| The increasingly serious environmental pollution and the gradually exhausted fossil energy make the development of efficient,energy-saving and zero-emission electric vehicles more and more attention to the world.Lithium-ion battery has the advantages of large capacity,light weight,long service life and so on.It is the main energy source of electric vehicles and hybrid electric vehicles,but it has a high sensitivity to working temperature.Large size power battery pack not only has high power,but also has the advantages of easy integration,but there are great thermal management challenges in maintaining the optimal temperature and temperature uniformity of the entire battery pack.Therefore,the reasonable design of power Battery Thermal Management System(BTMS)is the key to ensure the good performance of the power battery and prolong its service life.For this reason,theoretical analysis,numerical simulation and experimental verification are adopted in this paper to analyze the heat dissipation performance and optimize the structure of the BTMS coupled with micro-channel and composite phase change material(PCM)which is suitable for the high temperature area.The main research work and innovation points of this paper are as follows:(1)The heat generation rate model of the single battery was established and verified,and the temperature distribution characteristics of the single battery at different discharge rates were investigated under the condition of natural convection heat transfer in the high temperature area,which provided a reference for the design of the BTMS in the high temperature area.(2)A mathematical model and numerical method for the study of heat dissipation performance of BTMS coupled with microchannels and composite PCM for high temperature areas were developed,and grid independence verification was carried out.The cooling performance of the battery pack with different cooling ways was compared and analyzed.The advantages of coupled cooling strategy and the necessity of coupled BTMS are illustrated.The influence of microchannel coolant flow rate on coupled BTMS cooling performance was investigated and the appropriate coolant flow rate was obtained.In addition,the cooling performance of paraffin wax and composite PCM was compared,and the influence mechanism of the mass fraction of expanded graphite in composite PCM on the cooling performance of coupled BTMS was further revealed.(3)The cooling performance of coupling BTMS was systematically studied under different structure parameters.The influences of different coolant flow direction,micro-channel layout direction,number of micro-channels and section shape of micro-channels on the heat dissipation performance of the battery pack were analyzed,and the optimal micro-channel structure was obtained.Based on this,the structure of PCM and aluminum frame was further improved.Finally,the heat dissipation performance of the optimized coupled BTMS in continuous charge-discharge cycles was studied. |
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