Research On Thermal Characteristics And Heat Dissipation Structure Optimization Of Battery Pack Of Pure Electric Vehicle

In recent years,due to the energy crisis and the deterioration of the natural ecological environment,the automotive sector began to develop new energy vehicles,with the aim of finding clean energy to replace fossil fuels.Pure electric vehicle has become one of the hot new energy vehicles with the advantages of high energy density,large specific energy,environmental protection,pollution-free,recyclable charging and so on.However,because the operating temperature of lithium battery needs to be in a safe range(-25 ~ 45℃)for a long time,and the temperature difference of the battery should be controlled within the safe value(5℃),otherwise there will be thermal runaway problems,resulting in battery spontaneous combustion or explosion and other safety accidents.Therefore,it is very important to design an efficient,stable and safe battery cooling system.Firstly,this paper investigates the market and development status of new energy vehicles at home and abroad,makes a systematic introduction according to different types of new energy vehicles,compares the advantages and disadvantages of different power batteries,and finds that lithium ion batteries become a potential power source for the development of electric vehicles due to their special physical and chemical properties.However,due to the thermal characteristics of lithium ion batteries,the battery thermal management system is needed to control the temperature,and then the focus and difficulty of this paper is put forward,namely,the control of the temperature and temperature difference of the power battery.According to the investigation of the thermal management system of lithium ion battery,it is found that the current thermal management technologies mainly include air cooling,liquid cooling,phase change,heat pipe cooling and other mainstream cooling and cooling technologies.Secondly,according to the cuboid shaped lithium iron phosphate battery as the research object,based on the reaction mechanism and thermal effect theory of single lithium ion battery,the working principle and thermal generating mechanism of lithium iron phosphate battery during charging and discharging are understood,and the thermal reaction phenomenon of the battery during discharging is studied.Then,according to the actual battery,the geometric parameters and internal structure of the battery are obtained,and the thermal physical parameters of the battery are calculated by the weighted average method,which provides theoretical basis and important parameters for the simulation.Thirdly,according to the three conservation laws of mass,momentum and energy,based on the basic theory of heat transfer,the heat transfer problem of the battery is expounded,and the simulation conditions are set.In FLUENT software,based on the same temperature and different discharge ratio condition,the monomer battery and battery module three dimensional transient thermal model simulation,the distribution of temperature field analysis of battery,especially temperature change characteristics of different time,the highest temperature and temperature changing,and the monomer unit,heat significantly promoted,batteries at high discharge rate discharge at radiator cooling measures.From time,as the power battery development in the direction of the large size,high energy density,the surface heat dissipation become mainstream,for the battery module preliminary design a set of surface cooling system,the battery pack with high discharge rate(2 c)discharge,surface plate cooling ways on battery surface heat dissipation,the transient simulation results show that the highest temperature of the battery pack did not meet the design goals,the lowest temperature,temperature difference,need to improve the heat dissipation system and optimization.Finally,to rearrange the battery pack,the direction of the surface plate and the heat source distance is smaller,and the surface plate structure optimization,by using the optimized surface plate,find a relatively reasonable cooling fluid velocity and temperature,to ensure that the cooling effect at the same time,to minimize the energy consumption of the final simulation results fitted to the design requirements.