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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/5625

Title: Natural convection heat transfer from horizontal rectangular ducts
Authors: Ali, Mohamed E.
Keywords: Natural Convection
Rectangular Ducts
Experimental Heat Transfer
Issue Date: Aug-2007
Publisher: American Society of Mechanical Engineers
Citation: Journal of Heat Transfer: 129
Abstract: Experimental investigations have been reported on steady state natural convection from the outer surface of horizontal ducts in air. Five ducts have been used with aspect ratios ( duct height/duct width) of 2, 1, and 0.5. The ducts are heated using internal constant heat flux heating elements. The temperatures along the surface and peripheral directions of the duct wall are measured. Longitudinal (circumference averaged) heat transfer coefficients along the side of each duct are obtained for laminar and transition regimes of natural convection heat transfer. Total overall averaged heat transfer coefficients are also obtained. Longitudinal (circumference averaged) Nusselt numbers are evaluated and correlated using the modified Rayleigh numbers for transition regime using the axial distance as a characteristic length. Furthermore, total overall averaged Nusselt numbers are correlated with the modified Rayleigh numbers, the aspect ratio, and area ratio for the laminar and transition regimes. The longitudinal or total averaged heat transfer coefficients are observed to decrease in the laminar region and to increase in the transition region. Laminar regimes are obtained only at very small heat fluxes, otherwise, transitions are observed.
URI: 10.1115/1.2739623
ISSN: 0022-1481
Appears in Collections:College of Engineering

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