Effect of Pulse Frequency on Heat Transfer at the Stagnation Point of an Impinging Turbulent Jet

Heat transfer in an impact pulsed air jet is numerically studied using the Reynolds stress model. It is shown that both enhancement and suppression in the heat transfer are possible in an impinging pulsed jet as compared with a steady flow. The heat transfer intensifies with the pulse frequency at a stagnation point in the region of small distances between a pipe exit cross section and an obstacle (H/D >= 6), while an increase in the pulse frequency causes a decrease in the heat transfer for H/D > 8. An increase in the Reynolds number causes a deintensification of the heat transfer, and the data for all frequencies approach the single-phase flow mode. A comparison with available data by other authors is made, and satisfactory agreement is obtained with respect to the pulse frequency effect on the heat transfer between a gas jet and the impact surface.