Numerical simulation of transient heat transfer capability of stator ring surface spray cooling in electric motors

To address the overheating issue caused by the continuous increase in power density of electric vehicle motors, which traditional cooling technologies struggle to handle, this study develops a transient heat transfer numerical model on the annular surface of the motor stator. The effects of nozzle number, spray flow rate (Q), and nozzle height on the heat transfer capability of the stator surface are investigated. The simulation results show that increasing the number of nozzles enhances the liquid film coverage and improves temperature uniformity. Additionally, increasing the Q enhances the droplet impact kinetic energy, reduces the liquid film thickness, and thus lowers the maximum surface temperature and temperature difference. Furthermore, increasing the nozzle height helps achieve more uniform droplet distribution, suppresses splashing, and further improves cooling capability. Under a vibration frequency of 4000 Hz, increasing the nozzle number from 12 to 18, the Q from 4000 mL/min to 8000 mL/min, and the nozzle height from 20 mm to 30 mm results in a decrease in the maximum temperature by 25.3 °C, 38.8 °C, and 13.1 °C, respectively.