臺灣博碩士論文加值系統

本研究主旨探討含油濃度及低壓冷媒R-245fa應用於滿液式、滴淋式兩種蒸發器之熱傳性能分析。工作流體為R-245fa，使用圓管打孔進行滴淋蒸發實驗，測試飽和溫度為20oC與5oC，使用之潤滑油為EMKARATE RL -150S，含油濃度為1%、2%與5％，測試管分別為光滑管及60FPI的鰭片管，鰭片高為0.4mm，改變熱通量範圍為6~50kW/m2，流量範圍為0.012~0.04kg/ms。
結果顯示，在純冷媒實驗中，鰭片管在任一飽和溫度下，滴淋蒸發的熱傳性能較池沸騰高。R-245fa之池沸騰性能與R-123冷媒相近，為極佳的冰水機替代冷媒。在含油冷媒實驗中，光滑管應用於池沸騰時，熱傳性能隨著含油量的增加而下降，而應用於滴淋蒸發時，則是在低熱通量時熱傳性能佳，而高熱通量則是略為下降；鰭片管則是無論何種機制，熱傳性能皆是呈現隨含油率增加而上升。因此，含油率對於熱傳性能之影響隨測試管的表面結構不同而異，而在滴淋蒸發時，測試管的位置可影響滴淋狀態而成為主要因素之一。本實驗之薄膜蒸發熱傳係數之預測值其誤差皆在±20%以內；含油冷媒熱傳係數修正公式之預測值誤差在±35%以內。

This study investigates the evaporation heat transfer performance of R-245fa and R-245fa with lubricant RL -150S mixture (1%, 2% and 5% lubricant mass fraction) in pool boiling and falling film. Two kinds of tubes, a smooth tube and a fin tube of 0.4mm fin height, 60FPI(Fins Per Inch) were tested. Experiments were performed at saturation temperatures of 5, 10 and 20oC. The liquid flowed through a liquid feeder with a row of circular holes at a rate of 0.012 ~ 0.04kg/ms, and heat fluxes varied from 6 to 50kW/m2.
For pure refrigerant, the results show that falling film heat transfer coefficient is better than pool boiling with fin tube. The heat transfer coefficient of R-245fa is similar to R-123. Hence, R-245fa is a good refrigerant to replace R-123. For pool boiling in R-245fa-oil mixtures, different results are shown in smooth and fin tube. The heat transfer coefficient of smooth tube decreases with increasing oil concentration. The smooth tube has a greater heat transfer coefficient at low heat flux than in falling film, but the performance slightly decreases at high heat flux. The fin tube has the same tend in pool boiling and falling film, the heat transfer coefficient increases with increasing oil concentration. The performance of refrigerant-oil mixtures depends on the tube surface structure. For falling film evaporation, the falling fluid flow pattern depends on tube location. Hence, the tube location is an additional factor on performance. A heat transfer correlation of falling film evaporation on smooth tube, which predicts the data in this study within

摘 要 i
ABSTRACT ii
第一章 緒論 1
1.1 研究背景 1
1.2 研究動機與目的 1
第二章 文獻回顧 2
2.1 池沸騰理論 2
2.1.1 結構表面之沸騰原理 2
2.1.2 商用之結構表面 2
2.1.3 氣孔大小與氣孔袋口效應的影響 3
2.1.4 表面下渠道(Tunnel)之影響 5
2.1.5 結構表面之核沸騰理論分析 6
2.2 薄膜蒸發理論 9
2.2.1 水平圓管外之滴淋薄膜蒸發 9
2.2.2 滴淋流場 10
2.2.3 滴淋熱傳 13
2.2.4 測試管種類及排列位置 15
2.3 含油濃度 17
2.3.1 冷凍油性質對於熱傳性能之影響 17
2.3.2 冷凍油濃度對熱傳性能之影響 18
2.3.3 含油濃度量測方法 20
2.3.4 冷媒與冷凍油之混合性 22
2.4 R-245fa應用 23
2.4.1 R-245fa特性 23
2.4.2 R-245fa冷媒於冰水主機之應用 24
第三章 實驗設備與方法 31
3.1 實驗系統 31
3.1.1 實驗腔體 32
3.1.2 滴淋分配管 33
3.1.3 測試管 34
3.1.4 冷凝循環 36
3.1.5 抽真空、高壓空氣、工作流體填充及除氣過程 36
3.1.6 資料與影像擷取系統 36
3.2 實驗參數設定 37
3.2.1 測試管表面參數 39
3.3 量測儀器 41
3.3.1 壓力轉換器 41
3.3.2 流量計 41
3.3.3 微齒輪泵 41
3.3.4 熱電偶 41
3.3.5 電源供應器 42
3.3.6 多功能電表 42
3.3.7 真空泵浦 42
3.3.8 濃度折射計 42
3.4 實驗步驟 42
3.5 實驗數據分析 45
3.5.1 熱通量計算 45
3.5.2 測試管表面壁溫計算 45
3.5.3 熱傳係數計算 46
3.5.4 薄膜雷諾數計算 47
3.6 誤差分析 48
3.6.1 溫度校正 48
3.6.2 濃度折射計校正 49
3.6.3 熱傳係數誤差分析 51
第四章 實驗結果與討論 54
4.1 純冷媒實驗分析 54
4.1.1 池沸騰之熱傳性能分析 54
4.1.2 薄膜蒸發之熱傳性能分析 55
4.2 含油冷媒實驗分析 57
4.2.2 含油冷媒之池沸騰熱傳性能分析 58
4.2.3 薄膜蒸發之熱傳性能分析 59
第五章 結論及未來展望 101
參考文獻 103
符號說明 106

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