Optimization Research On Heat Pipe And Heat Transfer Components Based On Battery Heat Generation Characteristics

As the core component of new energy vehicle,power battery has been paid much attention to its thermal management and thermal safety performance.To further improve the efficiency and safety of the battery thermal management system and reduce the energy consumption of the thermal management system is an extremely important link in the further development of new energy vehicles.The excellent performance of heat pipe,such as passive heat transfer,heat sink separation,cold and heat bidirectional,and heat switch,makes it a strong candidate for future battery thermal management.However,there are still some problems in structure integration and deep coupling between heat pipe and battery.Therefore,aiming at the heat dissipation technology of battery coupled heat pipe,the research work explores and optimizes the heat dissipation structure of battery coupled heat pipe through equivalent thermal circuit analysis.Firstly,the feasibility of equivalent thermal circuit analysis is discussed in this paper,and the heat generation characteristics and its anisotropic heat transfer characteristics of power cell are theoretically derived.The network model of heat transfer resistance of heat pipe was established,the calculation method of thermal resistance of each part was expounded,and the equivalent thermal resistance of evaporation condensation and steam flow process in heat pipe was analyzed in detail.The convective heat transfer form and equivalent heat circuit modeling of coolant part are described.Secondly,the equivalent thermal circuit model of battery coupled heat pipe heat dissipation was established by Simulink,and the experimental platform of battery coupled heat pipe heat dissipation was built.The equivalent thermal circuit model was verified by the experimental method,and the error between the two was less than 7%.On this basis,a battery coupled heat pipe cooling structure with small integration space and low flow resistance was proposed.The equivalent thermal circuit analysis method was used to evaluate the temperature and temperature uniformity of the battery under different coolant flow,coolant temperature,ambient temperature and discharge rate,based on the maximum temperature of the battery and the horizontal and vertical temperature difference of the battery.Explain the phenomena that arise.Thirdly,in view of the problems in the analysis of basic heat transfer characteristics,heat transfer enhancement and temperature uniformity optimization were carried out for the single module of battery coupled heat pipe heat dissipation through simulation calculation.Heat transfer enhancement was carried out in the vertical direction by adding graphite sheet.Under basic conditions,the maximum temperature rise was reduced by 14.7%,the horizontal temperature difference was reduced by 48%,and the vertical temperature difference was reduced by 36%.The effect is optimal when the thickness of graphite sheet is 0.5mm.By adding insulation material to reduce the influence of environment on the temperature of the battery,the horizontal temperature difference is further reduced by 29% based on the graphite sheet scheme.Then,the influence of different length,width,thickness of heat pipe and cooling channel radius on the temperature and temperature uniformity of the battery is discussed respectively.The optimal length of heat pipe evaporation section is between60% and 80% of the total battery length.With the increase of the section radius of the cooling passage,the maximum temperature and horizontal temperature difference will decrease,while the vertical temperature difference will increase,which mainly affects the convective thermal resistance and the inlet and outlet temperature difference.For flat heat pipes,the increase of thickness and width of heat pipes can reduce the thermal resistance of steam flow and improve the heat transfer effect,but the improvement trend is decreasing.Through orthogonal experiment,the thermal performance of the battery module is the best when the length of the heat pipe is 60%,the width is 18 mm,the thickness is 4mm and the section radius of the flow channel is 14 mm.Finally,on the basis of the optimization of single-module structure,the horizontal temperature difference caused by unidirectional liquid flow of the battery pack was reduced to the minimum through the arrangement of variable parameter heat pipes.Under the basic working condition,the horizontal temperature difference of the battery pack was reduced by 38%.The thickness parameter range of the heat pipe was migrated under the thickness gradient of 0.5mm,and the horizontal temperature difference of the battery pack was further reduced by 66% after the migration.Reduce the horizontal temperature difference of the whole battery pack to the same as that of the single module.By flattening the width of the heat pipe,it can reduce by 27.8% under the thickness gradient of 3mm,and the horizontal temperature difference can be further reduced by 29% after the parameter range is shifted to small.It can also improve the horizontal temperature uniformity of the whole battery pack.