Effect of temperature difference and radial distance of single nozzle pulsed air jet on heat transfer enhancement

Pulsed air jet is a very interesting new research area due to its contribution towards heat and mass transfer enhancement and has a potential for future industrial application. It has been proven that pulsed air jet has better heat transfer performance compared with steady air jet system for certain flow geometry under certain conditions only. The objective of this paper is to study the effect of temperature difference and flow pulsation on the heat transfer performance of a single nozzle pulsed jet impingement system. In this study, three Reynolds number (Nu) (5500, 11000, and 16000) have been chosen to represent the turbulent air flow onto a copper impingement plate with a nozzle outlet diameter of 20 mm. Temperature difference (ΔT) of 0, 25, 50, 75, and 90°C have been used to study the effect of temperature difference. Measurement were taken at different radial distance to nozzle outlet diameter ratio (r/d), different pulse frequencies of 20 Hz and 40 Hz and at a fixed plate to nozzle distance ratio (z/d) of 4. It´s found that Nusselt number (Nu) increases as the Reynolds number increases and Nusselt number (Nu) decreases as ΔT decreases. At Reynolds number of 16000, r/d of 0 and ΔT of 0, highest Nusselt number of 45.42 has been obtained.