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Research Papers: Porous Media

# Second Law Analysis for Free Convection in Non-Newtonian Fluids Over a Horizontal Plate Embedded in a Porous Medium: Prescribed Surface Temperature

[+] Author and Article Information
W. A. Khan1

Department of Mechanical Engineering, National University of Sciences and Technology, Karachi, Pakistanwkhan_2000@yahoo.com

Rama Subba Reddy Gorla

Department of Mechanical Engineering, Cleveland State University, Cleveland, OH 44114

1

Corresponding author.

J. Heat Transfer 133(5), 052601 (Feb 02, 2011) (7 pages) doi:10.1115/1.4003045 History: Received April 18, 2010; Revised November 12, 2010; Published February 02, 2011; Online February 02, 2011

## Abstract

Second law characteristics of heat transfer and fluid flow due to free convection of non-Newtonian fluids over a horizontal plate with prescribed surface temperature in a porous medium are analyzed. Velocity and temperature fields are obtained numerically using an implicit finite difference method under the similarity assumption and these results are used to compute the entropy generation rate $Ns$, irreversibility ratio $Φ$, and the Bejan number Be for both Newtonian and non-Newtonian fluids. The effects of viscous frictional parameter $G$, Rayleigh number Ra, temperature variation $λ$, axial distance $(x)$ on the dimensionless entropy generation rate $Ns$, and the Bejan number Be are investigated for Newtonian and non-Newtonian fluids and presented graphically.

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## Figures

Figure 1

Flow model and coordinate system

Figure 2

Velocity profiles showing effects of λ and different power-law fluids

Figure 3

Temperature profiles showing effects of λ and different power-law fluids

Figure 4

Variation of dimensionless entropy generation rate with η showing effects of λ, G, Ω, Ra, and axial distance x for a Newtonian fluid

Figure 5

Variation of dimensionless entropy generation rate with η showing effects of G, Ω, Ra, and axial distance x for a pseudoplastic fluid

Figure 6

Variation of dimensionless entropy generation rate with η showing effects of G, Ω, Ra, and axial distance x for a dilatant fluid

Figure 7

Variation of Bejan number with η showing effects of G, Ω, Ra, and axial distance x for a Newtonian fluid

Figure 8

Variation of Bejan number with η showing effects of G, Ω, Ra, and axial distance x for a pseudoplastic fluid

Figure 9

Variation of Bejan number with η showing effects of G, Ω, Ra, and axial distance x for a dilatant fluid

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