The width of the downcomer is not equal to the width of the liquid receiving tray
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Under what circumstances can the width of the downcomer be different from the width of the liquid receiving tray in a single overflow tray?
The liquid that overflows from the tray into the downcomer contains a significant amount of gas; it is necessary to separate this gas from the liquid within the downcomer, otherwise it will affect the separation efficiency of the tray. Is this the reason behind such a design, in order to facilitate vapor-liquid separation? Personal opinion.
When no liquid seal is formed in the downcomer, that is, when air enters the system, the width of the downcomer is not equal to the width of the liquid receiving tray.
If designed as an inclined downcomer, the width of the liquid receiving tray (flat or concave type) is generally slightly wider than the width of the downcomer outlet. If it’s not due to design reasons – namely, the absence of an inlet weir – then it is usually because the vapor-liquid velocity ratio is too high, resulting in air entrainment (no liquid seal present). PS: This is just my personal opinion