臺灣博碩士論文加值系統

大型氣冷式冰水機之冷凝器通常係由多組鰭管式冷凝盤管所組成，由於受到機組外型尺寸之限制，使得冷凝盤管組之配置常有許多種不同之設計考量。然而，盤管之配置會影響經過冷凝盤管之氣流分佈，造成盤管表面風速不均勻，進而影響冷凝盤管散熱效率以及機組能源效率。因此尋找最佳之冷凝盤管配置，藉以改善氣流分佈與與提高熱傳性能之相關研究，就此成為此類設備性能提升之重要課題。有鑑於此，本研究主要的目的在於：利用CFD氣流模擬與熱交換器熱傳分析，再配合大型氣冷式冰水機組之實驗驗證的方法，比較在相同機組外型尺寸與風機性能之限制與不同外型尺寸相同風機性能條件下，進行不同盤管配置共十四種設計案例之氣流模擬與熱傳分析，藉由探討各個案例冷凝盤管的氣流分佈與熱傳性能之差異，尋找最佳之冷凝盤管的配置方式。
研究結果發現：在相同機型尺寸條件下僅改變盤管角度上的配置，並不能使內外盤管有均勻的分佈，對於平均風速與熱傳的改善也只有小幅度的變化，以案例5為最佳，分別改善7.19%與5.39%。A型式與B型式則分別為案例3A與3B，盤管總平均風速改善為29.01%與30.09%；總熱傳量則增加19.40%與20.74%。若以C型式的擺設，則盤管總平均風速改善為5.7%；總熱傳量則改善3.7%。盤管的配置以案例D為最佳。若以案例1為基準，則總平均風速可以改善達47.14%，熱傳則約有43.51%的改善空間。

The main purpose of this study is to find out the optimum coil configuration. Air-cooled liquid chiller coil configuration could strongly affect the condensing coil heat transfer. The coil configuration could affect the face velocity of condensing coil. CFD software-Airpak 2.1 is employed to simulate air flow field of the coils configuration. The numerical result was used to calculate the heat transfer of each coil. Compare with the baseline case 1. Case 5 could raise the average velocity nearly 7.19% and the heat transfer about 5.39%. Model A type, case 3A could raise the average velocity 29.01% and the heat transfer 19.40%. The optimum case of Model B type is case 3B, the average velocity could raise 30.09%, and heat transfer could raise 20.74%. When coil is Model C type, could raise the average velocity 5.7% and the heat transfer 3.7%. The optimum case of all cases is the case D, the average velocity could raise 47.14%, and heat transfer could raise 43.51%.

目 錄
摘 要 i
ABSTRACT ii
誌 謝 iii
目 錄 iv
表目錄 vi
圖目錄 vii
第一章 前 言 1
1.1 研究背景與動機 1
1.2 文獻回顧 3
1.3 研究目的 7
第二章 理論模式與數值方法 8
2.1 物理模型建立 8
2.2 理論模式 10
2.2.1 統御方程式 11
2.2.2 紊流流場模式 11
2.3 數值方法 14
2.3.1 對流-擴散方程式的差分型式 14
2.3.2 壓力-速度耦合的關係處理 16
2.4 鬆弛因數與離散方式 19
2.5 邊界條件設定及求解方法 19
2.6 熱交換器熱傳分析 20
第三章 實驗方法 25
3.1 實驗目的與設備介紹 25
3.2 實驗步驟與量測儀器 26
第四章 結果與討論 28
4.1數值模式驗證 28
4.1.1 格點獨立測試 28
4.1.2 實驗驗證 30
4.2 典型冷凝盤管之氣流分佈 32
4.3 改變盤管配置氣流模擬分析 40
4.3.2最佳分佈氣流模擬分析 51
4.4 綜合比較 76
第五章 結論與建議 79
5.1 結論 79
5.2 建議 80
參考文獻 81
符號彙編 83

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