Modeling and Optimization of Self-pumping Air-cooled Thermal Management System for a High Specific Power Outer Runner Electric Motor

This study models and optimizes the cooling fan and heat exchanger of an outer-rotor self-pumping air-cooled electric machine using analytical relationships, computational fluid dynamics (CFD), and experimental data. The fan model predicts pressure head rise and brake power based on geometry, operating conditions, and air properties, whereas the heat exchanger model estimates pressure drop and heat transfer coefficient as functions of volumetric flow rate. These models facilitate the integrated optimization of the thermal management system, validated through experiments. Two optimized designs were fabricated and tested with a customized apparatus. Both the fan and heat exchanger are additively manufactured, with the fan driven by an external motor for precise speed control. The heat exchanger’s temperature is monitored while heat is injected at the armature winding location. This study provides a comprehensive tool for designing effective fan-heat exchanger pairs for electric motors.