Ph.D. in Engineering, Kyushu University

Master of Engineering, Kyushu University

CFD（Computational Fluid Dynamics）

Snow Power Generation

Boiling and Condensation Heat Transfer

Aerospace Engineering, Automotive Engineering, Air Conditioning Engineering

Cascading energy use

Utilization of Waste Heat

Carbon neutral, decarbonization

Effective use of natural energy

Deep Learning

Absorption

Adsorption

Porous Material

Heat Transfer Enhancement

Jet Flow

Heat Exchanger

Multiphase Flow

Phase-Change Heat Transfer

Two-Phase Flow

Energy, Earth resource engineering, energy science

Nanotechnology/Materials, Energy chemistry

Manufacturing technology (mechanical, electrical/electronic, chemical engineering), Fluid engineering

Manufacturing technology (mechanical, electrical/electronic, chemical engineering), Thermal engineering

Apr. 2023 - Present
Tokyo University of Agriculture and Technology, Visiting Associate Professor, Japan

Apr. 2023 - Present
Waseda University, 招聘研究員（兼任）

Oct. 2022 - Present
Sebelas Maret University, Visiting Professor

Apr. 2020 - Present
The University of Electro-Communications, Associate Professor

Apr. 2017 - Mar. 2023
Waseda University, Institute for environment & energy technology Project Research institutes, Adjunct Researcher

Nov. 2020 - Oct. 2022
Sebelas Maret University, AdjunctProfessor

Oct. 2021
Sebelas Maret University, AdjunctProfessor

01 Apr. 2015 - 31 Mar. 2020
The University of Electro-Communications, Assistant Professor (Tenure Track)

Oct. 2019
Sebelas Maret University, Faculty of Engineering, Visiting Lecture

Jul. 2015 - Mar. 2017
Waseda University, Research Institute for Science and Engineering, Adjunct Researcher

Jul. 2013 - Mar. 2015
Tokyo University of Agriculture and Technology, Assistant Professor

Apr. 2013 - Jun. 2013
Japan Society for the Promotion of Science (JSPS), Research Fellowship for Young Scientists (PD)

Apr. 2012 - Mar. 2013
Japan Society for the Promotion of Science (JSPS), Research Fellowship for Young Scientists (DC2)

Apr. 2010 - Mar. 2013
Kyushu University, Faculty of Engineering, Mechanical Engineering

Apr. 2008 - Mar. 2010
Kyushu University, Faculty of Engineering, Mechanical Engineering

Apr. 2005 - Mar. 2008
Kagoshima University, Faculty of Engineering, Mechanical Engineering

Apr. 2024 - Present
Committee member, The Fourth Technical Committee of the Environmental Engineering Division of the Japan Society of Mechanical Engineers (JSME), Society

Nov. 2023 - Present
The Chairperson, The Thermoinformatics Research Committee of the Environmental Engineering Division of the Japan Society of Mechanical Engineers (JSME), Society

Apr. 2023 - Present
Adjunct Resercher, Sustainable Energy & Environmental Society Open Innovation Research Organization

Apr. 2015 - Present
幹事, 日本冷凍空調学会 冷凍空調技術委員会 「カーボンニュートラルに向けた先進熱交換技術に関する調査研究」プロジェクト, Society

Mar. 2023 - Feb. 2024
Member of the Tokyo Block Chamber of Commerce,, Japan Society of Mechanical Engineers, Society

Mar. 2023 - Feb. 2024
動力エネルギーシステム部門企画委員会, 日本機械学会, Society

01 Apr. 2021 - 31 Mar. 2023
委員, NEDO調査事業 次世代冷媒に関する調査委員会, Government

2021
委員, 日本冷凍空調学会 デシカント・吸着・吸収・化学系技術委員会, Society

May 2017 - May 2020
Article reviewer, Japan Society of Refrigerating and Air Conditioning Engieers, Society

May 2017 - May 2020
論文査読 委員, 日本冷凍空調学会, Society

2019 - 2020
出版ＷＧ 主査, デシカント・吸着・吸収・化学系委員会, Society

2019 - 2020
出版ＷＧ 主査, デシカント・吸着・吸収・化学系委員会, Society

Jan. 2020
幹事, 日本機械学会 サーモインフォマティクス研究会

2016 - 2018
吸着分科会 委員, デシカント・吸着・吸収・化学系技術委員会, Society

Oct. 2014 - Sep. 2017
環境工学部門研究会 幹事, 日本機械学会

2015 - 2016
炭化水素冷媒のドロップインによる省エネルギー性能影響に関する調査 委員, 特定非営利活動法人 環境エネルギーネットワーク２１, Others

2015
日本冷凍空調学会調査研究プロジェクト 幹事, 日本冷凍空調学会調査研究プロジェクト

2015
幹事, 日本冷凍空調学会 「地球温暖化に対応するための先進熱交換技術に関する調査研究」調査研究プロジェクト, Society

2014
若手技術者交流会企画委員会 委員, 日本冷凍空調学会, Society

Jul. 2023
Times of research and the World Research Council
Thermal Engineering
Outstanding Resercher Award, Koji Enoki

May 2023
Japan Society of Refrigerating and Air Conditioning Engineers
Academic Award, ジャンネッティ ニコロ;ガルシア ジョン・カルロ;ヴァレラ リチャード;ジェイソン;清 雄一;榎木 光治;鄭 宗秀;齋藤 潔

Aug. 2017
Incentive award, The Japanese Society for Multiphase Flow
Japan society

Aug. 2017
ELSEVIER (Applied Thermal Engineering)
ELSEVIER (Applied Thermal Engineering) Outstanding Contribution in Reviewing Award
Official journal

May 2017
ELSEVIER (Int. J. of Heat and Mass Transfer)
ELSEVIER (Int. J. of Heat and Mass Transfer) Outstanding Contribution in Reviewing Award
Official journal

May 2016
Japan Society of Refrigerating and AirConditioning Engineers (JSRAE)
Incentive award, Japan Society of Refrigerating and AirConditioning Engineers
Official journal

May 2014
Japan Society of Refrigerating and AirConditioning Engineers (JSRAE)
Science Award, Japan Society of Refrigerating and AirConditioning Engineers, 榎木 光治
Official journal

May 2013
Japan Society of Refrigerating and AirConditioning Engineers (JSRAE)
Presentation Award, Japan Society of Refrigerating and AirConditioning Engineers, 榎木 光治

Dec. 2010
International Symposium on Innovative Materials for Processes in Energy Systems
Best Poster Award, International Symposium on Innovative Materials for Processes in Energy Systems 2010, Koji Enoki
Japan society

Mar. 2010
Japan Student Services Organization
Japan Student Services Organization (JASSO), Repayment Exemption for Students with Excellent Grades (Exemption of all of the loan)

2007
Kagoshima University
学部長・学科長表彰（GPAが3.5以上・3.25以上）
Others

Internal flow of TiO2–CNT/water nanofluids in a twisted tape insert tube
Sukmo Utomo Abdillah Amin; Budi Kristiawan; Koji Enoki; Wibawa Endra Juwana; Agung Tri Wijayanta
International Journal of Ambient Energy, 45, 1, 2024, Hybrid nanofluids show promise for enhancing thermal performance although there are still challenges and considerations associated with their implementation. This study investigated the effect of adding nanohybrid particles to the base fluid to enhance thermal performance in a concentric tube heat exchanger device. In this study, the heat transport and thermohydraulic behaviour of titanium dioxide–carbon nanotube/water nanofluids in a heat exchanger with and without twisted tape insert were investigated numerically. The works were carried out in the Reynolds number range from 5000 to 10,000 in which the nanoparticle loadings from 0.1% to 0.2%, and a twist ratio of 7 were used. Nusselt number of the observed hybrid nanofluids enhances with increasing Reynolds number although there is an increase in friction factor. It is clearly found that the twisted insert tube of heat exchanger resulted in thermal enhancement compared with the ordinary heat exchanger, and the addition of titanium dioxide–carbon nanotube hybrid nanofluids can enhance Nusselt number. This thermal enhancement contributes to energy savings, which also achieves environmental remediation.
Scientific journal

Thermal performance of Al2O3-TiO2/water hybrid nanofluids for cooling system using a helically coiled tube in a brushless direct current motor
Budi Kristiawan; Muhammad Alwan Hibatullah; Budi Santoso; Musabbikhah; Koji Enoki; Agung Tri Wijayanta
Numerical Heat Transfer; Part A: Applications, 2024, Thermal performance of Al2O3-TiO2/water hybrid nanofluids for cooling system using a helically coiled tube in a brushless direct current motor has been investigated numerically. The numbers of helical coils number were varied by 4, 6, 8, and 10 in coils and represented by Helical numbers 362, 355, 352, and 350, respectively. To solve the velocity and pressure discretization, the SIMPLE (Semi Implicit Method for Pressure Linked Equations) method was applied whereas to solve the energy and momentum equations, second order upwind was used. The result revealed that Nusselt number of Al2O3-TiO2/water hybrid nanofluids is greater than water, with an increased Nusselt number of 3.7% and 10.42% for 1 vol.% and 2 vol.%, respectively. The added nanoparticles concentration of Al2O3-TiO2/water hybrid nanofluids could not reduce significantly the stator temperature. Al2O3-TiO2/water hybrid nanofluids can reduce the stator temperature by 0.92% and 1.82% for 1 vol.% and vol.2%, respectively compared to water. However, the increased Reynolds number can reduce the stator temperature for all the observed working fluids. Helical number can affect the Nusselt number due to the influence of the helical geometry on the fluid’s flow behavior, heat transfer properties, and turbulence levels. Nusselt number of Al2O3-TiO2/water hybrid nanofluids at 1 vol.% has a higher value than water in each variation with an average increase in Nusselt number of 4.12% for all helical numbers.
Scientific journal

Enhancing Heat Transfer Performance: Nanofluids Application in Helical Microfin Tube Concentric Heat Exchangers
Hilbran Tama Dida Efendi; Budi Kristiawan; Koji Enoki; Agung Tri Wijayanta; Syamsul Hadi
Corresponding, E3S Web of Conferences, 465, 96, 18 Dec. 2023, Peer-reviwed, with international co-author(s), This manuscript explores the application of nanofluids in helical microfin tube concentric heat exchangers and investigates the potential for improved heat transfer performance. Helical microfin tubes offer enhanced heat transfer characteristics due to increased surface area and improved fluid mixing. When combined with nanofluids, which are base fluids with suspended nanoparticles, the thermal conductivity and convective heat transfer properties can be further enhanced. The objective of this present work is to investigate experimentally on heat transfer enhancement Al2O3/distilled water (0.05 vol.%) flowing through a helical microfin concentric heat exchanger in both parallel and counter flow in the vertical direction. The result is revealed that Al2O3/water nanofluids has enhanced thermal evaluation performance to water as base fluid. Counter flow might exhibit a more balanced performance, with a moderate enhancement in heat transfer while considering the pressure drop compared to parallel flow.
International conference proceedings, English

Comparative investigation on potential application of hybrid nanofluids for Brushless Direct Current (BLDC) motor cooling system
Yokanan Gustino Djentoe; Budi Kristiawan; Koji Enoki; Agung Tri Wijayanta; Budi Santoso
Corresponding, E3S Web of Conferences, 465, 42, 18 Dec. 2023, Peer-reviwed, with international co-author(s), In this study, the potential usage of hybrid nanofluids for brushless direct current (BLDC) motor cooling was compared. Due to their efficiency, durability, and small size, brushless direct current (BLDC) motors are a type of electric motor that are frequently employed in electric vehicles (EVs). In order to maintain appropriate operating temperatures and ensure long-term durability, cooling systems must be taken into account throughout the design of brushless direct current (BLDC) motors. Because excessive heat can shorten a motor's lifespan and affect its performance, effective cooling is crucial. Systems for cooling liquids need more parts and upkeep than those for cooling air. taken into account to get the maximum cooling effectiveness. The effectiveness and dependability of the liquid cooling system are greatly influenced by the system's correct design and implementation, including hose routing, sealing, and coolant choices. There are several approaches to improve a BLDC motor's hybrid nanofluid/nanofluid cooling system. In order to achieve the highest cooling efficiency, fluid flow velocity, nanoparticle concentration, and cooling system design should all be carefully taken into account.
International conference proceedings, English

Circuitry optimization using genetic programming for the advancement of next generation refrigerants
N. Giannetti; J. C.S. Garcia; C. Kim; Y. Sei; K. Enoki; K. Saito
International Journal of Heat and Mass Transfer, 217, 124648, 15 Dec. 2023, Peer-reviwed, In this study, a new evolutionary method, which can handle the implementation of genetic operators with unrestrained number and locations of splitting and merging nodes for the optimization of heat exchanger circuitries, is developed. Accordingly, this technique expands the search space of previous optimization studies. To this end, a finned-tube heat exchanger simulator is structured around a bijective mathematical representation of a refrigerant circuitry (the tube–tube adjacency matrix), which is used in combination with traversing algorithms from graph theory to recognize infeasible circuitries and constrain the evolutionary search to coherent and feasible offspring. The performance of three refrigerants, namely R32, R410A, and R454C, commonly used in air-conditioning applications was assessed for the optimized circuitries of a 36-tube evaporator while converging to a given cooling capacity, degree of superheating, and heat source boundary conditions. At a given output capacity and air outlet temperature, larger coefficient-of-performance improvements (up to 9.99% with reference to a common serpentine configuration) were realized for zeotropic refrigerant mixtures, such as R454C, where appropriate matching of the temperature glide with the temperature variation of the air yielded the possibility of further reducing the required compression ratio under the corresponding operating conditions. Hence, it was demonstrated that low-GWP zeotropic mixtures with temperature glide can realize a performance comparable to that of R32 and higher than that of R410A by approaching the Lorenz cycle operation.
Scientific journal, English

The Utilization of TiO2 Nanofluid for Cooling System of BLDC Motor
Farrel Yoga Widiasto; Budi Kristiawan; Koji Enoki; Agung Tri Wijayanta; Budi Santoso
The 5th ASEAN UEC Workshop 2023, Sep. 2023, Peer-reviwed, Invited, with international co-author(s)
International conference proceedings, English

The isothermal examination for enhancing the thermal conductivity of the TiO2/EG-40 nanofluid
Sukarman; Khoirudin; Amri Abdulah; Muhamad Taufik Ulhakim; Budi Krisitiawan; Agung Tri Wijayanta; Koji Enoki
Last, The 5th ASEAN UEC Workshop 2023, Sep. 2023, Peer-reviwed, Invited, with international co-author(s)
International conference proceedings, English

The Influence of Nanofluids on Thermal and Electrical Properties in Mineral Oil
Khoirudin; Sukarman; Amri Abdulah; Budi Kristiawan; Agung Tri Wijayanta; Koji Enoki
Last, The 5th ASEAN UEC Workshop 2023, Sep. 2023, Peer-reviwed, Invited, with international co-author(s)
International conference proceedings, English

Enhancement of Thermal Performance Using Nano-Fluid and Device Requirement for Liquid Cooling Systems in Battery Electric Vehicle
Amri Abdulah; Budi Kristiawan; Koji Enoki; Agung Tri Wijayanta; Sukarman; Khoirudin
The 5th ASEAN UEC Workshop 2023, Sep. 2023, Peer-reviwed, Invited, with international co-author(s)
International conference proceedings, English

Comparative Investigation on Thermal Assessment of Hybrid Nanofluids for Cooling System Application: BLDC Motor Case
Yokanan Gustino Djentoe; Budi Kristiawan; Koji Enoki; Agung Tri; Budi Santoso
Corresponding, The 5th ASEAN UEC Workshop 2023, Sep. 2023, Peer-reviwed, Invited, with international co-author(s)
International conference proceedings, English

Numerical Analysis On Performance Enhancement Of Electric Motor Cooling System Using Al2O3-TiO2/Water Hybrid Nanofluids
Muhammad Alwan Hibatullah; Budi Kristiawan; Koji Enoki; Agung Tri Wijayanta
Corresponding, The 5th ASEAN UEC Workshop 2023, Sep. 2023, Peer-reviwed, Invited, with international co-author(s)
International conference proceedings, English

Experimental Study on Enhancing Thermal Performance of Al2O3/Distilled Water Nanofluid in a Vertical Helical Microfin Tube
Hilbran Tama; Dida Effendi; Budi Kristiawan; Koji Enoki; Agung Tri Wijayanta; Syamsul Hadi
Corresponding, The 5th ASEAN UEC Workshop 2023, Sep. 2023, Peer-reviwed, Invited, with international co-author(s)
International conference proceedings, English

Thermal Conductivity and Viscosity of TiO2/water Nanofluid
Ahmad Imam Rifa’i; Budi Kristiawan; Koji Enoki; Agung Tri Wijayanta
Corresponding, The 5th ASEAN UEC Workshop 2023, Sep. 2023, Peer-reviwed, Invited, with international co-author(s)
International conference proceedings, English

Evolutionary optimization of heat exchanger circuitries for the advancement of next-generation refrigerants
N. Giannetti; A. Milazzo; J.C. Garcia; R.J. Varela; Y. Sei; K. Enoki; K. Saito
Proceedings of the 26th International Congress of Refrigeration, Aug. 2023, Peer-reviwed, True, with international co-author(s)
International conference proceedings, English

Solar Air Heater Thermal Performance Enhancement using V-Up Continuous Ribs
Indri Yaningsih; Panji Maulana Ibrahim; Dominicus Danardono Dwi; Prija Tjahjana; Aditya Rio Prabowo; Catur Harsito; Koji Enoki; Wibawa Endra Juwana; Sukmaji Indro Cahyono
Proceedings of ICIMECE 2023, 86, Aug. 2023, Peer-reviwed, with international co-author(s)
International conference proceedings, English

膨張弁狭隘流路の流量評価法
Akihiko MINATO; Seiichi YAMAGUCHI; Koji ENOKI; Kiyoshi SAITO
JAPANESE JOURNAL OF MULTIPHASE FLOW, The Japanese Society for Multiphase Flow, 19 May 2023, Peer-reviwed
Scientific journal

Numerical study on the Effect of Rectangular and Triangular Counter-Rotating Vortex Generators on the H-Rotor Wind Turbine Performance
Indri Yaningsih; Dominicus Danardono Dwi Prija Tjahjana; Eko Prasetya Budiana; Mohamad Muqoffa; Zainal Arifin; Suyitno; Koji Enoki; Takahiko Miyazaki
Evergreen, Kyushu University, 10, 1, 230-241, Mar. 2023, Peer-reviwed, Vortex generators (VGs) in the form of small fins are attached to the blade of the H-rotor wind turbine to improve the performance. Many studies provide the utilization VGs both experimentally and numerically. However, the investigation of the full scale of counter-rotating VGs in rotor blades is still rarely found. In the current study, two shapes of VGs were investigated to evaluate wind turbine performance. VGs in rectangular and triangular shapes were attached under the identical blade geometry of 375 mm of chord length and the blade attachment of 30% from the chord length. VGs have a similar height and length of 6.5 mm and 13 mm, respectively. The turbine was constructed with three blades that rotate under 1,650 mm of the rotor diameter and 1,000 mm of rotor height. The chordwise position (x/c) of the VGs was at 10%, 15%, 20%, and 25%. The computational fluid dynamics with the unsteady Reynolds Average Navier Stokes (URANS) model were employed. We found that VGs behave in different performances. The rectangular VGs had the maximum power coefficient (Cp) value at the x/c of 20%, while the triangular VGs had the maximum Cp value at the x/c of 25%. However, both VGs show the maximum Cp in the value of 0.467 with a 1.5 Tip Speed Ratio. To evaluate the performance improvement, the blade with VGs was compared with the blade without VGs. It was found that using the VGs improved the performance of the wind turbine by around 45.68% and 47.24%, respectively, for triangular and rectangular shapes. The flow field characteristics in terms of turbulent kinetic energy and flow velocity were also presented in this study to gain a better understanding of how the VGs work. The result revealed that the presence of the VGs significantly improves the performance of the turbine.
Scientific journal

Performance Improvement of H-Darrieus Wind Turbine with High Efficiency Vortex Structure Attachment
Bayu Anggara; Eko Prasetya Budiana; Catur Harsito; Koji Enoki; Kim Ki-Seong; Indri Yaningsih; Dominicus Danardono Dwi Prija Tjahjana
Evergreen, Kyushu University, 10, 1, 496-503, Mar. 2023, Peer-reviwed, Invited, with international co-author(s), The H-Darrieus wind turbine could be applied as an alternative electricity generation source. However, their performance is still low, affecting less attention to being used as electricity generation sources. Considering the current condition, the present study provides a numerical simulation of a potential performance enhancement of the H-Darrieus wind turbine by adding a high-efficiency vortex (HEV). HEV owns the ability to control the flow around the blade. HEV causes turbulent flow around the turbine while increasing turbulent kinetic energy. Three different HEV structures in rectangular, trapezoidal, and triangular shapes were attached to the blade to investigate the wind turbine performance. Two-tab angles (β) of 30° and 45° were applied to each structure to investigate the best position of HEV. The blade without HEV was considered as the baseline for the performance evaluation. It is revealed that triangular HEV performed the best with β of 30°, improving the power coefficient by 34% compared to the baseline when the tip speed ratio (TSR) is more than 1.5.
Scientific journal

Heat transfer deterioration by the copper oxide layer on horizontalsubcooled flow boiling
Edgar Santiago Galicia, Tomihiro Kinjo, Ouch Som Onn, ToshihikoSaiwai, Kenji Takita, Kenji Orito, Koji Enoki
Applied Mechanics, MDPI, 4, 1, 20-30, 04 Jan. 2023, Peer-reviwed, True, Water–copper is one of the most common combinations of working fluid and heating surface in high-performance cooling systems. Copper is usually selected for its high thermal conductivity and water for its high heat transfer coefficient, especially in the two-phase regime. However, copper tends to suffer oxidation in the presence of water and thus the heat flux performance is affected. In this research, an experimental investigation was conducted using a cooper bare surface as a heating surface under a constant mass flux of 600 kg·m (Formula presented.) ·s (Formula presented.) of deionized water at a subcooled inlet temperature (Formula presented.) of 70 K under atmospheric pressure conditions on a closed-loop. To confirm the heat transfer deterioration, the experiment was repeated thirteen times. On the flow boiling region after thirteen experiments, the results show an increase in the wall superheat (Formula presented.) of approximately 26% and a reduction in the heat flux of approximately 200 kW·m (Formula presented.). On the other hand, the effect of oxidation on the single phase is almost marginal.
Scientific journal, English

Impact of nanoparticles loading to a novel hybrid TiO2-CNTs/water nanofluid on thermal performance enhancement
Kartika Irene; Budi Kristiawan; Koji Enoki; Agung Tri Wijayanta
Numerical Heat Transfer; Part A: Applications, In press, Sep. 2023, Peer-reviwed, This present work investigated the thermal characteristics and hydrodynamics behavior of TiO2-CNTs/water hybrid nanofluids for laminar and turbulent conditions. Assuming hybrid nanofluids as Newtonian fluids, simulation-based evaluation was conducted using a single-phase approach. Various nanoparticles loading and Reynolds number were employed to characterize the observed hybrid nanofluids’ convective heat transfer coefficient and friction factor. The ratio between heat transfer performance and pressure drop enhancement was analyzed to understand thermal performance. Constant heat flux of 6500 W/m2 and low nanoparticle concentration from 0.10 to 0.20 vol.% were applied in this simulation. The results revealed that adding CNTs nanoparticles did not significantly affect friction factor enhancement at very low concentrations due to their good tribological properties. For the thermohydraulic characteristics, the observed hybrid nanofluids were better than those of water. The thermal performance factor magnitudes of hybrid nanofluids were above 1.0 even though they did not have significant magnitudes at very low concentrations, 1.01 and 1.07 for laminar and turbulent flow, respectively.
Scientific journal, English

NUMERICAL INVESTIGATION ON HEAT TRANSFER COEFFICIENT OF TiO2–CNTs/WATER NANOFLUID
Budi Kristiawan, Koji Enoki, Agung Tri Wijayanta, Sukmo Utomo Abdillah Amin
The 4th ASEAN UEC Workshop 2022, -, 03 Dec. 2022, Peer-reviwed, True
International conference proceedings, English

Special Issue on Sciences and Innovations in Heat Pump/Refrigeration:Volume II
Takahiko Miyazaki; Koji Enoki; Joon Ahn
Applied Sciences, MDPI, applsci-2004686, 20, 18 Oct. 2022, Peer-reviwed, Invited
Scientific journal, English

遺伝的冷媒流路生成アルゴリズムを用いた熱交換器の最適化に関する研究
ジャンネッティ ニコロ; ガルシア ジョン カルロ; ヴァレラ リチャード; ジェイソン; 清 雄一; 榎木 光治; 鄭 宗秀; 齋藤 潔
日本冷凍空調学会論文集, 日本冷凍空調学会, 39, 3, 223-239, 30 Sep. 2022, Peer-reviwed
Scientific journal, Japanese

Simulation-based assessment of the thermal-hydraulic performance of titania-based nanofluids in a circular-mini-channel tube
Budi Kristiawan; Koji Enoki; Wibawa Endra Juwana; Rendy Adhi Rachmanto; Agung Tri Wijayanta; Takahiko Miyazaki
International Journal of Ambient Energy, Informa UK Limited, 43, 1, 8022-8035, 23 Jun. 2022, Peer-reviwed, with international co-author(s), Simulation-based assessment is performed here by using the single-phase model (S-PM) and the two-phase mixture model (T-PMM). The models are used to investigate the heat transfer performance of TiO2/water nanofluids inside a circular tube with a diameter of 1.09 mm and a length of 306 mm. Reynolds numbers are varied from 600 to 2100, while the nano-particle concentration is 1.0, 2.0, 3.5 and 5.0 vol.%. Higher friction factor (f) and convective heat transfer coefficient (h) were observed for titania-based nanofluids compared to those of the base fluid (water). Heat transfer performance of the nanofluid increases as the nanoparticle concentration is increased. Likewise, the augmentation in pressure drop increases with nano-particle concentration. The highest enhancement in the Nusselt number of 14.81% was observed for nanoparticles with a concentration of 5 vol.% at the Reynolds number of about 1500.
Scientific journal

