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ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Turbulent momentum and heat transfer in ducts of rhombic cross section

Get access (open in a dialog) DOI: 10.1615/IHTC12.1310
6 pages

Аннотация

Direct numerical simulation of fully developed turbulent velocity and temperature fields in rhombic ducts with five different acute angles, θ, are carried out. The Reynolds number Reb based on the bulk mean streamwise velocity and the hydraulic diameter, and the Prandtl number are about 4470 and 0.71, respectively. The mean streamwise velocity and associated mean secondary velocity vectors are obtained at each θ. The systematic change of the secondary flow pattern in the rhombic ducts is clarified. As θ is decreased, a pair of counter-rotating vortices are distorted near the acute angle corner, and they eventually break up into two pairs at θ = 30°. It is found that the square duct of θ = 90° gives the best heat transfer performance among the rhombic ducts tested. The dissimilarity between momentum and heat transfer exists and is stronger near the acute corners than near the obtuse ones. This is caused by the dissimilarity inherent in the velocity and thermal boundary conditions, and also by the streamwise velocity decelerated by the corner effect, particularly at the acute corners. For designing thermal mechanical equipment, the duct that has only obtuse corners would be more efficient than that with acute corners.