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Frosting characteristics and performance impact on R744 heat pump systems for electric vehicles at low ambient temperatures: An experimental approach

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APPLIED THERMAL engineering 2025年 266卷

作者： Li, Kang Kong, Fanyue Liu, Ni Zhang, Hua Dou, Binlin Li, Chao He, Qize Tian, Yafen Tu, Ran Mohtaram, Soheil Zhou, Xuejin Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P 516 Jun Gong Rd Shanghai 200093 Peoples R China Invest Design & Res Inst Co Ltd Shanghai 200080 Peoples R China Shanghai Fire Res Inst MEM Shanghai 200032 Peoples R China Huaqiao Univ Coll Mech Engn & Automat Xiamen 361021 Fujian Peoples R China

With global warming and the depletion of fossil fuels, electric vehicles have emerged. Although their carbon dioxide heat pump systems are environmentally friendly, they face the problem of frosting on outdoor heat exchangers. Previous studies have mainly focused on the internal factors of heat exchangers or specific operating conditions, with limited exploration of frosting behavior in electric vehicles under complex operating conditions, especially in supercritical high-pressure environments of carbon dioxide electric vehicles. This study builds an experimental platform for a carbon dioxide electric vehicle heat pump system, using an infrared thermal imager to capture accurate data on outdoor heat exchanger temperature and frost development. Different environmental temperatures and compressor speeds are set at high humidity levels of 85-95% to study the distribution of frost layer growth in outdoor heat exchangers under different operating conditions. The study also introduced FCR to analyze the changes in heat pump performance parameters in different FCR regions. Finally, under the same environmental temperature, humidity, and speed conditions, the frosting characteristics of R744 and R134a heat pump systems were compared, and the impact of frosting on them was analyzed. The results indicate that in high humidity environments, lower ambient temperatures and higher rotational speeds increase frost coverage. When FCR exceeds 40%, the suction pressure of the compressor significantly decreases, the heating capacity of the system decreases by 26.01% to 31.08%, and the COP decreases by 21.59% to 29.69%. Regardless of the compressor speed, the COP decreases by about 21% after frosting. Under similar conditions, R134a heat exchanger has more severe frosting than R744, which has a greater impact on the suction pressure of R134a compressor. However, frosting reduces the heating capacity of both systems by about 30%.

关键词： Electric vehicles Outdoor heat exchanger Frost formation CO2 heat pump system

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A novel horizontal gas-liquid pipe separator for wet gas based on the phase-isolation

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CHEMICAL engineering RESEARCH & DESIGN 2022年 178卷 315-327页

作者： Yang, Yang Ha, Wen Zhang, Hong Zhang, Chao Wang, Ying Zhang, Xingkai Wang, Dong 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 200093 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Yangtze Univ Pet Engn Coll Wuhan 430100 Peoples R China

This paper proposes a novel horizontal gas-liquid pipe separator with a compact structure based on the phase-isolation. In the separator, the gas-liquid two-phase flow is firstly isolated as a swirling annular flow by a swirler, where gas core and liquid film spiral and flow forward in parallel. Based on the flow characteristics of the swirling liquid film, a downward tangential liquid extraction channel is designed, which is tangent to the swirl trajectory of the liquid film. Then the swirling liquid film can be directly separated by falling into the downward tangential channel under the combined action of its kinetic energy and gravity. On the basis of this structure, the inner thread on the wall, different lengths of liquid extraction channel and tangential gas return channel are designed individually to study their effect on the separation efficiency. Experiments were carried out to investigate the separation performance of the separator. The results show that when the superficial velocity of gas reaches 20 m/s, the separation efficiency can be higher than 94% with the superficial velocity of liquid in a large range of 0.02-0.264 m/s. The design of inner thread is beneficial for separation when the liquid film has a certain thickness. The length of liquid extraction channel has an opposite influence on separation efficiency at low gas velocity and high gas velocity. The gas return flow channel deteriorates the separation performance for the reason that the returning gas will carry a large number of liquid droplets into the main pipe. (c) 2021 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

关键词： Gas-liquid two-phase flow Separation Phase-isolation Pipe separator

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Transient simulation of SO2 absorption into water in a bubbling reactor

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JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH PART A-TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL engineering 2023年第9期58卷 811-824页

作者： Cai, Yuyang Wang, Zhen Liu, Dunyu Chen, Jun Jin, Jing Qin, Qi Liu, Ke Hu, Haixiang Li, Sijie Shi, Huancong Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China Zhejiang Univ Huzhou Inst Huzhou Peoples R China Univ Regina Clean Energy Technol Res & Innovat Ctr Regina SK Canada

