Comparison of metal foam heat exchangers to a finned heat exchanger for low Reynolds number applications

Due to its high porosity and large specific surface area, open-cell metal foam is an attractive material for heat transfer applications. In this article the performance of metal foam heat exchangers is compared to the performance of a bare tube bundle and the performance of an existing conventional louvered fin heat exchanger. A macroscopic model consisting of the Darcy-Forchheimer-Brinkman flow model and the thermal non-equilibrium energy model is used to perform two-dimensional simulations on metal foam heat exchangers. Because thermal design of heat exchangers is always a trade-off between heat transfer and pressure drop, both are considered together when evaluating the heat exchangers' performance. The foamed heat exchangers show up to 6 times higher heat transfer rate than the bare tube bundle at the same fan power. If the fins are replaced by metal foam while keeping the overall dimensions the same, the finned heat exchanger shows in all cases the best performance. However, a metal foam heat exchanger can outperform the finned heat exchanger if the frontal area is changed. Optimization is required to select the best foam parameters, material and dimensions. This clearly shows the potential of open-cell metal foam for high performance heat exchanger designs.