An experimental investigation of a

An experimental investigation of a desalination system based on the HDH (humidification and dehumidification)
of air is studied. The experiments were carried out in the premises of an open roof (six
floors) of a Faculty of Engineering, Kafrelsheikh University, Egypt which lies at latitude 31.07
N and
longitude 30.57
E.The evaporator (humidifier) unit is based on a cellulose paper as packing materials
substratum through which water flows, and has a large area of favor evaporation. Cellulose papers with
different wet surface area are used and studied. A modified design of condenser (dehumidifier) is proposed
in HDH process to evaluate the performance of the unit. The condenser unit is a liquidegas heat
exchanger, where water vapor is condensed. The working principle of the set-up is based on the idea of
open-water and closed-air cycles. An evacuated solar water heater is integrated with the desalination
unit. The air is circulated either by natural or forced circulation. The effect of three types of forced
circulating air (up, down and up-down) on the unit performance is considered. Also, the influence of inlet
water temperature and inlet water mass flow rate to the humidifier on the performance HDH unit is
studied. In addition the optimal ratio of cold water at condenser inlet to hot water at evaporator inlet (C/
H) is obtained. The results show that the maximum productivity is obtained when C/H is twice. Also it is
found that forced down air circulation gives higher performance than that obtained for forced up, forced
up-down and natural air circulation. At C/H ¼ 2, inlet water mass flow rate to the humidifier is 4 kg/min
and forced down air circulation the unit productivity is about 23.6 kg/h with water temperature 90
C at
humidifier inlet. Results of the proposed design are compared with that for conventional type and the
comparison shows that the propped design gives a higher performance. Hence, the modified condenser
design increases the condenser effectiveness to be about 0.71 while, for conventional type of 0.49.