These are dry-bulb temperature, wet-bulb temperature, dew-point temperature, relative humidity, humidity ratio, specific enthalpy, and specific volume. Pioneered by Carrier in 1904, the style of psychrometric chart with which we are familiar graphically depicts several parameters. Psychrometric processes include physical and thermodynamic properties such as dry-bulb temperature, wet-bulb temperature, humidity, enthalpy, and air density. The term comes from the Greek psuchron meaning “cold”, and “metron” meaning “means of measurement”.Īlthough the principles of psychrometry apply to any physical system consisting of gas-vapour mixtures, the most common system of interest is the mixture of water vapour and air, because of its application in HVAC and meteorology.Ī psychrometric chart is a graphical representation of the psychrometric processes of air. “Moist air is defined as a mixture of two gases: dry air and water vapour (the gas phase of H2O). “Psychrometrics is a sub-science of physics dealing with the properties and processes of moist air,” says ASHRAE.

If the psychrometric chart were a person, you might say its importance to the history of the HVAC&R profession is akin to that of James Harrison, Willis Carrier or Lord Kelvin himself.

Carrier Psychrometric Chart Pdf