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

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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Numerical sensitivity study on nucleation bulk tension factor of non-equilibrium condensation model

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JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY 2023年第2期37卷 977-985页

作者： Chen, Eryun Fu, Shiyin Yang, Ailing Peng, Shuxue Zhao, Gaiping 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 Univ Shanghai Sci & Technol Sch Med Instruments & Food Engn Shanghai 200093 Peoples R China

The spontaneous condensation process of steam has obvious non-equilibrium characteristics, the accurate prediction of which is challenging. In this work, the nucleation bulk tension factor (NBTF) is used to modify the droplet surface tension for improving the accuracy in the calculation of the steam condensation flow. The non-equilibrium condensation processes in two nozzles are numerically simulated using a surface tension model with NBTF. The influence of NBTF on the simulation accuracy of the steam spontaneous condensation flow is analyzed. The correlation among the optimal value of NBTF, steam expansion rate and inlet parameters is emphatically studied. The obtained results show that the optimum value of NBTF is not sensitive to the change in the steam expansion rate under the same working conditions. It has no significant correlation with the total inlet temperature, but has a significant positive correlation with the total inlet pressure. Based on the numerical results, a cubic polynomial regression model between the optimal NBTF and total inlet pressure is obtained, the reliability of which is further verified by numerical calculation of a wet steam two-phase flow in the Bakhtar plane cascade. These results can provide a reference for determination of the optimum NBTF in wet steam condensation nucleation models.

关键词： NBTF Nucleation rate Non-equilibrium condensation Wet steam Planar cascade

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An investigation on dehumidification and heat transfer characteristics of a minichannel heat exchanger for heat pump system of electric vehicles

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INTERNATIONAL JOURNAL OF ENERGY RESEARCH 2022年第13期46卷 18294-18311页

作者： Yu, Jun Su, Lin Li, Kang Fang, Yidong Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Key Lab Multiphase Flow & Heat Transfer Shanghai Shanghai Peoples R China

heat pump systems for electric vehicles must assure the system's energy efficiency and the comfort and safety of the passenger cabin. This project aims to analyze the dehumidification and heat transfer characteristics of a heat exchanger through experiments and theoretical modeling. In this paper, a parallel flow minichannel heat exchanger was experimentally and theoretically studied under various operating conditions. A distributed parameter model considering heat and mass transfer was developed and utilized to predict the heat exchanger's dehumidification and heat transfer characteristics. The results reveal that, with a fixed inlet air relative humidity and a low refrigerant mass flow rate, the dehumidification rate (DHR) increases and subsequently declines with the increasing inlet airflow. When the inlet air relative humidity and inlet airflow are constant, the lower the refrigerant mass flow rate, the greater the enthalpy humidity ratio. As the inlet airflow increases, the refrigerant mass flow rate and inlet air relative humidity stay constant, and the enthalpy humidity ratio rises. The proposed model's predictions match the experimental data rather well. The predicted heat transfer rates (HTRs) and DHRs have absolute errors of less than 4% and 10%, respectively, compared with the experimental results. Under various airflows for the OM3 operating conditions, the distributions of HTR and DHR demonstrate that the HTR percentage is lowest in flow path IV, no dehumidification is conducted in flow path IV, and the DHR percentage is largest in flow path II. The proposed model may be employed to assess the dehumidification and heat transfer performance of heat exchangers and optimize the design of heat exchangers in similar heat pump systems. Highlights Construct a test bench for the dehumidification and heat transfer performance evaluation of a minichannel evaporator. Analyze and discuss the dehumidification and heat transfer characteristics of the evaporator under

关键词： dehumidification rate enthalpy humidity ratio heat transfer rate Minichannel heat exchanger

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Numerical study on the performance of an interventional microaxial blood pump with superhydrophobic surface

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PHYSICS OF FLUIDS 2025年第1期37卷

