Heat transfer measurements for non-Darcy flow in 10-ppi metal foam

Metal foam is a class of porous media with very high porosity (around 90%) and a large surface area density. The foam internal structure is web-like of thin ligaments surrounding cells that are open to flow. This structure promotes thermal dispersion because it offers a lot of mixing of a flowing fluid. Break up and inception of the boundary layers are phenomena adding to the convective heat transfer. The thermal conductivity of the solid phase of metal foam is also high. Because of all these attributed, metal foam is an excellent heat exchanger technology. There is a need for more experimental data regarding heat transfer in metal form. In this paper, experimental heat transfer data for water flow in commercial open-cell aluminum foam cylinder heated at the wall by a constant heat flux (14,998 W/m2 and 26,347 W/m2), is presented. The foam had 10 pores per inch (ppi) and a porosity around 87%. The measurements included wall temperature along flow direction as well as average inlet and outlet temperatures of the water. Flow speeds were in the non-Darcy regimes: transitional and Forchheimer flow regimes. The behavior of the wall temperature clearly shows thermal development conditions. The experimental Nusselt number is presented as a function of axial distance in flow direction, and showed what seemed to be periodic thermal development. The experimental data can be used for validation of other analytical solutions. The results can also be used to verify numerical models and metal-foam heat exchangers used in air-conditioning for example