Coalescence of liquid droplets in two‐component–two‐phase systems: Part I. Effect of physical properties on the rate of coalescence

Jeffreys, G. V.; Hawksley, J. L.

doi:10.1002/aic.690110309

Cited by 81 publications

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“…For higher approach velocities the rupture threshold may not be reached and the strain energy can reverse the bubble motion (rebound) and the film begins to thicken. At low approach velocities the rate of increase in contact area is slow enough to allow drainage and rupture [36]. In general, in the presence of ultrasound, an increase in frequency (at high frequencies) and the acoustic pressure increases the secondary Bjerknes force and the approach velocity [37].…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…This could imply that highly viscous fluids inhibit bubble surface motion and film drainage between the bubbles in contact, which is known to reduce coalescence [213]. However, the time for coalescence to occur becomes relevant in an ultrasound environment due to time dependant forces on the bubbles [36]. Numerical analysis of a two bubble system suggests that increasing the viscosity of the liquid, in this case sulfuric acid, would decrease the secondary Bjerknes force, approach velocity and therefore increase contact time [245].…”

Section: Surface Tension and Viscositymentioning

confidence: 99%

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A parametric review of sonochemistry: Control and augmentation of sonochemical activity in aqueous solutions

Wood

Lee

Bussemaker

2017

Ultrasonics Sonochemistry

260

137

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Please cite this article as: R.J. Wood, J. Lee, M.J. Bussemaker, A parametric review of sonochemistry: control and augmentation of sonochemical activity in aqueous solutions, Ultrasonics Sonochemistry (2017), doi: http:// dx.doi.org/10. 1016/j.ultsonch.2017.03.030 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.A parametric review of sonochemistry: control and augmentation of sonochemical activity in aqueous solutions

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Section: Theoretical Backgroundmentioning

confidence: 99%

Section: Surface Tension and Viscositymentioning

confidence: 99%

A parametric review of sonochemistry: Control and augmentation of sonochemical activity in aqueous solutions

Wood

Lee

Bussemaker

2017

Ultrasonics Sonochemistry

260

137

View full text Add to dashboard Cite

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“…As a drop or bubble approaches an interface, it develops a dimple: the film is thicker at its center than at its rim (Derjaguin and Kussakov, 1939;Allan et al, 1961;Platikanov, 1964;Hartland, 1967Hartland, , 1969Hartland and Wood, 1973;Hodgson and Woods, 1969;Burrill and Woods, 1973). Models concerned with the shape of the film as a drop or bubble approaches a fluid-fluid interface have been discussed by Chappelear (1961), by Charles and Mason (1960), by Jeffreys and Hawksley (1965), and by Lang and Wilke (1971). Our concern here will be the simpler case of a drop or bubble approaching a solid surface.…”

Section: Introductionmentioning

confidence: 99%

Thinning of a liquid film as a small drop or bubble approaches a solid plane

Lin

Slattery

1982

AIChE Journal

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When a small drop or bubble approaches a solid surface, a thin liquid film forms between them, drains, until an instability forms and coalescence occurs. A hydrodynamic theory is developed for the first portion of this coalescence process: the drainage of the thin liquid film while it is still sufficiently thick that the effects of London‐van der Waals forces and electrostatic forces can be ignored. This theory describes the time rate of change of the film profile, given only the drop radius and the required physical properties. Predictions are compared with profiles measured by Platikanov (1964) for gas bubbles. It is concluded that, even with only a trace of surfactant present, the liquid‐gas interface may be nearly immobile (tangential components of velocity are zero) and the surface viscosities will have little effect upon the drainage rate.

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“…Quantitative studies for multiple-drop systems have been confined to agitated vessels (8,10,13, 17,18). The techniques used usually involved some type of drop tracer study requiring an indirect method of observation and contamination of the liquid system with a tracer.…”

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confidence: 99%

The coalescence of drops in liquid‐liquid fluidized beds

Maraschino

Treybal

1971

AIChE Journal

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T h e coalescence rates of equisized drops of organic liquids fluidized by water under conditions of mutual saturation were studied. A drop-size separation technique permitted the direct count of the coalesced drops. Six organic liquids (benzene, cyclohexane, n-butylacetate, methyl isobutyl ketone, diisobutyl carbinol, and tetrahydrobenzaldehyde) were used, and the coalescence was in a l l cases total, that is, without formation of small satellite drops.A new hydrodynamic model i s presented to calculate the parameters governing the drainage of liquid between two deformable drops in head-on collision. A parameter from this model permits correlation of the coalescence rates with only two arbitrary constants, provided the ratio of dispersed to continuous liquid viscosities lies between 0.5 and 2. High viscosity ratios or the presence of trace quantities of surfactant greatly depress the coalescence rate, while continued reuse of the dispersed liquid leads to a statistically significant reduction. The presence of a fog of very small droplets increases the coalescence rate.In recent years evidence has been accumulating that the coalescence of drops in a liquid-liquid dispersion has a strong influence on the performance of liquid-extraction devices. For example, coalescence has been shown to be detrimental to the performance of spray towers (1 ). On the other hand, coalescence and redispersion of the drops in an agitated vessel are suspected of being responsible for enhanced mass transfer rates (20).extensive work on the time of coalescence of single drops at a flat interface, recently reviewed ( 4 , 14), has resulted in only one proposed correlation (13), which i s totally empirical and involves many arbitrary constants. Quantitative studies for multiple-drop systems have been confined to agitated vessels (8,10,13, 17,18). The techniques used usually involved some type of drop tracer study requiring an indirect method of observation and contamination of the liquid system with a tracer. This makes interpretation of the results difficult, since the coalescence phenomenon i s extremely sensitive to contaminants. The only correlation relating coalescence rate to all physical properties is that of Hillestad and Rushton ( l o ) , which uses many arbitrary constants. Only qualitative information i s available for spray towers (7, 15).In the present study, the coalescence rates for a swarm of uniformly sized drops maintained in a fluidized bed were studied. A drop-size segregation technique was used, so that newly formed coalesced drops were quickly removed from the bed, at a rate determined by direct counting. It i s believed that the conditions of measurement exerted a minimal influence on the phenomenon.The coalescence phenomenon i s poorly understood. The APPARATUS AND PROCEDUREThe vertical glass tube of Figure 1 consists of two tubes of uniform but different diameters joined by a tapered section. The continuous liquid enters from the top and flows downward. The dispersed phase, consisting of uniform, small drops, enters...

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Coalescence of liquid droplets in two‐component–two‐phase systems: Part I. Effect of physical properties on the rate of coalescence

Cited by 81 publications

References 0 publications

A parametric review of sonochemistry: Control and augmentation of sonochemical activity in aqueous solutions

A parametric review of sonochemistry: Control and augmentation of sonochemical activity in aqueous solutions

Thinning of a liquid film as a small drop or bubble approaches a solid plane

The coalescence of drops in liquid‐liquid fluidized beds

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