Investigation on millimeter-scale W1/O/W2 compound droplets generation in a co-flowing device with one-step structure

Pan, Dawei; Chen, Qiang; Zhang, Yinjuan; Li, Bo

doi:10.1016/j.jiec.2020.01.020

Cited by 18 publications

(4 citation statements)

References 30 publications

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“…The flow state of bullet-shaped droplets in the microchannel mainly depends on the characteristics of all the acting forces in the flow system. Generally, the main acting forces on the bullet-shaped droplet interface mainly include differential pressure force, shearing force, and Laplace pressure force. − The major forces during the bullet-shaped droplets moving in a square microchannel are demonstrated in Figure , where Δ P represents the pressure difference across the tail to the head of the droplet. Herein, the velocity of the liquid film around the droplet interface is much smaller than that of the droplet owing to the wall effect.…”

Section: Resultsmentioning

confidence: 99%

Effect of Viscosity on Liquid–Liquid Slug Flow in a Step T-Junction Microchannel

Yan

et al. 2022

Ind. Eng. Chem. Res.

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The multi-phase microflow hydrodynamics plays a significant role in the design of microreactors. The effects of two-phase viscosity on the hydrodynamics of liquid–liquid slug flow in a step T-junction microchannel was investigated systematically in this work. The paraffin oil and chitosan aqueous solution with different viscosities were used as the continuous and dispersed phase, respectively. The effects of various conditions on droplet size, droplet moving velocity, liquid film thickness, and pressure drop in the microchannel were studied and discussed. The results reveal that both dispersed and continuous phase viscosities have critical effects on the flow characteristics. Liquid film thickness, droplet velocity, and pressure drop are deviated from the conventional ideal model. Accordingly, two new semi-empirical models were established for calculating droplet velocity and liquid film thickness. The droplet velocity and liquid film thickness could be predicted by and , respectively. For the pressure drop, a modified model was developed by considering the real velocity of two phases, the geometric structures of microchannel, and physical properties. The predicted values by the modified model are in good agreement with experimental results, and the modified model has shown its good universality. This work could provide a more reliable guidance for the design of liquid–liquid microreactors.

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Section: Resultsmentioning

confidence: 99%

Effect of Viscosity on Liquid–Liquid Slug Flow in a Step T-Junction Microchannel

Yan

et al. 2022

Ind. Eng. Chem. Res.

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“…Some researchers had prepared millimeter-scale monodisperse double emulsions in a one-step coflowing microfluidic device, and developed a prediction model within ±10% error for droplet size based on the inner and outer droplet formation periods. 37 In summary, although the mechanisms of double emulsions generation regarding the flow patterns, size variation, and breakup dynamics in a coflowing microfluidic device have been extensively investigated, the involved multiphase flow systems only focus on the Newtonian fluids, and the investigation on the systems with the non-Newtonian fluid as the middle fluid is still lacking. Note that in numerous application fields double emulsions with non-Newtonian fluids as the middle fluids are usually required.…”

Section: Introductionmentioning

confidence: 99%

“…In brief, the factors that affect the sizes of double emulsions are complex, and it is necessary to propose a correlation model with several dimensionless numbers to predict the inner and outer diameters of the resultant double emulsions. Some researchers had prepared millimeter-scale monodisperse double emulsions in a one-step coflowing microfluidic device, and developed a prediction model within ±10% error for droplet size based on the inner and outer droplet formation periods . In summary, although the mechanisms of double emulsions generation regarding the flow patterns, size variation, and breakup dynamics in a coflowing microfluidic device have been extensively investigated, the involved multiphase flow systems only focus on the Newtonian fluids, and the investigation on the systems with the non-Newtonian fluid as the middle fluid is still lacking.…”

Section: Introductionmentioning

confidence: 99%

Effects of Rheological Properties of Non-Newtonian Middle Fluids on the Formation Dynamics of Double Emulsions in Coflowing Microfluidic Emulsification

Jiao,

Zhang,

Wang

et al. 2024

Ind. Eng. Chem. Res.

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Effects of the rheological properties of non-Newtonian middle fluids on the formation dynamics of double emulsions in coflowing microfluidic emulsification are systematically ascertained by both experimental investigation and numerical simulation with a volume of fluid-continuum surface force model. In the experiments, with non-Newtonian fluids as the middle fluids for the generation of double emulsions, six various flow regimes, including dripping, jetting, transition, nonbreakup, parallel, and multicore regimes, are distinguished, and the corresponding formation mechanisms of such distinct flow regimes are further comprehensively revealed by analyzing the flow field structures and viscosity distributions inside the double emulsions. Particularly, a large flow velocity of the outer fluid only contributes to the generation of a transition regime but not a jetting regime because of the shear-thinning property of the non-Newtonian middle fluid. The regimes in the flow pattern diagrams dependent on the capillary number of the outer fluid, the Weisenberg number of the middle fluid, and the Reynolds number of the inner fluid are obtained. Besides, the size variation laws of double emulsions under various operation conditions are also illustrated. As the flow velocity of the middle fluid increases, the inner diameter of the resultant double emulsions remains constant within a specific range because the increase of the flow velocity always results in the decrease of the middle fluid viscosity, thus determining the nearly invariant viscous shearing force acting on the inner fluid. Finally, the prediction correlations for the dimensionless inner and outer diameters of double emulsions with several key dimensionless numbers are established, and the prediction errors are within ±10%. The results of this study provide valuable guidance for the preparation of monodisperse double emulsions with non-Newtonian fluids as the middle fluids in a controllable and precise manner.

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“…A combination of three-phase flows with microfluidic technology has been widely investigated in recent decades in order to provide precise control and continuous operation 9 , 10 . The miniaturization of synthesis systems provides new possibilities for improved chemical synthesis, as well as a platform of biological and medical applications 11 . Core–shell microdroplets (CSMs) formation in microfluidic devices has a number of advantages: (1) improved processing precision and efficiency, (2) design flexibility for a multi-step platform, (3) quick turnaround results for fine tuning properties of shaped droplets, (4) cost savings from reduced raw material and reagent consumption, and (5) using significantly fewer potentially harmful chemicals and reagents allows for safer operations and a reduced impact on the environment 12 .…”

Section: Introductionmentioning

confidence: 99%

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

Bariki

Movahedirad

2022

Sci Rep

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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.

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Investigation on millimeter-scale W1/O/W2 compound droplets generation in a co-flowing device with one-step structure

Cited by 18 publications

References 30 publications

Effect of Viscosity on Liquid–Liquid Slug Flow in a Step T-Junction Microchannel

Effect of Viscosity on Liquid–Liquid Slug Flow in a Step T-Junction Microchannel

Effects of Rheological Properties of Non-Newtonian Middle Fluids on the Formation Dynamics of Double Emulsions in Coflowing Microfluidic Emulsification

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

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