Solar desalination based on humidification process - I. Evaluating the heat and mass transfer coefficients

Solar desalination with a humidification-dehumidification process has prove n to be an efficient means of utilizing solar energy for the production of fresh water from saline or sea water. The process used in this work is a cl osed air cycle type, in which air is circulated in the unit by natural draf t between the humidifier and condenser. In order to scale up a unit of this type, it is necessary to obtain suffici ent information on the process of heat and mass transfer in the unit. The h umidifier and the condenser had to be specially designed to maintain minimu m pressure drop in the unit, The mass transfer coefficient in the humidifie r was found to be affected mostly by the water flow rate due to its effect on the wetting area of the packing. In natural draft operation, the air cir culation rate was found to increase with water flow rate, causing a further increase in the mass transfer coefficient. It was possible to predict and correlate the mass and heat transfer coefficients in the humidifiers and co ndensers, having different designs, in the three units constructed by us in Jordan and Malaysia. (C) 1999 Elsevier Science Ltd. All rights reserved.