| As the main storage system of the electric vehicle,the power battery would make heat build-up under continuous large discharge rate in the process of driving.The cycle life and capacity of the battery decline sharply when the operating temperature is too high,which affects the stable performance of electric vehicles.And continuous heat accumulation may even lead to the explosion and fire.Therefore,the cooling technology of automotive power battery is very important for the safety and stability of electric vehicles.This paper focuses on the heat dissipation structure and performance optimization of lithium battery module and mainly carries out the following researches:(1)The structure and thermogenesis mechanism of the lithium-ion battery were described.The internal resistance of cells under different ambient temperature and SOC was investigated.The thermal characteristic model of the cell was established,and the temperature field of the cell under different discharge rates was analyzed,and the temperature rise of the battery at 0.5C,1C,2C discharge rate was tested respectively.The reliability of the thermal model of the cell was verified by comparing the results of simulation and experiment.(2)The heat dissipation model of the battery module based on the cooling plate was established,and then the single variable control simulation was used to analyze and compare the effect of pipe diameter,cooling plate thickness and pipe spacing distance on liquid-cooled battery module.Based on the results of single factor simulation,orthogonal test analysis was arranged to optimize the structure of the cooling plate taking the maximum temperature and temperature difference of the battery module as the comprehensive evaluation index.(3)Based on the optimized design results of the cooling plate,the influence of cooling medium,coolant temperature and flow rate on the heat dissipation performance of the liquid-cooled battery module were analyzed.The heat dissipation performance test bench of the liquid-cooled battery module system was built.The feasibility of the simulation model was verified through the analysis of the heat transfer performance of the battery module by the experiment.(4)The lower coolant temperature would reduce the temperature rise of the battery effectively,while it led to the temperature difference between the cells increasing.Therefore,the cooling method of coolant temperature decreasing step by step was adopted,and the influence of different cooling slopes on the heat dissipation performance of battery module was analyzed.In order to improve the temperature control of the battery module under high temperature condition,the response surface method was used to study the cooling influencing factors and their interactions on the temperature distribution of the battery module.The optimal condition of temperature distribution of the battery module was obtained with comprehensive analysis,and the reliability of the result of the factor combination obtained by response surface optimization was verified by simulation analysis based on Fluent.The research on structure optimization design and performance analysis of battery module system based on cooling plate is beneficial to improve the heat dissipation performance of battery thermal management system.The research method in this paper can provide technical basis and guidance for the design of battery cooling system. |
