Experimental and Numerical Analysis of a PCM-Supported ...

On the other hand, the efficiency of the collector, humidifier and condenser increase
at higher feed flow rate. In the humidifier, higher water flow rate will improve both the
mass transfer coefficient and the degree of wetting of the packing. Al-Hallaj and
Selman [2] developed an analytical semi-empirical simulation model for the HDH
system without thermal storage, and predicted its output in terms of the distillate
rate. The simulation results have shown a maximum production rate at 0.013 kg/s of
water flow rate, as shown in figure (2.9), due to combined effects of feed flow rate.
Figure 2.9: Effect of the feed water flow-rate on the daily production
of the HDH desalination unit [132]
Al-Enezi et al [142] studied experimentally on a global level the characteristics of
HDH process a as a function of operating conditions. A small capacity experimental
system composed of a packed bed humidifier, a double pipe glass condenser, a
constant temperature water circulation tank and a chiller for cooling water was used
for the study. As shown in figure (2.7), the water production was found to depend
strongly on the hot water temperature. Also the water production was found to
increase with the increase of air flow rate and the decrease of cooling water
temperature. They emphasized that the distillate rate decreases with the increase in
the feed seawater flow rate.
Al-Enezi et al [142] clarified that increasing the hot water flow rate has two opposite
effects on the system performance. The first is the decrease in the system operating
temperature due to the increase in water flow rate at constant input energy through
the heat supply. This effect reduces the driving force for evaporation and, in return,
the amount of product water. On the other hand, increasing the feed water flow rate
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