Hanging Downcomer From The Liquid Seal

Suspended downcomers of tray should be self-sealed in order to prevent vapor from ascending through bottom holes of downcomers. Tray efficiency would be reduced when vapor ascends through the downcomer. A self-seal line was needed in the hydraulic performance diagrani of tray. It was conservative that almost no vapor was allowed to ascend from the downcomer in the previous self-seal correlation. The range of satisfactory operation would be shrunk when the previous self-seal correlation was used in the tray design. The effect of self-seal on the tray efficiency was studied in this thesis. New self-seal condition was determined in the experiments. Experiments were carried out in a 300x200 plexiglass column in air-water system. Gas-leaking frequency used in self-seal curve was I time per second. Self-seal curve was determined. The effects of the downcomer bottom area., liquid density and vapor density on the self-seal curve were also studied in the thesis. Gas-leaking model was established. The effect of the gas-leaking on the tray efficiency was derived. After calculating, gas-leaking in new self-seal curve would reduced the tray efficiency by O.0262%-O.0728%. Liquid fluctuation and gas-leaking mechanisms were studied and ensured by experiments. The orifice-flowing coefficient and liquid hold-up ratio of the bottom hole of the downcomer were tested. The results showed that the range of satisfactory operation was enlarged using new self-seal correlation in tray design. When the ratio of vapor density to the liquiddensity (p Li / p L) increased, the essential self seal liquid-nowing reSistance(ha) wasincreased con.espondingly.