packagePerfectGas

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 c_p and constant volume c_v 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 Buildings.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.

Parameters

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
GasPropertiesprotected	Coefficient data record for properties of perfect gases
s_pTXprotected	Return specific entropy of moist air as a function of pressure p, temperature T and composition X (only valid for phi<1)
s_pTX_derprotected	Return specific entropy of moist air as a function of pressure p, temperature T and composition X (only valid for phi<1)

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.