Studies On The Characteristic Of Two-Phase Flow In Rolling Tubes

The two-phase flow pattern,pressure drop and void fraction in rolling and steady condition through vertical tubes were researched experimentally in this dissertation.All the experiments were achieved in a rolling test facility. Air and water were used as flowing medium at atmospheric pressure and temperature. Tubes of three different inside diameters: 15 mm, 25 mm and 34.5 mm were used separately and all of them were 5 m long smooth glass tubes. During the experiments, depending on pressure differential fluctuation method and visual observation, the onset of bubble flow and annular flow can be got; based on separated two-phase flow model and qualitative analysis, the turning point of inside pressure difference curve is just the point where the churn flow takes place. Pressures were measured by differential pressure transmitter and void fractions were measured by fast globe valve. All of the variable were timely collected and recorded by computer accumulation system in the experiment.First, the classification of flow pattern was setting through experimentobservation and data handling. Flow pattern map were drawn and compared. The differences of flow pattern transition were explained rationally.Then, the total pressure drop in rolling and steady condition through vertical tubes was given out on the base of experiment. Based on the visual observation and the analysis of experimental data, it was found that flow patterns with rolling motion were different from that of steady condition. Comparing with the steady condition, the pressure change in the region of slug flow,bubble flow and annular flow were showed obviously cyclical variation, but this periodic fluctuation phenomenon was not found in churn flow. Meanwhile, the influence of rolling angle and rolling period were analyzed.Finally, the half empirical formula was given out through analyzing the influence of void fraction and combining experimental data. Based on the experiment, the influence of rolling angle and rolling period were also analyzed.