Page 289 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Be st Practice 5 .1 Steam Turbine Best Practices

Uses:
Determine the amount of steam required per hour
Determine the amount of potential kW (horsepower)
Required:
Steam conditions
Theoretical steam rate table or Mollier diagram
Thermal efficiency of turbine
Formula:
Metric Units U.S. Units
Theoretical steam rate
3600 kJ/kW-hr 2545 BTU′S/HP-hr
TSR (kg/kWhr) = TSR (lb/HP-hr) =
ΔH ISENTROPIC ΔH ISENTROPIC
Actual steam rate
T.S.R. 3600 kJ/kW-hr T.S.R 2545 BTU/HP-hr
A.S.R. (kg/kWhr) = = A.S.R. (lb/HP-hr) = =
Efficiency ΔH ACTUAL Efficiency ΔH ACTUAL HP/hr
Turbine efficiency
T.S.R. ΔH ACTUAL
Efficiency = =
A.S.R ΔH ISENTROPIC
Fig 5.1.5 Determining steam rate

Quoted turbine efficiencies are external efficiencies; they
include mechanical (bearing, etc.) and leakage losses
Turbine efficiency at off load conditions will usually be lower
than rated efficiency
Typical efficiencies are presented for impulse turbine:
Condensing multi-stage
Non-condensing multi-stage
Non-condensing single state

Fig 5.1.6 Typical steam turbine efficiencies

Fig 5.1.7 Efficiency of multistage turbines (Courtesy of IMO Industries)

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