A model is established to analyze the heat and moisture transfer process in air-water or - hydroscopic solution system

two independent driving forces each other: enthalpy difference and relative humidity difference can be obtained. A triangle region

consisting of iso-enthalpy line from air inlet

saturation line of moisture air(iso-concentration line of solution)and connecting line of air and water or solution at inlet status

is determined in enthalpy-psychrometric chart based on relationship between the two driving forces. The region is a reachable handling region for heat and moisture transfer process in air-water or-hydroscopic solution system

because the variation of air outlet status is limited in the region whatever change of mass and heat transfer coefficients or flow pattern and rate. Experimental results of dehumidification and regeneration in literatures are analyzed with the help of reachable handling region.