P-T Data & Methodology

Data source and calculation method

The saturation curves were calculated during development using CoolProp 8.0.0, an MIT-licensed scientific property library, with its HEOS backend and nominal refrigerant compositions. CoolProp is not required at runtime.

The bundled curves use 1°F sampling steps within the −50°F to 130°F generation range. Each refrigerant and phase has its own supported pressure range. The app interpolates between stored points and rejects inputs outside that curve's range.

• Superheat: measured suction-line temperature minus vapor/dew saturation temperature.
• Subcooling: liquid/bubble saturation temperature minus measured liquid-line temperature.
• Pressure basis: gauge pressure relative to standard atmospheric pressure, 101,325 Pa; no altitude compensation.

The Basic and Advanced P-T tools share this reference basis. Temperature-difference conversions use the appropriate scale factor, without an absolute-temperature offset.

Verification

Regeneration with the pinned CoolProp version reproduced all 18 bundled curves byte for byte. At 160 supported intermediate-temperature check points, the largest interpolation difference from the direct model output was approximately 0.00264°F. These checks establish reproducibility and interpolation consistency; they do not establish the model's total physical uncertainty. We have not independently measured equilibrium properties at the exact commercial blend compositions.

Comparisons with published references

Property models and published charts can give different saturation values at the same pressure. The following differences were observed at supported comparison points; the sign is app minus the named reference.

Some points exceed the project's 0.5°F chart-comparison criterion. They remain documented reference exceptions, rather than passing agreement checks: R-454B bubble at 147 of 171 points (affected sample pressures approximately 27–450 psig); R-448A dew at 29 of 49 points (1–264 psig); and R-449A dew at 11 of 163 points (256–316 psig). These sampled ranges are not continuous limits or guaranteed maximum errors. Separate comparisons with the Honeywell 454B chart were within 0.5°F at the tested supported points.

The Chemours XL41 document identifies REFPROP Version 10 as its basis. The Honeywell charts and XP40 chart do not specify their complete model and interaction-parameter sets, so every difference cannot be assigned to a particular REFPROP version. The scientific model references are linked below; a newer model is not automatically more accurate for every composition and condition.

Consistent use with equipment documentation

For the same line-temperature measurement, the differences above make the affected subcooling or superheat result correspondingly lower. Near an entered target, the selected reference can change whether the result appears above or below that target. A one-decimal display does not imply accuracy to 0.1°F.

Use the P-T reference specified by the equipment manufacturer or your approved service procedure for the final charging decision. Do not apply a fixed offset to match a different chart. HVAC Charge Pro is a calculation/reference aid: superheat and subcooling values alone do not determine whether refrigerant should be added or removed. Verify instruments, units, refrigerant and measurements, and follow manufacturer instructions and applicable professional/safety requirements.

See the Engineering Disclaimer for the product's professional-use guidance.

Sources

• CoolProp 8.0.0 pinned source and MIT license
• Bell 2023: mixture-model research, NIST manuscript
• Chemours XL41 thermodynamic properties, engineering units
• Honeywell Solstice 454B P-T chart
• Honeywell Solstice N40 P-T chart
• Chemours XP40 P-T chart

Publication names identify reference sources and do not imply endorsement. No manufacturer chart, figure or complete numerical table is reproduced here.