Heat Transfer Enhancement of Vertical Heat Sinks with a Piezofan
This study examines several effects, including the piezofan positions, and piezofan arrangements, as well as piezofan height, on the heat transfer enhancement of two typical types of vertical heat sink. Either 30-mm-high or 10-mm-high heat sink having 11 plate-fins or 100 square pin-fins is tested with a running piezofan. The piezofan having Mylar blade is either vertically or horizontally placed above the heat sinks vibrating with resonant frequency of 31 Hz and tip mean-to-peak amplitude of 7.2 mm. The heat transfer coefficient is measured at five different fan locations with fan heights of 12 mm and 16 mm. Results show that the piezofan located at x/L = 0.5 usually performs the highest heat transfer enhancement for a given heat sink, while piezofan located at x/L = 1 usually shows the worst heat transfer enhancement. Depending on the fan arrangements and positions, heat transfer coefficient of the present 10-mm-high plate-fin heat sink shows 1.2 – 2.4 times higher than that under natural convection, while the enhancement factor ranges from 1.1 to 2.6 for 10-mm-high pin-fin heat sink.