Y.T. Li

Study of multiple magnetic vibrating fins with a piezoelectric actuator

An innovative cooling technology, multiple magnetic vibrating fins system with only one piezoelectric actuator, is investigated for the thermal management in this study. The vibrating driving force is generated by a piezoelectric actuator and then transfer to multiple magnetic fins by the magnetic forces. The multiple magnetic vibrating fins system in this study uses only one piezoelectric actuator to drive ten fins to vibrate simultaneously which means that it not only decrease the cost but also distinctly increase the application value. In this study, the resonance frequency and the vibration amplitude of the multiple magnetic vibrating fins is investigated to optimize its thermal performance. Compare to traditional fixed fins, the experiment results show that the improved thermal performance of the vibrating fins cooling system (η) can be improved up to 34.7%, 38.5%, 37.4% and 25.9% under the pitch of vibrating fins of 6 mm, 8 mm, 10 mm, and 12 mm, respectively, with the power consumption of 0.2 W.

The novel modularized multiple fans system with a piezoelectric actuator

Previous studies proposed the multiple fans system with a piezoelectric actuator (MFPA), which combined the piezoelectric effect, magnetic effect and resonance effect to drive the passive fans vibrating simultaneously. In this study, the thermal performance of a modularized MFPA was investigated, in which the housing design was applied. Performance of the MFPA system (η) is defined to describe the improvement of the thermal performance. The results indicate that the geometry of the housing can significantly influence the thermal performance of the modularized MFPA. The results show that can be improved from 30.26 % to 37.55 % when dimensionless width number (Z*) and dimensionless length number (Y*) are decreased from 1.5 to 1.25 and from 0.92 to 0.42, separately. Moreover, in the investigation the nozzle angle (θ), the results indicate that η can be further improved to 46.61 % when θ is increased from 0 to 63.43 .

Thermal performance of multiple piezoelectric-magnetic fans

Previous studies introduced novel multiple piezoelectric-magnetic fans (“MPMF”) which can improve its thermal performance effectively with only one piezoelectric actuator. Moreover, the T-shaped fan design also can increase sweep area of fan to drive more air and improve its thermal performance. This study focuses on investigating the effect of fan pitch (P) and gap (G) between fan tip and heat sink. In order to analysis the improvement of thermal resistance, efficiency of MPMF system is defined as the improvement of thermal resistance compared with natural convection in this study. The results show that MPMF can reach the optimal efficiency of MPMF system of 73.53% while aspect ratio of fan pitch (P/L) is 0.23 and the ratio of gap between fan tip and heat sink (G/L) is 0.05. In addition, the cooling ability under different dummy heater power is explored. When dummy heater operates at 90W, the surface temperature of heater can be declined from 187.9°C to 77.3°C. Comparing with the thermal performance of rotary fan (0.25°C/W, 1.8W), thermal resistance of MPMF is 0.62°C/W with the power consumption of 0.15W, 6.7% of the rotary fan.

Development and Application of One-Sided Piezoelectric Actuating Micropump

Three types of one-sided actuating piezoelectric micropumps are studied in this paper. In the first type, one-sided actuating micropump with two check valves can enhance the flow rate and prevent the back flow in suction mode to keep the flow in one direction. Furthermore, the frequency modulator is applied in the micropump to adjust and promote the maximum flow rate higher than 5.0 mL/s. In the second type, valveless micropump with secondary chamber shows that the secondary chamber plays a key role in the application of the valveless micropump. It not only keeps the flow in one direction but also makes the flow rate of the pump reach 0.989 mL/s. In addition, when a nozzle/diffuser element is used in valveless micropump, the flow rate can be further improved to 1.183 mL/s at a frequency of 150 Hz. In the third type, piezoelectric actuating pump is regarded as an air pump in the application of a microfuel cell system, which can increase more air inlet to improve the fuel/air reaction and further increase the performance of fuel cell.