The overarching goal of this work is to address the design of next-generation, high torque density electrical machines through numerical optimization using an integrated thermal-electromagnetic design tool that accounts for advanced cooling technology. A parametric thermal model of electric machines was constructed and implemented using a finite difference approach incorporating an automated, self segmenting mesh generation. A novel advanced cooling technology is proposed to improve thermal transport in the machine by removing heat directly from the windings via heat exchangers located between the winding bundles. Direct winding heat exchange (DWHX) requires high convective transport and low pressure loss. The heat transfer to pressure drop tradeoff was addressed by developing empirically derived Nusselt number and friction factor correlations for micro-hydrofoil enhanced meso-channels. The parametric thermal model, advanced cooling technique, Nusselt number and friction factor correlations were combined with a parametric electromagnetic model for electric machines. The integrated thermal-electromagnetic model was then used in conjunction with particle swarm optimization to determine optimal conceptual designs. The Nusselt number correlation achieves an R² value of 0.99 with 95% of the data falling within ± 2.5% similarly the friction factor correlation achieves an R² value of 0.92 with 95% of the data falling within ± 10.2%. The integrated thermal-electromagnetic design tool, incorporating DWHX, generated an optimized 20 kW permanent magnet electric machine design achieving a torque density of 23.2 N-m/L based on total system volume.

This study numerically examines the heat transfer and pressure drop performance of finned tube heat exchangers with staggered and inline tube layout for a range of tube pitch. The first part of the thesis considers the case where the heat exchanger is placed in fully ducted airflow. The simulations indicate that the performance reduced considerably for the staggered tube layout with an increase in the tube pitch, but a minimal difference for the inline tube arrangement. The effects of other geometrical parameters like fin pitch and the number of tube rows are then presented. Finally, a correlation for fin and tube heat exchangers with inline tube layout is proposed based on 280 simulations for 70 different configurations. The proposed heat transfer correlation can describe the database within ±8% discrepancy while the friction factor correlation can correlate the dataset within a ±10% discrepancy. The mean deviations for heat transfer and friction factor correlations are 4.3% and 5.4%. An important factor that influences the performance of flat plate and finned tube heat exchangers is when there is bypass flow around the heat exchanger. The next section of this thesis numerically investigates the partially ducted inline fin and tube heat exchanger with side bypass. The effects of the side clearance and the Reynolds number on the heat transfer and the pressure drop performance of the heat exchanger are presented. The simulations indicate that the heat transfer performance depreciates by more than 25% for infinite side clearance. The study then compares the pressure difference observed for entry, exit and the friction pressure drop with the various correlations available in the literature. Finally, the heat transfer and pressure drop performance for staggered and inline tube layouts are compared. / Thesis / Master of Applied Science (MASc)