Page 336 - Steam Turbines Design, Applications, and Rerating

310 Chapter Fifteen

Figure 15.1 Determination of approximate efficiency for mul-
tivalve, multistage turbines, English units. (Elliott Company,
Jeannette, Pa.)

As can be seen in the example, a 25,000 hp, 5000 r/min turbine using
steam at 600 psig/750°F/4 in Hga has an approximate efficiency of 77
percent.
Applying this approximate efficiency to the theoretical steam rate
(TSR), Table 14.3, results in a steam rate and steam flow as follows:
TSR 600 psig/750°F/4 in Hga = 7.65 lb/kWh

Approximate efficiency =η a = 77%

Approximate steam rate (ASR) = TSR/η a
= (7.65 lb/kWh) (.746 kW/hp)/0.77 = 7.40 lb/hph