臺灣博碩士論文加值系統

摘要
本文以Simple演算法直接求解具渦漩產生器之打孔板鰭橢圓管式熱交換器的三維熱流場現象，進而得到熱交換器的熱傳性能和壓降情況。直接解之局部熱對流係數結果並與逆算法中之共軛梯度法逆算求得之熱對流係數做比較，以驗證逆算法應用在求取打孔板鰭橢圓管式熱交換器之熱對流係數的正確性。由探討不同板鰭管式(圓管、橢圓管)熱交換器加裝渦漩產生器(vortex generator)的個數、置放位置、形狀等參數對熱傳及壓降的影響情形後，我們發現：在無渦漩器之板鰭管式熱交換器下，圓管式熱交換器比橢圓管的具有較高熱傳效果，然而也造成較高之壓降。當渦漩產生器加在管兩側前方時，橢圓管熱交換的熱傳效果卻比圓管的好，壓降也比圓管的低。可是當渦漩器放置在管兩側後方時，橢圓管熱交換器的熱傳效果反而比圓管的差，不過橢圓管壓降依然比圓管的低。探討渦漩器個數效應時：發現置放個數愈多，熱傳效果會愈好，壓降會愈大。渦漩器之形狀以三角翼對對板鰭管式熱交換器熱傳增強效果最顯著。由結果比較發現，共軛梯度法可以準確且快速的預測出打孔板鰭橢圓管式熱交換器之熱對流係數。本文所得結果對熱交換器界深入瞭解打孔板鰭橢圓管式熱交換器熱流場的壓降及熱傳係數情形有很大貢獻，所得數據可以提供熱交換器開發設計者充分的細部設計資料。

ABSTRACT
The three-dimensional fluid flow in a plate finned oval tube heat exchanger with vortex generator was studied with the SIMPLE algorithm method in addition to an understanding of heat transfer properties and pressure drop. The result of local heat transfer coefficient was analyzed directly and compared with the convection heat transfer coefficient obtained by the conjugate gradient method. This approach was to check the accuracy of the convection heat transfer coefficient in a plate finned oval tube heat exchanger with vortex generator via applying the reverse algorithm method. After exploring the impact upon heat transfer and pressure drop imposed by parameters of various plate finned tubes (circular, oval) heat exchangers with vortex generator such as the number, the position and the shape, etc., it was found that heat transfer effect of fin-tube heat exchanger with a circular tube without vortex generator was better than that with an oval tube; however, higher pressure drop was resulted. When the vortex generator was installed in the front of the tube on both sides, heat convection and transfer effect of an oval tube is better than that of a circular tube and pressure drop of the former is lower as well. Nevertheless, as the vortex generator was placed in the rear of the tube on both sides, heat convection and transfer effect of an oval tube is worse than that of a circular tube despite pressure drop of the former is still lower than that of the latter. From the perspective of the number of vortex generators, it was discovered that the more vortex generators were placed, the better the heat convection and transfer effect with greater pressure drop. A triangular winged vortex generator had the most significant performance of boosting heat transfer effect for a plate finned tube heat exchanger. Upon comparison of the results, it was found that the conjugate gradient method could predict the convection heat transfer coefficient accurately and rapidly for a plate finned oval tube heat exchanger. The results concluded from this article can make great contributions for people who expect to have an in-depth understanding about pressure drop of fluid flow and convection heat transfer coefficient for a plate finned oval tube heat exchanger. The data obtained may serve as a reference of complete detailed design information for heat exchanger developers and designers.

目 錄
中文摘要……………………………………………………………….Ⅰ
英文摘要……………………………………………………………….Ⅱ
目錄…………………………………………………………………….Ⅲ
圖目錄………………………………………………………………….VI
符號說明………………………………………………………………XI
第一章 緒論………………………………………………………．1
1-1前言………………………………………………………‥1
1-2文獻回顧…………………………………………………‥2
1-3研究動機…………………………………………‥………6
第二章 理論分析…………………………………………………‥9
2-1 共軛梯度法之理論分析……………………………………9
2-1-1 直接解問題…………………………………………10
2-1-2 靈敏性問題…………………………………………13
2-1-3 伴隨問題……………………………………………15
2-1-4 收斂條件……………………………………………17
2-1-5 數值計算流程………………………………………18
2-2 直接求解熱流埸數值法之理論分析………………………19
2-2-1 物理模型及基本假設………………………………19
2-2-2 統御方程式…………………………………………19
2-2-3 邊界條件……………………………………………21
2-2-4 熱傳係數及壓降係數計算…………………………22
第三章 數值模擬方法……………………………………………28
3-1 直接解之數值模擬………………．………………………28
3-1-1 網格點系統…………………………………………28
3-1-2 差分方程式之建立…………………………………29
3-1-3 求解流程……………………………………………31
3-1-4 鬆弛因子……………………………………………32
3-1-5 收斂條件……………………………………………34
3-2 打孔板鰭橢圓管式熱交換熱對流係數預測之數值模擬………………………………………………………．34
3-2-1 無渦漩產生器之板鰭管式熱交換器格網配置……35
3-2-2 打孔板鰭管式熱交換器格網配置…………………37
第四章 結果與討論………………………………………………42
4-1 板鰭管式熱交換器之熱流場分析………………………44
4-2 不同長短軸比之板鰭管式熱交換器加裝矩形翼渦漩產生器於管前方兩側………………………………………．48
4-3 共軛梯度法預測含有渦旋產生器之板鰭管式熱交換器之熱對流係數……………………………………………．51
4-4 渦漩產生器置放位置不同及個數對打孔板鰭橢圓管式熱交換器整體熱傳效益…………………………………．56
4-5 不同形狀之渦漩產生器對板鰭管式熱交換器的影響…60
第五章 結論與建議………………………………………………63
參考文獻………………………………………………………………111

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