.BuildingSystems.Utilities.Psychrometrics.TWetBul_TDryBulPhi

Information

This block computes the wet bulb temperature for a given dry bulb temperature, relative air humidity and atmospheric pressure.

If the constant approximateWetBulb is true, then the block uses the approximation of Stull (2011) to compute the wet bulb temperature without requiring a nonlinear equation. Otherwise, the model will introduce one nonlinear equation. The approximation by Stull is valid for a relative humidity of 5% to 99%, a temperature range from -20°C to 50°C and standard sea level pressure. For this range of data, the approximation error is -1 Kelvin to +0.65 Kelvin, with a mean error of less than 0.3 Kelvin.

Otherwise a calculation based on an energy balance is used. See #474 for a discussion. The model is validated in BuildingSystems.Utilities.Psychrometrics.Examples.TWetBul_TDryBulPhi.

For a model that takes the mass fraction instead of the relative humidity as an input, see BuildingSystems.Utilities.Psychrometrics.TWetBul_TDryBulXi.

References

Stull, Roland. Wet-Bulb Temperature from Relative Humidity and Air Temperature Roland Stull. Journal of Applied Meteorology and Climatology. Volume 50, Issue 11, pp. 2267-2269. November 2011 DOI: 10.1175/JAMC-D-11-0143.1

Contents

Name	Description
Medium	Medium model

Revisions

• March 6, 2023, by Michael Wetter:
  Added a constant in order for unit check to pass.
  See #1711 for a discussion.
• November 3, 2016, by Michael Wetter:
  Changed icon.
• May 24, 2016, by Filip Jorissen:
  Corrected exact implementation. See #474 for a discussion.
• October 3, 2014, by Michael Wetter:
  Changed assignment of nominal value to avoid in OpenModelica the warning alias set with different nominal values.
• November 20, 2013 by Michael Wetter:
  Updated model to use BuildingSystems.Utilities.Psychrometrics.Functions.saturationPressure() and BuildingSystems.Utilities.Psychrometrics.Functions.saturationPressureLiquid() as these functions have been moved from the medium to the psychrometrics package.
• October 1, 2012 by Michael Wetter:
  First implementation.