Adiabatic two-phase flow in rectangular microchannels with different aspect ratios: Part I – Flow pattern, pressure drop and void fraction
Adiabatic two-phase flow in rectangular microchannels with different aspect ratios: Part I – Flow pattern, pressure drop and void fraction
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DOI：
10.1016/j.ijheatmasstransfer.2010.07.067
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发表时间：
2011-01
影响因子：
5.2
通讯作者：
Chiwoong Choi;D. Yu;M. Kim
中科院分区：
文献类型：
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作者：
Chiwoong Choi;D. Yu;M. Kim
矩形微通道内两相流的高宽比是一个重要的参数。为了研究矩形微通道内高宽比对两相流流型、压降和含气率的影响，进行了矩形微通道内绝热液态水和氮气两相流的实验研究。矩形微通道的宽度和高度分别为510μm×470μm、608μm×410μm、501μm×237μm和503μm×85μm。因此，矩形微通道的深宽比分别为0.92、0.67、0.47和0.16;矩形微通道的水力直径分别为490、490、322和143μm。实验范围为液体表观速度0.06-1.0m/s，气体表观速度0.06- 71 m/s。可见的矩形微通道，使用光敏玻璃制造。并通过嵌入式端口直接测量微通道内的压降。使用高速相机和远距离显微镜对流动模式进行可视化。在本研究中观察到的矩形微通道中的典型流动模式是泡状流、过渡流（多股流）和液环流。随着高宽比的减小，由于约束效应，气泡流区逐渐占主导地位，拐角处的液膜厚度减小。矩形微通道中的空隙率与体积质量具有线性关系。由于液膜厚度的减小，两相流随着长径比的减小而趋于均匀。就像张等人s [19]相关性，随着禁闭数的增加，Lockhart-Martinelli相关性中的C值减小。矩形微通道内的摩擦压降与流型密切相关。
An aspect ratio is an important parameter for two-phase flow in a rectangular microchannel. To study the aspect ratio effect on the flow pattern, pressure drop and void fraction, experiments of adiabatic liquid water and nitrogen gas two-phase flow in rectangular microchannels were conducted. The widths and heights of rectangular microchannels are 510μm×470μm, 608μm×410μm, 501μm×237μm and 503μm×85μm. Therefore, the aspect ratios of the rectangular microchannels are 0.92, 0.67, 0.47 and 0.16; and the hydraulic diameters of the rectangular microchannels were 490, 490, 322 and 143μm, respectively. Experimental ranges were liquid superficial velocities of 0.06–1.0m/s and gas superficial velocities of 0.06–71m/s. Visible rectangular microchannels were fabricated using a photosensitive glass. And pressure drop in microchannels was directly measured through embedded ports. The visualization of the flow pattern was carried out with a high-speed camera and a long distance microscope. Typical flow patterns in the rectangular microchannels observed in this study were bubble flow, transitional flow (multiple flow) and liquid ring flow. As the aspect ratio decreased, the bubble flow regime became dominant due to the confinement effect and the thickness of liquid film in corner was decreased. A void fraction in the rectangular microchannels has a linear relation with the volumetric quality. And the two-phase flow becomes homogeneous with decreasing aspect ratio owing to the reduction of the liquid film thickness. Like Zhang et al.’s [19] correlation, as the confinement number increased, the C-value in Lockhart and Martinelli correlation decreased. And a frictional pressure drop in the rectangular microchannels was highly related with the flow pattern.