壓電磁力連動風扇結合均溫板系統應用於微型電腦內 之散熱研究

Abstract

隨著科技的進步，電子產品及LED產業在生活中的重要性逐步提升，體積走向微型化，產生更大的散熱需求。散熱技術需要持續跟上，才能維護產品的功用，本實驗室之前發展出壓電磁力連動風扇的散熱技術，利用永久磁鐵搭配單片壓電片即可驅動多片扇葉進行強制對流散熱，在提高散熱效率的同時降低了噪音和高功耗等負面因素。 本研究將壓電磁力連動風扇和均溫板系統進行結合，設計了八種不同的風扇模組進行比較，並投入微型電腦之內部空間使用，將熱源產生的熱量，藉由均溫板傳遞到上方風扇前端的散熱鰭片，由壓電風扇系統輔助散熱，尋找最佳的模組以及影響散熱能力的各項參數。 實驗結果顯示有5片扇葉、扇葉間距11mm、扇葉由40mm長的碳纖維片和10mm麥拉片所組成的系統有最佳散熱效能，當熱源輸入功率為12W時，其熱阻值為2.99K/W，對流熱傳係數為21.98 Wm^(-2) K^(-1)，Nu值為86.88，Ri值為0.199，顯示在散熱系統中強制對流的高比例，此時的熱阻值較僅使用熱管時提高了50.2%，而功耗值為遠低於旋轉風扇的0.0702W。在實驗比較中，在扇葉前端設置麥拉片、增加扇葉間距、增加扇葉數量都能提高系統的散熱效能。 同時本研究也進行了PIV實驗，觀察風扇模組運作時周圍的流場情形，從後續分析中發現，最大風速為2.796m/s，而扇葉前端近處的流場受到扇葉影響較為混亂，拉開距離之後即變得相當平穩，有助於後續實驗的操作。

In this study, a multiple fans system with a piezoelectric actuator (MFPA) was integrated with a vapor chamber. The integrated system was embedded in a micro-computer for its thermal management. The MFPA utilized magnetic repulsive force to transfer power from the piezoelectric actuator to the adjacent passive fans. Models with different fan length, fan pitch and the number of the fans were developed. The thermal performance, vibrational amplitude, and power consumption of different models were investigated. The experiment results showed that the best models is the model with five fans, 11 mm fan pitch, 40 mm carbon fiber plate and 10 mm Mylar plate. When the input power of the system was 12W, it had the heat resistance 2.99℃/W, convective heat transfer coefficient 21.98 Wm^(-2) K^(-1), nusselt number 86.88, and Richardson number 0.199 when the power consumption was 0.0702W. The thermal resistance of all the models decreased when the input power increased. Besides, the model with shorter carbon fiber plate length, larger fan pitch and larger fan number had the lower thermal resistance. The PIV experiment was also be conducted. After observing the particle’s moving trend, the max speed 2.796m/s was measured and it was analyzed that the flow field near to the fan would be disturbed by the fans, and the farther one would be relatively stable.