臺灣博碩士論文加值系統

本論文利用熱力學第二定律研究一飽和蒸氣緩慢流過可變壁溫水平橢圓管外層流膜狀凝結熱傳問題。熵增最佳化可應用分析在可變壁溫水平橢圓管外層流膜狀凝結熱傳，及其由熱傳或是流體摩擦所引起損失。本文結果提供不同的幾何離心率及可變壁溫之水平橢圓管模型下，找出管外膜狀凝結熱傳過程中熵增的效應；並且根據熱力學第二定律的觀點，可以了解離心率與熵增數成正比。同時在不可逆率上，熱傳貢獻明顯大於流體摩擦的貢獻。最後，也可以達成分析均勻溫度及非均勻溫度下不同的熵增情形，以作為未來設計相關熱機系統的參考。

This thesis focuses on the thermodynamic second law analysis of saturated vapor flowing slowly onto and condensing on an elliptical tube with variable wall temperature. An entropy generation minimization, EGM, technique is applied as a unique measure to study the thermodynamic losses caused by heat transfer and film flow friction for the laminar film condensation on a non-isothermal horizontal elliptical tube. The results provide us how the geometric parameter-ellipticity and the amplitude of non-isothermal wall temperature variation affect entropy generation during film-wise condensation heat transfer process. From the second law point of view, entropy generation increases with increasing the value of ellipticity. Meanwhile, thermal irreversibility dominates over film flow friction irreversibility. Finally, the optimal design can be achieved by analyzing entropy generation in film condensation on a horizontal elliptical tube with further account for the amplitude of non-isothermal wall temperature variation.

中文摘要 I
Abstract II
Acknowledgments IV
Contents V
Figure Contents VII
Nomenclature XIII

Chapter 1.Introduction 1
1-1.Rationale 1
1-1-1.Condensation 1
1-1-2.Entropy 2
1-2.Literature Survey 2
1-2-1.Free Convection Laminar Film Condensation 3
1-2-2.Entropy Generation Minimization in Heat Transfer Analysis 6
1-3.The Objective of This Study 8
1-4.Organization of This Thesis 8

Chapter 2.Elliptical Polar Coordinates System 12
2-1.Equivalent diameter of elliptical tube and radius of elliptical curvature 12
2-2.Surface tension 14

Chapter 3.Entropy Generation Minimization of Film Condensation on a Horizontal Elliptical Tube 16
3-1.Analysis 16
3-2.Results and Discussions 22

Chapter 4.Thermodynamic Optimization of Film Condensation on a Horizontal Elliptical Tube with Variable Wall Temperature 28
4-1.Analysis 28
4-2.Results and Discussion 35

Chapter 5.Concluding Remarks 42
5-1.Conclusion 42
5-1-1.About Isothermal Condition 42
5-1-2.About Non-Isothermal Condition 43
5-2.Suggestion for Future Works 43
References 45
Appendix 50
Curriculum Vitae 74

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