Formula & Engineering Notes
Ideal (isentropic) expansion to P2:
The inlet entropy is fixed from (P1, T1); the outlet state is read at P2 at that same entropy. Δh is the maximum (reversible) energy release; a real expansion makes entropy and releases less.
All steam properties are interpolated from the shared IAPWS-IF97 steam-table datasets — see the full steam tables and the Steam Property Calculator.
This is the turbine calculation stripped to its physics, with no efficiency or flow — just "if I drop this steam from here to there ideally, what happens and how much energy is on the table?" Constant entropy is the assumption: it's the best case, the yardstick everything real gets measured against.
Notice the steam usually gets wetter as it expands — that's the saturation dome doing its thing. If you need the actual, irreversible result (warmer, higher entropy, less work), apply an efficiency, which is exactly what the turbine-power tool does.