Pre-cooling of air by water spray evaporation to improve thermal performance of lithium battery pack

•The spray cooling is effective to reduce maximum temperature.•Maximum temperature difference of batteries gets large due to spray cooling.•The optimum water flow rate is related to the air velocity.•Air velocity dominates the residence time and diffusion behavior of droplets.•High ambient temperature results in increased maximum temperature of batteries. The performance of battery pack is sensitive to the working temperature and often hindered by overheating, so the high efficiency cooling technology is of significant benefit to the battery performance. In this work, the air pre-cooling by water spray evaporation is applied to the battery pack thermal management. The influences of water flow rate, water droplet size, air velocity and ambient temperature on the battery performance are investigated by computational fluid dynamics. The results show that the water spray cooling can greatly reduce the maximum temperature but increase the temperature difference compared to the dry cooling. A high water flow rate leads to the reduced maximum temperature, but plays the adverse role in the maximum temperature difference. The water droplet optimal size depends on the air velocity due to its dominant roles in the residence time and diffusion behavior of droplets. When the ambient temperature is below 308.15 K and the air velocity exceeds 2 m/s, the water flow rate of 0.0002 kg/s can meet the cooling demands of battery pack.