The effect of electric field on mass transfer from drops dispersed in a viscous liquid

He, W.; Baird, M. H. I.; Chang, Jen‐Shih

doi:10.1002/cjce.5450710305

Cited by 23 publications

(8 citation statements)

References 34 publications

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“…Previous studies in the literature reported observations that suggested stimulation of mass transfer at liquid interfaces under an electric field. − However, these studies either lacked a thorough analysis of the observations or were inconclusive. Some earlier studies speculated that an increase in ion density at a fluid interface under an electric field is responsible for the altered surface tension. − A liquid drop surrounded by another immiscible liquid and exposed to an electric field assumes a new shape.…”

Section: Introductionmentioning

confidence: 99%

Experimental Evidence of Enhanced Adsorption Dynamics at Liquid–Liquid Interfaces under an Electric Field

2020

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In this work we investigate adsorption of surface active compounds at water-oil interface subjected to an electric eld. A uid system comprising a pendent water drop surrounded by an asphaltene-rich organic phase is exposed to a DC uniform electric eld.Two sub-fractions of asphaltenes having contrasting anities to water-oil interface are used as surface active compounds. The microscopic changes in the drop shape, as a result of asphaltene adsorption, are captured and the drop proles are analyzed by using our in-house code for axisymmetric drop shape analysis (ADSA) under electric eld.The estimates of dynamic interfacial tension under dierent strengths of the eld (E 0 ) and concentrations of the asphaltene sub-fractions (C) are used to calculate adsorption dynamics and surface excess. The experimental observations and careful analysis of the data suggest that the externally applied electric eld signicantly stimulates the mass transfer rate at a liquid-liquid interface. The enhancement in mass transport at 1 water-oil interface can be attributed to the axisymmetric electrohydrodynamic uid ows generated on either sides of the interface. The boost in mass transport is evident from the growing decay in equilibrium interfacial tension (γ eq ) and increased surface excess (Γ eq ) upon increasing strength of the applied electric eld. The mass transfer intensication does not increase monotonously with the electric eld strength above an optimum E 0 , which is in agreement with previous theoretical studies in the literature.However, these rst explicit experimental measurements of adsorption at an interface under electric eld suggest that the optimum E 0 is determined by characteristics of the surface active molecules.

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Section: Introductionmentioning

confidence: 99%

Experimental Evidence of Enhanced Adsorption Dynamics at Liquid–Liquid Interfaces under an Electric Field

2020

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“…More recent practical interest is associated with the processes in which enhancement of the rate of mass or heat transfer between drops and their surrounding fluid is desired (cf. Thornton 1968;Harker & Ahmadzadeh 1974;Bailes 1981;Baird 1983;Scott 1989;Weatherley 1992;Ptasinski & Kerkhof 1992;He, Baird & Chang 1993). Taking in account circulatory flows generated by an applied electric field, Morrison (1977) and Griffiths & Morrison (1979) evaluated transfer rate enhancement and found significant electroconvective effects for stationary drops.…”

Section: Introductionmentioning

confidence: 99%

A computational analysis of electrohydrodynamics of a leaky dielectric drop in an electric field

1996

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Axisymmetric steady flows driven by an electric field about a deformable fluid drop suspended in an immiscible fluid are studied within the framework of the leaky dielectric model. Deformations of the drop and the flow fields are determined by solving the nonlinear free-boundary problem composed of the Navier-Stokes system governing the flow field and Laplace's system governing the electric field. The solutions are obtained by using the Galerkin finite-element method with an elliptic mesh generation scheme. Under conditions of creeping flow and vanishingly small drop deformations, the results of finite-element computations recover the asymptotic results. When drop deformations become noticeable, the asymptotic results are often found to underestimate both the flow intensity and drop deformation. By tracking solution branches in parameter space with an arc-length continuation method, curves in parameter space of the drop deformation parameter D versus the square of the dimensionless field strength E usually exhibit a turning point when E reaches a critical value Ec. Along such a family of drop shapes, steady solutions do not exist for E > Ec. The nonlinear relationship revealed computationally between D and E2 appears to be capable of providing insight into discrepancies reported in the literature between experiments and predictions based on the asymptotic theory. In some special cases with fluid conductivities closely matched, however, drop deformations are found to grow with E2 indefinitely and no critical value Ec is encountered by the corresponding solution branches. For most cases with realistic values of physical properties, the overall electrohydrodynamic behaviour is relatively insensitive to effects of finite-Reynolds-number flow. However, under extreme conditions when fluids of very low viscosities are involved, computational results illustrate a remarkable shape turnaround phenomenon: a drop with oblate deformation at low field strength can evolve into a prolate-like drop shape as the field strength is increased.

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“…13 Furthermore, the drops formed at an electrically connected nozzle or orifice will acquire a certain amount of induced charge, which depends on the imposed electric field strength/applied voltage. 59 Studies have also shown that the motion of charge carriers, such as ions, in a fluid can cause electrohydrodynamic ͑EHD͒ flow or Coulomb-driven convection 14 flow during ES formation. Information about electric charge ͑including free charge and induced charge͒ on the electroformed droplets and the electric-field intensity inside the experimental cell are also very important to study the EHD effects on the mechanism of drop formation and motion during ES.…”

Section: Relation Between Current and Voltagementioning

confidence: 99%

Parameters affecting electrospray performance of hot-embossed open-channel polymer microfluidic chips

Malahat

Iovenitti

Sbarski

2010

J. Micro/Nanolith. MEMS MOEMS

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We investigate the effect of chip tip-to-counter electrode spacing ͑gap͒, channel-size aspect ratio, onset voltage on electrospray ionization ͑ESI͒ performance of embossed polymer microfluidic chips. Planar polymer substrates were hot embossed using an electroformed tool and a laser machined tool. The embossed microchips were tested for successful ESI demonstration with minimum sample consumption and high throughput. Factors influencing the stability of electrospray were analyzed by a series of experiments. Theoretically and experimentally, it was observed that the distance of the microchannel tip to the counter electrode directly relates to the onset voltage applied. Furthermore, the overall pattern observed is the decrease in Taylor cone size with a decrease in channel dimensions. The total ion current was analyzed as a function of time and onset voltage at various gaps. Five electrospray modes, namely, drop mode, pulse mode, Taylor-cone jet mode, multijet mode, and oscillating jet mode recorded at the open channel tips were identified and the electrospray cycle investigated. These results are in good accordance with theory, and comparisons are drawn with the findings of other researchers.

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The effect of electric field on mass transfer from drops dispersed in a viscous liquid

Cited by 23 publications

References 34 publications

Experimental Evidence of Enhanced Adsorption Dynamics at Liquid–Liquid Interfaces under an Electric Field

Experimental Evidence of Enhanced Adsorption Dynamics at Liquid–Liquid Interfaces under an Electric Field

A computational analysis of electrohydrodynamics of a leaky dielectric drop in an electric field

Parameters affecting electrospray performance of hot-embossed open-channel polymer microfluidic chips

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