Abstract

Experiments of flow regime visualization and identification of air–water two-phase flow were conducted in a horizontal helically coiled rectangular channel. The test superficial liquid and gas velocities are 0.09–2 m/s and 0.18–16 m/s, respectively. Flow regimes were observed with a high-speed video camera and the corresponding local and average void fractions were measured with an electric conductivity probe method and with a quick-close valve method, respectively. Four main flow regimes including unsteady pulsating flow, bubbly flow, intermittent flow, and annular flow were observed. The bubbly flow identification criteria depend on more than 90% bubbles whose chord length was smaller than the channel equivalent diameter. The annular flow identification criteria is the local void fraction in the gas core larger than 0.97. Then the flow regimes and their transition mechanisms are analyzed. Furthermore, new transition criteria among these flow regimes have been proposed. The results show that the critical transition average void fraction from bubbly to intermittent flow is 0.23. A complete air–water flow regime map has been developed for the horizontal helically coiled rectangular channel and the map predicts the observed flow regimes well.

摘要

在水平螺旋盘绕的矩形通道中进行流态可视化和气水两相流识别实验。测试表观液体和气体速度分别为 0.09-2 m/s 和 0.18-16 m/s。用高速摄像机观察流态，并分别用电导率探针法和快速关闭阀法测量相应的局部和平均空隙率。观察到四种主要流态，包括非定常脉动流、气泡流、间歇流和环形流。气泡流识别标准取决于90%以上的气泡弦长小于通道等效直径。环流识别标准是气芯中的局部空隙率大于 0.97。然后分析了流态及其转变机制。此外，已经提出了这些流态之间的新过渡标准。结果表明，从气泡流到间歇流的临界过渡平均空隙率为 0.23。已经为水平螺旋盘绕的矩形通道开发了完整的空气-水流态图，该图很好地预测了观察到的流态。