Long-domain simulation of flow in open-cell mesoporous metal foam and direct comparison to experiment

Abstract

Open-cell metal foam is a class of modern mesoporous media that possesses high thermal conductivity, large accessible surface area per unit volume and high porosities (often greater than 90%). When a fluid passes through the foam, the internal structure of the foam, which is web-like, produces a complex flow field including flow reversal and vigorous mixing. All of these attributes make metal foam a very attractive core for many engineering applications, e.g. heat exchangers, filtration devices and reactors. The rather complex and intrinsically random architecture of the foam is extremely difficult to capture exactly. In this paper, we use a unit cell geometrical model to numerically investigate the flow field and pressure drop inside commercial open-cell aluminum foam. The Navier–Stokes equations are solved directly, and velocity and pressure fields are obtained for various approach velocities using a commercial numerical package. The details of the modeling process are given in this paper. The pressure drop results are compared to the Forchheimer equation, from which the permeability and form drag coefficient are calculated. Comparisons to experimental data were also carried out. The commercial foam that was used in the experiment had 10 pores per inch and porosity of 90% approximately. Air was forced to flow inside the foam using an open-loop wind tunnel. Good agreement between the modeling and experimental results are obtained for low velocities, with the agreement becoming poorer for larger velocities. The results for the low-velocity range are encouraging and lend confidence to the modeling approach, which paves the way for investigating other phenomena inside the foam, using the same unit cell, e.g. heat transfer. The limitations of the models are outlined and discussed.