Page 69 - Handbook of Energy Engineering Calculations

MOISTURE CONTENT AND STEAM ENTHALPY OF STEAM
TURBINE EXHAUST

What is the enthalpy and percent moisture of the steam entering a surface
condenser from the steam turbine whose Mollier chart is shown in Fig. 9?
2
The turbine is delivering 20,000 kW and is supplied steam at 850 Ib/in (abs)
(5856.5 kPa) and 900°F (482.2°C); the exhaust pressure is 1.5 in (3.81 cm)
Hg absolute. The steam rate, when operating straight condensing, is 7.70
lb/delivered kWh (3.495 kg/kWh) and the generator efficiency is 98 percent.

FIGURE 9 Mollier chart for turbine exhaust conditions.

Calculation Procedure:

1. Compute the engine efficiency of the turbine
Use the relation E = 3413/(w )(H − H ), where E = engine efficiency; w =
1
s
c
s
e
e
steam rate of the turbine when operating straight condensing in the units
given above; enthalpies H and H are as shown in the Mollier chart.
1
c
Substituting, E = 3413/(7.7)(1453 − 898) = 0.7986 for ideal conditions.
e