Microsoft Word - Cengel and Boles TOC _2-03-05_.doc

Chapter 10 | 567

Pump

3

6

Boiler

Condenser

2 s

T, °C

4

1

5

Reheater

Reheating

P 4 = P 5 = Preheat

15 MPa

10 kPa

10 kPa

15 MPa

15 MPa 600

4

5

1 6

3

2

10 kPa

Low-P 15 MPa

turbine

High-P

turbine

FIGURE 10–13

Schematic and T-sdiagram for Example 10–4.

(b) To determine the thermal efficiency, we need to know the enthalpies at

all other states:

State 1:

State 2:

State 3:

State 4:

Thus

2143.3 kJ>kg

qout
h 6 h 1 
 1 2335.1191.81 2 kJ>kg

3896.1 kJ>kg

 1 3583.1206.95 2 kJ>kg 1 3674.93155.0 2 kJ>kg

qin
 1 h 3 h 22  1 h 5 h 42

P 4 
4 MPa

s 4 
s 3

f¬

h 4 
3155.0 kJ>kg

1 T 4 
375.5°C 2

P 3 
15 MPa

T 3 
600°C

f¬

h 3 
3583.1 kJ>kg

s 3 
6.6796 kJ>kg#K

h 2 
h 1 wpump,in
 1 191.8115.14 2 kJ>kg
206.95 kJ>kg

15.14 kJ>kg

 31 15,000 102 kPa4a

1 kJ

1 kPa#m^3

b

wpump,in
v 11 P 2 P 12 
 1 0.00101 m^3 >kg 2

s 2 
s 1

P 2 
15 MPa

P 1 
10 kPa

Sat. liquid

f¬

h 1 
hf @ 10 kPa
191.81 kJ>kg

v 1 
vf @ 10 kPa
0.00101 m^3 >kg