加裝刮片之風扇之散熱研究

Abstract

本文主要目的為利用數值方法，研究在風扇所產生的流場中，發熱元件表面加裝旋轉動刮片或銅製散熱機構去散熱，並加以觀察其中的流場及溫度場之變化，其一的旋轉運動刮片是利用極接近發熱元表面，藉由破壞發熱面的溫度邊界層，以提升熱傳效能，並改變刮片的幾何尺寸，加以觀察幾何尺寸與熱傳性能間的關係，其二的銅製散熱機構，是將此機構放置於發熱面上，利用其優良的低熱阻係數將熱散出，並分析當機構的幾何條件改變時，此機構的熱傳效能變化。 在數值計算流場方面採用k-e紊流模式，利用有限體積法求得風扇與散熱機構間之流場與溫度場分佈，結果顯示發熱元件之熱傳性能，明顯受其相對於風扇位置而影響。利用加裝刮片去散熱後，發現可提升發熱元件之熱傳性能，當改變刮片的幾何尺寸後，發現變薄後熱傳性能變好，變短後熱傳性能降則低許多。而利用銅製散熱機構去散熱後，發現整體的發熱元件其熱傳性能也都有所提升，當改變機構的幾何條件後，發現當銅內水轉速變快時，熱傳效能變高，而在機構上加裝散熱鰭片後，所能帶走的熱量變多，但熱傳性能卻降低許多。 最後比較本文中的兩種散熱機構，與一般的散熱鰭片基座之熱傳性能比較，發現以旋轉運動刮片的熱傳性能最佳，而銅製散熱機構所能帶走的熱量最多，因此若能將此兩種機構結合在一起，相信一定會成為良好的散熱機構。

This main purpose of this article is studying heat dissipation and characteristics changes of flow and thermal fields on heated surface numerically by first, fan with rotating scratch plate, second, the copper heat dissipating device. This article shows different heat transfer performance relationship between different geometric sizes of thermal boundary layer destroying scratch plate of first device; and different heat transfer performance relationship between different geometric conditions of the low thermal resistance copper heat dissipating device on heated surface. In this numerical analysis, the finite volume method coupled with the k-e turbulent model are applied to solve the flow and thermal field. The results show that the heat transfer performance of heated surface is affected by the location of the fan. By applying the rotating scratch plate with the fan, the overall performance of heat transfer is improved. Results also show that with thinner rotating scratch plate, heat transfer rate is advanced; however, the heat transfer rate is retarded when using shorter scratch plate. Also, using copper heat dissipating device can improve the heat transfer performance of the heated surface. Heat transfer efficiency become better when rotational speed of the water in the copper heat dissipating device is faster; however, the efficiency become worse when the device is installed with fin. Finally, compare the two heat dissipating devices of this article with general heat sink and fin. The results show that the rotating scratch plate has the best heat transfer performance and the copper heat dissipating device can take away the most calorific capacities. So, if rotating scratch plate is combined with copper heat dissipating device, the device should become a fine heat transfer performance device.