Lateral Intrusion of Natural Convection into a Horizontal Porous Structure

[+] Author and Article Information
Adrian Bejan

Department of Mechanical Engineering, University of Colorado, Boulder, CO 80309

J. Heat Transfer 103(2), 237-241 (May 01, 1981) (5 pages) doi:10.1115/1.3244447 History: Received June 16, 1980; Online October 20, 2009


This article illustrates the fundamental features of lateral penetration of natural convection into a horizontal porous layer in lateral communication with a heat reservoir. It is found that the important group governing the fluid mechanics of the phenomenon is the Darcy-modified Rayleigh number Ra based on longitudinal (horizontal) permeability and on transversal (vertical) thermal diffusivity. It is shown that the buoyancy-driven flow has flattened C-shaped streamlines and isotherms. The flow penetrates laterally to a distance of order H Ra1/2 , where H is the height of the porous layer. The net heat exchange between the porous structure and the lateral heat reservoir is described by a Nusselt number result of the type Nu ∼ Ra1/2 . The effect of horizontal wall temperature gradient on penetration length and heat transfer is discussed. The engineering importance of these findings is illustrated by examples related to the conceptual design of porous winding structures for rotating superconducting electric machines.

Copyright © 1981 by ASME
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