Experimental and numerical investigation of the flow field through a heat exchanger for aero-engine applications

An experimental and computational study for the flow development through a heat exchanger for aero-engine applications is presented. The heat exchanger consists of elliptic tubes in a U formation, the ends of which are attached to the collector pipe, which has a cylindrical cross section. In this way, two identical packages (named as matrices) are formed and located at a certain distance between them. The elliptic tubes are placed in a staggered arrangement. Detailed flow measurements using a 3-hole pitot-static probe were carried out on a 1:1 scale model of the heat exchanger in order to measure the pressure drop through the heat exchanger and the velocity distribution behind it. The flow through the heat exchanger was modeled with a computational fluid dynamics approach. The heat exchanger matrices were modeled using a porous medium assumption. The pressure drop through each element of the porous medium was linked to an effective local velocity. In order to check the validity of the computational modeling, the results were compared to the measured flow parameters such as pressure and velocity distributions. Two sets of modeling were performed assuming a laminar and a turbulent flow. The results showed that the laminar approach gave better results and this is supported by the corresponding Reynolds numbers, which indicated that the global flow field is transitional.