Psychrometrics is the science of the thermodynamic properties of moist air — the combination of dry air and water vapor. HVAC engineers use psychrometric analysis to understand how air behaves as it is heated, cooled, humidified, and dehumidified.
Key psychrometric properties include: dry bulb temperature (what a standard thermometer reads), wet bulb temperature (related to evaporative cooling potential), dew point (temperature at which moisture condenses), relative humidity, humidity ratio (pounds of water vapor per pound of dry air), and enthalpy (total heat content).
Psychrometric charts graphically represent these relationships and are used to analyze HVAC processes, diagnose comfort problems, design ventilation systems, and determine proper equipment sizing for latent (dehumidification) loads. Understanding psychrometrics is fundamental for advanced HVAC design and troubleshooting.