Effect of channel size on liquid‐liquid plug flow in small channels

Dimitrios Tsaoulidis,Panagiota Angeli

doi:10.1002/aic.15026

Abstract

The hydrodynamic properties of plug flow were investigated in small channels with 0.5‐, 1‐, and 2‐mm internal diameter, for an ionic liquid/aqueous two‐phase system with the aqueous phase forming the dispersed plugs. Bright field Particle Image Velocimetry combined with high‐speed imaging were used to obtain plug length, velocity, and film thickness, and to acquire velocity profiles within the plugs. Plug length decreased with mixture velocity, while for constant mixture velocity it increased with channel size. Plug velocity increased with increasing mixture velocity and channel size. The film thickness was predicted reasonably well for Ca > 0.08 by Taylor's (Taylor, J Fluid Mech. 1961;10(2):161–165) model. A fully developed laminar profile was established in the central region of the plugs. Circulation times in the plugs decreased with increasing channel size. Pressure drop was predicted reasonably well by a modified literature model, using a new correlation for the film thickness derived from experimental values. © 2015 American Institute of Chemical Engineers AIChE J, 62: 315–324, 2016

Highlights

IntroductionTwo-phase flows (gas-liquid, liquid-liquid) in small channels have found numerous applications in, among others, (bio)chemical analysis and synthesis, fuel cells, thermal management systems, separation processes (e.g., solvent extraction), emulsification, and polymerization, driven by demands on sustainable and efficient continuous processing.[1,2] Small scale devices allow fast mixing and enhanced mass transfer because of features such as thin fluidic films, high specific interfacial areas, recirculation within phases, and convection induced by surface tension gradients.[3]
Two-phase flows in small channels have found numerous applications in, among others,chemical analysis and synthesis, fuel cells, thermal management systems, separation processes, emulsification, and polymerization, driven by demands on sustainable and efficient continuous processing.[1,2] Small scale devices allow fast mixing and enhanced mass transfer because of features such as thin fluidic films, high specific interfacial areas, recirculation within phases, and convection induced by surface tension gradients.[3]A common configuration during the flow of two immiscible liquids in small channels is the plug pattern where one phase forms elongated drops with size larger than the channel size, separated by continuous phase slugs
This finding has an important impact on the design of a small-scale devices, as plug length for constant flow rates is related to the number of plugs and to interfacial area available for mass transfer

Summary

Introduction

Two-phase flows (gas-liquid, liquid-liquid) in small channels have found numerous applications in, among others, (bio)chemical analysis and synthesis, fuel cells, thermal management systems, separation processes (e.g., solvent extraction), emulsification, and polymerization, driven by demands on sustainable and efficient continuous processing.[1,2] Small scale devices allow fast mixing and enhanced mass transfer because of features such as thin fluidic films, high specific interfacial areas, recirculation within phases, and convection induced by surface tension gradients.[3]. A common configuration during the flow of two immiscible liquids in small channels is the plug (slug or segmented) pattern where one phase forms elongated drops (plugs) with size larger than the channel size, separated by continuous phase slugs. From the various configurations that have been used to generate plug flow (e.g., flow focusing, Y- or T-junction inlets), the T-shaped one is very common.[4] Plug formation in small channels is mainly affected by the interfacial and shear forces, that dominate the flow.

Methods

Results

Conclusion