A bubbling reactor is an important type of gas scrubber to reduce SO2 emissions in maritime shipping. Both experiments and simulations were conducted to study the relationship between the periodic gas bubbling process and SO2 concentration at the outlet of the reactor, and the entrainment of liquid droplets on SO2 absorption. The accuracy of the model was verified by comparing the bubble size, the depth of bubbles injected into the water, and the SO2 concentration obtained in both experiments and simulations. The gas bubbling process is accompanied by bubble formation, rise, and collapse. The gas bubbling period is affected by the disturbance of the liquid level. The period of the SO2 concentration at the outlet of the gas bubbling reactor is smaller than that at the gas jar outlet which acts as the gas buffering region. The amounts of water carried out of the bubbling reactor by the gas bubbling process increase with the gas flow rates. The droplets and liquid film in the gas jar and the connecting tube play an important role in the absorption of SO2. This study encourages more research to reduce the fluctuation of SO2 concentration and consider droplet entrainment in the design of bubbling reactors.

关键词： Multi-fluid VOF model bubbling reactor SO2 absorption mass transfer model periodicity of gas bubbling >

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Effect of Operation Parameters on the Thermal Characteristics in a Planar Solid Oxide Fuel Cell

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Journal of Thermal Science 2024年第5期33卷 1974-1989页

作者： WANG Mingyuan WANG Ke WANG Yongqing CHEN Jiangshuai AN Bo TU Shantung School of Mechanics and Safety Engineering Zhengzhou UniversityZhengzhou 450001China Key Laboratory of Process Heat Transfer and Energy Saving of Henan Province Zhengzhou UniversityZhengzhou 450002China School of Mechanical and Power Engineering Zhengzhou UniversityZhengzhou 450001China Key Laboratory of Pressure Systems and Safety(MOE) East China University of Science&TechnologyShanghai 200237China

Effective operation strategies in the solid oxide fuel cell(SOFC)can adjust the spatial distribution of temperature gradient favoring the long-term *** investigate the effects of different operating conditions on the thermal behavior inside SOFC,a three-dimensional model is developed in this *** model is verified by comparing it with the experimental *** heat generation rate and its variation under different operating conditions are *** combined effects of operating voltage and gas temperature are considered to be the key factor influencing the temperature *** to the original case,the temperature of SOFC decreases by 21.4 K when the fuel velocity reaches 5 m/*** the maximum temperature gradient increases by21.2%.Meanwhile,higher fuel velocities can eliminate about 32%of the area with higher temperature *** when the oxidant velocity reaches 7.5 m/s,the peak temperature gradient effectively decreases by 16.59%.Simultaneous adjustment of the oxidant and fuel velocities can effectively reduce the peak temperature gradient and increase the safety *** effects of operation conditions on the temperature gradient of the cell are clarified in this study,which can be a reference for further research on the reliability of SOFCs.

关键词： SOFC heat generation temperature gradient distribution heat source thermal behavior

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Influence of lubricating oil circulation characteristics on the performance of electric vehicle heat pump system under low temperature conditions

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APPLIED THERMAL engineering 2024年第PartB期236卷

作者： Li, Kang Kong, Fanyue Luo, Shuxian Liu, Ni Zhang, Hua Dou, Binlin Zhao, Yugang Zhou, Xuejin Tu, Ran Su, Lin He, Qize 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 Pan Asia Tech Automot Ctr Co Ltd Shanghai 201201 Peoples R China Shanghai Fire Res Inst MEM Shanghai 200093 Peoples R China Huaqiao Univ Coll Mech Engn & Automat Xiamen 361021 Fujian Peoples R China

Electric vehicles frequently employ heat pump systems for winter heating. In winter low-temperature environments, the viscosity of lubricating oil increases, forming an oil film as the refrigerant enters the heat exchanger, consequently impacting the heat transfer efficiency and overall performance of the heat pump system. This paper presents the design and implementation of an experimental heat pump system tailored for electric vehicles. The experimental setup incorporates a specialized device for lubricating oil sampling and an assessment methodology for evaluating heat pump functionality. Under a range of low-temperature conditions, the system underwent comprehensive testing, enabling a detailed analysis and synthesis of the flow characteristics and the influence of lubricating oil within both the heat pump system and the heat exchanger. The results reveal that the oil circulation rate is directly affected by the compressor oil charge, and maintaining the oil circulation rate within the range of 3 %-4 % results in a peak COP of the system. When the ambient temperature is 0 degree celsius and the oil filling volume is 200 g, the oil circulation rate is 3.87 %, and the COP can reach 1.93. In addition, as the oil retention in the evaporator increases by 15.67 g, the COP value decreases by 21 %. Similarly, the increase in oil retention in the condenser from 2.43 g to 6.25 g resulted in a corresponding decrease in heat transfer capacity of 0.07 kW/K, leading to an overall deterioration of the system's performance.

