Heat and mass transfer between air and falling solution film in a cross flow configuration is investigated. Effects of addition of Cu-ultrafine particles in enhancing heat and mass transfer process are also examined. A parametric study is employed to investigate the effects of pertinent controlling parameters on dehumidification and cooling processes and their subsequent optimization. It is found that low air Reynolds number enhances the dehumidification and cooling processes. An increase in the height and length of the channel and a decrease in the channel width enhance dehumidification and cooling processes. It is also found that an increase in the Cu-volume fraction increases dehumidification and cooling capabilities and produces more stable Cu-solutions. (C) 2003 Elsevier Ltd. All rights reserved.