TITLE.PM5

VAPOUR POWER CYCLES 571

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\M-therm\Th15-2.pm5

(iii)Thermal efficiency of the Rankine cycle
(iv)Theoretical gain due to regenerative feed heating,
(v)Steam consumption in kg/kWh with or without regenerative feed heating, and
(vi)Quantity of steam passing through the last stage nozzle of a 50000 kW turbine with and
without regenerative feed heating.
Solution. Refer Fig. 12.20 (a), (b).

1 2 3

T u r b i n e

0

1 kg

Drain cooler

Condenser

(^12)
(^34)
m, h 11 m, h 22 m, h 33
1 – m (^1) 1 – m – m
(^12) 1 – m – m – m
123
m + m + m 123
hf 4 1 kg, hf 4
hf 2 hf 3 hf 5
1 kg
m, h1f 1 (m + m ), h12f 2 (m + m + m ), h123f 3
(a)
h
s
(b)
20 bar, 250 C
º
(^0) 1kg
(1 – m )^1
5.0 bar
1.5 bar
0.3 bar
0.05 bar
1
2
3
4
(1– m – m )
12
(1– m – m – m )
12 3
Fig. 12.20
From Mallier Chart : h 0 = 2905 kJ/kg, h 1 = 2600 kJ/kg, h 2 = 2430 kJ/kg
h 3 = 2210 kJ/kg, h 4 = 2000 kJ/kg
From steam tables :
At 5 bar : hf 1 = 640.1 kJ/kg
At 1.5 bar : hf 2 = 467.1 kJ/kg