Simulation Analysis Of Thermal Management Of Lithium Battery For Electric Vehicle

In recent years,with increasingly prominent trouble of energy shortage and environmental pollution,new energy vehicles get more and more attention.As the core of new energy vehicles,power batteries will produce a lot of heat in the car running.If effective thermal management measures can't be taken,there will be lots of problems,such as excessive battery temperature,unbalanced temperature distribution between cells and so on,which will not only affect the battery life and power performance,and even lead to serious battery burning or explosion,bringing a lot of security risks.In this paper,the basic structure of the battery and mechanism of heat production were researched.Taking a lithium iron phosphate battery as an example,using Bernardi calculation model to get the formula for calculating the heat generation rate of the whole battery in discharge process.Then UG was used to establish three-dimensional models of battery cell and pack,and ANSYS was used to simulate.The comparison of the simulation results with experimental results showed that the three-dimensional lithium-ion battery thermal efficiency model and the thermal calculation model are validated.Then taking battery maximum temperature and maximum temperature difference as the monitoring objectives,the thermal characteristics of the battery pack are analyzed and compared by different cooling methods(box ventilation cooling,phase change material cooling,fin cooling,composite cooling of fins and phase change materials).The results showed that:(1)Box ventilation cooling could significantly reduce the maximum and minimum temperature of the battery pack,but leaded to a extraordinary temperature difference.Increasing the wind speed at the air inlet,the battery group maximum temperature and maximum temperature difference had decreased.When opening a hole in the box where the heat is easily accumulation,the battery temperature distribution was improved,but the temperature uniformity was still poor.(2)Large current for a long time,simply using phase change material cooling is not easy to meet the cooling needs of the battery pack.When the material completely melted,the battery heat dissipation would be hindered.Therefore the phase change material cooling of such a structural model is not suitable for use in a continuously operating battery pack.(3)Finned natural convection cooling could only meet the thermal management requirements of the battery pack in small rate discharge.Large discharge rate of the battery pack required to use the fin cooling ventilation,and the temperature of battery pack could be controlled better with greater wind speed.On the basis of meeting the cooling needs of the battery pack,the fin could also be open to ventilate to reduce the weight of the system,.(4)When the phase change material was located in the space between the battery and the adjacent fins,the combined cooling of the fin and the phase change material could control the maximum temperature and the maximum temperature difference of the battery pack to 45?and 5?,respectively.When the phase change material was placed between the batteries and mounted on both sides of the copper sheets,the cooling effect was poor.Increasing the phase change material length,the maximum temperature difference of the battery pack had not been very good improvement.