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

Chapter 10 | 575

Boiler

Condenser

s

T

5

9

1

2

Pump II

1

11

2

13

Closed

FWH

9

3

7

12

3

8

7

6

Low-P

turbine

High-P

turbine

Open

FWH

Pump III Pump I

4 MPa

8

4

6

0.5 MPa

Reheater

1 kg

Mixing

chamber

10 kPa

15 MPa

600 °C

1 – y – z

10

y P 10 = P 11 = 4 MPa

600 °C z

11

10

12

13

5

4

15 MPa

4 MPa

0.5 MPa z

10 kPa

1 – y

1 –

y

1 kg

y

1 – y – z

1 – y

FIGURE 10–19

Schematic and T-sdiagram for Example 10–6.

The fractions of steam extracted are determined from the mass and energy

balances of the feedwater heaters:

Closed feedwater heater:

Open feedwater heater:

The enthalpy at state 8 is determined by applying the mass and energy

equations to the mixing chamber, which is assumed to be insulated:

1089.8 kJ>kg

h 8 
 11 0.1766 21 1087.4 2 kJ>kg0.1766 1 1101.2 2 kJ>kg

112 h 8 
 11 y 2 h 5 yh 7

E

#

in
E

#

out

z

11 y 21 h 3 h 22

h 12 h 2

11 0.1766 21 640.09192.30 2

3014.8192.30

0.1306

zh 12  11 yz 2 h 2 
 11 y 2 h 3

E

#

in
E

#

out

y

h 5 h 4

1 h 10 h 62  1 h 5 h 42

1087.4643.92

1 3155.01087.4 2  1 1087.4643.92 2

0.1766

yh 10  11 y 2 h 4 
 11 y 2 h 5 yh 6

E

#

in
E

#

out