Gas–liquid two-phase flow splitting at microchannel junctions with different branch angles

Review on Microbubbles and Microdroplets Flowing through Microfluidic Geometrical Elements

Two-phase flows are found in several industrial systems/applications, including boilers and condensers, which are used in power generation or refrigeration, steam generators, oil/gas extraction wells and refineries, flame stabilizers, safety valves, among many others. The structure of these flows is complex, and it is largely governed by the extent of interphase interactions. In the last two decades, due to a large development of microfabrication technologies, many microstructured devices involving several elements (constrictions, contractions, expansions, obstacles, or T-junctions) have been designed and manufactured. The pursuit for innovation in two-phase flows in these elements require an understanding and control of the behaviour of bubble/droplet flow. The need to systematize the most relevant studies that involve these issues constitutes the motivation for this review. In the present work, literature addressing gas-liquid and liquid-liquid flows, with Newtonian and non-Newtonian fluids, and covering theoretical, experimental, and numerical approaches, is reviewed. Particular focus is given to the deformation, coalescence, and breakup mechanisms when bubbles and droplets pass through the aforementioned microfluidic elements.

Dynamics of partially obstructed breakup of bubbles in microfluidic Y-junctions

For revealing the dynamics of partially obstructed breakup of bubbles in microfluidic Y-junctions, the combination of dimensionless power-law and geometric model was applied to study the effects of capillary number, bubble length, and channel angle on the bubble rupture process. In the squeezing process, the gas-liquid interface curve follows the parabolic model. For the evolution of the bubble neck during breakup, the increase of the bubble length, the channel angle, and the capillary number leads to the decrease of the focus distance α. The chord m increases with the increase of the capillary number and the decrease of the bubble length, and it would reach the maximum value when the channel angle is 90°. In the fast pinch-off stage during bubble breakup, the bubble's neck curve no longer conforms to the parabolic model so the focus and chord no longer exist. For the evolution of the bubble head during breakup, the value of γ approaches 1 with the increase of the capillary number and the bubble length, and with the close of the channel angle to 90°. It is found that the quadrilateral model can be applied for the partially obstructed rupture of bubbles in the symmetrical microfluidic Y-junction.

Phase Split in T-Junction Mini Channel – A Numerical Study

Extracting natural gas and crude oil from deep wells requires a thorough understanding of multi phase flow phenomena. Designing of micro reactors employing different fluids requires similar understanding on a micro scale. Gas-Liquid two-phase flow mixing and separation commonly occur in such oil exploration and recovery on a macro scale and in case of micro fluid reactors in a micro scale. In this paper, two-phase flow mixing and separation is analysed for a horizontal channel with internal diameter 2.50 mm and a length of 202.5 mm. The numerical results obtained during two-phase flow mixing are validated with experimental results by employing image processing techniques. A numerical model is developed to study mixing and separation characteristics of slug flow regime. The separation efficiency of the T-junction partial separator for various superficial velocities, viscosity, surface tension and separation angles is analysed. The analysis will be useful for designing mini/micro reactors.

A convenient numbering-up strategy for the scale-up of gas–liquid photoredox catalysis in flow

An operationally simple numbering-up strategy for the scale-up of gas–liquid photocatalytic reactions was developed, which provides an excellent flow distribution (SD_w < 10%).