Experimental study on 18650 lithium-ion battery-pack cooling system composed of heat pipe and reciprocating air flow with water mist

Lithium-ion batteries (LIBs) are critical power sources for portable devices, electric vehicles, power grids, and energy-storage systems. Effective thermal management is mandatory for achieving optimal battery performance. Although the air-cooling method has been investigated extensively owing to its simple structure, convenient maintenance, and low cost, it is insufficient for cooling large-scale battery packs because of its limited air-cooling capacity and unsatisfactory temperature uniformity. Thus, a reciprocating spray cooling system comprising a reciprocating air flow channel, heat pipe array, and spray nozzle is proposed herein for the efficient cooling of 18,650 LIB packs. The effects of the inlet air speed, spray frequency, and spray duty cycle on the cooling performance of the reciprocating mist cooling system and the corresponding optimal operating parameter range are analyzed. Additionally, the competitive mechanism between forced air convection and evaporative cooling is discussed. The results indicate that, compared with the case of natural convection cooling, the temperature increment of the battery pack decreases by 32.1 % under reciprocating mist cooling. Meanwhile, the maximum temperature difference reduces to approximately 3.41 degrees C with 3C of discharge. The spray frequency minimally affects the overall heat dissipation but induces surface temperature fluctuations in individual batteries. Increasing the spray duration per 10 s in a single spray duty cycle can reduce the average temperature of the battery pack by approximately 2 degrees C. Additionally, the power-allocation scheme affects the heat dissipation of the system. Decreasing the flow rate of spray cooling water and increasing the inlet air speed promote the evaporation of water mist inside the system, thus further improving heat dissipation. This study provides new insights into the design of air-cooled thermal management systems for battery packs.