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6th International Conference on Fluid Mechanics and Industrial Applications, FMIA 2022

作者： Shen, Zhongxiang Gao, Ming Dong, Wuhan Zhang, Lixin Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China

The microlayer present at the bottom of the bubble plays a very important role in heat transfer during nucleation boiling. In this paper, the dynamic characteristics of microlayer at the bottom of boiling bubble in a small channel were studied by laser interferometry method and high speed camera, and the results were compared with pool boiling experiments. The results show that the bubbles have an obvious tendency to slip in the flow boiling. The microlayer interference fringe is deformed and no longer a complete Newtonian ring. By analyzing the thickness distribution of microlayer in different directions in flow boiling and the change of micro-contact angle in the flow direction, it was found that the micro-contact angle in the flow direction became larger with the growth of bubbles. © Published under licence by IOP Publishing Ltd.

关键词： Contact angle

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Electrospinning engineering of gas electrodes for high-performance lithium-gas batteries

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Carbon Energy 2024年第10期6卷 353-398页

作者： Jingzhao Wang Xin Chen Jianan Wang Xiangming Cui Ze Wang Guangpeng Zhang Wei Lyu Maxim Shkunov S.Ravi P.Silva Yaozu Liao Kai Yang Wei Yan State Key Laboratory of Multiphase Flow in Power Engineering Department of Environmental Science and EngineeringSchool of Energy and Power EngineeringXi'an Jiaotong UniversityXi'anChina Advanced Technology Institute University of SurreyGuildfordSurreyUK State Key Laboratory for Modification of Chemical Fibers and Polymer Materials College of Materials Science and EngineeringDonghua UniversityShanghaiChina

Lithium-gas batteries(LGBs)have garnered significant attention due to their impressive high-energy densities and unique gas conversion ***,the practical application of LGBs faces substantial challenges,including sluggish gas conversion kinetics inducing in low-rate performance and high overpotential,along with limited electrochemical reversibility leading to poor cycle *** imperative task is to develop gas electrodes with remarkable catalytic activity,abundant active sites,and exceptional electrochemical ***,a versatile and well-established technique for fabricating fibrous nanomaterials,has been extensively explored in LGB *** this work,we emphasize the critical structure-property for ideal gas electrodes and summarize the advancement of employing electrospun nanofibers(NFs)for performance enhancement in *** elucidating the fundamental principles of LGBs and the electrospinning technique,we focus on the systematic design of electrospun NF-based gas electrodes regarding optimal structural fabrication,catalyst handling and activation,and catalytic site optimization,as well as considerations for large-scale *** demonstrated principles and regulations for electrode design are expected to inspire broad applications in catalyst-based energy applications.

关键词： carbon nanofibers electrocatalyst electrospinning gas electrodes metal-gas batteries

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Numerical study on shell-side shear flow and heat transfer in a spiral wound heat exchanger under onshore/offshore conditions

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APPLIED THERMAL engineering 2025年 267卷

作者： Ren, Yan Guo, Yixin Cai, Weihua Jiang, Yiqiang Wu, Weidong Yang, Yingying Chen, Jie Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China Norhteast Elect Power Univ Sch Energy & Power Engn Jilin Peoples R China Harbin Inst Technol Dept Bldg Thermal Energy Engn Harbin Peoples R China CNOOC Gas & Power Grp Beijing Peoples R China

Given that studies on shell-side shear flow and heat transfer characteristics in spiral wound heat exchangers (SWHEs) used in floating liquefied natural gas (FLNG) systems are still scarce, a mathematical-physical model was established based on the two-fluid thermal phase change model, incorporating a modified mean diameter of the dispersed phase. According to the results under onshore conditions with operating pressure ranging from 0.2 to 0.6 MPa, mass flux ranging from 40 to 100 kg/(m2 & sdot;s), heat flux ranging from 2,000 to 8,000 W/m2, and vapor quality ranging from 0.3 to 0.9, respectively, the shell-side frictional pressure drop gradient increased with decreasing operating pressure and increasing mass flux and vapor quality. The effect of the heat flux was negligible and could be ignored. The offshore conditions significantly increased the proportion of shear flow on the SWHE shell side. Therefore, the effects of the rolling and operating parameters on the shear flow were investigated with rolling amplitudes and periods of 5-15 degrees and 5-15 s, respectively. Consequently, the flow and heat transfer characteristics of the shell-side shear flow exhibited sinusoidal periodic fluctuations owing to the influence of the rolling motion, and their fluctuation periods were approximately equal to the rolling period. Within the allowable operating range, a higher mass flux could not only effectively resist the influence of the rolling motion but also maintain the heat exchanger performance at a higher level while delaying the adverse drying of the heat exchange tube wall. Additionally, Aunan's correlation was proven to exhibit good adaptability for calculating the frictional pressure drop gradient of shear flow under both onshore and offshore conditions. These results provide guidance for the design and operation of FLNG SWHEs.

