PERFORMANCE IMPROVEMENT OF HEAT EXCHANGERS USED IN A HYBRID ELECTRIC AIRCRAFT

Thermal management system analysis of a kW scale hybrid electric aircraft developed at the National Research Council of Canada (NRC) has been provided with the aim of assessing the cooling capacity and improving the efficiency. For the electric propulsion system of the aircraft, a series cooling loop has been designed that comprises a heat exchanger (radiator) and two pumps. As coolant travels through the motor and controller, it accumulates heat, then the heat is dissipated from the coolant passing through the radiator. From the calculated parameters for different demonstration flight phases of the aircraft, it is concluded that the current radiator design is limited by the air side resistance. This air thermal resistance comprises over 76% of the total thermal resistance in all flight phases. Therefore, a large frontal area to meet cooling needs is required. The potential of different methods for cooling improvement of the radiator were investigated and a new concept was suggested for heat transfer enhancement which is a passive enhancing method by applying different micro-fin roughness on the fins or coolant tubes of a radiator.