Research On Liquid Cooling System For The 18650 Li-ion Power Battery Module

With the rapid development of electric vehicles in China,the power battery as the core driving force of electric vehicles also ushered in new opportunities.The power lithium ion battery has the advantages of high energy density,long cycle life and no memory effect.However,during the charging and discharging process of a lithium-ion battery,a lot of heat will be generated inside.If the heat dissipation is not timely,especially under special conditions,the lithium ion battery is discharged at a large rate,which will cause a violent electrochemical reaction inside the battery pack,resulting in a decline in battery life and capacity.When the temperature rises to a certain extent,thermal runaway will occur or even thermal disaster accidents.Therefore,effective geothermal management of the battery pack to ensure that the battery runs within a safe temperature range is of great significance for improving the safety of electric vehicles and promoting the rapid development of electric vehicles.Power battery thermal management system is an important part of the battery pack in electric vehicles.It directly affects the service life,cycle and safety performance of the power battery,and is the most important part of the whole vehicle thermal management of electric vehicles.Based on the design and optimization of liquid cooling system of model 18650 lithium ion power battery,the main research contents are as follows:1)The four mainstream battery thermal management technologies are analyzed in detail,;Based on the structure and working principle of lithium ion battery,the heat generation principle of lithium ion power battery is analyzed.At the same time,according to the internal chemical reactions of the battery when it generates heat,the thermal model design of the thermal management system of the power battery and the calculation method of the thermal generation of the power battery are proposed.According to the obtained battery heat production,MATLAB data processing software was used to conduct linear fitting of the relationship between the time and battery temperature of the experimental data,and the thermal power of the ternary 18650 lithium ion battery at discharge rates of 1C,2C and 3C was obtained,providing various basic parameters for the operation of the COMSOL simulation software.2)Taking the 18650 lithium ion battery module as the research object,a liquid cooling system is used to conduct thermal management of the battery module;Analysis of different factors on the battery module maximum temperature and the influence of the maximum temperature difference,including import flow rate,channel number,the influence of the thermal characteristics of dielectric properties of the model of the channel,it is concluded that the highest temperature of the battery is distributed in the center of the battery module,imported velocity have obvious effect on temperature rise,reveals various factors the influence law of temperature changes to the battery module.The results show that when the inlet flow rate is 0.02 m /s and the number of flow channels is 4,the maximum temperature and temperature difference of the battery module are better than other comparative conditions.The maximum temperature was controlled within 55℃,and the maximum temperature difference decreased by 6.2℃.3)Different simulation models are established for the spoiler fins of the liquid cooling pipeline.By analyzing the influence of the size,Angle of attack and layout of the spoiler generator on the flow in the channel,the influence of different Reynolds Numbers on the Nussel number and resistance factor is analyzed.Through a series of studies,the following conclusions are drawn: the ABAB layout and ABBA layout are compared,and the heat transfer performance of ABBA layout is better than that of ABAB(998 < Re < 5996);The effects of different angles of attack on heat transfer performance and resistance factors were compared and studied.Under the condition of 998 < Re < 5996,when the Angle of attack was 45°,it was more conducive to the enhanced heat transfer of fins in the liquid cooling pipeline.In the range of 2996 < Re < 4055,the growth rate of Nu decreased,which might be related to the change of flow state.Triangular wing aperture can effectively reduce the resistance factor in the pipeline.This paper optimizes and improves the liquid cooling system of the strengthened pipeline studied,especially one of the most critical and important parts in the liquid cooling system of the battery module,which can provide important support for the subsequent structural design of the battery thermal management system,and has important theoretical research significance and application value.