The other important variable in what affects dew point is the pressure, which is where Pressure Dew Point (PDP) comes into play.Īs a rule of thumb (without the use of complex equations), compression increases/raises the dew point temperature and expansion/decompression lowers the dew point. Many readily found formulas on dew point are formulas for atmospheric dew point, as they focus solely on temperature and the amount of gas (eg. The common use of the term "dew point" is actually the "Atmospheric Dew Point" which doesn't take account the pressure of a system, as it's presumed to be at 1 atm.
$R$ = the gas constant = $8.3145\ J/mol \cdot K$ \ln\frac$ = enthalpy of vaporization in $J/mol$ If you have the vapor pressure $P_1$ of a pure substance at one temperature $T_1$ you can calculate the vapor pressure $P_2$ at a second temperature $T_2$ using the Clausius-Clapeyron equation: This is why water boils at 82 C instead of 100 C on Everest- because the atmospheric pressure is lower: If you reduce the pressure of the surrounding gas, then you do not need to raise the temperature of the liquid as much anymore. As you raise the temperature of a liquid, the vapor pressure increases until it equals the pressure of the surrounding gas at which point it boils.
Liquids boil when the vapor pressure of the liquid equals the pressure of the surrounding gas (e.g. Both are the same temperature for a given pressure. For single-component liquids, boiling point = condensation point.
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