Research On Thermal Management Of Electric Vehicle Lithium-ion Battery Based On Liquid Cooling

Today's social energy crisis and environmental pollution are getting more and more serious,electric vehicles have been widely used for their unique advantages,and power batteries are the most important ones in the"three powers"of electric vehicles.Performance and longevity are directly affected by the power battery.Excessively high or too low temperature can not make the battery work normally.In severe cases,thermal runaway will occur and an explosion will occur.Therefore,it is necessary to design an effective thermal management scheme to control the battery pack temperature within an appropriate range.In this paper,a square lithium battery of a company's pure electric logistics vehicle is based on its battery box structure,and a combination of theoretical analysis,computer simulation and experimental verification is used to design an effective battery thermal management solution.The battery pack is heated in a low temperature environment,and the battery pack is dissipated in a high temperature environment,so that the battery pack can always work at a suitable temperature to achieve the purpose of battery thermal management.The main research contents and conclusions of this paper are as follows:(1)The basic principle and structure of lithium-ion battery are analyzed.At the same time,the heat generation and heat dissipation mechanism of the battery under charge and discharge conditions are analyzed.The physical property parameters of the LP2714897lithium battery used in this paper are calculated and determined.(2)A three-dimensional model of single cells was established,and carried out computer numerical simulation of single cells under different discharge rates,different convection conditions and different ambient temperatures,and obtained temperature cloud and battery surface temperature rise under different conditions.The temperature rise test of the single cell was designed,and the temperature rise test of the single cell was completed.The experimental results were analyzed and compared with the simulation results.The temperature difference between the two was within 1?,which proved the rationality of the simulation.(3)According to the size of the battery box structure,the other type of lithium battery is arranged and arranged in the box;a complete thermal management scheme is designed,including the temperature control structure design and its arrangement in the box,and the pump,Calculation and selection of heat exchangers,radiators and heaters.(4)Finally,the flow field and thermal field of the battery pack was simulate.Firstly,the flow field simulation of the whole flow field of the system is carried out,and the system structure is optimized according to the results of the flow field simulation.The inlet and outlet are adjusted to the middle position,and the simulation is performed again.The result is ideal,and the flow velocity difference in each branch pipe It is reduced to 0.26m/s,and the flow velocity difference in the temperature control plate is reduced to 0.03m/s,which can be regarded as uniform splitting.Secondly,based on the condition of uniform shunt,a single temperature control board and battery model are established.Under the high temperature condition and the low temperature condition,the heat transfer model is analyzed by thermal simulation.According to the obtained temperature rise curve of the monitoring point and1800s It can be seen from the temperature cloud diagram that the thermal management system designed in this paper can well control the battery temperature within a suitable range,and the temperature difference can be less than 5?.