Prediction of Boiling Heat Transfer Coefficients for Mini-Channels
Yuichi Sei; Koji Enoki; Seiichi Yamaguchi; Kiyoshi Saito
Multiphase Science and Technology, Begell House, 34, 2, 43-65, Feb. 2022, Peer-reviwed, Invited, Artificial intelligence (AI) techniques have been widely used across many fields. However, few studies have focused on the use of AI techniques for predicting heat transfer coefficients regardless of single-phase or two-phase flows. The applicability of deep neural networks [ (DNNs), also known as deep learning], one of the most promising AI techniques, to horizontal-flow boiling heat transfer in mini-channels is being actively researched. The effect of surface tension in mini-channels is significant in comparison to that in conventional large tubes, and the heat transfer mechanism in the mini-channels is complicated. Thus, the accuracy of the prediction results based on existing studies is not satisfactory. Moreover, we cannot determine the uncertainty of the predicted heat transfer coefficients by using existing approaches. In this study, we propose a novel prediction mechanism, based on the combination of a DNN and Gaussian process regression, that can predict not only heat transfer coefficients with high accuracy but also the uncertainties of the predicted heat transfer coefficients. We refer to this new research field, which integrates thermal engineering and informatics, as thermoinformatics, and consider the scope of its future development.
Scientific journal, English

Development of Assessment Techniques for Next-Generation Refrigerants with Low GWP Values Fourth report: Efforts and outcomes on heat exchanger optimization in FY 2020
N. Giannetti; J.C. Garcia; R.J. Varela; Y. Sei; K. Enoki; J. Jeong; K. Saito
JSRAE Annual Conference 2021, Sep. 2021, with international co-author(s)
Symposium, English

Experimental investigation into the heat transfer and pressure drop performance of sintered high porosity media
Ren Watanabe; Takuto Kobayashi; Yusuke Otomo; Atsushi Akisawa; Yuki Ueda; Koji Enoki
Applied Thermal Engineering, Elsevier, 196, 117284, Sep. 2021, Peer-reviwed, Corresponding Author
Scientific journal, English

Subcooled flow boiling heat flux enhancement using high porosity sintered fiber
Edgar Santiago Galicia; Yusuke Otomo; Toshihiko Saiwai; Kenji; Takita; Kenji Orito; Koji Enoki
Applied Sciences, MDPI, 11, 13, 5883, Jun. 2021, Peer-reviwed, Passive methods to increase the heat flux on the subcooled flow boiling are extremely needed on modern cooling systems. Many methods, including treated surfaces and extended surfaces, have been investigated. Experimental research to enhance the subcooled flow boiling using high sintered fiber attached to the surface was conducted. One bare surface (0 mm) and four porous thickness (0.2, 0.5, 1.0, 2.0 mm) were compared under three different mass fluxes (200, 400, and 600 kg center dot m(-2)center dot s(-1)) and three different inlet subcooling temperature (70, 50, 30). Deionized water under atmospheric pressure was used as the working fluid. The results confirmed that the porous body can enhance the heat flux and reduce the wall superheat temperature. However, higher porous thickness presented a reduction in the heat flux in comparison with the bare surface. Bubble formation and pattern flow were recorded using a high-speed camera. The bubble size and formation are generally smaller at higher inlet subcooling temperatures. The enhancement in the heat flux and the reduction on the wall superheat is attributed to the increment on the nucleation sites, the increment on the heating surface area, water supply ability through the porous body, and the vapor trap ability.
Scientific journal, English

Pressure Drop of a Refrigerant Flowing Vertically Upward and Downward in Small Circular, Rectangular and Triangular Tubes
Koji Enoki
Applied Sciences, MDPI, 11, 11, 5195, Jun. 2021, Peer-reviwed, Invited, In the present study, experiments were performed to examine the characteristics of the two-phase frictional pressure drop of an R410A refrigerant flowing vertically upward and downward for the development of a high-performance heat exchanger using small tubes or mini-channels for air-conditioning systems. The cross-sections of copper test tubes were 0.5, 0.7, 1.0, 1.5, and 2.0 mm circular tubes, and rectangular and triangular tubes with hydraulic diameters of 1.04 and 0.88 mm, respectively. The frictional pressure drops were measured in the range of mass fluxes of 30-400 kg center dot m(-2)center dot s(-1), with qualities from 0.05 to 0.9 and a saturation temperature of 10 degrees C. The characteristics of the measured pressure drops were compared in different inner diameters, cross-section shapes, and flow directions. In addition, Chisholm's parameter and various modified Chisholm's parameters for small tubes were examined to determine whether or not they reproduced our measurement data.
Scientific journal, English

Pressure Drop of a Refrigerant Flowing Vertically Upward and Downward in Small Circular, Rectangular, and Triangular Tubes
Koji Enoki
Applied Sciences, MDPI, 11, 11, 5195, Jun. 2021, Peer-reviwed, Invited
Scientific journal, English

波状形状を有する微細管内における垂直上昇気液二相流の沸騰熱流動特性に関する研究
Tetsuya KOBAYASHI; Haruki MITARAI; Koji ENOKI; Kosaku NISHIDA; Ikuro AKADA
Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers, The Japan Society of Refrigerating and Air Conditioning Engineers, 38, 2, 123, May 2021, Peer-reviwed, In order to clarify the effects of different the shape on the boiling thermal-hydraulics characteristics of mini-channels, the observation of flow patterns and measuring pressure drop and boiling heat transfer coefficient in vertically upward flow with a wavy mini-channel have been conducted. The straight mini-channel was also tested with the same hydraulic diameter of 1 mm inside diameter for a comprehensive comparison. Flow patterns in the wavy mini-channel were observed some differences from general flow patterns reported by previous studies of straight mini-channels. The frictional pressure drop of the wavy mini-channel was about two times higher than that of the straight mini-channel. From the results of boiling heat transfer experiments, it was found that the heat transfer coefficient of the wavy mini-channel was different from that of the straight mini-channel at low heat fluxes and increased by a factor of up to 2.5, and that the heat transfer coefficient of the wavy mini channel approached that of the straight mini-channel at high heat fluxes.
Scientific journal, Japanese

透過率と管摩擦係数を用いた焼結型繊維状多孔質管に関する圧力損失特性の整理
Takuto KOBAYASHI; Ren Watanabe; Yusuke OTOMO; Yuki UEDA; Atsushi AKISAWA; Koji ENOKI
Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers, The Japan Society of Refrigerating and Air Conditioning Engineers, 38, 2, 155, May 2021, Peer-reviwed, The characteristics of the frictional pressure drop on the in-pipe flow filled with a sintered fibrous porous body were investigated by experimental study. In this study, the pipe friction coefficient, and Reynolds number were derived by using the shape coefficient and permeability for the sintered fibrous porous body. The porosity, inner diameter, average fiber diameter, and porous body filling length were parameters. The calculation method of the frictional pressure drop was proposed on this study, considers the flow velocity in the pipe that changes depending on the porosity, and the frictional pressure drop can be calculated within a range error of 12.3% at the maximum, and an average of 5.1%.
Scientific journal, Japanese

Effect of Shape Change in the Flow Dirction of Mini-channel on the Flow Patterns
Haruki Mitarai; Tetsuya Kobayashi; Koji Enoki; Kousaku Nishida; Ikurou Akada
The 13th International Energy Agency HEAT PUMP CONFERENCE, 344, 9B, Apr. 2021, Peer-reviwed
International conference proceedings, English

Experimental Investigation of Local Nucleate Boiling Heat Transfer and Mixing Ratio on Copper Surface about Mixture R 32 / R 1234ze (E)
Riku Fukuju; Koji Enoki; Kiyoshi Saito
The 13th International Energy Agency HEAT PUMP CONFERENCE, 345, 6A, Apr. 2021, Peer-reviwed
International conference proceedings, English

Correlation of Pressure Drop in the Sintered Fibrous Porous Tube with Permeability and Friction Coefficient
Koji Enoki; Takuto Kobayashi; Ren Watanabe; Yusuke Otomo; Atsushi Akisawa; Indri Yaningsih; Budi Kristiawan; Agung Tri Wijayanta
IOP Conference Series Materials Science and Engineering, Institute of Physics(IOP), 1096, Mar. 2021, Peer-reviwed, Invited
Scientific journal, English

The enhancement of subcooled flow boiling heat transfer with high porosity sintered fiber metal
Yusuke Otomo; Edgar Santiago Galicia; Koji Enoki
Applied Sciences, MDPI, 11, 3, 1-14, Jan. 2021, Peer-reviwed, Invited, We conducted experimental research using high-porosity sintered fiber attached on the surface, as a passive method to increase the heat flux for subcooled flow boiling. Two different porous thicknesses (1 and 0.5 mm) and one bare surface (0 mm) were compared under three different inlet subcooling temperatures (30, 50 and 70 K) and low mass flux (150-600 kg center dot m(-2)center dot s(-1)) using deionized water as the working fluid under atmospheric pressure. The test section was a rectangular channel, and the hydraulic diameter was 10 mm. The results showed that the heat flux on porous surfaces with a thickness of 1 and 0.5 mm increased by 60% and 40%, respectively, compared to bare surfaces at Delta Tsat = 40 K at a subcooled temperature of 50 K and mass flux of 300 kg center dot m(-2)center dot s(-1). An abrupt increase in the wall superheat was avoided, and critical heat flux (CHF) was not reached on the porous surfaces. The flow pattern and bubble were recorded with a high-speed camera, and the bubble dynamics are discussed.
Scientific journal, English

Effect of heat and mass transfer characteristics on the performance of the adsorption dehumidification system
Indri Yaningsih; Koji Enoki; Takahiko Miyazaki
14th IIR Gustav-Lorentzen Conference on Natural Fluids, Institute Institute of Refrigeration（IIR）, 1194, 310-315, Dec. 2020, Peer-reviwed, The current research deals with the study on the effect of heat and mass transfer characteristics on the adsorption dehumidification system performance. The Nusselt number (Nu) and Sherwood number (Sh) was evaluated under laminar regions, with the Reynolds number (Re) ranging from 440 to 722. Each investigation was conducted with the water vapor as a working fluid, which was flow under the maintained temperatures of 20 ºC and 55 ºC during the adsorption and desorption process, respectively. Numerical predictions were developed to predict the system characteristics by considering the Nu values obtained from the experimental data. Increasing Re leads to the improvement of Nu and Sh values; however, it negatively influences the system performance. It also suggested that the properties of the interface between desiccant layers and water vapor in the predictive approaches need to be carefully acquired.
International conference proceedings, English

Effect of the High Porosity Sintered Fiber on the Surface in Subcooled Boiling Heat Transfer Enhancement
Edgar; Santiago Galicia; Kosuke Kumatori; Yusuke Otomo; Koji Enoki
14th IIR Gustav-Lorentzen Conference on Natural Fluids, Institute Institute of Refrigeration（IIR）, 1193, 141-146, Dec. 2020, Peer-reviwed, Nowadays new passive methods to enhance the Critical Heat Flux (CHF) have been investigated for several researchers. Experiments using a novel and practical technique called High Porosity Sintered Fiber were conducted, attaching this material on the heating surface under forced convection subcooled conditions. The effects of the porous thickness on the heat flux and flow aspect were analyzed and recorded using a high speed camera. Three different of porous thickness (0.2,0.5, and 1 mm) and one bare surface (0mm) were tested. Experimental results show that using a porous surface can enhance the heat flux in almost 2 times better than the bare surface under de same wall superheat ∆Tsat K conditions. Besides that, at high thickness porosity, the CHF tends to reduce in comparison with the low thickness porosity. Bubble formation and pressure drop were also compared. The sintered fiber material is copper with a porosity of 86%.
International conference proceedings, English

Elucidation of pressure drop characteristics in sintered fibrous porous tubes using permeability and tube friction coefficient and construction of rearranging correlation
Takuto Kobayashi; Ren Watanabe; Yusuke Otomo; Koji Enoki
The 2nd ASEAN UEC WS on Energy and AI，UEC Seminar 2020, 6, Nov. 2020, Peer-reviwed
International conference proceedings, English

Effect of mass flux on high porosity sintered fiber on subcooled flow boiling
Edgar Santiago-Galicia; Yusuke Otomo; Koji Enoki
The 2nd ASEAN UEC WS on Energy and AI，UEC Seminar 2020, 9, Nov. 2020, Peer-reviwed
International conference proceedings, English

The enhancement of subcooled flow boiling heat transfer with high porosity sintered fibrous metal
Yusuke Otomo; Edgar Santiago Galicia; Toshihiko Saiwai; Kenji Takita; Toshihiro Zushi; Koji Enoki
The 2nd ASEAN UEC WS on Energy and AI，UEC Seminar 2020, 7, Nov. 2020, Peer-reviwed
International conference proceedings, English

Analysis on Significance of Nanofluids as the Working Fluid for Double Tube Heat Exchanger Applications
Ahmad Imam Rifa'I; Koji Enoki; Budi Kristiawan,Agung; Tri Wijayanta
The 2nd ASEAN UEC WS on Energy and AI，UEC Seminar 2020, 25, Nov. 2020, Peer-reviwed
International conference proceedings, English

The enhancement of subcooled flow boiling heat transfer with high porosity sintered fibrous metal
Yusuke Otomo; Edgar Santiago Galicia; Toshihiko Saiwai; Kenji Takita; Toshihiro Zushi; Koji Enoki
The 7th UEC Seminar in ASEAN, 2020, The 2nd ASEAN-UEC Workshop on Energy and AI, 2020, 9, Nov. 2020, Peer-reviwed
International conference proceedings, English

The progress in adsorption technologies for energy sustainability
Indri Yaningsih; Dominicus Danardono Dwi Prija Tjahjana; Eko Prasetya Budiana; Koji Enoki; Takahiko Miyazaki
The 7th UEC Seminar in ASEAN, 2020, The 2nd ASEAN-UEC Workshop on Energy and AI, 2020, Invited, 32, Nov. 2020, Peer-reviwed, Invited
International conference proceedings, English

Elucidation of pressure drop characteristics in sintered fibrous porous tubes using permeability and tube friction coefficient and construction of rearranging correlation
Takuto Kobayashi; Ren Watanabe; Yusuke Otomo; Koji Enoki
The 7th UEC Seminar in ASEAN, 2020, The 2nd ASEAN-UEC Workshop on Energy and AI, 2020, 6, Nov. 2020, Peer-reviwed
International conference proceedings, English

Correlation of Pressure Drop in the Sintered Fibrous Porous Tube with Permeability and Friction Coefficient
Koji Enoki; Takuto Kobayashi; Ren Watanabe; Yusuke Otomo; Atsushi Akisawa; Indri Yaningshi; Budi Kristiawan; Agung Tri Wijayanta
ICIMECE2020（International Conference on Industrial, Mechanical, Electrical and Chemical Engineering 2020）, Invited Speaker, 10 Oct. 2020, Peer-reviwed, Invited
International conference proceedings, English

ENHANCEMENT OF THERMAL-HYDRAULIC PERFORMANCE OF ARTIFICIALLY ROUGHENED SOLAR AIR HEATER DUCT WITH V-UP CONTINUOUS RIBS
Indri Yaningsih; Dominicus Danardono Dwi; Prija Tjahjana; Takahiko Miyazaki; Koji Enoki
Proceedings of ISTP31, ISTP31, ISTP31-85, Oct. 2020, Peer-reviwed
International conference proceedings, English

CRITICAL HEAT FLUX ENHANCEMENT USING A HIGH POROSITY SINTERED FIBER ATTACHED ON THE HEATED SURFACE
Edgar Santiago-Galicia; Yusuke Otomo; Indri Yaningsih; Koji Enoki
Proceedings of ISTP31, ISTP31, ISTP31-103, Oct. 2020, Peer-reviwed
International conference proceedings, English

Two-phase flow regimes of refrigerant R134a in an oscillating horizontal rectangular minichannel conduit
Koji Enoki; Masahiro Ono; Tomio Okawa; Atsushi Akisawa; Hideo Mori; Budi Kristiawan; Agung Tri Wijayanta
International Journal of Refrigeration, International Journal of Refrigeration, 118, 261-268, Oct. 2020, Peer-reviwed, In this study, refrigerant R134a experiments were carried out to observe two-phase flow in an oscillating horizontal rectangular minichannel conduit at refrigerant mass flux of approximately 30 kg•m −2•s −1 to 300 kg•m −2•s −1, saturation temperature of approximately 30 °C, and average vapor quality in the test section inlet of approximately 0.05 to 0.9. The test section was made from quartz and consists of a visible rectangular minichannel with a hydraulic diameter of 0.84 mm. The test section was oscillated vertically using a reciprocating motor. The effects of oscillation on slug and stratified flow patterns were investigated. The experimental observation was compared with an existing flow pattern map. The thin liquid film around the vapor of slug flow mostly moved up and down when the test section oscillated. As a result, a dry surface was not observed around the vapor due to the lower heat transfer coefficient. When the test section oscillated, the stratified flow changed to annular flow, and a dry surface was also not observed on the upper side of the minichannel conduit.
Scientific journal, English

Enhancing the thermal performance of TiO2/water nanofluids flowing in a helical microfin tube
Budi Kristiawan; Ahmad Imam Rifa'i; Koji Enoki; Agung Tri Wijayanta; Takahiko Miyazaki
Powder Technology, Elsevier, 376, 254-262, Oct. 2020, Peer-reviwed, A hybrid method with a microfin tube and TiO2/water nanofluid with various nanoparticles concentration has been investigated experimentally. The objectives of this work arc to characterize thermohydraulic including friction factor and thermal performance, and to develop correlation based on the experimental result. In general, adding nanopartides to the base fluid causes increased thermal performance. Pressure drop inside the microfin tube at TiO2/water concentrations of 0.05, 0.15, and 0.30 vol% were respectively 73%, 77%, and 80% higher than that in the smooth tube. Furthermore, the pressure drop increased with an increment in Re number. In this work, the developed correlation was proposed to predict practically Nu number. The present findings contribute to our understanding of how to enhance heat transfer using helical microfins inside tubes and nanofluids. (C) 2020 Elsevier B.V. All rights reserved.
Scientific journal, English

Water flow boiling heat transfer in vertical minichannel
Koji Enoki; Masahiro Ono; Tomio Okawa; Budi Kristiawan; Agung Tri Wijayanta
Experimental Thermal and Fluid Science, ELSEVIER SCIENCE INC, 117, C, 110147, Sep. 2020, Peer-reviwed, In recent years, microchannel water flow boiling has demonstrated excellent heat removal capabilities, particular for nuclear reactor safety utilities, ranging from mini-scale cooling devices to chemical industry plant purposes. Of particular interest is cooling technology using water as the primary refrigerant. This paper presents the results of an experimental investigation into the water boiling heat transfer in a minichannel conduit vertically oriented with the upward flow. The test section was a circular minichannel tube made of stainless steel with a 2.12 mm inner diameter. To observe the flow regime, the test section was equipped with sight tubes made of transparent perfluoroalkoxy alkane resin and Pyrex glass at the inlet and outlet, respectively. Water flow boiling experiments were conducted at a saturation temperature of approximately 100 °C, with the mass flux of water as the working fluid from 20 to 120 kg/m2·s, and the average vapor quality in the test section inlet of approximately 0.05 to 0.9. The predicted two-phase flow regimes at the test section were classified as three patterns, namely slug, annular, and churn flows, using a flow pattern map with the vapor quality as the abscissa versus the mass velocity as the ordinate. The flow patterns were confirmed and visualized by observations at the test section outlet sight tube. The characteristics of the heat transfer and fluid flow were analyzed. Moreover, the forced convective heat transfer coefficient and pressure drop in the test section were determined based on the experimental data. The highest mass flux yielded the highest convective heat transfer coefficient. Despite this significant heat transfer coefficient improvement, the pressure loss was higher than that for a higher mass flux, indicating that the pressure loss was more pronounced owing to the presence of the minichannel at a higher mass flux.
Scientific journal, English

Method for improving gas single-phase heat transfer using metal sintered porosity porous
Koji Enoki; Yusuke Otomo; Ren Watanabe; Takuto Kobayashi; Tomio Okawa; Yuki Ueda; Atsushi Akisawa
5th Thermal and Fluids Engineering Conference, 409-410, 22 May 2020, Peer-reviwed
International conference proceedings, English

Effects of surface tension and viscosity on liquid jet breakup
Yi Zhan; Yusuke Kuwata; Kiyotaka Maruyama; Tomio Okawa; Koji Enoki; Mitsuhiro Aoyagi; Takashi Takata
Experimental Thermal and Fluid Science, ELSEVIER SCIENCE INC, 112, 1, Apr. 2020, Peer-reviwed, The breakup process of liquid jet was explored through visualization using a high-speed camera to develop a prediction model for the impact frequency (the number of droplet passing per unit time). The experiments were conducted for the three jet regimes of Rayleigh, first wind-induced and second wind-induced. The five liquids (water, two ethanol aqueous solutions, and two glycerin aqueous solutions) were used as the test liquids to explore the effects of surface tension and viscosity. Since the droplets were produced due to jet breakup, the impact frequency was zero just downstream of the nozzle and increased asymptotically with an increase in the distance from the nozzle. Thus, auxiliary correlations were developed for the minimum breakup length where the jet breakup is initiated, the maximum breakup length where the jet breakup is completed, and the mean droplet size and the impact frequency in the equilibrium region downstream of the maximum breakup length. Since the correlations were dependent on the flow regime, the boundaries between the three jet regimes were also determined using the present observation results. It was demonstrated that the impact frequencies calculated by the proposed model agree with the experimental data accumulated in this work fairly well in the Rayleigh and second wind-induced regimes, while agreement was deteriorated to some extent in the transition (first wind-induced) regime. For the application to the prediction of splashing rate during coolant leakage in sodium-cooled fast reactors, a simple method to ensure conservative estimation of the impact frequency was also proposed.
Scientific journal, English

High Performance Cooling in Subcooled Boiling Heat Transfer Using High Porosity Sintered Fiber on the Surface
KUMATORI Kousuke; OTOMO Yusuke; SANTIAGO-GALICIA Edgar; OKAWA Tomio; ORITO Kenji; TAKITA Kenji; SAIWAI Toshihiko; ENOKI Koji
Japanese J. of Maltiphaes Flow, The Japanese Society for Multiphase Flow, 34, 1, 64-74, 2020, Peer-reviwed, Invited, Nowadays high performance cooling equipment are required for high heat dissipation electric devices. In this research, the experiments were carried out with high porosity sintered fiber on the surface under the forced convection subcooled boiling heat transfer. The experimental parameter of the porous is the filling height relative to the channel height, and the porosity of porous material was 86 %. According to the experiments, all of porous surfaces, almost 2 times higher performance on boiling heat transfer compared with the bare surface under the same wall superheat ⊿T_sat (K) conditions. However, the high height porous condition, the CHF tend to low compared with lower height porous condition and bare surface. In addition, the relations between the bubble behavior and the heat transfer were analyzed from experimental results and the videos acquired by high speed camera.
Scientific journal, Japanese

Toughness of Nanoparticle-Layer and Its Influence on Pool Boiling Heat Transfer in Nanofluids
Tomio Okawa; Yosuke Watanabe; Koji Enoki
Proceedings of 11th Korea-Japan Symposium on Nuclear Thermal-Hydraulics And Safety (NTHAS-11), NTHAS11, 21 Nov. 2019, Peer-reviwed
International conference proceedings, English

An experimental study of boiling heat transfer and pressure drop characteristics in wavy mini-channel
Tetsuya Kobayashi; Koji Enoki; Natsumi Tokashiki; Tomio Okawa; Kosaku Nishida; Masashi Kato; Ikuro Akada
ISTP30, ISTP, 044, 02 Nov. 2019, Peer-reviwed
International conference proceedings, English

Evaluation of the Performance of Nanofluid as Quenching Coolant
Yutaro Umehara; Tomio Okawa; Koji Enoki
TETSU TO HAGANE-JOURNAL OF THE IRON AND STEEL INSTITUTE OF JAPAN, IRON STEEL INST JAPAN KEIDANREN KAIKAN, 105, 11, 1050-1058, Nov. 2019, Nanofluid is a liquid in which nanometer-sized particles are dispersed in base liquid. It is known that the critical heat flux and the wall superheat at the minimum heat flux in pool boiling are improved in nanofluids. In this research, performance of silica-water nanofluid as quenching coolant is explored experimentally since the above-mentioned parameters play important roles in this application. First, we investigated the immersion cooling of high-temperature test piece in the nanofluid; here, the test piece was cylindrical in shape and made of Inconel 718 or SUS304. It was confirmed that the test piece is cooled faster in the nanofluid than in distilled water. It was also found that non-uniformity of temperature in the test piece during quenching is mitigated in the nanofluid. This indicates that the silica nanofluid is considered a promising coolant to avoid the occurrence of hardening crack during quenching. Finally, Vickers hardness test was done for the Inconel 718 test piece. It was shown that the hardness tends to increase with an increase in the cooling rate even under the high cooling rate of about 1000 K/min although the difference of hardness was not noticeable between the experiments using the distilled water and the silica nanofluid as the quenching coolant.
Scientific journal, Japanese

急冷処理用冷却材としてのナノ流体の有効性評価
Yutaro Umehara; Tomio Okawa; Koji Enoki
鉄と鋼, IRON STEEL INST JAPAN KEIDANREN KAIKAN, 105, 11, 1050-1058, Nov. 2019, Peer-reviwed, Nanofluid is a liquid in which nanometer-sized particles are dispersed in base liquid. It is known that the critical heat flux and the wall superheat at the minimum heat flux in pool boiling are improved in nanofluids. In this research, performance of silica-water nanofluid as quenching coolant is explored experimentally since the above-mentioned parameters play important roles in this application. First, we investigated the immersion cooling of high-temperature test piece in the nanofluid; here, the test piece was cylindrical in shape and made of Inconel 718 or SUS304. It was confirmed that the test piece is cooled faster in the nanofluid than in distilled water. It was also found that non-uniformity of temperature in the test piece during quenching is mitigated in the nanofluid. This indicates that the silica nanofluid is considered a promising coolant to avoid the occurrence of hardening crack during quenching. Finally, Vickers hardness test was done for the Inconel 718 test piece. It was shown that the hardness tends to increase with an increase in the cooling rate even under the high cooling rate of about 1000 K/min although the difference of hardness was not noticeable between the experiments using the distilled water and the silica nanofluid as the quenching coolant.
Scientific journal, Japanese

How to Enhancement Gas-side Heat Transfer
Koji Enoki
ICE-SEAM2019, Keynote Lectue, 16 Oct. 2019, Peer-reviwed, Invited
International conference proceedings, English

