Flow and heat/mass transfer in a wavy duct with various corrugation angles in two dimensional flow regimes |
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Authors: | Hyun Goo Kwon Sang Dong Hwang Hyung Hee Cho |
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Institution: | (1) Department of Mechanical Engineering, Yonsei University, Seoul, 120-749, South Korea;(2) Korean Intellectual Property Office, Daejeon, 302-701, South Korea |
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Abstract: | In this study, two dimensional heat/mass transfer characteristics and flow features were investigated in a rectangular wavy
duct with various corrugation angles. The test duct had a width of 7.3 mm and a large aspect ratio of 7.3 to simulate two
dimensional characteristics. The corrugation angles used were 100°, 115°, 130°, and 145°. Numerical analysis using the commercial
code FLUENT, was used to analyze the flow features. In addition, the oil-lamp black method was used for flow visualization.
Local heat/mass transfer coefficients on the corrugated walls were measured using a naphthalene sublimation technique. The
Reynolds number, based on the duct hydraulic diameter, was varied from 700 to 5,000. The experimental results and numerical
analysis showed interesting and detailed features in the wavy duct. Main flow impinged on upstream of a pressure wall, and
the flow greatly enhanced heat/mass transfer. On a suction wall, however, flow separation and reattachment dominantly affected
the heat/mass transfer characteristics on the wall. As the corrugation angle decreased (it means the duct has more sharp turn),
the region of flow stagnation at the front part of the pressure wall became wider. Also, the position of flow reattachment
on the suction wall moved upstream as the corrugation angle decreased. A high heat transfer rate appeared at the front part
of the pressure wall due to main-flow impingement, and at the front part of the suction wall due to flow reattachment. The
high heat/mass transfer region by the main-flow impingement and the circulation flow induced at a valley between the pressure
and suction walls changed with the corrugation angle and the Reynolds number. As the corrugation angle decreased, the flow
in the wavy duct changed to transition to turbulent flow earlier. |
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