Yide WangNavid Dehdari EbrahimiAdvisor: Y. Sungtaek Ju

Department of Mechanical and Aerospace EngineeringUniversity of California, Los Angeles

Power Efficiency of Piezoelectric Fan

Overview

• Background

• Introduction to working principles and previous studies

• Experimental setups, devices and techniques

• Experimentally Investigating power efficiency of piezoelectric fan cooling with different configurations.

1. Different blade thickness2. Different blade length

• Conclusion

• Ongoing and Future work

Background

• Applied alternating electric field on top and bottom PZT (lead zirconate titanate) layers induces alternating and opposite deformation.

• Opposite deformation creates bending moment, causing vibration.

• Vibrating at fan blade’s resonance frequency to induce maximum air flow.

• Lower power consumption compared to traditional rotary fan.

• Low noise level.

Three-layer PZT bimorph actuator

Fan blade (Polyester film)

http://dx.doi.org/10.1016/S0924-4247(99)00231-9

Previous Works

http://catalog.pelonistechnologies.com/Asset/Intel%20Piezo%20Report.pdf

• Acikalin et.al thoroughly studied the factors affecting the piezoelectric fan cooling including relative position, vibration amplitude, frequency and etc.

• Wait et.al researched the efficiency of piezoelectric fan converting electrical energy into mechanical energy operating at higher flexural modes.

• Kimber et.al derived correlations obtaining forced convection coefficients from the vibration of piezoelectric fan.

However, the lack of systematic study of cooling efficiency in terms of power consumption needs to be addressed !

Power measurement

Function Generator + Amplifier current and voltage

Output monitoring signal from amplifier

Data processing

𝑃= 1𝑇 ∫

0

𝑇

𝑉 (𝑡 ′ ) 𝐼 (𝑡 ′ )𝑑𝑡 ′

The total power consumption of piezoelectric fan:

Heat transfer setup

Back of the Flexible heater

Power Measurement Result

Total power consumed• Parasitic power dissipation• Flow power (correlates

directly to cooling)

Parasitic power dissipated in PZT actuator• Internal friction• Dielectric loss • Heat generation

Need to estimate flow power !

Dynamic Model of Piezoelectric Fan

𝐾 2 ,𝐶2 ,𝐶2𝑎𝐾 1 ,𝐶1 ,𝐶1𝑎𝑚1 𝑚2

After measuring the vibration amplitude of piezoelectric fan

Flow power estimation

𝑃 𝑓=83 𝐶2𝑎|𝑦2|

3𝜔2 𝑓

After obtaining the aerodynamic damping coefficient

Flow power at various input voltages Finite amount of power difference represents the parasitic power dissipation

Total Power Flow Power

PZT loss

Changing Blade Thickness

Configuration blade length (mm) Rang of Resonance Frequency (Hz)

Range of Voltage Applied to Piezo

Actuator (V)Thickness (mm) Material

I (Changing Thickness) 32 35 - 119 70 - 140 0.127 - 0.508 Kapton sheet (Ployester)

II (Changing length) 19 - 50 30 - 188 70 - 140 0.254 Kapton sheet (Ployester)

Change in Blade Thickness

Experimental Investigation

𝑃𝑜𝑤𝑒𝑟 𝑁𝑜𝑟𝑚𝑎𝑙𝑖𝑧𝑒𝑑𝐻𝑒𝑎𝑡𝑇𝑟𝑎𝑛𝑠𝑓𝑒𝑟 𝑃𝑒𝑟𝑓𝑜𝑟𝑚𝑎𝑛𝑐𝑒 :𝑃𝑁𝐻𝑇=h𝑃=

𝑄/∆ 𝑇𝑃

Experimental Investigation

Change in Blade Length

𝑃𝑜𝑤𝑒𝑟 𝑁𝑜𝑟𝑚𝑎𝑙𝑖𝑧𝑒𝑑𝐻𝑒𝑎𝑡𝑇𝑟𝑎𝑛𝑠𝑓𝑒𝑟 𝑃𝑒𝑟𝑓𝑜𝑟𝑚𝑎𝑛𝑐𝑒 :𝑃𝑁𝐻𝑇=h𝑃=

𝑄/∆ 𝑇𝑃

Conclusion

• Using aerodynamic damping () results in a better match than the linear damping ()

• The flow power induced by the piezoelectric fan can be estimated by subtracting the power dissipation in the PZT actuator from the total power consumption.

• Heat transfer Performance of the piezoelectric fan is more relevant to the flow power not the total power.

• Plotting the “forced convection coefficient of the fan” vs. “flow power” gives a convergent curve.

Total Power Flow Power

PZT loss

Ongoing and Future Work

• Measuring force on an opposing flat surface due to piezo fan to find out relation between heat transfer performance and air jet momentum.

• Measuring the flow rate of the air jet to find the relationship between the air flow rate and heat transfer performance.

• Simulation-based investigation of the relation between tip velocity and vortex strength.

• Optimizing the blade motion for higher efficiency: Experiment and Simulation

Thank you for your attention

References

1. Açıkalın, Tolga, et al. "Characterization and optimization of the thermal performance of miniature piezoelectric fans." International Journal of Heat and Fluid Flow 28.4 (2007): 806-820.

2. Kimber, Mark, and Suresh V. Garimella. "Measurement and prediction of the cooling characteristics of a generalized vibrating piezoelectric fan." International Journal of Heat and Mass Transfer 52.19 (2009): 4470-4478.

3. Wait, Sydney M., et al. "Piezoelectric fans using higher flexural modes for electronics cooling applications." IEEE transactions on components and packaging technologies 30.1 (2007): 119-128.