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研究生:董世欽
研究生(外文):Dung Shi-Chin
論文名稱:水平圓管外層流膜狀凝結熱傳之熱力學第二定律分析
論文名稱(外文):Second Law Analysis of Laminar Film Condensation on a Horizontal Tube
指導教授:楊勝安楊勝安引用關係
指導教授(外文):Yang Sheng-An
學位類別:碩士
校院名稱:國立高雄應用科技大學
系所名稱:模具工程系碩士班
學門:工程學門
學類:機械工程學類
論文種類:學術論文
論文出版年:2006
畢業學年度:94
語文別:中文
論文頁數:50
中文關鍵詞:圓管膜狀凝結熱力學第二定律
外文關鍵詞:entropytubetubefilm condensationsecond law
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本論文研究係採用熵增最佳化(EGM)方法,宗旨在分析慢速流動之飽和蒸汽在水平圓管外的熵值增加率。本文獲得用於說明圓管外膜狀凝結之特定不可逆率的作用之熵增率的公式,針對水平圓管在不同的邊界條件下:﹙1﹚表面定溫之穩態情況, ﹙2﹚表面溫度可變化之穩態情況,作層流膜狀凝結熱傳熵值增加率分析。
本研究結合Adrian Bejan學者所提出在對流熱傳下熵增原理與最佳化方式與指導教授楊勝安教授之膜狀凝結熱傳研究方法,針對不同的Brinkman參數、Rayleigh參數以及Jakob參數效應等,採用數值分析方法並搭配相關研究參數,分別分析等溫圓管之局部與平均之無因次化熱傳熵增率與局部不可逆率比。最後再作可變壁溫之水平圓管外層流膜狀凝結熱傳之熵增定律分析。結果顯示,局部熵增率隨Brinkman參數增加而變大。當Rayleigh參數遞增時,無因次熱傳係數增強,然而也造成局部熵增率增加。相對不可逆率分佈比值顯示不可逆率主要係由熱傳效應所主控;重力帶動之薄膜流動摩擦只有在接近半圓周處才具與熱傳相當之影響力。
最後本論文將與前人所作之熵增定律分析結果作比較,分析其優劣,提供3C大廠對於未來3C產品效能與節能兩方面取捨的設計參考。
This study uses the entropy generation minimization (EGM) method to optimize a saturated vapor flowing slowly onto and condensed on an isothermal horizontal tube. We derive an expression for entropy generation, which accounts for the resultant action of specified irreversibilities of film-wise condensation outside a tube, subjected to different kinds of boundary conditions which include (1) steady isothermal wall temperature, (2) variable (non-isothermal /isothermal) wall temperature.
This thesis combines the EGM technique proposed by Adrian Bejan for a laminar flow with convection heat transfer and the heat transfer approach for laminar film condensation by my adviser, Dr. Yang, to investigate both local and mean dimensionless entropy generation rate of laminar film condensation on a horizontal tube subject with both isothermal wall and variable wall temperature respectively. The present paper uses numerical approach and studies the effects of various working parameters, including Brinkman, Rayleigh, and Jakob numbers on the entropy generation rate. Besides, the irreversibilities ratio of finite temperature difference heat transfer and film flow friction are also studied.
The result shows that local entropy generation rate increases with Brinkman group parameters. As Rayleigh group parameters increase, dimensionless heat transfer coefficient is enhanced, but entropy generation number is augmented too. The result of irreversibility distribution ratio indicates that heat transfer irreversibility dominates over film flow friction irreversibility except around the middle way of streamwise length for the cases .
Finally, the present result is also compared with that different model. Besides, it will offer the electronic enterprise a reference data in the future.
目錄
頁數
中文摘要---------------------------------------------------------------------------------------I
英文摘要--------------------------------------------------------------------------------------II
誌謝------------------------------------------------------------------------------------------- IV
目錄---------------------------------------------------------------------------------------------V
圖目錄---------------------------------------------------------------------------------------VII
符號說明-----------------------------------------------------------------------------------VIII
第一章 前言----------------------------------------------------------------------------------1

1–1熱力學第二定律----------------------------------------------------------------1
1–2凝結物理模式--------------------------------------------------------------------2
1–3文獻回顧--------------------------------------------------------------------------3
1–4研究動機--------------------------------------------------------------------------6
1–5論文結構--------------------------------------------------------------------------6

第二章 熵增定律理論分析--------------------------------------------------------------12

2–1對流熱傳之局部熵增變化--------------------------------------------------12
2–2流動摩擦不可逆率與熱傳不可逆率-------------------------------------14

第三章 均勻壁溫下水平圓管外層流膜狀凝結熱傳之熵增定律分析-------16

3–1物理模型與理論分析---------------------------------------------------------16
3–2結果與討論---------------------------------------------------------------------23
3-2-1 均勻壁溫下水平圓管外層流膜狀凝結熱傳之局部熵增變化
----------------------------------------------------------------------------23
3-2-2 均勻壁溫下水平圓管外層流膜狀凝結熱傳之平均熵增變化
----------------------------------------------------------------------------25

第四章 非均勻壁溫下水平圓管外層流膜狀凝結熱傳之熵增定律分析----31

4–1物理模型與理論分析---------------------------------------------------------31
4–2結果與討論---------------------------------------------------------------------38
非均勻壁溫下水平圓管外層流凝結熱傳之熵增變化
(A=1, )----------------------------------------------------38

第五章 結論---------------------------------------------------------------------------------44

5–1綜合討論------------------------------------------------------------------------44
5–2未來研究方向與建議---------------------------------------------------------45

參考文獻------------------------------------------------------------------------------------- 46
簡歷--------------------------------------------------------------------------------------------50
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