Environmental Engineering Reference
In-Depth Information
The rate of heat rejected by the condenser is defined as
Q
con
=˙
m
6
(
h
6
−
h
3
)
(3.3.8)
Q
con
represents heat transfer rate rejected by the condenser,
where
m
6
represents mass
flow rate at state 6,
h
6
represents specific enthalpy at state 6, and
h
3
represents specific
enthalpy at state 3.
The exergy destruction rate in the condenser is calculated as
˙
Ex
6
=
Ex
3
+
Ex
con
+
Ex
de,con
(3.3.9)
where
m
6
(
h
6
−
s
0
)
Ex
6
=˙
h
0
)
−
T
0
(
s
6
−
1
T
0
T
con
Ex
con
=
Q
con
−
T
6
+
T
3
T
con
=
2
m
3
h
3
h
0
−
s
0
)
Ex
3
=˙
−
T
0
(s
3
−
Ex
6
represents exergy rate at stat 6,
Ex
con
represents exergy rate carried by heat
where
Ex
3
represents exergy rate at state 3, and
Ex
de,con
represents
exiting the condenser,
exergy destruction rate in the condenser.
The energy and exergy efficiencies are calculated as
W
t
−
W
p
I
×
A
=
1000
η
en
(3.3.10)
W
t
−
W
p
Ex
so
η
ex
=
(3.3.11)
where
η
en
represents energy efficiency of the system and
η
ex
represents exergy efficiency
of the system.
3.3.1.3 Results and discussion
Effects of variation in parameters such as ambient temperature, solar thermal area,
and pressure at state 4 on energy and exergy efficiencies are studied in this section.
It is observed that rise in ambient temperature doesn't affect the energy efficiency
but does result in a slight increase in exergy efficiency as seen in Figure 3.3.2. The
energy efficiency is found to be constant at 16.37% while exergy efficiency increases
from 17.19% to 17.3% with a rise in ambient temperature from 275 K to 310 K. This
result is important as it shows that from the energy perspective changes in ambient
temperature have no effect on the performance of the system, but we know that in real
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