FieldEngineersKitEngineering Reference & ASME Code Basis
1. Core Formula & Variable Definitions
IAPWS-IF97 Industrial Formulation for the Thermodynamic Properties of Water and Steam · ASME Steam Tables (IAPWS-IF97 basis) · ISO 80000-5 (Thermodynamics Quantities)
h = R · T · τ · (γτ0 + γτr) [kJ/kg]
s = R · [τ · (γτ0 + γτr) − (γ0 + γr)] [kJ/(kg·K)]
v = R · T · π · (γπ0 + γπr) / p [m³/kg] · ρ = 1/v
IAPWS-IF97 Region 2 superheated · Region 4 saturation (Tsat, wet steam with quality x)
Steam thermodynamic properties from the IAPWS-IF97 industrial formulation. Saturation mode uses Region 4 Tsat(P) with quality x between liquid (Region 1) and vapor (Region 2). Superheated mode evaluates Region 2 Gibbs free energy at T and P (T ≥ Tsat). Scope ends at Pc = 22.064 MPa.
- h (Specific enthalpy) — Steam enthalpy from Gibbs free energy (kJ/kg or Btu/lb).
- s (Specific entropy) — Steam entropy (kJ/(kg·K) or Btu/(lb·°F)).
- v / ρ (Specific volume / density) — v from π·γ_π; ρ = 1/v.
- Tsat (Saturation temperature) — Region 4 backward Tsat(P) on the saturation line.
- x (Steam quality) — Dryness fraction 0 (sat. liquid) to 1 (sat. vapor).
- hfg (Latent heat) — hg − hf at the saturation pressure.
2. Screening Rules Matching This Calculator
Returns IAPWS-IF97 steam properties at a single (P, T) or saturation point with quality x. Critical and supercritical states above Pc are out of scope.
h, s, v mix between sat. liquid (Region 1) and sat. vapor (Region 2) at Tsat.
Single-phase vapor evaluation at absolute P and T above the saturation line.
Stay below critical Pc = 22.064 MPa (220.64 bar). Imperial inputs convert via UnitSwitcher.
Pressures at/above Pc and non-H₂O fluids need full ASME steam tables or mixture property data.
Quick Reference Lookup Table
| Duty | P | State | h | Tsat / ρ | v |
|---|---|---|---|---|---|
| Default | 10 bar | Sat. vapor x=1 | 2777.1 kJ/kg | 179.88 °C | 0.1944 m³/kg |
| pSEO | 20 bar · 300 °C | Superheated R2 | 3024 kJ/kg | 7.97 kg/m³ | 0.1255 m³/kg |
| pSEO | 3 bar | Sat. vapor x=1 | 2724.9 kJ/kg | 133.52 °C | 0.6058 m³/kg |
| pSEO | 15 bar · 250 °C | Superheated R2 | 2924 kJ/kg | 6.58 kg/m³ | 0.1520 m³/kg |
| Imperial | 145 psi | Sat. vapor | ~1194 Btu/lb | ~356 °F | — |
| Imperial | 290 psi · 572 °F | Superheated | ~1300 Btu/lb | ~7.97 kg/m³ | — |
Values from IAPWS-IF97 Region 2 / 4 evaluation in this app. Spec sheet density at 20 bar · 300 °C uses IF97 ρ ≈ 7.97 kg/m³ (not ideal-gas estimates).
3. Applicability & Phase Limits
Pure water / steam (H₂O) only. Phase and region boundaries — not metallurgy — govern validity.
| Group / Regime | Range / Condition | Limit / Criterion | Engineering Notes |
|---|---|---|---|
| Saturated steam (Region 4 + x) | Tsat(P) | 0 ≤ x ≤ 1 | Hero h with Tsat for saturation duties. Wet steam uses quality mixing at Tsat. |
| Superheated steam (Region 2) | T > Tsat(P) | Subcritical P only | Hero h with density ρ for superheat. Confirm T ≥ Tsat before treating as single-phase vapor. |
| Subcooled liquid / condensate | T < Tsat(P) | Use water-thermodynamic-properties | Liquid-only duties belong in the Region 1 liquid calculator — not this steam tool. |
| Supercritical & near-critical | P ≥ 22.064 MPa | Out of scope | Region 3 and supercritical states are outside this app — open full IAPWS / ASME tables. |
Code Applicability & Safety Boundaries
- IAPWS-IF97 Region 2 / 4 screening — not a certified steam-table printout
- Pure H₂O only; dissolved solids and glycol shift properties and are not modeled
4. Step-by-Step Worked Example
Field VerificationShowHide
Worked example — 10 bar saturated dry steam
Look up saturated steam enthalpy and density at 10 bar abs for heat-balance / line sizing screening.
Find Tsat
Evaluate dry vapor
Read hero
5. How to look up IAPWS-IF97 steam properties
- 1
Select unit system
Use the navbar UnitSwitcher for metric (bar, °C) or imperial (psi, °F).
- 2
Enter absolute pressure
Stay within 0.01–100 bar abs (below critical 22.064 MPa).
- 3
Choose saturation or superheated
Saturation: set dryness x. Superheated: set T ≥ Tsat.
- 4
Read h hero and property rows
Hero shows enthalpy with Tsat (sat.) or density (superheat). Rows list hfg, s, μ, and k.
6. Frequently Asked Questions & Technical References
ShowHide
A tool that evaluates steam enthalpy, entropy, density, Tsat, and latent heat from the IAPWS-IF97 industrial formulation used by ASME steam tables.
Use saturation on the two-phase line with quality x. Use superheated when steam temperature is above Tsat at the given absolute pressure (Region 2).
No. Pressures at or above 22.064 MPa are outside Region 2/4 scope — verify with a full ASME steam table.
At Tsat(P): h = hf + x·(hg − hf) (same mixing for s and v).