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

the amount of condensation in the working fluid depends principally on the
thermophysical properties of the solid phase (or PCM), namely, the thermal
capacitance of the packed bed. The larger the thermal capacitance, the larger the
amount of condensation in working fluid is.
Weislogel and Chung [127] reported that, a PCM packed bed with condensing
working fluid passing through has many potential benefits. It will further enhance the
condensation rate by using encapsulated PCM packing with large heat capacity and
melting temperature close to the lower limit of the operation temperature range of the
condenser. Thomas et al [57] indicated that the volumetric heat transfer coefficient
for direct contact condensation of immiscible fluid in a packed bed is inversely
proportional to the difference between the saturation temperature and the average
bed temperature.
Figure 2.18: Schematics of the radiative cooled solar still [140]
2.8.6 Solar collectors
Bourouni et al., [129] stated that coupling HDH units with thermal solar collectors
presents a very interesting solution; however, the water cost is relatively high. They
attributed the higher production cost of HDH systems to two different reasons. One
reason for this is that solar heating necessitates significant investment in solar
collectors and land. Another is that very large amounts of air need to be recirculated
because the quantity of water normally contained in saturated air is minimal. Thus,
air pumping alone may represent a prohibitive energy cost.
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