Q .
Z2
1;w
dQ (3c)
Q . Qt Q (3d)
All real thermodynamic systems, such as power plants, are
irreversible systems which generate entropy. The entropy generation
rate over the closed system may be written as follows [17]:
S2 S1
Z2
1;w
dQ
T
. d; (4)
where S1 is the entropy at the initial state and S2 at the final state
after some transformation process w. The temperature T in integral
means the temperature at that point of the boundary of the system
over which the heat dQ is flowing [17]. Symbol d represents the
entropy generation term due to the irreversibilities of the transformation
process and its value is always positive. The net heat in
Equation (4) can be divided into heat absorbing and emitting parts
[17]:
Z2
1;w
dQ
T
.
Z2
1;w
dQt
T
Z2
1;w
dQ
T ; (5)
If the temperature T in heat integrals is constant, the integrals
can be written as follows:
Z2
1;w
dQt
T
. Qt
Tt;constant
(6a)
Z2
1;w
dQ
T
. Q
T;constant
; (6b)
In real thermodynamic systems, heat dQt and dQ- usually flow
in and out of the system at several different temperature levels. This
means that the temperature cannot be taken outside the heat integral.
To be able to express heat integrals in the similar way as in
Equations (6a) and (6b), Lampinen and Wiksten have proposed the
use of the so called effective heat-absorbing and eemitting temperatures
which are defined as follows [17]:
Qt
Tt
ß
Z2
1;w
dQt
T
(7a)
Q
T
ß
Z2
1;w
dQ
T ; (7b)
where temperatures Tt and T represent the effective heatabsorbing
and -emitting temperatures, respectively. Formally,
Equations (7a) and (7b) are identical with Equations (6a) and (6b).
However, the heat dQt and dQ does not have to flow in and out of
the system at the constant temperature. The effective heatabsorbing
and -emitting temperatures are defined case dependently
for various thermodynamic processes where heat dQt and
dQ- may flow in and out of the system at several different temperature
levels. For example, this paper defines the effective temperatures
for a power plant undergoing ClausiuseRankine cycle.
Q .
Z2
1;w
dQ (3c)
Q . Qt Q (3d)
All real thermodynamic systems, such as power plants, are
irreversible systems which generate entropy. The entropy generation
rate over the closed system may be written as follows [17]:
S2 S1
Z2
1;w
dQ
T
. d; (4)
where S1 is the entropy at the initial state and S2 at the final state
after some transformation process w. The temperature T in integral
means the temperature at that point of the boundary of the system
over which the heat dQ is flowing [17]. Symbol d represents the
entropy generation term due to the irreversibilities of the transformation
process and its value is always positive. The net heat in
Equation (4) can be divided into heat absorbing and emitting parts
[17]:
Z2
1;w
dQ
T
.
Z2
1;w
dQt
T
Z2
1;w
dQ
T ; (5)
If the temperature T in heat integrals is constant, the integrals
can be written as follows:
Z2
1;w
dQt
T
. Qt
Tt;constant
(6a)
Z2
1;w
dQ
T
. Q
T;constant
; (6b)
In real thermodynamic systems, heat dQt and dQ- usually flow
in and out of the system at several different temperature levels. This
means that the temperature cannot be taken outside the heat integral.
To be able to express heat integrals in the similar way as in
Equations (6a) and (6b), Lampinen and Wiksten have proposed the
use of the so called effective heat-absorbing and eemitting temperatures
which are defined as follows [17]:
Qt
Tt
ß
Z2
1;w
dQt
T
(7a)
Q
T
ß
Z2
1;w
dQ
T ; (7b)
where temperatures Tt and T represent the effective heatabsorbing
and -emitting temperatures, respectively. Formally,
Equations (7a) and (7b) are identical with Equations (6a) and (6b).
However, the heat dQt and dQ does not have to flow in and out of
the system at the constant temperature. The effective heatabsorbing
and -emitting temperatures are defined case dependently
for various thermodynamic processes where heat dQt and
dQ- may flow in and out of the system at several different temperature
levels. For example, this paper defines the effective temperatures
for a power plant undergoing ClausiuseRankine cycle.
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