Search

In this study, the transient and steady-state heat transfer caused by an air jet impinging on a heated plate moving back and forth in the horizontal direction is investigated experimentally. The jet flow issuing form nozzle of various geometry (circular, triangle, square) is impinged on rough and smooth surfaces. In addition, Reynolds number (jet velocity), distance between the nozzle and the plate, plate velocity and stroke are considered as independent parameters that could affect the heat transfer.The optimum number of experiments is determined with the help of Taguchi design of experiment method. The transient and steady-state heat transfer are analyzed by means a high-technology thermal camera. Local and average Nusselt numbers representing the heat transfer characteristics are calculated in response to the variable parameters. Comparative graphs and ANOVA test results are presented and evaluated in order to determine the effects of parameters on heat transfer. As a result, it has been seen that Reynolds number (82%) is the most dominant parameter affecting heat transfer. Other parameters are listed as nozzle geometry (7.6%), surface roughness (4.9%), plate velocity (1%), stroke (0.6%) and nozzle-plate distance (0.1%) according to their degree of effect. [ABSTRACT FROM AUTHOR]

Abstract The main focus of this work is a synergistic heat transfer analysis of the impinging multi jets. The geometry of the jet holes, arrangement of those holes, density of the jets through spanwise and streamwise directions and type of the confinement are the design parameters that affect the impingement characteristics. The numerical analysis is run by using commercial software ANSYS-CFX that uses computational fluid dynamics (CFD) codes. The average Nusselt number is extracted as the heat transfer result. It is concluded that, the heat transfer distribution under the densest-array jet impingement inside the one-exit-confined channel is behaved as the single jet because of the strong adjacent jet interference. The highest jet impingement heat transfer is achieved for the case using square jets. The effect of jet arrangement seems to be the weakest parameter on the heat transfer. [ABSTRACT FROM AUTHOR]

In current study design analysis of a specified impingement jet application is performed by use of Taguchi method. Some results from a previously done experimental study that includes the impingement of co-axial and single circular jets to the both roughened and smooth heated surfaces are handled. By use of Taguchi method, some results are obtained to show the effect of Reynolds numbers ( Re = 20,000 and 40,000), non-dimensional surface to jet exit spacing ( H/ D = 2, 6, 8 and 10), surface roughness (rough or smooth surface) and jet type (co-axial or circular). Finally, the effects of Reynolds number, surface roughness, jet-to-plate spacing and jet type on impingement heat transfer, by means of average Nusselt number, are found to be respectively, 83, 2, 4.5 and 10.7%. [ABSTRACT FROM AUTHOR]