| The application of electric vehicles has been greatly supported and developed by the government and society for its advantages in energy saving and emission reduction.As the key component of the electric vehicle,the performance of the power battery is obviously influenced by the temperature.The thermal management technology is crucial to the charging performance,reliability,and life of batteries.This dissertation proposes concrete thermal maganement and configuration based on two types of thermal management of batteries.Numerical simulations and experimental investigations are then conducted on the temperature controling performance.The influences of key parameters on the temperature are elucidated.Results verify the validity of the proposed design from the view of heat transfer.The dissertation carries out measurements of the discharge capacity and voltage of commercial square lithium iron phosphate battery with capcity of 20A·h.The results indicate that the temperature possesses a remarkable effect on the discharge capacity and discharge voltage platform;The experiment on HPPC unveils the law of internal electrical resistance and open-circuit voltage altering with the temperature and SOC;While the necessity of thermal management to power battery modules is verified via the experiment on the surface temperature and performance of a single power battery at a high discharging ratio.the heat generation and transfer model of single power battery is established.The heat transfer process of a single cell under 3C discharging condition is simulated by COMSOL Multiphysics.The results show that,1)Under 3C discharging condition,the highest temperature of battery is 57.2℃,the temperature rise rate is about 0.04℃/s;2)The measured temperature is consistent with the simulated one,which indicate the accuracy of the model.The temperature distribution characteristics obtained by the above study and the established model of the single cell heat transfer provide guidance for the design of the follow-up heat management system.This dissertation proposes a liquid-immersing thermal management technology considering both cooling and preheating,which is compared with a typical one with employment of thermotubes.Numerical simulations and experiments are then conducted on the temperature of two types of battery system.The results show that,1)The performance of immersed power battery thermal management system is superior to the performance of the heat pipe based one;2)Immersed power battery thermal management system combines the functions of heating and cooling.After preheating under the condition of-10℃,the power battery module is able to start the electric vehicle.The highest temperature under 3C discharging condition is 37.9℃,and the largest temperature difference is 1.99℃;3)When the battery module temperature is managed by the heat pipe based battery thermal management system,the highest temperature under 3C discharging condition is 37.9℃,and the temperature difference can be controlled 3.3℃;4)The experiment results and simulation results can fit well,confirming the accuracy of calculation model.It shows that the model can be used in the design of this kind of thermal management system. |
