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

Abstract

Taylor flow is a strategy-aimed flow to transfer conventional single-phase into a more efficient two-phase flow resulting in an enhanced momentum/heat/mass transfer rate, as well as a multitude of other advantages. To date, Taylor flow has focused on the processes involving gas–liquid and liquid–liquid two-phase systems in microchannels over a wide range of applications in biomedical, pharmaceutical, industrial, and commercial sectors. Appropriately micro-structured design is, therefore, a key consideration for equipment dealing with transport phenomena. This review paper highlights the hydrodynamic aspects of gas–liquid and liquid–liquid two-phase flows in microchannels. It covers state-of-the-art experimental and numerical methods in the literature for analyzing and simulating slug flows in circular and non-circular microchannels. The review’s main objective is to identify the considerable opportunity for further development of microflows and provide suggestions for researchers in the field. Available correlations proposed for the transition of flow patterns are presented. A review of the literature of flow regime, slug length, and pressure drop is also carried out.

Numerical investigation of gas–liquid and liquid–liquidTaylor flow through a circular microchannel with a sudden expansion

“…Recently, a comprehensive review on the hydrodynamics of Taylor flow through mini‐ and microchannels was published. [ 94 ] It shows the dependency of slug length on the properties of phases, volumetric flow rate ratio, gas holdup, and non‐dimensional numbers.…”

Effect of Inlet Contactors of Splitting Distributors for Parallel Microchannels

“…It should be noted that the hydrodynamics forms the basis for reaction/mass transfer inside the microchannels. Several experimental and simulation studies were conducted to investigate the hydrodynamics of multiphase flows (gas–liquid, liquid–liquid, gas–liquid–liquid) in a single microchannel. − It was reported that hydrodynamic parameters such as the formation/coalescence of droplets/bubbles/slugs and their respective lengths and flow patterns in a single microchannel were strongly dependent on the micro-/millichannel design, operating parameters, and fluid properties. However, numbering-up to the thousands of parallel channels required to match the industrial production scale throughput has many challenges.…”

“…It may lead to a decrease in the heat and mass transfer coefficient despite the inherent benefits of MSR. It should be noted that the significant factors that affect the maldistribution are channel geometry (size, shape, and aspect ratio), fluid distributors (T or Y), and fluid properties (density and viscosity of phases). ,,− …”

“…Moreover, the maldistribution of gas–liquid flows are addressed by flow nonuniformity in terms of length of gas bubbles/slugs inside the parallel micro-/millichannels. Several correlations were developed to predict the dimensionless length of gas bubbles/slugs in a single microchannel (refer to review article by Etminan et al). It was reported that the dimensionless length of bubbles/slugs are the function of capillary number (Ca) , Weber number ( We ), Reynolds number ( Re ), Eötvös number ( Eö ), fluid inlet contactor, and the ratio of dispersed phase flow rate to the continuous phase flow rate or ratio of velocity of dispersed phase to the velocity of the continuous phase.…”

Insights from a zeroth order analysis on steady streaming generated by an oscillating gas slug

“…Gas slugs are used in mass transfer limited reactions, drug delivery and other pharmaceutical operations in Lab-on-chip devices [18]. Previous studies focusing on combining gas slugs with acoustic streaming, have analysed applications in particles separation [9] and micromixing [19].…”