BuildSysPro.IBPSA.Utilities.Psychrometrics.Functions.X_pW

# .BuildSysPro.IBPSA.Utilities.Psychrometrics.Functions.X_pW

Mass fraction for given water vapor pressure

## Information

Function to compute the mass fraction for a given water vapor partial pressure.

#### Interface

>     function X_pW
>       extends Modelica.Icons.Function;
>       input Modelica.Units.SI.Pressure p_w(displayUnit = "Pa", min = 0.003, nominal = 1000) "Water vapor pressure";
>       input Modelica.Units.SI.Pressure p = 101325 "Total pressure";
>       output Modelica.Units.SI.MassFraction X_w(min = 0, max = 1, nominal = 0.01) "Species concentration at dry bulb temperature";
>     end X_pW;

## Revisions

- February 14, 2021 by Ettore Zanetti:
  Updated description.
- September 16, 2013 by Michael Wetter:
  Added attributes to variable `p_w`.
- March 9, 2012 by Michael Wetter:
  Added `smoothOrder=99` and `displayUnit` for pressure.
- February 17, 2010 by Michael Wetter:
  Renamed block from `HumidityRatio_pWat` to `X_pW`.
- April 14, 2009 by Michael Wetter:
  Converted model to block because `RealInput` are obsolete in Modelica 3.0.
- August 7, 2008 by Michael Wetter:
  First implementation.

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