BuildSysPro.IBPSA.Utilities.Psychrometrics.Functions.phi_pTX

# .BuildSysPro.IBPSA.Utilities.Psychrometrics.Functions.phi_pTX

Relative humidity for given pressure, dry bulb temperature and moisture mass fraction

## Information

Relative humidity of air for given pressure, temperature and water vapor mass fraction.

Note that the water vapor mass fraction must be in kg/kg total air, and not dry air.

#### Interface

>     function phi_pTX
>       extends Modelica.Icons.Function;
>       input Modelica.Units.SI.Pressure p "Absolute pressure of the medium";
>       input Modelica.Units.SI.Temperature T "Dry bulb temperature";
>       input Modelica.Units.SI.MassFraction X_w "Water vapor mass fraction per unit mass total air";
>       output Real phi(unit = "1") "Relative humidity";
>     end phi_pTX;

## Revisions

- April 4, 2019 by Filip Jorissen:
  Added inverse annotation for #1110.
- November 17, 2014 by Michael Wetter:
  Removed test that constrains the saturation pressure to be lower than `p`. I do not see any numerical problems without this test.
- November 13, 2014 by Michael Wetter:
  First implementation.

Generated at 2026-05-12T20:19:03Z by OpenModelicaOpenModelica 1.26.7 using GenerateDoc.mos