Heat Dissipation Characteristics And Optimization Design Of Forced Air Cooling For Lithium Ion Battery Of Electric Vehicle

With the rapid development of electric vehicles,as the energy supply device of electric vehicles,it is very important to study the battery and its performance.In the process of battery charging and discharging,a lot of heat is generated,and the performance of the battery is related to its own temperature,which makes how to heat the battery become a topic worthy of attention.In terms of battery cooling,three common cooling methods are: air cooling,liquid cooling and refrigerant direct cooling.In terms of heat dissipation efficiency,liquid cooling and refrigerant direct cooling are obviously better than air cooling,but simple structure and low cost are the main advantages of air cooling.Because the specific heat capacity of air is smaller and the convective heat transfer coefficient of air is lower than that of liquid,it becomes the main factor that restricts the ability of air cooling.How to design the structure of the battery pack to improve the maximum temperature and temperature uniformity of the battery pack under the same air cooling conditions is very important.Therefore,by combining theoretical analysis with simulation experiment,the battery pack composed of 12 21700 lithium-ion power battery cells is taken as the research object,and the influence of air inlet size,area ratio of inlet and outlet,horizontal eccentricity and vertical eccentricity of inlet and outlet on the air cooling and heat dissipation effect of the battery pack is studied by using orthogonal test method,and the interaction between various factors is analyzed The cooling structure of the pool group is optimized.The main contents are as follows:（1）Firstly,through the pre-processing software ICEM and the simulation software FLUENT,the model of 21700 Li ion power battery was built,and the constant current discharge was simulated.Then,the relationship between different discharge rate and convective heat transfer coefficient and the heat dissipation effect of the cell was obtained.（2）Then,a battery pack model based on 12 21700 lithium-ion cells was built.Through single factor analysis,the relationship between the arrangement of battery cells,air inlet wind speed,air inlet size,area ratio of inlet and outlet,horizontal eccentricity and vertical eccentricity of inlet and outlet and the heat dissipation effect of battery pack was obtained.（3）Taking the size of air inlet,area ratio of inlet and outlet,horizontal eccentricity and vertical eccentricity of inlet and outlet as design variables,the structure of battery pack was optimized by using orthogonal test method,range analysis method and variance analysis method to reduce the maximum temperature and temperature difference.Finally,we not only know the order of the influence of the four factors and the first-order interaction between them on the maximum temperature and the maximum temperature difference in the battery pack,but also get the optimal model:the size of the air inlet is 5cm,the area ratio of the inlet and outlet is 1.5,the horizontal eccentricity of the inlet and outlet is 0° and the vertical eccentricity is-20° of the battery pack.