Details

The inlet temperature to the turbine, (°C) is set; you can vary the inlet and outlet pressures (MPa). From these conditions the enthalpy (kJ/kg) and entropy (kJ/[kg K]) are obtained from the superheated steam tables.

The superscript denotes reversibility. A reversible steam turbine is isentropic, so , where is the entropy of the steam exiting a reversible turbine.

If at , then the reversible outlet state is superheated.

If at , then the outlet steam is at saturation temperature and consists of liquid and vapor. The quality of the steam is:

,

where is the fraction of vapor (quality), and the superscripts and refer to saturated liquid and saturated vapor.

Depending on the quality of the exiting steam, is obtained from either the saturated steam tables or the superheated steam tables.

If , and is found in the superheated steam tables at and .

If , and .

The change in enthalpy for the reversible turbine is the work for the reversible process.

The turbine efficiency indicates the turbine irreversibility and is the ratio of irreversible work to reversible work. For the irreversible turbine:
.

The cycle efficiency is:

,

where is the net work (kJ/kg), and is heat added (kJ/kg).

The screencast video at [1] shows how to use this Demonstration, and the video at [2] explains the cycle.

References

[1] Rankine Cycle. www.colorado.edu/learncheme/thermodynamics/RankineCycle.html.

[2] Power Cycle Introduction [Video]. (Mar 15, 2012) www.youtube.com/watch?v=BA77fu3zAbs.