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ISSN Online: 2377-424X

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

Local heat/mass transfer characteristics in a square duct with various rib arrangements

Get access (open in a dialog) DOI: 10.1615/IHTC12.5170
6 pages

Sinopsis

The present study investigates the effects of rib arrangements and gap positions on the rib on local heat/mass transfer in a duct. The combined effects of the gap flows of the discrete ribs and the secondary flows are examined for the purpose of the promotion of the uniformity of heat/mass transfer distributions as well as the augmentation of heat/mass transfer. A square channel with rectangular ribs is used for the stationary duct test. The rib-to-rib pitch to the rib height ratio of 8, and the rib attack angle of 60 deg. The gap width is 5 mm and two gap positions, which are upstream and downstream gaps, are examined. A naphthalene sublimation method is used to measure local heat/mass transfer coefficients. A complex flow structure occurs in the cooling passage with rib turbulators that promote heat transfer on the wall. Therefore, a numerical computation is performed using a commercial code to calculate the flow structures. The parallel rib arrangements make a pair of counter rotating secondary flows in the cross section, while the cross rib arrangements make a single rotating secondary flow including small vortices. These secondary flow patterns affect significantly the heat/mass transfer on the ribbed wall. Though the gap flow of the discrete ribs is relatively weaker than the rib-induced secondary flow, it promotes local turbulence and flow mixing near the ribbed wall.