本研究以氧化矽為蝕刻遮罩，以DRIE在矽晶圓上製作內含人造孔穴之微流道，進行甲醇/水混合系統的流沸騰實驗，探討莫耳分率、流道寬度為100 m與150 m及人造孔穴對流沸騰型態的影響及單相流與二相流之壓力變化。甲醇/水為不具共沸點之混合系統，實驗中所使用之莫耳分率為0 (純水)、0.07、0.3、0.5、0.7、0.9與1 (純甲醇) 共七種，流體之體積流率設定為0.02 ml/min。實驗結果顯示由常溫加熱至完全汽化，主要出現三種流沸騰型態，所對應的過熱溫度由低至高依序為塊狀流 (slug flow)、環狀流 (annular flow) 與霧狀流 (mist flow)。
對於甲醇/水混合系統而言，增加甲醇莫耳分率會使表面張力下降，有助於氣泡在微流道中之流動，且氣液介面亦較平滑，可避免頸縮現象發生。對於普通流道而言，流道寬度對流沸騰型態之變化並不明顯；對於內含人造孔穴之流道而言，流道寬度縮小使沸騰初始之氣泡體積變小。而對於寬度為100 m之流道，放置人造孔穴亦可使沸騰初始之氣泡體積變小；對於寬度為150 m之流道，放置人造孔穴可改善slug flow型態之氣泡流動性，避免發生氣泡堆積現象。
流道型態固定時，在單相流中，溫度上升使工作流體性質改變，單相壓力隨系統溫度上升而降低。當甲醇莫耳分率x  0.5時，混合系統中之預溶氣體在過冷狀態即釋出，使壓力變大，提高甲醇莫耳分率會使沸騰初始及mist flow型態之壓力降低。莫耳分率固定時，放置人造孔穴可略為降低沸騰初始及完全進入mist flow型態時所對應之過熱溫度。
對於沸騰後的二相流壓力變化，利用實驗結果估算孔隙率 (void fraction)，以Lockhart-Martinelli模型與均質模型 (homogeneous model) 計算二相流之摩擦壓降，發現對於甲醇/水混合系統，莫耳分率為影響二相流中摩擦壓降的重要因素。當莫耳分率愈高，摩擦壓降與量測總壓降之差距愈小。

In this study, flow boiling of methanol/water mixtures in microchannel is investigated under isothermal heating condition. The mole fractions of methanol in water tested are 0 (pure water), 0.07, 0.3, 0.5, 0.7, 0.9 and 1 (pure methanol). The widths of the microchannels are 100 m and 150 m, while the depth and length are 150 m and 1.6 mm, respectively. The bottom surfaces of the microchannels are treated by DRIE to produce artificial cavities with a diameter of 12 m. A syringe pump is used to deliver the mixtures and the flow rate is set to 0.02 ml/min.
There are three typical boiling regimes identified: the slug flow, the annular flow and the mist flow. For methanol/water mixtures, increasing the mole fraction decreases the surface tension and results in smaller bubbles in slug flow. It also makes the liquid-vapor interface smoother to avoid the formation of necking instability in annular flow. Moreover, by adding artificial cavities to the microchannels, bubble sizes are reduced and the required superheats of boiling incipience and transition to mist flow are both decreased.
In general, the single-phase pressure drop in microchannel decreases with increasing the system temperature and increases eruptly after the initiation of phase change. For x  0.5, however, dissolved gases tend to release at subcooling condition, causing the pressure drop to increase before boiling incipience. Void fraction is estimated from experimental results to calculate the frictional pressure drop of two-phase flow by employing the Lockhart-Martinelli parameter and homogeneous model. It is found that the higher mole fraction the more significant contribution of the frictional pressure drop to the total pressure drop. For x  0.5, the frictional pressure drop proves to dominate the total pressure drop for two-phase flow in microchannels.

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