Dew point

Dew point is the temperature at which air becomes saturated with water vapor, which is dependent on the humidity and pressure of the air. When the dew point temperature falls below freezing it is called the frost point. Dew point is a key factor in the formation of dew, frost, fog, and clouds.

Overview

The dew point is the temperature to which air must be cooled to become saturated with water vapor. When further cooled, the airborne water vapor will condensate to form liquid water (dew). When air cools to its dew point through contact with a surface that is colder than the air, water will condense on the surface. When the temperature is below the freezing point of water, the dew point is called the frost point, as frost is formed rather than dew. The measurement of the dew point is related to humidity. A higher dew point means there will be more moisture in the air.

Calculation

The dew point of a sample of air can be calculated using both its temperature and its relative humidity, and the calculation relies on the principle that the air temperature decreases during the adiabatic expansion. The calculation of the dew point requires a dew point calculator or a dew point table.

Applications

The dew point is a critical measurement used to predict the formation of dew, frost, and fog. It is also used in forecasting weather, in the process of distillation, and in the HVAC industry to manage humidity levels in buildings.

See also

• Relative humidity
• Dew
• Frost
• Fog
• Clouds
• Distillation
• HVAC

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