Abstract
Electrification of transportation in the aviation industry is challenging in part due to the high power densities necessary for propulsion using electric motors. A commercial, narrow-body aircraft would require electric motor systems having >12 kW/kg power density, over twice the current state-of-the-art. One major limitation to increasing power density are limits on the operating temperature. Electric motor windings, which are wrapped in insulation, produce the majority of the heat in the motor. Positioning the coolant closer to the windings so as to decrease the overall thermal resistance between the heat source and sink is therefore a promising route toward enabling higher power densities. In this study, an additively manufactured stator subsection prototype with embedded microchannels is used to demonstrate two-phase cooling at different mass flow rates of R1233zd(E). Compared to single-phase cooling, utilizing two-phase flow provides higher heat transfer coefficients, which have increasing importance on reducing the overall resistance when the coolant is embedded close to the heat source, as well as offering a nearly isothermal coolant at the saturation temperature independent of mass flux. This prototype test section, which has been demonstrated for continuous operation at 30.4 A/mm2, is experimentally characterized at five flow rates between 0.33 g/s and 0.83 g/s. The average coil temperature is demonstrated to be insensitive to mass flow rate, as is desired for practical operation, owing to the high effective heat capacity rate when operating in the two-phase regime. Instrumentation of the test section with wall-embedded thermocouples enables decomposition of the total coil temperature rise into the conductive and convective thermal resistance components. The incorporation of two-phase flow reduced the convective thermal resistance by 77 %. Thermal models for each of these resistance components are developed to validate experimental findings, and further, to allow performance prediction in context of up-scaling to the full motor assembly and higher operating powers.
Date of this Version
5-25-2025
Published in:
R. Regan, K. Saviers, W. Zhao, A. Kuczek, J. Tangudu, and J.A. Weibel, Embedded two-phase cooling in an additively manufactured stator prototype for a novel high-power-density electric motor concept, Applied Thermal Engineering 276, 126918, 2025.
Link to original published article:
https://doi.org/10.1016/j.applthermaleng.2025.126918
Comments
This is the author-accepted manuscript of R. Regan, K. Saviers, W. Zhao, A. Kuczek, J. Tangudu, and J.A. Weibel, Embedded two-phase cooling in an additively manufactured stator prototype for a novel high-power-density electric motor concept, Applied Thermal Engineering 276, 126918, 2025. Copyright Elsevier, it's made available here CC-BY-NC-ND, and the version of record is available at DOI: 10.1016/j.applthermaleng.2025.126918.