Study On The Heat Dissipation Performance Of Power Battery Liquid Cooling Thermal Management System Of Electric Vehicle Based On Flat Heat Pipe

With the development of traditional automobile industry,the contradiction between energy supply and demand and environmental pollution are becoming more and more serious.Developing electric vehicles to improve the energy structure and decrease the environment pollution becomes the important development direction in China.As the power source of electric vehicles,the performance and safety of power battery directly determines the performance and safety of the electric vehicles.The performance and safety of power batteries are closely related to the temperature.And the battery working performance and life will decline quickly when the temperature is too high or too low.When the temperature exceeds the limited value,it will cause fire and explosion and other dangerous accidents,seriously threatening the lives of passengers.Therefore,efficient thermal management of power battery system is very important.The structure characteristics,principle of heat generation and heat transfer of lithium-ion batteries as well as the fluid mechanics referred to the heat dissipation performance analysis of the liquid cooling thermal management system of power batteries based on flat heat pipe were analyzed in this paper.The lithium-ion battery model was established with the reference of 38 Ah prismatic ternary lithium-ion battery.And the model was valided by experiment.The deviation between the simulation data and experimental data was less than 5% which means the model is correct and reliable.Based on a single battery module,the temperature distribution characteristics was analyzed when the battery module is solely by liquid cooling with CFD method.And this provided a reference for the verification of the optimized thermal management system performance.At the same time,according to the structure characteristics of the original battery module,the flat heat pipes are arranged between the lithium-ion batteries in the battery module to optimize the temperature distribution uniformity.And the design can keep the space utilization and energy density.The influences of the number and width of the flat heat pipe on the maximum temperature and maximum temperature difference of the power battery system were analyzed in detail.Finally,it was determined that the best combination mode is the number of flat heat pipes is 11 and the width is equal to the width of the batteries.In this mode,the maximum temperature difference of the power battery system is 44.5% lower than that without the flat heat pipe.Based on the optimal combination of the flat heat pipe and the liquid cooling thermal management system on a single battery module,a power battery system design was proposed.The effects of different discharge rates,different cooling liquid inlet flow rate and different cooling liquid inlet temperature on the temperature uniformity of the power battery system were analyzed.The results show that the temperature uniformity will be better with bigger inlet flow and lower inlet temperature.