14 TRG-TRC001-EN
notes
period one
The Psychrometric Chart

The psychrometric chart now defines these five properties of air: dry-bulb

temperature (vertical lines), humidity ratio and dew-point temperature

(horizontal lines), relative humidity (curved lines) and wet-bulb temperature

(diagonal lines).

Remember: if any two of these five air conditions are known, the other three

can be found on the psychrometric chart by locating the point of intersection of

the two known conditions.

There is one more property of air that is displayed on the psychrometric chart—

specific volume. Specific volume is defined as the volume of one pound of

dry air at a specific temperature and pressure. As one pound of air is heated it

occupies more space—the specific volume increases.

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