Immersion evaporative cooling for high-power density motors in future aircraft

Electric aircraft offer higher energy conversion efficiency and lower carbon emissions compared to traditional fuel aircraft. Increasing motor power density can further improve system efficiency, making thermal management the main limiting factor for power density enhancement. Immersion evaporative cooling has emerged as a promising solution due to its excellent thermal characteristics. This paper establishes a hybrid analysis method coupling thermal network and computational fluid dynamics (CFD) approaches to study the convective heat transfer coefficient (CHTC) of immersion evaporative cooling used in motors under different coolant and current densities, calculating motor temperatures and operating time. Numerical results show that under immersion evaporative cooling conditions, the average CHTC reaches 773 W/(m²·K) for Novec 7300 and 5328 W/(m²·K) for deionized water, providing key parameters for the thermal network model. Experimental results demonstrate that the proposed cooling method maintains winding temperatures at approximately 100 °C during a 4-hour long-term stable operation, validating the accuracy of the numerical model. The research indicates that immersion evaporative cooling can effectively control motor temperature rise, offering important reference for cooling system design in next-generation high-power-density motors.