- W_actual (kW) = ṁ · (h₁ − h₂,actual)
- W_ideal (kW) = ṁ · (h₁ − h₂,s)
- η_isentropic = W_actual / W_ideal
- P_shaft = W_actual · η_mech
- P_elec = P_shaft · η_gen
- η_overall = P_measured / W_ideal (optional)
- Collect inlet and outlet states from test logs.
- Determine h₁ and h₂,actual from property data.
- Compute h₂,s for isentropic expansion.
- Enter mass flow and efficiencies, then calculate.
- Export CSV or PDF for reporting and QA checks.
| Turbine | ṁ (kg/s) | h₁ (kJ/kg) | h₂,actual (kJ/kg) | h₂,s (kJ/kg) | η_mech (%) | η_gen (%) | Measured P (kW) |
|---|---|---|---|---|---|---|---|
| Steam | 12.50 | 3,275 | 2,450 | 2,360 | 98 | 97 | 9,800 |
| Gas | 7.20 | 980 | 760 | 720 | 99 | 98 | 1,550 |
| Hydro | 55.00 | 160 | 120 | 110 | 99 | 98 | 2,050 |
| Time | Type | η_is (%) | W_actual (kW) | P_elec (kW) | η_overall (%) | ṁ (kg/s) | h₁ | h₂,a | h₂,s | Notes |
|---|---|---|---|---|---|---|---|---|---|---|
| No history yet. Run a calculation to populate this table. | ||||||||||
Commissioning targets and acceptance checks
Field acceptance often compares calculated isentropic efficiency against the guaranteed curve at the tested load. Record inlet and outlet pressures, temperatures, and flow, then derive consistent enthalpies for each operating point. A small sensor drift can change the enthalpy drop and distort efficiency more than expected.
Using enthalpy data with confidence
Use the same property method for all states, especially when mixing superheated and wet regions. Keep water quality and moisture fraction assumptions aligned with the test procedure. Steam work is typically expressed as ṁ(h₁ − h₂), producing power in kW when ṁ is in kg/s and h is in kJ/kg. For gas or hydro tests, substitute appropriate specific energy terms while keeping units consistent.
Losses beyond the thermodynamic stage
The calculator separates thermodynamic performance from mechanical and generator losses. Mechanical efficiency accounts for bearings, seals, couplings, and gearbox losses. Generator efficiency captures electrical conversion losses, cooling loads, and heating. Multiplying these factors provides a realistic electrical output estimate for construction reporting. Use manufacturer curves when available, and document assumptions when using typical values.
Interpreting results and red flags
Isentropic efficiency is the primary indicator of stage health, nozzle condition, and internal leakage. Very low values can indicate inaccurate flow, wrong state points, valve throttling, or excessive moisture. Values close to 100% are unusual and should trigger verification of the isentropic outlet enthalpy. If overall efficiency is far below expectations, check auxiliary consumption and electrical metering points. Use the optional measured power input to benchmark the full system against the ideal reference.
Documentation and audit-ready exports
CSV export supports quick handover to spreadsheets for trend charts, daily logs, and QA sign-offs. PDF export provides a compact attachment for commissioning packages and client submittals. Keep notes with each run to link results to test conditions, valve positions, and instrument calibration dates. Capture ambient conditions and operating constraints, since they influence condenser pressure and enthalpy calculations. Consistent records make troubleshooting faster when performance changes during load ramping.
FAQs
1) What efficiency does this calculator report?
It reports isentropic efficiency, calculated electrical power, and optional overall efficiency versus ideal power using a measured electrical output value.
2) Why do I need both h₂,actual and h₂,s?
h₂,actual represents the real outlet state, while h₂,s represents the isentropic outlet state. Their difference separates real losses from ideal expansion.
3) What units should I use for enthalpy and flow?
Use kJ/kg for enthalpy and kg/s for mass flow. That combination yields turbine power directly in kW, matching most commissioning reports.
4) Can I use this for hydro turbines?
Yes, if you express the specific energy drop using comparable kJ/kg terms. For water, you can convert head to energy and enter equivalent values.
5) Why does the tool warn when h₂,actual < h₂,s?
For expansion, actual outlet enthalpy is usually higher than isentropic outlet enthalpy. A lower value may indicate inconsistent states or data entry errors.
6) How should I use the measured electrical output field?
Enter the tested electrical output to compare real plant performance against the ideal reference. This helps validate instrumentation, losses, and contractual guarantees.