Design And Optimization Of Liquid-cooled Heat Dissipation Structure For Pure Electric Vehicle Lithium-ion Battery

Battery temperature is one of the most direct factors that affect the performance of pure electric vehicles:too low temperature,the battery capacity drops significantly,and the cruising range is reduced;too high temperature may cause a series of safety accidents such as battery thermal runaway.Studies have found that the safe working temperature range of power batteries is 25??40?,and the maximum temperature difference should be less than 5?.Therefore,an efficient battery cooling system is particularly important.This paper combines simulation analysis and experimental verification,taking lithium-ion batteries as the research object,and separately researches the optimization design of liquid cooling plates with double-layer fractal microchannels and bionic structure liquid cooling plates.The specific research is as follows:1.Focusing on the heat generation mechanism of lithium-ion batteries,the temperature gradient problem of the traditional single-layer liquid cooling plate structure is analyzed,and a liquid cooling plate structure with double-layer microchannels is designed.Studies have shown that increasing the coolant flow can effectively reduce the maximum temperature and temperature difference of the liquid cold plate,but an excessive flow will increase the energy consumption of the cooling pump and bring greater load to the battery.Reducing the temperature of the coolant can also greatly reduce the maximum temperature of the liquid cooling plate,but the temperature difference is basically unchanged.With other conditions unchanged,five different outer tube turning radii were selected,and the structure of the double-layer microchannel liquid cooling plate was optimized.The results show that the improved liquid cooling plate has improved heat dissipation performance and reduced power consumption.2.The lithium-ion battery is discharged at a rate of 2 C,and the same working conditions are selected.The optimized model and the traditional single-channel model are compared.The results show that the optimized model has a better heat dissipation effect,and the inlet and outlet pressures are poor.The maximum temperature is 27.9?,which is 0.5?lower than the single-channel liquid cooling plate;the temperature difference is 3.8?,which is a decrease of 1.9?,a decrease of 33.3%;the inlet and outlet pressure difference drops to 10798.9 Pa,a decrease of83.25%;With low cooling pump consumption,the heat dissipation performance can better meet the requirements of the battery working environment.3.According to the data obtained from the simulation of the double-layer microchannel liquid cooling plate,the relationship between the multi-target and the temperature of the liquid cooling plate is analyzed,and the temperature prediction model is established using STATA software,and the temperature regression equation is obtained.In order to verify the accuracy of the simulation results,an experimental verification device was designed.The results show that the error between the experimental and simulation results is maintained within 8%,the simulation of the cooling effect of the liquid cooling plate is accurate,and the cooling effect of the liquid cooling plate is obvious.4.According to the relevant knowledge of bionics,according to the human blood vessel model,a liquid cooling plate with bionic blood vessel structure is designed using the method of quasi-similar fractal.Under three different discharges of 1 C,2 C and 3 C,the FLUENT software was used to study the tube distance(A1,A2)at the coolant outlet,the coolant flow rate,the thickness of the liquid cooling plate,the turning radius R of the tube in the channel,etc.The influence of factors on heat dissipation performance.The results show that the tube distance(A1,A2),plate thickness and inner tube turning radius R have a significant impact on the heat dissipation effect of the liquid cooling plate,especially under 3C discharge.When A1=6 mm,A2=8 mm,plate thickness 4 mm,inner tube turning radius 8 mm,the maximum temperature(T_max)of the liquid cooling plate is 305.03 K(31.88?),and the temperature difference(?T)is 4.10?.At this time,the structure is more compact and the system energy consumption is lower while meeting the requirements of the safe working temperature of the power battery,which is more conducive to the standardization and practical application of the power battery liquid cooling plate.5.Imitating the human blood vessel model,the cooling liquid outlet is optimized with a variable width,and the heat dissipation performance of the liquid cooling plate has been greatly improved.Increasing the inlet mass flow can improve the heat dissipation capacity,but it will consume more energy consumption of the cooling system.Considering the selection of a flow rate of 0.020 kg/s,the best liquid cooling plate heat dissipation performance can be achieved.For 3 C discharge,a verification experiment was carried out.The results show that the error between the experiment and simulation results is maintained within 8.4%,the simulation of the cooling effect of the liquid cooling plate is accurate,and the cooling effect of the liquid cooling plate is obvious.