Characterization of two-phase flow distribution in microchannel heat exchanger header for air-conditioning system
Mark Anthony Redo; Jongsoo Jeong; Niccolo Giannetti; Koji Enoki; Seiichi Yamaguch; Kiyoshi Saito; Hyunyoung Kim
Experimental Thermal and Fluid Science, ELSEVIER SCIENCE INC, 106, 183-193, Sep. 2019, Peer-reviwed, The two-phase flow distribution behavior of R410A within the vertical header of a microchannel heat exchanger with multiple horizontally oriented microchannel flat tubes was investigated and is reported in this paper. Unlike most previous studies, which examined the distribution at lower flowrates applicable mostly to automobile applications, this work evaluated higher flowrates relevant to actual air conditioning evaporator applications with larger size headers. The following operating conditions, were utilized: an inlet mass flowrate that varied from 40 to 200 kg h(-1) (mass flux of 27-250 kg m(-2) s(-1) in the header), vapor qualities of 0.1, 0.2, and 0.6, and evaporating temperatures of 10 and 15 degrees C. The tube protrusion depth into the header was set at 0 and 50%. Flow distribution profiles derived from the experiment measurements and clear visualization images captured by a high speed camera showed that the distribution improves for increased inlet mass flux at low vapor quality, while a 5 degrees C difference in evaporating temperature does not yield a substantial distribution change. A 50% protrusion produces higher inertial forces pushing the liquid level towards the top section. A correlation was developed to predict the liquid distribution by relating the portion of liquid exiting the branch tube to the liquid at the immediate header as a function of the liquid Froude number.
Scientific journal, English

Temperature Distribution Measurement During Quenching of High-Temperature Wall with a Falling Liquid Film
Tomio Okawa; Keisuke Yamagata; Koji Enoki
18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), NURETH18-0000, 300-306, 19 Aug. 2019, Peer-reviwed, The spatial distribution of heat transfer coefficient (HTC) in the vicinity of the rewet front is most important information in determining the rewet velocity during cooling of high-temperature fuel rods with falling liquid film. Thus, many models are available for the HTC distribution in literature, but they have not been validated sufficiently mainly due to the lack of experimental data. In this study, transient of temperature distribution during rewetting of high-temperature vertical plate was measured using a high-speed infra-red camera. The measured temperature data were substituted to the heat conduction equation to derive the HTC distribution. It was confirmed that the rewet velocity measured in this work can be reproduced within the error of 10% if the calculated HTC distribution is used. This indicates that the experimental data obtained in this work can be used as the base data to develop a high-performance correlation for the HTC distribution near the rewet front.
International conference proceedings, English

Heat Transfer Enhancement of TiO2/Water Nanofluids Flowing Inside a Square Minichannel with Microfin Structure: A Numerical Investigation
Budi Kristiawan; Agung Tri Wijayanta; Koji Enoki; Takahiko; Miyazaki, Muhanmmad Aziz
Energies, MDPI, 12, 6, Aug. 2019, Peer-reviwed, インドネシアのスブラスマーレット大学と九州大学との共同研究成果である．
Scientific journal, English

Visualization and analysis of adsorption kinetics by using image processing algorithm
Indri Yaningsih; Koji Enoki; Agung Tri Wijayanta; Kyaw Thu; Takahiko Miyazaki
Trans. of the JSRAE, JSRAE, 19-07DC_OA, 3, 165, Aug. 2019, Peer-reviwed, This paper provides an analysis of the adsorption kinetics by using image processing algorithm. Rapid adsorption kinetics is increasingly important because it offers a good mass transfer hence improves the efficiency of the sorption system. For adsorption kinetics, it is required to determine the first stage of the measurement precisely. Therefore, selecting the proper method becomes essential. Simple experimental setup was developed for evaluating adsorption equilibrium and adsorption kinetics of Silica gel/water pair. The test apparatus comprises of adsorption cell, evaporator/condenser, piping line, and measurement devices for temperature and pressure. Silica gel types A was employed in the present study as the adsorbent material. A new method is proposed to calculate the adsorption kinetics by using the digital image analyzing. Algorithm for image analysis could semantically segment the adsorption process by creating images which represented the dataset for water level changes inside the evaporator.
Scientific journal, English

Effect of Nanoparticle Layer Coating on Heat Transfer Performance of Heat Pipe
T. Okawa; M. Wang; K. Enoki
Proceedings of 1st International Conference on Nanofluids (ICNf2019), ICNf-0000, Jun. 2019, Peer-reviwed
International conference proceedings, English

Convection Effect of the Freeze Valve Melting Process on Molten Salt Reactor
Indarta Kuncoro Aji; Tokushima Tatsuya; Motoyasu Kinoshita; Koji Enoki; Tomio Okawa
Proceedings of 27th International Conference on Nuclear Engineering (ICONE27), ICONE27-2450, May 2019, Peer-reviwed, Freeze valve is one of the major safety systems used in the Molten Salt Reactor (MSR), that automatically opens in case of accident. The freeze valve was first developed in the Oak Ridge National Laboratory (ORNL) to be utilized in the Molten Salt Reactor Experiment (MSRE). Currently, many organizations have developed different types of MSR. Thus, appropriate freeze valve designs are needed. Fundamental studies to understand the basic features of freeze valve are important to develop new designs. The purpose of this study is to analyze the effect of convection in the molten salt on the opening time of the freeze valve. Numerical simulations were conducted using the ANSYS Fluent 18.1 and the results were compared with the experimental data obtained under similar conditions. From the calculation results, it was found that the convection in molten salt is often neglected but it noticeably accelerate the opening time of the freeze valve. It was concluded that the convection effect should be taken into consideration in the design of high-performance freeze valve.
International conference proceedings, English

Experimental study on splash ratio and size of secondary droplets during liquid jet collision onto a solid surface
Yi Zhan; Yusuke Kuwata; Kiyotaka Maruyama; Koji Enoki; Tomio Okawa; Mitsuhiro Aoyagi; Takashi Takata
Proceedings of 27th International Conference on Nuclear Engineering (ICONE27), ICONE27-1055, May 2019, Peer-reviwed, If liquid sodium leaks as a liquid jet from pipe in sodium-cooled fast reactors, sodium droplets are produced during liquid jet impingement on the structures. Due to large contact area with surrounding air, generation of secondary droplets may lead to violent fire combustion. In the present work, high speed camera was first used to observe the liquid jet before the impingement. The splash ratio was then measured experimentally. It was shown that a phenomenological model using the impact frequency and the impact Weber number as the important variables can predict the splashing rate well. Distribution of the secondary droplet size was also measured by image analysis. It was indicated that the Sauter mean diameter of the secondary droplets was fairly proportional to the size of primary droplets.
International conference proceedings, English

An experimental study of the freeze valve opening time with considering wall effect
Tatsuya Tokushima; Indarta Kuncoro Aji; Koji Enoki; Motoyasu Kinoshita; Tomio Okawa
Proceedings of 27th International Conference on Nuclear Engineering (ICONE27), ICONE27-1519, May 2019, Peer-reviwed, Nuclear power has a lot of merits including low carbon-dioxide emission and economic advantage. However, it possesses fear factors such as severe accident and radioactive waste. Currently, several new-type reactors are developed to overcome those issues. Molten Salt Reactor (MSR) is one of the generation IV nuclear reactors. To enhance safety, it adopts a passive safety system called freeze valve. Freeze valve is located between the reactor and drain tanks. The salt in the freeze valve is kept in the solid state by forced cooling during normal operation, and melts passively in the occasion of station blackout to discharge the liquid fuel in the reactor vessel to the drain tanks. Obviously, accurate prediction of opening time of freeze valve is important to assure the safety of MSR. In the freeze valve, salt is contained in a metal tube. Since thermal conductivity of the tube wall material is much higher than that of salt, heat conduction within the tube wall may have great impact on the opening time of the freeze valve. Thus, in this study, the wall effect on the opening time of the freeze valve was experimentally investigated. To investigate the wall effect, a metal stick was placed vertically in the frozen HTS (heat transfer salt), and liquid HTS was poured on the frozen HTS. The heat in the liquid HTS was mainly conveyed in the stick by thermal conduction to transferred to the solid HTS. In consequence, melting of solid HTS started around the metal stick rather than the solid-liquid interface. Since tension was applied to the stick in the upward direction, the stick moved upward when the melt interface reached the bottom end of stick. This result suggested that opening of the freeze valve is established along the tube wall in the real MSR plant. To provide experimental data to validate the numerical simulation results, parametric trends of the onset time of stick movement on the several important parameters were investigated. These data can also be used as the guideline to determine the wall material, wall thickness, length of freezing region, and the initial temperature of the frozen salt.
International conference proceedings, English

Experimental Study of Heat Transfer Enhancement and Pressure Drop using TiO2/DW nanofluid Inside Counter Flow Double Tube Heat Exchanger
Ahmad Imam Rifa'i; Muhammad Faisal Hasan; Budi Kristiawan; Agung Tri Wijayanta; Takahiko Miyazaki; Kyaw Thu; Koji Enoki
AIP Conference Proceedings, AMER INST PHYSICS, 2097, 0300433, 23 Apr. 2019, Peer-reviwed, インドネシアのスブラスマーレット大学と九州大学との共同研究成果である．
Scientific journal, English

Experimental Evaluation of the Performance of Heat Pipes with Nanoparticle Layer
Tomio Okawa; Menglei Wang; Koji Enoki
14th International Conference on Heat and Mass Transfer (WSEAS), 1-3, Dec. 2018, Peer-reviwed
International conference proceedings, English

Studies on the Performance of the Heat Exchanger for Thermoacoustic Engines for LNG Cryogenic Energy Storage
Takuto Kobayashi; Koji Enoki; Yusuke Otomo; Yuki Ueda; Atsushi Akisawa; Tomio Okawa; Jumpei Kawasaki
ISTP29 (The 29th International Symposium on Transport Phenomena), ISTP29-141, 02 Nov. 2018, Peer-reviwed
International conference proceedings, English

Droplet generation during liquid jet impingement onto a horizontal plate
Yi Zhan; Naoki Oya; Koji Enoki; Tomio Okawa; Mitsuhiro Aoyagi; Takashi Takata
Experimental Thermal and Fluid Science, Elsevier Inc., 98, 86-94, 01 Nov. 2018, Peer-reviwed, In sodium-cooled fast reactors, liquid sodium leakage from piping may lead to fire accident. In the case that the liquid sodium is discharged as a liquid jet, a number of droplets are produced during liquid jet impingement on the structures
the surfaces of splashed droplets serve as a main reaction field of sodium combustion. In the present work, a liquid jet was emanated vertically downward from a circular nozzle hole onto a horizontal disk to measure the total amount and the maximum size of splashed droplets. It was found that the splashing rate was negligibly small when the liquid jet impinged as a continuous jet whilst a significant amount of liquid was splashed when the liquid jet impinged as a broken jet. Thus, a prediction method was first developed for the impact frequency of the primary droplets produced due to the jet breakup. It was then shown that a phenomenological model using the impact frequency and the impact Weber number as the important variables can predict the splashing rate well. It was also indicated that the size of the maximum splashed droplets was fairly proportional to the size of primary droplets.
Scientific journal, English

Void fraction and heat transfer in subcooled flow boiling
Hiroki OHORI; Shintaro SAKAMOTO; Koji ENOKI; Tomio OKAWA
NUTHOS-12 (12th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety), No.1058, 15 Oct. 2018, Peer-reviwed
International conference proceedings, English

The Characteristics of Water Boiling Heat Transfer, Pressure Drop and Flow Regime in Mini-channel
Koji Enoki; Masaharu Ono; Tomio Okawa; Budi Kristiawan; Agung Tri Wijayanta
ICIMECE2018（International Conference on Industrial, Mechanical, Electrical and Chemical Engineering 2018）, Invited Speaker, IS-173, 10 Oct. 2018, Peer-reviwed, Invited
International conference proceedings, English

Experimental Studi of Heat Transfer Enhancement and Pressure Drop using TiO2/DW nanofluid Inside Counter Flow Double Tube Heat Exchanger
Ahmad Imam Rifai; Muhammad Faisal Hasan; Budi Kristiawan; Agung Tri Wijayanta; Takahiko Miyazaki; Kyaw Thu; Koji Enoki
ICIMECE2018（International Conference on Industrial, Mechanical, Electrical and Chemical Engineering 2018）, AMER INST PHYSICS, ME-074, 09 Oct. 2018, Peer-reviwed, Invited, Nowadays nanofluids are widely used for heat transfer enhancement. Nanometer-sized particles added to base fluid enhance the thermal conductivity and thus increase the heat transfer rate. In the present study TiO2 nanoparticle with the average diameter, 21 nm is used. Titanium dioxide (TiO2) nanofluid prepared by dispersing nanoparticles in distilled water using the two-step method with volume concentration (0.05% - 0.3%), has been investigated. The force convective heat transfer coefficient and friction factor of the TiO2/Distilled water nanofluid with different volume concentration and Reynolds number for flow in a counterflow double tube heat exchanger are studied in this research. The result shows that the convective heat transfer coefficient of nanofluid is higher than base fluid for the same mass flow rate and same inlet temperature of nanofluid. The Nusselt number increases with Reynolds number and volume concentration TiO2/Distilled water of nanofluid. Meanwhile, micro-fin tube increases pressure drop in the flow path.
International conference proceedings, English

Heat transfer coefficient of nucleate boiling in low concentration level of single and hybrid Al2O3-SiO2 water-based nanofluids
M A H Aizzat; Muhamad Zuhairi Sulaiman; Koji Enoki; Tomio Okawa
AIP Conference Proceedings, Materials Science and Engineering, 469, 1, 012109, Oct. 2018, Peer-reviwed, Experiments were conducted to identify the Heat Transfer Coefficient (HTC) in saturated pool boiling of single and hybrid water-based nanofluids. In these experiments, Al 2 O 3 and SiO 2 nanoparticles were selected and diluted into two separate single nanofluids, and they were mixed in a different ratio from 0:100, 25:75, 50:50, 75:25 and 100:0 percent to achieve a final total concentration of 0.001 vol. %. Successively, the mixtures were used to obtain the HTC values through experimental works. In the present work, it was found that in the lowest concentration (0.00025 vol.%) of Al 2 O 3 nanofluid, the HTC enhanced considerably but deteriorated for SiO 2 nanofluid. Separately, as for the hybrid nanofluids, the HTCs were dramatically enhanced at the initial stage but slowly deteriorated once the time variation increased, especially in a higher ratio of SiO 2 nanofluid. The deposition of the nanoparticles onto the surface heater suggested being the main factor, where in the present case, the significant coexisting effect of the deposited hybrid nanoparticles (Al 2 O 3 and SiO 2 ) on the heated surface to the changes of ΔT W due to different nanoparticles properties.
Scientific journal, English

Nanoparticle layer detachment and its influence on the heat transfer characteristics in saturated pool boiling of nanofluids
Yosuke Watanabe; Koji Enoki; Tomio Okawa
International Journal of Heat and Mass Transfer, Elsevier Ltd, 125, 171-178, 01 Oct. 2018, Peer-reviwed, In nucleate pool boiling of nanofluid, nanoparticles suspended in liquid are deposited to form nanoparticle layer on the heated surface. As a result, surface properties are changed and the critical heat flux (CHF) is usually enhanced. However, since adhesion of the nanoparticle layer to the heated surface is not necessarily strong, partial detachment of the nanoparticle layer frequently occurs during nucleate boiling. In this study, peeling test was conducted for the nanoparticle layer formed during nucleate boiling of the water-based nanofluids to measure the adhesion force. The material of the heated surface was copper, and TiO2, Al2O3 and SiO2 were used as the nanoparticle material. It was found that the adhesion force is highly dependent on the nanoparticle material
it was greatest for SiO2 and weakest for TiO2 in the present experiments. Then, saturated pool boiling curves were obtained using the damaged heated surfaces after the peeling. For the nanoparticle-layer coated surfaces without peeling, the heat transfer coefficient (HTC) was lower and CHF was higher than those for the bare surface. It was shown that with an increase in the mass of the nanoparticles removed by peeling, the decrease of HTC and the increase of CHF were mitigated. Even higher HTC values and a lower CHF value than those for the bare heated surface were measured for significantly damaged surfaces.
Scientific journal, English

Observation and modelling of bubble dynamics in isolated bubble regime in subcooled flow boiling
Tomio Okawa; Kazuhiro Kaiho; Shintaro Sakamoto; Koji Enoki
Nuclear Engineering and Design, Elsevier Ltd, 335, 400-408, 15 Aug. 2018, Peer-reviwed, Experiments of subcooled flow boiling in isolated bubble regime were conducted to understand the dynamics of individual bubbles. The test fluid was water, the flow direction was vertical upward, and the pressure was slightly higher than the atmospheric pressure. In the present experiments, the bubbles produced at nucleation sites were commonly lifted off the vertical heated surface. They were then propelled into the subcooled bulk liquid to disappear due to heat transfer with subcooled liquid. It was frequently observed that the bubbles were suddenly accelerated in the lateral direction before the disappearance. Using the present observation results, new correlations were developed for the bubble lift-off velocity and the bubble acceleration phenomenon after the lift-off. It was shown that the bubble trajectories and the time-variation of bubble size calculated using the present correlations are in fairly good agreement with the experimental results.
Scientific journal, English

Static Analysis of A New Scheme of Two Stage Refrigeration Cycle with the Combination of FAM Z01 and FAM Z05 Adsorbents
Atsushi Akisawa; Muhammad Umair; Koji Enoki; Masayuki Nakayama
International Journal of Refrigeration, ELSEVIER SCI LTD, 92, 143-153, Aug. 2018, Peer-reviwed, This paper presents static analyses of two stage adsorption cycle using FAM Z01 and FAM Z05 as the adsorbents. The conventional two stage system consists of four adsorbent beds. In contrast, in new scheme three beds were used assigning FAM Z01 and FAM Z05 combination for low and high pressure sides, respectively. The objectives of this study were to evaluate the performance of two stage cycle with the Z01 and Z05 combination of adsorbent pair, and to compare the performance with that of the conventional two stage cycle using Silica-gel. Static analysis based on Duhring diagram was employed to estimate the performances of specific cooing effect (SCE) and COP. It was found that the cycle with new combination gives SCE more than twice compared with the conventional Silica-gel-water system at the heat source temperature of 55 degrees C. The sensitivity analysis was also performed for optimal mass allocation to adsorbent beds. (C) 2018 Elsevier Ltd and IIR. All rights reserved.
Scientific journal, English

Investigation on tribological behavior of Al2O3 nano cutting fluid under minimum quantity lubrication technique
B. Kristiawan; E. Surojo; S. Fitrina; A. T. Wijayanta; T. Miyazaki; K. Enoki
Grand RENEWABLE ENERGY 2018, Japan Council for Renewable Energy, O-He-5-3, 321, Jun. 2018, Peer-reviwed, Industrial development and application of new methods require extensive studies for getting main goals in manufacturing to minimize production, cost, energy, and resources along with improving the function. In this way, a cutting fluid plays an important role for extending tool life of the cutting tool. Because of this reason, the use of the cutting fluid has to have the proper coolant properties for decreasing cutting temperature and friction coefficient in machining processes. An experimental study is performed for investigating the cooling properties of Al2O3(aluminium oxide) nanofluid with Minimum Quantity Lubrication (MQL) method as the cutting fluid in the machining process. For evaluating the cooling properties of cutting fluid, friction coefficient has been measured by using Pin on Disk machining (ASTM G99). The Pin and Disk are made from carbide drill MWS1130LB and carbon steel SS400, respectively. The MQL technique with using nanofluids in the nanoparticle concentration of 1.2 vol. % and conventional cutting fluid or C5 coolant were tested at a volumetric rate of 250 ml/h and 15 liters/min, respectively. As a result, the observed nanofluid has the best performance for decreasing friction coefficient as 36% on 1000 rpm. However, the coolant properties of C5 coolant are better that Al2O3 nanofluid. It is due to the volume concentration of nanofluid is very high, so the performance of the fluid decreases.
International conference proceedings, English

Simulation analysis of solution transportation absorption chiller with a capacity from 90 kW to 3517 kW
Koji Enoki; Fumi Watanabe; Seigo Tanaka; Atsushi Akisawa; Toshitaka Takei
International Journal of Heat and Mass Transfer, Elsevier Ltd, 118, 193-200, 01 Mar. 2018, Peer-reviwed, The utilization of waste heat instead of fuel combustion is effective in reducing primary energy consumption to mitigate global warming problems. As waste heat sources are not necessarily located close to areas of heat demand, one of the difficulties is that waste heat must be transferred from the heat source side to the heat demand side, which may require the transportation of heat over long distances. From this point of view, we proposed and examined a new idea of heat transportation using ammonia-water as the working fluid in the system named the Solution Transportation Absorption chiller (STA). Our previous studies of the STA were mainly based on the experimental investigation with the STA facility where the cooling power was 25 RT (90 kW). Thus, the Coefficient of Performance (COP) of STA was found to have almost the same value of 0.65 with conventional absorption chillers without depending on the transportation distances. The simulation using AspenHYSYS also examined the same experimental condition. The experimental data showed good agreement with the simulation calculation. In this study, we examined the large-scale cooling power of the STA on the simulation. The intention of this study was to analyze sensitivity with large cooling capacities, the examined cooling powers were from 90 kW (25 RT) to 3517 kW (1000 RT). All cooling power achieved around COP 0.64 including pump power consumption. In addition, we performed a dynamic simulation. The results showed that pipeline size did not affect the cooling capacities and mass flow rates. Furthermore, the stability time of the cooling capacities and mass flow rates were almost the same regardless of the pipeline size and cooling capacity. In other words, the STA may achieve the same COP despite having various complex conditions compared with the conventional absorption chiller.
Scientific journal, English

MODELING OF BUBBLE BEHAVIOR IN LOW VOID FRACTION SUBCOOLED FLOW BOILING
Shintaro Sakamoto; Hiroki Ohori; Koji Enoki; Tomio Okawa
PROCEEDINGS OF THE 26TH INTERNATIONAL CONFERENCE ON NUCLEAR ENGINEERING, 2018, VOL 9, AMER SOC MECHANICAL ENGINEERS, 9, 2018, Peer-reviwed, In predicting the void fraction in subcooled flow boiling, accurate evaluation of single bubble behaviors is of considerable importance. In particular, bubble lift-off velocity affects the void fraction significantly since the bubble disappear quickly due to heat transfer with subcooled liquid if the lift-off velocity is high. In this study, the process of bubble lift-off was experimentally investigated to develop mechanistic correlations for the bubble lift-off velocity. In the development of the correlations, it was assumed that the bubble lift-off velocity in the horizontal direction is proportional to the bubble growth rate and that in the vertical direction is determined primarily by the local liquid velocity evaluated at the bubble center position. Then, impact of the bubble lift-off velocity on the void fraction was explored through numerical simulations. In the simulations, the bubble lift-off velocity in the lateral direction was parametrically changed. It was shown that the mean void fraction decreases with an increase in the lateral bubble lift-off velocity since the bubble condensation is enhanced. It was therefore confirmed that accurate evaluation of the bubble lift-off velocity is important for high accuracy prediction of the void fraction.
International conference proceedings, English

Effects of Oscillation on Vapor-liquid Two-phase Flow Patterns in Small Rectangular Tube
Masaharu Ono; Kunihiro Nagayama; Koji Enoki; Atsushi Akisawa; Tomio Okawa; Hideo Mori
Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers, 日本冷凍空調学会, 34, 4, 335-344, 31 Dec. 2017, Peer-reviwed, In this study, experiments were performed to observe horizontal vapor-liquid two-phase flow of refrigerant R 134a in the rectangular glass channel whose hydraulic diameter was 0.84 mm by using a high-speed camera. The experiment results of flow patterns were compared with existing flow pattern map. Further, the effects of oscillation on slug and stratified flow were investigated by observing flow as a reciprocating motor vertically oscillated the channel. The slug flow was observed at heat fluxes of 2.5 and 9.5 kW･m^-2, and the stratified flow was at a heat flux of 2.5 kW･m^-2. When the channel was oscillated at certain frequency and amplitude, the thin liquid film around vapor plug was largely waved up and down. As the result, the dry surface around vapor plug of slug flow, which is considered as a reason for decline in heat transfer coefficient, did not occur. Furthermore, stratified flow was transformed to annular flow, and dry surface on upper side of the channel also did not occur. These effects and transformation were classified into several patterns, and the influence of maximum acceleration was examined.
Scientific journal, Japanese

Elucidation of Flow Distribution of Two-phase Flow in the Parallel Mini-channel Evaporator
Masaharu Ono; Koji Enoki; Keisuke Kanja; Taichi Nakamura; Tomio Okawa; Kosaku Nishida; Masashi Kato
Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers, Japan Society of Refrigerating and Air Conditioning Engineers, 34, 4, 413-424, 31 Dec. 2017, Peer-reviwed, Invited, In this study, the experiments were performed to observe vertically upward vapor-liquid two-phase flow of HFE-7000 in the parallel microchannel whose hydraulic diameter was 0.93 mm per a path by using a high-speed camera. The experiments were conducted by heating the microchannel portion for use as evaporator. The saturation temperature was 30 °C. In order to investigate the influence of the inlet qualities of the test section on the flow pattern, the experiments were conducted to keep exit quality at xout = 0.9 and mass flow rate W = 0.0022 kg･s^-1, set inlet qualities at xin = 0, 0.2 0.7. From the results of the observation, it was clear that the cause of drift flow was unevenness of the vapor and liquid distribution in the inlet header. Moreover, back flow which is thought to degrade the heat exchanger performance was observed as well, and it was found that the cause was rapid expansion of the vapor plug. Therefore, when the inlet header part was made a modified shape narrowing the flow path area as it goes away from the test section inlet part, drift flow and back flow were suppressed. Furthermore, in order to investigate the influence on the heat exchanging performance by drift flow and back flow, the downstream side of the test section was photographed and measured using an IR camera. In the case of a vapor-liquid mal-distribution in the inlet header section, temperature rise accompanying dryout had been constantly occurring on the downstream side in the flow path near the test section inlet. However, in the case of the modified inlet header shape, it was found that the mal-distribution of the heat distribution on the downstream side due to the drift was reduced.
Scientific journal, Japanese

Prediction for Flow Boiling Heat Transfer in Small Diameter Tube Using Deep Learning
Koji Enoki; Yuichi Sei; Tomio Okawa; Kiyoshi Saito
Japanese Journal of Multiphase Flow, The Japanese Society for Multiphase Flow, 31, 4, 412-421, 15 Dec. 2017, Peer-reviwed, The applications of Artificial Intelligence ie AI show diversity in any fields. On the other hand, research of the predicting heat transfer regardless of single-phase or two-phase flow is still untouched. Therefore, we have confirmed usefulness using AI’s deep learning function on horizontal flow boiling heat transfer in flowing mini-channel that is actively researched. The effect of the surface tension in the mini-channel is large compared with conventional large tubes, and then the heat transfer mechanism is very complicated. For this reason, the numerical correlations of many existing researchers the prediction result is not good. However, the mechanistic correlation based on the visualization experiment, which the authors' research group published several years ago has very high precision. Therefore, in this research paper, we confirmed the effectiveness of using deep learning for predicting of the boiling heat transfer in mini-channel while comparing our correlation.
Scientific journal, Japanese

