Cooling the Heated Plate by Piezoelectric Fans with Different Shapes
Date Issued
2016
Date
2016
Author(s)
Ma, Sheng-Lun
Abstract
Effect of the piezoelectric fan with different shapes on cooling the heated plate has been investigated experimentally. Previous studies focused mainly on the cooling effectiveness under various parameters, especially the piezoelectric fan of its location and the heat sink of its fin design, but less exploring their transient flow structure and mechanism. Herein, we observe the air flow near the heated plate and illustrate the mechanism with velocity and vorticity distribution of hot flow. Three blade shapes of piezoelectric fans– trapezoid, rectangle, and invert trapezoid were analyzed at the similar frequency. Trapezoidal shapes have wide root and short leading edge of the blade, and invert-trapezoidal shapes are opposite. The piezoelectric fan was vibrating up and down at 15 mm above the ground parallels the heated plate. To explore the relationship between the thermal resistance and the flow structure, we measured velocity, vorticity and thermal resistance via high-speed particle image velocimetry (PIV) and thermocouples embedded in the heated device. The results reveal that the thermal resistance in invert-trapezoidal shape is 5-9 % less than in other shapes at the similar frequency. Because invert-trapezoidal shape generates more concentrated downward oscillating airflow, the flow is separated into left and right airflows and takes the heat away from the plate after arriving the heated plate. This forced convection enhance the heat dissipation and decreases thermal resistance between the hot plate and the surroundings. However, downward airflow generated by the trapezoidal shape is so wide that it cannot be spilt easily onto the heated plate. Our research for the flow characteristics of the piezoelectric of different fan shapes can be applied to the cooling electronic devices. By selecting an invert-trapezoid fan shape, more heat can be dissipated from electronic devices. Therefore, the enhancement of heat transfer which sheds light on the concept of optimal design for cooling devices effectively extends the lifespan of electronics and improves their performance.
Subjects
piezoelectric fan
visualization of velocity
fan shape
Type
thesis