However, the bubbling up vapor flows just through the downcomer bottom-orifices. The vapor occupies the part the of orifice area, so the orifice area for liquid descending is reduced and the downcomer liquid height increases which causes a premature downcomer flood as well. Moreover, the orifice area for liquid descending will be reduced further because bridging occurs, accompanied by vapor bubbling, with the area ratio of bridging being 0.4ยฑ1.8 of the area ratio of vapor bubbling. Therefore, the bubbling vapor rate and also the ratio of bridging are restricted for the sealed hangingdowncomer.
5 Conclusions
There are three states of (liquid descending, bridging, and vapor bubbling) at hanging downcomer bottom-orifices. Momentary variations in P i cause the occurrence of the three states. The three states are affected by superficial F-factor and liquid rate. The time and area ratios of bridging and vapor bubbling increase with increasing F-factor, and decrease with increasing liquid rate. Bridging really exists and is not negligible. The ratio of bridging is 0.4ยฑ1.8 of the ratio of vapor bubbling. Moreover, due to bridging, the bubbling vapor rate and also the ratio of bridging is restricted for the sealed hanging-downcomer.