scholarly journals Critical electric field strength for partial coalescence of droplets on oil–water interface under DC electric field

2018 ◽  
Vol 136 ◽  
pp. 83-93 ◽  
Author(s):  
Donghai Yang ◽  
Mojtaba Ghadiri ◽  
Yongxiang Sun ◽  
Limin He ◽  
Xiaoming Luo ◽  
...  
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Water Interface ◽  
Partial Coalescence ◽  
Dc Electric Field ◽  
Oil Water

Bubble Formation in a DC Electric Field

2008 ◽  
Author(s):  
Feng Chen ◽  
Yaozu Song ◽  
Yao Peng
Keyword(s):  
Aspect Ratio ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Bubble Growth ◽  
Growth Process ◽  
Major Axis ◽  
Minor Axis ◽  
Electric Stress ◽  
Dc Electric Field

The effect of a DC electric field on the formation and the characteristics of a nitrogen bubble injected from an orifice were studied experimentally and theoretically. This study was the first to divide the bubble growth process into four stages (waiting, expansion, deformation and detachment) according to the variation of the bubble shape in order to analyze the bubble behavior in the electric field. During the waiting stage, the waiting interval decreases significantly as the electric field strength rises. In the expansion stage, the minor axis reaches a maximum that decreases with increasing the electric field strength. Within the deformation stage, the major axis achieves its maximum and so does the aspect ratio. As the electric field strength rises, both the maximums of the major axis and the aspect ratio increase. At the detachment stage, as the electric field strength is intensified, the major axis lengthens, the minor axis shortens and the aspect ratio lengthens. From the waiting stage to the detachment stage, the effect of the electric field on the major axis of the bubble is marginal, while with increasing the electric field strength, the minor axis decreases distinctly and thus the aspect ratio increases. To employ the four-stage model, the bubble growth process was analyzed in detail under the electric field. The electric stress exerted on the bubble surface was calculated. The results show that the electric stress compresses the bubble equator and elongates the poles of the bubble, causing the bubble to elongate along the electric field direction.

Visualization of a Single Boiling Bubble in a DC Electric Field

2011 ◽  
Author(s):  
Feng Chen ◽  
Dong Liu ◽  
Yaozu Song ◽  
Yao Peng
Keyword(s):  
Heat Transfer ◽  
Life Cycle ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Wall Temperature ◽  
Boiling Heat Transfer ◽  
Bubble Dynamics ◽  
Nucleate Boiling ◽  
Dc Electric Field

The application of electric field has been demonstrated as an effective way to enhance pool boiling heat transfer. In past studies, adiabatic experiments were often conducted to simulate the dynamics of nucleate bubbles in the presence of an electric field, where gas bubbles were injected from an orifice, to avoid complexities involved in the nucleate boiling experiments. While adiabatic studies yield useful information of the bubble dynamics, further studies about bubble dynamics during nucleate boiling heat transfer are still necessary for a full understanding of the effects of applied electric field on the liquid-vapor phase change heat transfer. In this paper, the dynamics of a single boiling bubble in a direct current (DC) electric field was studied experimentally employing R113 as the working fluid. The life cycle of the boiling bubble was visualized using high-speed photography and was compared with that of an injected nitrogen bubble. Under the same electric field, a more appreciable elongation along the field direction was observed for the boiling bubble. A modified relationship between the bubble deformation and the electrical Weber number was proposed for the boiling bubble. As the electric field strength increases, it was found that, although the growth time of the boiling bubble increases, the waiting period decreases. However, it was also found that, the change of the whole life cycle with electric field strength increasing is relevant to the wall temperature. In this work, the wall temperature measured in the vicinity of the nucleation site upon the bubble departure decreases when the electric field is applied.

scholarly journals Experimental Study on the Performance of a Novel Compact Electrostatic Coalescer with Helical Electrodes

