Numerical development of a heat transfer and pressure drop porosity model for a heat exchanger for aero engine applications

Heat exchangers are used in various applications. In a typical CFD approach, where it is necessary to model the flow in a device with a heat exchanger, a first step can be the construction of a very detailed mesh modeling each flow passage inside the device. However, this approach can lead to very fine grids with high demands of CPU power and memory requirements. In order to overcome this problem, the presence of the heat exchanger can be modeled as a porous medium having the same thermal and flow behaviour as the original device. In this work, a generalized porous medium model was developed for a heat exchanger designed to be used as a heat recuperator for an aero engine. For the porosity model a modified anisotropic formulation of the Darcy–Forchheimer pressure drop law was introduced together with a heat transfer model in the form of a Nusselt–Reynolds–Prandtl numbers correlation. For the derivation of the pressure drop and heat transfer coefficients various data from experimental measurements were used. In order to assess the performance of the proposed model, CFD computations were performed. For all the examined cases, the CFD results were in close agreement with the experimental data and thus, the developed porosity model could sufficiently, describe the macroscopic behaviour of the heat exchanger.