本文內容主要探討鰭片式熱交換器，以內外套管冷卻方式進行，外套管的冷卻水以逆向流之流動方式，觀察內套管之流體隨時間冷卻變化之現象，其中將會透過模組建立與計算有限元素格點與多物理場數值方法進行分析。首先藉由初始原型之模型建立，得到冷卻溫度差初始值，再藉由物體型體建立的差異性，來追求冷卻系統效率的優化。
其中物體型體建立的差異性，是以內外套管鰭片有無、以及數量增減、旋轉角度的條件。觀察是否造成流體擾流，以及熱交換面積增加，兩相比較條件之收斂結果，來探討並比較其冷卻效率優劣。
從此研究結果可得出降溫效果從原型，到增加內鰭片後從每五段各三支、每五段各六支之後，可以得到顯著的降溫改善效果。在增加內鰭片一倍數量情況下，發現入口與出口溫差變更小，推斷是內鰭片數量過多過密造成流體過多阻力，影響流體進入內套管後的流速，後半段流體熱交換效益便下降。同樣情況下把內鰭片長度減半，60mm減短至30mm，入口與出口溫差變大，由此更加證明無效的內鰭片數量與長度造成流體阻力過大，擾流過多，反而降低了熱交換降溫效益。

This paper mainly discusses the physical phenomenon of fin double tube heat exchanger in the reverse flow, and observes the physical cooling phenomenon effectiveness for each different fin tubes model. It’s analyzed by experimental and computational fluid dynamics (CFD) software. The original model with no fins, then increase the fin quantities and rotate fine angle, change length, so we can compare the simulation result, check the outlet working fluid temperature, find the more optimal one.
We found the fin distributed situation will seriously impact the heat dissipation, in terms of theory, the more fins mean the more dissipation , but it will disturb the fluid flow.
We can get the convergence result with the fins increase and the cooling effectiveness.
Most of the literature only discusses the problem of heat exchanger.

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