关键词： Shear flow Thermal phase change model flow and heat transfer Shell side FLNG

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Optimization of Thermal Conductivity of Alumina-Filled Composites by Numerical Simulations

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Journal of Thermal Science 2023年第4期32卷 1569-1582页

作者： LI Shikun LIU Bin JIA Xiao XU Min ZONG Ruoyu LIU Guohua HUAI Xiulan Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power UniversityBeijing102206China Institute of Engineering Thermophysics Chinese Academy of SciencesBeijing100190China Nanjing Institute of Future Energy System Nanjing211135China

Understanding the correlation between the physical features of composite components and thermal conductive pathway is beneficial to optimizing the overall heat-transfer ***,we conduct numerical simulation to investigate the thermal conductivity and heat flux distributions of alumina(Al_(2)O_(3))-filled *** finite element model was verified by both experimental data and theoretical *** crucial factors include the influence of the interface thermal resistance,the intrinsic thermal conductivity of the matrix and Al_(2)O_(3)filler,and the size effect of Al_(2)O_(3)fillers were *** single Al_(2)O_(3)-filled composites,the results indicate that increasing the intrinsic thermal conductivity of the matrix is conductive to bridge the Al_(2)O_(3)pathway along heat-transfer direction,but there are very limited contributions by enhancing the intrinsic thermal conductivity of Al_(2)O_(3)filler,tuning the size of Al_(2)O_(3)filler,and reducing the interface thermal *** introducing the multiscale fillers,it is found that the high thermal conductivity can be achieved by regulating their size matching *** the optimal binary ratio of 70:30(40µm:15µm)and ternary ratio of 55:35:10(40µm:15µm:10µm),the heat-conduction network presents the dominant skeleton of large-sized filler and the bridging branch of small-sized fillers features,which facilitates the formation of a complete and continuous thermal conductive *** study gives a practical guidance for the thermal conductive design of Al_(2)O_(3)-filled composites.

关键词： optimization size matching effect thermal conductivity numerical simulation multiscale Al_(2)O_(3)filler

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Chemical looping dry reforming of waste glycerol coupled with thermochemical water splitting cycle by mesoporous Fe2O3-Co3O4/CeO2 oxygen carriers

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CHEMICAL engineering JOURNAL 2024年 493卷

作者： Wu, Kai Dou, Binlin Zhang, Hua Wang, Yadong Chen, Haisheng Xu, Yujie Li, Wei Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Chinese Acad Sci Inst Engn Thermophys Beijing 100190 Peoples R China Zhejiang Univ Dept Energy Engn Hangzhou 310027 Peoples R China

A coupled chemical looping conversion of glycerol and CO 2 with thermochemical water splitting (WS) cycle is substantially researched due to its potential for one-step renewable H 2 and syngas production. The major challenge lies on having good controls of redox reactions of the oxygen carriers (OCs) used and its unusual sensitivity to the changes of the compositions, chemical states and structure, etc. Here, we develop the OCs that consists of Fe 2 O 3 -Co 3 O 4 supported on the mesoporous CeO 2 structure (Fe 2 O 3 -Co 3 O 4 /CeO 2 ), which simultaneously promote glycerol oxidization (GO), dry reforming of glycerol (GDR), and WS processes. The easy migration and activation of lattice oxygen by Fe 2 O 3 -Co 3 O 4 /CeO 2 greatly improved the GO and GDR to produce syngas at the first step, and the pure H 2 production by the reduced Fe 2 O 3 -Co 3 O 4 /CeO 2 achieved excellent WS and oxygen storage at 750 degree celsius. The low -content Fe dopant in the OC presented a beneficial effect on the anti -sintering performance, and increase of Co -doping indicated a high activity to WS as well as enhanced GDR. The Fe 2 O 3 - Co 3 O 4 /CeO 2 with 7:5:10 of Co: Fe: Ce molar ratio presented the highest glycerol and CO 2 conversions and the highest H 2 yield, also illustrated the excellent activity and stability in 40 consecutive redox cycles.