Performance of thermal energy transportation based on absorption heat pump cycle over 200 m distance - Solution transportation absorption chiller
Atsushi Akisawa; Fumi Watanabe; Koji Enoki; Toshitaka Takei
APPLIED THERMAL ENGINEERING, PERGAMON-ELSEVIER SCIENCE LTD, 127, 1200-1205, Dec. 2017, Peer-reviwed, The authors proposed "Solution Transportation Absorption Chiller" which is driven by wasted heat and transfers absorbent solution instead of chilled water. It consists of generator-condenser pair on the heat source side, absorber-evaporator pair on the demand side and pipelines between them. In this study, the authors investigated the heat transportation performance of the system experimentally with the distance of 100 m, 200 m and 1000 m. The results suggest that the proposed system can work for transporting cooling with ammonia-water mixture as the working fluid. It was obtained that the COP of the system was the same as that of conventional absorption chiller without transportation. In other words, the performance does not suffer from the new function of long distance transportation. It can be concluded that the solution transportation is technologically feasible and also effective to replace conventional fossil fuels with remote wasted heat sources. (C) 2017 Elsevier Ltd. All rights reserved.
Scientific journal, English

Effect of surface properties on quenching characteristics of high-temperature body
Y. Umehara; K. Enoki; W. Liu; T. Okawa
10th International Symposium on Measurement Techniques for Multiphase Flow 2017, ISMTMF-R001-113, Dec. 2017, Peer-reviwed
International conference proceedings, English

Effect of surface properties on quenching characteristics of high-temperature body
Y. Umehara; K. Enoki; W. Liu; T. Okawa
10th International Symposium on Measurement Techniques for Multiphase Flow 2017, ISMTMF-R001-113, Dec. 2017, Peer-reviwed
International conference proceedings, English

Experimental investigation of the effect of generator temperature on the performance of solution transportation absorption chiller
Koji Enoki; Fumi Watanabe; Atsushi Akisawa; Toshitaka Takei
International Journal of Air-Conditioning and Refrigeration, World Scientific Publishing Co. Pte Ltd, 25, 3, 1750028-1-1750028-8, 01 Sep. 2017, Peer-reviwed, It is effective to recover waste heat to reduce primary energy consumption. From this point of view, we proposed and examined a new idea of heat transportation using ammonia-water as the working fluid in the system named the Solution Transportation Absorption chiller (STA). As waste heat sources are not necessarily located close to areas of heat demand, conventionally, absorption chillers are located on heat source side and produce chilled water that is transported to heat demand side through pipelines with an insulation. In contrast, the proposed system STA divides an absorption chiller into two parts. The generator and the condenser are located on heat source side while the evaporator and the absorber are on heat demand side. Both the conventional system and STA system satisfy the same boundary condition of heat recovery and heat supply to the demand side, STA can work for transferring thermal energy as the conventional system does even though the temperature of the media is ambient without an insulation. Our previous studies of the STA were based on the experimental investigation with the STA facility where the cooling power was 90kW (25.6 refrigeration ton) at the generator temperature 120°C from 0m (normal absorption chiller) to 1000m. Thus, the Coefficient of Performance (COP) of STA was found to have almost the same value of 0.65 with conventional absorption chillers without depending on the transportation distances. The objective of this study is to examine the effect of generator temperature from 100°C to 120°C on the performance of solution transportation of ammonia-water solution, because the generator temperature is directly linked to the waste heat temperature, so its effect needs to be investigated. The experimental facility tested the performance with 0m (normal absorption chiller), 200m and 500m distance. The results indicate that the effect of the generator temperature and solution transportation distances showed no significant on the COP.
Scientific journal, English

Characteristics of Bubbles Produced At Nucleation Sites in Subcooled Flow Boiling
Tomio Okawa; Kazuhiro Kaiho; Shintaro Sakamoto; Koji Enoki
17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 306-1, Sep. 2017, Peer-reviwed, In subcooled flow boiling region, wall heat flux is spent for vaporization and temperature rise of liquid phase. Thus, accurate evaluation of vaporization rate is of considerable importance in estimating the void fraction in this region that influences the natural circulation flow rate, two-phase flow stability, fuel burnup, and transient response in RIA (Reactivity-Initiated Accident) event. In the present work, bubble production process in water subcooled flow boiling at low pressure was visualized in detail to measure the nucleation site density, the bubble size, the bubble release frequency, and the vaporization rate. Appropriate correlations were selected for the nucleation site density and the bubble release frequency. New dimensionless correlations were developed for the bubble size distribution since no such correlation was available in literature. It was found that the bubbles of various sizes are produced in subcooled flow boiling and the effect of bubble size distribution should be taken into consideration for accurate prediction of the vaporization rate.
International conference proceedings, English

Peeling of Nanoparticle Layer on a Heated Surface and Its Influence on Pool Boiling CHF
Tomio Okawa; Yosuke Watanabe; Koji Enoki
17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), N/A, Sep. 2017, Peer-reviwed, Nanofluid is paid particular attention as the promising method to enhance critical heat flux in boiling heat transfer. It is considered that the CHF enhancement is mainly caused by the modification of surface properties such as the wettability and roughness due to the formation of nanoparticle layer on the heated surface. However, since adhesion of the nanoparticle layer is not firm, peeling of the layer often occurs during boiling. In the present work, peeling test was conducted to measure quantitatively the adhesion strength of the nanoparticle layer formed on the heated surface. The material of the heated surface was copper and titanium-dioxide, alumina, and silica were selected as the materials of nanoparticles. It was found that the total mass and the adhesion strength of the nanoparticle layer were dependent strongly on the particle material. The CHF enhancement ratio by nanoparticle layer tended to decrease with an increase in the peeling ratio. It may be interesting to note that the boiling heat transfer was improved whilst CHF was deteriorated with the increase of the loss of nanoparticles.
International conference proceedings, English

Bubble tracking simulation of subcooled flow boiling
Tomio Okawa; Kazuhiro Kaiho; Shintaro Sakamoto; Koji Enoki
Proceedings of Japan-U.S. Seminar on Two-Phase Flow Dynamics 2017, D2, Jun. 2017, Peer-reviwed
International conference proceedings, English

Measurement of the maximum bubble size distribution in water subcooled flow boiling at low pressure
Kazuhiro Kaiho; Tomio Okawa; Koji Enoki
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, PERGAMON-ELSEVIER SCIENCE LTD, 108, 2365-2380, May 2017, Peer-reviwed, Bubbles of various Sizes are produced at nucleation sites on a heated surface in subcooled flow boiling. However, although many correlations have been developed so far for the mean bubble size, systematic information is scarce for the bubble size distribution. In the present work, bubble nucleation process in water subcooled flow boiling at low pressure was observed in detail using an ITO-deposited transparent glass plate as the heated surface. It was found that bubbles of different sizes are produced at each nucleation site and moreover the mean bubble size differs considerably between different sites. It was hence considered that the reliability of subcooled flow boiling analysis codes can be improved if the effect of the bubble size distribution is included. In view of this, quantitative investigation was done for the bubble size distribution. It was shown that under the experimental conditions tested in this work, the distribution of the maximum size of individual bubbles produced at nucleation sites are fitted well with the gamma distribution. The dependences of the measured maximum bubble size distribution on important dimensionless numbers were explored to develop new correlations for the bubble size distribution. (C) 2017 Elsevier Ltd. All rights reserved.
Scientific journal, English

Stable, calm, and high-heat –flux removal using a porous-microchannel
Okawa. T; Ohashi. J; Hirata. R; Enoki. K
TFEC-IWHT2017-18154, 02 Apr. 2017, Peer-reviwed
International conference proceedings, English

Experiment and Visualization of R 410A Flow Distribution within the Vertical Header of Microchannel Heat Exchanger
Redo. M. A; Giannetti. N; Jeong. J; Ota. I; Saito. K; Enoki. K; Kim. H
5TH IIR INTERNATIONAL CONFERENCE ON THERMOPHYSICAL PROPERTIES AND TRANSFER PROCESSES OF REFRIGERANTS (TPTPR), INT INST REFRIGERATION, 44-243, Apr. 2017, Peer-reviwed, This paper reports an initial step to obtain an equally distributed fluid flow in an evaporator heat exchanger and eventually increase its performance. Experiments are carried out for R410A, using a vertical header where 20 horizontal parallel flat tubes are connected and the protrusion depth is half of the header width. The flow enters the header from a bottom inlet port and there is no heat load applied on the flat tubes. Inlet vapor quality before the header is varied for a fixed total mass flow rate of 60 kg/h. For each set of conditions, the mass flow rate and quality at different vertical positions of the header are singularly measured. Visualization data and experimental results have shown that 0.6 vapor quality before the header produces a more even distribution having a more homogeneous two-phase flow compared to 0.2 where phases are distinctly separated yielding dryouts on the top channels.
International conference proceedings, English

Stable, calm, and high-heat-flux heat removal using a porous-microchannel
Tomio Okawa; Junki Ohashi; Ryo Hirata; Koji Enoki
Proceedings of 4th International Workshop on Heat Transfer (IWHT), TFEC-IWHT2017-18154, Apr. 2017, Peer-reviwed
International conference proceedings, English

Experiment and Visualization of R 410A Flow Distribution within the Vertical Header of Microchannel Heat Exchanger
Redo. M. A; Giannetti. N; Jeong. J; Ota. I; Saito. K; Enoki. K; Kim. H
5th IIR International Conference on Thermophysical Properties and Transfer Processes of Refrigerants, INT INST REFRIGERATION, 044, 44-898, Apr. 2017, Peer-reviwed, with international co-author(s), This paper reports an initial step to obtain an equally distributed fluid flow in an evaporator heat exchanger and eventually increase its performance. Experiments are carried out for R410A, using a vertical header where 20 horizontal parallel flat tubes are connected and the protrusion depth is half of the header width. The flow enters the header from a bottom inlet port and there is no heat load applied on the flat tubes. Inlet vapor quality before the header is varied for a fixed total mass flow rate of 60 kg/h. For each set of conditions, the mass flow rate and quality at different vertical positions of the header are singularly measured. Visualization data and experimental results have shown that 0.6 vapor quality before the header produces a more even distribution having a more homogeneous two-phase flow compared to 0.2 where phases are distinctly separated yielding dryouts on the top channels.
International conference proceedings, English

A 1/2.3inch 20Mpixel 3-layer stacked CMOS Image Sensor with DRAM
Tsutomu Haruta; Tsutomu Nakajima; Jun Hashizume; Taku Umebayashi; Hiroshi Takahashi; Kazuo Taniguchi; Masami Kuroda; Hiroshi Sumihiro; Koji Enoki; Takatsugu Yamasaki; Katsuya Ikezawa; Atsushi Kitahara; Masao Zen; Masafumi Oyama; Hiroki Koga; Hidenobu Tsugawa; Tomoharu Ogita; Takashi Nagano; Satoshi Takano; Tetsuo Nomoto
Digest of Technical Papers - IEEE International Solid-State Circuits Conference, Institute of Electrical and Electronics Engineers Inc., 60, 76-77, 02 Mar. 2017, Peer-reviwed, In recent years, the performance of cellphone cameras has improved, and is becoming comparable to that of SLR cameras. However, the big difference between cellphone cameras and SLR cameras is the distortion due to the rolling exposure of CMOS image sensors (CISs) because cellphone cameras cannot have a mechanical shutters [1]. In addition to this technical problem, the demands for high quality in dark situations and for movies are increasing. Frame-level signal processing can solve these problems, but previous generations of CIS could not achieve both high-speed readout and accessible I/F speed. This paper presents 3-layer-stacked back-illuminated CMOS Image Sensor (3L-BI-CIS) with mounted DRAM as the frame memory.
International conference proceedings, English

Experiments on the splashing limit during drop impact onto a thin liquid film
Sota Kitabayashi; Koji Enoki; Tomio Okawa
International Conference on Nuclear Engineering, Proceedings, ICONE, American Society of Mechanical Engineers (ASME), 9, 2017, Peer-reviwed, The phenomenon of secondary droplet production during single drop impingement onto a liquid film is encountered in many industrial situations. Typical examples in the field of nuclear engineering are the spray cooling of hot surface and the atomization of radioactive liquids in severe accident. Therefore, the prediction of the onset of secondary droplet production is very important. It is known that the two types of droplet splashing mechanisms are present: the prompt splash and the late splash. The main purpose of this research is to determine the splashing limit separately for the prompt splash and the late splash. It is expected that the splashing limits are expressed using the three dimensionless numbers: the Weber number, the Ohnesorge number, and the dimensionless film thickness. Experiments were hence carried out using pure water and silicone oil as the working liquid. The experimental ranges were 129-606 for the Weber number, 0.00183-0.00300 for the Ohnesorge number, and 0.13-3.0 for the dimensionless film thickness. It was found that the occurrence of splashing can be predicted more accurately if the splashing limit is evaluated separately for the prompt splash and the late splash.
International conference proceedings, English

Splash during liquid jet impingement onto a horizontal plate
Yi Zhan; Naoki Oya; Koji Enoki; Tomio Okawa; Shuji Ohno; Mitsuhiro Aoyagi; Takashi Takata
International Conference on Nuclear Engineering, Proceedings, ICONE, American Society of Mechanical Engineers (ASME), 9, 2017, Peer-reviwed, In the numerical analysis of sodium fire event following coolant leakage in a sodium-cooled fast reactor, sufficient understanding is needed for the liquid jet atomization to estimate the combustion rate accurately. In the present work, a liquid jet was emanated vertically downward from a circular nozzle onto a liquid film formed on a horizontal plate. The droplets produced at the impact point were investigated. The splash ratio (the ratio of the mass of the splashed droplets to the jet flow rate) was measured under varied experimental conditions of nozzle diameter, fall height and flow rate of liquid jet. The experimental result depended significantly on the morphology of liquid jet upon impact. The splashing rate was negligibly small when the liquid jet impinged as the continuous jet but a significant amount of liquid was splashed when the liquid jet impinged as the broken jet. Thus, we developed a method to estimate the impact frequency. It was shown that the splash ratio can be correlated well if the impact frequency is included in the correlation.
International conference proceedings, English

Splash during liquid jet impingement onto a horizontal plate
Yi Zhan; Naoki Oya; Koji Enoki; Tomio Okawa; Shuji Ohno; Mitsuhiro Aoyagi; Takashi Takata
International Conference on Nuclear Engineering, Proceedings, ICONE, American Society of Mechanical Engineers (ASME), 9, 2017, Peer-reviwed, In the numerical analysis of sodium fire event following coolant leakage in a sodium-cooled fast reactor, sufficient understanding is needed for the liquid jet atomization to estimate the combustion rate accurately. In the present work, a liquid jet was emanated vertically downward from a circular nozzle onto a liquid film formed on a horizontal plate. The droplets produced at the impact point were investigated. The splash ratio (the ratio of the mass of the splashed droplets to the jet flow rate) was measured under varied experimental conditions of nozzle diameter, fall height and flow rate of liquid jet. The experimental result depended significantly on the morphology of liquid jet upon impact. The splashing rate was negligibly small when the liquid jet impinged as the continuous jet but a significant amount of liquid was splashed when the liquid jet impinged as the broken jet. Thus, we developed a method to estimate the impact frequency. It was shown that the splash ratio can be correlated well if the impact frequency is included in the correlation.
International conference proceedings, English

Experiments on the splashing limit during drop impact onto a thin liquid film
Sota Kitabayashi; Koji Enoki; Tomio Okawa
International Conference on Nuclear Engineering, Proceedings, ICONE, American Society of Mechanical Engineers (ASME), 9, 2017, Peer-reviwed, The phenomenon of secondary droplet production during single drop impingement onto a liquid film is encountered in many industrial situations. Typical examples in the field of nuclear engineering are the spray cooling of hot surface and the atomization of radioactive liquids in severe accident. Therefore, the prediction of the onset of secondary droplet production is very important. It is known that the two types of droplet splashing mechanisms are present: the prompt splash and the late splash. The main purpose of this research is to determine the splashing limit separately for the prompt splash and the late splash. It is expected that the splashing limits are expressed using the three dimensionless numbers: the Weber number, the Ohnesorge number, and the dimensionless film thickness. Experiments were hence carried out using pure water and silicone oil as the working liquid. The experimental ranges were 129-606 for the Weber number, 0.00183-0.00300 for the Ohnesorge number, and 0.13-3.0 for the dimensionless film thickness. It was found that the occurrence of splashing can be predicted more accurately if the splashing limit is evaluated separately for the prompt splash and the late splash.
International conference proceedings, English

Splash during liquid jet impingement onto a horizontal plate
Yi Zhan; Naoki Oya; Koji Enoki; Tomio Okawa; Shuji Ohno; Mitsuhiro Aoyagi; Takashi Takata
International Conference on Nuclear Engineering, Proceedings, ICONE, American Society of Mechanical Engineers (ASME), 9, 2017, Peer-reviwed, In the numerical analysis of sodium fire event following coolant leakage in a sodium-cooled fast reactor, sufficient understanding is needed for the liquid jet atomization to estimate the combustion rate accurately. In the present work, a liquid jet was emanated vertically downward from a circular nozzle onto a liquid film formed on a horizontal plate. The droplets produced at the impact point were investigated. The splash ratio (the ratio of the mass of the splashed droplets to the jet flow rate) was measured under varied experimental conditions of nozzle diameter, fall height and flow rate of liquid jet. The experimental result depended significantly on the morphology of liquid jet upon impact. The splashing rate was negligibly small when the liquid jet impinged as the continuous jet but a significant amount of liquid was splashed when the liquid jet impinged as the broken jet. Thus, we developed a method to estimate the impact frequency. It was shown that the splash ratio can be correlated well if the impact frequency is included in the correlation.
International conference proceedings, English

Production of droplets during liquid jet impingement onto a flat plate
Zhan. Y; Oya. N; Enoki. K; Okawa. T; Ohno. S; Aoyagi. M; Takata. T
N10P1122, 29 Nov. 2016, Peer-reviwed
International conference proceedings, English

Production of droplets during liquid jet impingement onto a flat plate
Zhan. Y; Oya. N; Enoki. K; Okawa. T; Ohno. S; Aoyagi. M; Takata. T
10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS10),, N10P1122, 29 Nov. 2016, Peer-reviwed
International conference proceedings, English

Systematic measurements of heat transfer characteristics in saturated pool boiling of water-based nanofluids
Muhamad Zuhairi Sulaiman; Daisuke Matsuo; Koji Enoki; Tomio Okawa
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, PERGAMON-ELSEVIER SCIENCE LTD, 102, 264-276, Nov. 2016, Peer-reviwed, Experiments were carried out to investigate the heat transfer characteristics in saturated pool boiling of water-based nanofluids. An upward-facing copper surface of 20 mm in diameter was used as the heated surface. Main experimental parameters in this work were nanoparticles' material (TiO2, Al2O3 and SiO2), mass concentration (0.04, 0.4 and 1 kg/m(3)) and dispersion condition (fine and coarse dispersions). Effects of these parameters on the time-variation of wall superheat under constant heat flux, the heat transfer coefficient (boiling curve) and the critical heat flux (CHF) were explored. It was found that the particle dispersion condition has no noticeable influence on the heat transfer characteristics within the range tested in this work. Whilst, the material and concentration of nanoparticles greatly affected the time variation of wall superheat and the boiling curve. In particular, it was found that the wall superheat likely to increase significantly when the nanoparticle layer formed on the heated surface is partially detached. The CHF in nanofluid was 2.5-3 times higher than that for pure water in all the experimental conditions. (C) 2016 Elsevier Ltd. All rights reserved.
Scientific journal, English

Boiling Heat Transfer and Flow Regime of Water Flowing Vertically Upward in a Mini-channel
Ono. M; Nakamura. T; Enoki. K; Okawa. T; Ozawa. M
日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, 日本冷凍空調学会, 2037-1-6, Nov. 2016, Peer-reviwed
International conference proceedings, English

Visualization of Bubbles in Water Subcooled Flow Boiling for Highly Accurate Estimation of Void Fraction
Kaiho. K; Sakamoto. S; Enoki. K; Okawa. T
N10P1121, Nov. 2016, Peer-reviwed
International conference proceedings, English

Visualization of Bubbles in Water Subcooled Flow Boiling for Highly Accurate Estimation of Void Fraction
Kazuhiro Kaiho; Shintaro Sakamoto; Koji Enoki; Tomio Okawa
10th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS10), N10P1121, Nov. 2016, Peer-reviwed
International conference proceedings, English

Performance estimation of once-through boiler using small-diameter water tubes
Tomio Okawa; Mamoru Ozawa; Koji Enoki; Masaharu Ohno; Taichi Nakamura
Journal of Japan Boiler Association, 日本ボイラ協会, 399, 399, 9-16, 15 Oct. 2016, Peer-reviwed
Scientific journal, Japanese

Boiling Heat Transfer and Pressure Drop of a Refrigerant R32 Flowing in a Small Horizontal Tube
Yudai Matsuse; Koji Enoki; Hideo Mori; Keishi Kariya; Yoshinori Hamamoto
HEAT TRANSFER ENGINEERING, TAYLOR & FRANCIS INC, 37, 7-8, 668-678, May 2016, Peer-reviwed, In this study, experiments were performed to examine characteristics of flow boiling heat transfer and pressure drop of a low global warming potential refrigerant R32 flowing in a horizontal copper circular tube with 1.0 mm inside diameter for the development of a high-performance heat exchanger using small-diameter tubes or minichannels for air conditioning systems. Axially local heat transfer coefficients were measured in the range of mass fluxes from 30 to 400 kg/(m(2<bold>)s</bold>), qualities from 0.05 to 1.0, and heat fluxes from 2 to 24 kW/m(2) at the saturation temperature of 10 degrees C. Pressure drops were also measured in the rage of mass fluxes from 30 to 400 kg/(m(2<bold>)s</bold>) and qualities from 0.05 to 0.9 at the saturation temperature of 10 degrees C under adiabatic condition. In addition, two-phase flow patterns were observed through a sight glass fixed at the tube exit with a digital camera. The characteristics of boiling heat transfer and pressure drop were clarified based on the measurements and the comparison with data of R410A obtained previously. Also, measured heat transfer coefficients were compared with two existing correlations.
Scientific journal, English

Hight-heat flux heat removal using a porous-micro-channel
Ohashi. J; Tsukamoto. A; Enoki. K; Okawa. T
PBNC2016, 26 Apr. 2016, Peer-reviwed
International conference proceedings, English

EXPERIMENTAL STUDY ON SPLASHING DURING LIQUID JET IMPINGEMENT ONTO A LIQUID FILM
Zhan Yi; Naoki Oya; Koji Enoki; Tomio Okawa; Shuji Ohno; Mitsuhiro Aoyagi
PROCEEDINGS OF THE 24TH INTERNATIONAL CONFERENCE ON NUCLEAR ENGINEERING, 2016, VOL 5, AMER SOC MECHANICAL ENGINEERS, ICONE24-60318, 2016, Peer-reviwed, A liquid jet is of considerable importance in many industrial fields including jet cleaning, jet engine and combustion. As an important example, the Monju nuclear power plant in Japan experienced a sodium leak in 1995. This led to a fire accident because the sodium reacted with oxygen in the air. To predict the significance of the fire accident, accurate evaluation of the amount of splashed droplets caused by the sodium jet impingement is of great importance. In this work, the relationship between the condition of a liquid jet and the amount of splashed droplets is explored experimentally. In the experiments, a liquid jet was emanated vertically downward from a circular nozzle onto a liquid film formed on a horizontal plate. Visualization using a high speed camera was performed to observe the condition of the liquid jet. From the nozzle, the mode of the liquid jet changed jet, lump and drop. Here, the jet mode means the continuous jet with smooth surface, the lump mode the continuous jet with, disturbed surface and the drop mode the broken jet. Dependences of the transition length to each mode on the important parameters such as the jet velocity and the nozzle diameter were investigated. Measurement was also conducted for the splash ratio that is defined as the ratio of the amount of splashed droplets to the jet flow rate. It was found that the splash ratio is high when the liquid jet is in the drop mode at the impact point. It was shown that the splash ratio can be correlated well as a function of the impact Weber number and the Strouhal number of the droplets impinging the liquid film.
International conference proceedings, English

ACCURATE ESTIMATION OF VAPORIZATION RATE IN SUBCOOLED FLOW BOILING BASED ON THE RESULTS OF VISUALIZATION EXPERIMENT
Kazuhiro Kaiho; Koji Enoki; Tomio Okawa
PROCEEDINGS OF THE 24TH INTERNATIONAL CONFERENCE ON NUCLEAR ENGINEERING, 2016, VOL 5, AMER SOC MECHANICAL ENGINEERS, ICONE24-60088, 2016, Peer-reviwed, This research presents experimental approaches to accumulate the data for mechanistic model in subcooled flow boiling. A number of photographic studies have been provided to investigate phenomena of bubble nucleation and condensation process for accurate prediction of void fraction such as bubble detachment diameter, bubble detachment frequency and nucleation site density in a subcooled flow boiling. In this work, a transparent heated surface was used to obtain the data from back side of heated surface to avoid overlapping bubbles by using high speed video camera. It enabled to observe bubble nucleation process and active nucleation sites. The experiment was performed in a vertical rectangular channel at atmospheric pressure and the water was used as test fluid. In generally, the computational analysis for a subcooled flow boing deal with mean bubble size as the size of bubbles produced on heated surface. Although, it was found that mean bubble size can represent bubbles produced at same site because they are almost uniform size. Even though the size of bubbles at same site are almost uniform, the difference of the size of bubbles between other sites are considerable value. Therefore, mean bubble size on the surface should not represent bubbles for all site otherwise the serious error may be caused. It seems that bubble detachment diameter should not be given by correlations of mean bubble detachment diameter for accurate prediction of vaporization rate. Some researchers proposed that bubble size distribution should be considered by Gaussian distribution [1-3]. However, it found that bubble size distribution data accumulated in this work cannot be fitted by Gaussian distribution and there are probability that larger bubbles are neglected due to the configuration features of Gaussian distribution. So, Gamma distribution was used to predict the bubble size distribution and it was evaluated in terms of heat flux, wall superheat, mass flux and liquid subcooling. And then, by the experimental approaches, the important dimensionless parameters are identified such as Nusselt number, Jakob number, Reynolds number and dimensionless subcooling. Furthermore, vaporization rate was calculated by correlations of bubble detachment diameter, bubble detachment diameter and nucleation site density and compared with the data. Finally, the effect of using mean bubble size or bubble size distribution on vaporization rate was investigated.
International conference proceedings, English

NUMERICAL SIMULATION OF SUBCOOLED FLOW BOILING USING A BUBBLE TRACKING METHOD
Tomio Okawa; Naoki Miyano; Kazuhiro Kaiho; Koji Enoki
PROCEEDINGS OF THE 24TH INTERNATIONAL CONFERENCE ON NUCLEAR ENGINEERING, 2016, VOL 3, AMER SOC MECHANICAL ENGINEERS, ICONE24-60088, 2016, Peer-reviwed, The process of bubble nucleation in subcooled flow boiling was visualized using a high speed camera to show that the bubble size can be significantly different between the nucleation sites. However, the bubble size is usually assumed constant in the numerical simulation of subcooled flow boiling. To explore the effect of the bubble size distribution on the void fraction in subcooled flow boiling, numerical simulations were performed using a bubble tracking method in which the size and position of each bubble are calculated individually using a Lagrangian coordinates. In the present simulation, the void fraction was greater when the bubble size distribution was taken into consideration. Since the bubble tracking method requires many correlations, further improvement is necessary. The present numerical results however indicate that the bubble size distribution should be taken in to consideration to evaluate the void fraction in subcooled flow boiling accurately.
International conference proceedings, English

低温熱駆動に向けた３つの吸着器を用いる二段型吸着冷凍サイクルの実証
高橋郁也; 榎木光治; 秋澤淳; 窪川清一; 吉江建一; 米澤泰夫
日本冷凍空調学会論文集 = Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers, 日本冷凍空調学会, 32, 3, 363-371, 30 Sep. 2015, Peer-reviwed, Adsorption refrigerators are able to generate cold water using low temperature waste heat, and are effective in reducing fossil fuel consumption and peak electric loads. In order to facilitate introduction of adsorption refrigerators, miniaturization of the machine and further lowering operation temperature are essential. In the present study, we experimentally investigated two-stage adsorption cycle with three Beds, which conventionally needs four Beds, using FAM-Z01 and Z05. The results showed that the cycle generated cooling ability of around 0.6 kW using hot water of 55 degrees Celsius. Therefore, we verified that miniaturization of the machine and lowering operation temperature can be achieved.
Scientific journal, Japanese

動的シミュレーションを用いたNH3－H2O系溶液輸送型吸収冷凍機の輸送配管が制御性および冷媒受液器に及ぼす影響
渡辺史; 田中成吾; 榎木光治; 秋澤淳; 武居俊孝
日本冷凍空調学会論文集 = Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers, 日本冷凍空調学会, 32, 3, 353-362, 30 Sep. 2015, Peer-reviwed
Scientific journal, Japanese

微細流路内沸騰熱伝達整理式の修正
榎木光治; 宮田一司; 森英夫
日本冷凍空調学会論文集 = Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers, 日本冷凍空調学会, 32, 3, 275-283, 30 Sep. 2015, Peer-reviwed, For the local flow boiling heat transfer coefficient in small diameter circular tubes, the authors had previously proposed a prediction correlation, in which the liquid film conductive evaporation heat transfer peculiar to small diameter tubes was taken into account in addition to forced convective evaporation and nucleate boiling. The liquid film conductive evaporation is the evaporation of the thin liquid film around vapor plugs in slug flow due to conduction through the film and shows considerably good heat transfer. However, this correlation was found not to be accurately applicable to high vapor pressure refrigerants and the flow at low flow rate in horizontal small tubes. Based on new experimental data, the correlation was partly modified to overcome these shortcomings. Compared with existing correlations, the improved correlation has higher prediction performance for 410A data by the authors and for a number of experimental data by the other researchers including R 32, R 1234yf, H2O and CO2. The good prediction performance of the present correlation is shown in the following figure.

