Liquid film thickness of two‐phase slug flows in capillary microchannels: A review paper

Abstract

Two-phase Taylor flow has received considerable attention from researchers in recent decades due to its potential use in a wide variety of industrial and medical applications. A large number of experimental, analytical, and numerical efforts have been taken by researchers to understand the fundamental characteristics of two-phase flows and the relevant transport phenomena. This paper presents a comprehensive review of the hydrodynamics, flow pattern, and liquid film thickness in two-phase flows through mini-and microchannels with different cross-sectional geometry. This paper also reviews correlations that predict liquid film thickness in microchannels for gas-liquid and liquid-liquid flows. The variations of liquid film thickness are plotted over a wide range of capillary numbers for both experimental and computational studies. This study shows that the effects of cross-sectional area on the flow patterns and flow characteristics have not been sufficiently investigated by researchers, particularly for rectangular cross-sectional areas with different aspect ratios.

A Review on the Hydrodynamics of Taylor Flow in Microchannels: Experimental and Computational Studies

“…Many other definitions have been developed to describe the characteristics of multiphase flows, including fluid flow, and heat and mass transfers, which are presented in Table 1. It should be noted that due to the presence of more than one phase and the interaction between all phases involved in multiphase flow, the thermophysical properties have been expressed differently compared to those of a single-phase flow [3][4][5]. The ratio between interfacial and gravitational (buoyancy) effects…”

“…Correlations for film thickness measurements were summarized and the key effects of Capillary number (Ca) on film thickness were discussed in detail. Recently, Etminan et al [4] presented all of the correlations proposed for film thickness measuring in the literature. They found the best-fitted correlation between some experimental data and a wide range of Ca.…”

“…The quantitative attempts to correlate slug length, liquid film thickness (recently summarized by [4] in a comprehensive review paper), and pressure drop have been compared. These correlations include non-dimensional numbers, superficial velocity ratios, volumetric flow rate ratios, void fraction, and other thermophysical characteristics of phases.…”

A Review of the Methods of Modeling Multi-Phase Flows within Different Microchannels Shapes and Their Applications

“…The EE method is suitable for problems where the dispersed phase volume fraction is more than 10%. In this method, both discrete and continuous phases are modeled by the Eulerian approach [47][48][49][50][51][52]. Table 1 shows several investigations of multi-phase flows within micro-equipment.…”

Issue Highlights

“…In the figure, variations of liquid film thickness are presented for a wide range of capillary numbers from both experimental and computational studies. [1] A coupled hydrodynamic-biokinetic simulation of three-phase flow in an oxidation ditch using CFD Hossein Norouzi-Firouz, Mohammad-Hossein Sarrafzadeh, Reza Zarghami, Iman Moshiri-Tabrizi Optimization and innovation are necessary for many units in the water industry. Regarding the remarkable advancement of mathematical modelling and simulations through computers, a better insight into the processes is feasible.…”