Flow regimes in foam-like highly porous media

Abstract

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Metal foam is a relatively new class of porous media. The internal morphology of the foam is composed of connected cells each having many ligaments that form a web. In addition, metal foam has very high porosity (often greater than 90%) and a large surface area density. These properties are exploited in many applications, e.g., filtration, heat exchange and reactors. Flow regimes, and transition from one to another, are critical for understanding energy dissipation mechanisms for flow through the foam. While this topic is well studied in traditional porous media, e.g., packed beds, it is not well understood for foam-like porous media such as metal, graphite and polymeric foams. The choice of an appropriate characteristic length for metal foam has also varied among researchers. Pressure drop characteristics such as the permeability and form/inertial drag coefficient are very divergent for metal foam. The current study is to shed some light on the above issues. In particular, a large set of experimental data for pressure drop of water flow in commercial aluminum foam having 20 pores per inch and a porosity of 87.6% was collected. The range of flow Reynolds number covered a few important flow regimes. The current data correlated very well using the friction factor based on the square root of the permeability (measured in the Darcy regime) as a function of Reynolds number based on the same length scale. It is shown that the same foam exhibits different values of its permeability and Forchheimer coefficient in different flow regimes. The finding of this study can help in numerical and analytical work concerning flow and heat transfer in foamlike porous media.