RESEARCH PAPERS: Natural and Mixed Convection

Natural Convection Heat Transfer in Horizontal Rod-Bundle Enclosures

[+] Author and Article Information
M. Keyhani, T. Dalton

Mech. & Aerospace Eng. and Engineering Science Department, The University of Tennessee, Knoxville, TN 37996-2210

J. Heat Transfer 118(3), 598-605 (Aug 01, 1996) (8 pages) doi:10.1115/1.2822674 History: Received August 14, 1995; Revised April 02, 1996; Online December 05, 2007


Natural convection heat transfer in enclosed horizontal N × N arrays (N = 3, 5, and 7) of electrically heated rods with a pitch-to-diameter ratio (P/d) of 1.35 has been experimentally investigated. Each array was positioned in an isothermal square enclosure with a width-to-diameter ratio (W/d) of 20.6. Pressurized air or helium was used as the working fluid. It was observed that the bottom-tow rods were relatively insensitive to increases in the array size, as they exhibit only slight temperature variations, but the top-row rods demonstrated substantial temperature increases. Natural convection correlations in the form of Nusselt number (Nud ) as a function of modified Rayleigh number (Rad *) were obtained for each rod in each array. The correlations cover three flow regimes of conduction, transition, and convection in the range of 6.45 < Rad * < 3.08 × 105 . A generalized enclosure Nusselt number was correlated as a function of enclosure modified Rayleigh number and the array size (N). Comparison of the data with previous numerical prediction showed that this correlation may be readily used to obtain a conservative estimate of the maximum temperature in the arrays with N = 3, 5, 7, and 9.

Copyright © 1996 by The American Society of Mechanical Engineers
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