臺灣博碩士論文加值系統

本文以實驗搭配逆運算法與Icepak探討橢圓板鰭管式熱交換器熱傳特性的研究，並探討橢圓鰭片間距、正向風速與兩種橢圓管尺寸對所得結果之影響。由於鰭片各點實際上的熱傳系數並不均勻，為了求得鰭片的平均熱傳系數，首先將鰭片劃分成數個小區域，並假設每個小區域內的熱傳係數為定值，接著搭配有限差分法及最小平方法來藉由實驗所得鰭片特定位置的溫度，以逆算法求得平均熱傳系數。本文也利用Icepak軟體求得實驗條件下的鰭片表面溫度與熱傳系數。結果顯示，增加鰭片間距可以使熱傳係數上升，並且會趨近於定值。提升流體風速可以使鰭片熱傳係數大幅提升，效果比增加鰭片間距還要好，但缺點是需要持續的外力來維持風速。當鰭片外緣相同時，中心的橢圓管徑越大，鰭片熱傳係數越大，但是風速越快時不同管徑的熱傳係數差距反而越小。另外，本文也利用模擬軟體分析比較不同情況下的鰭片周圍流場，並探討不同流動模式與網格切割對模擬結果之影響。

This study applies inverse method and Icepak to determine the heat transfer and fluid flow characteristics of elliptical fin and tube exchanger with various fin spacing, flow velocity and various tube size. Since the distribution of the heat transfer coefficient on the fin is not uniform, the plate-fin is divided into several subregions and the heat transfer coefficient in each subregion is assumed to be unknown constant.Then using inverse method with measured temperature data to predict and analyze the average heat transfer coefficient on each subregion and then the whole region. The inverse method along with the finite difference method, least squares fitting method and experimental temperature data are applied to determine the heat transfer coefficient. Icepak is applied to get temperature, heat transfer and coefficient.
The results indicate that the average heat transfer coefficient increase with increasing fin spacing and flow velocity but will be close to a value when the fin spacing is infinite long. The results also show that the average heat transfer coefficient increases when tube size is large but the difference between two different tube size will decrease when flow velocity increases. In order to verify the reliability of the inverse method with predicted results of this paper, the present study also compares the empirical corelations of other relevant literature with CFD simulation packages.

摘要 I
Extended Abstract II
誌謝 VII
目錄 VIII
表目錄 XI
圖目錄 XIII
符號說明 XV
第一章 緒論 1
1-1 研究背景 1
1-2 文獻回顧 4
1-3 研究目的 5
1-4 研究重點與本文架構 6
第二章 逆向方法之理論分析 8
2-1 簡介 8
2-2 數學模型 8
2-3 數值逆運算法 11
第三章 數值模擬 15
3-1 簡介 15
3-2 假設條件 16
3-3 層流模式(Laminar model) 17
3-4 紊流模式(Turbulence model) 17
3-4-1 零方程式紊流模式(Zero equation turbulence model) 18
3-4-2 Standard k-ε紊流模式(Standard k-ε turbulence model) 18
3-4-3 RNG k-ε紊流模式(RNG k-ε turbulence model) 21
3-4-4 Realizable k-ε紊流模式(Realizable k-ε turbulence model) 22
3-4-5 Enhanced k-ε紊流模式(Enhanced k-ε turbulence model) 24
3-5 邊界條件 24
3-6 求解方法與程序 27
第四章 實驗操作 30
4-1 簡介 30
4-2 實驗設備 31
4-3 實驗步驟 33
第五章 結果與討論 38
5-1 逆向結果之討論 38
5-1-1 鰭片間距的影響 38
5-1-2 風速的影響 39
5-1-3 管徑的影響 41
5-2 模擬結果之討論 42
5-2-1 流動模式之選擇 42
5-2-2 計算域與網格測試 43
5-2-3 數值模擬流場分析 44
第六章 綜合結論與未來展望 84
6-1 綜合結論 84
6-2 未來發展方向與建議 85
參考文獻 87

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