Effective thermal conductivity of rough spheres packed bed

The effective thermal conductivity, ke, rigorously defined on the basis of the local volume averaging method, is an important parameter in porous media. The experimental and numerical results available in literature demonstrate that the ke value is influenced by several parameters such as thermal and mechanical properties of the multiphase porous medium, phase volumetric fractions, geometrical shape and spatial distribution of the solid matrix and, in particular, contact area between the solid particles. In the present paper, a numerical method to evaluate the effective thermal conductivity from the packing structure of a packed bed of mono-sized spheres is validated through the comparison with experimental data, obtained by the authors from an apparatus designed and build up for this purpose. The effects of the spheroid surface roughness is examined as the applied contact load and the solid matrix material vary. In particular packed beds of steel and aluminum spheroids saturated by a static gas (air) have been studied. Unfortunately, the lack of published results including an accurate measurement of the particle roughness does not allow the authors to compare their numerical results with other researchers’ experimental data.