High-frequency oscillating water flow in highly-porous media : experimental results for 10-ppi metal foam

Abstract

It is well known that oscillating flow can increase heat transfer over steady-state flow. Inserting porous media in the path of a flow also enhances convection heat transfer. Combining these two effects (oscillating flow and porous media) is supposed to substantially augment heat transfer. In order to understand the heat transfer in such arrangement, one must first understand the flow behavior. Oscillating water flow in open-cell metal foam having 10 pores per inch (ppi) has not been reported in the literature. In this paper, main characteristics of oscillating water flow in 10-ppi open-cell metal foam is reported. The foam had a porosity of 87%. Three flow displacements 74.3, 97.2 and 111.5 mm were applied at the relatively high flow frequencies of 0.46, 0.58 and 0.69 Hz. The effect of flow displacement and frequency on important parameter is presented and discussed. The appropriately defined friction factor correlated well with the kinetic Reynolds number. Steady-state experiments were also conducted for Darcy and Forchheimer water flow through the same metal foam, and the permeability and form/inertial drag coefficient were obtained. Comparisons of the friction factor for oscillating and steady flows is presented. The results of this study are very likely applicable to similar foam-like highly porous media, and is critical for interpreting oscillating heat transfer in metal foam.