JP Journal of Heat and Mass Transfer
Volume 13, Issue 2, Pages 193 - 227
(May 2016) http://dx.doi.org/10.17654/HM013020193 |
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IMPINGEMENT ARRAY HEAT TRANSFER WITH LARGE HOLE SPACING
Zhong Ren, Junsik Lee, Phil Ligrani, Dae Hee Lee, Michael D. Fox and Hee-Koo Moon
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Abstract: Data are presented which illustrate surface heat transfer characteristics of an array of impinging jets with large hole spacing on a flat plate. Included is consideration of the effects of jet-to-target plate distance, and jet Reynolds number. Steamwise and spanwise hole spacing is 12D. Jet-to-target plate distances Zof 1.5D, 3.0D, 5.0D, and 8.0Dare employed, where Dis the impingement hole diameter. Reynolds numbers range from 8,000 to 50,000, with isentropic jet Mach numbers of approximately 0.1 to 0.2. Experimental results include local, line-averaged, and spatially-averaged Nusselt number distributions. These different types of Nusselt numbers increase strongly with impingement jet Reynolds number for all situations examined. This dependence of spatially-averaged Nusselt number is quantified using a correlation for the two most upstream rows of impingement jets (at the smallest values), where cross-flows and jet interactions are minimal. The highest local Nusselt numbers are generally present for for of 20,000, 30,000, and 50,000, with local Nu number decreases as increases further. For of 8,000, the highest Nusselt number values are generally present for In general, using the influences of surrounding jets, including cumulative-induced cross-flows and interactions of jet-induced vortex structures, are less pronounced, relative to configuration with smaller hole spacing. With the present large hole spacing, both local and line-averaged maximum Nusselt number data trends show only very small variations with increasing As such, important differences relative to impingement arrays with smaller hole spacing are evident, especially in regard to Nusselt number variations as streamwise location, jet-to-target plate distance, and Reynolds number are changed. |
Keywords and phrases: impinging jet, impingement jet array cooling, jet-to-target plate distance, Nusselt number, jet hole spacing, heat transfer augmentation. |
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