High-Viscosity Spray Cooling System for High-Reliability Motor Drives in Electric Vehicles: A Review

This paper explores a novel approach of employing a singular liquid for both lubrication and cooling in compact-class and high-reliability design of future electric vehicle (EV) drivetrains. While the oil spray method offers direct cooling for hairpin windings of EV motors, its implementation poses several challenges, most notably, the high viscosity leads to inefficient spray pattern. This study makes an effort to review the most recent advances in this topic, emphasizing the pivotal spray hydrodynamic parameters that influence the cooling performance. Additionally, the paper investigates heat transfer correlations and predictive models proposed by previous research studies, considering the thermophysical properties of oils. Finally, this study aims to highlight challenges and practical concerns associated with the application of oil spray technique for thermal management of EV motor drives.