01
Canonical model and calculation order
PsychroField treats humid air as a perfect-gas mixture of dry air and water vapor. Saturation pressure uses retained water- and ice-region equations from the cited primary reference. State solving remains in SI at full numeric precision; unit conversion occurs only at input and output boundaries.
Each accepted independent pair is converted to a canonical dry bulb, humidity ratio and total pressure. All reported properties and chart coordinates derive from that one state object, preventing the chart and table from drifting apart.
02
What the 102 automated tests cover
The retained suite contains 102 passing tests. Categories cover published worked examples; saturation values around the water/ice boundary; all supported independent input pairs; dependent-pair, supersaturation and non-finite rejection; SI/IP round trips; elevation and pressure matrices; process conservation; two-stream mixing; and explicit failure behavior.
A passing count is not a blanket accuracy promise. Each fixture declares its expected value, source role and tolerance so a reviewer can see whether the test checks an identity, a rounded publication example or an independent library comparison.
03
Retained external checks
ASHRAE worked examples anchor equation interpretation and rounding context. Public NIST psychrometric calculation material supplies independent algorithmic and reference context. PsychroLib 2.5 and CoolProp 8 were run as comparison implementations without copying their source into the engine.
Where formulations or conventions differ, the evidence retains the difference instead of tuning one result to mimic another package. Tests use tolerances appropriate to the reference precision and numerical solve.
04
Supported range and rejection behavior
State dry bulb is supported from −80 °C to 200 °C, saturation calculations extend to −100 °C, and total pressure is accepted from 10 to 200 kPa. A state is rejected when saturation pressure approaches or exceeds total pressure, when RH leaves 0–100%, or when the property pair cannot uniquely define a state.
The interface associates errors with the relevant field, sets an invalid state for assistive technology and moves focus to the first invalid input after submission.
05
Known model limits
Enhancement factors, non-ideal high-pressure effects, droplets, fog, sorption, transient transport and chemical composition beyond dry air/water vapor are excluded. Elevation pressure follows a standard atmosphere and is not a weather measurement.
A single state cannot represent coil bypass, spray energy, fan work, leakage, duct gain, stratification or equipment controls. Use outputs for education, preliminary analysis and checking; verify safety, compliance and final design independently.
06
How to reproduce a claim
Record the route, software version, two input properties, pressure, unit system and displayed/exported result. Compare canonical SI values before comparing rounded display strings. For a process, also record start/end states, mode, flow basis and sign convention.
The source register explains why each publication was retained and what was not copied. Calculation defects can be reported through the contact route with a public comparison source.