The Impact Of Conduction Shape Factor In Volume Averaged Calculations Of Heat Transfer In Permeable Porous Materials

Abstract

Extended Abstract Porous materials like metal and graphitic foams are seeing increased use in heat transfer devices due to their high solid-phase conductivity and area-to-volume ratios. The internal structures of these materials can be extremely complex, but accurate characterization of the foam properties in terms of permeability, inertial losses, interstitial exchange and effective conductivity are critical for being able to consider such materials in design and application. Recent literature exists for characterizing permeable porous materials by conducting pore-level simulations on idealized geometric models [1-2] or geometric models generated by scanning samples of the porous media [3-4]. In such cases, a given geometric structure is discretized and simulations are conducted to obtain direct solutions to the mass, momentum and energy equations under laminar or turbulent flow conditions. These simulations can be used to obtain integral quantities characterizing the resistance to fluid passage, convective exchange and thermal dispersion, all of which are required for analogous simulations conducted using the volume-averaged (porous-continuum) approach. In addition to flow resistance and interstitial heat exchange, accurate information must be provided to characterize the solid phase conduction, which because of the complex shape, is a function of both solid-phase conductivity and a conduction shape factor, which characterizes the departure of the conduction path from being straight and of uniform cross-section [5-6]. In the present study, spherical-void-phase representative elemental volumes developed using the Discrete Element approach described in Dyck & Straatman [7] were produced over the range of porosities 0.70 ≤ ε ≤ 0.85 and for