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系統識別號 U0026-1806201921573700
論文名稱(中文) 乾-溼分離式冷卻水塔之三維流場分析與電腦輔助設計軟體開發
論文名稱(英文) 3-D Flow Field Analysis and Development of Computer Aided Design Software for a Dry Wet Cooling Tower
校院名稱 成功大學
系所名稱(中) 機械工程學系
系所名稱(英) Department of Mechanical Engineering
學年度 107
學期 2
出版年 108
研究生(中文) 吳仲凱
研究生(英文) Chung-Kai Wu
學號 N16061066
學位類別 碩士
語文別 中文
論文頁數 81頁
口試委員 指導教授-張錦裕
口試委員-陳志臣
口試委員-魏蓬生
口試委員-黃正弘
中文關鍵字 冷卻水塔  白煙  流場分析 
英文關鍵字 Cooling Tower  Plume  Flow Field 
學科別分類
中文摘要 傳統冷卻水塔為熱交換器的一種,透過流體間(水與空氣)的直接接觸熱傳,利用熱傳導、對流與蒸發的方式進行熱交換,其目的在將系統或製程中產生的廢熱,以循環水吸收後成為熱水,透過冷卻水塔冷卻為冷水,再進入系統或製程,形成一個冷卻水的迴圈。傳統冷卻塔因完全透過蒸發散熱,出口之空氣溫度高,且相對濕度極高,當外界為氣溫較低且潮濕之環境時,冷卻水塔出口空氣接觸到外界低溫高濕度之空氣,會使空氣快速降溫,空氣所能含水量降低,使大量水蒸氣冷凝為肉眼可見之小水滴,即是我們看到的白煙(Plume)現象,其雖然對人體與環境無害,但會造成視覺障礙,影響視野。且傳統之冷卻塔使用熱傳面積大之填料,將循環水由頂端灑落,使填料表面覆蓋一層水膜,大幅增加其散熱面積,以致於大量之循環水蒸發至空氣中,造成不少之循環水損失。
本論文主要目的,在設計一個簡單易懂、人性化的操作介面,讓使用者透過單純的輸入各項需求的操作條件,經過程式的計算,能夠自動產出乾盤管及填料各別之計算結果,以及乾濕空氣混合後總冷卻水塔之各項性能,讓使用者得到乾-濕分離式冷卻水塔計算之數據,並且輕鬆調整輸入條件,以滿足設計需求
為了改善白煙問題,本論文加入乾盤管之設計,其原理與空氣冷卻之逆流式熱交換器相同。首先高溫之循環水先通過乾盤管做第一次降溫,將其匯集後再灑於填料上蒸發做第二次降溫,相較於傳統冷卻水塔而言,可降低填料上方灑水之溫度,將乾盤管及填料交錯排列,並且利用通過乾盤管之乾空氣,使冷卻水塔內部之乾、濕空氣能夠充分混合,降低其出口空氣相對濕度,以減少秋冬季節時,因環境溫度低而造成冷卻水塔出口出現白煙的現象。當環境溫度高於25°C時,溼式冷卻水塔及乾-溼分離式冷卻水塔皆不會產生白煙,當環境溫度降為20°C以下後,溼式冷卻水塔即開始有白煙形成,乾-溼分離式冷卻水塔於環境溫度為5°C時才有白煙形成,因此乾-溼分離式冷卻水塔可運作於環境溫度高於5°C而無白煙形成,有效克服冷卻水塔於冬季或是寒冷地區因環境溫度低而容易形成白煙之缺點。
本論文亦透過套裝軟體ANSYS FLUENT模擬真實三維乾-濕分離式冷卻水塔流場,並在氣室內增加擾流板設計,可增加氣室內之空氣擾動,大幅增加氣室中乾濕空氣對流現象,有助於乾濕空氣混合,可將出口相對濕度大於90%空氣占比降低17.2%,有效減少高濕度之空氣量,減少白煙形成。
英文摘要 The paper analyse the flow field and humidity field of a three dimensional dry/wet cooling tower by using ANSYS. The dry/wet cooling tower is designed to reduce plume formation by adding dry coils into a wet cooling tower. In order to improve the mixture efficiency of dry air and water vapor, the spoiler is added above the dry coil to generate turbulence flow. A CAD software is also developed to calculate the dry/wet cooling tower design temperature and performance. By doing so, the engineer can easily receive the information without complex calculation while designing a dry/wet cooling tower. Plume occurs at ambient temperature under 20°C in a wet cooling tower while dry/wet cooling tower can operate at ambient temperature above 5°C without plume formation. As the ambient temperature decrease, the exit water temperature of a cooling tower will drop as well, dry/wet cooling tower has to increase 51.7% of heat transfer area to achieve same exit water temperature as a wet cooling tower. The dry/wet cooling tower with spoiler reduce 17.2% of air above 90% relative humidity which can lower the plume formation effectively.
論文目次 摘要 I
Abstract III
誌謝 IX
目錄 X
表目錄 XII
圖目錄 XIII
符號說明 XV
第一章 緒論 1
1.1 前言 1
1.2 文獻回顧 2
1.3 研究目的 5
第二章 冷卻水塔理論分析 9
2.1 冷卻水塔設計理論 9
2.1.1 熱傳量 值之計算 9
2.1.2 空氣出口之乾球及濕求溫度之計算 10
2.1.3 填料壓降之計算 14
2.2 乾盤管熱交換器設計理論 17
2.2.1 效率-性能係數( )關係式 17
2.2.2 乾盤管壓降之計算 20
2.3 乾濕空氣混合氣體理論 25
2.3.1 壓降平衡流量計算 26
2.4 電腦輔助設計軟體 30
2.4.1 輸入條件 30
2.4.2 結果輸出 31
第三章 乾-溼分離式冷卻水塔流場分析 35
3.1 物理模型 35
3.1.1 流體區統御方程式 35
3.1.2 擴散統御方程式 37
3.1.3 多孔性介質統御方程式 38
3.1.4 紊流模型 39
3.1.5 邊界條件設定 40
3.2 數值方法 41
3.2.1 通用守恆式 41
3.2.2 有限體積法 42
3.2.3 壓力耦合方程組的半隱式方法SIMPLEC 45
3.3 解題流程 46
3.4 收斂條件 46
3.5 格點測試 46
第四章 結果與討論 55
4.1 乾-濕分離式冷卻水塔參數分析 55
4.1.1 乾盤管設計對冷卻水塔出口水溫之影響 55
4.1.2 乾盤管設計在不同環境溫度下對白煙現象之影響 56
4.2 冷卻水塔之流場分析 62
4.2.1 冷卻水塔流場解析 62
4.2.2 冷卻水塔相對溼度分析 63
第五章 結論 77
參考文獻 79
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