# Steam Turbine Calculator

## U.S. Dept. of Energy | Energy Efficiency & Renewable Energy

**Click here to access the CALCULATOR.**

__U.S. Department of Energy Steam Turbine Calculator How-To__

This calculator can be used to produce rough approximations of power and/or steam flow given a set of conditions. Please note that this is a generic tool developed by the US Department of Energy, and that more precise results for Elliott steam turbine generators with controlled and/or uncontrolled extractions can be provided by contacting Elliott.

There are 2 common methods of use for the U.S. Department of Energy Steam Turbine Calculator:

*Calculate Steam Turbine (Generator) Power, given:*- Inlet Pressure
- Inlet Temperature
- Steam Flow
- Exhaust Pressure

*This is the most typical method when calculating ST output. Please see the section below titled “**1. Calculating Steam Turbine Power Given Steam Conditions and Flow**” for directions.

*Calculate Steam Flow, given:*- Inlet Pressure
- Inlet Temperature
- Exhaust Pressure
- Desired Power (kWe)

* Please see the section below titled “**2. Calculating Steam Flow Given Steam Conditions and Power**” for directions.

**Instructions**

**Please note: The U.S. DOE steam turbine calculator uses units of PSIG and °F. Though it sometimes shows °C for temperature, it will calculate as if your input was in °F.**

**1. Calculating Steam Turbine Power Given Steam Conditions and Flow**

- Set “Solve For” drop-down to
**Outlet Properties** - For Inlet Steam section:
**Enter Inlet Pressure (PSIG)****Enter Inlet Temperature (°F)**

- For Turbine Properties section:
- “Selected Turbine Property” drop-down to
**Mass Flow** **Enter Steam Mass Flow (klb/hr [e.g. 36,000 lbm/hr = 36.0 klbm/hr])**- Enter assumed
**isentropic efficiency (see Table 1 below)** - Enter assumed generator efficiency of
**93%**(takes gearbox losses and generator losses into account)

- “Selected Turbine Property” drop-down to
- For Outlet Steam section:
- Enter desired
**Exhaust Pressure (PSIG)**- If condensing exhaust condition, pressure units must be converted to PSIG (See Table 1 for basic conversions)

- Enter desired

**2. Calculating Steam Flow Given Steam Conditions and Power**

- Set “Solve For” drop-down to
**Outlet Properties** - For Inlet Steam section:
**Enter Inlet Pressure (PSIG)****Enter Inlet Temperature (°F)**

- For Turbine Properties section:
- “Selected Turbine Property” drop-down to
**Power Out** - Enter assumed
**isentropic efficiency (see Table 1 below)** - Enter assumed generator efficiency of
**93%**(takes gearbox losses and generator losses into account) **Enter desired power at the generator (kWe [electrical power])**

- “Selected Turbine Property” drop-down to
- For Outlet Steam section:
- Enter desired
**Exhaust Pressure (PSIG)**- If condensing exhaust condition, pressure units must be converted to PSIG (See Table 1 for basic conversions)
****

- If condensing exhaust condition, pressure units must be converted to PSIG (See Table 1 for basic conversions)

- Enter desired

__Table 1:__**Exhaust Pressure Conversion Table**

inHgA |
PSIG |

4 | -12.7354 |

6 | -11.7561 |

8 | -10.7708 |

__Table 2:__**Estimated Isentropic Efficiencies of Steam Turbines**

Turbine Type |
Exhaust Type |
Average (%) |

Single Stage | Back Pressure | 53 |

Single Stage | Condensing | 57 |

Multi-Stage <10 MW | BackPressure | 60 |

Multi-Stage <10 MW | Condensing | 67 |

Multi-Stage > 10 MW | Back Pressure | 75 |

Multi-Stage > 10 MW | Condensing | 80 |

**Note:** Isentropic efficiencies of Steam Turbines can range from 20-90%. The efficiencies in Table 1 are simplified values for the purpose of estimating industrial type Steam Turbine Generators. For firm performance values please contact the Power Generation Team at Elliott Group.