An exhaustive search optimization of heat transfer and pressure drop in Kelvin's open cell foams

Thanks to their high effective thermal conductivity, specific surface area, and tortuosity, open-cell foams are well-known for their capability to enhance heat transfer in applications such as heat exchangers and volumetric solar air receivers. In the very recent years, innovative manufacturing techniques, including 3D designing and printing, have been looked very helpful to find foam morphologies that allow to maximize heat transfer and minimize pressure drop. Optimal foam structures can be obtained by means of pore-scale simulations, employing an exhaustive search with a bearable computational effort. A multi-objective optimization of convective heat transfer and pressure drop in Kelvin's foams with air is presented in this paper. A pore-scale numerical model, with a uniform heat flux at the solid/fluid interface, is used to predict the interfacial convective heat transfer coefficient, h_c, and pressure drop, Δp, in the foam. The cell size, porosity, cell anisotropy stretching factor, as well as the inlet velocity and the direction of the air, are assumed as the design variables for the optimization model, while the interfacial convective heat transfer coefficient and pressure drop are chosen as the objective functions to be maximized and minimized, respectively. Pareto fronts ranging from h = 110 W/m² K and Δp = 0.77 Pa to h_c = 460 W/m² K and Δp = 51 Pa are predicted, within which the optimum point for the chosen foam morphology, air velocity and direction can be selected, according to the chosen criterion.