Heat Transfer in the Impinging Synthetic Jet Cooling: Frequency and Jet-to-Surface Effects

The synthetic jet is a jet with zero net mass flux usually produced by oscillating a diaphragm placed on a cavity. The cooling performance of the impingement synthetic jet is investigated numerically in a scaled up model that enables high resolution thermal and flow measurements. The test setup comprises of two circular parallel plates where one plate contains an integrated jet actuator and the opposite plate includes a constant heat flux of 18 W. Effects of jet formation frequency at the orifice outlet and jet-to-surface distances (H/d) at constant Reynolds number are investigated. The cavity and diaphragm are omitted and a harmonic time-dependent velocity profile is assumed at the orifice outlet. Also, the 2vf− turbulence model is applied as a suitable model for problems with stagnation points. Solution of the governing equations under the assumptions of incompressible, axisymmetric and temperaturedependent properties is carried out. The PISO algorithm is employed for the coupling of continuity and momentum equations. Results show that the Nusselt number increases as jet to surface distance raises. However, this increase does not continue for all the quantities. Also, for small distances between the synthetic jet and the heated surface, the high formation frequency synthetic jet removes heat better than the low frequency jet, whereas the low frequency jet is more effective at larger distances.