Scientific journal, Japanese

Simulation analysis of solution transportation absorption chiller with the capacity from 25RT to 1000RT
Koji Enoki; Seigo Tanaka; Fumi Watanabe; Atushi Akisawa; Yuki Ueda; Toshitaka Takei
Refrigeration Science and Technology, International Institute of Refrigeration, 431, 3834-3841, 2015, Peer-reviwed, Utilization of wasted heat instead of fuel combustion is effective to reduce primary energy consumption for mitigating global warming problem. Because wasted heat sources are not necessarily located close to areas of heat demand, one of the difficulties is that wasted heat has to be transferred from heat source side to heat demand side, which may require heat transportation over long distance. From this point we proposed and have examined new idea of heat transportation using ammonia-water as the working fluid which system is named Solution Transportation Absorption chiller, in short STA. Our previous studies of STA were mainly the experimental investigation with STA facility which cooling power was 25RT (90kW). As a result, the COP of STA was found almost same value 0.65 with the conventional absorption chiller without depending on the transportation distances. The simulation using AspenHYSYS also examined with same experimental condition. The experimental data showed good agreement with the simulation calculation. In this study, we examined the large-scale cooling power STA on simulation. The examination cooling powers were from 90 kW(25RT) to 3517 kW(1000RT). All cooling power achieved around COP 0.64 including pump power consumptions. In addition, we performed the dynamic simulation. As the results, there was no effect of pipeline size on the cooling capacities and mass flow rates. Furthermore, the stability time of the cooling capacities and mass flow rates were almost same regardless of the pipeline size and cooling capacity.
International conference proceedings, English

Experimental study on a three-bed two-stage adsorption refrigeration cycle using FAM-Z01 and Z05 adsorbents
Fumiya Takahashi; Koji Enoki; Atsushi Akisawa; Seiichi Kubokawa; Ken-Ichi Yoshie; Yasuo Yonezawa
Refrigeration Science and Technology, International Institute of Refrigeration, 431, 3850-3857, 2015, Peer-reviwed, Utilization of the wasted heat is effective to reduce primary energy consumption for mitigating global warming problem. Multistage adsorption refrigeration cycles can be a candidate to utilize low temperature heat sources less than 70 degrees Celsius for air-conditioning. However multistage adsorption cycles have a disadvantage of large volume of the facility due to many adsorption beds, for instance, conventional two-stage adsorption chillers have four-beds. This study proposes two-stage adsorption refrigeration cycle with three-beds which reduces one bed in comparison with conventional one. The operation of the cycle is different from that of conventional system as well. To estimate the performance of the proposed cycle using FAM Z01 and Z05. Static analyses on the Dühring diagram was employed to predict the cooling effect. Moreover, the performance of the cycle was investigated experimentally. The results verify that the cycle can work with the hot water of 60 degrees Celsius to produce chilled water of 12 degrees Celsius.
International conference proceedings, English

Effect of acoustic wave on enhancement of moisture adsorption rate of silica-gel
Kenichi Okubo; Soshi Matsuda; Yuki Ueda; Koji Enoki; Atsushi Akisawa
Refrigeration Science and Technology, International Institute of Refrigeration, 431, 637-644, 2015, Peer-reviwed, In this study, the enhancement of adsorption speed by acoustic wave is investigated to understand how the acoustic wave influences the adsorption performance. The experimental data were obtained to examine the effect of the equilibrium adsorption capacity under the acoustic field. The experimental results showed the adsorption speed with applied acoustic wave became higher than the case without acoustic wave although the equilibrium adsorption amount was the same. The effects of the velocity amplitude, pressure amplitude and frequency on adsorption speed were also examined. The adsorption speed was increased with increasing the velocity amplitude, and then the maximum adsorption speed attained 5.0 times as high as the case without acoustic wave when the velocity amplitude was 1.35 m/s. Based on the experimental data, a correlation expression was proposed, which is agreement to estimate the enhancement effect with the error of ±20% applicable to predict adsorption speed with acoustic wave. The correlation showed good.
International conference proceedings, English

Performance of wall-mounted non-tracking solar thermal collector with a parabolic mirror for concentration
Ryo Kashiide; Atsushi Akisawa; Koji Enoki
ISES Solar World Congress 2015, Conference Proceedings, International Solar Energy Society, 95, 880-889, 2015, Peer-reviwed, This study examined the performance of a solar collector with a linear parabolic mirror mounted vertically on walls. In order to simplify the system, it does not have sun tracking function and focuses on hot water supply only during winter which dominates annual hot water demand. The objectives are to design optimal shape of the parabolic concentrator by simulations and to demonstrate the heat recovery by experiments. The inclined angle and the focal length of the paraboloid are the design parameters. Since the parabolic mirror does not truck the sun, there should be the optimal setting of the design parameters which maximize the thermal energy collection during winter season. The simulation results indicated that the inclined angle of 25 ° and the focal length of 95 mm would be optimal, based on which the proposed collector was made and tested outdoors. The experimental results showed that the temperature of the hot water actually gained 45.8 degC in February, 2015.
International conference proceedings, English

A Three-Stage Adsorption Cycle with Three Silica-Gel Beds
WIRAJATI I GUSTI; AGUNG BAGUS; UMAIR MUHAMMAD; ENOKI KOJI; UEDA YUKI; AKISAWA ATSUSHI
日本冷凍空調学会論文集, Japan Society of Refrigerating and Air Conditioning Engineers, 31, 4, 423-429, 31 Dec. 2014, Peer-reviwed, This paper proposes a three-bed three-stage adsorption cycle with a new operational strategy. The cycle consists of three adsorber/desorber heat exchangers, one evaporator, and one condenser. The two beds on the low-pressure side operate in a re-heat cycle, and another bed on the high-pressure side operates in a conventional cycle. The objectives of the current study were to evaluate the cycle at a low heat source temperature such that it can be driven by solar or waste heat and to reduce the number of heat exchangers from six beds to three beds. A simulation model was developed, and the system behavior and its performance were predicted. The performance of the proposed cycle was compared with that of a conventional six-bed three-stage adsorption cycle. The simulation results showed that the proposed cycle with the new operational strategy could operate at low heat source temperature i.e., 45 °C, and offers approximately five times higher performance in terms of SCP than the conventional cycle. Consequently, the proposed cycle is effective for use of a low-grade heat source, even with three beds.
Scientific journal, English

Experimental Investigation of Solution Transportation Absorption Chiller in Steady/Non-steady State with Heat Transportation of 500 meters
Watanabe. F; Enoki. K; Marlinda; Tanaka. S; Ueda. Y; Akisawa. A; Takei. T; Araki. K
ISHPC2014-11, Mar. 2014, Peer-reviwed
International conference proceedings, English

Experimental Investigation of Heat Transportation Based on Absorption Mechanism over 200m Distance - Measured Performance of Solution Transportation Absorption Chiller
Akisawa. A; Watanabe. F; Marlinda; Enoki. K; Ueda. Y; Takei. T; Araki. K
SEES2014, Feb. 2014, Peer-reviwed
International conference proceedings, English

Experimental investigation of the effect of generator temperature on the performance of solution transportation absorption chiller
Koji Enoki; Fumi Watanabe; Marlinda; Seigo Tanaka; Yuki Ueda; Atsushi Akisawa; Toshitaka Takei; Kazumichi Araki
ACRA 2014 - Proceedings of the 7th Asian Conference on Refrigeration and Air Conditioning, 2014, Peer-reviwed, It is effective to recover wasted heat to reduce primary energy consumption. Because wasted heat sources are not necessarily located near heat demand, it is required to transport wasted heat from the source side to the demand side. The objective of this study is to examine the effect of generator temperature from 100 °C to 120 °C on the performance of solution transportation of ammonia-water solution, which is based on absorption refrigeration cycle. The experimental facility was employed to test the performance with 0 m, 200 m and 500m distance. The results indicate that the effect of the generator temperature and solution transportation distances showed no significant on the COP.
International conference proceedings, English

Flow Patterns of the Vapor-Liquid Two-Phase Flow in a Small Triangular Channel
松瀨 裕大; 中津留 拓哉; 榎木 光治; 森英夫; 仮屋圭史; 濱本芳徳
日本冷凍空調学会論文集 = Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers, 日本冷凍空調学会, 31, 1, 39-45, 2014, Peer-reviwed, In the present study, experiments were performed to observe vapor-liquid two-phase flow of a refrigerant R 410A in a horizontal small triangular channel with a glass tube and a high speed camera. The hydraulic diameter of glass tube was 0.82 mm. Based on the observation, flow patterns were classified into several flow regimes, and the effect of channel arrangement against gravity direction on the flow pattern was clarified. Furthermore, the effects of cross-sectional shape and flow direction were made clear by comparing with data of upward and downward flow in a triangular channel and horizontal flow in circular and rectangular channels previously obtained.
Scientific journal, Japanese

Pressure Drop of the Vapor-liquid Two-phase Flow in Small Tubes
ENOKI KOJI; MORI HIDEO; MIYATA KAZUSHI; KARIYA KEISHI; HAMAMOTO YOSHINORI
日本冷凍空調学会論文集, Japan Society of Refrigerating and Air Conditioning Engineers, 30, 4, 425-437, 31 Dec. 2013, Peer-reviwed, Experiments were carried out to examine the characteristics of the vapor-liquid two-phase pressure drop of a refrigerant R 410A flowing in horizontal copper circular and rectangular tubes, and their hydraulic diameters were 1.00 and 1.02 mm, respectively. Pressure drops were measured at mass velocities from 30 to 400 kg/(m²·s) and qualities from 0.05 to 0.9, and the saturation temperature of 10 °C under the adiabatic condition. Based on the observations of vapor-liquid two-phase flow patterns and the comparison with the data for vertically upward and downward flow in the circular and rectangular tubes previously obtained, the effects of the cross-sectional shape and flow direction on the characteristic of pressure drop were clarified. In addition, the measured pressure drops were compared with the existing correlations and their applicability were examined.
Scientific journal, Japanese

Boiling Heat Transfer and Pressure Drop of a Refrigerant R32 Flowing in a Small Horizontal Tube,
Matsuse. Y; Enoki. K; Mori. H; Kariya. K; Hamamoto. Y
141-146, Sep. 2013, Peer-reviwed
International conference proceedings, English

Boiling Heat Transfer and Pressure Drop of a Refrigerant Flowing Vertically Upward in Small Rectangular and Triangular Tubes
Koji Enoki; Kazushi Miyata; Hideo Mori; Keishi Kariya; Yoshinori Hamamoto
HEAT TRANSFER ENGINEERING, TAYLOR & FRANCIS INC, 34, 11-12, 966-975, Sep. 2013, Peer-reviwed, In the present study, experiments were performed to examine the characteristics of flow boiling heat transfer and pressure drop of a refrigerant R410A flowing vertically upward in small copper rectangular and triangular tubes with hydraulic diameters of 1.04 and 0.88mm, respectively, for the development of a high-performance heat exchanger using small tubes or minichannels for air-conditioning systems. Their characteristics were clarified by comparing the previous experimental data of the small circular tube (1.00mm internal diameter). In the rectangular and triangular tubes, the pressure drop was found to be slightly lower and the heat transfer was much better than in the circular tube.
Scientific journal, English

Flow Patterns of the Vapor-liquid Two-phase Flow in Small Tubes
榎木 光治; 森 英夫; 宮田 一司
日本冷凍空調学会論文集 = Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers, 日本冷凍空調学会, 30, 2, 155-167, 2013, Peer-reviwed, Experiments were carried out to observe the vapor-liquid two-phase flow of a refrigerant R 410A in small diameter glass tubes. The cross-sectional shapes of the glass tubes were circular, rectangular, and triangular, and their hydraulic diameters were 1.03, 0.97, and 0.82 mm, respectively. Flow directions were vertical upward, downward, and horizontal. Two-phase flow patterns were observed with a high-speed camera for mass velocity ranges from 30 to 400 kg/(m²·s) and qualities between 0.05 and 0.9 at the saturation temperature of 10 ℃ under adiabatic condition. The vapor and liquid superficial velocities were taken as 0.036 - 8.588 m/s, and 0.003 - 0.337 m/s, respectively. Based on the present observations, flow patterns were classified into several flow regimes, and the effects of the cross-sectional shape and flow direction on the flow pattern were clarified. Furthermore, conventional flow pattern maps for mini-channels were compared with the present observation results, and new flow pattern maps were proposed. In addition, the evaporation heat transfer through thin liquid film was confirmed through the observation with heating.
Scientific journal, Japanese

Boiling Heat Transfer and Pressure Drop of a Refrigerant Flowing in Small Horizontal Tubes, Proc. of the 3rd International Forum on Heat Transfer (IFHT2012)
Enoki. K; Mori. H; Miyata. K; Kariya. K; Hamamoto. Y
IFHT2012-193, Nov. 2012, Peer-reviwed
International conference proceedings, Japanese

Boiling Heat Transfer and Pressure Drop of a Refrigerant Flowing Vertically Upward in Small Rectangular and Triangular Tubes
Enoki K; Miyata. K; Mori. H; Kariya. K; Hamamoto. Y
PROCEEDINGS OF THE INTERNATIONAL SYMPOSIUM ON INNOVATIVE MATERIALS FOR PROCESSES IN ENERGY SYSTEMS 2010 (IMPRES2010): FOR FUEL CELLS, HEAT PUMPS AND SORPTION SYSTEMS, RESEARCH PUBLISHING SERVICES, 447-454, Dec. 2010, Peer-reviwed, In the present study, experiments were performed to examine the characteristics of flow boiling heat transfer and pressure drop of a refrigerant R410A flowing vertically upward in small copper rectangular and triangular tubes with the hydraulic diameter of 1.04 and 0.88 mm respectively for the development of a high-performance heat exchanger using small tubes or mini-channels for air-conditioning systems. Their characteristics were clarified by comparing the measurements with the data for the small circular tube of 1.00 mm I.D. previously obtained. In the rectangular and triangular tubes, the pressure drop was found to be slightly less and the heat transfer was much better than those in the circular tube.
International conference proceedings, English

Two-Phase Pressure Drop of a Refrigerant Flowing Vertically Downward in a Mini-Channel
MIYATA Kazushi; ENOKI Koji; MORI Hideo; HAMAMOTO Yoshinori
Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers, 日本冷凍空調学会, 26, 3, 335-346, 30 Sep. 2009, Peer-reviwed, Experiments were performed on two-phase pressure drop of a refrigerant R-410A flowing vertically downward in small copper circular tubes with 0.5-2.0 mm I.D., and small copper rectangular and triangular tubes with 1.04 and 0.88 mm inner hydraulic equivalent diameter, respectively, for the development of a high-performance heat exchanger using small tubes or multi-port extruded tubes for air conditioning systems.Pressure drops were measured and flow patterns were observed in the range of mass flux from 30 to 400 kg/(m²s)and quality from 0.1 to 0.9 at the saturation temperature of 10 °C. Characteristics of measured pressure drops were examined for different flow channel geometries. In high quality region or relatively high mass flux condition, the frictional pressure drop was reproduced well by the Lockhart-Martinelli correlation used together with a new correlation for Chisholm's parameter C as a function of hydraulic equivalent diameter. In low mass flux and low quality region, the frictional pressure drop was also reproduced well by multiplying the Chisholm two-phase multiplier factor by modified coefficient. In addition, flow pattern was observed with 0.5 and 2.0 mm I.D circular glass tubes. Slug flow and annular flow patterns were observed at lower and higher quality, respectively.
Scientific journal, Japanese

電通大から 世界最先端のエネルギー研究
榎木光治
Lead, Oct. 2023, 電気通信大学 環境報告書2023, 23-24, Japanese, Invited, Introduction research institution

電気通信大学カーボンニュートラル推進計画書 コラム執筆
榎木光治
電気通信大学, Jun. 2022, 電気通信大学カーボンニュートラル推進計画, 7, Japanese, Invited, Meeting report

Accuracy verification of low-cost CO2 concentration measuring devices for general use as a countermeasure against COVID-19
Yo Ishigaki; Koji Enoki; Shinji Yokogawa
AbstractWithin the context of the COVID-19 pandemic, CO2 sensors that measure ventilation conditions and thereby reduce the risk of airborne infection, are gaining increasing attention. We investigated and verified the accuracy of 12 relatively low-cost sensor models that retail for less than $45 and are advertised as infection control measures on a major e-commerce site. Our results indicate that 25% of the tested sensors can be used to identify trends in CO2 concentration, if correctly calibrated. However, 67% of sensors did not respond to the presence of CO2, which suggests that a type of pseudo-technique is used to display the CO2 concentration. We recommend that these sensors are not suitable for infection prevention purposes. We also found that all 67% of the sensors that did not respond to CO2 responded strongly to alcohol. Owing to the widespread use of alcohol in preventing the spread of infectious diseases, sensors that react to alcohol can display inaccurate values, resulting in inappropriate ventilation behavior. Therefore, we strongly recommended that these sensors not be used. Based on our results, we offer practical recommendations to the average consumer, who does not have special measuring equipment, on how to identify inaccurate CO2 sensors., Cold Spring Harbor Laboratory, 31 Jul. 2021, medRxiv, -, English, Report scientific journal

低GWP冷媒を採用した次世代冷凍空調技術の実用化評価に関する研究開発(第2報)2019年度の取り組みと成果—Development of Assessment Techniques for Next-Generation Refrigerant with Low GWP Values(2nd Report)Efforts and Outcomes of FY2019
宮岡 洋一; 西山 教之; ジャンネッティ ニコロ; 鄭 宗秀; 山口 誠一; 齋藤 潔; 榎木 光治; 井上 洋平; 清 雄一; 湊 明彦; 関口 通江
日本冷凍空調学会, 2020, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, Japanese, 2188-5397, 40022806181

波状形状を有する微細管内沸騰二相流の熱伝達および圧力損失特性に関する研究—Heat transfer and pressure drop characteristics of boiling two-phase flow in wavy mini-channel
小林 哲也; 御手洗 遥輝; 西田 耕作; 加藤 雅士; 赤田 郁朗; 榎木 光治
日本冷凍空調学会, 2020, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, Japanese, 2188-5397, 40022806394

焼結型高気孔率金属繊維多孔質体伝熱面における強制対流サブクール沸騰熱伝達に関する研究—Forced Convection Subcooled Boiling Heat Transfer with High Porosity Sintered Fiber on the Surface
大友 優甫; SANTIAGO-GALICIA Edgar; 福壽 陸; 織戸 賢治; 滝田 賢二; 幸 俊彦; 榎木 光治
日本冷凍空調学会, 2020, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, Japanese, 2188-5397, 40022805267

透過性と管摩擦係数を用いた焼結繊維状多孔質管に関する圧力損失特性の整理—Arrangement of pressure drop characteristics of sintered fibrous porous tube using permeability and tube friction coefficient
小林 拓都; 渡邊 廉; 大友 優甫; 上田 祐樹; 秋澤 淳; 榎木 光治
日本冷凍空調学会, 2020, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, Japanese, 2188-5397, 40022806238

Flow behavior and heat transfer characteristics near the rewetting front
梅原裕太郎; 山形圭祐; 榎木光治; 大川富雄
2020, 日本原子力学会春の年会予稿集(CD-ROM), 2020, 202002281007743083

Measurement of Adsorption Kinetics by Using Image Processing
2019, English, 2188-5397, 40022802563

低GWP冷媒を採用した次世代冷凍空調技術の実用化評価に関する研究開発(第1報)次世代低GWP冷媒のサイクル性能評価研究の概要と2018年度の取り組み—Development of Assessment Techniques for Next-Generation Refrigerant with Low GWP Values(1st Report)Outline of the Research of Cycle Performance Evaluation for Next-Generation Refrigerant with Low GWP and the Approach in 2018
宮岡 洋一; ジャンネッティ ニコロ; 山口 誠一; 齋藤 潔; 榎木 光治; 井上 洋平; 清 雄一; 湊 明彦; 関口 通江
日本冷凍空調学会, 2019, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, Japanese, 2188-5397, 40022801443

繊維状金属焼結管に関する伝熱および圧力損失の実験的解明—Method for improving air-side heat transfer using metal sintered body
渡邊 廉; 榎木 光治; 大友 優甫; 小林 拓都; 大川 富雄; 秋澤 淳; 上田 祐樹
日本冷凍空調学会, 2019, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, Japanese, 2188-5397, 40022801664

Heat transfer improvement in heat exchanger for thermoacoustic engine by sintered porous pipes
OTOMO Yusuke; ENOKI Koji; KOBAYASHI Takuto; UEDA Yuki; AKISAWA Atsushi; KAWASAKI Jumpei; OKAWA Tomio
Recently thermoacoustic engine is being used to recover latent and sensible heat. However, the heat exchanger which is loaded by thermoacoustic engine has low performance because of large thermal resistance of the gas side. The purpose of this study is improving heat exchanger equipped with sintered fiber metal porous materials into the pipes in order to enhance the heat flux. Porous materials have the characteristic of mixing the fluid in contact and expanding heat transfer area. In addition, these heat pipes have a less contact thermal resistance because of the sintered porous materials into tube wall. Conducted experiments to measure heat exchange for each pipes show that porous pipes have between 1.5 times and 2 times better heat exchange performance than conventional ones under the condition Reynolds number Re = 4500. Furthermore, heat exchanger using sintered fiber metal porous materials increase until 10 times the heat transfer rate in comparison with the conventional heat exchangers., The Japan Society of Mechanical Engineers, 2019, The Proceedings of the National Symposium on Power and Energy Systems, 2019.24, E111, Japanese, 2424-2950, 130007773973

Experiments on Lift-off Bubble Size Distribution in Subcooled Flow Boiling
OKAWA Tomio; KAIHO Kazuhiro; LI Hongji; OHORI Koki; SAKAMOTO Shintaro; ENOKI Koji
Bubble size is an important fundamental parameter in subcooled flow boiling. In this study, bubble behavior in subcooled flow boiling was visualized to confirm that mean bubble size is considerably different between different nucleation sites. Empirical correlations were developed using the present experimental data for the distribution of mean bubble size and the distribution of the size of bubbles produced in each site. Observation of the nucleation sites using a microscope revealed that tower-shaped structure is present at the nucleation sites where small bubbles are produced whilst no such structure was found at the sites where large bubbles are produced. This result suggest that bubble size is dependent significantly on the nucleation site geometry., The Japan Society of Mechanical Engineers, 2019, The Proceedings of the National Symposium on Power and Energy Systems, 2019.24, A215, Japanese, 2424-2950, 130007773841

