blockpW_TDewPoi

Model to compute the water vapor pressure for a given dew point temperature of moist air
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Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Information

Block to compute the water vapor pressure for a given dew point temperature.

The correlation used in this model is valid for dew point temperatures between 0°C and 30°C. It is an approximation to the correlation from 2005 ASHRAE Handbook, p. 6.2, which is valid in a wider range of temperatures and implemented in Buildings.Utilities.Psychrometrics.Functions.pW_TDewPoi. The approximation error of this simplified function is below 5% for a temperature of 0°C to 30°C. The benefit of this simpler function is that it can be inverted analytically, whereas the other function requires a numerical solution.

Connectors

TypeNameDefaultDescription
Modelica.Blocks.Interfaces.RealOutputp_wWater vapor partial pressure
Modelica.Blocks.Interfaces.RealInputTDew point temperature

Revisions

  • December 7, 2011 by Michael Wetter:
    Changed function call from p_w = Buildings.Utilities.Psychrometrics.Functions.pW_TDewPoi(T=T); to p_w = Buildings.Utilities.Psychrometrics.Functions.pW_TDewPoi_amb(T=T); as the first version sometimes triggered warnings when the solver attempts negative temperatures. The accuracy of the two implementation does not change much in the region of interest for building HVAC applications.
  • February 17, 2010 by Michael Wetter:
    Renamed block from DewPointTemperature_pWat to pW_TDewPoi.
  • September 4, 2008 by Michael Wetter:
    Changed from causal to acausal ports, needed, for example, for Buildings.Fluid.Examples.MixingVolumeMoistAir.
  • August 7, 2008 by Michael Wetter:
    First implementation.