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Research Papers: Porous Media

Natural Convection Reduction in a Composite Air/Porous Annular Region With Horizontal Orientation

[+] Author and Article Information
M. Ait saada, S. Chikh

Faculté de Génie Mécanique et de Génie des Procédés, Université des Sciences et de la Technologie Houari Boumediene, B.P. 32, El Alia, Bab Ezzouar 16111, Algeria

A. Campo1

Department of Mechanical Engineering, The University of Vermont, Burlington, VT 05405campanto@yahoo.com

Also named unicellular flow.

1

Corresponding author.

J. Heat Transfer 131(2), 022601 (Dec 12, 2008) (8 pages) doi:10.1115/1.2993544 History: Received October 31, 2007; Revised July 10, 2008; Published December 12, 2008

This paper deals with a numerical investigation on natural convection heat transfer in a long horizontal annular region formed with a heated inner cylinder and a cooled outer cylinder. Identifying the annular region geometrically by its radius ratio, it is divided into two subregions: a thicker outer subregion is filled with a porous material saturated by air, whereas a thinner inner subregion is clear. Based on the general Darcy–Brinkman–Forchheimer model for flow in porous media, numerical calculations with the control volume method produce the velocity and temperature fields of the air motion in the two subregions. The baseline case corresponds to an annular region of same dimensions, but filled completely with a porous material saturated by air. Upon articulating the physical properties of a porous material with the clear gap size, the analyst will be able to tune those conditions that are conducive to heat transfer reduction across the concentric two-cylinder configuration. The outcome of this paper is equivalent to the determination of superior thermal insulation performance using lesser porous material. In other words, this paper boils down to beneficial energy conservation together with money savings in the purchase of the thermal insulation.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Physical system and computation domain

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Figure 2

Streamlines and isotherms in a partially porous annulus for Ra=106 and Da=10−8: effect of ea∗ for (a) Rc=2 and (b) Rc=10

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Figure 3

Influence of ea∗ and Da on the mean Nusselt number for Ra=106

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Figure 4

Heat transfer reduction in a partly porous annulus for Ra=106: (a) conduction and convection contributions in total heat losses and (b) total heat losses

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Figure 5

Air-gap size for optimal thermal insulation

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Figure 6

Heat transfer performance in a partly porous annulus for Ra=106 and Rc=10

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Figure 7

Heat transfer performance for thermal insulation when Da=10−8

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