BuildSysPro.IBPSA.Media.Specialized.Air.PerfectGas

# .BuildSysPro.IBPSA.Media.Specialized.Air.PerfectGas

Model for air as a perfect gas

## Information

This package contains a thermally perfect model of moist air.

A medium is called thermally perfect if

- it is in thermodynamic equilibrium,
- it is chemically not reacting, and
- internal energy and enthalpy are functions of temperature only.

In addition, this medium model is calorically perfect, i.e., the specific heat capacities at constant pressure cp and constant volume cv are both constant (Bower 1998).

This medium uses the ideal gas law

ρ = p ⁄(R T),

where ρ is the density, p is the pressure, R is the gas constant and T is the temperature.

The enthalpy is computed using the convention that h=0 if T=0 °C and no water vapor is present.

Note that for typical building simulations, the media IBPSA.Media.Air should be used as it leads generally to faster simulation.

#### References

Bower, William B. A primer in fluid mechanics: Dynamics of flows in one space dimension. CRC Press. 1998.

## Contents

Name | Description
--- | ---
ThermodynamicState | ThermodynamicState record for moist air
BaseProperties |
Xsaturation | Steam water mass fraction of saturation boundary in kg_water/kg_moistair
setState_pTX | Thermodynamic state as function of p, T and composition X
setState_phX | Thermodynamic state as function of p, h and composition X
setState_dTX | Thermodynamic state as function of d, T and composition X
gasConstant | Gas constant
saturationPressureLiquid | Return saturation pressure of water as a function of temperature T in the range of 273.16 to 373.16 K
saturationPressureLiquid_der | Time derivative of saturationPressureLiquid
sublimationPressureIce | Saturation curve valid for 223.16 <= T <= 273.16. Outside of these limits a (less accurate) result is returned
sublimationPressureIce_der | Derivative function for 'sublimationPressureIce'
saturationPressure | Saturation curve valid for 223.16 <= T <= 373.16 (and slightly outside with less accuracy)
pressure | Gas pressure
temperature | Gas temperature
density | Gas density
specificEntropy | Specific entropy (liquid part neglected, mixing entropy included)
enthalpyOfVaporization | Enthalpy of vaporization of water
HeatCapacityOfWater | Specific heat capacity of water (liquid only) which is constant
enthalpyOfLiquid | Enthalpy of liquid (per unit mass of liquid) which is linear in the temperature
der_enthalpyOfLiquid | Temperature derivative of enthalpy of liquid per unit mass of liquid
enthalpyOfCondensingGas | Enthalpy of steam per unit mass of steam
der_enthalpyOfCondensingGas | Derivative of enthalpy of steam per unit mass of steam
enthalpyOfNonCondensingGas | Enthalpy of non-condensing gas per unit mass of steam
der_enthalpyOfNonCondensingGas | Derivative of enthalpy of non-condensing gas per unit mass of steam
enthalpyOfGas | Enthalpy of gas mixture per unit mass of gas mixture
enthalpyOfDryAir | Enthalpy of dry air per unit mass of dry air
der_enthalpyOfDryAir | Derivative of enthalpy of dry air per unit mass of dry air
specificHeatCapacityCp | Specific heat capacity of gas mixture at constant pressure
der_specificHeatCapacityCp | Derivative of specific heat capacity of gas mixture at constant pressure
specificHeatCapacityCv | Specific heat capacity of gas mixture at constant volume
der_specificHeatCapacityCv | Derivative of specific heat capacity of gas mixture at constant volume
dynamicViscosity | dynamic viscosity of dry air
thermalConductivity | Thermal conductivity of dry air as a polynomial in the temperature
specificEnthalpy | Specific enthalpy
specificEnthalpy_pTX | Specific enthalpy
specificInternalEnergy | Specific internal energy
specificGibbsEnergy | Specific Gibbs energy
specificHelmholtzEnergy | Specific Helmholtz energy
temperature_phX | Compute temperature from specific enthalpy and mass fraction

## Revisions

- September 9, 2022, by Michael Wetter:
  Set nominal attribute for `BaseProperties.Xi`.
  This is for #1634.
- October 26, 2018, by Filip Jorissen and Michael Wetter:
  Now printing different messages if temperature is above or below its limit, and adding instance name as JModelica does not print the full instance name in the assertion. This is for #1045.
- March 15, 2016, by Michael Wetter:
  Replaced `spliceFunction` with `regStep`. This is for issue 300.
- November 13, 2014, by Michael Wetter:
  Removed `phi` and removed non-required computations.
- March 29, 2013, by Michael Wetter:
  Added `final standardOrderComponents=true` in the `BaseProperties` declaration. This avoids an error when models are checked in Dymola 2014 in the pedenatic mode.
- April 12, 2012, by Michael Wetter:
  Added keyword `each` to `Xi(stateSelect=...)`.
- April 4, 2012, by Michael Wetter:
  Added redeclaration of `ThermodynamicState` to avoid a warning during model check and translation.
- January 27, 2010, by Michael Wetter:
  Added function `enthalpyOfNonCondensingGas` and its derivative.
- January 27, 2010, by Michael Wetter:
  Fixed bug with temperature offset in `T_phX`.
- August 18, 2008, by Michael Wetter:
  First implementation.

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