Numerical simulation and experimental study of emulsification in a narrow-gap homogenizer

Steiner, Helfried; Teppner, Renate; Brenn, Günter; Vankova, Nina; Tcholakova, Slavka; Denkov, Nikolai D.

doi:10.1016/j.ces.2006.04.016

Cited by 40 publications

(27 citation statements)

References 19 publications

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“…The averaged value over the whole gap is ε avg = 3.599 × 10 5 m 2 s −3 . These numbers are comparable with those obtained by Steiner et al [4] for the turbulent flow in the axially-symmetric emulsifier. The question arises, which value of ε is responsible for the final size Fig.…”

Section: Numerical Simulationsupporting

confidence: 80%

“…The flat emulsifier was constructed to ease optical access, hence to permit application of optical methods for measuring flow velocity fields (PIV method) and to visualize break-up of emulsion droplets. It is a two dimensional substitute of the central cross-section of the axially-symmetric emulsifier thoroughly investigated in the separate study [1,4]. The emulsifier consists of a small channel formed between two glass plates and a triangular processing element creating the rapid flow contraction (Fig.…”

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

“…The same emulsion was used in the parallel experimental campaign performed at the University of Sophia. In their experiment [1,4] the drop size distribution was measured for the emulsion created after over 100 consecutive passes through the emulsifier. A small samples of emulsion were extracted from the collecting vessel and investigated under the microscope equipped with the CCD camera and VCR recorder.…”

Section: Visualization Of Droplets Break-upmentioning

confidence: 99%

“…The main aim of the present work is to determine experimentally details of the flow characteristics in a plane model of the emulsifier, which preserves all hydrodynamic characteristics of the axial-type device [4]. An optical access through transparent walls permitted full field measurements necessary to resolve details of spatial and temporal flow field fluctuations in the emulsifier.…”

Section: Introductionmentioning

confidence: 99%

“…In the tube it creates an axially-symmetric emulsifier, device thoroughly investigated experimentally by Tscholakova et al [1]. The numerical simulation of the flow through the axially-symmetric emulsifier [1,4] was used to analyze effects of the turbulent energy dissipation on the emulsification process. It was correlated with a droplet size measurements.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of turbulence in a micro-channel emulsifier

Błoński

Korczyk

Kowalewski

2007

International Journal of Thermal Sciences

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Turbulent flow of water in an 1 mm long and 0.4 mm high gap of an emulsifier is investigated experimentally using micro-PIV technique and compared with numerical predictions. The purpose of the investigations is to develop a procedure for well-controlled generation of mono-disperse suspension of micro-droplets. The micro-flow measurements are based on epi-fluorescence illumination and high-speed imaging. The experimental data are compared with the numerical results obtained using direct simulation and turbulent flow model. From the turbulent modelling (k−ε) it was found that, the maximum of turbulent energy dissipation rate takes place mainly in the micro-channel gap. However, measured and directly simulated (DNS) velocity fields indicate that flow turbulization is delayed and develops shortly behind the gap. Experimental and numerical results are used to predict droplet dimension of two different oil emulsions. Very low amount of oil-phase fraction in investigated emulsions justifies us to use flow characteristics evaluated for pure water to predict mean diameter of oil droplets. These predictions are validated using experimental data on statistics of droplets size.

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Section: Numerical Simulationsupporting

confidence: 80%

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

Section: Visualization Of Droplets Break-upmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analysis of turbulence in a micro-channel emulsifier

Błoński

Korczyk

Kowalewski

2007

International Journal of Thermal Sciences

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Dual mechanism model for fluid particle breakup in the entire turbulent spectrum

Karimi

Andersson

2019

AIChE Journal

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This work provides an in-depth understanding of different breakup mechanisms for fluid particles in turbulent flows. All the disruptive and cohesive stresses are considered for the entire turbulent energy spectrum and their contributions to the breakup are evaluated. A new modeling framework is presented that bridges across turbulent subranges. The model entails different mechanisms for breakup by abandoning the classical limitation of inertial models. The predictions are validated with experiments encompassing both breakup regimes for droplets stabilized by internal viscosity and interfacial tension down to the micrometer length scale, which covers both the inertial and dissipation subranges. The model performance ensures the reliability of the framework, which involves different mechanisms. It retains the breakup rate for inertial models, improves the predictions for the transition region from inertia to dissipation, and bridges seamlessly to Kolmogorov-sized droplets. K E Y W O R D S mathematical modeling, multiphase flow, process, simulation, turbulence 1 | INTRODUCTION The size distribution of fluid particles within a continuous medium is of vital importance for different industrial applications. In multiphase processes, knowledge of size distribution determines the rate of momentum, heat and mass transport. The mathematical framework commonly used to tackle this problem is population balance modeling, which requires closure terms for the breakup and coalescence of the dispersed fluid particles. 1,2 The present work concentrates on the breakup mechanisms of fluid particles in turbulent flows.The pioneering models for breakup were formulated by Rayleigh in the nineteenth century for jet flows, and considered dynamic stresses and surface tension. 3 Taylor, 4,5 on the other hand, has shown the relevance of viscous stresses for droplet distortions when the droplets are very small or when the continuous phase is highly viscous. Balancing the deforming and stabilizing stresses, Hinze has proposed a formulation for the maximum stable droplet diameter (d max ) for dispersion in turbulent flows. 6 The above advancements have paved the way for further developments in the field. Typically, the ratio between counteracting stresses acting on fluid particles represents a dimensionless number that indicates the probable breakup mechanism. For instance, when inertia is the principal cause of breakup, a critical Weber number is quantified, and the break up takes place above this number; examples can be found in Reference 7-9 . The other scenario is the definition of a critical Capillary number (i.e., the ratio of viscous stress over surface stresses) for viscous laminar flows. [10][11][12] Although the dimensionless numbers are a relevant means for interpreting the breakup process, relying on dimensionless numbers to explain the complicated physical phenomenon that occurs during the breakup in turbulent multiphase systems is too simplistic. 13,14 Thus, later breakup models are inclined toward the dynamics of bubble or drople...

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High‐Pressure Homogenization: Simplified Drop Deformation Estimate during Transition through Orifices

Walzel

2017

Chem Eng & Technol

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The breakup process of primary drops during transition through slots or small openings has been examined frequently in the past. Recent experiments show strong influence of the dispersed-phase viscosity on the deformation of drops at the inlet of orifices that cannot be explained by the equilibrium approach based on capillary numbers or viscosity ratios only. It is necessary to account for the strongly transient character of the process. A quantitative treatment of this behavior based on relationships from the literature and executed with feasible numerical effort is presented. It is shown that the course of the extension rate of the flow and all properties of the system have a major influence on the drop deformation in front of the orifice. The threadlike deformed drops are precursors for the subsequent breakup process downstream.

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Numerical simulation and experimental study of emulsification in a narrow-gap homogenizer

Cited by 40 publications

References 19 publications

Analysis of turbulence in a micro-channel emulsifier

Analysis of turbulence in a micro-channel emulsifier

Dual mechanism model for fluid particle breakup in the entire turbulent spectrum

High‐Pressure Homogenization: Simplified Drop Deformation Estimate during Transition through Orifices

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