Annals of the Assembly for International Heat Transfer Conference 13

ISBN 1-56700-225-0 / CD 1-56700-226-9

Year 2006

S. D. Hwang
Machinery, Metal & Construction Exam. Bureau, Korea Intellectual Property Office(KIPO), Daejeon, Korea

H. H. Cho
Department of Mechanical Engineering, Yonsei University, Seoul 120-749, Korea

An experimental study was conducted to investigate the heat transfer and pressure drop of a rectangular channel with the dimpled and/or protruded walls. In the present study, three different roughened surfaces of dimpled, protruded and complex(dimple-protrusion) surface were tested. The dimples/protrusions were installed at both top and bottom walls of the rectangular channel. The local heat transfer coefficients on the dimpled/protruded walls were measured using a transient TLC(Thermocromic Liquid Crystal) technique. The friction factors of the rectangular channel with dimples/protrusions were obtained using pressure taps installed at the channel side wall. And the performance factors, which indicate the enhancement levels by both considerations of heat transfer enhancements and pressure loss increases were evaluated. As a result, high heat transfer region appeared at the rear side of the dimple due to the increased flow mixing on the dimpled surface. For the protruded surface, heat transfer was enhanced on the front side of the protrusion by the impingement effects of the flow induced by the horseshoe vortices. In case of complex geometry, dimple-protrusion, the compound effects of the dimple and protrusion occurred. The protrusion case showed the highest heat transfer enhancement among test cases. However, pressure loss increased. For the performance factor, the dimpled case shows the highest performance factor among test cases of dimpled, protruded and dimple-protrusion due to the its low pressure drop increase.

HTE-24 pages DOI: 10.1615/IHTC13.p17.240 Download article

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