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題名 | Flow Patterns Identification of Refrigerant R-134a in Horizontal Evaporator Tubes by Pressure Measurement=以管壁壓差探討水平蒸發管中冷媒R-134a的流場型態 |
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作者姓名(中文) | 游明輝; 林存國; 郭心田; | 書刊名 | 中國機械工程學刊 |
卷期 | 20:2 1999.04[民88.04] |
頁次 | 頁129-137 |
分類號 | 446.641 |
關鍵詞 | 管壁; 壓差; 水平蒸發管; 冷媒; 流場; Two-phase flow patterns; Pressure fluctuation measurement; Horizontal evaporator tubes; |
語文 | 英文(English) |
中文摘要 | 本研究以實驗的方法探討冷媒R-134a在水平蒸發管中的流場型態,其方法為量 測測試段上下管壁的壓差振盪,以壓力振盪的機率密度函數探討水平蒸發管中R-134a冷媒 的流場型態。實驗的進行是在不同質量流率,乾度和內管壁粗造度(平滑管和微鰭管),管壁 均勻加熱量下,量測非透明管測試段的上、中、下游的管壁振盪壓差,以判別上、中、下游 管內的流場型態,最後以流場型態圖表示平滑管和微鰭管流場變遷情況。本實驗的質通量範 圍介於46至110kg/m□s,乾度範圍介於0.02至0.80實驗結果顯示在低質通量下,微鰭管 由於表面張力的影響,上游為環狀流,下游為分離流;平滑管則上至下游全為分離流。在高 質通量下,兩種管在相同加熱量下的流場皆為由分離流發展為環狀流。此外,加熱量愈大, 流場變遷愈快發生。 |
英文摘要 | The two-phase flow patterns of refrigerant R-134a in horizontal evaporator tubes are investigated experimentally. Differential pressure fluctuations between the top and bottom of the test tube cross-section are measured. The probability density function of the pressure fluctuation is then used to identify the flow pattern at the measurement section. The experiment is carried out at various mass flow rates and vapor qualities in opaque evaporator tubes with and without surface roughness. For each test tube, pressure measurements are made at the upstream, middle, and downstream locations for observation of flow pattern transition during constant heating. Flow patterns are summarized in a flow map for both smooth and micro-fin tubes, hi the operating range of mass flux between 46 to 110 kg/m□s, and of vapor quality between 0.02 to 0.80, it is found that in micro-fin tubes annular flow is observed upstream, and switch to separated flow downstream at low mass flux where surface tension is relatively important, while at the same mass flux in a smooth, tube separated flow dominates from upstream to downstream. At high mass flux the two-phase flow in both types of the tubes is initially in separated flow pattern and develops into an annular flow pattern under constant heating. The larger the heating rate is, the sooner the transition occurs. |
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