Psychrometrics reference
Psychrometric Properties Reference
Definitions, units, and boundaries for common moist-air values.
Variables and units
| Variable | IP | SI | Condition |
|---|---|---|---|
| Dry bulb | °F | °C | Measured air temperature |
| Relative humidity | % | % | Requires temperature |
| Dew point | °F | °C | Moisture state at saturation |
| Humidity ratio | lbw/lbda | g/kgda | Requires total pressure |
| Enthalpy | Btu/lbda | kJ/kgda | Reference-state dependent |
| Wet bulb | °F | °C | Pressure and method dependent |
Using the table
State dry bulb, moisture input, and total pressure before comparing properties. At standard pressure, 24°C and 50% RH is one example state; use the calculator rather than treating a reference definition as a fixed property value.
Limits and calculator
These definitions do not replace a full psychrometric chart or project-specific moisture analysis. Use the Psychrometric Calculator for a documented state and then connect results to the HVAC Load Calculator where relevant.