Solar desalination with a humidification-dehumidification cycle: performance of the unit

The closed air cycle humidification-dehumidification process was used for water desalination using solar energy. The circulated air by natural or forced convection was heated and humidified by the hot water obtained either from a flat plate solar collector or from an electrical heater. The latent heat of condensation was recovered in the condenser to preheat the saline feed water. Two units of different sizes were constructed from different materials. The productivity of these units was found to be much higher than those of the single-basin stills. Moreover, these units were capable of producing a large quantity of saline warm water for domestic uses other than drinking. No significant improvement in the performance of the desalination units was achieved using forced air circulation at high temperatures. While at lower temperatures, a larger effect was noticed. This can be related to the low heat and mass transfer coefficients at low temperatures and to the non-linear increase in the water vapor pressure with temperature.