Numerical Study of EHD-Enhanced Forced Convection Using Two-Way Coupling

2003 ◽  
Vol 125 (4) ◽  
pp. 760-764 ◽  
Author(s):  
M. Huang ◽  
F. C. Lai
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Heat Transfer Enhancement ◽  
Forced Convection ◽  
Electric Fields ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Transfer Enhancement ◽  
Wide Range ◽  
The Difference

Numerical results are presented for heat transfer enhancement using electric field in forced convection in a horizontal channel. The main objective of the present study is to verify the assumption that is commonly used in the numerical study of this kind of problem, which assumes that the electric field can modify the flow field but not vice versa (i.e., the so-called one-way coupling). To this end, numerical solutions are obtained for a wide range of governing parameters (V0=10, 12.5, 15 and 17.5 kV as well as ui=0.0759 to 1.2144 m/s) using both one-way and two-way couplings. The results obtained, in terms of the flow, temperature, and electric fields as well as the heat transfer enhancement, are thoroughly examined. Since the difference in the results obtained by two approaches is insignificant, it is concluded that the assumption of one-way coupling is valid for the problem considered.

Numerical Study of EHD-Enhanced Forced Convection Using Two-Way Coupling

2001 ◽  
Author(s):  
M. Huang ◽  
F. C. Lai
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Heat Transfer Enhancement ◽  
Forced Convection ◽  
Electric Fields ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Transfer Enhancement ◽  
Wide Range ◽  
The One

Abstract In this paper, numerical results are presented for heat transfer enhancement using electric field in forced convection in a horizontal channel. The electric field is generated by charging a wire electrode located at the center of the channel with direct current at a high voltage. The main objective of the present study is to verify the assumption that is commonly used in the numerical study of this kind of problems, which assumes the electric field can modify the flow field but not vice versa (i.e., the so-called one-way coupling). To this end, numerical solutions have been obtained for a wide range of governing parameters (Vo = 10, 12.5, 15 and 17.5 kV as well as ui = 0.0759 to 1.2144 m/s) using both one-way and two-way couplings. Using the two-way coupling approach, the possible modification of the electric field by the primary flow, which was previously neglected, is accounted for. The results obtained using these two approaches, in terms of the flow, temperature, and electric fields as well as the heat transfer enhancement, are thoroughly examined. In addition, their influence over the flow stability is investigated. Finally, the conclusion about the validity of the one-way coupling is reached at the end of the study.

Heat Transfer Enhancement by EHD-Induced Oscillatory Flows

2005 ◽  
Author(s):  
F. C. Lai ◽  
J. Mathew
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Heat Transfer Enhancement ◽  
Numerical Solutions ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Temperature Fields ◽  
Transfer Enhancement ◽  
Periodic Flows ◽  
Small Reynolds Numbers

Prior numerical solutions of electrohydrodynamic (EHD) gas flows in a horizontal channel with a positive-corona discharged wire have revealed the existence of steady-periodic flows. It is speculated that heat transfer by forced convection may be greatly enhanced by taking advantage of this oscillatory flow phenomenon induced by electric field. To verify this speculation, computations have been performed for flows with Reynolds numbers varying from 0 to 4800 and the dimensionless EHD number (which signifies the effect of electric field) ranging from 0.06 to ∞. The results show that heat transfer enhancement increases with the applied voltage. For a given electric field, oscillation in the flow and temperature fields occurs at small Reynolds numbers. Due to the presence of oscillatory secondary flows, there is a significant enhancement in heat transfer.

Interactions Between Bubbles in Close Proximity Under Uniform and Non-Uniform Electric Fields

2007 ◽  
Author(s):  
Matthew R. Pearson ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Heat Transfer Enhancement ◽  
Electric Fields ◽  
Nucleate Boiling ◽  
Numerical Results ◽  
Electrode Spacing ◽  
Transfer Enhancement ◽  
Close Proximity ◽  
Multiple Bubbles

It is widely known that dielectrophoretic force can be harnessed to enhance the separation of liquid and vapor phases, with several known benefits in heat transfer enhancement. It has been shown that, when the electrode spacing and the bubble radius are of the same order of magnitude, the presence of the electric field can significantly deform the bubble, and this deformation can significantly affect the bubble’s behavior. Additionally, the presence of a bubble can provide significant, local distortion of the electric field. Consequently, the existence of multiple bubbles in close proximity may generate interactions that serve to further affect bubble deformation and motion behavior. Of course, nucleate boiling involves the generation of several bubbles in close proximity, and it is useful to understand whether these interactions may favorably or adversely affect the potential for heat transfer enhancement. This numerical study simulates the behavior of two and three bubbles within an external, electric field. The geometric deformation of the bubbles due to the electric field and the distortion of the electric field due to the existence of the bubbles are both incorporated into the mathematical model. The numerical results provide information about the effect that one bubble can have on the others’ motion, and also illustrate any tendencies of the bubbles to attract or repel each other when subject to various electric fields. Based on the numerical results, conclusions are drawn on the implications that the observed phenomenon may have on heat transfer enhancement applications.

Numerical Study of Forced Convection in a Partially Porous Channel With Discrete Heat Sources

1995 ◽  
Vol 117 (1) ◽  
pp. 46-51 ◽  
Author(s):  
H. A. Hadim ◽  
A. Bethancourt
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Pressure Drop ◽  
Heat Source ◽  
Heat Transfer Enhancement ◽  
Forced Convection ◽  
Numerical Study ◽  
Heat Sources ◽  
Transfer Enhancement ◽  
Discrete Heat Sources

A numerical study was performed to analyze steady laminar forced convection in a channel partially filled with a fluid-saturated porous medium and containing discrete heat sources on the bottom wall. Hydrodynamic and heat transfer results are reported for the configuration in which the porous layers are located above the heat sources while the rest of the channel is nonporous. The flow in the porous medium was modeled using the Brinkman-Forchheimer extended Darcy model. Parametric studies were conducted to evaluate the effects of variable heat source spacing and heat source width on heat transfer enhancement and pressure drop in the channel. The results indicate that when the heat source spacing was increased within the range considered, there was a negligible change in heat transfer enhancement while the pressure drop decreased significantly. When the heat source width was decreased, there was a moderate increase in heat transfer enhancement and a significant decrease in pressure drop.

Heat Transfer Enhancement by EHD-Induced Oscillatory Flows

2006 ◽  
Vol 128 (9) ◽  
pp. 861-869 ◽  
Author(s):  
F. C. Lai ◽  
J. Mathew
Keyword(s):  
Heat Transfer ◽  
Electric Field ◽  
Heat Transfer Enhancement ◽  
Numerical Solutions ◽  
Reynolds Numbers ◽  
Secondary Flows ◽  
Temperature Fields ◽  
Transfer Enhancement ◽  
Periodic Flows ◽  
Small Reynolds Numbers

Prior numerical solutions of electrohydrodynamic (EHD) gas flows in a horizontal channel with a positive-corona discharged wire have revealed the existence of steady-periodic flows. It is speculated that heat transfer by forced convection may be greatly enhanced by taking advantage of this oscillatory flow phenomenon induced by electric field. To verify this speculation, computations have been performed for flows with Reynolds numbers varying from 0 to 4800 and the dimensionless EHD number (which signifies the effect of electric field) ranging from 0.05 to ∞. The results show that heat transfer enhancement increases with the applied voltage. For a given electric field, oscillation in the flow and temperature fields occurs at small Reynolds numbers. Due to the presence of oscillatory secondary flows, there is a significant enhancement in heat transfer.

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