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  • 學位論文

傾斜檔板角度對平板型散熱片熱流特性之影響

Effects of the inclined angle of a plate shield on the thermal and flow characteristics of a Plate-Fin Heat Sink

指導教授 : 蔡國隆

摘要


本文利用計算流體力學軟體(FLUENT),在雷諾數Re=10000、20000、30000及40000下之操作情形,改變散熱片鰭片高度(H=30、45、75mm)和傾斜檔板角度(45°、60°、75°、90°、105°、120°及135°),藉此來探討平板型散熱片熱流特性之影響。 研究結果顯示在低雷諾數下,傾斜檔板角度的改變對壓降的變化影響很小,而隨著雷諾數的增加,在高雷諾數狀態下,不同傾斜檔板的變化,使整個流場的壓力變化增大,然而散熱片高度的增加可使整個流場的壓力下降程度降低,但在最高散熱片高度之下,轉動傾斜檔板角度時,所產生的壓降變化很小。若論流場變化來說,使用較矮的散熱片其所搭配的傾斜檔板面積比較大,造成進入散熱片之鰭片與鰭片之間的流體產生加速的行為;在所有的狀況下,就以增加散熱片高度來說,均可有效的降低熱阻。傾斜檔板角度的改變,對降低熱阻的影響並不大,但在傾斜檔板角度135度時所顯示的熱阻值是最大,同時就流場壓差而言,傾斜檔板角度之影響於高雷諾數及較低鰭片高度時變的相當明顯,如Re=40000和H= 30 mm時,傾斜檔板角度105度時有最小的壓降,而Re=40000下,H=45及75 mm最小壓降之檔板傾斜角度分別為90度及105度,因此就兼顧散熱性能和流動性能而言,檔板傾斜角度會因散熱鰭片高度而有最佳值。

並列摘要


This study uses Computational Fluid Dynamics software (FLUENT) and its operation under different Reynolds Numbers listed as follows: Re=10000, 20000, 30000 and 40000; by changing the height of the Heat sink (H=30, 45 and 75, respectively), and the angle of the plate shield (at 45°, 60°, 75°, 90°, 105°, 120° and 135°, respectively), to explore the effects of thermal and flow characteristics of Plate Heat Sinks. The research shows that under smaller Reynolds Numbers, the plate-shield’s angle effects are minimal towards the pressure difference. However, with the increase of the Reynolds Number, the difference between the shield angle’s effects on the flow pressure increases as well. While the higher the heat sink, the smaller the pressure drop of the flow pressure; but under the highest heat sink setting, when turning the plate shield’s angle, the pressure drop is relevantly not obvious. From the prospect of flow pressure differential, the lower the heat sink combined with a wider plate shield angle, would cause an increase of fluid flow in between the plate fins. Under all circumstances, increasing the heat sink’s height can effectively lower the heat resistance. The plate shield’s angle, on the other hand does not greatly affect the heat resistance, however when set at 135°, the heat resistance reaches maximum value. Meanwhile regarding the fluent flow pressure difference, the plate shield angle’s effect are more obvious when the Reynolds number is high and the plate fins are lower, for instance when Re= 40000 and H= 30 mm, the angle of the plate shield at 105° has the lowest of pressure drop; on the other hand, when Re= 40000, H= 45 / 75 mm, the lowest pressure drop occurs when the plate shield angle is at 90° and 105°, respectively. Therefore, to conclude the research, to lay stress on both cooling functions and the flow characteristics of fluids, the plate shield angle would create the best result depending on the height of the heat sink.

參考文獻


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