only on a limited scale.
Several Researchers investigated the heat transfer characteristics
of PCMs in an LHS during melting and solidification [28–33].
Sari and Kaygusuz [34] studied the phase transition time, the phase
change temperature and the propagation of the solid–liquid
interface in both radial and axial directions as well as the effect of
the heat flow rate on the phase change stability of steric acid,
which was used as the phase change energy storage material. They
found that melting and solidification occurred from an upper and
lower point in the axial direction, respectively. In the radial
direction melting came about from a point closer to the HTF to a
point far away from it, while solidification was observed to be in
the opposite direction. On the contrary, Sukhatme [35] and
Ettouney et al. [23] reported that during the discharge period PCM
first solidified at the heat transfer surface. Furthermore, it was
indicated that the temperature of HTF affected the charge and
discharge times while the effect of the flow rate of HTF in the