As indicated in Fig. P8.52, a power plant similar to that in Fig. 8.11 operates on a regenerative vapor power cycle with one closed feedwater heater. Steam enters the first turbine stage at state 1 where pressure is 12 MPa and temperature is 560 C. Steam expands to state 2 where pressure is 1 MPa and some of the steam is extracted and diverted to the closed feedwater heater. Condensate exits the feedwater heater at state 7 as saturated liquid at a pressure of 1 MPa, undergoes a throttling process through a trap to a pressure of 6 kPa at state 8, and then enters the condenser. The remaining steam expands through the second turbine stage to a pressure of 6 kPa at state 3 and then enters the condenser. Saturated liquid feedwater exiting the condenser at state 4 at a pressure of 6 kPa enters a pump and exits the pump at a pressure of 12 MPa. The feedwater then flows through the closed feedwater heater, exiting at state 6 with a pressure of 12 MPa. The net power output for the cycle is 330 MW. For isentropic processes in each turbine stage and the pump, determine (a) the cycle thermal efficiency (%). Determine (b) the mass flow rate into the first turbine stage, in kg/s. Determine (c) the rate of entropy production in the closed feedwater heater, in kW/K. Determine (d) the rate of entropy production in the steam trap, in kW/K.

Elements Of Electromagnetics
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As indicated in Fig. P8.52, a power plant similar to that in Fig. 8.11 operates on a regenerative vapor power cycle with one closed feedwater heater. Steam enters the first turbine stage at state 1 where pressure is 12 MPa and temperature is 560 C. Steam expands to state 2 where pressure is 1 MPa and some of the steam is extracted and diverted to the closed feedwater heater. Condensate exits the feedwater heater at state 7 as saturated liquid at a pressure of 1 MPa, undergoes a throttling process through a trap to a pressure of 6 kPa at state 8, and then enters the condenser. The remaining steam expands through the second turbine stage to a pressure of 6 kPa at state 3 and then enters the condenser. Saturated liquid feedwater exiting the condenser at state 4 at a pressure
of 6 kPa enters a pump and exits the pump at a pressure of 12 MPa. The feedwater then flows through the closed feedwater heater, exiting at state 6 with a pressure of 12 MPa. The net power output for the cycle is 330 MW.

For isentropic processes in each turbine stage and the pump, determine (a) the cycle thermal efficiency (%). Determine (b) the mass flow rate into the first turbine stage, in kg/s. Determine (c) the rate of entropy production in the closed feedwater heater, in kW/K. Determine (d) the rate of entropy production in the steam trap, in kW/K. 

a) 43.8%

b) 259.55 kg/s

c) 73.33 kW/K

Need answer to d. 

T
6
5
4
p= 12 MPa
7 p= 1 MPa
8
Steam
generator
p = 6 kPa
3
(v)
www
Closed
feedwater
heater
(1)
S
Condenser
7
IK~
Pump
State p (kPa) T (°C)
1
560
2
3
4
5
6
7
8
12,000
1,000
6
6
12,000
12,000
1,000
6
13³ ↓ (1-9)
Trap 8
(y)
Qout
T
h (kJ/kg) s (kJ/kg-K)
3506.2
6.6840
2823.3
6.6840
2058.2
6.6840 0.7892
151.53
0.5210
0
163.60
0.5210
606.61
1.7808
762.81
2.1387
762.81
2.4968
5
6
7
X
0
0.2530
Fig. 8.11 Regenerative vapor power cycle with one closed feedwater heater.
Fig. P8.52
Transcribed Image Text:T 6 5 4 p= 12 MPa 7 p= 1 MPa 8 Steam generator p = 6 kPa 3 (v) www Closed feedwater heater (1) S Condenser 7 IK~ Pump State p (kPa) T (°C) 1 560 2 3 4 5 6 7 8 12,000 1,000 6 6 12,000 12,000 1,000 6 13³ ↓ (1-9) Trap 8 (y) Qout T h (kJ/kg) s (kJ/kg-K) 3506.2 6.6840 2823.3 6.6840 2058.2 6.6840 0.7892 151.53 0.5210 0 163.60 0.5210 606.61 1.7808 762.81 2.1387 762.81 2.4968 5 6 7 X 0 0.2530 Fig. 8.11 Regenerative vapor power cycle with one closed feedwater heater. Fig. P8.52
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