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Uses of impinging jet devices for heat transfer

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To better understand and facilitate design of an impinging jet device, the heat transfer on a cylindrical target exposed to radial impinging slot jets was investigated using numerical methods. Numerical models were created to test the performance of the shear stress transport, standard and realizable k-", v 2 f , and Reynolds stress model turbulence models vs published test data. Based on the validation study, the v 2 f model was ultimately selected for further work. Models were then constructed to simulate a cylinder exposed to a radial array of slot jets. Parametric variations were conducted to produce information about the influence of jet speed, number of nozzles, and other independent design variables, upon heat transfer. The number of nozzles was varied from 2 to 8, jet Reynolds number Re from 5,000 to 80,000, and target diameter from 5 to 10 times the nozzle hydraulic diameter. The physics of the flows are discussed, finding, for example, that interaction of adjacent opposed wall jets caused a static pressure rise and resulted in flow separation on the surface of the cylindrical target. This separation and the fountain flow between the two wall jets greatly influenced the local heat transfer, causing a rise in Nusselt number Nu of an order of magnitude. The resulting average Nu values varied from 19 to 217 and were condensed into a correlation equation incorporating the ratio of nozzle width to target diameter, number of nozzles, Reynolds number, and Prandtl number.

To better understand and facilitate design of an impinging jet device, the heat transfer on a cylindrical target exposed to radial impinging slot jets was investigated using numerical methods. Numerical models were created to test the performance of the Shear Stress Transport (SST), Standard and Realizable k-epsilon, v2f, and Reynolds Stress Model (RSM) turbulence models versus published test data. Based on the validation study the v2f model was ultimately selected for further work. Models were then constructed to simulate a cylinder exposed to a radial array of slot jets. Parametric variations were conducted to produce information about the influence of jet speed, nozzle count, and other independent design variables upon heat transfer. Nozzle count was varied from 2 to 8, jet Reynolds number ranged from 5,000 to 80,000, and target diameter varied from 5 to 10 times the nozzle hydraulic diameter. The interaction of adjacent opposed wall jets caused a static pressure rise and resulted in flow separation on the surface of the cylindrical target. This separation and the fountain flow between the two wall jets greatly influenced the local heat transfer, causing a rise in Nu of an order of magnitude. The resulting average Nu values varied from 19 to 217 and were condensed into a correlation equation incorporating target curvature, number of nozzles, Re, and Pr.