Study of Thermo-acoustic Engine to utilize cold energy of LNG
AKISAWA Atsushi; UEDA Yuki; IKEGAMI Takashi; KAWASAKI Junpei; ENOKI Koji
This study focuses on a thermo-acoustic engine which utilizes cold energy of LNG. The authors developed an experimental engine driven with liquified N₂, which successfully generated acoustic power more than 100W. The objective of this study is to find an application of thermo-acoustic engine combined with conventional propane cycle for LNG power generation. Because thermo-acoustic engine performs better in cryogenic temperature range, it is suggested to allocate thermo-acoustic engines prior to the propane cycle. An optimization was employed to design thermo-acoustic engine for various cold side temperature of the regenerator. The results of the cycle simulation showed that the temperature of -120 degC would be the best setting to maximize the total power generation of both the thermo-acoustic engines and the propane cycle, which increases the output by 15%., The Japan Society of Mechanical Engineers, 2019, The Proceedings of the National Symposium on Power and Energy Systems, 2019.24, E112, Japanese, 2424-2950, 130007773967

Development for a thermoacoustic power system driven by cold exergy
UEDA Yuki; KAWASAKI Jyunpei; HONZAWA Takahumi; KATO Takuma; AKISAWA Atsushi; IKEGAMI Takashi; ENOKI Kohji
The thermoacoustic engine that can be driven by cold exergy has been designed and constructed. It is composed of a looped tube, a straight tube, two heat exchangers, a regenerator, and a tank. The regenerator is sandwiched by the heat exchangers and is located in the looped tube. When the temperature ratio of the heat exchangers exceeds 1.7, the gas inside the engine spontaneously oscillates. The amplitude of the oscillation increases with increasing the temperature ratio, and the output power of the engine reaches 190 W., The Japan Society of Mechanical Engineers, 2018, The Proceedings of the National Symposium on Power and Energy Systems, 2018.23, C215, Japanese, 2424-2950, 130007550752

Direct Measurement of Heat Transfer Coefficient Distribution around the Rewetting Front during High Temperature Surface Liquid Cooling
Yamagata Keisuke; Enoki Koji; Okawa Tomio
In order to elucidate the rewetting phenomenon in detail, it is important to know the distribution of the heat transfer coefficient in the vicinity of the rewetting front. However, the distribution of the heat transfer coefficient is not yet known in detail, and there are few data that directly measured its distribution. In this study, the temperature distribution of the wall surface temperature when the liquid film flows down was measured using a high-speed infrared camera, and the distribution of heat transfer coefficient was directly measured from the temperature data. We tried to experimentally determine the dominant factors influencing the heat transfer coefficient by changing experiment parameters., The Japan Society of Mechanical Engineers, 2018, The Proceedings of the Thermal Engineering Conference, 2018, 0039, Japanese, 2424-290X, 130007637556

Effect of Various Parameters on Boiling Heat Transfer of Nanofluids
Watanabe Yosuke; Enoki Koji; Okawa Tomio
In nucleate boiling of nanofluids, heat transfer coefficient and CHF change due to nanoparticle layer formation on the heated surface. It is considered that the nanoparticle layer causes the changes of wettability and roughness of the heated surface. In this study, influences of the total mass of nanoparticle layer and properties of the heated surface were experimentally investigated parametrically changing the nanoparticle concentration and the heat flux during nanoparticle layer formation. The heated surface material was copper and the material of nanoparticles was titanium-dioxide, alumina, and silica. The influencing parameter for the total mass of the nanoparticle layer was elucidated experimentally., The Japan Society of Mechanical Engineers, 2018, The Proceedings of the Thermal Engineering Conference, 2018, 0037, Japanese, 2424-290X, 130007637557

Study on Thermal Performance of Nanofluid in Heat Pipe
Menglei Wang; Enoki Koji; Okawa Tomio
In this research, silicon dioxide/DI water nanofluid was used as the working fluid in a cylindrical heat pipe to experimentally investigate its effect to enhance the heat transfer performance. In the experiment, the one end of the heat pipe was heated using a nichrome wire heater and the other end was cooled using a fan. In addition, effects of pre-coating of the screen mesh and the inside wall of the heat pipe with nanoparticles on heat transfer performance were explored. The experimental results showed that in comparison with the normal heat pipe BBW (bare tube / bare mesh / pure water), the thermal resistance of BNW (bare tube / nanoparticle-coated mesh / pure water) is reduced by 2-8% for the input power of 3-9W. When the power was increased to 9-25W, however, the thermal resistances of NXW (nanoparticle-coated tube / no mesh / pure water) and NBW (nanoparticle-coated tube / bare mesh / pure water) decreased 13-32%. This corresponded to the heat transfer enhancement of 15-40%., The Japan Society of Mechanical Engineers, 2018, The Proceedings of the Thermal Engineering Conference, 2018, 0029, Japanese, 2424-290X, 130007637518

Two-phase Flow Distribution at Wider Flow Range within the Vertical Header of Microchannel Heat Exchanger: マイクロチャンネル熱交換器の垂直ヘッダーにおける広範囲流量分配特性
2017, English, 2188-5397, 40021356891, BB18860123

サブクール沸騰熱伝達におけるポーラス伝熱面を用いた伝熱面拡大と流体の攪拌の影響—The effects of enhancement porous surface area and roily coolant in forced convection subcooled boiling heat transfer
大箸 淳記; Edgar SANTIAGO-GALICIA; 熊取 弘祐; 榎木 光治; 大川 富雄
日本冷凍空調学会, 2017, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, Japanese, 2188-5397, 40021357557, BB18860123

報告記 第9回若手産学技術者ワークショップ : 産業界と大学関係者の交流の場
榎木 光治; 志田 京子; 古谷野 赳弘; 齊藤 正士
日本冷凍空調学会, Jan. 2017, 冷凍 = Refrigeration, 92, 1071, 63-66, Japanese, 0034-3714, 40021071710, AN00254367

Two-phase flow distribution of R410A within the vertical header of a microchannel heat exchanger
REDO Mark Anthony; GIANNETTI Niccolo; JEONG Jongsoo; ENOKI Koji; OTA Ikuhide; SAITO Kiyoshi; KIM Hyunyoung
With an ultimate goal of enhancing the flow distribution within a microchannel heat exchanger, an experimental apparatus was designed and constructed. This study presented an initial evaluation and investigation of R410A distribution with mass flowrate of 40, 60, 80 kg/h or mass flux of 120, 180, 240 kg/m²s. The inlet vapor quality before the header was varied at 0.1, 0.2 and 0.6. The inlet flow entered at the bottom with a normal location towards the vertical header. 20 horizontal parallel flat tubes having microchannel holes were protruded half-width of the header where the flow was distributed. Individual pressure drop and flowrate were measured. Corresponding inlet vapor quality for each was calculated. Visualization was conducted for the observation of the flow behavior at the vertical header. Increase on the liquid level at higher mass flux and more homogeneous two-phase flow at lower quality were observed within the header, which yielded better distribution., The Japan Society of Mechanical Engineers, 2017, The Proceedings of the Symposium on Environmental Engineering, 2017.27, 427, Japanese, 2424-2969, 130006320050

The Characteristics of Vapor-liquid Two-phase Flow in Mini-Channels
NAKAMURA Taichi; ONO Masaharu; ENOKI Koji; OKAWA Tomio; KATO Masashi; NISHIDA Kousaku
The Japan Society of Mechanical Engineers, 2017, The Proceedings of Conference of Kanto Branch, 2017.23, 413, Japanese, 2424-2691, 130007078922

Relationship with heat flux and noise and pressure fluctuation in porous-micro-channel
HIRATA Ryo; OHASHI Junki; ENOKI Koji; OKAWA Tomio
The Japan Society of Mechanical Engineers, 2017, The Proceedings of Conference of Kanto Branch, 2017.23, 410, Japanese, 2424-2691, 130007078926

The detachment of nanoparticle layer on boiling heat-transfer of nanofluids
WATANABE Yosuke; ENOKI Koji; OKAWA Tomio
The Japan Society of Mechanical Engineers, 2017, The Proceedings of Conference of Kanto Branch, 2017.23, 405, Japanese, 2424-2691, 130007078189

A study on secondary droplet production during drop impingement onto a thin liquid film
KITABAYASHI Sota; ENOKI Koji; OKAWA Tomio
The Japan Society of Mechanical Engineers, 2017, The Proceedings of Conference of Kanto Branch, 2017.23, 302, Japanese, 2424-2691, 130007078153

ナノ流体による高温物体の超高速冷却
梅原裕太郎; 榎木光治; 大川富雄
2017, 日本原子力学会春の年会予稿集(CD-ROM), 2017, 201702229695805895

ナノ流体を用いた高温物体の伝熱特性の解明
梅原裕太郎; 榎木光治; LIU Wei; 大川富雄
2017, 日本原子力学会秋の大会予稿集(CD-ROM), 2017, 201702238113018960

Changes in quench characteristics of high temperature objects by nanofluid
梅原裕太郎; 榎木光治; 大川富雄
2017, 混相流シンポジウム講演論文集(CD-ROM), 2017, 201702290843481306

ナノ流体中における高温物体のクエンチ特性
梅原裕太郎; 榎木光治; 大川富雄; 緒方隆志
2017, 日本機械学会関東支部総会・講演会講演論文集(CD-ROM), 23rd, 2424-2691, 201702272121947869

Vapor - liquid Two - phase Flow Patterns and the Effects of Oscillation of a Refrigerant Flowing in Small Horizontal Rectangular Tube
OHNO Masaharu; ENOKI Koji; NAGAYAMA Kunihiro; AKISAWA Atsushi; Okawa Tomio; MIYATA Kazushi; MORI Hideo
In this study, we performed to observe horizontal vapor-liquid two phase flow of refrigerant R 134a in the rectangular glass channel which hydraulic diameter is 0.84 mm. The test glass tube was added the oscillation to the gravity direction for slug and stratified flow under low mass flux and heat flux. When the channel was oscillated of certain frequency and amplitude, the liquid of the corner part of rectangular channel waved up and down. In slug flow, dry surface of central was supplied the liquid by the oscillation and was formed the thin liquid. In stratified flow, dry surface of top was supplied the liquid and flow pattern changed to annular from stratified flow. The oscillation influences were investigated in a quantitative way., The Japan Society of Mechanical Engineers, 2016, The Proceedings of the National Symposium on Power and Energy Systems, 2016.21, A212, Japanese, 2424-2950, 130007143420

Effects of bubble lift-off conditions on numerical analysis of subcooled flow boiling
Sakamoto Shintaro; Kaiho Kazuhiro; Enoki Koji; Okawa Tomio
Numerical simulation of subcooled flow boiling in a vertical rectangular duct was carried out using a one-way bubble tracking method; this method treats each bubble as an individual particle. Although a bubble behavior after lifting off the heated surface depends on the bubble size and velocity at lift-off, these lift-off conditions are not taken into consideration in existing subcooled flow boiling models. In the present simulation, the distributions of lift-off velocity and bubble size were considered. It was demonstrated that the calculated void fraction in subcooled flow boiling is influenced significantly by the lift-off conditions., The Japan Society of Mechanical Engineers, 2016, The Proceedings of the Thermal Engineering Conference, 2016, C221, Japanese, 2424-290X, 130007135584

Measurements of pressure fluctuation and sound production in flow boiling in a porous-micro-channel
Ohashi Junki; Hirata Ryo; Enoki Koji; Okawa Tomio
Experiments were carried out to investigate the characteristics of high-heat-flux heat removal using a porousmicro-channel under the condition of high liquid subcooling and high mass flux. The working fluid was water and the main experimental parameters were insertion of porous plate and channel size. It was shown that fluctuation of heating surface temperature and flow oscillation are mitigated if the porous plate is placed in the flow channel. Another finding was that the sound production in the flow channel under the high heat flux condition is also mitigated in the porous-micro-channel. These results indicate that the porous-micro-channel is advantageous for the high-heat-flux heat removal from high-power-density devices., The Japan Society of Mechanical Engineers, 2016, The Proceedings of the Thermal Engineering Conference, 2016, I112, Japanese, 2424-290X, 130007136346

An experimental study on the secondary droplets production during the drop impingement onto a liquid film
ENOKI Koji; Matsuse Kohei; Okawa Tomio
Experiments were performed to explore the conditions for the onset of secondary droplet formation during single drop impact onto a liquid film(splashing). It was found that there were two types of splashing: the prompt splash and the late splash. In the prompt splash, small droplets were scattered with high velocity immediately after the impact. Whilst, in the late splash, larger droplets of lower velocity were produced after the development of liquid crown. The condition for the onset of splashing was expressed using the two dimensionless numbers: the Weber number, the Ohnesorge number. The correlations were given separately for the prompt and late splashes. Moreover new correlations were developed about prediction of the secondary droplet diameter and velocity., The Japan Society of Mechanical Engineers, 2016, The Proceedings of the National Symposium on Power and Energy Systems, 2016.21, A213, Japanese, 2424-2950, 130007143418

3つの吸着反応器を用いる二段型吸着冷凍サイクルの性能実証—Experimental study on a three-bed two-stage adsorption refrigeration cycle
高橋 郁也; 榎木 光治; 秋澤 淳
[日本冷凍空調学会], Apr. 2015, 空気調和・冷凍連合講演会講演論文集 Proceedings of Japanese Joint Conference on Air-conditioning and Refrigeration (Tokyo), 49, 4p, Japanese, 2424-0540, 40020722219, AA12206279

微細矩形流路内における気液二相流動様相および振動の及ぼす影響—Vapor-liquid Two-phase Flow Patterns and Effects of Oscillation in Small Rectangular Tube
長山 国弘; 榎木 光治; 大野 正晴
日本冷凍空調学会, 2015, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, Japanese, 2188-5397, 40020754342, BB18860123

B213 Visualization Analysis of the Boiling Characteristics during the Water Subcooled Flow Boiling in Low Pressure
Kaiho Kazuhiro; Tuchie Kenta; Miyano Naoki; Enoki Koji; Okawa Tomio
In the subcooled flow boiling, bubble size is important in calculating the vaporization rate accurately. On the surface, a number of bubbles that are different size are generated. If the bubble size is assumed to be uniform, a serious error may be caused in the numerical simulation. In this study, considering bubble size distribution, the bubble size are predicted by the gamma distribution. It was demonstrated that the gamma distribution satisfactorily describes the bubble distribution data. Furthermore, correlations were developed for the dimensionless bubble size and shape parameter to enable accurate prediction of them in the subcooled flow boiling., The Japan Society of Mechanical Engineers, 2015, The Proceedings of the Thermal Engineering Conference, 2015, _B213-1_-_B213-2_, Japanese, 2424-290X, 110010045406

Effect of Transportation Pipe on Controllability and Refrigerant and Solution Receiver of Solution Transportation Absorption Chiller Using NH3-H2O: Dynamic Simulation
WATANABE Fumi; TANAKA Seigo; ENOKI Kouji; AKISAWA Atsushi; TAKEI Toshitaka
The Solution Transportation Absorption chiller (STA) can transport the thermal energy at ambient temperature due to conversion of the thermal energy into concentration difference of the refrigerant and the solutions. This study, on the assumption that a large scale STA as the heat transportation distance is 10000 m and the cooling output is 3517 kW, simulates the dynamic behaviors decreased to 20 % of the cooling output and then analyze the effect of control ability and the refrigerant receiver on the transport pipe. The behaviors of the cooling output are almost the same tracking as those of both 1 m and 10000 m pipes. Lager volume of the pipe will results in more use of refrigerant in the refrigerant receiver because the increased amount of refrigerant mass in the strong solution is used by refrigerant in the refrigerant receiver. Therefore, STA can be controlled for the cooling output by the conventional control method. On the other hand, the receivers volume or filling amount of the refrigerant are required to be designed according to the pipe volume., Japan Society of Refrigerating and Air Conditioning Engineers, 2015, Transactions of the Japan Society of Refrigerating and Air Conditioning Engineers, 32, 3, 353-362, Japanese, 1344-4905, 2185-789X, 130005266041, AA11125910

411 Performance analysis of solution transportation absorption chiller with dual evaporators
TANAKA Seigo; AKISAWA Atsushi; ENOKI Kohji; WATANABE Fumi
The authors have examined heat transportation based on ammonia absorption cycle named STA. STA recovers discharged heat and converts it into cooling. New type of STA was proposed in this study, which incorporates two evaporators to provide cooling at different temperature simultaneously. The objectives of this study are to investigate the static performance such as cooling output and COP as well as to observe the interaction between two refrigeration cycles of the proposed STA by non- steady state simulation. The static cycle simulation reveals that cooling output of each evaporator is proportional to refrigerant mass flow. The result of dynamic simulation shows that the change of cooling load in one side affects the temperature behavior of the other side to some extent. Because the effect seems small, it implies that the two evaporators can be controlled separately as the conventional way., The Japan Society of Mechanical Engineers, 2015, The Proceedings of the Symposium on Environmental Engineering, 2015.25, 171-174, Japanese, 2424-2969, 110010051540

403 Performance measurement of non-tracking-type solar thermal collector with parabolic mirror for concentration
KASHIIDE Ryo; AKISAWA Atsushi; ENOKI Koji
This study examined the performance of a solar collector with a parabolic mirror mounted vertically on walls. In order to simplify the system, in does not have sun tracking function and focuses on hot water supply only during winter which dominates heat demand. The objectives are to design the parabolic concentrator by simulations and to demonstrate the heat recovery by experiments. The inclined angle and the focal length of the paraboloid are the design parameters. Since the parabolic mirror does not truck the sun, there should be the optimal settings of the design parameters which maximize the thermal energy collection during winter season. The simulation results indicated that the inclined angle of 25 ° and the focal length of 95 mm would be optimal, based on which the proposed collector was made and tested outdoors. The experimental results showed that the temperature of the hot water actually gained 45.8 degC. In contrast, the same collector without parabolic mirror attained only 30.9 degC of the hot water., The Japan Society of Mechanical Engineers, 2015, The Proceedings of the Symposium on Environmental Engineering, 2015.25, 147-150, Japanese, 2424-2969, 110010051533

20814 Analysis of Heat Transfer in Adsorption Bed combined with Compound Parabolic Concentrator
DWIPUTR Achmad Faisal; UMAIR Muhammad; ENOKI Koji; UEDA Yuki; AKISAWA Atsushi
Simulation study of heat transfer in an adsorption bed with CPC-shaped solar collector was carried out. The objectives of this study were to make a simulation model and verify it with experimental results, and to find the effect of fin pitch in heat transferring. The solar heat distribution on CPC receiver was obtained by ray tracing on CPC geometry. It was found that the simulation results had good agreement with experimental data. The heat transfer decreased when the fin pitch was increased, and increased when fin pitch was decreased. And with regard to fin optimal interval, the result concludes that for a given area of fin, the heat transfer is optimum when fins are placed evenly along the bed. This simulation model will help to optimize the experimental model to improve the system performance., The Japan Society of Mechanical Engineers, 14 Mar. 2014, 日本機械学会関東支部総会講演会講演論文集, 2014, 20, "20814-1"-"20814-2", Japanese, 110009949464, AA11902161

音波の速度振幅と圧力振幅が湿分吸着促進に与える影響の評価—Enhancement of Adsorption Rate by Sound Wave in Terms of Velocity Amplitude and Pressure Amplitude
大久保 賢一; 上田 祐樹; 榎木 光治
日本冷凍空調学会, 2014, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, Japanese, 2188-5397, 40020711631, BB18860123

太陽熱利用による吸着冷凍機とデシカント空調機の連成システムの運転実績—Performance of the coupled system using solar thermal energy between adsorption refrigerator and desiccant air conditioner
大原 裕史; 山口 大貴; 榎木 光治
日本冷凍空調学会, 2014, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, Japanese, 2188-5397, 40020713244, BB18860123

溶液輸送型吸収冷凍機の200m熱輸送実験に基づくシミュレーションモデルの開発—Development of Simulation Model Based on Experiments of Solution Transportation Absorption Chiller with 200m
田中 成吾; 渡辺 史; 榎木 光治
日本冷凍空調学会, 2014, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, Japanese, 2188-5397, 40020711691, BB18860123

大規模化された溶液輸送型吸収冷凍機の長距離熱輸送における動的解析—Dynamic simulation of large-scale solution transportation absorption chiller with long distance
榎木 光治; 田中 成吾; 渡辺 史
日本冷凍空調学会, 2014, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, Japanese, 2188-5397, 40020711706, BB18860123

放物面鏡を用いた非追尾型集熱器の最適設置形態および性能評価—Optimum installation form and performance evaluation of non-tracking-type heat collector with a parabolic mirror
樫出 亮; 上田 祐樹; 榎木 光治
日本太陽エネルギー学会, 2014, 太陽/風力エネルギー講演論文集 = Proceedings of JSES/JWEA Joint Conference / 日本太陽エネルギー学会 編, 151-154, Japanese, 40020274689, AN10465992

Three-Stage Adsorption Cycle with Three-Adsorption Beds
WIRAJATI I Gusti Agung Bagus; UMAIR Muhammad; ENOKI Koji
日本冷凍空調学会, 2014, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, A222-1-4, English, 2188-5397, 40020712523, BB18860123

Flow patterns of the vapor-liquid two-phase flow in a small triangular channel
松瀨 裕大; 中津留 拓哉; 榎木 光治
日本冷凍空調学会, 2013, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, 319-322, Japanese, 2188-5397, 40020588591, BB18860123

Flow patterns of the vapor-liquid two-phase flow in small tubes
榎木 光治; 森 英夫; 宮田 一司
日本冷凍空調学会, 2012, 日本冷凍空調学会年次大会講演論文集 Proceedings of the JSRAE Annual Conference, A231-1-4, Japanese, 2188-5397, 40020583975, BB18860123

807 Heat transfer regimes of flow boiling in vertical small tube
ENOKI Koji; MIYATA Kazushi; OTUJI Daisuke; MORI Hideo; HAMAMOTO Yoshinori
The Japan Society of Mechanical Engineers, 15 Mar. 2010, 日本機械学会九州支部講演論文集, 2010, 63, 289-290, Japanese, 110008745400, AN0036066X

Observation of the vapor-liquid two-phase flow patterns in a small diameter tube
Enoki Koji; Miyata Kazushi; Mori Hideo; Hamamoto Yoshinori
気液二相状態の冷媒が内径1mmの微細円管内を垂直上向きおよび下向きに流れる際の流動様相を，ガラス管と高速度カメラを用いて観察した．その結果，大径管の場合と同様に，クオリティの増加とともにスラグ流から環状流への遷移が見られ，また，下降流の方が，上昇流に比べて低いクオリティでも環状流に遷移することが確認された．さらに，管壁に沿って流れる液膜の挙動を，流動方向や流速ごとに詳細に観察し，既に明らかにしている微細管内垂直流の摩擦圧力損失および沸騰熱伝達の特性と関連付けて検討した．, The Heat Transfer Society of Japan, 2010, Proceedings of National Heat Transfer Symposium, 2010, 104-104, Japanese, 130004648375

Boiling Heat Transfer and Pressure Drop of a Refrigerant Flowing Vertically Upward in a Small Rectangular Tube
Miyata Kazushi; Enoki Koji; Mori Hideo; Hamamoto Yoshinori
本研究では，微細流路を用いた空調機用高性能熱交換器の開発のために，水力等価直径1.04mmの矩形流路断面を有する銅製細管内を冷媒R410Aが垂直上向きに流れる際の沸騰熱伝達と圧力損失の実験を行った．冷媒の飽和温度は10℃である．局所熱伝達率は，質量速度30-400 kg/(m²・s)，熱流束1-24 kW/m²，クオリティ0.05-1.0の領域で，また圧力損失は，質量速度30-400 kg/(m²・s)，クオリティ0.1-0.9の範囲で測定した．また，得られたデータを，すでに得ている矩形管内下降流のデータと比較した．, The Heat Transfer Society of Japan, 2009, Proceedings of National Heat Transfer Symposium, 2009, 183-183, Japanese, 130005018756

2024年度版 社会科資料集５年
Others, 社会科資料集へ写真提供, 118, 5, 株式会社日本標準, 2024, Peer-reviwed

熱駆動サイクル技術の基礎と応用 ～ カーボンニュートラル社会に貢献する冷凍空調技術 ～
秋澤淳; 宮崎隆彦; 榎木光治
Scholarly book, Japanese, Supervisor, 316, 日本工業出版, Mar. 2023, 9784819035057

連結流路を用いた並列多孔微細流路における偏流・逆流抑制に伴う性能向上に関する 研究
榎木光治
Public discourse, Japanese, 日本冷凍空調学会調査研究プロジェクト 「カーボンニュートラルに向けた先進熱交換技術に関する調査研究」, Invited
15 Sep. 2023
15 Sep. 2023- 15 Sep. 2023

おばね雪発電
榎木光治
Public discourse, ｢おばね発電｣エネルギー棟施設見学 & 講習会, Invited
02 Jun. 2023
02 Jun. 2023

積雪発電の研究開発の概要とエネルギーの地産地消について
榎木 光治
Public discourse, 社会福祉法人大石田町社会福祉協議会 除雪体制づくりプロジェクト会議, Invited
01 Jun. 2023
01 Jun. 2023

積雪発電の研究開発の概要とエネルギーの地産地消について
榎木光治
Keynote oral presentation, Japanese, 令和４年度最上地域エネルギー戦略推進協議会講演会, Invited, 最上地域エネルギー戦略推進協議会, 山形県新庄市, Domestic conference
22 Feb. 2023

Optimization of refrigerant circuitry within finned-tube heat exchangers using thermo-genetic path-algorithm
N. Giannetti; J.C. Garcia; R.J. Varela; Y. Sei; K. Enoki; J. Jeong; K. Saito
Oral presentation, English, JSRAE Annual Conference 2022, Domestic conference, with international co-author(s)
Sep. 2022

低レイノルズ数円管内乱流における進行波状吹出し・吸込み制御モードの熱伝達促進効果の比較
三藤春輝; 守裕也; 宮嵜武; 榎木光治
Oral presentation, Japanese, 第35回数値流体シンポジウム, 日本流体力学学会, Domestic conference
Dec. 2021

Adiabatic and Boiling Flow Patterns of the Vapor-liquid Two-phase Flow in Small Channels
Koji Enoki; Kazushi Miyata; Yoshinori Hamamoto; Hideo Mori
Oral presentation, Japanese, 日本機械学会 熱工学カンファレンス2021, 日本機械学会, Domestic conference
09 Oct. 2021

Visualization of something near to you about heat and fluid for elementary, middle and high school students
Koji Enoki
Oral presentation, Japanese, 日本機械学会 熱工学カンファレンス2021, 日本機械学会, Domestic conference
09 Oct. 2021

