In back pressure turbines, steam just inters through HP valves & exists through exhaust, no any bleed or condensation is done.

The efficiency of the back pressure turbines is more as compared to condensate & condensate cum extraction steam turbines. However specific steam consumption of back pressure turbines is very less as compared to above both type of Turbines

**How do you 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 64 kg/cm2 and 490 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 64 kg/cm2 and 490 deg C = 809 kcal/kg

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

Work done = (809-660) = 149 kcal/sec

Or 4.18 X 149 = 622.82 kJ/kg or 622.82 KW

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

**SSC = 860 / 149 = 5.78 kg/kw or MT/MW**

A back pressure turbine having inlet steam enthalpy and exhaust enthalpy 780 kcal/kg & 580 kcal/kg, then calculate the specific steam consumption of that Turbine?

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

SSC = 860 / (780-580)

SSC =4.3 MT/MW

Read ** Powerplant and calculations** for such more articles

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