Formula & Engineering Notes
Turbine work (isentropic basis):
The inlet enthalpy and entropy come from (P1, T1). The ideal outlet h2s is found at the outlet pressure at the same entropy — in the wet region from quality, in the superheated region by inverting the table. Actual drop = ηs × ideal drop.
All steam properties are interpolated from the shared IAPWS-IF97 steam-table datasets — see the full steam tables and the Steam Property Calculator.
The whole game of a turbine is converting enthalpy into shaft work, and entropy is the referee. A perfect machine would expand at constant entropy — that vertical line on a Mollier chart sets the absolute most work you could ever get. Find that ideal end point, take the enthalpy drop, and multiply by the isentropic efficiency for what a real machine delivers.
Watch the exit quality. As steam expands it gets wetter, and below roughly 0.88 those droplets start sandblasting the last-stage blades. If this tool flags a wet exit, you either superheat more at inlet or accept a higher back-pressure.