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Research Papers: Micro/Nanoscale Heat Transfer

Non-Newtonian Fluid Flow and Heat Transfer in a Semicircular Microtube Induced by Electroosmosis and Pressure Gradient

[+] Author and Article Information
Mehdi Karabi

Faculty of Mechanical Engineering,
Shahrood University of Technology,
Shahrood 3619995161, Iran

Ali Jabari Moghadam

Faculty of Mechanical Engineering,
Shahrood University of Technology,
Shahrood 3619995161, Iran
e-mail: jm.ali.project@gmail.com

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received May 17, 2018; final manuscript received August 1, 2018; published online September 25, 2018. Assoc. Editor: Danesh K. Tafti.

J. Heat Transfer 140(12), 122403 (Sep 25, 2018) (9 pages) Paper No: HT-18-1315; doi: 10.1115/1.4041189 History: Received May 17, 2018; Revised August 01, 2018

The hydrodynamic and thermal characteristics of electroosmotic and pressure-driven flows of power-law fluids are examined in a semicircular microchannel under the constant wall heat flux condition. For sufficiently large values of the electrokinetic radius, the Debye length is thin; the active flow within the electric double layer (EDL) drags the rest of the liquid due to frictional forces arising from the fluid viscosity, and consequently a plug-like velocity profile is attained. The velocity ratio can affect the pure electrokinetic flow as well as the flow rate depending on the applied pressure gradient direction. Since the effective viscosity of shear-thinning fluids near the wall is quite small compared to the shear-thickening fluids, the former exhibits higher dimensionless velocities than the later close to the wall; the reverse is true at the middle section. Poiseuille number increases with increasing the flow behavior index and/or the electrokinetic radius. Due to the comparatively stronger axial advection and radial diffusion in shear-thinning fluids, better temperature uniformity is achieved in the channel. Reduction of Nusselt number continues as far as the fully developed region where it remains unchanged; as the electrokinetic radius tends to infinity, Nusselt number approaches a particular value (not depending on the flow behavior index).

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Figures

Grahic Jump Location
Fig. 2

Dimensionless potential contours for (a) η=101 and (b) η=103

Grahic Jump Location
Fig. 1

(a) Computational domain (b) geometrical cross section

Grahic Jump Location
Fig. 3

Dimensionless velocity contours for η=103, and (a) n=0.6,Γ=−1, (b) n=1.4,Γ=−1, (c) n=0.6,Γ=1, and (d) n=1.4,Γ=1

Grahic Jump Location
Fig. 4

Dimensionless velocity profiles at the symmetric plane for (a) n=0.6,Γ=−1, (b) n=0.6,Γ=1, (c) n=1.4,Γ=−1, and (d) n=1.4,Γ=1

Grahic Jump Location
Fig. 5

Dimensionless velocity profiles at the symmetric plane for various values of n, Γ, and η

Grahic Jump Location
Fig. 6

The scaled Dimensionless temperature contours for η=100, Γ=−1 and (a) n=0.6,z*=L*/10, (b) n=0.6,z*=L*/5, (c) n=1.4,z*=L*/10, and (d) n=1.4,z*=L*/5

Grahic Jump Location
Fig. 7

(a) The scaled dimensionless temperature at the symmetric plane for various axial distances, (b) dimensionless bulk temperature versus axial distances for various η values, (c) dimensionless bulk temperature versus axial distances for various values of n and Γ, and (d) the scaled dimensionless temperature at the exit section for different angular positions

Grahic Jump Location
Fig. 8

Nusselt number versus axial distances for various values of (a) η and (b) n,Γ

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