複數片式壓電磁力連動風扇系統研究與最佳化

Investigation and Optimization of the Multiple Piezoelectric–Magnetic Fan System

譚理光(Li-Kuang Tan)

指導教授 ： 馬小康

國立臺灣大學/工學院/機械工程學研究所/博士(2015年)

https://doi.org/10.6342/NTU.2015.00883

摘要

本研究係針對複數片式壓電磁力連動風扇系統做複數片風扇之最佳間距及風扇距散熱片最佳距離進行分析，以及此系統對於熱對流係數提昇與散熱特性之研究。本研究當中之壓電磁力連動風扇系統係由一片主動式的壓電磁力風扇與二片被動磁力風扇，再運用壓電效應，磁力效應以及共振效應之結合後，複數片式壓電磁力連動風扇系統僅使用一片壓電片便可達成三片風扇同時產生連動效果，此連動效果進而推動氣流產生擾動並增強散熱效果。
在風扇間距實驗中風扇間距為0.233倍的風扇擺動長度時，有最佳的散熱特性，而風扇翼尖距散熱片距離為 0.05倍的風扇擺動長度時，此時熱阻值最低。而風扇系統在散熱片中不同的九個位置實驗中，在風扇翼尖離熱源最近的位置，有最佳的散熱特性；而在熱對流係數提昇與雷諾數的關係中，更可歸納並轉換為一個位置(x/Sl =0, y/Sh =0) 的熱對流係數提昇，後續研究可利用此一轉換方程式，換算出任一位置的熱對流係數提昇。

關鍵字

共振 ； 壓電磁力風扇 ； 冷卻特性 ； 熱阻 ； 對流係數

並列摘要

An innovative cooling technology vibrating fans with a piezoelectric-magnetic source is investigated for the thermal management of electronics devices. The objective is to establish a cooling system that uses a piezoelectric-magnetic force as a vibrating source to drive multiple fans for cooling. The vibration driving force is generated by a piezoelectric material actuator coupled with multiple magnetic resonance forces. The cooling performance in terms of thermal resistance is evaluated and measured with different configurations, including the aspect ratio of the fan pitch (P/L) that ranges from 0.167 to 0.333 and the ratio of the gap between the fan tip and the heat sink (G/L) that ranges from 0.0167 to 0.0833 with different fan input powers ranging from 0.15W to 0.25W. The results indicate that multiple piezoelectric-magnetic fan (“MPMF”) system is efficient consuming low power with an improved thermal performance (76.7%) compared with natural convection. In addition, the optimum P/L can be found at 0.233 with different fan input powers. Furthermore, the optimum G/L is 0.05 whereas the optimum P/L is 0.233. The MPMF system can apparently decrease thermal resistance with the advantage of lower power consumption.
The cooling performance and heat convection improvement for the MPMF system embedded in a heat sink are also evaluated at different fan tip locations. The results indicate that the fan tip location of the MPMF system at x/Sl =0.5 and y/Sh =0 is an optimum configuration, improving the thermal performance by 53.2% over natural convection condition for the fan input power of 0.1 W. The MPMF system breaks the thermal boundary layer and causes fluctuations inside the fins of the heat sink to enhance the average heat transfer coefficient. Moreover, the relationship between the convection improvement and the Reynolds number for the MPMF system has been investigated and transformed into a correlation line for nine different fan tip locations to provide a means of predicting the cooling performance for the MPMF system embedded in a heat sink.

並列關鍵字

Resonance ； The multiple piezoelectric–magnetic fan system ； Cooling performance ； Thermal resistance ； Heat transfer coefficient

參考文獻

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