| The development of electric vehicles has been promoted by the increasing reduction of oil and coal and the aggravation of environmental pollution.Lithium-ion batteries,with its many advantages such as high voltage,large energy density,long cycle life and so on,have become the preferred power batteries for electric cars.Because lithium-ion batteries could generate a lot of heat,effective thermal management of lithium-ion batteries has become a bottleneck problem in the application of battery,so we use cooling-plate to dispatch the heat of lithium-ion batteries.We analyzed the cooling performance of the cooling-plate by ANSYS FLUENT and temperature distribution of the battery cell and pack.The main works of this paper are as follows:We discussed the structure of the lithium-ion batteries,chemical reaction principle and heat production mechanism,which providing a theoretical basis for subsequent mathematical modeling and simulation.The heating effect model is set up on the basis of heat transfer and heat transfer mechanism of the battery.The thermophysical parameters have been calculated and the heat production rate model has been set up by the heat generating theory which was put forward by Bernardi.A heat-dissipation structure design is carried out,a U-shaped cold plate model is proposed,and a heat dissipation model of a battery and a cold plate was established.The heat dissipation effect of the cold plate and the temperature of the battery were numerically calculated.We analyze the effect of the number and length of cold plates,the flow direction of the cooling liquid,the inlet mass flow and the discharge rate on the temperature distribution of the battery.The results show that the cooling effect of No.4-1cold plate is better,and the temperature rise of the battery is the smallest when the cold plate length is 57mm.By analyzing the eight kinds of flow directions,it is concluded that in the fourth mode,the temperature of the battery is the lowest,and the latter three flow modes can effectively reduce the temperature difference of the battery.The battery can reach the temperature requirement when the mass flow rate is 0.2×10-5kg/s under the discharge rate of 1C,the mass flow cannot be less than 10-5kg/s when the 3C discharge,and the mass flow should be higher than 1.4×10-5kg/s when the 5C discharge.Based on the U-shaped cold plate,a double U-shaped channel structure was proposed.To facilitate the calculation,the heat source of the cold plate bottom surface was loaded,and the effects of the arrangement of the double U,the structural parameters of the channel,and the variable cross-section flow channel on the thermal performance were analyzed.The results showed that rotating the middle small counterclockwise 180 can reduce the temperature of the heating surface by 2.02? and reduce the temperature difference by1.11?;when the parameters of the flow channel satisfy l1=16mm,l9=4mm,l12=2mm,and l14=21mm,When l3=7mm and l7=8mm,the heat transfer and temperature equalization performance of the cold plate are the best;increasing the cross-sectional width of the inlet section can improve the heat transfer performance,and the cross-sectional width satisfying the first transverse segment is greater than the third transverse segment.When the section width of the inlet section is greater than the section width of the outlet section,the heat exchange conditions exhibit the best results.Finally,a heat dissipation model for the battery and dual U-shaped channels was established.It was found that the heat transfer effect of the double U-shaped channels was better than that of the U-shaped channels.Finally,a temperature field analysis is performed on a battery pack consisting of 5 single cells.The cooling model uses a No.4-1 U-shaped cold plate.The cooling medium?nanofluid and water?,the inlet velocity,and the cold plate layout method are used to analyze the heat transfer.The influence of the situation shows that the heat dissipation effect of the nanofluid is better;using the arrangement of the fork row,compared with the row,the temperature rise is smaller and the temperature uniformity is better. |
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