Key Psychrometric Properties
- Dry Bulb Temperature (DBT): The temperature of air measured by a thermometer freely exposed to the air
- Wet Bulb Temperature (WBT): The lowest temperature that can be reached by evaporative cooling
- Dew Point Temperature: The temperature at which air becomes saturated when cooled
- Relative Humidity (RH): The ratio of actual water vapor pressure to saturation vapor pressure
- Humidity Ratio: The mass of water vapor per unit mass of dry air (kg/kg)
- Specific Enthalpy: The total heat content of moist air per unit mass of dry air
Common HVAC Processes
- Sensible Heating/Cooling: Change in dry bulb temperature at constant humidity ratio
- Humidification/Dehumidification: Change in humidity ratio at constant dry bulb temperature
- Cooling and Dehumidification: Combined process typical of air conditioning
- Adiabatic Mixing: Combining two air streams to produce a mixed condition
Psychrometric Chart Interpretation
The psychrometric chart is a graphical representation of the thermodynamic properties of moist air.
Key lines include dry bulb temperature (x-axis), humidity ratio (y-axis), relative humidity curves,
constant enthalpy lines, and constant wet bulb temperature lines. HVAC processes can be visualized
as paths between points on the chart.
