Psychrometric Properties
Enter air properties and click Calculate to see psychrometric properties.
Common HVAC Processes
Sensible Heating/Cooling
Horizontal line on chart. W constant, T changes.
Humidification
Vertical line on chart. T constant, W increases.
Adiabatic Saturation
Along constant wet bulb line. h constant.
Dehumidification
Cool below dew point, remove condensate.
Key Definitions
Dry Bulb (Tdb)Temperature measured by a standard thermometer
Wet Bulb (Twb)Temperature measured with a wet wick - indicates evaporative cooling potential
Dew Point (Tdp)Temperature at which condensation begins (100% RH)
Humidity Ratio (W)Mass of water vapor per mass of dry air (kg/kg or g/kg)
Relative HumidityRatio of actual vapor pressure to saturation pressure (0-100%)
Enthalpy (h)Total heat content per unit mass of dry air (kJ/kg)
ASHRAE 55 Comfort Zone
Summer (Light clothing)
- • Temperature: 23-26°C (73-79°F)
- • Humidity: 30-60% RH
- • Air velocity: 0.15-0.25 m/s
Winter (Heavy clothing)
- • Temperature: 20-24°C (68-75°F)
- • Humidity: 30-60% RH
- • Air velocity: 0.1-0.15 m/s
Presets
Calculation Type
Input Parameters
Atmospheric Pressure
Standard: 101.325 kPa (sea level)
• Sea level: 101.325 kPa
• 500m altitude: ~95.5 kPa
• 1000m altitude: ~89.9 kPa
• 2000m altitude: ~79.5 kPa