Environmental Engineering Reference
In-Depth Information
where
I
N
is direct normal radiation at the ground level and
I
oN
is the corresponding value at
the edge of the atmosphere. Since the hourly global radiation is measured at a tilted surface
having the same tilt angle as the collector absorber plates,
I
t
, it is possible to solve the
following equation for the hourly values of
P
:
1
1
sin(
h
)
1
1
−
P
1
+
cos(
α
)
sin(
h
)
I
=
I
×
P
×
cos(
θ
)
+
×
I
×
sin(
h
)
×
×
(5)
t
o
o
2
1
−
1
4
ln(
P
)
2
Figure 11. Solar angles.
With the hourly values of
P
estimated, it is possible to calculate the direct and diffuse
components from Eqs. 2 and 3.
5.2. Calculating the Amount of Heat Collected and Collector Outlet Water
Temperature
The heat collection amount,
Q
c
, was calculated from the measured collector inlet and
outlet water temperatures and the water flow rate
Q
=
m
C
(
T
−
T
)
(6)
c
c
p
c
2
c
1
where
m
c
is the water flow rate through the collector bank (or block) and
T
c1
and
T
c2
are the
inlet and outlet water temperatures, respectively.
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