Heat and momentum transfer in the flow of gases through packed beds

Abstract

AbstractHeat and momentum transfer studies have been made for the flow of gases through fixed beds consisting of randomly packed, solid metallic particles. The experimental technique employed in these studies made possible for the first time the procurement of gas‐film heat transfer data under steady state conditions and in the absence of mass transfer effects. Electric current passed through the metallic particles of the bed created within the particles a steady generation of heat, which was continuously removed by gases flowing through the bed. Several direct temperature measurements of both gases and solids within the bed made possible the direct calculation of the heat transfer coefficient for the gas film to produce the Colburn heat transfer factor jh, which has been found to correlate with the modified Reynolds number, Reh = √ ApG/[µ(1 – ∈)φ]. The shape factor φ was established in these studies for cubes and cylinders and was found to be identical to their respective sphericities.Pressure‐drop measurements produced a friction factor fk of the Blake type, which yielded separate curves for each shape when correlated with the modified Reynolds number Rem. No simple relationship was found to exist between the heat transfer and friction factors. A single correlation of the pressure‐drop data was obtained for the modulus fkoφn when correlated with a Reynolds number of the type Rem = √ ApG/[µ(1 – ∈)]. The exponent n varies with the particle shape.Experimental runs have been carried out for 3/16, 1/4, 5/16‐in. spheres, 1/4 and 3/8‐in. cubes, and regular cylinders using hydrogen and carbon dioxide to extend the range of molecular weights beyond that of air, used for the majority of these runs. A particle‐size, column‐diameter effect was found to exist for both heat and momentum transfer. This effect becomes significant in the low Reynolds region.