Numerical Studies On The Thermal Management Of Lithium-ion Battery Pack For Electric Vehicle Application

Battery is one of the key parts of the electric vehicles, which has a great effect on the performance of the electric vehicles. The thermal management on the battery pack can prolong its service time as well as improve its performance.This thesis presents the numerical simulation results on the air cooled battery pack based on the cylindrical lithium ion battery, Li FePO4. Firstly, the heat generation and thermal model of the battery was built-up, and the numerical results in terms of it were successfully validated by the experimental results. Secondly, the numerical study was conducted on the air cooled battery pack, and the optimum air distribution method was obtained under the condition that the small deviation of the temperatures for all the battery modules in the battery pack can be achieved. The details are as the following:(1)Reorganize the study of heat diffusion and heat radiation after reading related thesis. Discuss major functions of battery thermal management system and analyze advantage and disadvantage of different heat-transfer agents.(2)After comparing the safety of different materials, the 26650LiFePO4 battery becomes the topic of this thesis. This thesis confirm the acceptable temperature range and state the inner constitution, reaction process, heat production item and heat diffusion feature, which become the foundation for future study on heat radiation.(3)Establish Li FePO4 battery three-dimensional imitation model and study the change of temperature under different conditions. Finding out that the temperature depends on working electric current. Reducing surrounding temperature or increasing convection will help heat radiation. Apart from these, this thesis compare monomer heat analysis basing on the test, finding that imitation results match test data.(4)Comparing imitation results of general Air cooled Battery and test results, it matches, which confirm imitation can exactly describe heat reaction of battery. The thesis design many new types of heat radiation installation in order to solve difference between Air cooled Battery. This thesis wrote down that the biggest difference of temperature and standard deviation is less than general air cooled battery. When the flow in entrance is increased, the biggest difference of temperature and standard deviation reduce first and then increase. Therefore, the system must have the best program to distribute the flow.(5)This thesis design methods to improve the new type of battery thermal management system by control the amount of entrance, choice of entrance location and entrance structure. When there are three entrances, the dip angle of other three entrance will be 60o、60o and 60 o. At that time, the temperature of the system will be the best. This thesis set up diversion board in front entrance in 2、3and back end in 6、7,which is the best program to control temperature difference.