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%

Characterization and Optimization of the Thermal Performance of Miniature Piezoelectric Fans

Piezoelectric fans have emerged as a viable cooling technology for the thermal management of electronic devices, owing to their low- power consumption, minimal noise emission, and small and configurable dimensions. Piezoelectric fans are investigated for application in the cooling of low-power electronics. Different experimental configurations are considered, and the effect of varying the fan amplitude, the distance between the fan and the heat source, the fan length, its frequency offset from resonance, and the fan offset from the center of the heat source are studied to assess the cooling potential of the fans. A design of experiments (DOE) analysis revealed the fan frequency offset from resonance and the fan amplitude as the critical parameters. Transfer functions are obtained from the DOE analysis for the implementation of these fans in electronics cooling. For the best case, an enhancement in convective heat transfer coefficient exceeding 375% relative to natural convection was observed, resulting in a temperature drop at the heat source of more than 36.4 °C. A computational model for the flow field and heat transfer induced by the piezoelectric fan is also developed. Effects of the flow on convection heat transfer for different fan-to-heat source distances and boundary conditions are analyzed. Transition between distinct convection patterns is observed with changes in the parameters. The computational results are validated against experimental measurements, with good agreement

Experimental Investigation of the Thermal Performance of Piezoelectric Fans

Piezoelectric fans are investigated as a cooling technology for the thermal management of electronic devices. Flow visualization experiments are conducted to better understand the physics of fan operation. Prototypes of the fans are built and tested to assess their feasibility and cooling performance and determine optimal locations for the fans. An enclosure the size of a cellular phone and a commercially available laptop computer are used to demonstrate the cooling feasibility of the fans. Piezoelectric fans are found to offer significant localized cooling, exceeding enhancements in convective heat transfer coefficients of 100%, while exhibiting low power consumption, minimal noise, and small dimensions. Performance metrics for piezoelectric fans should be based on heat transfer characteristics, such as the percent increase in the heat transfer coefficient of the system. Optimization techniques that maximize the electromechanical coupling factor (EMCF) can be used to design efficient fans