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Journal of Enhanced Heat Transfer
IF: 0.562 5-Year IF: 0.605 SJR: 0.175 SNIP: 0.361 CiteScore™: 0.33

ISSN Print: 1065-5131
ISSN Online: 1026-5511

Journal of Enhanced Heat Transfer

DOI: 10.1615/JEnhHeatTransf.v6.i6.40
pages 429-439

Heat Transfer Enhancement in Rectangular Channels with Concavities

MinKing K. Chyu
Department of Mechanical Engineering and Materials Science University of Pittsburgh, Pittsburgh, PA 15261, USA
Y. Yu
Mechanical and Aerospace Engineering Department, Arizona State University, Tempe, USA
H. Ding
Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania

ABSTRACT

The present study evaluates an innovative approach for enhancement of surface heat transfer in a channel using concavities, rather than protruding elements. Serving as a vortex generator, a concavity is expected to promote turbulent mixing in the flow bulk and enhance the heat transfer. Using a transient liquid crystal imaging system, local heat transfer distributions on the surfaces of cavities roughened by staggered arrays of concavities have been obtained, analyzed, and compared. Two different shapes of concavities were evaluated, i.e., hemispheric and tear-drop shaped. The results reveal that both concavity configurations induce a heat transfer enhancement about 2.5 times their smooth wall counterparts for 10,000 < Re < 50,000. Such a level of enhancement is similar to that of typical rib turbulators with a pitch-to-height ratio around 10 and aligned normal to the bulk flow direction. In addition, both concavity arrays reveal remarkably low pressure losses that are nearly one-half the magnitudes incurred with the rib turbulators. In compact heat exchanger applications, the concavity approach is particularly attractive in reducing cooling system pressure losses and component weight.


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