Damppdruk

Damppdruk is the partial pressure of water vapor in a gas mixture, most commonly in air. It describes how much moisture is present in the air independent of other gases and is determined by temperature and moisture load. At a given temperature, the damppdruk cannot exceed the saturation vapor pressure, p_v^sat(T); when it reaches this value the air is saturated with water vapor.

The relationship between damppdruk and humidity is often expressed through relative humidity (RH). Relative humidity is the ratio of the actual damppdruk to the saturation vapor pressure at the current temperature, multiplied by 100%. In practical terms, RH = (p_v / p_v^sat(T)) × 100%. Units for damppdruk include pascals (Pa), kilopascals (kPa), and hectopascals (hPa). For reference, at 20°C the saturation vapor pressure is about 2.34 kPa; an indoor RH of 50% corresponds to a damppdruk of roughly 1.17 kPa.

Damppdruk is measured with hygrometers, dew point sensors, or psychrometric methods (dry- and wet-bulb thermometers). Modern devices use capacitive or resistive sensors or chilled-mirror dew point technology.

Applications and significance vary by field. In meteorology, damppdruk influences dew point, fog, and precipitation. In building services and industrial processes, controlling damppdruk is essential to prevent condensation, mold growth, and corrosion, or to optimize drying and storage of hygroscopic materials. In steam and HVAC systems, managing damppdruk affects energy efficiency and system performance, linking humidity control to comfort and safety.