Applying both their own assumptions and the mechanism of lateral mixing proposed by Ranz (20), the authors obtained theoretical formulas for effective thermal conductivities ke in packed beds. Previously reported experimental data were analyzed with these equations, and the usable data for predicition of ke were shown. In order to see the influence of both packing characteristics and temperature on the effective thermal conductivities, experimental data were obtained with air for beds with various kinds of packing, i.e., iron spheres, porcelain packings, cement clinker, insulating fire brick, and Raschig rings. Correlation of these data with Equation (15) showed that this equation adequately expressed the heat transfer mechanisms in packed beds with motionless gases, especially at hight temperatures.

The axial effective thermal conductivities of packed beds were determined by measuring the axial temperature gradients a t steady state, the heat being conducted in the direction opposite to that of air. The present experiments were carried out with the beds of glass beads, metallic balls, broken pieces of limestone, and Raxhig rings, taken in separate experiments.It was found that the axial effective thermal conductivity increases more with the increose of air flow than i t does in the case of radial conductivity. The axial effective thermal conductivity coincides with the radial conductivity when NE, + 0.

From studies of annular packed beds wherein the heat flows purely radially, the authors obtained the coefficients of heat transfer on the inner tube surface, as well as the mean effective thermal conductivities of bed. The inner and outer diameters of the annular packed bed were 22 and 70 mm. respectively, and the packings shown in Table 1 were used. The wall film coefficients obtained with air flowing axially through the bed were correlated for NReM < 600 by means of Equation (14).The coefficients of heat transfer for cylindrical packed beds reported previously by other observers were correlated also by Equation (14), with 0.054 used for values of αω in the range NReM < 2,000.Consideration of Equation (14) in terms of a theoretical model of heat transfer showed that it was reasonable to apply it for the prediction of wall film coefficient, especially for low Reynolds numbers.

Experiments of heat and mass transfer from the tube wall to the fluids flowing through the packed beds were carried out separately. In heat transfer air was used as the fluid, and several kinds of solid particles with low and high thermal conductivities were investigated to determine effective thermal conductivities and wall heat transfer coefficients. In mass transfer the dissolution rate of the coated material on the inner wall of the packed tube to the water stream was measured, and wall mass transfer coefficients were analyzed. It was found that a close similarity exists between the JH and JD factor for the wall coefficients in the turbulent‐flow region.

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