Numerical Prediction of Heat Exchanger Performances for a Hybrid Electric Propulsion Aircraft Concept

Abstract

In order to reduce the overall emissions of aviation hybrid electric propulsion concepts have a great potential meeting this challenge. For fuel cell applications heat exchangers are required to dissipate the waste heat produced by the fuel cell. The integration of the heat exchangers has an impact on the aircraft aerodynamics which in turn is influencing the flow through the cooler duct. This paper presents the first applications of a new approach in the DLR TAU Code to model a heat exchanger using the body force method in the Flowsimulator framework. The results are verified and indicate that the approach is robust and properly resolving the underlying physics. First applications with the new method are shown for a fuselage-mounted heat exchanger concept. Several TAU specific and geometrical sensitivity studies are presented to get a detailed representation of the flow characteristics of an integrated heat exchanger and the impact of the heat exchanger integration on the overall aircraft aerodynamics. Within the examinations the influence of the grid refinements, the turbulence models and the freestream velocity were analyzed. Furthermore, the influence of the location of a RamAir-heat exchanger concept on the fuselage of an aircraft, the influence of diffuser and nozzle length, and initial investigations of the influence of the nozzle outlet cross-section area were assessed.