Hydro-Dynamic Characteristics of Gas-Liquid Two-Phase Flow in Ultra-Small Capillary Tubes

空气-水和蒸汽-水两相流动特性已经使用由二氧化硅或石英制成的20、25、50、80和100微米管进行了直观观察。在本工作中使用的光学系统包括一个可以将图像放大150倍的显微镜、一个高速摄像机和一台个人电脑。整个系统的空间分辨率为0.4微米。从目前的工作中得出以下结论。1)在直径小于100微米的微通道中，可观察到气泡流、段塞流、液块流、液环流、环膜流和雾状流等多种两相流形态。具体来说，液体环流是我们的新发现之一。2)微通道中两相流的主要影响因素是表面污染和润湿性等表面条件。一个非常有趣的观察结果是，在一个经过物理和化学处理的非常干净的系统中，几个气体段塞通过一个气体杆连接起来，就像“烤鸡肉”一样。我们将这种新发现的两相流模式命名为串状段塞流。3)提出了20微米管的两相流型转换图。4)通过Armand关联和修正Chisholm关联，证实了剖面平均孔隙率和压降具有较好的相关性。5)在实验观察和数值模拟的基础上，提出了考虑气泡间两种作用力的气泡动力学模型。

Air-water and steam-water two-phase flow characteristics have been observed visually using 20, 25, 50, 80 and 100 microns i. d. tubes made of either silica or quartz. The optical system used in the present work consists of a microscope magnifying the images up to 150 times, a high-speed video camera and a personal computer. The spatial resolution of the whole system was 0.4 microns. Following conclusions have been drawn from the present work.1) More than several two-phase flow patterns were observed in micro-channels of diameter smaller than 100 microns, including bubbly, slug, Iiquid lump flows, Iiquid ring, annular film, and mist flows. Specifically, the liquid ring flow is one of our new findings.2) It has been confirmed that surface conditions such as surface contamination and the wettability are dominant effects in two-phase flows in micro channels. A very interesting observation is That, in a very clean system both physically and chemically treated, several gas slugs were connected by a gas stem just like "Yakitori". We named this newly found two-phase flow pattern as skewered slug flow.3) We proposed a two-phase flow pattern transition map for a 20-micron tube.4) It has been confirmed that the cross-sectional average void fraction and pressure drop are well Correlated by the Armand correlation and the modified Chisholm correlation, respectively.5) Based on our experimental observation and numerical simulation, we have proposed a bubble dynamic model taking into account two interaction forces exerting between the bubbles.