Numerical Prediction And Measurement Of Pressure Drop And Heat Transfer In A Water-Cooled Hollow-Shaft Rotor For A Traction Motor Application

This article addresses the rotating effect on the pressure loss and heat transfer coefficient (HTC) of a hollow-shaft rotor cooling system for an automotive traction motor. Firstly, a numerical model based on computational fluid dynamics (CFD) was established to fully understand the mechanism of rotational flow patterns. Experiments were then performed to measure and compare heat exchange and pressure loss between rotating and stationary conditions with the assistance of an analytical thermal model. Finally, trends of pressure drop and HTC at various rotational rates were explained in detail. Based on CFD simulations and experimental prototype testing, two opposite effects: boosting or diminishing on pressure drop and heat transfer due to rotation have been identified. Moreover, the rotation can significantly improve the overall HTC and pressure loss of an axial turbulent flow. As a result, a significant drop in terms of rotor temperature is identified for an automotive traction motor when such a rotor cooling system is implemented.