Heat Transfer Analysis of a Novel Piezoelectric Air Pump

With the propagation of ever faster and more powerful electronics, the need for active, low power, cooling is becoming apparent. Piezoelectric materials exhibit reasonable performance with very little power consumption. Therefore a promising potential solution lies in utilizing piezoelectric materials via fans or pumps. However, piezoelectric pumps have mainly been employed in the transport of liquids and aqueous solutions through small microchannels. The structures typically consist of both an outlet nozzle and an inlet nozzle that are geometrically disposed to promote flow in one direction. Device construction is generally simplified compared to mechanically actuated openings, however much of the potential flow is lost due to backflow. The piezoelectric pump studied in this paper consists of a single outlet nozzle with a large inlet. Its unique construction allows it to overcome relatively high pressures as well as promoting better manufacturability. Experimental investigations were undertaken in order to characterize the cooling potential of the device. A thin film heater provided a constant heat flux and an infrared camera was used to determine the resulting temperatures of the heated surface. Full-field data of the convection coefficient were analyzed as a function of vibration amplitude of the piezoelectric diaphragm and distance from the nozzle to the heated target. A maximum heat transfer coefficient was found when the blower was approximately 30 mm from the heated surface and this distance was independent of vibration amplitude. Correlations have been developed which account for both variables considered and can be used to predict the performance of future designs which rely on the same physical characteristics.