A Design And Optimization Of Contact-type Battery Cooling System

Due to its high energy density,high voltage,and memory-free advantages,lithiumion batteries are widely used in electric vehicles.However,during use,they generate a large amount of heat.If this heat is not effectively dissipated in a timely manner,it can lead to problems such as battery overheating,shortened lifespan,and reduced safety.Therefore,this paper proposes a new drip liquid cooling system based on a porous outlet pipe to address the heat dissipation problem of lithium-ion power battery modules.Through numerical simulation and experimentation,the heat dissipation performance of the immersed and drip liquid cooling systems under different parameters was compared and studied.Multi-objective optimization was also performed on the droptype liquid cooling system.The main research contents of this paper are as follows:(1)The changes in the internal resistance and entropy coefficient of lithium-ion single battery were experimentally tested using a hybrid pulse test under different environmental temperatures,SOC,and discharge rates.The heat generation model of the battery was obtained by fitting the Bernardi heat generation formula with experimental data for discharge rates of 1C,1.5C,and 2C.The constructed heat generation model was verified through relevant experiments,and the error between the simulation value and experimental value was within 5%,confirming the accuracy of the established heat generation model for single cells.(2)A new drip liquid cooling system based on a porous outlet pipe was designed.The uniformity of the outlet flow of the porous outlet pipe was theoretically calculated and experimentally verified.The cooling performance of a 4-parallel and 7-series battery module was analyzed and tested through simulation and experiment.The results show that the cooling requirements can be met under different cooling liquid flow rates and discharge rates,and the temperature distribution of the battery module is relatively uniform.The experimental test results are consistent with the simulation results.(3)An immersion liquid cooling system model was established and its accuracy was verified through relevant experiments.Based on the established immersion liquid cooling system model and related experiments,the cooling performance of the drip liquid cooling system and the immersion liquid cooling system under different cooling liquid flow rates,discharge rates,and cooling liquid inlet temperatures was compared and analyzed.The comparative analysis results show that when the battery module discharge rate exceeds 1C,the immersion liquid cooling system cannot control the temperature of the battery module within the ideal temperature range,while the drip liquid cooling system can still control the highest temperature and temperature difference of the battery module within 40℃ and 5℃ respectively at a discharge rate of 2C.The immersion liquid cooling system is more susceptible to the size of the cooling liquid flow rate,and at higher cooling liquid inlet temperatures,the drip liquid cooling system exhibits better cooling performance compared to the immersion cooling system.(4)A multi-objective optimization design was conducted on the proposed drip liquid cooling system,with coolant flow rate and spacing between the porous outflow pipes as optimization variables.The optimization aimed to reduce the inlet and outlet pressure drop of the coolant,lower the temperature difference within the battery module,and improve the volumetric energy density of the battery module while meeting the cooling demand.