Abstract:
An experimental and numerical study was performed to study the impingement heat transfer on the flat target surface produced by a pulsed-jet with an additional collection chamber. The current test was conducted under the following conditions, such as pulse frequency (f) ranged from 5 Hz to 40 Hz, jet Reynolds number (Re) ranged from 5 000 to 15 000, pulsation duty cycle (R) ranged from 0.2 to 0.8, jet-to-surface distance (H/d) ranged from 2 to 10. In the numerical simulations, the above parameter ranges were relatively extended, for example, 5 Hz≤f≤200 Hz, 5 000≤Re≤20 000 and 0.2≤R≤1.0. With respect to the pulsed-jet impingement without collection chamber, the pulsed-jet with an additional collection chamber was found to enhance the convective heat transfer, with a 8%-19% increase of the stagnation Nusselt number. Due to the additional collection chamber, the vena contracta effect near the jet orifice increased the approaching velocity towarded the target surface at the jet-on process. At the jet-off process the inertia role inside the additional collection chamber behaved. Among the current research conditions, the relatively optimal pulsation parameters such as f=80 Hz and R=0.8 were demonstrated. For the pulsed-jet impingement on a confined target, H/d=4 was a relatively optimal jet-to-surface distance.