Effect of surfactants on the deformation and break-up of an aqueous drop in oils under high electric field strengths

Zhang, L.; He, Limin; Ghadiri, Mojtaba; Hassanpour, Ali

doi:10.1016/j.petrol.2014.11.014

Cited by 30 publications

(18 citation statements)

References 26 publications

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“…The effect of surfactants on the electro-deformation of neutrally buoyant drops was investigated by experimental techniques (Ha & Yang, 1998) and the corresponding theoretical models were also presented (Ha & Yang, 1995;Teigen & Munkejord, 2010;Nganguia et al, 2013). Zhang et al (2015) studied the role of nonionic surfactant on the deformation and breakup characteristic of a water droplet in a surrounding oil medium. Later, Ervik et al (2018) showed how the insoluble surface active agents can affect the oscillating nature of droplets under AC electric field.…”

Section: Introductionmentioning

confidence: 99%

Sedimentation of a surfactant-laden drop under the influence of an electric field

et al. 2018

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The sedimentation of a surfactant-laden deformable viscous drop acted upon by an electric field is considered theoretically. The convection of surfactants in conjunction with the the combined effect electrohydrodynamic flow and sedimentation leads to a locally varying surface tension, which subsequently alters the drop dynamics via the interplay of Marangoni, Maxwell and hydrodynamic stresses. Assuming small capillary number and small electric Reynolds number, we employ a regular perturbation technique to solve the coupled system of governing equations. It is shown that when a leaky dielectric drop is sedimenting in another leaky dielectric fluid, Marangoni stress can oppose the electrohydrodynamic motion severely, thereby causing corresponding changes in internal flow pattern. Such effects further result in retardation of drop settling velocity, which would have otherwise increased due to the influence of charge convection. For highly mobile surfactants (high Péclet number limit), the drop surface becomes immobilized and the charge convection effect gets completely eliminated. For non-spherical drop shapes, the effect of Marangoni stress is overcome by the 'tip stretching' effect on the flow field. As a result, the drop deformation gets intensified with increment in sensitivity of surface tension to the local surfactant concentration. Consequently, for oblate type of deformation the elevated drag force causes further reduction in velocity. Owing to similar reasons, prolate drops experience lesser drag and settles faster than the surfactant-free case. In addition to this, with increased sensitivity of interfacial tension on the surfactant concentration, the asymmetric deformation about the equator gets suppressed. These findings may turn out to be of fundamental significance towards designing electrohydrodynamically actuated droplet based microfluidic systems that are intrinsically tunable by varying the surfactant concentration. *

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Section: Introductionmentioning

confidence: 99%

Sedimentation of a surfactant-laden drop under the influence of an electric field

et al. 2018

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“…However, when surfactants are added to this picture, the literature is not so extensive. Previous authors (Ha and Yang, 1998;Zhang et al, 2015) have investigated the influence of surfactants on the electrohydrodynamic stretching experimentally, but they have been limited to considerations of the static (equilibrium) deformation, as well as drop sizes above 1 mm in diameter, and a limited number of observations. Computational studies in the literature, namely previous work by , and the paper by Nganguia et al (2013) which finds good agreement with , have also been focused on the static deformation.…”

Section: Introductionmentioning

confidence: 99%

Influence of surfactants on the electrohydrodynamic stretching of water drops in oil

Ervik

Penne

Hellesø

et al. 2018

International Journal of Multiphase Flow

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In this paper we present experimental and numerical studies of the electrohydrodynamic stretching of a sub-millimetre-sized salt water drop, immersed in oil with added non-ionic surfactant, and subjected to a suddenly applied electric field of magnitude approaching 1 kV/mm. By varying the drop size, electric field strength and surfactant concentration we cover the whole range of electric capillary numbers (Ca E ) from 0 up to the limit of drop disintegration. The results are compared with the analytical result by G.I. Taylor (Proc. R. Soc. A 280, 383 (1964)) which predicts the asymptotic deformation as a function of Ca E . We find that the addition of surfactant damps the transient oscillations and that the drops may be stretched slightly beyond the stability limit found by Taylor. We proceed to study the damping of the oscillations, and show that increasing the surfactant concentration has a dual effect of first increasing the damping at low concentrations, and then increasing the asymptotic deformation at higher concentrations. We explain this by comparing the Marangoni forces and the interfacial tension as the drops deform. Finally, we have observed in the experiments a significant hysteresis effect when drops in oil with large concentration of surfactant are subjected to repeated deformations with increasing electric field strengths. This effect is not attributable to the flow nor the interfacial surfactant transport.

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“…The findings revealed that an increase in the frequency of the PEF suppressed the formation of secondary droplets in the low-frequency electric domain. Zhang et al [139] examined the influence of a demulsifier on the distortion and breakup of hydrous drops in an immiscible dielectric oil under the effect of an electric source. The experimental runs were performed in a single drop microscopic cell under an external electric field.…”

Section: Electrical Demulsificationmentioning

confidence: 99%

An Overview of Recent Advances in State-of-the-Art Techniques in the Demulsification of Crude Oil Emulsions

et al. 2019

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The processing of crude oil often requires the extraction of a large amount of water. Frequently, crude oil is mixed with water to form water-in-crude oil emulsions as the result of factors such as high shear at the production wellhead and surface-active substances that are naturally present in crude oil. These emulsions are undesirable and require demulsification to remove the dispersed water and associated inorganic salts in order to meet production and transportation specifications. Additionally, the demulsification of these crude oil emulsions mitigates corrosion and catalyst poisoning and invariably maximizes the overall profitability of crude oil production. Recently, there has been growing research interest in developing workable solutions to the difficulties associated with transporting and refining crude oil emulsions and the restrictions on produced water discharge. Therefore, this paper reviews the recent research efforts on state-of-the-art demulsification techniques. First, an overview of crude oil emulsion types, formation, and stability is presented. Then, the parameters and mechanisms of emulsification formation and different demulsification techniques are extensively examined. It is worth noting that the efficiency of each of these techniques is dependent on the operating parameters and their interplay. Moreover, a more effective demulsification process could be attained by leveraging synergistic effects by combining one or more of these techniques. Finally, this literature review then culminates with propositions for future research. Therefore, the findings of this study can help for a better understanding of the formation and mechanisms of the various demulsification methods of crude oil to work on the development of green demulsifiers by different sources.

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Effect of surfactants on the deformation and break-up of an aqueous drop in oils under high electric field strengths

Cited by 30 publications

References 26 publications

Sedimentation of a surfactant-laden drop under the influence of an electric field

Sedimentation of a surfactant-laden drop under the influence of an electric field

Influence of surfactants on the electrohydrodynamic stretching of water drops in oil

An Overview of Recent Advances in State-of-the-Art Techniques in the Demulsification of Crude Oil Emulsions

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