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RESEARCH PAPERS: Bubbles, Particles and Droplets

Enhancement of Heat Transfer by an Electric Field for a Drop Translating at Intermediate Reynolds Number

[+] Author and Article Information
Rajkumar Subramanian

Department of Mechanical, Industrial, and Nuclear Engineering,  University of Cincinnati, Cincinnati, OH 45221-0072

M. A. Jog1

Department of Mechanical, Industrial, and Nuclear Engineering,  University of Cincinnati, Cincinnati, OH 45221-0072milind.jog@uc.edu

1

To whom correspondence should be addressed.

J. Heat Transfer 127(10), 1087-1095 (May 05, 2005) (9 pages) doi:10.1115/1.2033906 History: Received September 11, 2004; Revised May 05, 2005

The enhancement of heat transfer by an electric field to a spherical droplet translating at intermediate Reynolds number is numerically investigated using a finite volume method. Two heat transfer limits are considered. The first limit is the external problem where the bulk of the resistance is assumed to be in the continuous phase. Results show that the external Nusselt number significantly increases with electric field strength at all Reynolds numbers. Also, the drag coefficient increases with electric field strength. The enhancement in heat transfer is higher with lower ratio of viscosity of the dispersed phase to the viscosity of the continuous phase. The second heat transfer limit is the internal problem where the bulk of the resistance is assumed to be in the dispersed phase. Results show that the steady state Nusselt number for a combined electrically induced and translational flow is substantially greater than that for purely translational flow. Furthermore, for a drop moving at intermediate Reynolds number, the maximum steady state Nusselt number for a combined electrically induced and translational flow is slightly greater than that for a purely electric field driven motion in a suspended drop.

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Copyright © 2005 by American Society of Mechanical Engineers
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References

Figures

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Figure 5

Variation of surface pressure for W=0 and 1, Re=50, and kμ=3

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Figure 6

Variation of drag coefficient with Reynolds numbers for different values of W with kμ=3

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Figure 8

Local Nusselt number variation with application of electric field at Re=50, Pr1=5, and kμ=3

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Figure 9

Enhancement in average Nusselt number with W for different values of Reynolds number (20, 50, 80, and 100), Pr1=5, and kμ=3

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Figure 10

Variation of Nusselt number with dimensionless time t=t*α2∕R2 for Re=50, Pr2=21.21, and kμ=3

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Figure 11

Variation of steady state Nusselt number with Peclet number, Re=80, and kμ=3

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Figure 12

Comparison of internal stream lines for flow due to electric field and translational motion at Re=80 (dashed lines), and internal stream lines for purely electric field driven flow for a suspended drop (solid lines)

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Figure 13

Variation of drag coefficient with W for different viscosity ratios kμ=0.7, 1.1, 3, 5, and 10, Re=50

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Figure 14

Enhancement of heat transfer with W for different viscosity ratios kμ=0.7, 1.1, 3, 5, and 10, Re=50, and Pr1=5

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Figure 1

Schematic diagram showing the coordinate system and streamlines for purely translating drop and for purely electric field driven flow for a suspended drop

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Figure 2

Comparison of the transient variation of Nusslet number with Chung and Oliver (Ref. 5). Chung and Oliver have used a notation where the relative electric field strength is called E (instead of W).

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Figure 3

Internal and external streamlines for W=0 and 1, Re=50, kμ=3

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Figure 4

Internal and external streamlines for W=5 and 10, Re=50, kμ=3

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Figure 7

External isotherms for W=0 and 5 at Re=50, Pr1=5, and kμ=3

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