Electric field effects on drop size and terminal velocity in liquid‐liquid systems

Vu, Ngo; Carleson, T.E.

doi:10.1002/aic.690321018

Cited by 20 publications

(7 citation statements)

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“…The charged drop falling in the direction of gravity will fall at a higher terminal velocity. These effects have been observed and reported in the literature (Vu and Carleson, 1986;Carleson and Berg, 1983;Harker and Amadzadeh, 1974). In some cases the increase in terminal velocity will result in shortened drop residence times and resulting lower absorption efficiencies (for gas absorbing in a falling charged drop; C.arleson and Berg, 1983).…”

Section: Introductionmentioning

confidence: 74%

“…Figure 1 depicts the cohmm used to study the effect of a D.C. field on forming and falling single drops. Previous work was performed with this column on the measurementof drop charge and velocity (Vu and Carleson, 1986). In the DOE supportedwork, drop mass transferrates were evaluated.…”

Section: Research Resultsmentioning

confidence: 99%

“…liquid-liquid systems), the extraction efficiencies will increase perhaps due to drop oscillation or increases in surface area (Bailes, 1981). Electrostatic theory and force balances have been used to determine the effects of the direct current field upon drop size and velocity (Vu and Carleson, 1986;Carleson and Berg, 1983;Takamatsu, et al, 1981).…”

Section: Introductionmentioning

confidence: 99%

“…Incorporating these effects, Vu and Carleson (1986) showed that the drop phase mass transfer coefficient should increase 8 % and 35 % for the continuous phase. Experimental measurements for dispersed phase control indic.ate an increase of around 25 % (Bailes, 1981), significantly higher than predicted.…”

Section: Introductionmentioning

confidence: 99%

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Effect of electric fields on mass transfer to droplets. Final report

Carleson¹,

Budwig²

1994

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During the six year funding period, the effects of a direct and alternating field upon single drop hydrodynamics and mass transfer were evaluated both experimentally and theoretically. Direct current field effects upon drop size, velocity and mass transfer rates were also observed for multiple drops formed in a three stage sieve tray column. Drop size, velocity, and mass transfer rates were measured experimentally and compared to simple models for direct current electric fields. Agreement between theory and experiment was found for drop charge, size, and velocity. Drop mass transfer coefficients were substantially larger than theoretical predictions while extraction efficiencies were moderately higher. Drop distortion and oscillation were observed and are thought to result in the experimentally observed higher values. For alternating current fields, drop flow streamlines and oscillations were measured and found to compare well with predictions from a solved mathematical model. In addition, equipment was constructed to determine mass transfer rates to oscillating drops. Concentration profiles in still and oscillating drops were measured and qualitatively compared to theoretical predictions. D_AIMER This reportwas preparedas an accountof worksponsoredby an agencyof the United States Government.Neitherthe United States Governmentnor any agencythereof,nor any of their employees,makes any warranty,expressor implied,or assumesany legal liabilityor responsibility for the accuracy,completeness, or usefulnessof any information, apparatus,product,or processdisclosed,or representsthat its use would not infringeprivatelyowned rights. Reference hereinto any specificcommercialproduct,process, or serviceby tradename,trademark, manufacturer, or otherwisedoes not necessarilyconstituteor imply its endorsement,recommendation,or favoringby the United States Governmentor any agency thereof.The views and opinions of authorsexpressedherein do not necessarilystate or reflect those of the United StatesGovernment or any agencythereof. %

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Section: Introductionmentioning

confidence: 74%

Section: Research Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of electric fields on mass transfer to droplets. Final report

Carleson¹,

Budwig²

1994

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“…Although there is so far no industrial scale application of electrically enhanced mass transfer in liquid-liquid extraction (Scott, 1989;Weatherley, 1992), investigations on some industrially related systems have been carried out. For example, extraction of nickel, copper, uranium and rare earths (Bailes, 1977(Bailes, , 1981Bailes and Wade, 1980;Martin et al, 1984;Hund and Lancelot, 1986), and extraction of penicillin G and other products from whole fermentation broths (Millar and Weatherley, 1989;Weatherley et al, 1990) have been reported. Table 1 shows that most of the work conducted with a uniform electric field was either confined to the interpretation of total mass transfer performance or restricted to the discrete droplet regime; and all systems selected had low viscosities.…”

Section: Electric Fieldsmentioning

confidence: 99%

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

He¹,

Baird²,

Chang³

1993

Can. J. Chem. Eng.

