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 the industrial scale downcomer are studied in the paper. The liquid backmixing and circular flow in downcomer are tested with the fluoro-tracer agent and the hot water tracer technique in a 1900mm and a 1200mm diameter simulator，respectively. The critical chocking liquid-loading intensity of downcomer is determined in a rectangle simulator, of which the length is 800mm and the width is 600mm. The results shows severe liquid backmixing in the downcomer with backmixing number are higher than 0.1 and the dimensionless variance are about 0.5. The liquid circular flow is observed in the middle of downcomer. It is also shown that the value of critical chocking liquid-loading intensity of downcomer is less than the value predicted by previous empirical correlation. The results obtained in the large-scale experimental apparatus should be more reliable than that in small-scale equipment. It can provide basic data for engineering design.