A comprehensive model for the pressure drop in vertical pipes and packed columns

A macroscopic approach is used to describe the hydrodynamics of a two-phase annular counter-current flow in inclined flow channels. This type of flow is characteristic for gas-liquid contact equipment as applied in packed columns. In this study, a distinction is made between the pressure drop caused by the geometry of the channels and the pressure drop caused by the friction on the gas-liquid interface. It is shown that the frictional forces on the interface have two components that either influence the Liquid interface velocity or induce waves on the interface. Special attention is paid to the description of the gas-liquid interaction. The interaction is described using an additional term on a undisturbed counter-current flow using a dimensionless expression. A set of three independent equation is derived, describing the liquid hold-up, the interface velocity and the different contributions to pressure drop as function of physical properties of both phase. The description is demonstrated on vertical pipes and packed columns containing either random or structured packing. Because of the general description, it is possible to predict the by liquid hold-up and pressure drop induced flood point in this equipment. (C) 2001 Elsevier Science B.V. All rights reserved.