Experimental results, measured on dimpled test surfaces placed on one wall of different rectangular channels, are given for a ratio of air inlet stagnation temperature to surface temperature of approximately 0.94, and Reynolds numbers based on channel height from 9940 to 74,800. The data presented include friction factors, local Nusselt numbers, spatially averaged Nusselt numbers, and globally averaged Nusselt numbers. The ratios of dimple depth to dimple print diameter are 0.1, 0.2, and 0.3 to provide information on the influences of dimple depth. The ratio of channel height to dimple print diameter is 1.00. At all Reynolds numbers considered, local spatially resolved and spatially averaged Nusselt number augmentations increase as dimple depth increases (and all other experimental and geometric parameters are held approximately constant). These are attributed to (i) increases in the strengths and intensity of vortices and associated secondary flows ejected from the dimples, as well as (ii) increases in the magnitudes of three-dimensional turbulence production and turbulence transport. The effects of these phenomena are especially apparent in local Nusselt number ratio distributions measured just inside of the dimples and just downstream of the downstream edges of the dimples. Data are also presented to illustrate the effects of Reynolds number and streamwise development for dimples. Significant local Nusselt number ratio variations are observed at different streamwise locations, whereas variations with the Reynolds number are mostly apparent on flat surfaces just downstream of individual dimples.
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Effects Of Dimple Depth on Channel Nusselt Numbers and Friction Factors
N. K. Burgess,
N. K. Burgess
Convective Heat Transfer Laboratory, Department of Mechanical Engineering,
University of Utah
, 50 S. Central Campus Drive, Salt Lake City, UT 84112-9208
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P. M. Ligrani
P. M. Ligrani
Convective Heat Transfer Laboratory, Department of Mechanical Engineering,
University of Utah
, 50 S. Central Campus Drive, Salt Lake City, UT 84112-9208
Search for other works by this author on:
N. K. Burgess
Convective Heat Transfer Laboratory, Department of Mechanical Engineering,
University of Utah
, 50 S. Central Campus Drive, Salt Lake City, UT 84112-9208
P. M. Ligrani
Convective Heat Transfer Laboratory, Department of Mechanical Engineering,
University of Utah
, 50 S. Central Campus Drive, Salt Lake City, UT 84112-9208J. Heat Transfer. Aug 2005, 127(8): 839-847 (9 pages)
Published Online: October 6, 2004
Article history
Received:
December 1, 2003
Revised:
October 6, 2004
Citation
Burgess, N. K., and Ligrani, P. M. (October 6, 2004). "Effects Of Dimple Depth on Channel Nusselt Numbers and Friction Factors." ASME. J. Heat Transfer. August 2005; 127(8): 839–847. https://doi.org/10.1115/1.1994880
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