Alternative mechanisms of drop breakup in stirred vessels

Kumar, Sanjeev; Ganvir, Vivek; Satyanand, C.; Kumar, R.; Gandhi, K. S.

doi:10.1016/s0009-2509(98)00139-0

Cited by 41 publications

(36 citation statements)

References 15 publications

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“…These models have been extended to account for effect on drop size of dispersed phase rheologies (Lagisetty et al, 1986;Koshy et al, 1988b, Gandhi andKumar 1990), presence of surfactants (Koshy et al, 1988a) and circulation patterns (Kumar et al, 1992). Some models accounting for breakage mechanisms different from that due to turbulent pressure fluctuations have also been proposed (Kumar et al, 1991;Wichterle, 1995;Kumar et al, 1998). A few studies focusing on the fine details like the effect of intermittency of turbulence on representative drop diameter have also been presented (Baldyga and Bourne, 1993).…”

Section: Nishikawa Et Al (1987a)mentioning

confidence: 99%

Representative drop sizes and drop size distributions in A/O dispersions in continuous flow stirred tank

et al. 2008

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Section: Nishikawa Et Al (1987a)mentioning

confidence: 99%

Representative drop sizes and drop size distributions in A/O dispersions in continuous flow stirred tank

et al. 2008

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“…Most of the work published in the literature (except [9]), is for a low-viscosity dispersed phase and surfactant-free systems. Koshy et al [10] and Kumar et al [11] investigated the effect of surfactants on drop breakage in turbulent liquid dispersions of low viscosity. Few studies dealt with high-dispersed phase concentration but only [6,12] obtained drop sizes in unstable dispersions; in all other cases surfactant-stabilized emulsions were used.…”

Section: Introductionmentioning

confidence: 99%

Drop Size Distribution in a Standard Twin‐Impeller Batch Mixer at High Dispersed‐Phase Volume Fraction

El‐Hamouz

2009

Chem Eng & Technol

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The preparation of concentrated aqueous silicone oil emulsions has been investigated with particular attention to the effect of the dispersed‐phase volume fraction ϕ from 0.01 to 0.5 for a wide range of oil viscosities (50 to 1000 cSt). Oil was added on the top surface of a 6‐L vessel. Drop size distribution and Sauter mean diameter, d32, measurements were carried out over 24 h mixing time. Emulsification was found to be relatively sensitive to the oil phase viscosity, μd, for the same ϕ yielding a narrower drop size distribution for low oil viscosity (50 cSt) and a wider drop size distribution for the highly viscous oil (1000 cSt). For the same ϕ, increasing μd resulted in increasing d32. The equilibrium d32 was found to be well correlated to the viscosity number by $ {d_{32} \over D} = 0.026\, \ast \;{V_{\rm i}^{0.204}} $ for ϕ = 0.5. For the same oil viscosity, d32 was found to increase with increasing ϕ. A multiregression of d32 with both ϕ and Vi for various silicone oil viscosity grades was successfully correlated by $ d_{32} = 9.6\, \phi^{0.069} V_{\rm i}^{0.216} $ with a regression coefficient (R2) of 0.975. This shows a very weak dependence of the equilibrium d32 on ϕ.

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“…Kumar et al (1998) carried out experiments in which ratio was varied in range encompassing = 3 and found that the drop size changes smoothly with a change in in this range. This suggests that the drops could be breaking in extensional flow somewhere in the vessel as extensional flow can break drops of all viscosity ratios.…”

Section: Introductionmentioning

confidence: 99%

“…The data of Boye et al (1996), who varied impeller diameter could not be predicted very well as the d max for breakup in accelerating flow around the blade edge is predicted to be independent of impeller diameter. Kumar et al (1998) attributed this failure to the very approximate nature of the model used to analyse flow field around the blade. The effect of various other variables such as interfacial tension, viscosities of the two phases has yet not been studied and it is not clear of the model of Kumar et al (1998) fails only in predicting the dependence of d max on impeller diameter or other variables as well.…”

Section: Introductionmentioning

confidence: 99%

“…Kumar et al (1998) attributed this failure to the very approximate nature of the model used to analyse flow field around the blade. The effect of various other variables such as interfacial tension, viscosities of the two phases has yet not been studied and it is not clear of the model of Kumar et al (1998) fails only in predicting the dependence of d max on impeller diameter or other variables as well.…”

Section: Introductionmentioning

confidence: 99%

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Breakup of drops around the edges of Rushton turbine

Patil

Kumar

2010

Can J Chem Eng

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A detailed experimental and simulation study has been carried out in the present work to understand drop breakup in regions around the edge of the Rushton turbine in agitated vessels. The effect of impeller speed, impeller size, interfacial tension, and the viscosities of the two phases is studied on drop breakup through their effect on d max , the size of the largest drop in the system, and the whole size distribution. The measurements were carried out using Galai particle size analyser and optical microscope. Experimental analysis shows that the d max , maximum stable drop diameter varies with impeller tip velocity to the power −1. The variation of d max with interfacial tension is studied using different surfactants. The effect of viscosity ratio, achieved by changing the dispersed phase viscosity, on d max is captured. For the same d max values obtained from two different dispersed phases show that the wider drop size distribution is observed for higher dispersed phase viscosity.Uneétude expérimentale et de simulation détaillée aété réalisée dans ce travail dans le but de comprendre la rupture de gouttes dans les zones près de l'extrémité de la turbine Rushton dans des cuves agitées. L'effet de la vitesse de l'impulseur, de la taille de l'impulseur, de la tension interfaciale et des viscosités des deux phases estétudié sur la rupture de gouttes par leur effet sur le diamètre de goutte stable maximal, la taille de la plus grosse goutte du système et la distribution pour toute la taille. Les mesures ontété effectuéesà l'aide d'un analyseur granulométrique Galai et d'un microscope optique. Une analyse expérimentale démontre que le diamètre de goutte stable maximal varie avec une vélocité du bout de l'impulseurà la puissance -1. La variation du diamètre de goutte stable maximal avec la tension interfaciale estétudiéeà l'aide de différents surfactifs. L'effet de viscosité relative, atteint en changeant la viscosité de phase dispersée, sur le diamètre de goutte stable maximal est capté. Les mêmes valeurs de diamètre de goutte stable maximal obtenues de deux phases dispersées différentes indiquent que la distribution des plus grosses gouttes est observée pour la viscosité de phase dispersée supérieure.

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Alternative mechanisms of drop breakup in stirred vessels

Cited by 41 publications

References 15 publications

Representative drop sizes and drop size distributions in A/O dispersions in continuous flow stirred tank

Representative drop sizes and drop size distributions in A/O dispersions in continuous flow stirred tank

Drop Size Distribution in a Standard Twin‐Impeller Batch Mixer at High Dispersed‐Phase Volume Fraction

Breakup of drops around the edges of Rushton turbine

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