An experimental and numerical study on heat transfer enhancement of a heat sink fin by synthetic jet impingement

Compared to traditional continuous jets, synthetic jets (jets with oscillatory flow such that the time-average velocity is zero) have specific advantages, such as lower power requirement, simpler structure and the ability to produce an unsteady turbulent flow that is known to be effective in augmenting heat transfer. This study presents experimental and computational results that document heat transfer coefficients associated with impinging a synthetic jet flow onto the tip region of a longitudinal fin used in an electronics cooling system. The effects of different parameters, such as amplitude and frequency of diaphragm movement and jet-to-cooled-surface spacing, are recorded. The computational results show a good match with experimental results. In the experiments, an actual-scale (1 mm jet orifice) system is introduced and, for finer spatial resolution and improved control over geometric and operational conditions, a large-scale mock-up (44 mm jet orifice) is applied in a dynamically-similar way, then tested. Results of the experiments at the two scales, combined with the computational results, describe fin heat transfer coefficients on and near the jet impingement stagnation point. A linear relationship for heat transfer coefficient versus frequency of diaphragm movement is shown. Heat transfer coefficient values as high as 650 W/m2K are obtained with high-frequency diaphragm movement. Cases with different orifice shapes show how jet impingement cooling performance changes with orifice shape.