Cooling Performance Analysis And Optimization Of Lithium-ion Battery For Electric Vehicle

As the main energy storage component of electric vehicles,lithium-ion batteries directly determine the dynamic performance,cruising range and working stability of electric vehicles.During the driving of electric vehicles,lithium-ion batteries will generate a lot of heat when they discharge.It is easy to cause problems such as high temperature and large temperature difference in the battery pack.Moreover,it will cause combustion.High-efficiency battery thermal management systems are of great significance for improving the performance of electric vehicles and power batteries.Based on the theoretical basis of heat transfer and computational fluid dynamics,this paper takes electric vehicle battery pack as the research object.A series of researches on the heat dissipation performance of the battery pack were carried out.The main contents are as follows:Firstly,the heat generation mechanism and heat transfer characteristics of lithium-ion batteries were analyzed.Based on this,the heat generation rate model of the battery was established and its thermal property parameters were calculated as the theoretical basis for subsequent research.Secondly,the lithium-ion battery was tested for internal resistance and temperature rise,and the test data were obtained to study the relationship between internal resistance,SOC and temperature under different working conditions.The finite element thermal model of the LiFePO₄battery was established by the software Fluent combined with the test data.The discharge process was simulated under different working conditions of the battery.The simulation and test results were consistent.The thermal model can reflect the temperature change of the lithium-ion battery effectively.Thirdly,the battery module was taken as the research object,the heat dissipation performance of the liquid-cooled battery module was simulated by the computational fluid dynamics method with different flow channels.From the perspective of heat dissipation performance,flow distribution uniformity and flow channel pressure drop,a comparative analysis was made to determine the optimal structure.For the selected flow channel structure,the effects of the inlet and outlet position,coolant inlet flow rate,coolant temperature,channel's width and channel's height on the heat dissipation performance of the module were investigated.Finally,using the flow channel structure parameters as the experimental factors,the highest temperature and maximum temperature difference of the battery module were used as evaluating indicator.The response surface methodology was used to obtain the flow channel structure optimization scheme,and the optimization effect was verified by simulation.The maximum temperature rise of the optimized battery module decreased by 10.3%.The thermal model of the battery pack was established to optimize the cold plate connection mode.The maximum temperature difference of the optimized pack was reduced by 14.5%and the temperature uniformity of the battery pack was significantly improved.It is found that the flow channel structure parameters in this model have a greater influence on the maximum temperature rise of the battery pack;while the cold plate connection mode has a greater influence on the temperature uniformity of the battery pack.The research method and model structure provided a reference for the heat dissipation structure design of the battery pack in the future.