INTRODUCTION Major cities around the world are either implementing or considering the stringent environmental pollution regulations. This, along with the increasing price of fossil fuels and the growth of renewable energy has brought electric propulsion back to the market. The electric propulsion uses an electrical energy storage such as batteries or fuel cells, along with electric drives instead of an IC engine powertrain. Electric motor in an electric drivetrain can be incorporated in number of ways and hub motor, especially in direct drive configuration, offers a number of benefits such as improved efficiency, increased cabin space in four wheelers and weight reduction in two wheelers without affecting the ride and handling [ 1]. Figure 1. Exploded view of the motor (1. Endplate, 2. Rim, 3.Rotor core, 4. Magnet, 5. Winding, 6. Stator core, 7. Spider and 8. Non rotating shaft).Numerical and Experimental Investigation of Heat Flow in Permanent Magnet Brushless DC Hub Motor Muhammed Fasil, Daniel Plesner, Jens Honore Walther, Nenad Mijatovic, and Joachim Holbøll Technical University of Denmark Bogi Bech Jensen University of the Faroe Islands ABSTRACT This paper investigates the heat dissipation in the hub motor of an electric two-wheeler using lumped parameter (LP), finite element (FE) and computational fluid dynamic (CFD) models. The motor uses external rotor permanent magnet brushless DC topology and nearly all of its losses are generated in the stator. The hub motor construction restricts the available conductive paths for heat dissipation from the stator to the ambient only through the shaft. In contrast to an internal rotor structure, where the stator winding losses are diffused via conduction, here convection plays a major role in loss dissipation. Therefore, a LP thermal model with improved convection modelling has been proposed to calculate the temperature of the components inside the hub motor. The developed model is validated with the FE thermal model and the test data. In addition, CFD tools has been used to accurately model the internal and the external flow as well as the convective heat transfer of the hub motor. Finally, an optimization study of the hub motor has been carried out using the CFD model to improve heat transfer from the stator. CITATION: Fasil, M., Plesner, D., Walther, J., Mijatovic, N. et al., "Numerical and Experimental Investigation of Heat Flow in Permanent Magnet Brushless DC Hub Motor," SAE Int. J. Alt. Power. 4(1):2015, doi:10.4271/2014-01-2900.2014-01-2900 Published 10/13/2014 Copyright © 2014 SAE International doi:10.4271/2014-01-2900 saealtpow.saejournals.org 46Downloaded from SAE International by American Univ of Beirut, Saturday, July 28, 2018The hub motor investigated in this paper is taken from an electric two wheeler currently available in the market. The continuous rating of the motor is 750 W at 550 rpm and it has an external rotor radial flux permanent magnet brushless DC (PMBLDC) topology. The exploded view of the motor is shown in Fig. 1. The stator comprising of the stator core and the winding is attached to a non-rotating shaft via spider. The shaft is then connected to the two wheeler chassis. The wheel houses the rotor core and magnets and they are connected to the shaft via a set of endplates with bearing. An air gap of 0.5 mm separates the stator core and magnets. A good thermal design of an electric motor not only helps to limit the temperature of its components within the thermal limit of their materials, but also allows the overall size reduction of motor [2]. A detailed thermal study is essential in case of the PMBLDC hub motor as nearly all of its losses are generated in the stator and their construction restricts available conductive paths for the heat dissipation to ambient only through the shaft. In contrast to an internal rotor structure, where the stator winding losses are diffused via conduction, here convection plays a major role in dissipating the los