DESALINATION www.elsevier.com/locate/desal Desalination 247 (2009) 594–609 Experimental and numerical investigation of humidification/ dehumidification solar water desalination systems Adel M. Abdel Dayem*, M. Fatouh Dept. of Mech. Power Eng., Faculty of Eng. (Mattaria), Masaken El-Helmia P. O. 11718, Cairo, Egypt email: adel_abdeldayem@hotmail.com & drmohfat@hotmail.com Received 5 July 2007; accepted 13 December 2008 Abstract In this work, a humidification–dehumidification process is considered as an advanced technique to design and construct a solar water desalination system. In this system, the salt water is heated in a solar collector before flash- ing inside an insulated chamber to be evaporated and condensed naturally later on where the rest of saline water is re-circulated into the system. Three systems are manufactured and tested in Cairo, 308N. The salt water is circu- lated in a separate loop for the first and second systems. In the first system, an auxiliary heater is used to switch the temperature of the salt water where it is naturally switched in the second system depending on the weather con- ditions. The third system is an open system in which the salt water is used as a collector fluid. In all three systems, a thermosyphon solar water heater is used as a heat source consisting of a collector and a storage tank. A numer- ical simulation was developed for the considered systems to predict their annual performance and desalinated water production. An agreement between the measured and simulated data was obtained. It is found that the third system is the most efficient one and it has the lowest cost. Moreover, the first one has the greatest distilled water with higher temperatures and flow rates. Keywords: Solar desalination; Humidification–dehumidification; Numerical simulation; Multi-effect 1. Introduction Over the past few decades, the solar energy was used for water desalination as a renewable and clean source of energy. Recently multi-effect humidification–dehumidification simultaneous process is used to desalinate the salt/brackish water by many scientists. In this process, the hot salt water is flashed inside an insulated chamber to evaporate the salt water in evaporator side (humidifier). A water-cooled condenser is used to condensate the vapor to distilled water in condenser side (dehumidifier) that is collected outside from the chamber as shown in Fig. 1. The fresh salt water can be used as the condenser fluid to be preheated before feeding into the system. The rest of saline water collected inside the cham- ber is still hot and is mixed together with the *Corresponding author. 0011-9164/09/$– See front matter Ó 2009 Elsevier B.V. doi:10.1016/j.desal.2008.12.039 Published by