作者： Geng, Xuesong Li, Chengcheng Ma, Jianying Qiu, Huihe Cui, Guomin Wang, Ying Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200039 Peoples R China Fudan Univ Zhongshan Hosp Shanghai Inst Cardiovasc Dis Dept Cardiol Shanghai 200032 Peoples R China Hong Kong Univ Sci & Technol Guangzhou Thrust Sustainable Energy & Environm Guangzhou Peoples R China

Unlike traditional blood pumps, interventional microaxial blood pumps are characterized by their small size, high rotational speed, and narrow gap between the impeller rim and pump housing. These features result in an unstable flow field within the pump, leading to high shear stress regions that can cause hemolysis. To improve the hydraulic efficiency of the blood pump and mitigate blood damage, this paper proposes an interventional microaxial blood pump with a superhydrophobic surface. The finite element method was used to model the axial blood pump and arterial flow field, with Navier slip boundary conditions applied to the impeller and outflow structure walls, simulating a slip length of 50 mu m to represent the superhydrophobic surface characteristics. A combination of numerical simulations and hydraulic experiments was employed to evaluate the effects of the superhydrophobic surface on the pump's hydraulic performance and hemolysis characteristics. The results indicated that the designed interventional microaxial blood pump model demonstrated good blood compatibility. The superhydrophobic surface significantly reduced shear stress at the design point, with wall shear stress in the impeller and outflow structure regions decreasing by approximately 8.09%. Hydraulic efficiency increased by approximately 12.16%, and the hemolysis index decreased by about 12.60%. These findings provide valuable support for further optimization of microaxial blood pumps.

关键词： Shear stress

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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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EFFECTS OF FLUID-SOLID WALL heat transfer ON THE ACHIEVABLE SIMULATED SOLID WALL CONTACT ANGLES IN PSEUDOPOTENTIAL LATTICE BOLTZMANN METHOD WITH DIFFERENT GHOST FLUID LAYERS CONSTRUCTED AT A SOLID WALL

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heat transfer RESEARCH 2022年第8期53卷 21-33页

作者： Wang, Dongmin Univ Shanghai Sci & Technol Sch Energy & Power Engn Key Lab Multiphase Flow & Heat Transfer Shanghai Shanghai 200093 Peoples R China Suzhou Univ Sci & Technol Jiangsu Key Lab Micro & Nano Heat Fluid Flow Tech Suzhou 215009 Peoples R China

In the pseudopotential multiphase lattice Boltzmann method, a ghost fluid layer is often constructed at a solid wall to simulate wall wettability under isothermal conditions. But the effects of fluid-solidwall heat transfer on the achievable simulated heating solid wall contact angle remain unclear, with different types of ghost fluid layer constructed at the solid wall. A two-dimensional semicircular liquid droplet on a heating solid wall evolving to the equilibrium contact angle has been simulated by the pseudopotential multiphase lattice Boltzmann method. It is found that with the ghost fluid layer constructed by the duplicated method, the fluid-solid wall heat transfer leads to droplet shape distortion and drastic increase of spurious velocity at any fluid-solid interaction strength G(s), resulting in the algorithm collapse and a failure in implementing any heating solid wall contact angles. With the ghost fluid layer constructed by constant fluid density, the fluid-solid wall heat transfer leads to solid wall contact angle slightly increasing and narrowing down the achievable simulated solid wall contact angle to the range from 103 degrees to 155 degrees. With the ghost fluid layer constructed by local fluid density, the fluid-solid wall heat transfer leads to the heating solid wall contact angle largely decreasing and narrowing down the achievable simulated heating solid wall contact angle to the range from 14 degrees to 25 degrees.

