To calculate the work done per kg of steam

 Let us assume 1 kg/sec of steam is entering into Turbine whose enthalpy is H1 kcal/kg & existing from turbine at enthalpy H2 kcal/kg

Then, work done per kg of steam is given as =(H1-H2) kcal/s

Or 4.18 X (H1-H2) KW, since 1 KJ/sec = 1 KW

 How do you calculate specific steam consumption of a back pressure Turbine?

 Specific steam consumption is defined as the amount of steam consumed to generate 1 KW of power

 SSC = 860 / (Difference in inlet & exhaust enthalpy)

 i.e 860 / (H1-H2)

 A back pressure turbine is operating at pressure & temperature 104 kg/cm2 and 545 deg C respectively, the exhaust steam at pressure 2 kg/cm2& temperature 140 deg C is being used for process.Calculate the work done and specific steam consumption?

 Enthalpy of inlet steam at pressure & temperature 105 kg/cm2 and 545 deg C  = 825 kcal/kg

 Enthalpy of inlet steam at pressure & temperature 2 kg/cm2 and 140 deg C  = 660 kcal/kg

 Work done = (825-660) = 165 kcal/kg

Or 4.18 X 165 = 689.7 kJ/kg or 689.7 KW

Specific steam consumption SSC = 860 / (Difference in inlet & exhaust enthalpy)

SSC = 860 / 165 = 5.21 kg/kw or MT/MW

Note: In this calculation, Turbine efficiency, Gear box efficiency and Alternator efficiencies are not being considered, so SSC may show on lower side.