Abstract
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.
Highlights
Flow patterns are defined as the different types of spatial distribution of immiscible phases that develop as they flow simultaneously in a channel
This impact must be studied in detail, since the geometry is directly involved on the performance of practical applications, ranging from micro to macroscales
Good knowledge on two-phase flow hydrodynamics in millichannels and microchannels is important for the design, optimization, and control of structured microflow systems, since the physics governing bubble/droplet passing through microfluidic elements is really complex [22,23]
Summary
Flow patterns are defined as the different types of spatial distribution of immiscible phases that develop as they flow simultaneously in a channel. Within each flow pattern, the channel geometry has a large impact on the behaviour of characteristic hydrodynamic features This impact must be studied in detail, since the geometry is directly involved on the performance of practical applications, ranging from micro to macroscales. In the case of multiphase flows, these microfluidic elements include expansions, contractions, constrictions, obstacles, and T-junctions that can be used to promote the formation, breakup, or coalescence of microdroplets and microbubbles. Good knowledge on two-phase flow hydrodynamics in millichannels and microchannels is important for the design, optimization, and control of structured microflow systems, since the physics governing bubble/droplet passing through microfluidic elements is really complex [22,23]. The overall picture regarding two-phase flows in microfluidic geometrical elements is systematized
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