Investigation of the effects of optimum nozzle type on the impinging jest

In this thesis, an experimental work is performed in order to determine optimum nozzletype in impinging jets. As nozzle type, circular nozzles with various diameters and coaxialnozzles are used. The circular nozzles are the circular aluminum pipes having 7.9, 10.8, 13.8and 23.1 mm inner diameter value. And as the co-axial jet; outer of the jet there is a pipe of 13.8mm inner diameter, and the pipes which have 9.8, 8 and 6.2 mm are located through thecenterline of this principal pipe. The gained heat transfer, after each of these 7 different nozzleshad been impinged to a heated flat plate, and calculated in the term of dimensionless Nusseltnumber. The impingement plate is the front side of a channel, in which water vapor is passed.Hence, a constant temperature boundary condition is supplied.The flow characteristic of these jets (mean flow and turbulent intensity) withoutimpinging, namely free jet, is obtained by a highly sensitive hot-wire anemometer. And also themean flow and turbulent intensity on near field of impingement plate is obtained while only thecircular jet flow is impinging on the target plate (four circular nozzles are used, not the co axialones). Both the velocities and temperatures are measured and recorded by a computer aided datalogger device.Not only the uncertainty analysis of the measured data is performed, but also theempirical correlations are obtained by the help of statistical regression analysis. And finally, thefounded correlations are compared to literature, and the validity of them is discussed.At the result it has been seen that, the diameter of the nozzle is an important parameterat the cooling pheromone of impinging jets. For all nozzle types, at the same Re value, due tochanging the diameter of the nozzle would cause an effect on velocity and turbulent intensity,the cooling characteristic was affected. Especially it is difficult to make accurate measurementson the heated plate subjected to a co-axial jet flow; there hasn?t been more detailed paper in theliterature. Hence, the results of this work will assist to fill this cavity. In this work it has beenseen that, the velocity ratio of co-axial flow has a great important effect on cooling.Key Words: impinging jet, co axial jet, circular or round jet, heat transfer, flow dynamics