EXPERIMENTAL STUDY ON THE HEAT TRANSFER UNDER IMPINGING JET ARRAY USING LIQUID CRYSTAL THERMOGRAPH

In this work, the effects of jet geometry and the arrangement of film holes on the target plate on the impinging heat transfer are experimentally investigated in detail. A liquid crystal thermograph technology is employed in this study. The aspect ratios (AR) of elliptical jet with five different values, 4, 2, 1, 0.5, and 0.25, jet Reynolds number ranging from 2000 to 4000, and jet-to-target spacing ranging from 1.5 to 4.5 are considered to investigate impingement heat transfer performance. In addition, three arrangements of film hole on the target plates, named side-, middle- and staggered-types, are tested, respectively. The experimental results show that the Nu increases with the increase of jet Reynolds number. Better heat transfer is noted for the cases with smaller jet-to-plate spacing. For the effect of the arrangement of pores on the target surface, the heat transfer on middle-type plate is more significant than the other two for smaller jet-to-plate spacing. As for the effect of aspect ratio, results indicate that the optimal heat transfer performance is found with circular jet of AR=1.