Calculator
Example Data Table
| Temperature | Pressure | Saturation temperature | Degree of superheat | Estimated entropy | State note |
|---|---|---|---|---|---|
| 200 °C | 5.00 bar | 149.931 °C | 50.069 °C | 7.11204 kJ/kg·K | Superheated state confirmed. |
| 300 °C | 10.00 bar | 176.397 °C | 123.603 °C | 7.17677 kJ/kg·K | Superheated state confirmed. |
| 450 °C | 20.00 bar | 209.919 °C | 240.081 °C | 7.33240 kJ/kg·K | Superheated state confirmed. |
Formula Used
This page applies a practical engineering entropy estimate for superheated steam:
s ≈ sref + ∫(cp/T)dT − R ln(P/Pref)
For lower temperatures, the calculator uses a reference-state path with a representative heat-capacity value. For higher temperatures, it adds a temperature-dependent entropy increment. Pressure correction follows the logarithmic ideal-gas relation.
log10(P) = A − B / (T + C)
The second expression estimates saturation temperature, which lets the page report the degree of superheat. Use it for design checks, education, screening, and quick comparisons.
How to Use This Calculator
- Enter steam temperature and choose the matching unit.
- Enter pressure and select bar, kPa, MPa, or psi.
- Optionally name the case for exported files.
- Click the calculate button.
- Read entropy, saturation temperature, degree of superheat, and auxiliary outputs.
- Use the graph to see how entropy changes at the same pressure.
- Download the result summary in CSV or PDF format.
- Confirm final design values with detailed steam tables when needed.
FAQs
1) What does this calculator estimate?
It estimates the specific entropy of superheated steam from temperature and pressure, then reports related checks such as saturation temperature, degree of superheat, density, and specific volume.
2) Why does pressure affect entropy?
At the same temperature, raising pressure reduces the available molecular spacing. That lowers the entropy estimate, which is why the pressure correction term subtracts from the reference path.
3) What is degree of superheat?
It is the difference between the entered temperature and the saturation temperature at the same pressure. A positive value indicates the state is superheated.
4) Can I use psi and Fahrenheit?
Yes. The form accepts psi, kPa, MPa, and bar for pressure, plus Celsius, Kelvin, and Fahrenheit for temperature. Internally, the page converts them to consistent units.
5) Is this suitable for final plant design?
Use it for quick engineering screening, training, and comparison work. For contractual design, equipment guarantees, or compliance calculations, confirm values with detailed steam-property software or tables.
6) Why might the state note say not superheated?
That message appears when the entered temperature is at or below the estimated saturation temperature for the selected pressure. Increase temperature or reduce pressure to move into the superheated region.
7) What does the graph show?
The graph shows estimated entropy against temperature at the entered pressure. It helps you inspect the local trend and compare the current operating point with nearby temperatures.
8) Why include specific volume and density?
Those outputs help with broader steam-system review. They are useful for checking flow behavior, equipment sizing, and whether the entered operating point is physically reasonable.