池沸騰熱傳在工業上的運用相當廣泛，但是要一般化及準確的預測其熱傳係數卻相當困難。主要是因為池沸騰之核化沸騰熱傳現象相當複雜，且其熱傳係數會隨著加熱表面之表面情況、幾何形狀大小、材料、排列及工作液體之不同而有所變化。而在這些不同的加熱表面下，沸騰時氣泡脫離半徑（departure diameter）、頻率（frequency）、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。為了增加池沸騰之熱傳效率，將對上述所提影響核化沸騰之參數進行更深入的探討。

本研究欲以實驗方式進行，工作液體有R-134a及R-600a，以電漿塗佈（plasma spraying）和在加熱棒外加線圈的方式來改變加熱表面之材料及表面情況。探討測試管幾何形狀及表面情況對核化沸騰熱傳之影響；並以高速之攝影設備拍攝，了解在各種不同測試管之情況下氣泡生成之情形，以期瞭解此類熱傳增強表面在R-600a及R-134a 兩種冷媒之沸騰傳熱機制。依據實驗結果，可尋求出不同狀況下的沸騰曲線，並計算它們的熱傳係數。除此之外，考慮熱傳係數、冷媒性質與測試管表面性質之間的關係建立一經驗公式。

最終目標希望能夠找出熱傳效果最好之增強表面，以提供設計高性能滿溢式(flooded type)冰水機之參考;並對核化沸騰之熱傳現象有全盤且更深入之了解，以建立更完整之學理基礎，提供學術界作為參考。

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 boiling phenomenon is rather complex and influenced by many factors, such as surface condition, heater size, geometry, material, arrangement of heated rods, and refrigerants, etc. The key boiling parameters (bubble dynamics data) such as bubble departure diameter, frequency and nucleation site density will be varied in such different heated surface resulting in the different effect of heat transfer. The present study is ain at providing the pool boiling data for plasma coating and helical wire wrapped enhanced tubes. Furthermore, more fundamental of the physical phenomenon can be obtained.

This study was performed experimentally. R-134a and R-600a were used as refrigerants. The surface condition will be changed with plasma spray coating and helical wire wrapped. It is expected that the surface condition can affect the nucleate boiling heat transfer in certain degree. In addition, boiling visualization was also made to broaden our basic understanding of the bubble diameter and dynamics while growing.

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 i
圖目錄 iv
表目錄 v
符號說明 vi
中文摘要 ix
英文摘要 x

第一章 緒論 1
1-1 前言 1
1-2 背景與目的 2
1-3 文獻回顧 5
1-4 研究範圍 10

第二章 實驗系統設備 11
2-1 加熱系統 11
2-2 測試容器 11
2-3 恆溫水槽 12
2-4 凝結器 13

第三章 實驗方法及步驟 16
3-1 實驗方法 16
3-1-1 測試管製作 16
3-1-2 控制測試管之熱通量 16
3-1-3 固定系統之飽和狀態 17
3-1-4 SEM觀測 17
3-2 實驗步驟 17
3-2-1 清洗 17
3-2-2 測漏 18
3-2-3 進行實驗 18
3-2-4 數據處理 19

第四章 理論分析與數據處理 20

第五章 結果與討論 23
5-1 沸騰曲線與磁滯現象 23
5-2 熱傳效率 26
5-3 測試管表面特徵觀測與量測 28
5-4 氣泡行為觀測 29
5-4-1 氣泡數目 29
5-4-2 氣泡直徑與頻率 31
5-5 熱傳增強管經驗公式 32

第六章 結論與建議 48
6-1 結論 48
6-2 建議 49

參考文獻 50

圖 目 錄

頁次
圖2-1 實驗設備與熱電偶配置圖 14
圖2-2 測試管與熱電偶配置圖 15
圖5-1 沸騰曲線圖 37
圖5-2 熱傳係數圖 38
圖5-3 SEM觀測結果圖 39
圖5-4 量測區域圖 40
圖5-5 氣泡數目與熱通量關係圖 41
圖5-6 氣泡脫離直徑與熱通量關係圖 42
圖5-7 氣泡頻率與熱通量關係圖 43
圖5-8 熱傳增強管熱傳經驗公式圖 44

表 目 錄
頁次
表5-1 冷媒性質 33
表5-2 熱傳增強比 34
表5-3 測試管種類與表面性質測量 35
表5-4 胚胎氣泡半徑與氣泡脫離直徑比較 36

參 考 文 獻


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