Impact of orifice jet configuration on heat transfer in a channel with inclined target surface cooled by single array of impinging jets with outflow opposing the entry flow

An experimental investigation has been carried out to study the effect of origice-jet plate configuration on heat transfer characteristics in a channel with inclined heated target plate cooled by single array of equally spaced impinging jets. Air ejected from an array of orifices is aimed at the heated target surface and exits from the radial outlets. The target plate forms the leading edge of a gas turbine blade. The study covers the effect of various orifice-jet plate configurations, feed channel aspect ratios (5 ≤ H/d ≤ 9) and Reynolds number (9300 ≤ Re ≤ 18800) on the heat transfer characteristics for a given outflow orientation (outflow direction opposing the entry flow). Three orifice-jet plate configurations (centered, staggered, and tangential holes) have been examined. In general, it has been noticed that Nusselt number (Nu) is high for higher aspect ratios. For a given plate-1 with single array of equally spaced centered jets and for Re=18800 (outflow opposing the entry flow), the local Nu for H/d=9 has been found to be greater than Nu of H/d=7 by 5%. This increase can be attributed to increase in strength of impinging jets due to increase in feed channel aspect ratio. It has also been noticed that plate-1 with centered orifice-jet configuration gives better heat transfer characteristics relatively as compared to other orifice-jet configurations. The percentage increase in average Nu has been found to be about 19% with centered holes as compared staggered orifice-jet plate. The percentage increase in average Nu has been found to be about 4% with staggered jet-plate as compared to tangential orifice-jet plate configuration.