TITLE.PM5

594 ENGINEERING THERMODYNAMICS

dharm

\M-therm\Th12-4.pm5

1

2

Boiler

H.P.

0.4 bar

4

Condenser

3

Superheater

1kg

80 bar

80 bar

Reheater

L.P.

mkg

7 bar

(1–m) kg

7 bar

(^2) 7 bar (1–m) kg
Feed heater
7 bar
( ) Schematic arrangement of the planta
s (kJ/kg K)
h (kJ/kg)
( )bh-sdiagram
3170
2985
2555
2520
(^13)
2
80 bar 7 bar
350°C350°C
1kg
(1–m)(1–m) kgkg
0.4 bar
Fig. 12.39
(i) The ratio of steam bled to steam generated :
Consider energy/heat balance of feed heater :
Heat lost by m kg of steam = Heat gained by (1 – m) kg of condensed steam
m(h 2 – hf 2 ) = (1 – m) (hf 2 – hf 4 )
m(2520 – 697.1) = (1 – m) (697.1 – 317.7)
1822.9 m = (1 – m) × 379.4
∴ m = 0.172 kg
i.e. Amount of steam bled per kg of steam supplied to the turbine = 0.172 kg
∴ Steam generated
Steam bled
=^1
0 172.
= 5.814. (Ans.)