| As the only power source of electric vehicle,the performance of lithium-ion power battery directly affects the overall performance of electric vehicle,and the temperature is the main factor affecting the overall performance of battery,so efficient thermal management system is the key to high performance and long life of lithium-ion battery.In this paper,R134 a evaporation phase transformation is used to control the temperature of the battery pack,and numerical calculation method is used to simulate the heat transfer characteristics of the refrigerant phase transformation process.A scheme is proposed to optimize the cold plate structure of the system by changing the layout and section shape of the refrigerant flow channel,and improve system cooling performance.The main contents of this paper are as follows:(1)According to the working principle of lithium battery,the mechanism of heat generation and heat transfer is analyzed.Based on the theoretical knowledge of phase change heat dissipation,the mass heat transfer term of the phase change process is established,UDF phase change program is compiled,and the source term is added to simulate the phase change process of refrigerant.(2)Establish the thermal simulation model of battery and determine the thermal physical parameters of battery.Based on the HPPC test method,the dynamic relationship between the internal resistance of the battery and the ambient temperature and SOC is studied,and the input heat source of each part of the battery is determined.The simulation analysis of the battery discharge temperature under different discharge rate and different ambient temperature is carried out.The results show that the temperature of the battery is too high under the condition of high rate discharge or high temperature,so it is necessary to dissipate the heat of battery.(3)The simulation model of the cooling system of the battery module is established,the vehicle model is built by CRUISE,the HWFET condition is established,the dynamic current of the vehicle is simulated and analyzed,and the heat source input of the system is determined.The heat transfer characteristics of the battery phase change cooling system is simulated from different refrigerant inlet temperature and different mass flow.The simulation results was analyzed from the aspects of temperature field and gas content distribution of the battery,and the optimization scheme of refrigerant flow channel layout and section shape is proposed.The results show that the optimized cooling system model can improve the uniformity of temperature distribution of the battery.(4)Under the same working condition,simulation and analysis of cooling performance of battery cooling system before and after optimization with 50% glycol aqueous solution as cooling medium,and compared with R134 a phase change reaction cooling results.The results show that the maximum temperature and temperature difference of phase change cooling battery are lower than that of liquid cooling,which can ensure the battery consistency. |
