| The power battery will produce a certain amount of heat in the work and has a high sensitivity to temperature,so it is essential to ensure that it works in a suitable temperature range.To solve the problem of battery heat,on the one hand,it is necessary to study the heat generation mechanism and reduce the heat generation from the battery itself.On the other hand,it is necessary to design a scientific and effective battery heat management system.In this paper,the heat generation characteristics of a square ternary lithium ion battery are studied and the corresponding liquid cooling and heat management system is designed.The main research contents of this paper are as follows:(1)Li-ion batteries with different shapes and chemical systems were compared,and square ternary lithium battery was selected.The battery module was composed of 1 parallel 8 series(1P8S),and the corresponding liquid cooling and heat management system was established.Among them,the liquid cooling plate and its pipeline system has four kinds,namely 4P,3P1S,2P2S and 1P.The flow process is analyzed and the indexes for evaluating the consistency of flow distribution,heat dissipation,average temperature and energy consumption of liquid cooling structure are proposed.(2)Based on the single-factor control variable method,the influences of coolant flow rate,collector section size,harmonica-shaped tube length,cavity thickness and inlet and outlet aperture on the flow distribution consistency and system flow resistance of 4P,3P1S and 2P2S liquid cooling structures were studied.Based on the orthogonal experimental analytic hierarchy process,the influence weight of each factor on the consistency of flow distribution was studied.The cross-section size of the collector tube and the thickness of the harmonica-shaped tube cavity were the main influencing factors,and the length of the harmonica-shaped tube and the aperture of the inlet and outlet were the secondary influencing factors.The parameters of the liquid cooling structure were optimized.The optimal parameters of the three liquid cooling structures are as follows:the cross section size of the collector tube is 16*16mm~2,the thickness of the harmonica-shaped tube oral cavity is 2mm,the length of the harmonica-shaped tube is 500mm,and the aperture of the inlet and outlet is 14mm.(3)After increasing the coolant temperature,the average temperature of 4P,3P1S,2P2S and 1P liquid cooling structures increases linearly,and the maximum temperature difference of 2P2S and 1P liquid cooling structures decreases.After the shunt design,the temperature uniformity of the liquid cooling structure is improved,but there is still a large temperature gradient along the Y direction.The stepped thermal pads were designed to reduce the maximum temperature difference on the upper surface of the thermal pads of the four liquid-cooled structures by nearly 30%and increase the average temperature by 2-3%.Four kinds of liquid cooling structure schemes are designed with different flow rates to improve their heat dissipation,temperature uniformity and energy consumption performance.Under 1C discharge,the maximum temperature of the battery modules of the four liquid cooling schemes was less than 36.5℃,and the flow resistance is less than 20 kPa.The maximum temperature difference of 4P,3P1S and 2P2S is within 0.7℃,and the 1P liquid cooling structure is 1.1℃.(4)The flow resistance of the system is tested,and the deviation between the measured value and the simulated value is less than 5%.The temperature characteristics of the battery module of the four liquid-cooled structures were transiently analyzed under the conditions of WLTC and high temperature fast charging.Under the condition of high temperature fast charging,the maximum temperature of the battery module of the four liquid cooling structures is close to 45℃,which needs to be further reduced. |
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