关键词： Electric vehicle Oil retention heat pump system Oil circulation rate heat pump performance

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Enhancing Vertical-Axis Tidal Turbines with Strategic Superhydrophobic Surfaces for Optimized Aerodynamic and Self-Starting Performances

SSRN

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SSRN 2024年

作者： Yin, Dawei Sun, Jinjing School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Shanghai Key Laboratory of Power Energy in Multiphase Flow and Heat Transfer Shanghai200093 China

As observation and research on nature deepen, bionic and hydrophobic surface drag reduction are gaining increasing popularity among researchers. The application of bionic principles and hydrophobic surface technologies in the field of fluid dynamics has opened up new avenues for enhancing the performance of various engineering systems, including vertical-axis tidal turbines (VATTs). By mimicking the natural mechanisms observed in certain species, such as the lotus effect, researchers have been able to develop superhydrophobic surfaces (SHS) that significantly reduce drag in fluid ***, SHS have been applied uniformly across the entire surface of an airfoil. However, this study takes a more nuanced approach by investigating the impact of SHS application at different positions on the airfoil. Through numerical simulations, the study explores how varying the distribution of SHS can influence the power coefficient (Cp), a key performance metric for VATTs . The findings from the study are quite revealing. At a tip speed ratio (TSR) of 1.68, the study observes that applying SHS to 30% of the chord length near the leading edge of the airfoil yields the maximum relative power coefficient benefit, with an increase of up to 34.8%. This suggests that strategic placement of SHS can lead to significant performance improvements without the need for uniform application, which could potentially reduce material costs and maintenance requirements. Moreover, the study also finds that applying SHS only on the inner surface of the VATT can result in a 32% increase in the power coefficient. This indicates that the inner side of the airfoil, which experiences the higher pressure side of the fluid flow, is particularly sensitive to the drag reduction effects of SHS. The leading edge of the airfoil is another critical area where SHS application can have a substantial impact. The leading edge is the first point of contact between the airfoil and the fluid, and any reduc

关键词： Drag reduction

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Insights on CDI parametric controls and dependencies using gloabal sensitivity analysis

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SEPARATION AND PURIFICATION TECHNOLOGY 2025年第Part8期354卷

作者： Qin, Huai Fang, Fang Mao, Yunfeng Xu, Longqian Wu, Deli Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Zhejiang Prov Ind EP Design & Res Inst Co Ltd Shangyu 310013 Zhejiang Peoples R China Tongji Univ Coll Environm Sci & Engn State Key Lab Pollut Control & Resources Reuse Shanghai 200092 Peoples R China Vanderbilt Univ Dept Civil & Environm Engn Nashville TN 37235 USA

Capacitive deionization (CDI) emerges as a promising desalination technology due to its high energy efficiency and potential for energy recovery. Its performance improvement and application extension highly require understanding how variations in multiple input parameters, as well as their interactions, lead to variations in output, which is not straightforward in the complex system of CDI. In this work we use the extended Fourier amplitude sensitivity test (eFAST) method to conduct a global sensitivity analysis (GSA) in order to examine the effects of several parameters, including material properties, operating conditions, and ionic properties, on the energy consumption and salt removal efficiency of CDIs. The research reveals that high capacitance and efficient mass transfer are crucial for CDI advancement, with a trade-off between desalination rate and energy efficiency. The interplay between input parameters is revealed by factorial design and GSA, which show that no single parameter alone determines salt adsorption capacity but that feedwater salt concentration and current density are important when considering both individual and coupled effects. The study suggests that the specific application and feedwater characteristics should be taken into consideration when deciding between the CC and CV modes of desalination. While CC mode excels in water production and energy efficiency for high salinity feedwater pretreatment, CV mode is better at treating low salinity waterr. The comprehensive parametric analysis provides valuable insights into optimizing CDI design and operating conditions to balance desalination capacity and energy efficiency.

