Convective heat transfer on a flat target surface impinged by pulsating jet with an additional transmission chamber

A series of experimental tests are performed for the pulsating jet impingement heat transfer by varying the Reynolds number (5000 <= Re <= 15000), operation frequency (5 Hz <= f <= 40 Hz) and dimensionless nozzle-to-surface distance (2 <= H/d <= 10) while fixing the duty cycle as DC = 0.5. The maximum uncertainty in the measurement of Nusselt number is estimated to be about +/- 7%. Meanwhile, numerical simulations are performed to demonstrate the instantaneous flow field of the pulsating jet impingement. Particular attention is paid to examine the influence of transmission chamber on the pulsating jet impingement heat transfer. The results show that by using an additional transmission chamber, the pulsating jet impingement heat transfer is enhanced. For example, the circumferentially-averaged Nusselt number around the stagnation point (x/d <= 2) is increased up 8%similar to 16% by the adding of a transmission chamber in related to the baseline case under Re = 10000 and H/d = 6. Due to the presence of transmission chamber, the exiting jet velocity profile at the orifice outlet is varied. In related to the baseline case, the transmission chamber makes the time-averaged ejecting velocity in the central zone increase but decrease in the edge zone. As the peak velocity in the central zone of orifice outlet is effectively increased by the use of transmission chamber, the jet impinging velocity approaching to the target surface is also strengthened, resulting in a stronger jet impingement in the vicinity of the stagnation point.