Numerical Simulations of Liquid−Liquid Flows in Microchannels

Abstract

Liquid−liquid flows in microchannels are important to microreactors/microfluidic devices that are used to carry out liquid−liquid reactions, extractions, emulsifications, etc. In this work, we report numerical investigations of drop/slug formation and flow regimes for liquid−liquid (oil−water) flow in microchannels. The Volume of Fluid (VOF) method was used to simulate the dynamics of water drop/slug formation in silicon oil, and the predicted drop/slug shapes/lengths were compared with previous literature measurements [Garstecki et al., Lab Chip 2006, 6, 437−446]. The effects of flow rates of water and oil phases (0.019−0.417 and 0.004−0.14 μL/s, respectively), channel size, liquid−liquid distributor (T-junction and Y-junction), and liquid viscosity on liquid−liquid flow regimes and slug lengths were investigated. The predicted drop/slug formation dynamics/slug lengths agreed satisfactorily with the aforementioned Garstecki et al. literature measurements for Q water/Q oil in the range of 0.1−1.7. However, for Q w a t e r/Q oil > 1.7, unlike the (long) slug flow reported in the aforementioned Garstecki et al. literature, a parallel flow was observed in the numerical simulations. The effect of wall adhesion (contact angle) on the flow regimes and slug lengths was also investigated. The experimentally validated computational model will be useful to simulate mixing, transport processes, and chemical reactions in microchannels.

WITHDRAWN: Liquid–liquid flow regimes and mass transfer in various micro-reactors

“…The formation of parallel flow is reported to be favored in rectangular shaped channels [35] and for high phase viscosity ratios [39]. The contact angle of the continuous phase also impacts the stability of parallel flow and may change the flow regime at equal Capillary number [21,40,41]. The transition to parallel flow reduces the overall pressure drop through a channel due to a lubrication effect by the less viscous liquid.…”

Studies of plug formation in microchannel liquid–liquid flows using advanced particle image velocimetry techniques

“…The thin fluidic films and small fluid volumes improve heat and mass transfer rates which result in more uniform concentration and temperature fields and allow better process control compared to large scale systems; these features can enhance efficiency and reduce waste (Daw and Finkelstein 2006). Microchannel multiphase flows in particular have found many applications in areas such as chemical analysis and synthesis, pharmaceuticals processing and thermal management systems (Angeli and Gavriilidis 2008;Raj et al 2010). The increased surface to volume ratio in microchannels favours multiphase processes where interfacial mass or heat transfer are important.…”

Computational investigations of the mixing performance inside liquid slugs generated by a microfluidic T-junction

“…28 Nowadays, numerical simulations have provided an alternative way to understand the fundamental fluid dynamics. While the majority of the numerical studies have been carried out to understand the hydrodynamics of the slug formation process, 29,30 there are limited reports discussing about the mixing process inside slugs. Previous numerical studies carried out by Kashid et al 31 and Rhee and Burns 32 have adopted the moving frame method with pre-defined concentration field to study the mixing process within one slug or between the adjacent slugs.…”