Impingement cooling in triangular ducts using an array of side-entry wall jets

An experimental study has been performed to measure local heat transfer coe fficients and static wall pressure drops in leading-edge triangular ducts c ooled by wall/impinged jets. Coolant provided by an array of equally spaced wall jets is aimed at the leading-edge apex and exits from the radial outl et. Detailed heat transfer coefficients are measured for the two walls form ing the apex using transient liquid crystal technique. Secondary-flow struc tures are visualized to realize the mechanism of heat transfer enhancement by wall/impinged jets. Three right triangular ducts of the same altitude an d different apex angles of beta = 30 degrees (Duct A), 45 degrees (Duct B) and 60 degrees (Duct C) are tested for various jet Reynolds numbers (3000 l ess than or equal to Re-j less than or equal to 12 600) and jet spacing (s/ d = 3.0 and 6.0). Results show that an increase in Re-j increases the heat transfer on both walls. Local heat transfer on both walls gradually decreas es downstream due to the crossflow effect. At the same Re-j, Duct C has the highest wall-averaged heat transfer rate because of the highest jet center velocity as well as the smallest jet inclined angle. The distribution of s tatic pressure drop based on the local through flow rate in the present tri angular duct is similar to that of developing straight pipe Rows. Average j et Nusselt numbers on the both walls have been correlated with jet Reynolds number for three different duct shapes. (C) 2001 Elsevier Science Ltd. All rights reserved.