关键词： Capacitive deionization Mass transfer model Global sensitivity analysis Constant current mode Constant voltage mode

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Study on the Three-Dimensional flow Control of Two-Phase flow Around a Cylinder by an Attached Cylinder

SSRN

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SSRN 2023年

作者： Xia, Yizhan Hu, Yu Huang, Shengxian Wang, Ying Shanghai key laboratory of multiphase flow and heat transfer of power engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China

Enhancing the separation of flow, shedding of vortices, and sediment deposition around blunt bodies, particularly in cylindrical flows within the realm of ocean engineering, emerges as a pivotal safety factor. This study delves into the control of two-phase flow encircling a cylinder using an affixed cylinder under three-dimensional real ocean conditions. Employing the SST turbulence model, a two-dimensional incompressible RANS numerical simulation is performed. Initially, the influence of varying gap ratios between the auxiliary small cylinder and the main cylinder is scrutinized. Subsequently, the impact of attached small cylinders on the flow field surrounding the main cylinder is examined under different particle characteristics. Lastly, employing the UDF function, four small cylinders exhibiting distinct vibration modes are defined, and the numerical simulation investigates the effects of Grain flow on particle flow and distribution in the wake region of the main cylinder. © 2023, The Authors. All rights reserved.

关键词： Cylinders (shapes)

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Exergy Analysis of a Novel Chemical Looping Hydrogen Generation System Integrated with SOFC

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Journal of Thermal Science 2021年第1期30卷 313-323页

作者： ZHANG Xiaosong CHEN Zhewen CHEN Zhenbin LI Jinsong Mechanical and Electrical Engineering College Hainan UniversityHaikou 570228China Beijing Key Laboratory of Multiphase Flow and Heat Transfer North China Electric Power UniversityBeijing 102206China

In this paper,a novel system integrating chemical-looping hydrogen generation(CLH)system and solid oxide fuel cell(SOFC)has been *** new methane-fuelled energy system was investigated with energy balance and exergy *** produces the hydrogen as the fuel of the SOFC,and the Fe O and Fe3O4 are selected as the looping *** heat from the SOFC is absorbed by the CLH and converted to chemical energy through the reduction reaction of *** to the cascade utilization of the fuel between the CLH and SOFC,the net efficiency of this novel system can achieve 62.8%considering CO_(2)separation,more than 10 percentage points higher than a methane reforming fuelled SOFC ***,by using the CLH to produce the hydrogen,the CO_(2)can be recovered without an energy *** the analysis of the graphical exergy,the cascade utilization of waste heat and the high-efficiency hydrogen production is the main reason of high *** novel system also has the advantage of CO_(2)capture without energy penalty,so this combined system is an advantaged method to accomplish the efficient utilization of methane.

关键词： chemical looping fuel cell exergy analysis

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Numerical simulation study of the fluid-structure coupling effects of Karman vortex street on airfoil motion with varying thickness

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OCEAN engineering 2023年第Part2期286卷

作者： Zhou, Zikang Huang, Shengxian Wang, Ying Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai Peoples R China

This paper examines the fluid-structure interaction of rigid and passive motion of airfoils with different thick-nesses in the K ' arm ' an vortex street at low Reynolds numbers through numerical simulations. Five NACA airfoils with varying thicknesses (8%, 12%, 16%, 20%, and 24%) were investigated regarding their fluid-structure interaction in the K ' arm ' an vortex street. These airfoils were positioned downstream along the centerline of a D-shaped cylinder. Employing a six-degree-of-freedom method, their passive motion was simulated, and the motion grid was generated using the elastic deformation method and local grid reconstruction technique. The analysis included examing alterations in the flow field and forces acting upon airfoils of varying thicknesses in both fixed and released states. The outcomes demonstrate that an increase in airfoil thickness amplified the traction force exerted on the airfoil within the K ' arm ' an vortex street, consequently yielding higher lateral force and torque. In the released state, the airfoil exhibited forward motion towards the D-shaped cylinder and deviated from the suction region of the K ' arm ' an vortex street due to the influence of lateral force. The study unveils that airfoils of suitable with appropriate thickness, such as NACA0012, achieved an improved equilib-rium between forward speed and lateral displacement, thereby covering a more extensive forward distance. These findings provide valuable insights for the designing robotic fish that utilize vortex streets under low-flow conditions.

关键词： Numerical simulation Fluid-structure interaction Airfoil thickness Passive motion

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