Jet-Spacing Effect on Impinged Heat Transfer in a Triangular Duct with a Tengential Jet-Array
Jenn-Jiang Hwang, Nai-Chien Shih, Chung-Shen Cheng, Kuan-Tsen Shih and Yeon-Pei Tsai
Impinged heat transfer characteristics in a leading-edge triangular duct by an array of wall jets are studied experimentally. Coolant provided by an array of equally spaced wall jets is aimed at the leading-edge apex and exits from the radial outlet. A transient liquid crystal technique is utilized to measure the detailed heat transfer coefficients on the two principal walls forming the apex. Secondary-flow structures are visualized to realize the mechanism of heat transfer enhancement by wall/impinged jets. The effects of jet Reynolds numbers (3000 &Mac178; Rej &Mac178; 12600) and jet spacings (1.5&Mac178; s/d &Mac178; 6.0) are examined. Results show that an increase in Rej increases the heat transfer on the both walls. Local heat transfer on the both walls gradually decreases downstream due to the crossflow effect. Of the same Rej, decreasing the jet spacing increases the heat transfer coefficient. Of the same duct through flow rate, however, reducing the jet spacing reduces the heat transfer enhancement near the leading-edge apex.