关键词： Chemical looping conversion of glycerol and CO2 Glycerol oxidization (GO) Glycerol dry reforming (GDR) Water splitting (WS) Oxygen carriers (OCs)

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heat transfer Enhancement of Partially Serrated Twisted Finned Tube Bank

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heat transfer engineering 2023年第21-22期44卷 2079-2090页

作者： Wei, Hongyu Cong, Tao Jiang, Chen Zhou, Wenxue Bai, Bofeng Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Peoples R China Shanghai Lanbin Petrochem Equipment Co Ltd Shanghai Peoples R China Lanzhou Heat Transfer & Energy Saving Engn & Techn Lanzhou Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Due to the large thermal resistance on the airside of the air-cooled heat exchangers, it is necessary to improve heat transfer performance and reduce flow resistance by improving the fin structure. In this paper, partially serrated finned tube bank was proposed and numerically investigated. The experimental system of finned tube bank was built to verify the correctness of the numerical simulation. The finned tube bank is twisted and serrated on the windward side to enhance heat transfer. Moreover, the non-grooved sector region on the leeward side reduces the flow resistance and improves the temperature uniformity of the fins. The effects of fin twisting of the windward side and non-grooving angle of the leeward side were explored. Nusselt number and friction factor decrease as the leeward non-grooving sector region increases. The correlations of Nusselt number and friction factor were derived based on the simulation results of partially serrated twisted finned tube banks with 120 degrees non-grooving region on the leeward side. Nusselt number, friction factor and comprehensive heat transfer coefficient of partially serrated twisted finned tube bank are 13.3%, 13.0% and 10.5% higher than that of annular finned tube bank with Reynolds number from 6200 to 20,600, respectively.

关键词： Nusselt number

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Interaction between Neighboring Supercritical Water Molecules and Density Fluctuation by Molecular Dynamics Simulations

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Journal of Thermal Science 2022年第3期31卷 907-922页

作者： WANG Yan XU Jinliang MA Xiaojing Key Laboratory of Condition Monitoring and Control for Power Plant Equipment of Ministry of Education North China Electric Power UniversityBeijing102206China Beijing Key Laboratory of Multiphase Flow and Heat Transfer North China Electric Power UniversityBeijing102206China

Supercritical water(scW)is important for various engineering *** structure and distribution of sc W is key to dominate the related processes and ***,scW is investigated using molecular dynamics(MD)simulation with controlled pressure and *** oscillation is observed to occur in a 1 nm thickness bin,indicating mass exchange of particles across the bin *** show that the low density scW behaves strong *** analysis of system density fluctuations is performed by square root error and maximum structure factor,demonstrating the agreement between the two *** scW molecules are tightly gathered to form“liquid island”locally,but are very sparse in other regions,which are similar to the gas-liquid mixture in subcritical pressure.A target molecule is tracked to plot 3D displacements and rotating angles,with the former indicating large amplitude ballistic(diffusing)motion and small amplitude oscillation,and the latter displaying two scales of angle *** translation and rotating motion are related to hydrogen bond break up and *** low density scW behaves isolated molecules with few combinations of hydrogen bonds between molecules,while the high density scW behaves more combinations of molecules via hydrogen *** two scales motion is expected to influence thermal/chemical process in supercritical state,deepening the fundamental understanding of scW structure.

关键词： supercritical water molecular dynamics density hydrogen bond translation and rotating motion

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Study on the leakage in water-injected twin-screw steam compressor

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PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART E-JOURNAL OF PROCESS MECHANICAL engineering 2023年第6期237卷 2244-2256页

作者： Tian, Yafen Yuan, Hao Geng, Yanting Zhao, Zhaorui Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai Peoples R China Shanghai Marine Diesel Engine Res Inst Dept Compressor Shanghai Peoples R China

Steam compressor shows great energy-saving potential in mechanical vapor compression and high-temperature heat pump systems. However, leakage remains a huge problem for compressor performance improvement and design optimization. In this article, a thermodynamic model with detailed leakage flow model was developed for the working process in water-injected twin-screw compressor. Altogether, leakage in different paths and heat and mass transfer between injected liquid and compressed vapor were considered. Compared with experimental results, the accuracy of predicted efficiency is within +/- 5% for all tested operating conditions. In the validated model, leakage flow in five leakage paths and their effects on compressor efficiency was investigated. Results indicate that leakage can reduce volumetric efficiency by up to 50.2%, while the injected water liquid vaporization can improve volumetric efficiency by 7.9% at 5000 r center dot min(-1). The leakage through contact line (CL), tip sealing (TS) line, and discharge end face (DE) show the most important impact on compressor efficiency, while the leakage through blow hole (BH) and suction end face (SE) has little impact on compressor efficiency. Compared with zero leakage under certain conditions, the reduction of volumetric efficiency caused by CL, TS line, and DE can reach up to 22.4%, 20.4%, and 12.7%, respectively. Reducing clearances of the above three leakage paths can efficiently improve the performance of steam compressor, especially for CL.

