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RESEARCH PAPERS: Forced Convection

Heat Transfer Enhancement by EHD-Induced Oscillatory Flows

[+] Author and Article Information
F. C. Lai1

School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019flai@ou.edu

J. Mathew2

School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019

1

Corresponding author.

2

Presently at ClimateCraft, Oklahoma City, OK.

J. Heat Transfer 128(9), 861-869 (Mar 01, 2006) (9 pages) doi:10.1115/1.2241761 History: Received June 02, 2005; Revised March 01, 2006

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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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 6

Steady flow and temperature fields in a channel with two wire electrodes at V0=15kV: (a) Stream functions (ΔΨ=0.015 for Re=2400, ΔΨ=0.02 for Re=3600, and ΔΨ=0.03 for Re=4800), (b) isotherms (Δθ=0.1)

Grahic Jump Location
Figure 7

Variation of flow field (stream functions) with time in a channel with one wire electrode (V0=15kV, Re=1200, ΔΨ=0.008): (a)τ=500, (b)τ=506.5, (c)τ=513, (d)τ=519.5, (e)τ=526, (f)τ=532.5

Grahic Jump Location
Figure 8

Variation of temperature field (isotherms) with time in a channel with one wire electrode (V0=15kV,Re=1200,Δθ=0.1): (a)τ=500, (b)τ=506.5, (c)τ=513, (d)τ=519.5, (e)τ=526, (f)τ=532.5

Grahic Jump Location
Figure 9

Variation of flow field (stream functions) with time in a channel with two wire electrodes (V0=15kV,Re=1200,ΔΨ=0.012): (a)τ=400, (b)τ=409.1, (c)τ=418.2, (d)τ=427.3, (e)τ=436.4, (f)τ=445.5

Grahic Jump Location
Figure 10

Variation of temperature field (isotherms) with time in a channel with two wire electrodes (V0=15kV,Re=1200,Δθ=0.1): (a)τ=400, (b)τ=409.1, (c)τ=418.2, (d)τ=427.3, (e)τ=436.4, (f)τ=445.5

Grahic Jump Location
Figure 11

Heat transfer enhancement by electric field, (a) one wire electrode, (b) two wire electrodes

Grahic Jump Location
Figure 5

Steady flow and temperature fields in a channel with one wire electrode at V0=15kV: (a) Stream functions (ΔΨ=0.015 for Re=2400, ΔΨ=0.02 for Re=3600, and ΔΨ=0.03 for Re=4800), (b) isotherms (Δθ=0.1)

Grahic Jump Location
Figure 4

Variation of Nusselt number with time (two electrodes at V0=15kV): (a)Re=75(NEHD=1191.85); (b)Re=150(NEHD=297.96), (c)Re=300(NEHD=74.49), (d)Re=600(NEHD=21.19), (e)Re=900(NEHD=9.01), (f)Re=1200(NEHD=5.30), (g)Re=1500(NEHD=3.30), (h)Re=1800(NEHD=2.25), (i)Re=2100(NEHD=1.70), (j)Re=2400(NEHD=1.28)

Grahic Jump Location
Figure 3

Variation of Nusselt number with time (one electrode at V0=15kV): (a)Re=75(NEHD=969.57), (b)Re=150(NEHD=242.39), (c)Re=300(NEHD=60.60), (d)Re=600(NEHD=15.15), (e)Re=900(NEHD=6.73), (f)Re=1200(NEHD=3.79), (g)Re=1500(NEHD=2.42), (h)Re=2100(NEHD=1.24)

Grahic Jump Location
Figure 2

Transition of flow fields under the influence of electric field (a) one wire electrode, (b) two wire electrodes

Grahic Jump Location
Figure 1

A horizontal channel with (a) one wire electrode, (b) two wire electrodes (d=3cm, s=4.8cm, and L=25.8cm)

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