Heat sink design and topology optimization of a DC/AC converter for a general aviation hybrid-electric aircraft

• Design of air-cooled heat sinks for hybrid-electric general aviation aircraft. • Dual-step optimization of heat sinks using semi-empirical models and CFD. • Heat sink via pseudo-3D topology optimization for high thermal load dissipation. • TO heat sinks reduce weight by 45 % and pumping power by 34 %. • TO heat sinks integrated into the digital twin of hybrid-electric aircraft. This work aims to explore the potential of topology optimization in the design of forced air-cooled heat sinks for inverters equipping hybrid-electric aeronautical propulsion systems. Compared to the automotive applications that are driving the electrification of the transportation sector, the design of heat sinks in aircraft requires minimizing not only the thermal resistance and pumping power of the fans, but also the weight and volume. The challenge is further made more difficult by ambient air temperature and density that vary with the aircraft’s altitude. Considering the inverter of a real aircraft equipped with a hybrid electric propulsion system, the authors first designed conventional heat sinks with finned configurations by applying semi-empirical formulations and then a free-form heat sink by exploiting topology optimization. Conventional heat sinks serve as a reference for carrying out the evaluation with heat sinks based on topology optimization. The latter prove to be characterized by superior performance as the thermal resistance is up to 7 % lower, the pumping power of the fan is reduced by 34 % at the same inlet velocity and the weight saving is around 45 %. Finally, the heat sinks were verified at the system level by having their models integrated into a completed aircraft model.