关键词： Liquid water injection twin-screw steam compressor leakage heat and mass transfer performance optimization

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Impact of optimized gas-liquid separator on temperature and frost distribution in electric vehicle heat pump AC

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APPLIED THERMAL engineering 2024年第PartB期248卷

作者： Li, Kang Miao, Yanming Xia, Dingyu Liu, Ni Zhang, Hua Dou, Binlin He, Qize Zhao, Yugang Li, Chao Mohtaram, Soheil Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Key Lab Multiphase Flow & Heat Transfer Shanghai P Shanghai 200093 Peoples R China Shanghai Fire Res Inst MEM Shanghai 200032 Peoples R China Invest Design & Res Inst Co Ltd Shanghai 200080 Peoples R China

In the context of low temperatures, the outdoor evaporator surface in an electric vehicle's heat pump air conditioning system tends to accumulate frost unevenly. This uneven frosting occurs due to the varying heat exchange capacity of the refrigerant's two phases within the evaporator. Any reduction in the heat exchanger's capacity would lead to a negative impact on system performance. To address these challenges, this study introduces a gas-liquid separator placed in front of the outdoor evaporator. The aim was to enhance both the outdoor evaporator's performance and the overall system efficiency while investigating frost formation and heat distribution in the outdoor evaporator within a heat pump air conditioning system. The research outcomes demonstrate that the gas-liquid separator can effectively enhance evaporating pressure by regulating the opening degree of the gas-phase bypass valve. Optimal performance is achieved with the gas-phase branch bypass valve set between 20% and 30%, ensuring a stable operational condition and higher evaporating pressure. Moreover, the incorporation of a gas-liquid separator could lead to significant improvements in system performance, with increases of 6.9% in heat capacity and 7.4% in COP observed. Additionally, this enhancement extends to the outlet air temperature, showing improvements ranging from 3.6% to 11.2%.

关键词： Electric vehicle Gas-liquid separator heat pump system heat exchange characteristics heat pump performance

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Optimal evaporation/condensation temperature determination and experimental validation for electric vehicles

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APPLIED THERMAL engineering 2024年 252卷

作者： Li, Kang Guo, Huan Zhou, Xuejin Chen, Hongming Liu, Ni Zhang, Hua Dou, Binlin He, Qize Tian, Yafen Tu, Ran Su, Lin Mohtaram, Soheil Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Key Lab Multiphase Flow & Heat Transfer Shanghai P Shanghai 200093 Peoples R China Huaqiao Univ Coll Mech Engn & Automat Xiamen 361021 Peoples R China MEM Shanghai Fire Res Inst Shanghai 200032 Peoples R China

This study explores the potential of heat pump air conditioning systems in enhancing the driving range of electric vehicles (EVs) by optimizing evaporator and condenser temperatures to achieve improved system performance and efficiency. A novel methodology is introduced to determine the optimal temperatures for evaporation and condensation within such a system, seamlessly integrated with a primary return system. The validity of this approach is substantiated through rigorous experimental validation. Under New European Driving Cycle (NEDC) conditions, the heat pump air conditioning system demonstrates superior performance and reduced energy consumption, with optimal evaporator temperatures ranging from-2 degrees C to 2 degrees C and condenser temperatures between 57.1 degrees C and 61.8 degrees C during summer. Winter conditions are optimized with evaporator temperatures from-16 degrees C to-12 degrees C and condenser temperatures between 42.4 degrees C and 48.8 degrees C. Additional experiments were conducted to validate system performance in both cooling and heating modes. The results highlight a close alignment between the theoretical model for the primary return air system and actual performance, with less than a 10 % discrepancy in calculated outlet temperatures compared to experimental data across various operating conditions. This correlation validates the theoretical model's capacity to accurately reflect real-world system behavior.

关键词： Electric vehicle heat pump air conditioning system Evaporation temperature Air outlet temperature Experimental verification of performance

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