For each individ ual co mponent, the first an d second
laws of thermo dynami c are applied to find the work out put, the he at added or rejec ted, and the syst em irre versibility. The energy balance eq uation can be express ed a s
Xi
Ei þ Q_ ¼ X
0
E0 þ W_ ð1 Þ
The irreversibility rate for uniform flow conditions can be
expressed as
_I ¼ T
o
dS
dt ¼ Tom_ X sexit X sinlet þ dssystemdt þ X
j
qj
T
" #jð2
Þ
where the subscript ‘‘ j’’ stands for the heat transfer for different reservoirs and the term (dssystem/dt) = 0 for steady
state conditions.
2.1. Basic ORC – Fig. 2(a)
2.1.1. Process 1–2 (pump)
Using Eq. (1) the pump power can be expressed as
W_
p ¼
W_
p ;ideal
gp
¼
m_ ðh1 h2s Þ
gp
ð3 Þ
where W_
p ;ideal is the ideal power of the pump, m_ is the working fluid mass flow rate, gp is the isentropic efficiency of
the pump, and h1 and h2s are the enthalpies of the working fluid at the inlet and outlet of the pump for the ideal
case.
Using Eq. (2), the pump irreversibility rate can be determined
For each individ ual co mponent, the first an d second
laws of thermo dynami c are applied to find the work out put, the he at added or rejec ted, and the syst em irre versibility. The energy balance eq uation can be express ed a s
Xi
Ei þ Q_ ¼ X
0
E0 þ W_ ð1 Þ
The irreversibility rate for uniform flow conditions can be
expressed as
_I ¼ T
o
dS
dt ¼ Tom_ X sexit X sinlet þ dssystemdt þ X
j
qj
T
" #jð2
Þ
where the subscript ‘‘ j’’ stands for the heat transfer for different reservoirs and the term (dssystem/dt) = 0 for steady
state conditions.
2.1. Basic ORC – Fig. 2(a)
2.1.1. Process 1–2 (pump)
Using Eq. (1) the pump power can be expressed as
W_
p ¼
W_
p ;ideal
gp
¼
m_ ðh1 h2s Þ
gp
ð3 Þ
where W_
p ;ideal is the ideal power of the pump, m_ is the working fluid mass flow rate, gp is the isentropic efficiency of
the pump, and h1 and h2s are the enthalpies of the working fluid at the inlet and outlet of the pump for the ideal
case.
Using Eq. (2), the pump irreversibility rate can be determined
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