关键词： contact angle ghost fluid layer heat transfer pseudopotential multiphase lattice Boltzmann method

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Life Cycle Assessment Analysis and Comparison of 1000 MW S-CO_(2)Coal Fired power Plant and 1000 MW USC Water-Steam Coal-Fired power Plant

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Journal of Thermal Science 2022年第2期31卷 463-484页

作者： LI Mingjia WANG Ge XU Jinliang NI Jingwei SUN Enhui Key Laboratory of Thermo-Fluid Science and Engineering of Ministry of Education School of Energy&Power EngineeringXi’an Jiaotong UniversityXi’an 710049China Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power UniversityBeijing 102206China

The objective of this paper is to understand the benefits that one can achieve for large-scale supercritical CO_(2)(S-CO_(2))coal-fired power *** aspects of energy environment and economy of 1000 MW S-CO_(2)coal-fired power generation system and 1000 MW ultra-supercritical(USC)water-steam Rankine cycle coal-fired power generation system are analyzed and compared at the similar main vapor parameters,by adopting the neural network genetic algorithm and life cycle assessment(LCA)***-objective optimization of the 1000 MW S-CO_(2)coal-fired power generation system is further carried *** power generation efficiency,environmental impact load,and investment recovery period are adopted as the objective *** main vapor parameters of temperature and pressure are set as the decision *** results are concluded as ***,the total energy consumption of the S-CO_(2)coal-fired power generation system is 10.48 MJ/k Wh and the energy payback ratio is 34.37%.The performance is superior to the USC coal-fired power generation ***,the resource depletion index of the S-CO_(2)coal-fired power generation system is 4.38μPRchina,90,which is lower than that of the USC coal-fired power generation system,and the resource consumption is ***,the environmental impact load of the S-CO_(2)coal-fired power generation system is 0.742 m PEchina,90,which is less than that of the USC coal-fired power generation system,0.783 m PEchina,*** all environmental impact types,human toxicity potential HTP and global warming potential GWP account for the most environmental ***,the investment cost of the S-CO_(2)coal-fired power generation system is generally less than that of the USC coal-fired power generation system because the cost of the S-CO_(2)turbine is only half of the cost of the steam *** optimal turbine inlet temperature T_(5)becomes smaller,and the optimal turbine inlet pressure is unchanged at 622.082°C/30 MPa.

关键词： S-CO_(2)power plant ultra-supercritical water-steam Rankine cycle power plant life cycle assessment energy efficiency environment impact economic performance

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Lanthanide-Functionalized Carbon Quantum Dot-Based Dual-Emission Hydrogels for Multilevel Anti-counterfeiting and Repeatable Information Loading

ACS APPLIED OPTICAL MATERIALS

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ACS APPLIED OPTICAL MATERIALS 2024年第5期2卷 714-724页

作者： Li, Ying Xu, Chen Wang, Zi-Long Lu, Jia-Zhen Shang, Yi-Chen Wang, Mi-Tang Univ Shanghai Sci & Technol Sch Mat & Chem Shanghai 200093 Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China

With the increasing development of advanced optical anti-counterfeiting technologies, it is essential to develop a simple, fast fluorescent material with anti-counterfeiting properties. In this study, we successfully prepared a single-emission CDs-based hydrogel (CDs@PVA-Alg) by introducing carbon dots (CDs) into the interpenetrating network of sodium alginate (Alg) and poly(vinyl alcohol) (PVA) via hydrogen bonding and further cross-linking them with Ln3+ ions to obtain dual-emission Ln-functionalized CDs-based hydrogels (Ln@CDs@PVA-Alg) (Ln = Tb, Eu). By freeze-thawing and ion-exchange methods, the resulting hydrogels displayed extraordinary mechanical properties and significant photoluminescent properties. On one hand, the CDs@PVA-Alg hydrogel demonstrated distinct fluorescence responses to Ln3+ ions. On the other hand, the fluorescence of Tb@CDs@PVA-Alg was quenched by H+ ions and restored in OH- solution. Furthermore, the mechanism of the above fluorescence response was explored in depth, which was further used to create an excellent optical anti-counterfeiting platform that can be utilized for multilevel anti-counterfeiting and repeatable information loading. By changing the excited light and chemical reagent, these materials enable versatile operations such as encryption, decryption, decoding, loading, and unloading of a wide range of information. This study not only supplies a representative example of the fabrication of dual-emitting Ln@CDs@PVA-Alg hydrogels but also investigates their potential application as smart polymeric gels with multifunctionality.

