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Forced Convection

Hydrodynamic and Thermal Characteristics of Combined Electroosmotic and Pressure Driven Flow in a Microannulus

[+] Author and Article Information
Hadi Yavari

Center of Excellence in Energy Conversion (CEEC), School of Mechanical Engineering, Sharif University of Technology, P.O. Box 11155-9567, Tehran, Iranhadiyavari@alum.sharif.edu

Arman Sadeghi

Center of Excellence in Energy Conversion (CEEC), School of Mechanical Engineering, Sharif University of Technology, P.O. Box 11155-9567, Tehran, Iranarmansadeghi@mech.sharif.edu

Mohammad Hassan Saidi1

Center of Excellence in Energy Conversion (CEEC), School of Mechanical Engineering, Sharif University of Technology, P.O. Box 11155-9567, Tehran, Iransaman@sharif.edu

1

Corresponding author.

J. Heat Transfer 134(10), 101703 (Aug 07, 2012) (10 pages) doi:10.1115/1.4006816 History: Received September 19, 2011; Revised April 30, 2012; Published August 06, 2012; Online August 07, 2012

The present study considers both the hydrodynamic and thermal characteristics of combined electroosmotic and pressure driven flow in a microannulus. Analytical solutions are presented using the Debye–Hückel linearization along with the uniform Joule heating and negligible viscous dissipation assumptions, whereas exact results are achieved numerically. Here, the range of validity for the Debye–Hückel linearization is found to be about two times of that for a parallel plate microchannel. Accordingly, this linearization may successfully be used to evaluate the potential and velocity distributions up to the zeta potentials of 100 mV, provided that the dimensionless Debye–Hückel parameter is above 10; nevertheless, the calculated wall shear stresses may be significantly different from the exact ones, even for lower zeta potentials. The viscous heating effects are found to be limited to low values of the dimensionless Debye–Hückel parameter. These effects are pronounced in the presence of a favorable pressure gradient, whereas the opposite is true for an opposed pressure gradient. Furthermore, the influence of increasing the annular geometry parameter, that is the inner to outer radii ratio, generally is to decrease both the inner and outer Nusselt numbers. It is also revealed that the pressure effects vanish at higher values of this parameter.

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Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Geometry of the physical problem, coordinate system, and electric double layer

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Figure 2

Grid dependency of the Poiseuille number values

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Figure 3

Radial distribution of ψ* at different values of K

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Figure 4

Radial distribution of u* at different values of K (a) β=1 and (b) β=-1

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Figure 5

Radial distribution of u* at different values of Γ

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Figure 6

Variations of u¯* with respect to α at different values of Γ

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Figure 7

Variations of fRe with respect to K at different values of ζ*

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Figure 8

Radial distribution of θ at different values of K

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Figure 9

Variations of the inner and outer Nusselt numbers with respect to K at different values of ζ*

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Figure 10

Variations of (Ev/Ee)/Sv with respect to K at different values of β

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Figure 11

Variations of (Ev/Ee)/Sv with respect to α at different values of Γ

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Figure 12

Inner and outer Nusselt numbers as functions of Sv at different values of K

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Figure 13

Variations of the Nusselt numbers with respect to α at different values of Γ

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