Heat Transfer Characteristics Of A Pair Of Impinging Synthetic Jets: Effect Of Orifice Spacing And Impingement Distance

Recent research has shown that an impinging synthetic jet attains local heat transfer rates that rival those of a steady impinging jet. A single synthetic jet still requires a buoyancy-driven or forced cross flow to avoid recirculation of heated fluid. However, multiple adjacent synthetic jets exhibit a fluidic interaction that results in flow vectoring towards the direction of the jet leading in phase. Previous results have shown a significant heat transfer enhancement and the establishment of a jet-induced cross-flow, which could eliminate the need for an external forced cross-flow. This paper presents the findings of an experimental study to optimize the orifice-to-impingement distance H and orifice centre-to-centre separation distance S. The convective heat transfer rate is determined on an electrically heated metal foil using thermal imaging. The jets are driven by a pair of adjacent jet actuators forcing air through two rectangular slot orifices of width D = 1.65mm and aspect ratio alpha = 27:1. The jets are maintained at a constant Reynolds number and stroke length (Re = 600, L-0/D = 29). For the parameter range considered, an optimum setting of H/D = 24 and S/D = 3 operated within a phase difference region of 60 degrees < Phi < 120 degrees gives the best cooling performance.