A numerical study of heat transfer in a turbulent pulsating impinging jet

Pulsating impinging jets can have significant influence on transfer processes. A number of studies have been done on heat transfer in a pulsating impinging jet but very divergent and sometimes contradictory results have been reported. In the present study, the flow and temperature field under a single confined pulsating turbulent impinging jet are determined numerically by the finite volume method. Effects of Pulsation function parameters (frequency and amplitude) and various geometries on the flow characteristics and heat transfer rate from hot surface are discussed. Results of simulation show that flow pulsation has different effects in various flow zones. Pulsation of jet improve cooling performance in the wall jet zone and simultaneously reduce heat transfer in the stagnation zone. As expected the effect of flow pulsation decays with distance from the jet nozzle. Under certain conditions flow oscillation adversely affects the heat transfer in comparison with the steady jet at the same mean Reynolds number. In pulsating jets we can introduce a critical frequency correspond to St = 0.26. The amount of heat transfer at the frequencies corresponding St = 0.26 is higher than other cases. In general, it is concluded that cooling performance of oscillating impinging jet is enhanced by increase in the frequency and amplitude of oscillation as well as decrease in nozzle to plate distance.