Performance study of the capillary film solar distiller

The solar stills are used to produce fresh water from sea and brackish water by using direct solar radiation. However, these stills represent the best technical solution to supply remote villages or settlements with fresh water without depending on high technology and expertise. In the south of Algeria, water resources (underground and geothermal) are available, but water has a salinity of 2-4 g/l. To supply sufficient fresh water for the population, desalination becomes necessary. This paper presents the results of experiments carried out with a capillary film distiller installed in the south of Algeria (in a village near Touggourt where the temperature of the groundwater is about 65 degrees C at the source) for groundwater distillation and to improve the efficiency of the capillary film solar distiller using solar energy and the capillary effect. This type of distiller, called DIFICAP (DIstiller with a FIlm in CAPillary motion) was designed and patented by R. and C. Ouahes and P. Le Goff [1]. A very thin layer of tissue with fine mesh, saturated with water, it maintains itself at contact with a metal plane due to the surface tension which is much greater than the gravitational forces. This plate acts as an evaporator-condenser. In its three-stage version, the DIFICAP is composed of three identical evaporation-condensation cells in thermal series. The heat dissipated by the condensation of steam on the metal plane is used on the back face of the plane for the evaporation of an equivalent quantity of water. Solar energy is thus used three times in succession. The difference in temperature between plates in each cell is 5-10 degrees C. It was found that the efficiency of this distiller increased with increasing the temperature of the brackish water at the inlet and also with increasing the intensity of the solar radiation. It depends also on the heat loss and fabric used. Also, the efficiency can be increased and the cost decreased if the plant works all day long. This requires a large amount of heat storage.