CFD-PBM simulation of droplets size distribution in rotor-stator mixing devices

Double emulsions are widely spread in a number of applications, such as food, cosmetics and pharmaceutics. They are usually prepared in two steps, comprising the preparation of a first emulsion that is in a second step introduced in an external continuous phase. A number of phenomena may occur during the second step including breakage, coalescence, and escape that is aimed to be reduced to keep high the encapsulation efficiency. Suitable models of these phenomena are proposed in this work and incorporated into a population balance model (PBM) to allow predicting the evolution of the droplet size distribution (DSD) of the external macrodroplets as well as the release rate. During the considered short preparation time and the slow molecular diffusion of the encapsulated salt, the release rate was assumed to be mainly governed by the leakage of internal droplets, i.e. their release due to the breakage of the macro-droplets. The proposed leakage model is thus described as a function of the breakage rate of the macro-droplets. The model parameters involved in the different sub-models of the PBMs (breakup and coalescence kernels, leakage) were identified in experiments of W/O/W double emulsions prepared using a rotor stator. Then, the model was validated under various key process conditions, such as the internal water fractions (10 -40 %) and stirring rate. The dependence of the leakage parameter on the concentration of salt was also investigated. The macro-DSD was measured by Laser diffraction while the leakage rate was monitored by conductivity measurements.

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“…This kernel was used by Qin et al [40] to model the emulsification in a rotor-stator mixer, within a coupled CFD-PBM framework.…”

Section: Breakage Kernelmentioning

confidence: 99%

Modeling of double emulsions using population balance equations

Khadem

Sheibat‐Othman

2019

Chemical Engineering Journal

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“…In the past few years, several attempts have been made to deepen the understanding of break-up and coalescence phenomena by combining computational fluid dynamics (CFD) and population balance models (PBM). [126][127][128][129][130][131][132][133] In these works, the spatial dependencies of the break-up and coalescence rates are incorporated by simulating the geometry in question with a proper mesh and solving the equations with a finite elements method or similar. This methodology results in a greater physical accuracy but demands higher computational costs.…”

Section: Drop Breakage and Coalescence Processes In Liquid-liquid Dmentioning

confidence: 99%

Mechanisms and conditions that affect phase inversion processes: A review

2020

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The phenomenon of phase inversion occurs in liquid-liquid dispersions found in a variety of chemical engineering fields. From simple oil-water mixtures to complex polymeric systems, the operating variables that affect this physical phenomenon are discussed in this work. The contribution on this matter by a large number of researchers is critically assessed, outlining both coherent and conflicting results. A detailed review of the mechanisms by which phase inversion takes place is also provided. While this subject has been studied for the past fifty years, this multivariate nonlinear process is This article is protected by copyright. All rights reserved. not yet comprehensively understood, and this review article aims to describe the conclusions so far reached to provide insight for future research.

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“…In this regard, the variable drop diameter should be involved in transport equations during the simulation. Among different methods available, the CFD coupled with a population balance model (PBM), that is, the CFD–PBM approach, shows increasing interest to investigate two-phase flows in the literature. − …”

Section: Introductionmentioning

confidence: 99%

CFD–PBM Simulation of Liquid–Liquid Dispersions in a Pump-Mixer

Zhou

Wang

et al. 2021

Ind. Eng. Chem. Res.

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The approach coupling computational fluid dynamics and a population balance model (PBM) was adopted to simulate the hydraulic performance of liquid–liquid dispersions in a pump-mixer. Behaviors of the drop breakage and coalescence were considered in the PBM. To validate simulation methods and strategies, simulated drop size distributions were compared with experimental data and a good agreement was obtained. Flow structures in the pump-mixer were analyzed and two recirculation loops were observed. Holdup profiles reveal that the dispersed phase is unevenly distributed in space, which is more obvious at lower rotating speeds. Simulation results show that breakup regions are mainly located near the impeller where high energy dissipation rates exist, while coalescence regions were observed in the whole mixer. Distributions of the drop mean diameter were displayed. It indicated that the drop size is uniformly distributed in space at higher rotating speeds.

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CFD-PBM simulation of droplets size distribution in rotor-stator mixing devices

Cited by 46 publications

References 19 publications

Modeling of double emulsions using population balance equations

Modeling of double emulsions using population balance equations

Mechanisms and conditions that affect phase inversion processes: A review

CFD–PBM Simulation of Liquid–Liquid Dispersions in a Pump-Mixer

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