Heat Release of Fuel Cell Powered Aircraft

Abstract

Using a hydrogen fuel cell as primary power supply for the aircraft propulsion system, the heat dumping poses a large challenge, since the generated heat transfer rate is of the same magnitude as the electric power generated. An appropriate liquid cooling system and corresponding heat exchanger are sized in a preliminary manner and their impact at the aircraft performance is assessed, among others the additional power demand and weight, but in particular the additional drag of the heat exchanger. These results can be considered as first order estimations. It is found that the propulsive power demand of a mid-size commercial aircraft is increased by 27.3% at cruise flight by installing a suitable heat exchanger. Corresponding dimensions are sized and favourable parameters of the heat exchanger are estimated. For example, best performance is achieved if the inlet velocity to the heat exchanger is reduced to 15% of the flight velocity, the diameter based Reynolds number of the heat transferring tubes is 3100, the length of the tubes is 0.217 m and the frontal area is 84% of the fuselage cross section. Due to large frontal area, the integration of the heat exchanger has been identified as a demanding task with considerable impact at the additional drag.