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

Abstract

Solar desalination with a humidification–dehumidification process has proven 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 closed air cycle type, in which air is circulated in the unit by natural draft between the humidifier and condenser. In order to scale up a unit of this type, it is necessary to obtain sufficient information on the process of heat and mass transfer in the unit. The humidifier and the condenser had to be specially designed to maintain minimum pressure drop in the unit. The mass transfer coefficient in the humidifier 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 circulation 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 condensers, having different designs, in the three units constructed by us in Jordan and Malaysia.