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ICHMT DIGITAL LIBRARY ONLINE

ISSN 961-91393-0-5

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Year 2005

• 18th Australasian Heat and Mass Transfer Conference
Curtin University of Technology, Perth, Western Australia, 26-29 July 2005

239 pages

Volume price - $518.00

The Conduction and Convection Regimes in a Cavity with Evenly Heated and Cooled Vertical Walls

G. D. McBain
School of Aerospace, Mechanical, & Mechatronic Engineering, The University of Sydney, Darlington NSW 2006 Australia

Steven Armfield
Sydney University

S. Jiracheewanun
School of Aerospace, Mechanical, & Mechatronic Engineering, The University of Sydney, Darlington NSW 2006 Australia

ABSTRACT

We treat natural convection in a plane vertical rectangular cavity with one vertical wall evenly heated, the other cooled, and an adiabatic floor and ceiling. We predict the temperature difference across the cavity by simple analysis, and present numerical solutions verifying the results.
If the cavity is infinitely tall, there is an exact steady one-dimensional solution depending on a single parameter: the stratification. This quantity is not prescribed by the boundary conditions, but can be determined analytically from an energy balance on a suitable control volume. This allows the calculation of the cross-cavity temperature difference (the Nusselt number−Rayleigh number relation) over the entire laminar range of Rayleigh numbers, for all Prandtl numbers, and for all sufficiently large aspect ratios. The result links the trivial conduction limit to the Kimura−Bejan boundary layer approximation, which is also shown to be asymptotically correct.
Numerical solutions verify the conduction−convection transition for the Nusselt number. They also indicate the dependence on the parameters of the problem (Rayleigh and Prandtl numbers) of the bound on the aspect ratio for the applicability of the approach: that is, the minimum separation of ceiling from floor which permits a fully developed region.