論文摘要

以池沸騰形式之熱傳現象在現今之工業的應用上可說是相當的廣泛，然而要一般化及準確的預測其熱傳係數卻是相當的不容易，主要的原因是池沸騰之核化沸騰(nucleate boiling)熱傳現象相當複雜，而熱傳係數視不同加熱表面之粗糙性、面積、材質、幾何形狀大小、排列方式及工作液體之不同而有不同結果。在這些不同的加熱表面下，沸騰時氣泡離開時之頻率（frequency）、半徑（departure diameter）、及加熱表面之有效核蕊密度(active nucleation site density)等參數（bubble dynamics data）會有所不同，因此會造成不同之熱傳效果。本研究以實驗方式進行，工作液體使用R-134a環保冷媒。測試管則分為平滑及以電漿塗佈（plasma coating）銅兩種不同表面性質。主要探討之項目為在不同測試管表面性質、數量、幾何排列方式及加熱量情況下對核化沸騰熱傳之影響，並計算出熱傳係數及其它相關參數，了解在上述各種不同實驗情況下所有相關係數之修正值，以期瞭解此類熱傳增強表面在R-134a冷媒之沸騰傳熱機制。並依據實驗結果，尋求出不同狀況下的沸騰曲線，計算它們的平均熱傳係數、管群因子及管排形狀因子。除此之外，尋找熱傳係數、冷媒性質與測試管表面性質之間的關係。在實驗結果發現塗佈管群之熱傳係數較平滑管群來的高，其熱傳增強效果在單管組中約為1.1至2.2倍。平滑管群之所有管群因子是屬於較穩定的狀態，約固定在1.5至2.3之間，塗佈管群的管群因子範圍在1.1至3.8之間。至於管排形狀因子方面，其值約在1左右。本實驗的主要目標是將實驗結果提供工業界或學術界設計高性能滿溢式熱交換器之參考。

Abstract

Pool boiling process is frequently encountered in a number of engineering applications. However, it is difficult to exactly predict the heat transfer coefficient. This is because the nucleate pool boiling phenomenon is rather complex and influenced by many factors, such as surface roughness, areas of heater, material, geometry, arrangement of heated rods, and refrigerants, etc. The key boiling parameters (bubble dynamics data) such as bubble departure frequency, diameter and active nucleation site density will be varied in such different heated surface resulting in the different effect of heat transfer. This study was performed experimentally. R-134a was used as refrigerants, and the present study is aim at providing the pool boiling data for smooth and plasma coating enhanced tube bundles. It is expected that the surface condition, amount of test tubes, geometric of bundles and different heat flux can affect the nucleate boiling heat transfer in certain degree. In addition were calculated and developed that heat transfer coefficients and relevant corrections. Furthermore, more fundamental of the physical phenomenon can be obtained. According to the results of experiments, Boiling curves and calculations of the bundle factors and geometry factors were subsequently secured. The enhanced heat transfer coefficients with coated tube bundles are 1.1-2.0 times higher than smooth tube bundles. The 1.5-2.3 and 1.1-3.8 bundle factors obtained from the smooth tube bundles and coated tube bundles respectively. The geometry factors were about 1 for all arrangements studied herein. Thermal design data of a flooded type evaporator of high performance as well as more and further physical insight of the above-stated nucleate boiling heat transfer can be acquired. The results will hopefully be helpful not only for the academia but for the industry.

目 錄
頁 次
目錄 1
圖目錄 4
表目錄 5
符號說明 6
中文摘要 8
英文摘要 9

第一章 緒論 10
1-1 前言 10
1-2 背景與目的 11
1-3 文獻回顧 14
1-4 研究範圍 18

第二章 實驗系統設備 20
2-1 加熱系統 20
2-2 測試容器 20
2-3 恆溫水槽 21
2-4 凝結器 22


第三章 實驗方法及步驟 26
3-1 實驗方法 26
3-1-1 測試管製作 26
3-1-2 SEM觀測 26
3-1-3 改變測試管之數量及幾何位置 26
3-1-4 固定系統之飽和狀態 27
3-1-5 控制測試管之熱通量 27
3-2 實驗步驟 27
3-2-1 清洗 27
3-2-2 測漏 27
3-2-3 進行實驗 28
3-2-4 數據處理 28

第四章 理論分析 33
4-1 熱通量計算 33
4-2 熱電偶溫度處理 33
4-3 熱傳係數的計算 34
4-4 平均熱傳係數的計算 34
4-5 管群因子的計算 35
4-6 管排形狀因子的計算 35

第五章 誤差分析 36

第六章 結果與討論 40
6-1 單排組 40
6-2 雙排組 45
6-3 三排組 47
6-4 正三角組 49

第七章 結論與建議 62
6-1 結論 62
6-2 建議 63

參考文獻 65

附錄 71










圖 目 錄

頁次
圖2-1 測試加熱管之截面示意圖 15
圖2-2 測試容器示意圖 16
圖2-3 測試設備溫度量測點分佈圖 17
圖3-1 測試管SEM觀測結果 23
圖3-2 測試管排列幾何形狀示意圖 24
圖6-1 單排組沸騰曲線圖 45
圖6-2 雙排組沸騰曲線圖 46
圖6-3 三排組沸騰曲線圖 47
圖6-4 正三角組沸騰曲線圖 48
圖6-5 單排組熱傳係數特性圖 49
圖6-6 雙排組熱傳係數特性圖 50
圖6-7 三排組熱傳係數特性圖 51
圖6-8 正三角組熱傳係數特性圖 52
圖6-9 管群因子特性圖 53
圖6-10 管排形狀因子特性圖 54


表 目 錄

頁次
表3-1 測試管表面性質 22
表5-1 參數及變數誤差值 31
表6-1 冷媒性質 44

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