Heat Transfer Performance Enhancement On Wheel Hub Motor With Fin Adjoint Optimization

An effective thermal management system for motors can improve the efficiency, stability, and lifespan, so it is important to study and evaluate different modes of cooling. Hub-motors generally rely upon aerodynamic cooling because the geometry of the wheel naturally limits packaging space, and can preclude the introduction of more complex, efficient (and expensive) cooling systems. When the heat load is high the aerodynamic cooling alone may not be sufficiently enough to cool down the motor to the safe temperature range, in such situations surface modification or topology enhancement with fins become relevant. In this study, three-dimensional (3D) approaches for cooling a commercially available 500W scooter wheel hub motor (BLDC-Brushless Direct Current) are simulated under various driving conditions using the StarCCM+, a computational fluid dynamics (CFD) package. The results show that aerodynamic cooling alone without any surface modification is not sufficient for lowering the temperature of the stator to safe range (<135˚C), when the heat load is more than 5% of rated power. To improve the heat transfer surface features, the internal and external convective thermal resistance has been determined numerically with simulations to introduce cooling fins. The internal convective thermal reisistane on the rotor cover is higher than that of rotor by a factor of 10. Introduction of fin on internal surface of rotor and rotor cover resulted in a marginal heat transfer improvement. It is expected that, pertinent design and optimization of the fins can further bring down the maximum temperature rise.