Study On Power Battery Cooling System With Heat-pipes

The development of electric vehicle mainly depends on power battery technology, which is one of the most crucial technologies. The current electric vehicle requires higher energy density, higher power density, longer life cycle and safety in use. Traditional lead-acid battery can not meet new requirements raised by people any more, however, Lithium-ion power battery, featuring higher specific energy, longer life cycle and more friendly to environment, can resolve problems like short mileage, poor power and short life cycle of batteries of electric vehicle. Li-ion power battery also contains large amounts of nonferrous metal, which has very high value for recycling, now Li-ion power battery has wide use on most electric vehicles. While the electric vehicles run under large load, the power batteries will be in the state of discharging continuously. If the battery thermal management system can not transfer the heat generated by batteries quickly and effectively, it can lead to thermal runaway, oxidation and combustion of electrolyte and even explosion. Besides, Li-ion battery only can work within the temperature range from-20 to 60 degrees centigrade, and has the optimum working temperature range from 20 to 50 degrees centigrade. To ensure the battery to be within the optimum working temperature range, power battery thermal management system is imperative.The paper concluded the current development status of electric vehicles, and designed one Li-ion power battery cooling system with heat-pipes. The system works mainly on heat-pipes cooling and assists with air cooling.The paper mainly contains:First, it finished the design of radiating fins. It conducted the structure design of radiating fins with determined the actual structure size and gross heat amount of the battery pack. It built the three-dimensional solid model, carried out structured mesh partition, and conducted independent study on grids, with chosen the calculating zone of the radiating fins. It got the rule between fin cooling capability and fin spacing, then it determined the number of fins.Second, it conducted steady numerical simulation. It separately analyzed the effect of working current and environment temperature to internal resistant, and the temperature rise characteristic under constant current discharging. On the basis of them, it got the heat generating law of power battery, built three-dimensional solid model, and conducted mesh partition. Then it got the temperature field distribution of cells and battery pack.Third, it conducted transient numerical simulation of the battery pack. It set working current of battery with different discharging rules under different time periods, and got the corresponding heat generating law. Then it got the change rules of battery temperature, by setting boundary conditions with user-defined functions in FLUENT.The battery pack thermal management system with heat-pipes designed by this paper, well solved the difficult problems of too high temperature in battery pack and too large temperature difference among batteries. It provides new research direction of power battery thermal management system.