Heat transfer in beds of fine particles (heat transfer perpendicular to flow)

Effective thermal conductivites were evaluated for beds of fine glass beads from experimental data on heat transfer perpendicular to the direction of fluid flow. Results were obtained for a bead size range of 29 to 940 μ and for carbon dioxide, nitrogen, helium, and a C7 hydrocarbon liquid. The results showed that over the range of flow rate studied 0 to 80 lb./(hr.sq.ft.), or modified Reynolds number from 0 to 6.6, there was no effect of flow on the conductivity. Hence the measured stagnant conductivity k°e also satisfactorily represented heat transfer for flowing conditions. In view of this result, methods of predicting the stagnant conductivity were re-examined and a revised prediction method proposed. The equations are based upon a model which supposes energy to be transferred through a continuous fluid phase and through the solid particles by a solid-fluid series mechanism. The equations are compared with the data available in the literature.