Calculator inputs
Use enthalpy values from steam tables, property software, or plant test sheets. The page stays single-column, while the form uses 3, 2, and 1 columns across screen sizes.
Example data table
| Item | Example value | Unit |
|---|---|---|
| Inlet pressure | 90 | bar |
| Inlet temperature | 480 | °C |
| Exhaust pressure | 0.12 | bar |
| Inlet enthalpy h₁ | 3375 | kJ/kg |
| Actual outlet enthalpy h₂ | 2440 | kJ/kg |
| Isentropic outlet enthalpy h₂s | 2325 | kJ/kg |
| Mass flow rate | 18 | kg/s |
| Mechanical efficiency | 98 | % |
| Generator efficiency | 97 | % |
| Boiler heat input | 21000 | kW thermal |
| Auxiliary load | 250 | kW |
| Sample turbine isentropic efficiency | 89.05 | % |
| Sample net electrical power | 15748.60 | kW |
| Sample overall efficiency | 74.99 | % |
Formula used
1) Actual specific turbine work
wactual = h₁ − h₂
2) Isentropic specific turbine work
wisentropic = h₁ − h₂s
3) Turbine isentropic efficiency
ηt = (wactual / wisentropic) × 100
4) Shaft power
Pshaft = ṁ × wactual
5) Gross electrical power
Pgross = Pshaft × ηmech × ηgen
6) Net electrical power
Pnet = Pgross − Paux
7) Overall efficiency
ηoverall = (Pnet / Qin) × 100
8) Specific steam consumption
SSC = (ṁ × 3600) / Pnet
Enthalpy terms normally come from steam tables or property software. Pressure and temperature help define the operating point, but this calculator uses enthalpy values directly for the thermodynamic efficiency calculation.
How to use this calculator
- Enter the turbine inlet pressure, inlet temperature, and exhaust pressure.
- Find h₁, h₂, and h₂s from steam tables, Mollier charts, or property software.
- Enter mass flow rate, mechanical efficiency, and generator efficiency.
- Add boiler heat input and auxiliary load to estimate net plant performance.
- Enter annual operating hours, fuel cost, and electricity price for yearly economics.
- Click Calculate Efficiency to show results above the form.
- Review the Plotly chart to compare actual and isentropic expansion paths.
- Use the CSV and PDF buttons to export the result summary.
Frequently asked questions
1) What efficiency does this calculator show?
It reports turbine isentropic efficiency and overall plant efficiency. The first compares actual and ideal enthalpy drop. The second compares net electrical output with boiler heat input.
2) Where do the enthalpy values come from?
Use steam tables, Mollier charts, plant historian values, or thermodynamic software. The calculator assumes those properties are already known for inlet, actual outlet, and isentropic outlet states.
3) Can I calculate efficiency using pressure and temperature only?
Not directly in this version. Pressure and temperature help identify the state point, but you still need enthalpy values from steam-property references to complete the efficiency calculation accurately.
4) Why is overall efficiency lower than turbine efficiency?
Overall efficiency includes more losses. Mechanical losses, generator losses, auxiliary consumption, and boiler heat input all reduce the plant-level figure compared with the turbine-only isentropic efficiency.
5) What does it mean if efficiency is above 100%?
That usually means an input problem. Recheck h₂, h₂s, boiler heat input, and auxiliary load. Real steam turbines do not achieve more than 100% isentropic or overall efficiency.
6) Can I use this for condensing and back-pressure turbines?
Yes. The same enthalpy-based method works for both. Just make sure the outlet pressure and outlet enthalpy values match the actual turbine configuration and operating condition.
7) Why is steam rate useful?
Steam rate shows how many kilograms of steam are needed per kilowatt-hour. Lower values usually indicate better performance and help compare units, upgrades, and test runs.
8) Are annual hours and energy price required?
They are only needed for yearly energy and margin estimates. The thermodynamic core results still depend mainly on enthalpy values, steam flow, efficiency factors, and auxiliary load.