Performance analysis of a wet pad assisted air-cooled battery thermal management system with varying number of battery cells

Battery thermal management system is essential in electric vehicles to ensure thermal safety and efficient battery operation. Air-cooled battery thermal management technology is well-developed and inexpensive, but the small convection coefficient of air limits the heat dissipation capability of the system. Direct evaporative cooling, in the form of a wet pad, can be integrated to enlarge the cooling capacity through water evaporation. There is little research investigating the effectiveness of the system under varying number of battery cells. Besides, the minimum temperature of the battery pack is rarely discussed under various ambient conditions. Different from previous work, this paper aims to indicate the optimal working condition zones of a wet pad assisted air-cooled battery thermal management system. Thermal model of the wet pad and battery pack are established using MATLAB and Fluent software, respectively. Simulation results show that with the assistance of the wet pad, 4.9–6.2 °C cooler air would be produced, resulting in a 3.6–6.1 °C reduction in the maximum surface temperature of the battery but a slightly larger temperature difference among batteries. Better cooling performance of the wet pad can be obtained at arid ambient conditions. Using the wet pad, the optimal working condition zones of the battery pack are expanded because it is more capable of hot weather. Battery temperature control failed in the dry-air cooling cases at 2C discharge rate with 18 batteries and above, but with the wet pad, it can be controlled at 33.6 °C even with 60 batteries. Lastly, from an optimization viewpoint, by wrapping each battery with 0.5 mm aluminum flake, the maximum surface temperature and the temperature difference of the battery pack can be reduced by 4.1 % and 17.4 %, respectively. The findings will be beneficial for the design and optimization of a wet pad assisted air-cooled battery thermal management system.