Scaled Test Program Strategy of Skin Heat Exchanger for Thermal Management in Hybrid Electric Regional Aircraft

The strategy developed to carry out a scaled test program aimed at reproducing the behavior of skin heat exchangers to alleviate the heat dissipation requirements in future hybrid electric propulsion regional aircrafts is presented. The test program is intended to reproduce the dimensionless thermal response characterizing the skin heat exchanger on a predefined nominal cruise flight operation, while conducting the tests in a wind tunnel operating at low velocities and near-standard atmospheric conditions. For that purpose, dimensional analysis is used to define the geometrical scale and approach flow conditions in the wind tunnel test program, so that the dimensionless parameters describing the skin heat exchanger thermal response resemble the ones taking place under nominal flight conditions. The validation of the scaling strategy is achieved by comparing dimensionless parameters characterizing the turbulent momentum and heat transfer processes taking place at the skin heat exchanger/airflow interface surface in the flight and wind tunnel environments, by using CFD analysis based on two-equation k – ϵ and SST RANS turbulence modeling. The comparison reveals that the adopted wind tunnel strategy is indeed capable of closely reproducing the heat transfer process taking place in the flight environment, thus paving the way to achieve mid TLR validation of the skin heat exchanger technology.