- 學位論文
直接散熱之壓電風扇設計與測試
Design and Test of Piezoelectric Fans for Direct Cooling
摘要
本論文提出一種直接冷卻的概念，將壓電片黏貼於紅銅散熱片上，利用震盪散熱片的方法來增加散熱效果。 在單一散熱片（壓電風扇）的測試中，改變黏著劑的種類與壓電片的長度來進行尖端位移與尖端風速的量測。實驗結果顯示，選用剪切強度愈大的黏著劑，壓電風扇的衰退量愈低；選用硬度較高的黏著劑，壓電風扇的尖端位移量也愈大。在施加100 V電壓下，可產生尖端位移量10.9 mm、尖端風速2.3 m/s。 將五片單一散熱片組成陣列式的散熱模組，改變加熱瓦數來進行散熱測試，結果顯示在發熱源為5 W下，熱對流係數比自然對流增加約9 %。造成此熱傳效果不佳的原因為尖端位移量太小、鰭片整體表面效率太低與接觸熱阻過大。此些因素對熱傳的負面影響，大於散熱片擺盪時增加熱傳的效果，所以整體散熱效果的提升並不明顯。 使用導熱膠將散熱片與基座完全固定，可改善尖端位移問題。實驗結果顯示熱阻比自然對流降了33 %，熱對流係數提升64 %。將散熱片厚度增加至0.28 mm（長度為55 mm），鰭片整體表面效率可達0.9以上。若散熱片能一體成形，且能精準地控制共振頻率，使其能保持同步擺動，散熱效果會更加明顯。
並列摘要
This study presents a concept for direct cooling. Attaching the piezoelectric actuators to the copper fins can improve the heat transfer rate by the method of vibration. The single piece named piezoelectric fan with various piezoelectric patch geometries and bonding glues are made and tested. It is found that the decay of performance is reduced with the shear strength of glues and tip displacement is increased with the hardness of glues. The maximum tip displacement and tip velocity are 10.9 mm and 2.3 m/s respectively as driven by a 100 V power source. For the fin array with five pieces plates, the heat load is conducted. It is found that the convection heat transfer coefficient can enhance 9 % under natural convection with a 5 W heat load. The heat dissipation with vibrating fins is not as good as expected owing to a small tip displacement, low overall surface efficiency and great contact resistance. The tip displacement can be improved by fixing the fins and base completely with a thermally conductive adhesive between them. The results reveal that the thermal resistance reduces 33 % and heat transfer coefficient enhances 64 % under natural convection. The overall surface efficiency can reach to be 0.9 by increasing the fin thickness to 0.28 mm (fin length is 55 mm). If the fin system can always remain an in-phase vibration condition with the fins manufactured as an integral part and the resonant frequency controlled precisely, the heat transfer performance will be enhanced markedly.