Analysis And Optimization Of Cooling Features Of Electric Vehicle Power Battery Pack

With the extensive exploration of carbon,fuel and natgas in different countries,the resource shortage and natural disaster have had a significant influence on human everyday life.However,electric cars do not have waste gas discharge in the use phase,and have tremendous benefits of saving energy and reduction of pollution comparing with conventional fuel cars.As one of the biggest parts of electric cars,the temperature management of battery has never been a better solution,which limits the rapid advances of electric cars.Excessive temperature will decline the capacity and life of the battery,and in grave cases,even lead to spontaneous fire and other phenomena,affecting the security of the car.Lithium-ion battery is the most extensive in the market for electric cars,and in order to realize its great function,it is vital to ensure that it operates at a stable temperature field.Thus,this paper takes this battery as the argument,and studies the cooling features of lithium-ion battery pack through thematic analysis and CFD 3D emulation,which offers theoretical bases and data support for efficiently using lithium-ion battery and system energy usage.The key study elements are as following:Firstly,the heat generation and heat loss of Li-ion batteries are fully studied,the needed data for battery modeling are obtained,and the heat generation ratios of the batteries at 0.5C,1C,1.5C and 2C discharge ratios are obtained by the heat generation model.The battery temperature scope under diverse discharge ratios is emulated by Fluent,And the precision of the model was tested by contrast with the test.The results indicate that the battery temperature at 2C discharge rate is exceeding the safe working range and needs to be dissipated.Secondly,the simplified battery model was used to create a battery pack consisting of six single cells connected in parallel,and three different flow path structures were designed and placed under the battery pack,and the cooling effect of the three flow path structures was compared by simulation at 2C discharge rate.The data show that the serial flow path is the best flow path configuration,and the highest temperature of the battery is 44.41℃ and the biggest temperature gap is 12.86℃,but it cannot meet the design demands of the highest temperature less than 40℃and the biggest temperature gap less than 5℃,so the liquid cooling system needs to be improved.The improvement is to add an equal liquid cooling plate above the battery pack,and to compare the different flow directions of coolant and different flow path shapes in the upper and lower cooling plates.The outcome indicates that the upper and lower coolant flow direction is opposite and the flow channel shape is square has better cooling effect,the highest temperature and biggest temperature gap of the battery meet the design demands.Then,univariate analysis was used to study the effects of coolant flow rate,coolant temperature,runner edge length and runner rotation number on the maximum battery temperature,maximum temperature difference and fluid pressure drop.According to the orthogonal test,the impact level of every factor on the highest temperature of the battery,the largest temperature gap and the fluid pressure drop were gained.At this time,the highest battery temperature is 28.05℃,the largest temperature gap is 4.16℃,and the fluid pressure drop is 401.4pa,compared with the improved liquid cooling system,the highest battery temperature dropped by 17.9%,the largest temperature gap decreased by 6.7%,and the fluid pressure drop declined by 31.1%.Finally,in order to study more fully and more easily the impact of test factors on the highest temperature,largest temperature gap of the battery and fluid pressure drop,the model is approximated by using the design-of-test sampling in Isight,and the forecast is optimized by the multi-objective algorithm NSGA-Ⅱ,and the forecast results are contrasted with the emulation results.The data show that the mistakes are lower than 5%,and the highest battery temperature dropped by 6.3%,the largest temperature gap decreased by 6.2%,and the cooling hydraulic drop declined by 80.3%comparing with the modified battery.