指導教授：孫珍理臺灣大學：機械工程學研究所范皓翔Fan, Hao-hsiangHao-hsiangFan2014-11-292018-06-282014-11-292018-06-282014http://ntur.lib.ntu.edu.tw//handle/246246/263160本研究的目的是探討管徑大小與消散相質量分率對不同乳化劑在毛細管之內的沸騰現象、熱傳效率以及初始沸騰溫度的影響。實驗中選用的毛細管分為長方形與正方形毛細管兩種，內管截面分別為 200 × 200 μm^2、700 × 700 μm2、900 × 900 μm^2、1000 × 100 μm^2以及500 × 50 μm^2。乳化劑共有兩種，一種是消散相為太古油，連續相為純水之乳化劑，其中連續相的沸點較低；第二種是消散相為冷凍劑，連續相為甘油水溶液之乳化劑，其中消散相的沸點較低。 由結果可發現，正方形毛細管內之乳化劑在初始沸騰時，氣泡會在連續相與消散相液體之界面、加熱壁面或壁面上殘留之液體薄膜上成核，氣泡成長擴張時會將毛細管內之乳化劑排開，但毛細管壁面上會有少許乳化劑殘留。氣泡在方形管內成長時形狀較為對稱，與兩端壁面的接觸角相同。此外，消散相質量分率小時在正方形毛細管內能觀察到多顆成核氣泡同時生成的現象。反之，乳化劑在長方形毛細管沸騰時，多為單顆氣泡在連續相之中成核，氣泡在成長時與兩端壁面的接觸角不相同。一般而言，氣泡開始成核並且成長到整個毛細管壁的特徵時間介於10 - 100 ms之間。 於純水中加入太古油，在相同過熱溫度下熱傳率皆高於純水。此外，當消散相質量分率由0 (純水) 增加至0.001，將使太古油乳化劑的初始沸騰溫度上升30°C。但太古油質量分率繼續增加為0.01，初始沸騰溫度不會繼續升高，在質量分率大於0.1時，太古油乳化劑之初始沸騰溫度降為與純水相近。反之，在甘油水溶液中加入冷凍液NovecTM 7200，在相同過熱溫度下，冷凍液乳化劑的熱傳效果皆低於甘油水溶液。若在甘油水溶液中加入少量NovecTM7200液體，會造成冷凍液乳化劑初始沸騰溫度降低約10°C，但質量分率進一步增加為0.05時，其初始沸騰溫度並不會繼續降低。方型毛細管管徑大小對冷凍液型乳化劑的初始沸騰溫度影響較大，管徑為200 μm時初始沸騰過熱溫度最高，管徑900 μm之初始沸騰溫度最低，但管徑大小對於太古油乳化劑影響無明顯趨勢。另外，對於長方形毛細管，太古油乳化劑與冷凍液乳化劑的質量分率對熱傳效果皆無明顯趨勢。In this study, we investigate boiling of two different types of emulsions in a capillary. Influences of the capillary size and the mass fraction of the dispersed phase in boiling characteristics are studied. Capillaries of five different inner dimensions, 500 × 50, 1000 × 100, 200 × 200, 700 × 700, 900 × 900μm^2 are used. Two types of emulsions are chosen as our working fluids. The first type consists of sulfated castor oil as the dispersed phase and pure water as the continuous phase, where the continuous phase has lower boiling point. The second type consists of Novec 7200 as the dispersed phase and aqueous glycerin solution as the continuous phase, where the dispersed phase has lower boiling point. When incipient boiling occurs in the square capillary, bubble may appear in the bulk continuous phase, on the interface of the two phases or on the heating sidewall. For emulsion of small mass fraction, several bubbles tend to nucleate simultaneously on the heating sidewall of a square capillary. On the other hand, only a single bubble emerges during nucleation in a rectangular capillary and the bubble advancement leads to different contact angles between the interface and two sidewalls. When bubble expands longitudinally, the bulk emulsion is flushed away from the heating surface, leaving a thin liquid film on the sidewalls. From the results, we find that heat transfer rate of sulfated castor oil-in-water emulsion is always larger than that of pure water in a square capillary. When a small amount of sulfated castor oil is added to water, the superheat of incipient boiling is drastically augmented. Yet, superheat of incipient drops if the mass fraction of sulfated castor oil exceeds 0.001. Interestingly, the emulsion of refrigerant Novec 7200 in aqueous glycerin solution shows different boiling characteristics. We find that heat transfer rate deteriorates when a small amount of Novec 7200 is added to aqueous glycerin solution. Moreover, increasing the mass fraction of Novec 7200 leads to the decrease in superheat of incipient boiling. When the mass fraction of Novec 7200 is larger than 0.05, however, both heat transfer rate and superheat of incipient boiling remain independent of mass fraction. For emulsion of Novec 7200 in aqueous glycerin solution, smaller capillary leads higher superheats of incipient boiling.摘要 i Abstract iii 目錄 v 符號索引 vii 第一章 導論 1 1.1 前言 1 1.2 文獻回顧 2 1.2.1 乳化劑的沸騰性質 2 1.2.2 稀薄乳化劑 3 1.2.3 乳化劑中氣泡成長機制 4 1.3 研究動機 5 第二章 實驗量測架構與不確定性 7 2.1 實驗設備 7 2.1.2 毛細管元件 7 2.1.2 影像觀測系統 8 2.1.3 加熱裝置 8 2.1.4 資料擷取系統 9 2.1.5 工作流體 10 2.1.6 液滴大小量測 11 2.2 實驗量測步驟 13 2.3 不確定性分析 14 2.3.1 表面溫度 15 2.3.2 過熱溫度 15 2.3.3 熱通量 16 2.3.4 熱傳係數 16 2.3.5 質量分率 17 第三章 實驗結果與討論 18 3.1 乳化劑沸騰現象討論 18 3.1.1 加熱液滴之熱泳效應 18 3.1.2 加熱對液滴造成的影響 19 3.1.3 太古油乳化劑沸騰氣泡產生之位置以及氣泡之成長 19 3.1.4 冷凍液乳化劑沸騰氣泡產生之位置以及氣泡之成長 25 3.2沸騰曲線 29 3.2.1 質量分率對沸騰曲線之影響 29 第四章 結論與建議 35 4.1 結論 35 4.2 建議 365230118 bytesapplication/pdf論文公開時間：2015/08/11論文使用權限：同意有償授權(權利金給回饋學校)乳化劑液滴thesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/263160/1/ntu-103-R01522118-1.pdf