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1733
Author(s):  
Yi Shi ◽  
Jiaqing Chen ◽  
Zehao Pan
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Water Content ◽  
Water Droplet ◽  
Separation Process ◽  
Water Droplets ◽  
Water Separation ◽  
Oil Water Separation ◽  
Oil Water

As most of the light and easy oil fields have been produced or are nearing their end-life, the emulsion stability is enhanced and water cut is increasing in produced fluid which have brought challenges to oil–water separation in onshore and offshore production trains. The conventional solution to these challenges includes a combination of higher chemical dosages, larger vessels and more separation stages, which often demands increased energy consumption, higher operating costs and larger space for the production facility. It is not always feasible to address the issues by conventional means, especially for the separation process on offshore platforms. Electrostatic coalescence is an effective method to achieve demulsification and accelerate the oil–water separation process. In this paper, a novel compact electrostatic coalescer with helical electrodes was developed and its performance on treatment of water-in-oil emulsions was investigated by experiments. Focused beam reflectance measurement (FBRM) was used to make real-time online measurements of water droplet sizes in the emulsion. The average water droplet diameters and number of droplets within a certain size range are set as indicators for evaluating the effect of coalescence. We investigated the effect of electric field strength, frequency, water content and fluid velocity on the performance of coalescence. The experimental results showed that increasing the electric field strength could obviously contribute to the growth of small water droplets and coalescence. The extreme value of electric field strength achieved in the high-frequency electric field was much higher than that in the power-frequency (50 Hz) electric field, which can better promote the growth of water droplets. The initial average diameters of water droplets increase with higher water content. The rate of increment in the electric field was also increased. Its performance was compared with that of the plate electrodes to further verify the advantages of enhancing electrostatic coalescence and demulsification with helical electrodes. The research results can provide guidance for the optimization and performance improvement of a compact electrocoalescer.

Coalescence, Partial Coalescence, and Noncoalescence of an Aqueous Drop at an Oil–Water Interface under an Electric Field

Langmuir ◽  
2020 ◽  
Vol 36 (21) ◽  
pp. 6051-6060 ◽  
Author(s):  
Vikky Anand ◽  
Vinay A. Juvekar ◽  
Rochish M. Thaokar
Keyword(s):  
Electric Field ◽  
Water Interface ◽  
Partial Coalescence ◽  
Oil Water

Visualization of a Single Boiling Bubble in a DC Electric Field

2012 ◽  
Author(s):  
Feng Chen ◽  
Dong Liu ◽  
Yaozu Song
Keyword(s):  
Heat Transfer ◽  
Life Cycle ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Wall Temperature ◽  
Boiling Heat Transfer ◽  
Bubble Dynamics ◽  
Nucleate Boiling ◽  
Dc Electric Field

The application of electric field has been demonstrated as an effective way to enhance pool boiling heat transfer. In past studies, adiabatic experiments were often conducted to simulate the dynamics of nucleate bubbles in the presence of an electric field, where gas bubbles were injected from an orifice, to avoid complexities involved in the nucleate boiling experiments. While adiabatic studies yield useful information of the bubble dynamics, further studies about bubble dynamics during nucleate boiling heat transfer are still necessary for a full understanding of the effects of applied electric field on the liquid-vapor phase change heat transfer. In this paper, the dynamics of a single boiling bubble in a direct current (DC) electric field was studied experimentally employing R113 as the working fluid. The life cycle of the boiling bubble was visualized using high-speed photography and was compared with that of an injected nitrogen bubble. Under the same electric field, a more appreciable elongation along the field direction was observed for the boiling bubble. A modified relationship between the bubble deformation and the electrical Weber number was proposed for the boiling bubble. As the electric field strength increases, it was found that, although the growth time of the boiling bubble increases, the waiting period decreases. However, it was also found that, the change of the whole life cycle with electric field strength increasing is relevant to the wall temperature. In this work, the wall temperature measured in the vicinity of the nucleation site upon the bubble departure decreases when the electric field is applied.

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