NUMERICAL INVESTIGATIONS ON SYNTHETIC JET IMPINGEMENT COOLING USING MULTIPLE ORIFICE

Abstract

A synthetic jet generally consists of a cavity with a driver attached on one side and an orifice on the opposite side. When the driver moves back and forth, the jet will generate an unsteady flow through the orifice and the flow will move downstream to a surface forming an impinging flow. When the jet is in the ejection cycle, the diaphragm will expel flow out from the orifice and form a vortex near the orifice. If the propulsion is large enough, the vortex will move downstream before the jet orifice flow reverses and starts to suck in flow. The computational process is carried out using the commercial software ANSYS Fluent. In this study, the heat transfer characteristics of synthetic jet impingement cooling with multiple orifice (2,4 and 16 orifices) are analyse with different operating frequencies (f=1Hz to f=5Hz and f=100Hz to f=500Hz) with different Reynolds number (Re=5000,10000 and 20000) well as Strouhal number (St=0.006 to St=0.030). The results demonstrate that high frequency synthetic jets show better heat removal capacity than lower frequency at the same Reynolds number. Also, the variation of area averaged Nusselt number depends on Strouhal number or dimensionless stroke length.