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LES Investigation of Flow and Heat Transfer in a Channel With Dimples and Protrusions

[+] Author Affiliations
Mohammad A. Elyyan, Danesh K. Tafti

Virginia Polytechnic Institute and State University, Blacksburg, VA

Paper No. GT2007-27811, pp. 609-621; 13 pages
doi:10.1115/GT2007-27811
From:
  • ASME Turbo Expo 2007: Power for Land, Sea, and Air
  • Volume 4: Turbo Expo 2007, Parts A and B
  • Montreal, Canada, May 14–17, 2007
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 0-7918-4793-4 | eISBN: 0-7918-3796-3
  • Copyright © 2007 by ASME

abstract

LES calculations are conducted for flow in a channel with dimples and protrusions on opposite walls with both surfaces heated at three Reynolds numbers, ReH = 220, 940, and 9300 ranging from laminar, weakly turbulent to fully turbulent, respectively. Turbulence generated by the separated shear layer in the dimple and along the downstream rim of the dimple is primarily responsible for heat transfer augmentation on the dimple surface. On the other hand, augmentation on the protrusion surface is mostly driven by flow impingement and flow acceleration between protrusions, while the turbulence generated in the wake has a secondary effect. Heat transfer augmentation ratios of 0.99 at ReH = 220, 2.9 at ReH = 940, and 2.5 at ReH = 9300 are obtained. Both skin friction and form losses contribute to pressure drop in the channel, with form losses increasing from 45% to 80% with an increase in the Reynolds number. Friction coefficient augmentation ratios of 1.67, 4.82 and 6.37 are obtained at ReH = 220, 940, and 9300, respectively. Based on the geometry studied, it is found that dimples and protrusions may not be viable heat transfer augmentation surfaces when the flow is steady and laminar.

Copyright © 2007 by ASME

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