Effect of the shape of equilibrium adsorption isobar on dynamics of water adsorption/desorption under isobaric stages of a basic cycle of an adsorption heat transformer has been studied. Selective water sorbent SWS-1L (CaCl2 confined to mesoporous silica gel) was used for these tests as its water adsorption isobars have segments with both convex and concave shapes. From these experiments the conclusion has been drawn that the dynamics of adsorption on a single adsorbent grain is closely linked with the shape (convex or concave) of the segment of water adsorption isobar between initial and final temperatures of the isobaric process. In particular, under the same boundary conditions desorption is faster than adsorption for a concave isobar segment and vice versa for a convex one. (C) 2008 Elsevier Ltd. All rights reserved.