Study on Two-phase Flow in Tray Downcomer - Backmixing and Choking Tests

摘要

To decide the upper limit of tray downcomer, characteristics of V-L two-phase flow in thernindustrial scale downcomer are studied in the paper. The liquid backmixing and circular flow inrndowncomer are tested with the fluoro-tracer agent and the hot water tracer technique in a 1900mm and arn1200mm diameter simulator ,respectively. The critical chocking liquid-loading intensity of downcomer isrndetermined in a rectangle simulator, of which the length is 800mm and the width is 600mm. The resultsrnshows severe liquid backmixing in the downcomer with backmixing number are higher than 0.1 and therndimensionless variance are about 0.5. The liquid circular flow is observed in the middle of downcomer. Itrnis also shown that the value of critical chocking liquid-loading intensity of downcomer is less than thernvalue predicted by previous empirical correlation. The results obtained in the large-scale experimentalrnapparatus should be more reliable than that in small-scale equipment. It can provide basic data forrnengineering design.