Research On Design And Optimization Of Liquid Cooling And Heat Dissipation Of Lithium Ion Battery Module Of Electric Vehicle

As the main power source of electric vehicles,the performance of lithium-ion battery(LIB)directly determines the power and safety of electric vehicles.LIBs exist in the form of battery packs in electric cars,and they will continuously emit heat during the process of working.If these heat cannot be released in time,problems such as temperature excessive and difference in the battery packs will easily occur,and even lead to the explosion and fire accidents in serious cases of electric cars.Therefore,the thermal management system which can effectively control the battery temperature is of great significance for the performance of electric vehicles.In this thesis,the battery module is taken as the research object,and the liquid cooling and heat dissipation characteristics of the battery module are studied by means of simulation and numerical analysis.The main contents are as following:Firstly,the basic structure and reaction principle of LIBs are described.Through the analysis of the heat generation mechanism and heat transfer characteristics of the battery,the three-dimensional thermal model of a single LIB is established and the thermal physical parameters of the battery core is calculated.Secondly,The values of internal resistance and entropy heat coefficient of 30 Ah LIB under different conditions are obtained through experiments.The temperature rise of the battery at different discharge rates is simulated by Fluent and compared with the data collected from the temperature rise test to verify the accuracy of the thermal model.Thirdly,The liquid cooling and heat dissipation model of the battery module is established,and two noval runner structures are proposed according to the common characteristics of serpentine runner and parallel runner.Based on three fundamental equations of mass,momentum and energy conservation in fluid mechanics,the performance of the battery modules in terms of heat dissipation effect and inlet/outlet pressure difference under these structures is compared through fluent software simulation,and the optimal flow channel structure is determined.The heat dissipation characteristics of the module are studied in terms of inlet and outlet position,coolant flow rate,initial coolant temperature and runner structure parameters.Finally,taking the runner structure parameters as the optimization object,the maximum temperature difference of the module and the maximum temperature difference of the module as the evaluation index,combines with the response surface optimization method,a multi-group test scheme is designed and the optimal runner structure parameters are obtained by variance analysis of the simulation results.The accuracy and reliability of the optimized model are verified by simulation,and the maximum temperature difference of the optimized battery module decreases by 10%.