Application of multiple fans with a piezoelectric actuator system inside a pico projector

Numerous studies have shown that multiple fans with a piezoelectric actuator (MFPA) system can provide better cooling ability than a single piezoelectric fan with low power consumption and low noise. In this study, five MFPA models were designed and developed to be applied inside a pico projector, and the resonant frequency, the vibrational amplitude and the power consumption of these models were measured. Moreover, the Nusselt number, Richardson number, and thermal resistance were used to evaluate the thermal performance of the MFPA. The results reveal that the MFPA model with a combination of 35-mm long carbon fiber plates and 5-mm long Mylar plates achieves the optimal thermal performance. The thermal resistance, Nusselt number, and Richardson number of the MFPA model were, respectively, 4.13 K/W, 81.25, and 0.018 under 8-W heater power. Further experiments were performed with the optimal model set in different orientations. The results show that the Nusselt number dropped from 81.25 to 59.10 when the orientation changed from the normal case to the upside-down case at 8-W heater power.