How are the weir height of the overflow weir and the bottom gap height of the downcomer determined?
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When calculating the height of the gap at the bottom of the downcomer, it is always higher than the height of the weir; this happens every time I try it. The documentation states that in order to ensure a liquid seal, the height of the gap at the bottom of the downcomer should be lower than the height of the outlet weir, generally not less than 6 mm. How can this be changed? What’s the problem? Last edited by Drifting in the north on 2009-1-6 14:43]
The bottom gap can be higher than the height of the overflow weir; if there is concern about gas flowing back into the downcomer, no valve openings are provided near the outlet of the downcomer. If not, can the overflow weir be raised? Using an inclined-hole tray outlet eliminates the need for an overflow weir. There is also the option of using an arc-shaped liquid receiving tray, which can increase the clearance at the bottom of the downcomer as well; however, it is best that the liquid medium does not contain any impurities that could settle.
I’m working on the design for chemical engineering principles; thank you all