Effect of metal foam thickness on the conduction and convection heat transfer for a flat plate with metal foam impinged by multiple jets

Abstract

ABSTRACT The influence of metal foam thickness on the convection and conduction heat transfer is studied by measuring the local heat transfer of a smooth flat plate, attached and detached metal foamed flat plate under multiple jet impingement conditions. 27 jets of 3 mm diameter are introduced from a jet plate. These jets impinge on a thin stainless steel foil that serves as a targeted plate. The pitch of the jets is 4d in both the spanwise and streamwise directions. The spent fluid is exiting in all directions. The influence of metal foam thickness is investigated for an open-cell aluminum foam with 4, 8, and 12 mm thickness. The porosity of aluminum metal foam is 0.92. The pore density (pores per inch) is 20 PPI. The local heat transfer is measured using infrared thermography and a thin metal foil technique. A smooth flat plate impinged by multiple jets serves as a reference case. The evaluation of the convection and conduction heat transfer offered by the metal foamed flat plate is obtained with the help of the detached foam configuration. The jet diameter-based Reynolds number ranges from 2500 to 15000. The range of the jet to plate spacing covered is 3d to 6d. Depending on the metal foam thickness, the metal foamed flat plate offers additional hydraulic resistance to the jet flow and conduction effect. The additional hydraulic resistance attenuates the convective heat transfer and is represented by attenuation factor (α). For metal foam having 4, 8, and 12 mm thickness, the attenuation factor is around 1.11, 0.99, and 0.64, respectively. The conduction effect offered by metal foam is responsible for the enhancement of the heat transfer. The conduction effect is represented as an enhancement factor (E). For metal foam having 4, 8, and 12 mm thickness, the enhancement factor is around 1.51, 1.58, and 2.32, respectively. The conduction effect presented in the metal foamed flat plate dominates over the attenuation in the convective heat transfer. The overall enhancement offered by 4, 8, and 12 mm metal foamed flat plate is around 1.67, 1.56, and 1.48, respectively.