An experimental investigation of heat transfer characteritics of a normal and oblique air jet impining on heated flat plate

SUMMARY AN EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER CHARECTERISTICS OF A NORMAL AND OBLIQUE AIR JET IMPINGING ON HEATED FLAT PLATE The high speed air jets are widely used in the paper and glass production industries, metals annealing, and coooling of electrical and electronic equipments. In this study, depending on some parameters, the heat transfer charecteristics of a normal and an oblique circular fully devoloped air jet impinging on heated flat plate have been experimentally. In the experiments, the ranges of parameters were taken between 10 000- 40 000 for Reynolds numbers, 6-14 H/D which is the ratio of distance between plate and lüle exit to lüle diameter, and 45-90 degrees for jet inclination angle. Lüle diameter was kept constant to be 15 mm. The temperature variation on the flat plate during the jet impingement were measured by using the calibrated liquid crystal. It was found that maximum heat transfer accured out of the potantial core, approximately at the distance of eight jet diameters length from the lüle exit. At the stagnation point, it was observed that the heat transfer coefficient decreases with decreasing jet inclination angle. For the 45 der. jet inclination angle, the stagnation heat transfer coefficient for H/D=7,10,14 reduced respectively %6, %18, %22 compared with that of normal impinging jet. Results experimentally determined from this study are good in agreement with the data given in the literature for the normal impingement. Key Words: Jet impingement, Obliquely jet impingement, Jet impingement cooling, Jet convective heat transfer, Stagnation point heat transfer. VII