| In this paper,under the support of the National Natural Science Foundation of China(No.51675258,51261024,51075372),Science and Technology Plan Project of Jiangxi Province(No.20141BBE50021),and Original Energy Technology(Tianjin)Co.,Ltd.In view of the current electric vehicle field,the battery pack has excessive heat accumulation during operation,the internal temperature of the cabinet is too high,and the adaptability to the environment is poor.As a result,when the power battery pack is operated under thermal abuse conditions,A series of questions,such as the battery performance is degraded and the cycle life is shortened.Firstly,the main arrangement of the battery module and the characteristics of the heat dissipation structure of the battery box are analyzed.Taking into account the requirements of the protection level of the box,the layout design of the inlet and outlet of the box is proposed at different positions of the box.Secondly,Combining with Computational Fluid Dynamics(CFD)simulation method and experiment,using the model 18650 cylindrical battery2-dimensional model,the variation patterns of temperature field and velocity field inside the box at different wind speeds were studied.Finally,using the relevant experiments and CFD simulations,the effectiveness and possible limitations of the air-cooled heat dissipation of the 3-dimensional model of the cylindrical battery under different arrangement are studied,which provides theoretical guidance and reliability basis for the follow-up battery thermal management system design.It can even save the development cost of thermal management systems.The object of this article is the current mainstream automotive lithium-ion battery,mainly from the following aspects to do research:1.The background and significance of this research direction are discussed.The development of pure electric vehicle power battery,the research status of power battery thermal management system at home and abroad are reviewed,and the advantages and disadvantages of the current thermal management system are analyzed.Based on this,it is proposed.The research content and innovations of this paper.2.Taking into account the structural characteristics of lithium-ion batteries,the heat-generating mechanism of the batteries with different structures was analyzed and the thermal properties of the batteries were calculated.At the same time,the momentum,mass,and energy conservation laws were used in Cartesian and cylindrical coordinates.Different heat conduction differential equations were established under different structures to lay the foundation for subsequent battery temperature field research.3.The lithium-ion battery cells were tested for their charge and discharge capacity at different temperatures and temperature rise experiments at different discharge rates.The effect of ambient temperature on the charge and discharge performance of the battery and the effect size of different discharge rates on the internal temperature rise of the battery were obtained.A single thermal effect model was established to simulate and calculate temperature rise changes at different discharge rates(0.5C/1C/1.5C/2C).Paste thermocouples on different parts of the cell were used to obtain experimental data and simulation results.The comparative analysis shows that the relative error of the two is within 3%,which verifies the feasibility of the 3-dimensional battery thermal effect model.It also proves the necessity of battery thermal management and provides theoretical basis and method guidance for the follow-up battery thermal management design.4.In the parallel arrangement of the battery pack,fork-shaped arrangement and trapezoidal arrangement,through the pack at different locations to open the inlet and outlet.The air inlet is for the battery cell and the battery gap;the air outlet is for the battery cell and the battery gap,and a 2D thermal effect model of the 18650 model cylindrical battery is established.Through horizontal and vertical comparisons,the battery group is obtained: under the same arrangement,the optimal opening scheme for the inlet and outlet of the box is set;under the different arrangement methods,the optimal arrangement scheme is adopted.5.Due to the 2-dimensional arrangement,the air inlet and outlet are set on the same plane,and only the effect of the inlet and outlet openings on the distribution of the temperature field and velocity field in the battery box can be seen.This does not truly reflect the cooling effect of the air cooling of the battery box.Because of the thermal expansion and contraction effect,the heated gas expands and the density decreases,resulting in hot air rising and cold air falling.Therefore,it is necessary to establish a three-dimensional model of the battery pack to study the effectiveness of the air cooling on the heat dissipation of the battery pack.Therefore,a three-dimensional model of a cylindrical battery with two different arrangements was established.Using CFD software,the temperature field distribution of the battery at constant rate discharge and different wind speeds(0.3m/s,0.7m/s,1.5m/s)was simulated.,and made a comparativeanalysis of its temperature rise data: set up an air-cooled heat dissipation experimental platform,and studied the effectiveness of air-cooled heat dissipation under different wind speeds,and conducted comparative analysis of its data.6.Finally,the content of the research in this paper is summarized,and the follow-up research is further explained. |
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