TITLE.PM5

VAPOUR POWER CYCLES 549

dharm

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1

Boiler Turbine

0.1 bar, 0.9 dry

0.09 bar

2

Saturated liquid 3

Wp

4

70 bar

Q 1 WT

60 bar, 380 Cº

65 bar

400 Cº

Q 2

Fig. 12.6
At 0.1 bar :
hf 2 = 191.8 kJ/kg, hfg 2 = 2392.8 kJ/kg (from steam tables)
and x 2 = 0.9 (given)
∴ h 2 = hf 2 + x 2 hfg 2 = 191.8 + 0.9 × 2392.8 = 2345.3 kJ/kg
Power output of the turbine = ms (h 1 – h 2 ) kW,
[where ms = Rate of steam flow in kg/s and h 1 , h 2 = Enthalpy of steam in kJ/kg]

=

10000

3600 (3123.5 – 2345.3) = 2162 kW

Hence power output of the turbine = 2162 kW. (Ans.)

(ii) Heat transfer per hour in the boiler and condenser :

At 70 bar : hf 4 = 1267.4 kJ/kg

At 65 bar, 400°C :ha =

3177.2 60 3158.1 70

2

bgbgbar+ bar

= 3167.6 kJ/kg

......(By interpolation)

∴ Heat transfer per hour in the boiler,

Q 1 = 10000 (ha – hf 4 ) kJ/h

= 10000 (3167.6 – 1267.4) = 1.9 × 107 kJ/h. (Ans.)

At 0.09 bar : hf 3 = 183.3 kJ/kg

Heat transfer per hour in the condenser,

Q 1 = 10000 (hh 2 − f 3 )

= 10000 (2345.3 – 183.3) = 2.16 × 10^7 kJ/h. (Ans.)

(iii) Mass of cooling water circulated per hour in the condenser, mw :

Heat lost by steam = Heat gained by the cooling water

Q 2 = mw × cpw (t 2 – t 1 )

2.16 × 10^7 = mw × 4.18 (30 – 20)

∴ mw = 2.16 10

4.18 30 20

×^7

bg−

= 1.116 × 107 kg/h. (Ans.)