Experimental investigation on time-averaged heat transfer characteristics of a row of pulsating jets

Abstract

The heat transfer characteristics of a row of pulsating jets feeding by a cooling tube have been investigated for an active clearance control system. Experimental tests were performed to explore the effects of the frequency (rectangular signal, 5–30 Hz), Reynolds number (6000–20,000), jet-to-surface spacing ratio (6–10), and jet-to-jet spacing ratio (3–9) on the Nusselt number of the pulsating jets and the relative enhancement coefficient compared with the steady jets. Results show that the streamwise-averaged Nusselt number of the pulsating jets increases with the increase of frequency (5–25 Hz) and Re. Its distribution along the X/d is gentler with the increase of H/d and S/d. Heat transfer correlations are developed and two associated parameters SrRe0.911(H/S)0.348 and SrRe(H/d)0.540(S/d)-0.248 are obtained to effectively scale the enhancements. Maximum enhancements for the stagnation region and wall jet region are 29.3% and 26.8%, respectively. The heat transfer on the overall surface can be strengthened in a wider range of conditions compared with the stagnation region, which contributes to the heat transfer uniformity in certain conditions.