The function and principle of the downcomer, explained in simple terms
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The function and principle of the downcomer, explained in simple terms
In addition to facilitating the downward flow of liquid, the function of the downcomer is also to separate the gas in the foam within the downcomer, so that bubbles are not carried to the next tray and thus do not affect the mass transfer efficiency. Therefore, the liquid should have sufficient residence time in the downcomer to allow the gas to escape; generally, a residence time of more than 3–5 seconds is required. Generally, the overflow area accounts for no more than 25% of the total area of the tray; in cases with a large volume of liquid, this value can be exceeded.
Channels for the downward flow of the liquid phase, gas-liquid separation (to prevent mist entrainment, with a concept of clear liquid layer height), and establishment of a liquid seal (to prevent gas from rising through this path).
In addition to facilitating the downward flow of the liquid, the function of the downcomer is also to separate the gas in the foam within the downcomer
Function: Liquid descent. Principle: Gravity-driven descent. Design principle: Sufficient residence time is sufficient; everything else relates to economic considerations