Page 118 - Handbook of Energy Engineering Calculations

chart, a supplement to the Steam Tables, the following conditions are found
along the vertical isentropic line where s = s = s = 1.6398 Btu/(lb · °F)
1
x
2
(6.8655 kJ/kg · °C):

FIGURE 38 (a) Turbine cream flow diagram. (b) Temperature-

entropy schematic for steam flow.

At the bleed point, where the given extraction pressure, p = 200 lb/in 2
x
(1380 kPa) and the entropy, s , is as mentioned above, the enthalpy, h =
x
x
1284 Btu/lb (2986 kJ/kg) and the temperature, t = 528°F (276°C). At the
x
2
exit, where the given exhaust pressure, p = 110 lb/in (760 kPa) and the
2
entropy, s , is as mentioned above, the enthalpy, h = 1225 Btu/lb (2849
2
2
kJ/kg) and the temperature, t = 400°F (204°C).
2

2. Compute the total available energy to the turbine
Between the throttle and the bleed point the available energy to the turbine,
AE = Q (h − h ), where the full-load rate of steam flow, Q = 80,000 lb/h
l
x
l
1
l
(600 kg/s); other values are as before. Hence, AE = 80,000 × (1362.7 −
1
6
1284) = 6.296 × 10 Btu/h (1845 kJ/s). Between the bleed point and the
exhaust the available energy to the turbine, AE = (Q − Q )(h − h ), where
x
2
1
2
2