Page 121 - A Comprehensive Guide to Solar Energy Systems
P. 121
Chapter 6 • Solar Water Heaters 119
FIGURE 6.7 Schematic of the flat-plate solar collector with PCM [23]. PCM, phase change material.
FIGURE 6.8 Schematic of the solar collector with high porous aluminium foam incorporating with paraffin [25].
Fazilati and Alemrajabi [21] investigated the performance of a solar water heater using
paraffin wax in spherical capsules as the storage medium in the jacketed shell type tank. It
was evaluated that 25% of service time of the SWH system could be prolonged by using PCMs.
A SWH system with a galvanized steel storage tank containing paraffin was investigated
by Al-Hinti et al. [27] (Fig. 6.11). The total volume of the storage tank was at 107.4 l with
paraffin occupying 49.4 l and the water encapsulated making up the remaining volume
(58 l). This water-paraffin PCM storage system reached a temperature of 45°C higher than
the ambient temperature after 24 h of operation.
6.4.2 SWHs With Loop Heat Pipe
A lHP [28–31], as shown in Fig. 6.12, is a two-phase (liquid/vapor) heat transfer device al-
lowing a high thermal flux to be transported over a distance of up to several tens of meters
in a horizontal or vertical position owing to its capillary or gravitational structure. Such
lHP systems consist of an evaporator, condenser, compensation chamber, liquid line, and
vapor line and are particularly suitable for applications linked to SWHs.
