FULL FIELD THERMAL PERFORMANCE OF A SIDE MOUNTED PIEZOELECTRIC FAN
Piezoelectric fans are a potential low power thermal management solution for handheld and low profile electronic devices. Their design is simple and adaptable, enables noiseless operation, and makes use of resonance conditions which allow for a highly energy efficient cooling device. It has been shown that piezoelectric fans oscillating at their resonance frequency have the capability to significantly increase heat transfer over natural convection, but many of the fundamental studies have focused on an impingement orientation, one where the fan is positioned normal to the heated surface. This requires a significant amount of space to implement, and hence precludes many low profile applications, where volume usage must be as efficient as possible. In this study, the full field heat transfer coefficients maps are experimentally found for a piezoelectric fan oscillating parallel to the heated surface using infrared thermography. The effect of the distance between the fan blade and heater is explored by considering three different values for gap: 1 mm, 3 mm, and 5 mm. For these experiments, the oscillation amplitude is held
constant at 10 mm. Results show that these small changes in gap can have a large impact on the heat transfer
coefficient distributions. A gap of 1 mm yields the largest impact zone for thermal enhancement over natural
convection, and produces wing-like contours. For the largest gap considered (5 mm), the impact zone become
more localized near the fan tip and provides peak heat transfer performance higher than the 1 mm gap. At the
intermediate gap, the contours are qualitatively similar to the 5 mm gap results, but with an improvement in heat
transfer coefficient. Optimal performance is dependent on the intended target size of the heat source. The full field convection coefficient maps are analyzed in detail to produce optimization approaches for the design engineer. This includes gap and placement of the vibrating fan with respect to the heated target.