Hydrodynamics of trickling flow in packed beds: Relative permeability concept

Liquid holdups and pressure drops for gas and liquid concurrent flow in packed beds were measured experimentally. To calculate the Ergun type constants, pressure drops were also measured for single- (gas) -phase flow through the same packings. These measurements reveal that the Ergun type inertial constant depends on the particle shape. The beds were packed with porous and nonporous spheres, cylinders, extrudates, and Raschig rings. The experimental data were analyzed using the concept of relative permeabilities. The liquid-phase relative permeability, correlated well with the reduced liquid saturation in a unique power-law form for all particles independent of their shape. The gas-phase relative permeability as a function of the gas-phase saturation followed the same law, but the exponent depends on the particle shape and gas-phase Reynolds number. Predicted and experimental values for liquid holdups for all particle shapes agreed well with mean relative deviations less than 10%. Predictions of pressure drops for spherical particles, cylinders, and extrudates are at least as accurate as other less rigorous correlations (mean relative errors between 25 and 40%). Pressure drop predictions for Raschig rings are poorer (mean relative deviations of 90%), reflecting in part the variations in pressure drops from experiment to experiment with these particles.