Tenth International Water Technology Conference, IWTC10 2006, Alexandria, Egypt 227 THEORETICAL AND EXPERIMENTAL STUDY OF A SMALL UNIT FOR WATER DESALINATION USING SOLAR ENERGY AND FLASHING PROCESS A. Safwat Nafey a,* , M. A. Mohamad b , S.O. El-Helaby a , and M. A. Sharaf a a Dept. of Engineering Science, Faculty of Petroleum and Mining Engineering, Suez Canal University, Suez, Egypt * Tel.:+20-62-3303560; Fax: 20-62-3366252, E-mail: swazy20@hotmail.com b Solar Energy Department, National Research Center, Cairo, Egypt ABSTRACT A small unit for water desalination by solar energy and flash evaporation process is investigated. The system is built at the Faculty of Petroleum and Mining Engineering at Suez-Egypt. The system consists of a solar water heater (flat plate solar collector) working as a brine heater, and a vertical flash unit which is attached with a condenser/preheater unit. In this work, the system is investigated theoretically and experimentally at different real environmental conditions along Julian days of one year. A mathematical model is developed to calculate the productivity of the system under different operating conditions. BIRD model for the calculation of solar insolation is used to predict the solar insolation instantaneously. Also the solar insolation is measured by a high sensitive digital pyranometer. Comparison between the theoretical and experimental results is performed. The system is tested during the summer and winter months. The average accumulative productivity of the system in November, December and January raged between 2.5 to 3.5 kg/day. The average summer productivity ranged between 13 to 16 kg/day in July and August and 10 to 12 kg/day in June. Keywords: Desalination; Flash unit; Solar water heater; Solar energy INTRODUCTION Global resources of fresh water are scarce, unevenly distributed and, in many cases, may require some form of treatment and handling. These limited resources have resulted in water shortages in 88 developing countries across the world containing 50% of the world's population [1]. Need for purification of saline water is increasing due to an increase of population and limited supply of potable water. Using solar energy is a practical method for obtaining small amounts of fresh water from saline water. Solar water distillation has been a subject of great interest for several decades [2]. The standard techniques like multi stage flash, multi effect distillation, vapor compression and reverse osmosis are reliable for large capacity