Effect of intermittent and sinusoidal pulsed flows on impingement heat transfer from a concave surface

The effects of square waveform (intermittent) and sinusoidal waveform pulsation are investigated on the heat transfer rate from a slot jet impinging to a concave surface. In this respect, a numerical analysis of turbulent flow and heat transfer in a two-dimensional jet is performed using the RNG k-ɛ model. The effects of jet Reynolds number, pulsation frequency, nozzle to target surface spacing in both types of waves and the effect of the amplitude of sinusoidal waves on distribution of the surface time-averaged local Nusselt number are studied. Results show that in the pulsed jets, the increase of frequency in the range of 20-80 Hz and the Reynolds number in the range of 4740-7200 cause the increase of the time-averaged Nusselt number compared to steady jet cases. In the pulsed jets, reducing the nozzle-to-surface distance causes the increase of heat transfer from the target surface. Moreover, the increase of pulse amplitude from 0.2 to 1.0 in the sinusoidal waves increases the time-averaged Nusselt number. Finally, the comparison of results indicates a considerable increase of the heat transfer rate for the square form waves than sinusoidal waves compared to the steady state data.