本研究分為兩個部分，第一部分為螺旋管熱增強性能分析，研究在不同螺旋曲率直徑、不同工作流體(液態水、空氣)、以及不同進口流速之狀態下，進行模擬並與相同管內徑之直圓管比較；第二部分為煙囪出口是否有白霧現象產生之流場分析。
首先，第一部份，在進口流速與流體等條件相同的情況下，因為流體在螺旋管管內流動有離心力的關係，使流體流動更加劇烈，造成二次流的現象產生，故相較於直圓管熱傳效果明顯較好，約增加120%，但壓降也相較於直圓管明顯較高，約增加為130%。另外，螺旋管在不同螺旋曲率直徑下，螺旋曲率直徑愈小，管內流體流動更加劇烈，因而造成熱傳與壓降效果提高，以本研究螺旋曲率直徑最小的1400毫米為基準，螺旋曲率直徑每增加600毫米，熱傳效能約減少103%，壓降則減少106%。在螺旋管對直圓管的面積縮減率上，螺旋管管內工作流體為水時的熱傳效果雖然相較直圓管明顯較多，但因為壓降也相對較多的緣故，所以面積縮減率並不大，反而是以空氣為工作流體時的面積縮減率較明顯，故以工作流體為水來說，如果單純以熱傳效率為考慮的話，則螺旋管是可以替換直圓管的；但如果係以熱傳面積為考量的話，就必須考量螺旋管製作成本與其熱傳及壓降效能的比較，再考慮是否適合使用螺旋管。
第二部分為研究煙囪出口煙氣在相同的出口流速、溫度及相對濕度下，接觸到不同環境下的溼空氣時，濕空氣中的水蒸氣是否會達到冷凝的條件而形成小水滴，而通常相對濕度在95%以上幾乎就能產生肉眼可見的白霧現象。在熱力學分析上，因為僅能知道煙囪排放的流量，而不知環境受煙囪出口影響時被吸引的流量，故僅能以當時的煙氣溫度及比濕與環境的溫度及比濕，在濕度圖上做連線，並預測環境流量在哪些範圍會有白霧的產生。而在計算流體力學分析上，則可以追蹤流場每個位置，故可以清楚看見哪的地方有白霧現象，以台灣相對濕度較高的氣候環境來模擬，當環境溫度到25℃時，相對濕度最大也只有92%，且以僅有一小部分，幾乎不可能產生白霧現象；而當環境溫度為20℃時，接觸混和後的相對濕度有大面積到了95%以上，且最大也有100%，開始有白霧現象的出現；最後，在環境氣溫為15℃時，煙囪所排出的煙氣與環境的濕空氣接觸混和後有大面積的相對濕度在100%左右，白霧現象則更加明顯了。

There are two parts in the study, one is analysis of the heat enhancement performance of the helical coil, and the other is whether there is white fog at the outlet of the chimney and the flow field analysis, by using CFD analysis. In the first part, the fluid flowing in the helical coil has the relationship of centrifugal force, causing the phenomenon of secondary flow, so it is compared with the heat transfer effect of the straight tube is obviously better, about 120%, and the pressure drop is also higher, about 130%. In addition, under different helical curvature diameters of the helical coil, the smaller the helical curvature diameter, which will increase the heat transfer and pressure drop effects. The second part is to study whether the vapor in the humid air reaches the condensing condition and forms droplets when the flue gas at the chimney outlet is in contact with humid air in different environments at the same outlet flow rate, temperature and relative humidity. In reality, relative humidity above 95% can almost produce white fog visible. By using CFD to track each position of the flow field, and clearly see where there is white fog. When ambient temperature is lower, the white fog has produced more.

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