Effect of packing geometry on heat and mass transfer in stacked beds of spheres

Experimental measurements have been made of the simultaneous rates of mass and heat transfer for the surface evaporation of water into air from a simple cubic, a rhombohedral, and two orthorhombic assemblages of uniform celite spheres, in the particle Reynolds number range 300-1200. The measurements were confined to the pre-determined constant rate drying period of the spheres. No appreciable differences in mass and heat transfer factors were found for the various assemblages, except for the cubic, which exhibited lower transfer factors at the higher Reynolds numbers. This is explained qualitatively by the fact that the cubic configuration shows a considerably larger free projected cross-sectional area than the others, thus allowing for greater fluid channelling. Various methods proposed by investigators of randomly packed beds for correlating mass transfer by the inclusion of fractional void volume functions in the mass transfer factor and/or the Reynolds number were tested for the stacked assemblages. None of these methods completely correlated the results. Galloway's fluid friction data for the two orthorhombic assemblages were recalculated and showed similar friction factors to those obtained by Martin for identical packings of brass spheres. Ergun's criteria for complete and for no longitudinal fluid mixing were applied to the various assemblages. The results for the cubic assemblage suggest the possibility of considerable air mixing therein.Applied Science, Faculty ofChemical and Biological Engineering, Department ofGraduat