Study Of Battery Thermal Management Based On Direct Refrigerant-cooling

The continuous deterioration of global environment and the annual consumption of nonrenewable fossil fuels have made energy conservation and environmental protection more and more important to the people all over the world.Electric vehicles are driven by electric energy,have no exhaust emissions and no noise,and are considered to be the future trend that replace traditional fossil fuel-driven vehicles.As the most important component of the electric vehicle,power battery needs to be improved in terms of temperature performance.A properly designed thermal management system plays a key role in improving the safety and cruising range of the vehicle.In this paper,from the prospective of shortening the charging time of buses,the design and research of the power battery thermal management system is carried out.Comparing the current heat management cooling methods,the direct cooling method using refrigerant is used to control the temperature of the lithium-ion battery.The cold plate is used as cooling device with the refrigerant flows in the pipe of it.By analyzing the structure and thermal performance of lithium-ion battery cells and comparing various types of lithium-ion batteries,a good-performance prismatic lithium iron phosphate battery was selected,and the heat generation of the battery was calculated using the Bernadi heat generation rate model.Calculate and design the battery arrangement of the whole vehicle according to the parameters of the electric bus and battery.Compared with the commonly used vehicle refrigerants,R1234 yf is selected with environmental advantages such as small GWP.Use FLUENT software to perform numerical simulation on bus battery,refrigerant and cold plate.The single battery is simulated under the charging rate of 1C,3C,and 5C.According to the simulation results of the single battery,it is found that the battery thermal performance is good when charging at 1C.It is determined that the following numerical simulations of the battery,refrigerant and cold plate are for 3C,5C The situation is further studied and analyzed.Optimized the design of the cold plate,compared three cold plate pipes with different crosssection sizes and four cold plates with different tube lengths.According to the three evaluation indicators of the battery’s maximum temperature,maximum temperature difference and pressure drop,the system with a larger CPI was selected.With a pipe area of30mm×4mm,it is found that the number of pipeline processes is positively correlated with the maximum temperature and temperature difference,and negatively correlated with the pressure drop.Considering various factors,a four-process cold plate that meets the pressure drop requirements and has better temperature control performance is selected.The heat dissipation model of the optimized structure of the battery pack is used to study the influence of different working conditions on the battery temperature,and simulate the influence of the initial battery temperature,refrigerant evaporation temperature,and refrigerant flow rate on the temperature at 3C and 5C charging rates.Therefore,the simulation results of the four-process pipeline cold plate show that the initial temperature of the battery has little effect on the temperature at the end of the reaction.The refrigerant evaporation temperature is positively correlated with the battery maximum temperature and has a linear relationship,and is negatively correlated with the temperature difference;Both the maximum temperature and the temperature difference are positively correlated.Finally,according to the temperature change,the flow rate at 3C and 5C is0.15kg/s and 0.22kg/s.