Water Vapor Pressure

on . Posted in Fluid Dynamics

Water vapor pressure is the pressure exerted by water vapor molecules when they are in equilibrium with liquid water at a given temperature.  It represents the partial pressure of water vapor in a mixture of gases, such as air, when the air is saturated with moisture at a specific temperature.

The concept of water vapor pressure is important in meteorology, as it plays a significant role in the formation of weather phenomena like clouds, precipitation, and humidity levels.  The higher the temperature, the more water vapor the air can hold, so the water vapor pressure increases with rising temperatures.  The relationship between temperature and water vapor pressure follows the Clausius-Clapeyron equation, which describes how the saturation vapor pressure changes with temperature.  This relationship is fundamental in understanding and predicting weather patterns and is also relevant in various fields, including chemistry, biology, and engineering.


Water Vapor Pressure formula

\( p =  10^{\; A - ( B \;/\;  C + T ) }  \) 
Symbol English Metric
\( p \) = vapor pressure of water \(lbf\;/\;in^2\) \(Pa\)
\( A \) = Antoine constant for water \(dimensionless\)
\( B \) = Antoine constant for water \(dimensionless\)
\( C \) = Antoine constant for water \(dimensionless\)
\( T \) = water temperature \(F\) \(C\)


Antoine Constants for Water

Water Temperature A B C
1 to 100 degrees celsius 8.07131 1730.63 233.426
99 to 374 degrees celsius 8.14019 1810.94 244.485


P D Logo 1

Tags: Pressure Water Vapor