Prob 10.3
PROBLEM 10.3
PROBLEM STATEMENT:
A steam power plant operates on the ideal Rankine cycle.
The steam leaves the turbine at a pressure of 0.2 MPa and quality 0.98. The
turbine produces 1500 kW of power.
If the mass flow rate is 1.5 kg/s, find:
(a) The net power output.
(b) The cycle thermal efficiency.
DIAGRAM DEFINING SYSTEM AND PROCESS:
GIVEN:
Steam (H
2
O) operating on an ideal Rankine cycle with superheat
P
4
= 0.2 Mpa = P
1
, x
4
= 0.98
==
&
&
OUT,TURBINE
W1
5
0
0
k
W
,
m
1
.
5
k
g
/
s
FIND:
Net power output
η
&
NET
RANKINE
W
(kW) and cycle thermal efficiency,
ASSUMPTIONS:
1. Both the turbine and the pump are isentropic
2. No kinetic and potential energy effects
3. All processes of the steam are internally reversible
4. No pressure drop in boiler and condenser
5. Incompressible liquid in pump
GOVERNING RELATIONS:
Vapor power systems – Rankine cycle
1.
=−
&&
&
NET
OUT,TURBINE
IN,PUMP
Net power output, W
W
W
2.
η=
&
&
RANKINE
NET
IN
Efficiency,
W
/Q
3.
2
1
P
IN,PUMP
P
W
vdP
(
ICL
)
m
=
∫
&
&
QUANTITATIVE SOLUTION:
The specific enthalpy value at the turbine entrance (h
3
) can be determined from
an energy balance on the turbine:
⇒
=
+
&
&
&
&
OUT,TURBINE
OUT,TURBINE
3
4
3
4
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 Spring '07
 Schmidt
 Energy, Trigraph, AirTrain Newark

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