An experimental investigation of hybrid desalination system using Humidification–Dehumidification process integrated
with RO unit, evacuated tube solar water heater (SWH) and solar air heater (SAH). The humidifier unit is based on a cellulose paper as a packing material to increase the mass and heat transfer. A modified design of dehumidifier is used in HDH process to condensate water vapor and improve the performance of the unit. The system is based on the idea of open-water and open -air cycles. The SWH and SAH are integrated with the desalination unit to increase the rate of evaporation. The results showed that, the productivity of the unit strongly depends on the water temperature at humidifier inlet and Ro unit inlet. In addition, the optimal ratio of cold water at dehumidifier inlet to hot water at humidifier inlet (C/H) is obtained. The results show that a maximum productivity of (14.25 L/hr.) is obtained when C/H =2, inlet water mass flow rate to the humidifier (2 kg/min), Using SAH with (5 m/s) humidifier inlet air velocity, and 95 ℃ at humidifier inlet. The productivity obtained from the HDH system while operating full day is 56.6 L/ workday and maximum Ro unit productivity is 55 L/hr. was obtained at 45 ℃ RO unit Feed Water, the productivity obtained from the Ro unit while operating full day is 416 L/ workday was obtained at average 40 ℃ RO unit Feed Water. Hybrid system provides 472 L/day as a Sumption of Condensate water and Ro unit productivity.