A Theoretical and Experimental Study for A humidification-Dehumidification (HDD) Solar Desalination Unit
A humidification-dehumidification (HD) solar desalination unit was designed. It seems to be suitable to provide drinking water for population or remote arid areas. Solar water and solar air collectors were designed to provide the hot water and air to the desalination chamber. The desalination chamber was divided into humidifier and dehumidifier towers. The circulation of air in the two towers was maintained by the forced convection. Theoretical and experimental works were done at different environmental conditions. A mathematical model was formulated, in which the thermodynamic relations were used to study the flow, heat and mass transfer inside the humidifier and dehumidifier. Such a technique was performed in order to increase the unit performance. Heat and mass balance was done and a set of governing equations was solved using the finite difference technique. The solar intensity was measured along the working day during the summer and winter months and a comparison between the theoretical and experimental results were performed. The average accumulative productivity of the system in November, December and January was ranged between 2 to 3.5 kg / m day while the average summer productivity was found between 6 to 8 kg/m day in June and 7.26 to 11 22
SOLAR STILL PRODUCTIVITY ENHANCEMENT
The distilled water productivity of the single basin solar still is very limited. Some methods have to be developed to improve this productivity. Using black rubber or black gravel materials within a single sloped solar still as a storage medium is examined in this work. To study experimentally the effect of different parameters such as rubber thickness and gravel size under the same operating conditions, four identical still units are designed and constructed. The experimental results showed that black rubber (10 mm thick) improves the productivity by 20% at the conditions of 60 l/m2 brine volume and 15° glass cover angle. Also, using black gravel of 20–30 mm size improves the productivity by 19% at the conditions of 20 l/m2 brine volume and 15° of glass cover angle.
Experimental evaluation of a single-basin solar still using different absorbing materials
Single-basin solar stills can be used for water desalination. Probably, they are considered the best solution for water production in remote, arid to semi-arid, small communities, where fresh water is unavailable. However, the amount of distilled water produced per unit area is somewhat low which makes the single-basin solar still unacceptable in some instances. The purpose of this paper is to study the effect of using different absorbing materials in a solar still, and thus enhance the productivity of water. Experimental results show that the productivity of distilled water was enhanced for some materials. For example, using an absorbing black rubber mat increased the daily water productivity by 38%. Using black ink increased it by 45%. Black dye was the best absorbing material used in terms of water productivity. It resulted in an enhancement of about 60%. The still used in the study was a single-basin solar still with double slopes and an effective insolation area of 3 m2.