Experimental and numerical investigation into the heat transfer and pressure drop performance of sintered high porosity media
Koji Enoki
Keynote oral presentation, English, The 7th International Conference on Industrial, Mechanical, Electrical and Chemical Engineering (ICIMECE 2021), Invited, Sebelas Maret University,RISTEKDIKTI, Sebelas Maret University, Indonesia（Online）, https://icimece2021.ft.uns.ac.id/, International conference
05 Oct. 2021

並列波状微細流路熱交換器の入口ヘッダー形状変化よる偏流の抑制に関する研究
御手洗 遥輝; 安喰 康太; 榎木 光治; 西田 耕作; 赤田 郁朗
Oral presentation, Japanese, 2021年度日本冷凍空調学会 年次大会, 日本冷凍空調学会, 東京工業大学（リモート開催）, Domestic conference
10 Sep. 2021

混合冷媒の熱伝達特性と伝熱面における物性との関係に関する研究
福壽 陸; 菅野 樹; 榎木 光治; 齋藤 潔
Oral presentation, Japanese, 2021年度日本冷凍空調学会 年次大会, 日本冷凍空調学会, 東京工業大学（リモート開催）, Domestic conference
10 Sep. 2021

The Effect of the Copper Oxidation on the Subcooled Flow Boiling Heat Transfer
サンティアゴガリシア エドガー; 大友 優甫; 榎木 光治
Oral presentation, English, 2021年度日本冷凍空調学会 年次大会, 日本冷凍空調学会, 東京工業大学（リモート開催）, Domestic conference
10 Sep. 2021

繊維状金属焼結多孔質管におけるガス側の熱伝達向上法と圧力損失特性に関する実験的研究
渡邊 廉; 樫 祐人; 榎木 光治; 織戸 賢治; マテリアル株式会社; 滝田 賢二; 幸 俊彦
Oral presentation, Japanese, 2021年度日本冷凍空調学会 年次大会, 日本冷凍空調学会, 東京工業大学（リモート開催）, Domestic conference
10 Sep. 2021

Development of Assessment Techniques for Next-Generation Refrigerants with Low GWP Values Fourth report: Efforts and outcomes on heat exchanger optimization in FY 2020
Giannetti Niccolo; Garcia John Carlo; Varela Richard Jayson; 清 雄一; 榎木 光治; 鄭 宗秀; 齋藤 潔
Oral presentation, Japanese, 2021年度日本冷凍空調学会 年次大会, 日本冷凍空調学会, 東京工業大学（リモート開催）, Domestic conference
08 Sep. 2021

管内沸騰熱伝達率の深層学習への応用方法と注意点
Yuichi Sei; Koji Enoki
Invited oral presentation, Japanese, 混相流レクチャーシリーズ46, Invited, 日本混相流学会, Domestic conference
04 Jun. 2021

Good collaborative studies developed from our close relationship by both official and private activities
Koji Enoki
Nominated symposium, English, ［UNS］UEC EDU FEST 2021, Invited, Sebelas Maret University, Indonesia (Online), 本学の協定校であるスブラス・マレット大学(インドネシア）では、創立45周年記念に際し、本学や日本文化を紹介するOne day e-Seminar［UNS］UEC EDU FEST 2021 を3月13日（土）にオンライン（ZOOM）で開催いたします。, International conference
13 Mar. 2021

人工知能AIの基礎および相変化熱伝達予測への⼈⼯知能の適⽤について
Koji Enoki
Invited oral presentation, Japanese, 2020年度 パナソニック総合技術シンポジウム（第38回）, Invited, Panasonic Corporation, Domestic conference
Nov. 2020

Correlation of Pressure Drop in the Sintered Fibrous Porous Tube with Permeability and Friction Coefficient
Koji Enoki
Invited oral presentation, English, ICE-SEAM 2020, Invited, RISTEKDIKTI, Indonesia, https://icimece2020.ft.uns.ac.id/, International conference
Oct. 2020

TBD
Koji Enoki
Invited oral presentation, English, ICE-SEAM 2020, Invited, RISTEKDIKTI, Indonesia, https://icimece2020.ft.uns.ac.id/, International conference
15 Sep. 2020

Heat Transfer of Natural Refrigerant
Koji Enoki
Invited oral presentation, Japanese, 日本冷凍空調学会，自然冷媒システム調査研究プロジェクト, Invited, 大阪, Domestic conference
20 Jul. 2020

管内沸騰熱伝達率の深層学習への応用方法と注意点
Koji Enoki; Yuichi Sei
Keynote oral presentation, Japanese, Japan Society of Refrigerating and Air Conditioning Engineers, Invited, The Japanese Society for Multiphase Flow, Tokyo, http://www.jsmf.gr.jp/index.shtml#event, Domestic conference
01 Jun. 2020

相変化熱伝達予測への人工知能の適用について ～ 人工知能の基礎と特性を理解した上での利用方法～
Koji Enoki
Invited oral presentation, Japanese, 日本機械学会 相変化界面研究会, Invited, Domestic conference
27 May 2020

AI技術の活用事例～管内沸騰熱伝達率の整理～
Koji Enoki; Yuichi Sei
Public discourse, Japanese, Japan Society of Refrigerating and Air Conditioning Engineers, Invited, Japan Society of Refrigerating and Air Conditioning Engineers, Fukuoka, https://www.jsrae.or.jp/info/f-200207_tech_semi.html, Domestic conference
07 Feb. 2020

Lecturer on Thermal Fluid Engineering
Koji Enoki
Public discourse, English, Sebelas Maret University, Invited, Graduate School of Engineering, Sebelas Maret University, Solo, Indnesia, International conference
18 Oct. 2019

Method for Improving Air-side Heat Transfer using Metal Sintered High Porosity Porous
Koji Enoki
Invited oral presentation, English, 6th ICE-SEAM 2019, Invited, RISTEKDIKTI, Indonesia, https://iceseam2019.ft.uns.ac.id/keynotes/, International conference
16 Oct. 2019

Fundamental of How to Enhancement of Heat Exchange in my Study
Koji Enoki
Public discourse, English, Sebelas Maret University, Invited, Graduate School of Engineering, Sebelas Maret University, Solo, Indnesia, International conference
18 Oct. 2018

General Lecture on Thermal Engineering
Koji Enoki
Public discourse, English, Sharing and discussion on Passage to ASEAN Programs in University of PGRI Semarang, Invited, University of PGRI Semarang，P2A, Semarang, Indnesia, International conference
17 Oct. 2018

The Characteristics of Water Boiling Heat Transfer, Pressure Drop and Flow Regime in Mini-channel
Koji Enoki
Invited oral presentation, English, ICIMECE2018, Invited, Indonesia, http://icimece2018.ft.uns.ac.id/invited-speaker/, International conference
Oct. 2018

冷熱利用熱音響エンジンの開発
Y. Ueda; J. Kawasaki; N. Honzawa; T. Kato; A. Akisawa; T. Ikegami; K. Enoki
Oral presentation, Japanese, The 23 rd National Symposium on Power and Energy Systems, Domestic conference
Jun. 2018

ナノ流体を用いた高温物体の伝熱特性の解明
梅原 裕太郎; 大川 富雄; 榎木 光治; 劉 維
Oral presentation, Japanese, 日本原子力学会「2017年秋の大会」, 日本原子力学会, 北海道, Domestic conference
Sep. 2017

強制対流サブクール沸騰における気泡凝縮の数値解析
坂本 新太郎; 大堀 浩輝; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本原子力学会「2017年秋の大会」, Domestic conference
Sep. 2017

液噴流衝突時における飛散現象に関する研究
Yi Zhan; 大箭 直輝; 榎木 光治; 大川 富雄; 青柳 光裕; 大野 修司; 高田 孝
Oral presentation, Japanese, 日本原子力学会「2017年秋の大会」, Domestic conference
Sep. 2017

サブクール沸騰熱伝達におけるポーラス伝熱面を用いた伝熱面拡大と流体の攪拌の影響
大箸 淳記; SANTIAGO GALICIA Edgar; 熊取 弘祐; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 2017年度日本冷凍空調学会年次大会, Domestic conference
Sep. 2017

マイクロチャンネル熱交換器の垂直ヘッダーにおける広範囲流量分配特性
REDO Mark Anthony; GIANNETTI Niccolo; JEONG Jongsoo; 鄭 宗秀; 榎木 光治; 太田 育秀; 山口 誠一; 齋藤 潔; 金 鉉永
Oral presentation, English, 2017年度日本冷凍空調学会年次大会, Domestic conference
Sep. 2017

液滴・液膜衝突時における二次液滴の生成条件
北林 草太; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本混相流学会 混相流シンポジウム2017, Domestic conference
Aug. 2017

分裂した液噴流の固体面衝突時における飛散液滴に関する研究
ZHAN Yi; 大箭 直輝; 榎木 光治; 大川 富雄; 青柳 光裕; 大野 修司; 高田 孝
Oral presentation, Japanese, 日本混相流学会 混相流シンポジウム2017, Domestic conference
Aug. 2017

気泡追跡法による強制対流サブクール沸騰の数値解析
坂本 新太郎; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本混相流学会 混相流シンポジウム2017, Domestic conference
Aug. 2017

ポーラスマイクロチャンネル内沸騰流における流動安定性
大箸 淳記; SANTIAGO Edgar; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本混相流学会 混相流シンポジウム2017, Domestic conference
Aug. 2017

並列多穴微細流路内における気液二相流の流動様相観察と偏流メカニズムの解明
大野 正晴; 中村 太一; 榎木 光治; 大川 富雄; 西田 耕作; 加藤 雅士
Oral presentation, Japanese, 日本混相流学会 混相流シンポジウム2017, Domestic conference
Aug. 2017

ナノ流体による高温物体のクエンチ特性変化
梅原 裕太郎; 大川 富雄; 榎木 光治
Oral presentation, Japanese, 日本混相流学会 混相流シンポジウム2017, Domestic conference
Aug. 2017

ナノ流体沸騰熱伝達におけるナノ粒子層剥離
渡辺 陽介; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本混相流学会 混相流シンポジウム2017, Domestic conference
Aug. 2017

マイクロチャンネル垂直ヘッダーにおけるR410Aの二相流分配特性
レド マーク; ジャンネッティ ニコロ; 鄭 宗秀; 榎木 光治; 太田 育秀; 齋藤 潔; 金 鉉永
Oral presentation, English, 日本機械学会 第27回 環境工学総合シンポジウム2017, Domestic conference
Jul. 2017

ポーラスマイクロチャンネルを用いた高熱流束伝熱面の安定冷却
大川 富雄; 大箸 淳記; 平田 涼; 榎木 光治
Oral presentation, Japanese, 自動車技術会(SAE) 2017年春季大会, Domestic conference
Jul. 2017

ナノ流体沸騰熱伝達に及ぼすナノ粒子層の剥離の影響
渡辺 陽介; 大川 富雄; 榎木 光治
Oral presentation, Japanese, 日本原子力学会「2017年春の大会」, Domestic conference
Jun. 2017

強制対流サブクール沸騰の数値解析における気泡の伝熱面離脱速度の影響
坂本 新太郎; 海保 和宏; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本原子力学会「2017年春の大会」, Domestic conference
Mar. 2017

サブクール沸騰中における気泡生成特性
大川 富雄; 海保 和宏; 坂本 新太郎; 榎木 光治
Oral presentation, Japanese, 日本原子力学会「2017年春の大会」, Domestic conference
Mar. 2017

ナノ流体による高温物体の超高速冷却
梅原 裕太郎; 大川 富雄; 榎木 光治
Oral presentation, Japanese, 日本原子力学会「2017年春の大会」, Domestic conference
Mar. 2017

液体噴流の固体面衝突時における飛散液滴に関する研究
Zhan Yi; 大箭 直輝; 榎木 光治; 大川 富雄; 青柳 光裕; 大野 修司; 高田 孝
Oral presentation, Japanese, 日本原子力学会「2017年春の大会」, Domestic conference
Mar. 2017

強制対流サブクール沸騰の数値解析における気泡の伝熱面離脱条件
坂本 新太郎; 海保 和宏; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本機械学会 関東学生会第56回学生員研究発表講演会, Domestic conference
Mar. 2017

微細流路内における気液二相流動特性に関する研究
中村 太一; 大野 正晴; 榎木 光治; 大川 富雄; 加藤 雅士; 西田 耕作
Oral presentation, Japanese, 日本機械学会 関東学生会第56回学生員研究発表講演会, Domestic conference
Mar. 2017

ポーラスマイクロチャンネル内における熱流束と騒音低減及び圧力変動の関係性
平田 涼; 大箸 淳記; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本機械学会 関東学生会第56回学生員研究発表講演会, Domestic conference
Mar. 2017

ナノ流体中における高温物体のクエンチ特性
梅原 裕太郎; 大川 富雄; 榎木 光治; 緒方 隆志
Oral presentation, Japanese, 日本機械学会 関東学生会第56回学生員研究発表講演会, Domestic conference
Mar. 2017

ナノ流体沸騰熱伝達におけるナノ粒子層の剥離
渡辺 陽介; 大川 富雄; 榎木 光治
Oral presentation, Japanese, 日本機械学会 関東学生会第56回学生員研究発表講演会, Domestic conference
Mar. 2017

液滴・薄液膜衝突時に生じる二次液滴に関する研究
北林 草太; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本機械学会 関東学生会第56回学生員研究発表講演会, Domestic conference
Mar. 2017

液噴流の固体面衝突時における飛散液滴生成に関する研究
榎木 光治
Oral presentation, Japanese, 日本冷凍空調学会調査研究プロジェクト, Invited, Domestic conference
Mar. 2017

強制対流サブクール沸騰の数値解析における気泡の伝熱面離脱条件の影響
坂本 新太郎; 海保 和宏; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本機械学会 熱工学コンファレンス2016, Domestic conference
Oct. 2016

ポーラスマイクロチャンネル内沸騰流における圧力変動及び発生音の計測
大箸 淳記; 平田 涼; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本機械学会 熱工学コンファレンス2016, Domestic conference
Oct. 2016

液滴・薄液膜衝突時の二次液滴生成に関する研究
北林 草太; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本機械学会 熱工学コンファレンス2016, Domestic conference
Oct. 2016

サブクール沸騰中の気泡径分布に及ぼす各種パラメータの影響
海保 和宏; 坂本 新太郎; 念 剛; 榎木 光治
Oral presentation, Japanese, 日本原子力学会「2016年秋の大会」, Domestic conference
Sep. 2016

液体噴流の固体面衝突時における液滴生成に関する研究
大箭 直輝; 詹 翼; 榎木 光治; 大川 富雄; 青柳 光裕; 大野 修司; 高田 孝
Oral presentation, Japanese, 日本原子力学会「2016年秋の大会」, Domestic conference
Sep. 2016

ミニチャンネル内垂直上昇流における水の沸騰熱伝達特性に関する研究
中村 太一; 大野 正晴; MD.AMIRUL ISLAM; 榎木 光治; 大川 富雄; 小澤 守
Oral presentation, Japanese, 2016年度日本冷凍空調学会年次大会, Domestic conference
Sep. 2016

微細流路内気液二相流の沸騰熱伝達と流動様相に関する研究
榎木 光治
Nominated symposium, Japanese, 日本混相流学会 若手研究者夏季セミナー2016, Invited, Domestic conference
Sep. 2016

ポーラスマイクロチャンネルを用いた高熱流束除熱
大箸 淳記; 塚本 晋大; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本機械学会 第21回 動力・エネルギー技術シンポジウム, Domestic conference
Jun. 2016

液滴の液膜衝突時における二次液滴生成に関する研究
榎木 光治; 松瀬 滉平; 大川 富雄
Oral presentation, Japanese, 日本機械学会 第21回 動力・エネルギー技術シンポジウム, Domestic conference
Jun. 2016

微細矩形流路内における気液二相流動様相観察と振動の及ぼす影響
大野 正晴; 榎木 光治; 長山 国弘; 秋澤 淳; 大川 富雄; 宮田 一司; 森 英夫
Oral presentation, Japanese, 日本機械学会 第21回 動力・エネルギー技術シンポジウム, Domestic conference
Jun. 2016

強制対流サブクール沸騰の可視化とボイド率解析
大川 富雄; 海保 和宏; 宮野 直樹; 榎木 光治
Oral presentation, Japanese, 第53回 日本伝熱シンポジウム, Domestic conference
May 2016

液体噴流の液面衝突に関する研究
大箭 直輝; 大川 富雄; 榎木 光治; 大野 修司; 青柳 光裕
Oral presentation, Japanese, 日本原子力学会「2016年春の大会」, Domestic conference
Mar. 2016

粒子流体モデルを用いたサブクール沸騰の数値解析
大川 富雄; 宮野 直樹; 海保 和宏; 榎木 光治
Oral presentation, Japanese, 日本原子力学会「2016年春の大会」, Domestic conference
Mar. 2016

サブクール流動沸騰中における気泡生成挙動に関する研究
海保 和宏; 土江 健太; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本原子力学会「2016年春の大会」, Domestic conference
Mar. 2016

ポーラスマイクロチャンネル内における流動不安定性に関する研究
塚本 晋大; 大箸 淳記; 大川 富雄; 榎木 光治
Oral presentation, Japanese, 日本機械学会 関東学生会第５５回学生員卒業研究発表講演会, Domestic conference
Mar. 2016

ポーラスマイクロチャンネル内における気泡微細化沸騰
大箸 淳記; 塚本 晋大; 大川 富雄; 榎木 光治
Oral presentation, Japanese, 日本機械学会 関東学生会第５５回学生員卒業研究発表講演会, Domestic conference
Mar. 2016

微細流路内における気液二相流動様相観察と振動の影響
大野 正晴; 長山 国弘; 榎木 光治; 大川 富雄; 秋澤 淳; 森 英夫; 宮田 一司
Oral presentation, Japanese, 日本機械学会 関東学生会第５５回学生員卒業研究発表講演会, Domestic conference
Mar. 2016

サブクール沸騰中における気泡の伝熱面離脱速度
土江 健太; 海保 和宏; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本機械学会 関東学生会第５５回学生員卒業研究発表講演会, Domestic conference
Mar. 2016

噴流衝突時に形成される液膜挙動に関する研究
竹之上 聡; 北風 祥吾; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本機械学会 関東学生会第５５回学生員卒業研究発表講演会, Domestic conference
Mar. 2016

噴流衝突時に形成される液膜挙動に関する研究
竹之上 聡; 北風 祥吾; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本機械学会 関東学生会第５５回学生員卒業研究発表講演会, Domestic conference
Mar. 2016

微細矩形流路内における気液二相流動様相および振動の及ぼす影響
長山 国弘; 榎木 光治; 大野 正晴; 秋澤 淳; 大川 富雄; 宮田 一司; 森 英夫
Oral presentation, Japanese, 2015年度日本冷凍空調学会年次大会, Domestic conference
Oct. 2015

動的シミュレーションを用いたNH3－H2O系溶液輸送型吸収冷凍機の10000m輸送配管が制御性および冷媒，溶液受液器に及ぼす影響
渡辺 史; 田中 成吾; 榎木 光治; 秋澤 淳; 武居 俊孝
Oral presentation, Japanese, 2015年度日本冷凍空調学会年次大会, Domestic conference
Oct. 2015

気泡追跡法によるサブクール沸騰の数値解析
宮野 直樹; 海保 和宏; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本機械学会 熱工学コンファレンス2015, Domestic conference
Oct. 2015

低圧時サブクール流動沸騰中における沸騰挙動の可視化解析
海保 和宏; 土江 健太; 宮野 直樹; 榎木 光治; 大川富雄
Oral presentation, Japanese, 日本機械学会 熱工学コンファレンス2015, Domestic conference
Oct. 2015

液面衝突噴流の液滴生成に関する研究
大箭 直輝; 榎木 光治; 大川 富雄
Oral presentation, Japanese, 日本原子力学会「2015年秋の大会」, Domestic conference
Sep. 2015

サブクール沸騰中における沸騰挙動の可視化解析
海保 和宏; 土江 健太; 大川 富雄; 榎木 光治
Oral presentation, Japanese, 日本原子力学会「2015年秋の大会」, Domestic conference
Sep. 2015

ミニチャンネル内の気液二相流動様相と相変化熱伝達の特性
榎木 光治
Public discourse, Japanese, 第154回流体懇話会, Domestic conference
Jul. 2015

微細流路内相変化熱伝達と伝熱促進メカニズム
榎木 光治
Public discourse, Japanese, 日本機械学会環境工学部門 吸収・吸着を用いた環境制御の高度化に関する研究会 第一回研究交流会, Invited, Domestic conference
Nov. 2014

大規模化された溶液輸送型吸収冷凍機の長距離熱輸送における動的解析
榎木 光治; 田中成吾; 渡辺史; 秋澤淳; 上田祐樹; 武居俊孝
Oral presentation, Japanese, 2014年度日本冷凍空調学会年次大会, Domestic conference
Sep. 2014

溶液輸送型吸収冷凍機の 200m 熱輸送実験に基づくシミュレーションモデルの開発
田中 成吾; 渡辺 史; 榎木 光治; 秋澤 淳; 上田 祐樹; 武居 俊孝
Oral presentation, Japanese, 2014年度日本冷凍空調学会年次大会, Domestic conference
Sep. 2014

太陽熱利用による吸着冷凍機とデシカント空調機の連成システムの運転実績
大原 裕史; 山口 大貴; 榎木 光治; 上田 祐樹; 秋澤 淳
Oral presentation, Japanese, 2014年度日本冷凍空調学会年次大会, Domestic conference
Sep. 2014

音波の速度振幅と圧力振幅が湿分吸着促進に与える影響の評価
大久保 賢一; 榎木 光治; 上田 祐樹; 秋澤 淳
Oral presentation, Japanese, 2014年度日本冷凍空調学会年次大会, Domestic conference
Sep. 2014

Three stage adsorption cycle with three adsorption beds
I G. A. B. Wirajati; M. Umair; K. Enoki; Y. Ueda; A. Akisawa
Oral presentation, English, 2014年度日本冷凍空調学会年次大会, Domestic conference
Sep. 2014

CPC一体型吸着材充填層内の熱伝導解析
DWIPUTRO Achmad Faisal; UMAIR Muhammad; 榎木 光治; 上田 祐樹; 秋澤 淳
Oral presentation, Japanese, 日本機械学会 関東支部第 20 期総会・講演会
Mar. 2014

微細三角形流路における気液二相流の流動様相
松瀬 裕大; 中津留 拓哉; 榎木 光治; 森 英夫; 仮屋 圭史; 濱本 芳徳
Oral presentation, Japanese, 2013年度日本冷凍空調学会年次大会, Domestic conference
Sep. 2013

微細管内気液二相流の流動様相
榎木 光治; 森 英夫; 宮田 一司; 濱本 芳徳
Oral presentation, Japanese, 2012年度日本冷凍空調学会年次大会, Domestic conference
Sep. 2012

微細円管内水平流の沸騰熱伝達と圧力損失
榎木 光治; 森 英夫; 宮田 一司; 田代 雅浩; 仮屋 圭史; 濱本 芳徳
Oral presentation, Japanese, 2011年度日本冷凍空調学会年次大会, Domestic conference
Sep. 2011

微細管内気液二相流動様相の観察
榎木 光治; 宮田 一司; 森 英夫; 仮屋 圭史; 濱本 芳徳
Public discourse, Japanese, 日本冷凍空調学会 第11回西日本地区技術交流会, Domestic conference
Oct. 2010

微細円管内水平流の沸騰熱伝達と圧力損失
榎木 光治; 森 英夫; 宮田 一司; 田代 雅浩; 仮屋 圭史; 濱本 芳徳
Oral presentation, Japanese, 2010年度日本冷凍空調学会年次大会, Domestic conference
Sep. 2010

微細流路内気液二相流の流動様相観察
榎木 光治; 宮田 一司; 森 英夫; 濱本 芳徳
Oral presentation, Japanese, 日本伝熱学会 第47回日本伝熱シンポジウム, Domestic conference
May 2010

垂直微細管内沸騰流の伝熱様式
榎木 光治; 宮田 一司; 森 英夫; 濱本 芳徳
Oral presentation, Japanese, 日本機械学会 九州支部講演論文集, Domestic conference
Mar. 2010

垂直三角形微細内上昇流の沸騰熱伝達と圧力損失
榎木 光治; 宮田 一司; 森 英夫; 濱本 芳徳
Oral presentation, Japanese, 2009年度日本冷凍空調学会年次大会, Domestic conference
Oct. 2009

矩形微細管内上昇流の沸騰熱伝達と圧力損失
宮田 一司; 榎木 光治; 森 英夫; 濱本 芳徳
Oral presentation, Japanese, 日本伝熱学会 第46回日本伝熱シンポジウム, Domestic conference
Jun. 2009

Foundations of Sustainability Research B (Shared lecture: Thermal Energy Conversion)
Oct. 2023
Joint Doctoral Program for Sustainability Research, Graduate school liberal arts course

Fluid Mechanics
Sebelas Maret University

Fluid Mechanics (流体力学、分担)
Sebelas Maret University

メカトロニクス基礎実験B・知能機械工学基礎実験第二（風洞実験のWeb講義，および実験幹事を担当）
The University of Electro-Communications

メカトロニクス基礎実験B・知能機械工学基礎実験第二（風洞実験のWeb講義，および実験幹事を担当）
電気通信大学

メカトロニクス基礎実験A・知能機械工学基礎実験第一（風洞実験のWeb講義，および実験幹事を担当）
The University of Electro-Communications

メカトロニクス基礎実験A・知能機械工学基礎実験第一（風洞実験のWeb講義，および実験幹事を担当）
電気通信大学

熱工学基礎
The University of Electro-Communications

熱工学基礎
電気通信大学

確率統計
The University of Electro-Communications

確率統計
電気通信大学

メカトロニクス基礎実験B・知能機械工学基礎実験第二
The University of Electro-Communications

メカトロニクス基礎実験B・知能機械工学基礎実験第二
The University of Electro-Communications

メカトロニクス基礎実験B・知能機械工学基礎実験第二
電気通信大学

メカトロニクス基礎実験A・知能機械工学基礎実験第一
The University of Electro-Communications

メカトロニクス基礎実験A・知能機械工学基礎実験第一
電気通信大学

知能機械工学基礎実験 Ⅱ
The University of Electro-Communications

知能機械工学基礎実験 Ⅱ
電気通信大学

知能機械工学基礎実験 I
The University of Electro-Communications

知能機械工学基礎実験 I
電気通信大学

機械システム工学実験
東京農工大学

機械システム工学実験
東京農工大学

物理科学実験A
The University of Electro-Communications

専門実験B
The University of Electro-Communications

物理科学実験A
The University of Electro-Communications

物理科学実験A
電気通信大学

Feb. 2023
総合コミュニケーション科学学会

日本太陽エネルギー学会

American Society of Thermal and Fluids Engineers(ASTFE)

