Thermal and fluidic characterization of piezoelectric fans

The objective of this work is the thermal and fluidic characterization of piezoelectric fans for their implementation in cooling solutions. The two most remarkable characteristics of piezoelectric fans are their low noise levels and their low power consumption. These features render piezoelectric fans well-suited to applications in the thermal management of portable electronic devices. Feasibility studies conducted on piezoelectric fans have demonstrated the viability of using these devices in electronics cooling applications. However, these studies did not attempt a detailed characterization of the piezoelectric fans to an extent which would lead to their optimal integration into cooling solutions. The cooling performance of these fans are experimentally characterized in detail in this work. Transfer functions are presented for three different practical orientations of the fan and heat source. Different tip shapes for piezoelectric fans have been evaluated. It is found that modifying the tip of a straight piezoelectric fan actually reduced its cooling performance for the three different shapes considered. Experimentally it is shown that for the same cooling performance axial fans consumed approximately 10 times more power than piezoelectric actuators. A two-dimensional numerical model is also developed and validated with experimental measurements. The numerical model is used to develop fan curves for the piezoelectric fans, using a methodology similar to that used in constructing pump or fan curves for conventional fans. A simplified model based on stagnation region heat transfer in impingement flows is also proposed to estimate the heat transfer from a piezoelectric fan. The velocities obtained from the piezoelectric fan curves generated are used in this impingement heat transfer model, and the predictions are found to agree with measured stagnation zone Nusselt numbers with an average deviation of 22%