Hydrodynamics of Taylor Flow in Vertical Capillaries: Flow Regimes, Bubble Rise Velocity, Liquid Slug Length, and Pressure Drop

TLDR: Two-phase flow hydrodynamics in vertical capillaries of circular and square cross sections were experimentally studied, using air as the gas phase and water, ethanol, or an oil mixture as the liquid phase as discussed by the authors.

Abstract: Two-phase flow hydrodynamics in vertical capillaries of circular and square cross sections were experimentally studied, using air as the gas phase and water, ethanol, or an oil mixture as the liquid phase. The capillary hydraulic diameters ranged from 0.9 mm to 3 mm, with the superficial gas and liquid velocities covering a span of 0.008−1 m/s, which is typical of that obtained in monolith reactors. Using a high-speed video camera, four distinct flow regimes were observed within the range at which experiments were conducted:  bubbly, slug-bubbly, Taylor, and churn flows. Annular flow was observed at excessively high gas and low liquid flow rates, well beyond those of interest to this study. Based on the definition of a two-class flow regime, the combination of two parametersthe slip ratio (S) and the ratio of the superficial gas velocity to two-phase superficial velocity (UG/UTP)was observed to be suitable for determining the transition from homogeneous flow to nonhomogeneous flow. The influence of capill...