AIR-COOLED HEAT SINK FOR AN ELECTRICPROPUSION AIRCRAFT APPLICATION BASED ON THE MANIFOLD-MINICHANNEL CONCEPT

Abstract

The growing demand for efficient thermal management in high-power electric propulsion systems has driven the exploration of innovative cooling solutions for aircraft applications. This research investigates the feasibility of employing a manifold-microchannel heat sink to dissipate waste heat from a 500 kW electric motor designed for aviation use. Given the constraints of airborne systems, the heat sink must achieve a balance between high thermal performance and minimal hydraulic penalties, besides lightweight construction. Air is selected as the working fluid due to its simplicity, reliability, and weight advantages over liquid-cooling alternatives, eliminating the need for pumps and additional infrastructure while making use of the dynamic pressure of the free airstream for cooling.The study focuses on optimizing the heat sink's geometry and airflow distribution to ensure effective heat dissipation while maintaining the motor’s temperature below the critical threshold of 150°C. A combined numerical-experimental methodology was adopted. Parametric studies and CFD simulations informed the selection of channel and manifold dimensions, which were validated through experimental testing. Thermal-hydraulic characterization established a baseline performance across operating conditions representative of cruise and takeoff. Measured thermal resistance values ranged from 0.002 to 0.0032 K/W, while pressure drops remained below 1,500 Pa, satisfying thermal and hydraulic design constraints. When compared with a conventional straight-fin heat sink under equivalent pumping power conditions, the MMHS achieved up to 50% lower thermal resistance. Conversely, for a fixed thermal resistance, the MMHS reduced pressure drop by as much as a factor of 12. The study further provided the first experimental evidence of particulate fouling in MMHS configurations. Silica sand ingestion, with particle sizes below channel width, led to only an 8% increase in pressure drop that stabilized within 20 minutes, with negligible effect on thermal resistance. Glass beads with diameters exceeding the channel size produced larger pressure drop increases, in some cases nearing 40%, yet fouling remained localized. These results highlight the intrinsic resilience of MMHS systems, owing to the redundancy provided by thousands of parallel minichannels, in contrast to conventional straight-fin heat sinks that would experience rapid global clogging. Overall, this work demonstrates that cylindrical air-cooled MMHS systems can deliver high thermal performance, low hydraulic losses, and robust fouling tolerance, positioning them as a viable thermal management solution for next-generation electric propulsion motors. By expanding the MMHS concept beyond electronics to aviation applications, this dissertation contributes new experimental evidence, particularly on fouling behavior, and establishes a foundation for further optimization and integration of lightweight, reliable cooling technologies in electrified aircraft.