What “IF97” means for the numbers you see on this page
Industrial steam balances often start from IAPWS-IF97. Pair with the piping preliminary design scenario for line sizing (/tools/scenarios/piping-prelim) or pressure-drop checks when you have consistent ρ and μ.
Model assumptions & validity
- Thermodynamic surface: IAPWS Industrial Formulation 1997 for the Helmholtz energy (IF97) with regional equations (r1 liquid, r2 vapor, r4 saturation, etc.) as implemented by the bundled EOS library.
- Transport properties (μ, k) follow the supplementary IAPWS releases referenced by the library; treat them as high-quality estimates for engineering screening, not metrology-grade values without your own validation plan.
- Modes: saturation by T or P returns two-phase property tables at the saturation line; single-phase mode solves (p, T) in the subcooled / superheated / supercritical region subject to library bounds.
- Stay within the IAPWS IF97 published range for the task; states extremely close to the critical point or triple point can amplify numerical sensitivity—cross-check against certified software for custody or safety-margin studies.
- No chemistry: dissolved gases, salinity, and non-condensable gas effects on saturation temperature are not modeled.
Standards & references
- IAPWS IF97 — see existing references.
- Related workflow: /tools/scenarios/piping-prelim for pipe sizing and /tools/pressure-drop for incompressible line loss screening.
Shareable URL (mode + SI state)
The shareable URL sets query key m to sat_t, sat_p, or super—saturation from temperature, from pressure, or superheated single-phase (same meaning as Sat(T) / Sat(P) wording in the UI; these are fixed URL tokens, not function-call syntax). It also encodes pPa (absolute pressure, Pa) and tK (kelvin). Example: temperature-based saturation uses m=sat_t with tK only; superheated states need a self-consistent p and T pair. After opening a link, wait for local settings to hydrate, then press Calculate to regenerate tables.
Frequently asked questions
- Is this the same as ASME steam tables?
- It is built on the same IAPWS-IF97 formulation that ASME-compatible steam tables derive from, but any printed table differs by rounding, interpolation grid, and transport-property submodels. Use this tool for reproducible digital checks; cite IAPWS IF97 when documenting assumptions.
- Why do transport properties differ slightly from my Mollier chart?
- Charts interpolate graphically and may use older releases or simplified viscosity correlations. Small deviations in μ and k are normal; enthalpy and density along IF97 should still be tight for screening.
- Can I use results directly for safety valve sizing?
- Only as one input to a code-compliant procedure. Relief sizing depends on accumulation, backpressure, discharge coefficients, and applicable ASME/API rulesets beyond pure property evaluation.
- Does the tool send my process conditions to a server?
- No. The EOS executes in your browser session; shareable links only encode numbers in the URL that you explicitly copy.
- What do the URL tokens m=sat_t, m=sat_p, and m=super mean?
- sat_t: saturation table keyed by temperature (supply tK). sat_p: saturation keyed by absolute pressure (supply pPa). super: single-phase superheated (or general single-phase) state—supply a consistent absolute pressure and temperature pair. All pressures in links are absolute pascals.
- When should I distrust a single grid value without a second cross-check?
- Near the critical point, at very low pressures, or when dissolved gas shifts the true saturation temperature, tabulated IF97 alone may not represent your field fluid. Treat outputs as model-based screening unless validated against measurements or code-prescribed software.
Extended copy on this page (headings, assumptions, references, FAQs) may be drafted or localized with AI assistance; engineering judgment and governing codes still apply. Numerical models run locally in your browser as implemented. For contract-critical work, cite primary standards and qualified review.