Drop breakup in dilute Newtonian emulsions in simple shear flow: New drop breakup mechanisms

Zhao, Xinyu

doi:10.1122/1.2714641

Cited by 38 publications

(19 citation statements)

References 34 publications

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“…When the viscous shear force overcomes the surface tension force, drops elongate and break to form large number of very small satellite drops (Zhao, 2007). Hence, the following bimodal daughter distribution function (Fig.…”

Section: Pbe Functionsmentioning

confidence: 99%

“…When the capillary number is just slightly larger than the critical value such that 1 r Ca=Ca cr r 2, a drop breaks into two nearly equally sized daughter drops by an end-pinching mechanism (Region A in Fig. 1(b)) (Janssen et al, 1994;Wieringa et al, 1996;Zhao, 2007). When Ca=Ca cr 4 41 and 0:1 o λo1, a drop breaks into many nearly equally sized daughter drops by a capillary mechanism (Region C in Fig.…”

Section: Drop Breakage and Coalescence In Colloid Millsmentioning

confidence: 99%

“…When Ca=Ca cr 4 41 and λ41, a drop breaks into many unequally sized daughter or satellite drops (Region B in Fig. 1(b), (c)) (Zhao, 2007;Cristini et al, 2003). Adding to the complexity, Ca cr is known to depend on the type of flow field in addition to the viscosity ratio.…”

Section: Drop Breakage and Coalescence In Colloid Millsmentioning

confidence: 99%

“…Additional passes of the emulsion through the colloid mill allow the drop size to be further reduced. While drop breakage in simple shear or Couette flow has been well studied (Cristini et al, 2003;Zhao, 2007;Renardy et al, 2002;Grace, 1982;Boonen et al, 2010), drop breakage mechanisms in colloid mills are not well understood. Common practice is to assume simple or extensional shear flow, in which drops break due to capillary instability when the ratio of the viscous stress to the interfacial tension force crosses a critical value (Wieringa et al, 1996;King and Keswani, 1994;Almeida-Rivera and Bongers, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Prediction of emulsion drop size distributions in colloid mills

Maindarkar

Dubbelboer

Meuldijk

et al. 2014

Chemical Engineering Science

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Developed a population balance equation model for emulsification in colloid mill. Derived the function for drop breakage frequency in simple shear flow. Proposed a new daughter drop distribution function for capillary drop breakage. Used a viscosity model to predict the emulsion viscosity at high shear rates. Demonstrated good agreement between measured and predicted drop size distributions. Colloid mills are the most common emulsification devices used in industry for products with high oil content. Drop breakage occurs when the emulsion is flowed through a small gap between rotor and stator under laminar shear conditions. In this paper, we have developed the first full population balance equation (PBE) model for colloid mills and used the model to better understand the relevant drop breakage mechanisms. The PBE model accounted for both drop breakage and coalescence and generated predictions of the drop size distribution after each pass of the emulsion through the colloid mill. Drops were assumed to break due to capillary instability with the distribution of drop sizes resulting from each breakage event studied in detail. A viscosity model was developed to predict the emulsion viscosity as function of the oil fraction and the high shear rates commonly used. Nonlinear optimization was used to estimate adjustable parameters in the breakage and coalescence functions to minimize the least-squares difference between predicted and measured drop size distributions for high oil-to-surfactant emulsions. We concluded that experimentally observed drop volume distributions could not be predicted with daughter drop distribution functions reported in the literature. Improved predictions were obtained using a new bimodal distribution function which captured drop breakage into multiple, nearly uniform daughter drops with a large number of small satellite drops. We also investigated model extensibility for changes in the oil fraction, emulsion flow rate and rotor speed.Published by Elsevier Ltd.

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Section: Pbe Functionsmentioning

confidence: 99%

Section: Drop Breakage and Coalescence In Colloid Millsmentioning

confidence: 99%

Section: Drop Breakage and Coalescence In Colloid Millsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Prediction of emulsion drop size distributions in colloid mills

Maindarkar

Dubbelboer

Meuldijk

et al. 2014

Chemical Engineering Science

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“…Their studies showed that when the viscosity ratio is greater than O(0.1), the critical capillary number decreases with increasing offset only for the smallest offset. Zhao [10] investigated the drop break up in dilute Newtonian emulsions in simple shear flow by using high-speed microscopy over a wide range of viscosity ratio, focusing on high capillary number. He showed the final drop size distribution intimately links to the drop break up mechanism, which depends on viscosity ratio and capillary number.…”

Section: Introductionmentioning

confidence: 99%

Geometry effects on the interaction of two equal-sized drops in simple shear flow at finite Reynolds numbers

Mortazavi¹,

Bayareh²

2009

Computational Methods in Multiphase Flow V

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The effect of geometry on the interaction of two equal-sized drops in shear flow is presented. The full Navier-Stokes equations are solved by a finite difference/front tracking method. The interaction of drops was studied at finite Reynolds numbers for viscosity ratio (λ) of one. The distance between drop centres along the velocity gradient direction (z) was measured as a function of time. The interaction of two drops contains approach, collision, and separation. Based on experimental data, we simulated different geometries by changing the offset and size of drops. It was found that ∆z increases after collision and reaches ∆z, during three stages of interaction, increases with the increasing initial offset. To investigate the drop shape evolution, we calculated the deformation and the orientation angle formed by the drop major axis and horizontal direction. The deformation of the drops is maximum when the drops are pressed against each other and minimum when they are drawn a part. Our results show that the time of approaching of drops at low initial offset is greater than the other ones, but the maximum deformation is the same for equal drop sizes. The deformation decreases with the decreasing size of drops. As the initial offset increases, the drops rotate more quickly and the available contact time for film drainage decreases. We found that the trajectories of drops in the approaching stage are different owing to the different initial offsets. However, after the drops come into contact, it can be seen that they follow the same trajectories, similar to experimental results.

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Macro, Micro and Nanostructured Morphologies of Multiphase Polymer Systems

Huang

2011

Handbook of Multiphase Polymer Systems

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Drop breakup in dilute Newtonian emulsions in simple shear flow: New drop breakup mechanisms

Cited by 38 publications

References 34 publications

Prediction of emulsion drop size distributions in colloid mills

Prediction of emulsion drop size distributions in colloid mills

Geometry effects on the interaction of two equal-sized drops in simple shear flow at finite Reynolds numbers

Macro, Micro and Nanostructured Morphologies of Multiphase Polymer Systems

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