Research And Optimization Of Liquid Cooling System For Lithium Battery Pack Of Electric Vehicle

Facing the increasingly serious environmental pollution problem and energy shortage problem,the development of pure electric vehicles is the general trend.As the only power source for electric vehicles,power battery is one of bottlenecks that restricts the development of electric vehicles.Since lithium-ion batteries are very sensitive to temperature,too high or too low temperatures can seriously affect their performance,and the closely placed single cells in the battery pack can easily cause a series of phenomena such as thermal accumulation and thermal overlap,and so on.Therefore,thermal management of the power battery is crucial.In this paper,we mainly used the method of CFD(computational fluid dynamics simulation analysis),from the perspective of engineering application,to establish gap-free battery modules and normal gap battery modules,and adopt a conservative scheme to thermally manage the battery modules.In order to improve the performance and thermal safety of electric vehicles,a reasonable cooling system scheme is proposed and studied and optimized.The specific research contents of this paper are as follows:1.The structure,working principle,heat generation mechanism,heat transfer theory and temperature of lithium battery are studied and analyzed.The calculation and estimation of the heat generation rate and thermophysical parameters of lithium-ion batteries are studied.2.The battery cell and module models were built using CATIA software.Using AMESim one-dimensional simulation and Fluent three-dimensional simulation to simulate the temperature rise of the single lithium battery under different discharge rates and that of the single lithium battery under different ambient temperatures,and compared with the experimental data to verify the correctness of the model.Fluent software was used to simulate the temperature rise of the battery module under natural convection,which verified the necessity of thermal management of the battery pack.The method of battery thermal management was selected through AMESim software,and two schemes of the heat dissipation were compared for the external fluid flow circulation connection of the battery pack,which provided a direction for future research.3.Designed the liquid cooling thermal management system of the battery module,conducted single factor variable heat dissipation from the structure of three different cooling baseplates,coolant inlet temperature and inlet speed and used orthogonal optimization test analysis to synthesize the best heat dissipation plan.4.Using Advisor software to simulate and analyze three typical operating conditions of electric vehicles,it is believed that the discharge rate of the power battery will not exceed 1C during most of the trip.Finally,a steady-state liquid-cooled heat dissipation simulation of thebattery module was carried out under the discharge rate of 1C to verify that the feasibility of the liquid-cooled solution can achieve the expected effect.