Modeling investigation of mass transfer of gas–liquid–liquid dispersion systems

A flow map for core/shell microdroplet formation in the co-flow Microchannel using ternary phase-field numerical model

Core/shell microdroplets formation with uniform size is investigated numerically in the co-flow microchannel. The interface and volume fraction contour between three immiscible fluids are captured using a ternary phase-field model. Previous research has shown that the effective parameters of microdroplet size are the physical properties and velocity of the three phases. By adjusting these variables, five main flow patterns are observed in numerical simulations. A core/shell dripping/slug regime is observed when the inertia of the continuous phase breaks the flow of the core and shell phases and makes a droplet. In the slug regime, the continuous phase has less inertia, and the droplets that form are surrounded by the channel walls, while in the dripping regime, the shell phase fluid is surrounded by the continuous phase. An increase in continuous-fluid or shell-fluid flow rate leads to dripping to a jetting transition. When three immiscible liquids flow continuously and parallel to one another without dispersing, this is known as laminar flow. In the tubing regime, the core phase flows continuously in the channel's central region, the shell phase flows in the annulus formed by the core phase's central region, and the continuous phase flows between the shell phase fluid and channel walls. In order to discriminate between the aforementioned flow patterns using Weber and Capillary numbers and establish regime transition criteria based on these two dimensionless variables, a flow regime map is provided. Finally, a correlation for shell thickness using shell-to-core phase velocity ratio and conducting 51 CFD simulations was proposed.

Manipulation of gas-liquid-liquid systems in continuous flow microreactors for efficient reaction processes

Gas-liquid-liquid flow in microreactors holds great potential towards process intensification of operation in multiphase systems, particularly by a precise control over the three-phase contact patterns and the associated mass transfer enhancement. This work reviews the manipulation of gas-liquid-liquid three-phase flow in microreactors for carrying out efficient reaction processes, including gas-liquid-liquid reactions with catalysts residing in either liquid phase, coupling of a gas-liquid reaction with the liquid-liquid extraction, inert gas assisted liquid-liquid reactions and particle synthesis under three-phase flow. Microreactors are shown to be able to provide well-defined flow patterns and enhanced gas-liquid/liquid-liquid mass transfer rates towards the optimized system performance. The interplay between hydrodynamics and mass transfer, as well as its influence on the overall microreactor system performance is discussed. Meanwhile, future perspectives regarding the scale-up of gas-liquid-liquid microreactors in order to meet the industrial needs and their potential applications especially in biobased chemicals and fuels synthesis are further addressed.