Dew Point Temperature

on . Posted in Fluid Dynamics

Dew point, abbreviated as \(T_d\), is the temperature the air needs to be cooled to (at constant pressure) in order to achive a relative humidity of 100%.  It is a basic concept in meteorology and is used to describe the moisture content of the air.  It is a measure of atmospheric moisture or humidity.  When the air temperature drops to the dew point, the air is holding as much moisture as it can at that temperature, and any additional cooling will result in the condensation of water vapor into liquid water, such as dew, fog, or cloud droplets.

The dew point temperature is a critical parameter in weather forecasting because it helps meteorologists predict when and where condensation, fog, frost, or dew will occur.  When the air temperature approaches the dew point temperature, the relative humidity increases, and if they are the same, the air becomes saturated.  In practical terms, the dew point temperature is often used to describe how comfortable or uncomfortable the air feels.  When the dew point temperature is close to the actual air temperature, the air is humid, and it can feel muggy and uncomfortable.  Conversely, when the dew point is much lower than the air temperature, the air is dry and comfortable.  Meteorologists and weather reports often use the dew point temperature alongside relative humidity to provide a better understanding of the moisture content in the atmosphere and how it can affect weather conditions.


Dew point Temperature formula

\( T_d =  ( RH \;/\; 100 )^{ \frac{1}{8} }  \;   \left(  112 + 0.9 \; T  \right)  + 0.1 \; T - 112  \) 
Symbol English Metric
\( T_d \) = dew point temperature \(F\)  \(C\) 
\( RH \) = relative humidity \(F\)  \(C\) 
\( T \) = temperature \(F\)  \(C\) 


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Tags: Temperature HVAC