Natural Convection From Horizontal Disks and Rings

[+] Author and Article Information
M. Sahraoui, M. Kaviany

Department of Mechanical Engineering and Applied Mechanics, University of Michigan, Ann Arbor, MI 48109

H. Marshall

Computing Center, University of Michigan, Ann Arbor, MI 48109

J. Heat Transfer 112(1), 110-116 (Feb 01, 1990) (7 pages) doi:10.1115/1.2910331 History: Received July 21, 1988; Online May 23, 2008


A length scale similar to the hydraulic diameter for natural convection from horizontal surfaces has been previously suggested by others. This length scale correlates the available experimental results for circular, rectangular, and triangular surfaces fairly well. Herein this length scale is used for natural convection from rings. The obtained experimental (using naphthalene sublimation) and numerical (finite-difference approximation of the governing equations for axisymmetric fields) results confirm this length scale applicability to this class of multiply connected surfaces. Relatively good agreement is found between the experimental and numerical results for small inside diameters, while for large inside diameters the agreement is fair. These numerical results correlate well with Nu = 0.603 Ra1/5 Pr0.085 where the length scale is the ratio of area to perimeter of the heat transfer surface. A disk with an impermeable, adiabatic core is used numerically to explore the influence of the flow through the core on the local and average heat transfer rates. These numerical results correlate well with Nu = 0.561 Ra1/5 Pr0.085 . This indicates that the lack of core flow decreases the overall heat transfer rate by 7 percent.

Copyright © 1990 by The American Society of Mechanical Engineers
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