Design and Experimental Characterisation of an Additively Manufactured Heat Exchanger for the Electric Propulsion Unit of a High-Altitude Solar Aircraft

This paper presents design considerations of an air-cooled heat exchanger (HE) for a propulsion motor. The motor has been designed as a part of electric drive system for a high-altitude solar aircraft. The existing heat evacuation methods for such applications include predominantly forced air ventilation of the machine active parts through an open frame/motor housing. When considering numerous constraints associated with the airframe design, the effectiveness of such a cooling approach might be insufficient or have a detrimental impact on the system endurance. This is due to the resultant air flow via the motor body, which is rather difficult to reliably model or design for. In this work, the authors investigate a dedicated heat exchanger to assure a more measured design with superior cooling capability. To enable sufficient heat removal from the motor body, a metal additive manufacture (AM) was used in fabrication of the HE prototypes. Both design methodology and experimental results from tests on the HE/motor hardware demonstrators are discussed in detail. The research outcomes have shown that the use of the developed thermal management system offers a high level of motor/HE integration, lightweight design and a high removal rate of the generated heat.