Multiphase Flow in a Microchannel

Abstract

Multiphase flow in a microchannel is the basis for the application of microchemical process and flow chemistry. The gas-liquid two-phase flow, liquid-liquid two-phase flow, and gas-liquid-solid three-phase flow in a microchannel are introduced. Due to the interplay of the interfacial phenomena and the confinement effect at microscale, various flow patterns of the multiphase flow in a microchannel occur, such as Taylor bubble flow, bubbly flow, churn flow, parallel flow, and annular flow for gas-liquid two-phase flow (tiny droplet, plug droplet, annular flow, and parallel flow for liquid-liquid two-phase flow). Bubbles and droplets are the typical flow patterns for multiphase flow in a microchannel. The mechanism and manipulation for the generation, breakup, and coalescence of bubbles and droplets in a microchannel are highlighted. The interface evolution for the bubble dynamics and droplet dynamics in a microchannel is reported, to shed light on the interfacial instability mechanism. Bubbles or droplets can be generated in a microchannel via the dripping, jetting, squeezing, or tip-streaming, by various forces exerted on the gas-liquid interface or liquid-liquid interface such as interface tension force, viscous force, and inertia. Various breakup mode and coalescence mode for bubbles and droplets in a microchannel are observed. The interfacial mass transfer across the gas-liquid interface via a bubble and the liquid-liquid interface via a droplet is analyzed. Due to the increased specific surface area, the related mass transfer process can be intensified. Multiphase flows involving particles are also presented such as for particle separation and nanomaterials synthesis.