Study On Heat Pipe-Based Heat Dissipation Scheme Of Cylindrical Li-Ion Battery Pack For Pure Electric Vehicle

To reduce dependence on fossil fuels and reduce vehicle emissions.Electric cars are gaining popularity.As the core of electric vehicle,the temperature of power battery has great influence on its energy performance and cycle life.The operating temperature should not exceed 50?,the maximum temperature should be between 20? and 50?,and the temperature difference of the battery should be controlled within 5?.In order to achieve this goal,this paper designs a heat dissipation system with the coupling of heat pipe and air cooling or liquid cooling for the 18650 battery pack,studies the effectiveness of the heat dissipation system and makes targeted optimization.The main research contents and conclusions of this paper are as follows:1.Numerical simulation of temperature rise change of single lithium battery under discharge rates of 1C,2C,3C and 5C according to battery parameters.And the discharge temperature rise experiment is carried out.The correctness of the numerical calculation parameters is verified by comparing the experimental results with the simulation results.2.Design the heat dissipation system of heat pipe coupled with air cooling or liquid cooling,and conduct experimental research.It is found that the coupled heat dissipation structure can effectively suppress the temperature rise of the battery and improve the temperature uniformity of the battery pack.But the increasing of inlet speed did not significantly reduce the average temperature and temperature difference between the battery pack.The heat dissipation effect of heat pipe and air cooling coupling structure can be improved by increasing the number of heat dissipation fin.From the overall performance,the performance of heat pipe and liquid cooling coupling structure is more effective than that of air cooling.3.By optimizing the arrangement of heat conducting fins and liquid cooling channels of the coupled heat dissipation structure,the temperature control effect of the battery pack of the system can be further improved.Considering the heat transfer effect and efficiency and the optimum heat conduction fin structure is structure four.The optimal layout of liquid-cooled runner is layout 2.The optimal length of the condensation is 30 mm.4.The performance of water,34% ethylene glycol solution,50% ethylene glycol solution and 60% ethylene glycol solution in three aspects of freezing point,heat dissipation effect and pressure drop at the inlet and outlet was comprehensively considered.The relationship about the cooling fluid flow rate and temperature for the temperature control effect of the battery pack is compared.It is found that the cooling fluid flow rate has little effect on the temperature control performance of the battery.The decrease of the coolant temperature will decrease the maximum temperature and the average temperature of the battery pack.The relationship between the two is basically linear.But the decrease of the coolant temperature will increase the temperature difference of the battery pack.5.In order to control the temperature and temperature difference within a reasonable range when the battery is discharged at a large power ratio,a liquid cooling control strategy of temperature gradient and intermittent flow is designed.This strategy can control the average temperature and temperature difference of the battery pack with the discharge of 5C within a reasonable range until the discharge ends.Strategy 5 has the best temperature control effect.