This article presents a research study on the process analysis of adiabatic liquid desiccant dehumicification/regeneration with slug flow assumptions. A controlling equation is developed for the quasi-equilibrium processes where the two fluid streams are in contact in quasi-equilibrium conditions. Results from this equation with numerical integration for the solution are presented as process curves on a psychrometric chart. Two of these curves are found to be characteristic of two typical types of adiabatic dehumidification/regeneration processes: one featured with small enthalpy change of air and low mass flow of solution (type-1) and the other with small concentration change and high mass flow of solution (type-2). These two types of process curves are thus named as characteristic process curves. Numerical simulations of one-dimensional heat and mass transfer model under practical conditions were also performed. With special inlet conditions and approximately balanced heat and mass capacity conditions, the loci of states for the two fluid streams will still proceed approximately along the same characteristic process curves. Under other inlet conditions, the characteristic process curves still function as asymptotic limits for the real processes. Thus, the research presented in this article provides an in-depth understanding of the complicated heat and mass transfer processes and also a theoretical basis for further development of simplified and precise enough algorithm of heat and mass transfer calculations. (c) 2005 Elsevier Ltd. All rights reserved.