Development of an Experimental Methodology to Characterize Liquid Cooling Systems for Electric Motors

Efficient thermal management of electric motors is essential for competitive electric mobility. The end-windings are a critical part of the motor, in terms of thermal management. Their cooling can be improved by injecting transmission oil. In the design of such cooling systems, the convective coefficient is an important parameter for quantifying heat transfer towards the liquid. In this study, oil injection on a flat heated plate is used as a model experiment to replicate such cooling and characterize convective heat transfer. Embedded thermocouples measure the temperature at different depths in the plate. The convection coefficient is estimated via different experimental and numerical methods. The methods developed consent to evaluate the coefficient within 20 times the nozzle distance. Values up to 7550W/m2K are obtained nearby the impingement point.