Abstract:
The numerical simulation investigation is performed to evaluate qualitatively the effect of the duty cycle to heat transfer enhancement of the multi-nozzles impinging jet using RNG
k-
ε model combined with the wall function. Simulations are carried out with different duty cycles, phase differences and frequencies. The numerical results indicate that unsteady impingement jets heat transfer performance is lower than the steady impinging jets in the case of double slot impingement jets under the condition of the same Reynolds number and the phase difference
θ of 0°, because the stronger unsteady impinging jet disturbance between adjacent nozzle jet than that of steady case. Compared to heat transfer characteristics of the steady jet, the phase difference of adjacent two nozzles staggers the velocity. When the stagger of velocity has no interactions or mutual influence is small, heat transfer enhancement achieves the best effect. Heat transfer performance with duty cycle of 0.5 is worse above the threshold frequency of 50Hz, while the effect of jet frequency on the heat transfer with a duty cycle of 0.25 is less than the former within the frequency of 0~100Hz.