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Mass transfer of benzoic acid from drops dispersed into a continuous phase of mineral oil with high viscosity has been investigated both with and without an imposed non‐uniform d.c. electric field. Total mass transfer efficiency was significantly enhanced in the presence of the high voltage electric field. The results indicate that the application of the electric field to the drop formation process does not change the fundamental mass transfer mechanisms and the mass transfer during drop free fall can also be described by existing mass transfer models. The results also suggest that the high viscosity of the continuous phase inhibits the drops oscillation as well as circulation when the drop sizes become smaller under the applied high voltage electric field. Therefore the significant enhancement of mass transfer efficiency in the present work is mainly due to the increased specific interfacial area.

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Drop formation from an orifice in an electric field

Byers

Perona

1988

AIChE Journal

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The formation of dispersed phases a t needle tips and orifice plates has generated considerable practical interest in various separation processes. The influence of applied electric fields in reducing and controlling drop volume has already found use in electropainting and ink-jet printing. These applications are examples of electrohydrodynamic atomization in which the electric field is so intense that the liquid is disrupted into a spray of charged drops. In contrast, the present study concerns the formation of droplets in an immiscible liquid phase a t charges well below the Rayleigh stability limit. Here the results could be of importance in a broad range of liquid-liquid processes such as liquid-liquid extraction, where energy in the form of mechanical agitation is expended in the production of surface area.As a research area the behavior of charged drops in an electric field has received considerable investigation. Studies of drop shape and size, velocity of translation, and mass transfer with surrounding fluid have been published. Possible mass-transfer applications are suggested by the production of smaller drops and the promotion of internal circulation (Wham and Byers, 1987).Many investigators have found that drop volume decreases as a result of electric-field-application to drop formation a t nozzles from syringe needles (e.g., Vu and Carleson, 1986). In this investigation, drops were formed from an orifice plate with a geometry that is more commonly encountered in industry. Experiments were carried out with low fluid velocities a t the orifices, described by previous investigators as the "prejetting" or "single-drop'' regime. The charged orifice plate produced an axisymmetric, nonuniform field. Because the field is significantly influenced by the radius of the orifice plate, it was used as an experimental variable to help control the formation of drops in a field.To allow prediction of the electrostatic force on a drop, a theoretical model based on an ellipsoidal shape was developed. The model provided a good prediction of drop sizes over the ranges of variables for which its assumptions apply. ExperimentalWater drops were formed from an orifice enclosed in a glass column filled with cyclohexane. The charged orifice plate, 0.952 cm in diameter, was oriented horizontally and the water drops that formed fell downward toward a grounded stainless steel screen, Figures 1 and 2. The distance between the orifice plate and the screen was 5 cm and remained constant throughout the study. Plates were used with orifice diameters of 0.03175, 0.06350,0.09525 and 0.1524 cm.A static DC field was applied using a Hipotronics power supply with a range of 0 to 30 kV. A Tritronics Model PC5600, high-speed shuttered video camera was used to record the experiments. Shutter speed was varied from 4 to 0.1 ms, with framing rates of 60 to 300 frames per second. A Sony VO-5800 video recorder recorded the video image for playback and analysis of the results, while a F0R.A video timer VTG-33 recorded the date and time (to within 0...

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Electric field effects on drop size and terminal velocity in liquid‐liquid systems

Cited by 20 publications

References 3 publications

Effect of electric fields on mass transfer to droplets. Final report

Effect of electric fields on mass transfer to droplets. Final report

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

Drop formation from an orifice in an electric field

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