Cooling Performance Investigation And Parameter Optimization Of Liquid Cooling System With Mini-Channel For Li-ion Battery

With the increasing severity of energy shortage and environmental deterioration,electric vehicles have been developed more rapidly.As the main energy storage component and power source of electric vehicles,the performance of lithium-ion batteries is very important for the vehicle.A large amount of heat released during operation will make the temperature of the batteries rise sharply,and the life and capacity of the batteries will decline rapidly.Excessive heat even leads to accidents such as deflagration.Large temperature difference within a battery cell also affects the accuracy of state of charge(SOC)estimation.Therefore,it is necessary to maintain the temperature at an appropriate range.Aiming at solving the high temperature problem of battery during high C-rate discharge,a liquid-cooled battery thermal management system based on a minichannel cold plate is established in this work.The numerical simulation method is used to analyze the cooling effect of the system and the response surface method(RSM)is used to optimize the channel structure.The main research work are as follows:(1)The research status of battery thermal management is summarized,and the working principle of lithium ion battery,the mechanism of heat generation and transfer are analyzed,in addition,the battery heat generation model is selected.The hybrid pulse power characteristic(HPPC)method is used to measure the internal resistance of the battery at different discharge rates,temperatures and SOC.Then,the battery heat generation model is obtained by coupling resistance and the Bernardi model,and the equivalent physical calculation method is used to obtain the battery thermal physical parameters.A single battery simulation model is established and the result shows that the error is within 5% at different discharge rates,and the model is accurate.(2)A liquid cooling system based on mini-channel cold plates is established,and the cooling effect of cold plate with 4 types of channel is simulated,which includes common and optimized forms.The temperature of the battery module and the cooling hydraulic pressure drop are compared.The results show that the series-parallel channel form has better performance,which can lower the temperature of the battery module,improve the temperature uniformity,and reduce the coolant pressure drop.(3)Based on the series-parallel channel cold plate,the effects of different mass flow rate,inlet temperature and ambient temperature on the cooling effect are analyzed.The results show that the increase of the mass flow rate improves the cooling effect,but be limited after increasing the mass flow rate to 5 g/s;Lower coolant temperature can keep the temperature of battery module at a lower level,but increase the maximum temperature difference and the power consumption of the cooling system;The influence of the ambient temperature on the battery module decreases with the discharge time under different ambient temperatures,and tends to be a certain value after 300 s of discharge.(4)The influence of series-parallel channel parameters on cooling performance is analyzed,and the parameters of channel are optimized.The effect of a single factor with different bottom margin of the inlet channel,width and height on the temperature of the battery is analyzed.The results show that the increase in the bottom margin reduces the standard deviation of the battery module temperature,but the maximum temperature and temperature difference first decrease and then increase;The increase in the width reduces the average temperature of the battery module,but the maximum temperature and temperature difference will increase slightly after the width exceeds a certain value;Increasing the height resulted in an adverse effect on the temperature performance.Based on the single factor analysis,three variables of the bottom margin of channel,the width of channel at the series and parallel area are selected to constitute the response surface,and the interactive effects of different factors on the temperature and coolant pressure drop is analyzed.In addition,the parameters of channel are optimized,the optimization results show that the maximum temperature rise,maximum temperature difference of battery module and the pressure drop of coolant are reduced by 8.4%,15.5% and 34.8% respectively.