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

m
d m
a w 2
w 1
(4.83)
where w 2 and w 1 are the moisture contents of the air entering and leaving the
condenser respectively (kg w /kg air ).
As mentioned earlier, the usable output heat during day time is broken down into
input heat which is supplied to the HDH system and stored heat for night time
operation or during cloudy hours. The quantity and quality of energy input to the
HDH cycle is directly related to the storage and collector characteristics. Due to
mainly transient conditions in solar operated facilities and integration of the thermal
buffer in the solar system, the input energy to the HDH cycle cannot be based on a
short time such as hourly or daily calculations. Thus it is possible to express the GOR
as an integrated value over a fairly long time period or one year by the ratio between
total fresh water production and total energy input. As radiation data is only available
on hourly basis for one year (8760 hr/year), thus t = 0 to 8760 is taken into the
integral. The cumulated yearly GOR can then be written as:
t
8760
t 0
t
md
hfg
dt
0
GOR
8760
(4.84)
Q dt
in
t
Energy recovery is achieved in two different ways, brine recirculation and recovery of
latent heat of condensation:
Q
rec
r
w
T
T
M c T
T
M c
(4.85)
w5 amb hw w w7
w6
Where M hw is the hot seawater water load required for the evaporator and M r is the
recirculated brine.
4.5.8 Salt and mass flow balances
Assuming that the distillate water is free of salt, the overall mass and salt balances
can be applied on the HDH system. As a starting point, the mass of the brine blow
down M b can be related to the feed seawater make-up M f through a salt balance on
the evaporator:
98