packagePerfectGas
Model for air as a perfect gas
Extends from Modelica.Media.Interfaces.PartialCondensingGases, Modelica.Icons.Package.
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 BuildingSystems.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
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | Water | 1 | Index of water (in substanceNames, massFractions X, etc.) |
| Integer | Air | 2 | Index of air (in substanceNames, massFractions X, etc.) |
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 forBaseProperties.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:
ReplacedspliceFunctionwithregStep. This is for issue 300. -
November 13, 2014, by Michael Wetter:
Removedphiand removed non-required computations. -
March 29, 2013, by Michael Wetter:
Addedfinal standardOrderComponents=truein theBasePropertiesdeclaration. This avoids an error when models are checked in Dymola 2014 in the pedenatic mode. -
April 12, 2012, by Michael Wetter:
Added keywordeachtoXi(stateSelect=...). -
April 4, 2012, by Michael Wetter:
Added redeclaration ofThermodynamicStateto avoid a warning during model check and translation. -
January 27, 2010, by Michael Wetter:
Added functionenthalpyOfNonCondensingGasand its derivative. -
January 27, 2010, by Michael Wetter:
Fixed bug with temperature offset inT_phX. -
August 18, 2008, by Michael Wetter:
First implementation.