Effects of Temperature-Dependent Viscosity Variation on Entropy Generation,Heat,and Fluid Flow Through a Porous-Saturated Duct of Rectangular Cross-Section

K. Hooman; H. Gurgenci

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K. Hooman, H. Gurgenci. Effects of Temperature-Dependent Viscosity Variation on Entropy Generation,Heat,and Fluid Flow Through a Porous-Saturated Duct of Rectangular Cross-Section[J]. Applied Mathematics and Mechanics, 2007, 28(1): 61-69.

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Effects of Temperature-Dependent Viscosity Variation on Entropy Generation,Heat,and Fluid Flow Through a Porous-Saturated Duct of Rectangular Cross-Section

School of Engineering, The University of Queensland, Brisbane, Australia

Received Date: 2006-03-15
Rev Recd Date: 2006-09-07
Publish Date: 2007-01-15

Abstract

Abstract

Effect of temperature-dependent viscosity on fully developed forced convection in a duct of rectangular cross-section occupied by a fluid-saturated porous medium is investigated analytically. The Darcy flow model was applied and the viscosity-temperature relation was assumed to be an inverse-linear one. The case of uniform heat flux on the walls, i. e. the H boundary condition in the terminology of Kays and Crawford, was treated. For the case of a fluid whose viscosity decreases with temperature, it is found that the effect of the variation is to increase the Nusselt number for heated walls. Having found the velocity and the temperature distribution, the second law of thermodynamics was invoked to find the local and average entropy generation rate. Expressions for the entropy generation rate, the Bejan number, the heat transfer irreversibility, and the fluid flow irreversibility were presented in terms of the Brinkman number, the P clet number, the viscosity variation number, the dimensionless wall heat flux, and the aspect ratio (width to height ratio). These expressions let a parametric study of the problem based on which it is observed that the entropy generated due to flow in a duct of square cross-section is more than those of rectangular counterparts while increasing the aspect ratio decreases the entropy generation rate similar to what previously reported for the clear flow case by Ratts and Raut.
- entropy generation rate,
- forced convection,
- porous medium,
- rectangular duct,
- temperature-dependent viscosity

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References(24)

References

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