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ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Enhancement of the Heat Transfer from Flat Surface to Impinging Round Jet Using Concentric Trip Arrays

Get access (open in a dialog) DOI: 10.1615/IHTC12.2980
6 pages

Resumo

The effect that flow trips have on the heat transfer produced by round impinging jets with nozzle-to-plate distances ranging from 2 to 6 diameters was examined for four different trip arrangements. The heat transfer enhancement caused by the trips was largest for a nozzle-to-plate distance of 2 diameters. In this case the largest heat transfer enhancement was produced by a single trip at r/D = 0:5. The local Nusselt number downstream of the trip was increased by over 50% and the average Nusselt number for the areas with radii from 1.0 < r/D < 1.5 was increased by 20%. The results suggest that the optimal location of the trip may depend on the area being cooled by the jet. It was found that the heat transfer enhancement was reduced by adding trips downstream of the first trip.
The heat transfer enhancement produced by the trips was smaller for larger nozzle-to-plate separation distances of 4 and 6 diameters though the average Nusselt number could be increased by up to 10%. The optimal trip geometry again depended on the area being cooled by the jet. In these cases the downstream trips caused a local heat transfer enhancement when the distance between the trips was 10 trips heights as expected. The results suggest that a significant portion of the heat transfer enhancement for the nozzle-to-plate spacing of 2 diameters occur because the trip caused the large-scale ring structures to separate from the plate while for the larger separation distances the turbulent produced by the trip plays a more important role.