关键词： carbon quantum dots hydrogel films fluorescencesensing mechanical toughness anti-counterfeiting

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Dynamic analysis of rolling ball bearing-rotor based on a new improved model

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SN APPLIED SCIENCES 2022年第6期4卷 1-12页

作者： Nan, Guofang Jiang, Shan Yu, Dengliang Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China

Dynamic analysis for a bearing-rotor system with the imbalance and the asymmetric gap is conducted in this paper. A new improved analytical model overall considering the gap, the varying compliance vibration and the time-dependent unbalanced force is established, especially the new model is more accurate and closer to reality by abandoning the assumption of the traditional model that the three center points of the inner ring, the outer ring and the rolling ball are collinear. More general vibration characteristics are described and the calculation results based on the new model are more universal than those based on the traditional model. The comparison of the calculation result between the improved model and the traditional model shows that the phase difference for the two results is obviously different from each other, the dominant frequency has no obvious difference between the two models and the amplitudes have somewhat difference. The parametric excitation vibration induced by the varying compliance force of the rolling ball on the inner ring-rotor is analyzed and then the influences of the rotating speed, the gap, the eccentricity and the mass of the rotor on the nonlinear responses are studied and some important conclusions are drawn. As the speed increases, the VC frequency gradually loses its domination of the frequency spectrum, and the rotational speed frequency and its combined frequency with the VC frequency dominate the vibration. The bearing-rotor system is susceptible to the variations of the rotational speed, the gap, the eccentricity and the mass of the rotor in certain ranges;the parameters can make the system in a relatively stable, stable and unstable state;the system shows the complex dynamic behaviors such as the periodical vibration, the quasi-periodic vibration, the chaotic motion and the jumping phenomenon, the bifurcation, sudden change. The research is significant for the quantitative calculation of the dynamic response for parameter desi

关键词： Bearings Gap Improved model Nonlinear Varying compliance

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Experimental study of electronic expansion valve opening on the performance of electric vehicle heat pump system at different compressor speeds

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INTERNATIONAL JOURNAL OF REFRIGERATION 2023年 149卷 94-104页

作者： Wang, Fengxian Wu, Weidong Zhu, Qundong Li, Kun Zhang, Hua 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 Univ Shanghai Sci & Technol Inst Refrigerat & Cryogen Engn 516 Jungong Rd Shanghai 200093 Peoples R China

The good matching of the electronic expansion valve (EXV) opening and compressor speed in an electric vehicle heat pump air conditioning system is significant for improving the whole system performance. The matching of EXV opening and compressor speed and its effect on system performance was experimentally investigated and analyzed. The results showed that at various compressor speeds, the condensing pressure increased and the evaporating pressure decreased to a small extent with the decrease of EXV opening, thus increasing the pressure ratio. The condensing pressure had a jump phenomenon at a specific EXV opening, and the corresponding jump opening was different at each compressor speed. The COP reached the optimal values of 2.4, 2.6, and 2.1 at the EXV opening of 110, 100, 90 steps, respectively, due to the synergistic effect between compressor speed and EXV opening. Moreover, it was found that the changing trend of COP was consistent with that of condenser outlet temperature. The compressor speed and EXV opening had a more significant impact on condensing pressure than evaporating pressure. The influence of compressor speed on each performance parameter was greater than that of EXV opening, while the EXV opening significantly influenced the subcooling degree. Under different compressor speed conditions, changing the single adjustment step of EXV according to the influence of EXV on each parameter can realize the rapid and accurate control of the heat pump system performance, which can provide a reference for the formulation of relevant control strategies and the reduction of the system energy consumption.

关键词： heat pump Electric vehicle EXV opening Compressor speed Control strategies

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