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The dew point temperature equals the air temperature when the air is saturated with water; in all other cases the dew point will be less than the air temperature. [ 6 ] : 129 In technical terms, the dew point is the temperature at which the water vapor in a sample of air at constant barometric pressure condenses into liquid water at the same ...
In food science, water activity (a w) of a food is the ratio of its vapor pressure to the vapor pressure of water at the same temperature, both taken at equilibrium. [1] Pure water has a water activity of one. Put another way, a w is the equilibrium relative humidity (ERH) expressed as a fraction instead of as a percentage.
The analysis here shows the simple unattributed formula and the Antoine equation are reasonably accurate at 100 °C, but quite poor for lower temperatures above freezing. Tetens is much more accurate over the range from 0 to 50 °C and very competitive at 75 °C, but Antoine's is superior at 75 °C and above.
The conversion equations depend on the temperature at which the conversion is wanted (usually about 20 to 25 degrees Celsius). At an ambient air pressure of 1 atmosphere (101.325 kPa), the general equation is: = / ()
The Antoine equation is a class of semi-empirical correlations describing the relation between vapor pressure and temperature for pure substances. The Antoine equation is derived from the Clausius–Clapeyron relation. The equation was presented in 1888 by the French engineer Louis Charles Antoine (1825–1897). [1]
The Goff–Gratch equation is one (arguably the first reliable in history) amongst many experimental correlation proposed to estimate the saturation water vapor pressure at a given temperature. Another similar equation based on more recent data is the Arden Buck equation .
The Tetens equation is an equation to calculate the saturation vapour pressure of water over liquid and ice. It is named after its creator, O. Tetens who was an early German meteorologist. It is named after its creator, O. Tetens who was an early German meteorologist.
Xchanger Inc, webpage Calculator for humidity, dew point, mass flows & heat flux for variable pressure systems with compressors, blowers, vacuum pumps and heat exchangers. Corwin's Calculators Calculator for humidity, dew point. How to read and use a psychrometric chart; Free Online Interactive Psychrometric Chart