Influence of pore density on thermal development in open-cell metal foam

Abstract

Herein heat transfer measurements due to water flow in commercial open-cell aluminum foam confined by a cylindrical shell, which was heated by a constant heat flux, are described. Two kinds of commercial foam were tested: 10 and 40 pores per inch (ppi). Measurements included wall temperature along flow direction as well as average inlet and outlet temperatures of water. Flow rates ranged from Darcy to Forchheimer regimes. The wall temperature along the foam, as well as the local Nusselt number lucidly displayed thermal entry effects leading to thermal fully-developed conditions. The thermal entry length was about 2.9 pipe diameters (150mm) for 10-ppi and 2.4 pipe diameters (122mm) for 40-ppi foam; these were same for Darcy and Forchheimer flow regimes. It can be stated that the thermal entry length in open-cell metal foam was found to be significant and different from its porous-media analytically-predicted values and behavior. Moreover, the thermal entry length in metal foam was found to inversely proportional to the pores density but in a weak manner.