Numerical study of nozzle width effect on cooling performance of a turbulent impinging oscillating jet in a heated cavity

The paper presents a numerical study on an impingement cooling system which employs a self-excited oscillating air jet discharging into a confined space. The effect of nozzle width was examined on the flow structure and heat transfer at different inlet flow rates and impinging distances. The unsteady incompressible flow was solved by the finite volume based tool OpenFOAM code. The k-o (SST) model was selected to capture the turbulence effects. The results indicated that reducing the nozzle width increased the frequency of the oscillation at a constant flow rate. On the other hand, the Nusselt number at the impingement wall increased linearly by reducing the nozzle width. For the ratio of nozzle width to cavity width greater than 0.195, the oscillation of the flow completely vanished. In these cases, the self-excited oscillating impinging jet was converted into a conventional stationary impinging jet. The results showed that the value of the average Nusselt number of the conventional stationary jet was lower than that of the self-excited oscillating ones. Also, small variations in the impingement distance slightly changed the mean Nusselt number at small nozzle widths. The results suggest that the oscillation of the flow enhances the cooling performance of the system.