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

for latent heat storage would be obtained when the melting point or range of a PCM
lies outside the operation range. Figure (8.11) shows a histogram of the hourly
variation of outlet hot water temperature from the solar collector, which represents
the inlet temperature to the PCM storage tank.
Figure 8.11: Histogram of hourly variation of inlet water temperature to the
PCM-storage over one year for Al-Arish city with 3m 3 thermal storage
It is clear from the figure how wide the fluctuation margin in the collector outlet water
temperature. The useful heat output from the collector under the local influencing
meteorological quantities and the specified load structure is indeed not favourable of
a latent heat store. The Stefan number (Ste) materializes these facts; it is the ratio of
the PCM sensible heat to latent heat per unit mass:
c
Ste
pcm( Ti
h
Ti
, c
,
)
(8.1)
Hm
Where T i,h , and T i,c represent the inlet fluid temperature during the heating (energy
storing) period, and the inlet fluid temperature during the cooling (energy releasing)
period respectively. The symbols c pcm is the heat capacity of the PCM, and Hm
is
the latent heat of phase change.
As Stefan number tends to infinity (Ste→∞), sensible heat storage dominates, while
when the Stefan number approaches zero (Ste→ 0), latent heat storage dominates.
For optimal PCR operation, the latter limiting case is preferred. These effects are
clearly observed and elaborately discussed by both Erk and Dudukovic [83] and
Modarresi and Sadrameli [84]. The physical properties of useful phase change
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