A solar desalination system using humidification–dehumidification process: experimental study and comparison with the theoretical results

In this study, influence of the different system operating conditions on the performance of a solar desalination system using humidification-dehumidification process have been investigated experimentally under the climatological conditions of Ankara (40°N, 33°E), Turkey. An experimental set-up that consists of a double-pass flat plate solar air heater with two glass covers, pad humidifier, dehumidifying exchanger and water storage tank was designed and manufactured. Working principle of the set-up is based on the idea of closed water and open-air cycles. A series of tests were performed on it in outdoor environment, in order to assess the effect of mass flow rate of the feed water, process air and cooling water, double-pass flat plate solar air heater, initial water temperature and amount of the water inside the storage tank on the productivity of the system. Additionally, an evacuated tubular solar water heater unit was integrated to the existing system and the effect of this integration on the performance of the system was examined. Solar radiation, wind speed, relative humidity, mass flow rate of the feed water, process air and cooling water, mass of condensate water and temperatures at various locations were obtained during the experiments.

The results of the experimental study showed that under certain operating conditions, the system productivity decreases about 15% if double-pass solar air heater is not used and significant improvement on the productivity of the system is achieved by increasing the initial water temperature inside the storage tank. In addition, productivity of the system increases with increasing the feed water mass flow rate and quantity of water inside the storage tank. However, productivity of the system remains approximately the same when the air mass flow rate is increased. Moreover, increasing the cooling water mass flow rate results in the improvement on the productivity of the system investigated. Finally, results obtained from the present investigation were compared with the theoretical study and a good agreement between them is observed.