In this paper a family of new silica gel-calcium chloride composite adsorbents is presented for desiccant rotary wheel in dehumidification system. For these desiccants the water sorption equilibrium has been measured in a wide relative vapour pressure range. This experimental study shows that the vapour adsorption properties of the composites using calcium chloride as impregnated salt can be controllably modified by varying the amount of the salt inside the pores. The thermodynamic performance of such desiccant rotary wheel is analysed based on the adsorption equilibrium equations obtained through nonlinear regressions using fractal BET theory. The simulation results show that the new composite desiccants can be effectively used in a rotary wheel dehumidifier and to improve its performance, various optimum operational/system parameters have been identified. Copyright (C) 2005 John Wiley Sons, Ltd.