Last edited 18 Sep 2014

Psychrometric charts

Psychrometric charts are complex graphs that can be used to assess the physical and thermodynamic properties of gas-vapour mixtures at a constant pressure. They are often used to assess the properties of moist air. This can be useful in the design of heating, ventilation and air-conditioning systems for buildings, and psychrometric charts often include a zone in the middle that represents the range of conditions that people find comfortable under different circumstances (such as summer and winter).

Typically, the properties represented on psychrometric charts are:

The state of moist air can be determined from any two of these properties, from which all other properties can then be determined.

Atmospheric pressure varies with altitude and so a number of psychrometric charts are available for different atmospheric pressures, however, for altitudes of less than 600m the sea-level psychrometric chart is often considered adequate.

800px-PsychrometricChart SeaLevel SI svg.png

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