Humidity and hygrometry
Cloud forest mount kinabalu-withHygrom.jpg
Specific concepts
General concepts
Measures and Instruments

Psychrometrics, psychrometry, and hygrometry are names for the field of engineering concerned with the physical and thermodynamic properties of gas-vapor mixtures. The term comes from the Greek psuchron (ψυχρόν) meaning "cold"[1] and metron (μέτρον) meaning "means of measurement".[2]

Common applications

Although the principles of psychrometry apply to any physical system consisting of gas-vapor mixtures, the most common system of interest is the mixture of water vapor and air, because of its application in heating, ventilating, and air-conditioning and meteorology. In human terms, our thermal comfort is in large part a consequence of not just the temperature of the surrounding air, but (because we cool ourselves via perspiration) the extent to which that air is saturated with water vapor.

Many substances are hygroscopic, meaning they attract water, usually in proportion to the relative humidity or above a critical relative humidity. Such substances include cotton, paper, cellulose, other wood products, sugar, calcium oxide (burned lime) and many chemicals and fertilizers. Industries that use these materials are concerned with relative humidity control in production and storage of such materials.

In industrial drying applications, such as drying paper, manufacturers usually try to achieve an optimum between low relative humidity, which increases the drying rate, and energy usage, which decreases as exhaust relative humidity increases. In many industrial applications it is important to avoid condensation that would ruin product or cause corrosion.

Molds and fungi can be controlled by keeping relative humidity low. Wood destroying fungi generally do not grow at relative humidities below 75%.

Other Languages
العربية: قياس الرطوبة
català: Psicrometria
Deutsch: Psychrometrie
Ελληνικά: Υγρομετρία
español: Psicrometría
français: Psychrométrie
hrvatski: Psihrometrija
italiano: Psicrometria
português: Psicrometria
srpskohrvatski / српскохрватски: Psihrometrija
Türkçe: Psikrometri