Version v1.2 · 2026-10-14
Nine pure fluids are fitted in the library — H₂O, NH₃, CH₃OH, R134a, R22, R124, R32, R218 and CO₂ — since every pair model needs the pure-refrigerant saturation line as its endpoint. Two fitting routes are used. For R134a and R22, Wagner-form equations were fitted to the reference equations of state as implemented in CoolProp (maximum deviations 0.031% and 0.0065%). For the other seven, compact fits were made to the NIST WebBook saturation tables: the adopted form is a seventh-degree polynomial for ln P in t (°C), with a Wagner-type form as the trial alternative, and sixth-degree polynomials for the liquid and vapour enthalpies. All enthalpies are shifted to a single datum, hliq(0 °C) = 100 kJ/kg, the shift changing only the constant term and leaving latent heats unchanged. For ammonia, the adopted polynomial gives a maximum deviation of 0.0272% over the full table range (−77 to 132 °C) and 0.0027% over the working band (−50 to +60 °C), with anchors Pref(25 °C) = 1.00269 MPa and Tsat(0.101325 MPa) = 239.83 K. For CO₂ the adopted polynomial gives 0.0099% over −56 to 30 °C.
Table 2. Pure-fluid saturation fits (library).
| Fluid | Points | Table range (°C) | Max. deviation of Pref vs. source table |
|---|---|---|---|
| H₂O | 373 | 1–373 | 0.0291% |
| NH₃ | 210 | −77–132 | 0.0272% |
| CH₃OH | 330 | −90–239 | 0.1064% |
| R134a | (reference EOS) | −50–95 | 0.031% |
| R22 | (reference EOS) | −50–90 | 0.0065% |
| R124 | 276 | −40–110 (adopted fit) | 0.111% |
| R32 | 215 | −136–78 | 0.0609% |
| R218 | 219 | −147–71 | 0.1495% |
| CO₂ | 601 | −56–30 | 0.0099% |