Research on the Effect of Heat Pipe Inclination Angle on Temperature Distribution in Electrical Machines

Due to high equivalent thermal conductivity with lightweight and small size, heat pipes (HPs) are being extensively applied in the motor cooling system to improve its thermal performance. However, when practically installed in electrical machines, the inclination angle of the HP will affect its thermal conductivity and motor temperature distribution as well, which is still unclear. This article intends to figure out the effects of HP inclination angle on motor temperature distribution via both theoretical and experimental investigation. Based on the theoretical analysis of the HP inclination effect, the equivalent thermal conductivity of the HP with different inclination angles from 0° to 180° is experimentally investigated on a dedicated platform. Then, temperature distribution across a full-size stator-winding assembly with HPs is quantitatively studied using an established thermal model. Finally, the thermal simulation results are experimentally verified by testing on a processed specimen. The results indicate that the HP thermal performance degrades by over 80% with the inclination angle from 0° to 180°, which results in a significant temperature nonuniformity across the motor under liquid cooling conditions.