Psychrometric Chart Tool implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-with-binding-errata

Evidence ID

t6-003

Effect

Computation or source lookup only

Input and validation requirements

The tool has a real undefined-result failure at P-p_v=0, and exactly zero relative humidity produces a non-finite dew point. The supplied specification also does not state the water/ice saturation branch or the unit conventions for temperature and humidity ratio, so different plausible interpretations produce different states.

Required corrections

[
  {
    "vector": "2,4",
    "field": "saturation_pressure_kPa (+vapor)",
    "wrong": 2.33434,
    "correct": 2.33344,
    "cause": "digit transposition in pws(20) under her own stated Magnus constants (0.61094*e^1.34010=2.33344)"
  }
]

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "dry_bulb_C": 25,
    "relative_humidity": 0.5,
    "pressure_kPa": 101.325,
    "saturation_correlation": "Magnus: 0.61094 exp(17.625T/(T+243.04))"
  },
  "expected_outputs": {
    "saturation_pressure_kPa": 3.16176,
    "vapor_pressure_kPa": 1.58088,
    "humidity_ratio_kg_per_kg_da": 0.0098595,
    "dew_point_C": 13.86,
    "wet_bulb_C": 17.9,
    "enthalpy_kJ_per_kg_da": 50.267,
    "specific_volume_m3_per_kg_da": 0.85707
  },
  "working": "pws(25)=0.61094·exp(17.625·25/(25+243.04))=3.16176 kPa. pv=0.5·3.16176=1.58088 kPa. W=0.622·1.58088/(101.325−1.58088)=0.983308/99.74412=0.00985950. Dew point: L=ln(1.58088/0.61094)=0.95070; Td=243.04L/(17.625−L)=13.8600 °C. Wet bulb uses Newton's method on f(Twb)=Ws(Twb)−0.622·0.00066·(1+0.00115Twb)(25−Twb)−0.00985950, tolerance 1e−6 °C: Twb(0)=15.0000 °C; Twb(1)=18.0200 °C; Twb(2)=17.9011 °C; Twb(3)=17.9000 °C; converged Twb=17.9000 °C. h=1.006·25+0.00985950·(2501+1.86·25)=25.1500+0.00985950·2547.50=50.2670 kJ/kg_da. v=0.287042·298.15·(1+1.607858·0.00985950)/101.325=0.857070 m³/kg_da."
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche6/tranche6-results.json
• tranche errata record