Document Type : Full Lenght Research Article
Faculty of Mechanical Engineering
Faculty of Mechanical Engineering, Semnan University, Semnan, Iran
Faculty of Mechanical Engineering, Semnan University, Iran
The main purpose of the current work is the analysis of the pulsating effect on the flow and heat transfer from impinging jet on a concave surface. In this way, the heat flux of 2300 W/m2 has been applied constantly on the surface with the radius of 120mm. The intermittent jet has been created for the frequency range of 1-100Hz by the pulsed-jet generator. Nusselt number distribution and flow field have been investigated for dimensionless distance of nozzle to surface (H/d) 2 to 5 and Reynolds number from 7000 to13000. The comparison of the experimental data with Numerical simulation shows that the k-ε RNG turbulence model is appropriately capable of predicting the Nusselt number on the concave surface under the pulsed jet impinging. Results of the present research indicate that, pulsating the jet is more effective on the concave surface in comparison with a flat surface. Also as compared to steady jet, when pulsating applies to the inlet jet with low frequency, reduction in Nusselt number is acquired. Furthermore, at each Re number and H/d, a threshold Strouhal number is found above which the Nusselt number of the pulsed jet is greater than that of the steady jet. Moreover, for the low nozzle to surface distance, Nu of stagnation point at low and high frequency is varied with Sr0.05 and Sr 0.15, respectively. At Re=10000, pulsating the impinging jet with f =100Hz causes an increase in the time and area-averaged of Nusselt number by 22% and 20% in comparison to steady jet at H/d=5 and 2, respectively.