| With the rapid development of new energy technologies,the application demand of energy storage systems is also gradually growing.Lithium battery energy storage has the advantages of environmental friendliness,high specific energy and good cycle characteristics,and occupies a dominant position in electrochemical energy storage.With the expansion of battery capacity and system power density,energy storage systems will generate a lot of heat when charging and discharging.The thermal safety and group thermal life of lithium batteries restrict the development of energy storage systems.Therefore,it is very important to design an energy storage battery thermal management system with excellent cooling performance.The traditional single air cooling system can no longer meet the increasing heat dissipation demand.The composite thermal management system can achieve complementary advantages and improve cooling performance.Phase change cooling has the advantages of simple system,less energy consumption,constant temperature and heat absorption,etc.,and has a good temperature control effect on the battery pack,and is considered to have broad application prospects.Therefore,this article conducts research and design on the thermal management system of lithium battery energy storage battery pack based on the combination of air cooling and phase change materials.Firstly,this article introduces the internal structure and working principle of lithium battery,and chooses 26650 lithium iron phosphate battery as the research object.The heat generation principle and heat transfer path of lithium battery were analyzed,the theoretical heat model of lithium battery was established,and the temperature rise characteristics of single lithium battery under different discharge rates were simulated,and compared with the experimental data,the effectiveness of the heat model was verified.Secondly,in order to solve the heat dissipation problem of lithium batteries under high-rate discharge conditions,a single battery model based on pure paraffin phase change cooling was designed.The results show that at room temperature,pure paraffin can effectively control the temperature rise of the battery,but under high temperature and high rate conditions,the low thermal conductivity of pure paraffin makes it difficult to dissipate heat in time,and the battery temperature exceeds the safe range.In order to solve this problem,two heat transfer enhancement measures were proposed,which were made of composite phase change material with high thermal conductivity by adding expanded graphite to paraffin wax and coupled metal fin,and the influence of different parameters on heat dissipation effect was studied.The research results show that both the composite phase change material and metal fins can significantly improve the heat dissipation effect.Among them,when the composite phase change material is used for heat dissipation,compared with pure paraffin heat dissipation,the maximum temperature of the battery surface is reduced by 21.37%.The vertical fins have a more significant effect of enhancing heat transfer.Compared with pure paraffin heat dissipation,the addition of annular long fins reduces the maximum surface temperature of the battery by 10.98% and 11.19% under natural convection and forced convection environments,respectively.However,under the condition of high temperature and large magnification,when the two heat transfer enhancement measures are coupled with air cooling,the coupling effect is poor,and the air cooling cannot be fully utilized to improve the cooling performance.Finally,in view of the poor coupling effect of the traditional air-cooling-phasechange cooling system,two air-cooling-phase-change composite energy storage lithium battery pack heat dissipation structures are proposed,which are the reserved air flow channel in the inner shell and the extended annular metal fins in the inner shell,and then conducted a comparative study.The research results show that the reserved air channel model of the inner shell can fully combine the advantages of air cooling and phase change cooling,so that the air cooling and phase change cooling can be better coupled,and the liquid phase rate can be reduced by up to 45.8%.Increasing the number of air inlets and outlets can improve the uniformity of battery surface temperature. |
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