Abstract
A solar powered desalination unit which is working on a humidifiation –dehumidifiation technique (HDH) is one of the most important techniques used in seawater desalination in remote and rural areas. It is easy to design, operate and maintain. In this paper, a theoretical study based on a design methodology for a solar assisted desalination unit working on a HDH principle under the prevailing conditions of TajouraLibya is carried out. Th main target is to study the effct of diffrent design and operating parameters that inflence the performance of the unit and its productivity under diffrent design scenarios; (spring, summer,autumn and winter). Results show that the productivity of the unit is increased with a corresponding increase in the inlet air mass flw rate to the solar air heater, inlet water mass flw rate to the humidifir and cooling water mass flw rate to the dehumidifir. A signifiant increase in the productivity of the unit is achieved when the initial water temperature and the initial mass of water inside the storage tank were increased. Moreover, Gained Output Ratio, GOR, values vary between (0.27 and 0.79) for winter and spring designs and (1.94 and 2.75) for autumn and summer designs respectively. In general, the productivity of the unit is estimated tobe within a range from a minimum of (2 ~ 4) kg/m2.day, in winter to a maximum of (10 ~ 12) kg/m2.day, in summer, which makes it very convenient for using in rural and remote areas.

Key words: desalination, humidifiation, dehumidifiation, GOR, solar air heater fresh water, HDH