hvac psychrometrics derived

{
  "input": {
    "body": {
      "dry_bulb": 95,
      "wet_bulb": 75,
      "elevation": 0
    },
    "type": "http",
    "method": "POST",
    "bodyType": "json"
  },
  "output": {
    "type": "json",
    "example": {
      "notes": [],
      "state": {
        "grains": 98.46,
        "density": 0.07092,
        "dry_bulb": 95,
        "enthalpy": 38.316,
        "wet_bulb": 75,
        "dew_point": 66.76,
        "humidity_ratio": 0.014065,
        "vapor_pressure": 0.325,
        "specific_volume": 14.2995,
        "relative_humidity": 39.82
      },
      "steps": [
        {
          "step": "Atmospheric pressure",
          "reference": "ASHRAE Handbook—Fundamentals (2021), Ch. 1 Psychrometrics, Eq. 3",
          "calculation": "p = 14.696 × (1 − 6.8754×10⁻⁶ × Z)^5.2559 = 14.696 × (1 − 6.8754×10⁻⁶ × 0)^5.2559 = 14.6960 psia"
        },
        {
          "step": "Humidity ratio",
          "reference": "ASHRAE Handbook—Fundamentals (2021), Ch. 1 Psychrometrics",
          "calculation": "pws(75.00 °F wet bulb) = 0.43007 psia (ASHRAE Ch. 1 Eq. 6)"
        },
        {
          "step": "Humidity ratio",
          "reference": "ASHRAE Handbook—Fundamentals (2021), Ch. 1 Psychrometrics",
          "calculation": "Ws* = 0.621945 × pws / (p − pws) = 0.018750 lb/lb (saturated at the wet bulb)"
        }
      ],
      "units": "IP",
      "pressure": 14.696,
      "elevation": 0,
      "next_calls": [
        {
          "why": "What load does a coil carry cooling this air to 55/54 °F at 1000 CFM?",
          "tool": "hvac_coil_load",
          "price": "$0.002",
          "arguments": {
            "units": "IP",
            "airflow": 1000,
            "leaving": {
              "dry_bulb": 55,
              "wet_bulb": 54
            },
            "entering": {
              "dry_bulb": 95,
              "wet_bulb": 75
            }
          }
        }
      ],
      "references": [
        "ASHRAE Handbook—Fundamentals (2021), Ch. 1 Psychrometrics"
      ],
      "inputs_used": {
        "dry_bulb": 95,
        "wet_bulb": 75
      },
      "unit_labels": {
        "area": "ft²",
        "load": "MBH (1,000 BTU/h)",
        "grains": "gr / lb dry air",
        "length": "in",
        "airflow": "CFM",
        "density": "lb / ft³",
        "enthalpy": "BTU / lb dry air",
        "pressure": "psia",
        "velocity": "FPM",
        "elevation": "ft",
        "condensate": "gal / h",
        "temperature": "°F",
        "friction_rate": "in. w.g. / 100 ft",
        "humidity_ratio": "lb water / lb dry air",
        "specific_volume": "ft³ / lb dry air",
        "relative_humidity": "%",
        "velocity_pressure": "in. w.g."
      }
    }
  }
}