A UNIFIED MODEL FOR COUNTERCURRENT VAPOR LIQUID PACKED-COLUMNS .1. PRESSURE-DROP

A model for the two-phase pressure drop in a packed column is developed from percolation concepts. Specifically, the macroscopic ''flood'' point for countercurrent liquid/vapor flow in a packed column is assumed to play the identical role that the incipient percolation threshold plays for the conductor/insulator transition on an electrical lattice. The flow passages making up the void space of the packing are taken to be ''conducting'' when they are open to vapor flow and ''insulating'' when they are choked off by liquid (i.e., localized flooding). The Wallis equation, developed to describe flooding for countercurrent flow in vertical tubes, is used to describe the flood point in the column. By an appropriate renormalization to the ''flood'' point, a simple equation for the pressure drop is derived.