“…In this case, a single macro-scale equation for describing the liquid phase flow is very difficult to develop. Models with a splitted liquid phase, i.e., one macro-scale equation for the gas phase but two macro-scale equations for the liquid, have been proposed to handle such cases [60][61][62]. In this framework, one has a balance equation for the gas phase (a single effective phase is enough in the context of structured packings so far), γ, and two balance equations for liquid phase part 1, β 1 , and liquid phase part 2, β 2 .…”