Channeling in Packed Columns :
The tendency of the liquid to segregate towards the walls of a packed column and to flow along the walls (a region of the greatest void space) is termed as channeling, which leads to low mass transfer efficiencies. Thus, with a good initial liquid distribution in randomly packed columns, channeling can be minimised by providing a tower diameter to packing size ratio greater than 8, i.e., the diameter of the tower should be at least eight times the packing size (or the packing size smaller than at least one-eighth of the tower diameter).
In packed columns, the region of greatest void space is the region near the wall of the column since the packing material cannot nest tightly with the plane wall as it does with itself. It is a natural tendency for the fluid to move toward the region of greatest void space during its flow.