Study on Slug Characteristics of Air-water Two-phase Flow in Horizontal Narrow Rectangular Channel
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摘要: 气弹速度和液膜厚度作为弹状流工况下的关键参数，在传热分析和力学分析中具有重要意义。本文以空气-水为介质，采用高速摄影机和印刷电路板式（PCB）液膜厚度传感器，对高1.9 mm×宽68 mm的水平窄矩形通道内气弹运动特性进行研究。液相雷诺数（Rel）<2500，矩形通道内为层流区；Rel≥2500，矩形通道内为湍流区，基于气-液两相混合速度分别拟合了气弹运动速度的预测关系式，结果表明，层流区分布系数（C0）可采用Ishii 关系式计算且漂移速度为0；而湍流区C0为1.0。当气弹雷诺数（Reb）<3100时，气弹底部液膜厚度（δb）随毛细管数的增大而增大；而在Reb≥3100时，δb表现出波动性。现有的δb预测关系式不适用于窄矩形通道，在考虑通道高宽比的影响下提出了一个新的δb预测关系式，对文献中210个数据进行了验证，预测误差均在±20%内。Abstract: As the key parameters of slug flow, slug velocity and liquid film thickness are of great significance in heat transfer analysis and mechanical analysis. In this paper, the characteristics of slug in a horizontal narrow rectangular channel with 1.9 mm×68 mm are studied by using high-speed camera and PCB liquid film sensor. For liquid Reynolds number
${{Re}}_{\text{l}}\text{ < 2500}$ ) , the rectangular channel is a laminar area; For Rel≥2500, the rectangular channel is a turbulent area. Based on the gas-liquid two-phase mixing velocity, the predictive relation of slug velocity is fitted respectively. The results show that the laminar area distribution coefficient (C0) can be calculated by Ishii equation and the drift velocity is 0; the turbulent area C0 is 1.0. For slug Reynolds number Reb<3100, the liquid film thickness (δb) at the bottom of slug increases with the increase of capillary number; For Reb≥3100, δb shows volatility. Existing δb predictive relation is not applicable to narrow rectangular channels. Considering the influence of channel aspect ratio, a new δb predictive relation is proposed to verify 210 data in the literature, and the prediction errors are all within ±20%. -
图 7 气弹液膜厚度随毛细管数的变化
Figure 7. Variation of Slug Liquid Film Thickness with Capillary Number
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