On the leakage flow around gas bubbles in slug flow in a microchannel

Abstract

The leakage flow is that liquid does not push gas bubbles and leaks through the channel corners. This leakage flow was confirmed by tracking particles moving in the liquid film with a double light path method and was quantified by tracking the gas-liquid interface movement. The results show that leakage flow varies during bubble formation process. The average net leakage flow Q net-leak in a bubble formation cycle at T-junction can be as large as 62.4% of the feeding liquid flow rate, depending on the liquid properties. Q net-leak for regular flow at main channel is much smaller, ranging from about 0 to 30% of the feeding liquid flow rate. The difference between the two leakage flows would lead to an increase in liquid slug length after generation. Finally, the effects of parameters such as phase flow rates, surface tension, and viscosity were investigated.

Formation of liquid–liquid slug flow in a microfluidic T‐junction: Effects of fluid properties and leakage flow

“…Falconi et al reported detailed velocity distribution in the film through three numerical methods and showed a local back flow region in the rear part of the liquid film for a regular slug flow. Although there are several studies that support significant leakage flow, it was not directly observed . Or more accurately, a complete route of leakage flow overtaking a bubble/droplet was not directly observed.…”

“…Different from most studies in literature, the present work focuses on the leakage flow which largely impacts the flow hydrodynamics and is still an important problem remaining unsolved . In rectangular channels, as bubbles/droplets cannot fill the corners, significant amount of liquid flows through the corners and bypasses them, leading to leakage flow.…”

The effect of liquid viscosity and modeling of mass transfer in gas–liquid slug flow in a rectangular microchannel

“…For the solving of the coupled equations, the mass transfer coefficient, the specific surface area, and Q f need to be defined. Q f is a problem unsolved for slug flow in microchannels, especially in rectangular channels . In this work, Q f is approximated by treating the channel cross‐section to be circular, similar to the treatment of Ładosz and Rudolf von Rohr .…”

“…Q f is a problem unsolved for slug flow in microchannels, especially in rectangular channels. [49][50][51] In this work, Q f is approximated by treating the channel cross-section to be circular, similar to the treatment of Ładosz and Rudolf von Rohr. 52 In this way, Q f can be obtained by integrating the liquid velocity profile in the slug, which is assumed to conform to the Poiseuille flow:…”

Hydrodynamics and Mass Transfer of Gas‐Liquid and Liquid‐Liquid Taylor Flow in Microchannels

“…In rectangular channels, the film has a different thickness along the angular coordinate [39,[71][72][73]. Also a significant amount of liquid can move in the back flow at the corners of the channel [74][75][76]. To find the flux of a continuous phase through a film, integration over the angular coordinate is necessary.…”