Measurement and prediction of the cooling characteristics of a generalized vibrating piezoelectric fan

Piezoelectric fans are thin elastic beams whose vibratory motion is actuated by means of a piezoelectric material bonded to the beam. These fans have found use as a means to enhance convective heat transfer while requiring only small amounts of power. The objective of the present work is to quantify the influence of each operational parameter and its relative impact on thermal performance. Of particular interest are the vibration frequency and amplitude as well as the geometry of the vibrating cantilever beam. The experimental setup consists of a piezoelectric fan mounted normal to a constant heat flux surface. Temperature contours on this surface captured via an infrared camera are used to extract the forced convection coefficient due to the fluid motion generated from the fan. Different fans, with fundamental resonance frequencies ranging from 60 to 250 Hz, are considered. Results show that the performance of the fans is maximized at a particular value of the gap between the fan tip and the heated surface. It is found that when a fan operates at this optimum gap, the heat transfer rate is dependent only on the frequency and amplitude of oscillation. Correlations based on appropriately defined dimensionless parameters are developed and found to successfully predict the thermal performance across the entire range of fan dimensions, vibration frequency and amplitude. An understanding of the dependence of thermal performance on the governing variables allows for improved design of piezoelectric fans as a method of enhancing heat transfer.