THE HEAT TRANSFER SOCIETY OF JAPAN

THE JAPAN SOCIETY OF MECHANICAL ENGINEERS

The Japanese Society for Multiphase Flow

JAPAN SOCIETY OF REFRIGERATING AND AIR CONDITIONING ENGINEERS

Development of High-Efficiency Refrigeration and Air-Conditioning Technology for Practical Use of Next-Generation Low-GWP Refrigerants/ Development and evaluation of low-GWP mixed refrigerants suitable for home air-conditioning, etc. Development of Safety and Performance Evaluation of Low GWP Mixed Refrigerants and Development of Overall System Evaluation Method /Development of system evaluation method for low GWP mixed refrigerants
再委託先; 研究代表者
NEDO, 次世代低GWP冷媒の実用化に向けた高効率冷凍空調技術の開発
Apr. 2023 - Mar. 2025

多孔質体の熱伝達率および有効熱伝導率予測のための深層学習法の確立
榎木 光治; YANINGSIH INDRI
日本学術振興会, 科学研究費助成事業 特別研究員奨励費, 電気通信大学, 特別研究員奨励費, 22F20057
22 Apr. 2022 - 31 Mar. 2024

飛躍的な熱伝達を達成する焼結型多孔質伝熱管の伝熱メカニズムの解明と応用研究
Koji Enoki
日本学術振興会, 科学研究費助成事業 基盤研究(C), 電気通信大学, 基盤研究(C), Principal investigator, 金属繊維多孔質体について，内径18mmで金属多孔質体を空隙率80％で充填長さ25mmで充填し，オール純アルミで生成された試験体を元に，実験的研究とシミュレーション解析を実施した．実験的な結果では，流速が遅い領域では300℃の温度差が取得出来ることが判明し，流速を上げると徐々に出口温度が上昇し250℃の温度差になる事がわかった．これは従来径管では50℃ほどの温度差も取れなかったことを考えると，飛躍的な熱交換効率である．この多孔質体をCTスキャン化して数値シミュレーション解析を行った．この結果は，実験結果と定量的にも定性的にも一致し，伝熱量だけでなく摩擦圧力損失までプラスマイナス10％程度と非常に高精度で再現することができた．これは何を意味するかというと，従来は多孔質体内の温度や圧力分布，流速などが不明であったが，シミュレーションにより今後はデータが得られることで，飛躍的な熱交換を行う伝熱管の物理メカニズムの解明を行う事で，他の伝熱管の最適設計などへ応用することが可能となる．, 21K03914
01 Apr. 2021 - 31 Mar. 2024

熱エネルギーの有効利用について
榎木光治
東芝エネルギーシステム社, 学術相談, 学術相談, Principal investigator
Sep. 2023 - Dec. 2023

多孔質体の熱伝達率および有効熱伝導率予測のための深層学習法の確立
榎木 光治; YANINGSIH INDRI
日本学術振興会, 科学研究費助成事業 特別研究員奨励費, 電気通信大学, 特別研究員奨励費, 21F20057
28 Apr. 2021 - 31 Mar. 2023

省エネ化・低温室効果を達成できる次世代冷凍空調技術の最適化及び評価手法の開発／ 次世代冷媒の基本特性に関するデータ取得及び評価／ 低ＧＷＰ冷媒を採用した次世代冷凍空調機器の実用化評価に関する研究開発／ 性能解析技術研究開発及び性能評価技術研究開発 その他助成金 NEDO（国立研究開発法人 新エネルギー・産業技術総合開発機構） 研究助成
Koji Enoki
NEDO, 研究助成, Principal investigator
01 Apr. 2021 - 31 Mar. 2023

多孔質体の熱伝達率および有効熱伝導率予測のための深層学習法の確立
榎木 光治; YANINGSIH INDRI
日本学術振興会, 科学研究費助成事業 特別研究員奨励費, 電気通信大学, 特別研究員奨励費, 20F20057
24 Apr. 2020 - 31 Mar. 2022

吸着冷凍機の研究開発に一石を投ずる人工知能AIを用いた多種多様な吸着材の吸着特性の予測法確立への挑戦
Koji Enoki
公益財団法人 前川報恩会, 研究助成
01 Jan. 2020 - 31 Jan. 2022

（学術相談）バイナリー発電熱交換器の最適運転方法
モビリティエナジーサーキュレーション株式会社, 学術相談
Dec. 2020 - Jun. 2021

Optimization and evaluation method of next generation air conditioning technology that can achieve energy saving low GDP
Koji Enoki; Research Leader of subcontractor
NEDO（New Energy and Industrial Technology Development Organization）, 研究助成, Principal investigator
Aug. 2018 - Mar. 2021

（学術相談）本田技術研究所
本田技術研究所, 学術相談
Jun. 2020 - Aug. 2020

LNG冷熱利用熱音響エンジン発電技術の研究開発
Koji ENOKI
NEDO（New Energy and Industrial Technology Development Organization）, エネルギー・環境新技術先導プログラム, Principal investigator
Apr. 2017 - Mar. 2019

パラレルマイクロチャンネル内気液二相流れに関する包括的研究
公益社団法人 前川報恩会
Dec. 2016 - Dec. 2017

Study on the heat transfer coefficient and nano-particle layer peeling for industrial use of the boiling heat transfer of nanofluid
Okawa Tomio; ENOKI Koji; Muhamad Zuhairi Bin Sulaiman; MATSUO Daisuke; KOBAYASHI Taiga; WATANABE Yosuke
Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), The University of Electro-Communications, Grant-in-Aid for Scientific Research (C), Nanofluid is paid particular attention as the promising method to enhance critical heat flux in boiling heat transfer. It is considered that the CHF enhancement is mainly caused by the modification of surface properties such as the wettability and roughness due to the formation of nanoparticle layer on the heated surface. However, since adhesion of the nanoparticle layer is not firm, peeling of the layer often occurs during boiling. In the present work, peeling test was conducted to measure quantitatively the adhesion strength of the nanoparticle layer formed on the heated surface. It was found that the total mass and the adhesion strength of the nanoparticle layer were dependent strongly on the particle material. The CHF enhancement ratio by nanoparticle layer tended to decrease with an increase in the peeling ratio. It may be interesting to note that the boiling heat transfer was improved whilst CHF was deteriorated with the increase of the loss of nanoparticles., 26420140
01 Apr. 2014 - 31 Mar. 2017

マイクロチャンネル内における気液二相流動様相に及ぼす物性の影響に関する研究
榎木 光治
公益社団法人前川報恩会, Principal investigator
Dec. 2015 - Dec. 2016

マイクロチャンネル内における気液二相流動様相に及ぼす物性と飽和温度の影響に関する研究
榎木 光治
一般社団法人前川報恩会, Principal investigator
Dec. 2014 - Dec. 2015

空調用高性能熱交換器開発のための微細流路内相変化熱伝達と伝熱促進メカニズムの解明
Koji Enoki
日本学術振興会, 科学研究費助成事業 特別研究員奨励費, 九州大学, 特別研究員奨励費, Principal investigator, 内径あるいは一辺が1㎜程度の微細流路を有する円管と矩形管および三角形管を対象に, 冷媒R410AとR32を用いて, 垂直上昇と下降および水平流における気液二相流動様相の観察および沸騰熱伝達と圧力損失に関する実験を行い, 以下の結果を得た. 1. 微細流路内の流動様相や沸騰熱伝達および圧力損失に及ぼす流路形状や流動方向の影響, つまり表面張力や重力の影響は, 全般に, 質量速度が100kg/(m^2-s)以下の低流量で現れた. 2. 可視化ガラス管を加熱して沸騰熱伝達試験に近い条件で管内冷媒の様子を観察したことで, 流路形状によらず垂直流よりも水平流の熱伝達が, 流動方向によらず円管よりも非円形管の熱伝達が良好になる伝熱メカニズムを明らかにした. 3. 微細流路内断熱気液二相流の観察結果をもとに, 気液各相のWe数で整理されたChenらの流動様式線図を低流量へ拡張し, 円形, 矩形, および三角形流路の垂直上昇流と下降流さらに水平流に適用可能な新たな5つの流動様式線図を作成した. 4. 予定していた実験計画が早期に終了したため, これまでの研究で使用してきた冷媒R410Aよりも地球温暖化係数が小さく今後使用が予想されるR32を用いて水平流の実験を行った. R32とR410Aを比較すると, 熱伝達率は全般にR32の方が高く, また圧力損失については, ともにスラグ流が観察される領域で同等, それ以外の流動様式ではR32の方が大きくなることがわかった. 以上の成果は, 雑誌論文として4編が掲載, 1編が投稿中で, 空調用熱交換器の高性能化, コンパクト化に大いに貢献するものと期待できる., 12J00771
01 Apr. 2012 - 31 Mar. 2014

微細流路内相変化熱伝達と伝熱促進メカニズムの解明
榎木 光治
九州大学アカデミックチャレンジ, 研究助成, Principal investigator
Apr. 2010 - Mar. 2011

エネルギー有効活用の為のヒートポンプ高性能化に関する研究
榎木 光治
日本学術振興会, 海外渡航助成プログラム, Principal investigator
Dec. 2010 - Dec. 2010

PCT(CHAINA)HEAT EXCHANGER PLATE, HEAT EXCHANGER PLATE LAMINATE, AND MICROCHANNEL HEAT EXCHANGER
Patent right, Koji Enoki, Kosaku Nishida, Ikuo Akada, 特願202280028833.1, Date applied: 16 Oct. 2023, Mayekawa Mfg. Co., Ltd.,The University of Electro-Communications, Domestic, Domestic

PCT(EPC)HEAT EXCHANGER PLATE, HEAT EXCHANGER PLATE LAMINATE, AND MICROCHANNEL HEAT EXCHANGER
Patent right, Koji Enoki, Kosaku Nishida, Ikuo Akada, 特願22915849.8, Date applied: 16 Oct. 2023, Domestic, Domestic

PCT(KOREA)HEAT EXCHANGER PLATE, HEAT EXCHANGER PLATE LAMINATE, AND MICROCHANNEL HEAT EXCHANGER
Patent right, Koji Enoki, Kosaku Nishida, Ikuo Akada, 特願10-2023-7036783, Date applied: 16 Oct. 2023, Mayekawa Mfg. Co., Ltd.,The University of Electro-Communications, Domestic, Domestic

PCT(JAPAN)HEAT EXCHANGER PLATE, HEAT EXCHANGER PLATE LAMINATE, AND MICROCHANNEL HEAT EXCHANGER
Patent right, Koji Enoki, Kosaku Nishida, Ikuo Akada, 特願2023-570896, Date applied: 16 Oct. 2023, Mayekawa Mfg. Co., Ltd.,The University of Electro-Communications, Domestic, Domestic

PCT(INDIA)HEAT EXCHANGER PLATE, HEAT EXCHANGER PLATE LAMINATE, AND MICROCHANNEL HEAT EXCHANGER
Patent right, Koji Enoki, Kosaku Nishida, Ikuo Akada, 特願202317072814, Date applied: 16 Oct. 2023, Mayekawa Mfg. Co., Ltd.,The University of Electro-Communications, Koji Enoki Kosaku Nishida Ikuo Akada, Domestic, Domestic

PCT(US)HEAT EXCHANGER PLATE, HEAT EXCHANGER PLATE LAMINATE, AND MICROCHANNEL HEAT EXCHANGER
Patent right, Koji Enoki, Kosaku Nishida, Ikuro Akada, 特願18/554,912, Date applied: 16 Oct. 2023, Mayekawa Mfg. Co., Ltd.,The University of Electro-Communications, Domestic, Domestic

熱吸収構造体および温度差発電装置
Patent right, 榎木 光治 , 葛西 純 , 葛西 成美 , 中野 和司 , 横井 浩史, 特願2023-029123, Date applied: 28 Feb. 2023, 株式会社フォルテ , 国立大学法人電気通信大学, Domestic

PCT国際特許出願 熱交換器
Patent right, 榎木光治,西田耕作,赤田郁朗, PCT/JP2022/047036, Date applied: 21 Dec. 2022, Pct

Heat Exchanger
Patent right, 特願2017-140055, Date applied: Jul. 2017, 西田耕作，榎木光治，加藤雅士，大川富雄, 特開2019-20068, Date announced: Feb. 2018, 特許7072790号, Date issued: 13 May 2022

熱交換器用プレート、熱交換器用プレート積層体、及びマイクロチャンネル熱交換器
Patent right, 榎木光治, 西田耕作, 赤田郁朗, 特願2021-21493, Date applied: 28 Dec. 2021

シリンジポンプ装置
Patent right, 榎木光治, 宮田一司, 秋澤淳, 大川富雄, 特願2017-072214, Date applied: Mar. 2017, 榎木光治，宮田一司，秋澤淳，大川富雄, 特開2018-173038, Date announced: Nov. 2018, 特許第6899132号, Date issued: 16 Jun. 2021

熱音響システム用熱交換器、往復振動流を用いたエネルギー変換器、熱音響エンジン、および、スターリングエンジン
Patent right, 榎木光治, 上田祐樹, 秋澤淳, 川崎淳平, 特願2019-049139, Date applied: Mar. 2019, 特願2018-48000の優先権主張

Boiler
Patent right, Tomio Okawa, Koji Enoki, 特願2016-242453, Date applied: Dec. 2016, 特開2018-96631, Date announced: Jun. 2018

Heat Exchanger for a Thermoacoustic System
Patent right, Koji Enoki, Yuki Ueda, Atsushi Akisawa, Junpei Kawasaki, 特願2018-048000, Date applied: Mar. 2018, The University of Electro-Communications

微細流路を用いた熱交換器の沸騰熱伝達性能シミュレーション装置、およびプログラム
Patent right, 榎木光治, 宮田一司, 森英夫, 特願2015-150851, Date applied: Jul. 2015, 特開2017-32347, Date announced: Jul. 2017

冷却剤
Patent right, 大川 富雄, 梅原 裕太郎, 榎木 光治, 特願2018-044725, Date applied: Mar. 2018, 特願2017-046260の優先権主張, Date announced: Mar. 2017

冷却剤、冷却装置および冷却方法
Patent right, 大川 富雄, 梅原 裕太郎, 榎木 光治, 特願2017-046260, Date applied: Mar. 2017

やまがた環境展2023 積雪発電について山形県最上総合支庁環境課からの依頼展示
Panelist, 山形県、一般社団法人山形県産業資源循環協会、NPO法人山形県自動車公益センター、山形県環境保全協議会、山形県商工会議所連合会, やまがた環境展2023, 山形ビッグウイング, Festival
14 Oct. 2023 - 15 Oct. 2023

高校との接続事業（出張講義）
Lecturer, 静岡県立磐田南高等学校, 脱炭素社会への希望の光！ 積雪および太陽熱発電の発電技術について, Visiting lecture
13 Sep. 2023

高校との接続事業（出張講義）
Lecturer, 東京都立豊多摩高等学校, カーボンニュートラル実現のためにエネルギーを理解しよう！, Visiting lecture
14 Jul. 2023

おばね雪発電
Lecturer, 山形県尾花沢市, ｢おばね発電｣エネルギー棟施設見学 & 講習会
02 Jun. 2023

積雪発電の研究開発の概要とエネルギーの地産地消について
Lecturer, 社会福祉法人大石田町社会福祉協議会, 除雪体制づくりプロジェクト会議, Lecture
01 Jun. 2023

積雪発電の研究開発の概要とエネルギーの地産地消について
Lecturer, 山形県最上総合支庁環境課, 令和４年度最上地域エネルギー戦略推進協議会講演会, Lecture
22 Feb. 2023

高校との接続事業（出張講義）
Appearance, 城北埼玉中学・高校（3年生から5年生）, カーボンニュートラルについて, 真空下での水の沸騰や，水を利用した冷凍空調機の開発の仕組みなどを高校生へ解るように実験を取り入れた． また，勉強する理由について，伝えられる範囲でつたえた．
25 Nov. 2022

高校との接続事業（出張講義）
Appearance, 三鷹中等教育学校（4年生と5年生）, カーボンニュートラルについて, 真空下での水の沸騰や，水を利用した冷凍空調機の開発の仕組みなどを高校生へ解るように実験を取り入れた． また，勉強する理由について，伝えられる範囲でつたえた．
04 Oct. 2022

夢ナビライブ2021 中・高校生を対象としたリアルタイム講義・質問対応・研究室訪問
Appearance, FROMPAGE・文部科学省・大学教育センター, 熱との戦いを制してサステイナブルな社会の実現へ, Zoom, 高校生
11 Jul. 2021

夢ナビオンデマンド2021 中・高校生を対象としたオンデマンド講義
Appearance, FROMPAGE・文部科学省・大学教育センター, 熱との戦いを制してサステイナブルな社会の実現へ, Web上, 高校生
Jun. 2021

高校との接続事業（出前授業）
Appearance, 山形県立酒田東高等学校, 身の回りには沸騰や凝縮があふれている？？, 山形県立酒田東高等学校 最新最高機種の高速度カメラの映像等を駆使して，理科科目に興味を持ってもらうために，工夫した．
12 Nov. 2020

高校との接続事業（出前授業）
Appearance, 沖縄県立球陽高等学校 SSHコース, 高校と大学の違いについて 高速度カメラを実際に触れてみよう, 沖縄県立球陽高等学校 SSHコース 高速度カメラやサーモグラフィを実際に触れてもらって，理科科目へ興味を持ってもらった．
14 Nov. 2018

生涯学習支援等への貢献 高等学校・高等専門学校等への出張講義
Lecturer
2016

高校との接続事業（出前授業）
Appearance, 宮崎県立宮崎南高等学校, 母校への皆さんへ□修学旅行中ごめんねバージョン□, 宮崎県立宮崎南高等学校
11 Dec. 2014

knowledgeable opinion カーボンニュートラル ”ヒートポンプと私の歩み”
Myself, 一般財団法人ヒートポンプ・蓄熱センター, 一般財団法人ヒートポンプ・蓄熱センター, https://www.hptcj.or.jp/tabid/2204/Default.aspx, Pr
21 Mar. 2024

ゲレンデの自然を次世代につなぐ スキー場の使用電力を再エネ｢100%｣に
日経XTREND, 日経XTREND, https://special.nikkeibp.co.jp/atclh/NXR/24/tokyu_land0301/, Internet
14 Mar. 2024

ゲレンデの自然を次世代につなぐ スキー場の使用電力を再エネ｢100%｣に
日経ビジネス, 日経ビジネス, Paper
04 Mar. 2024

ニセコから世界へ発信 豪雪地帯のコストを減らす「積雪発電｣
東急不動産ホールディングス 環境先進スペシャルサイト, 東急不動産ホールディングス 環境先進スペシャルサイト, https://www.tokyu-fudosan-hd.co.jp/kankyo/news/29/, Internet
27 Feb. 2024

カーボンニュートラル実現に向けた未利用熱の効率回収
読売新聞朝刊 鹿児島県版, 読売新聞朝刊 鹿児島県版, https://www.uec.ac.jp/news/media/2024/pdf/20240223_6038.pdf, Paper
23 Feb. 2024

雪を守れ！スキー場の電力100％を再エネ化
Other than myself, Japan In-depth, Japan In-depth, https://japan-indepth.jp/?p=81082, Internet
05 Feb. 2024

"雪は敵か味方か、付き合い方が学ぶ 秋田市でフォーラム 災害や利活用事例紹介"
Other than myself, 秋田魁新報朝刊, 秋田魁新報朝刊, https://www.sakigake.jp/news/article/20240128AK0024/, Paper
29 Jan. 2024

ニセコで「積雪発電」お湯も電気も融雪も
Other than myself, ENERGY FRONTLINE, ENERGY FRONTLINE, https://ene-fro.com/article/ef328_a1/, Internet
23 Jan. 2024

"北海道倶知安で積雪活用の発電実証実験"
毎日新聞電子版, 毎日新聞電子版, Internet
21 Jan. 2024

"北海道倶知安で積雪活用の発電実証実験"
NHK NEWS WEB（北海道）、日本経済新聞電子版、時事通信社、au Webポータル, NHK NEWS WEB（北海道）、日本経済新聞電子版、時事通信社、au Webポータル, https://www3.nhk.or.jp/lnews/aomori/20240119/movie/6080021647_20240119190950.html?movie=false
21 Jan. 2024

"北海道倶知安で積雪活用の発電実証実験"
NHK NEWS WEB（青森）、日本経済新聞地方経済面、北海道新聞朝刊、新建ハウジング, "北海道倶知安で積雪活用の発電実証実験", https://www3.nhk.or.jp/lnews/aomori/20240119/6080021647.html, Paper
19 Jan. 2024

"積もった雪 使って発電 倶知安のスキー場 温度差利用 実用化へ実験＝北海道"
1/30住宅新報web 1/25日刊建設工業新聞電子版 1/22北海道建設新聞 1/20東京読売新聞朝刊, 1/30住宅新報web 1/25日刊建設工業新聞電子版 1/22北海道建設新聞 1/20東京読売新聞朝刊, Paper
Jan. 2024

"TOKYU SNOW RESORT 雪という資源を守る環境維持に向けた取り組みを加速"
Other than myself, 東急不動産株式会社、, 北海道建設新聞, https://prtimes.jp/main/html/rd/p/000000546.000055787.html, Paper
Dec. 2023

"In Niseko, 'Snow Accumulation Power Generation': Reduced Environmental Impact and Lower Snow Removal Costs."
Other than myself, 日本経済新聞, 日本経済新聞朝刊，日本経済新聞電子版, 榎木光治准教授（機械知能システム学専攻／共同サステイナビリティ研究専攻）が共同で研究開発した積雪発電の実証実験が今冬、北海道ニセコ地区で開始, Paper
Sep. 2023

雪活用発電，可能性は
Other than myself, 山形新聞, 山形新聞, 山形県大石田町と尾花沢市での講演会で雪と外気の温度差を利用した「積雪発電」の特徴を解説, Paper
Jun. 2023

冬の雪を活用して発電する実証実験 地元企業が大学と実施
Other than myself, NHK, Media report
Mar. 2023

Electricity from snow
Other than myself, The European Times, Internet
Feb. 2023

Japanese researchers begin study into electricity generation from snow
Other than myself, The Japan Times, Internet
Jan. 2023

JAPAN WILL GENERATE ELECTRICITY FROM SNOW
Other than myself, Innovative Techs (Youtube), https://www.youtube.com/watch?v=7P2cSKl9Tns, Internet
Jan. 2023

暮らしに利用 雪と生きる（トップページ）
朝日小学生新聞, Paper
Jan. 2023

Japan’s city of Aomori to try making electricity with snow
Other than myself, SUSTAINABILITY TIMES, https://www.sustainability-times.com/low-carbon-energy/japans-city-of-aomori-to-try-making-electricity-with-snow/, Internet, 海外の記事であり，海外からのHPへのアクセス数によって見つけた記事
Dec. 2022

電通大と青森市、積雪発電を実証実験
Nikkei, 日本経済新聞社, https://www.nikkei.com/article/DGXZQOCC130RJ0T11C22A1000000/, Paper
Nov. 2022

捨てる雪で発電 青森市など、脱炭素新事業の育成も視野 https://www.nikkei.com/article/DGXZQOCC201FJ0Q2A121C2000000/
Nikkei, Paper
Nov. 2022

Electricity from snow? A Japanese city believes it can be done
NIKKEI Asia, Paper
Nov. 2022

冬の積雪活用した発電実験を説明 豪雪地帯の青森市で実施
NHK, https://www3.nhk.or.jp/lnews/aomori/20221128/6080018077.html, Media report
Nov. 2022

東京電力のWebマガジンにて，三菱マテリアルとの共同研究成果が特集記事として掲載
Other than myself, EMIRA, https://emira-t.jp/special/20863/, Internet
Jul. 2022

三菱マテリアル、従来にない高効率での熱回収が可能な伝熱管の技術を開発
日本経済新聞, https://www.nikkei.com/article/DGXLRSP619759_18102021000000/?fbclid=IwAR3btj9tadujPqWmjWGX1YNOdg7jFjZoxTeTFnuOgb-2_1C0Vpodh_c370Y, Paper
Oct. 2021

従来にない高効率での熱回収が可能な伝熱管の技術を開発 ～カーボンニュートラルで持続可能な社会の実現に向けて飛躍的な貢献を期待～ https://www.mmc.co.jp/corporate/ja/news/press/2021/21-1015a.html
Other than myself, 三菱マテリアル株式会社 公式プレスリリース, Others
Oct. 2021

三菱マテリアル株式会社と共同研究成果が，米科学振興協会(AAAS)のサイト「EurekAlert!」に掲載． 学術分野を問わず，世界でその論文の話題としての影響力を示す，Altmetric Attention Score = 14 と上位10％以内
Other than myself, 米科学振興協会(AAAS), EurekAlert!, https://techxplore.com/news/2021-10-scientists-sintered-porous-media-compact.html, Internet
Oct. 2021

報道ステーション 二酸化炭素センサの粗悪品について取材放送
Other than myself, テレビ朝日, 報道ステーション, Media report, https://www.youtube.com/watch?v=Vs2oEwlAsIk&t=103s
Aug. 2021

ザ！世界仰天ニュース「真夏のまさかの危険SP」 ドライアイスの間違った使用法による命の危険性に関する啓蒙活動
Other than myself, 日本テレビ, ザ！世界仰天ニュース, 真夏のまさかの危険SP, Media report, ±0.01℃に補正した，高精度温度計を使用した，本学の温度計測技術の対外アピールを兼ねる．
Aug. 2021

電気通信大と早大、深層学習により高精度な沸騰熱伝達予測モデルを構築
Other than myself, 日本経済新聞, https://www.nikkei.com/article/DGXLRSP466412_Y7A211C1000000/, Paper, https://www.nikkei.com/article/DGXLRSP466412_Y7A211C1000000/
Dec. 2017

The 5th ASEAN – UEC Workshop on Informatics and Engineering
Competition etc, Planning etc, ECTI Association, UEC, IEEE Comuter Society, May 2023 - 10 Sep. 2023

受託研究員受入
福岡県工業技術センター所属 博士号ホルダーの研究員受入
Jun. 2023 - Mar. 2024

研究者交流（短期派遣・招へい）支援
2018 - 2018

学内競争的資金
若手研究支援
2017 - 2017

電気通信大学タスクフォース成果論文の投稿費用（オープンアクセス）
2017 - 2017

学内競争的資金
若手研究支援
2016 - 2016

学内競争的資金
新任教員研究支援
2015 - 2015