This model calculates medium properties
for an ideal gas of a single substance, or for an ideal
gas consisting of several substances where the
mass fractions are fixed. Independent variables
are temperature T and pressure p.
Only density is a function of T and p. All other quantities
are solely a function of T. The properties
are valid in the range:
For the other variables, see the functions in
Modelica.Media.IdealGases.Common.SingleGasNasa.
Note, dynamic viscosity and thermal conductivity are only provided
for gases that use a data record from Modelica.Media.IdealGases.FluidData.
Currently these are the following gases:
This model has been copied from the ThermoFluid library
and adapted to the Modelica.Media package.
| Name | Description |
|---|
 ThermodynamicState
| Thermodynamic state variables for ideal gases |
| data | Data record of ideal gas substance |
| fluidConstants | Constant data for the fluid |
 BaseProperties
| Base properties of ideal gas medium |
 setState_pTX
| Return thermodynamic state as function of p, T and composition X |
 setState_phX
| Return thermodynamic state as function of p, h and composition X |
| setState_psX
| Return thermodynamic state as function of p, s and composition X |
| setState_dTX
| Return thermodynamic state as function of d, T and composition X |
| setSmoothState
| Return thermodynamic state so that it smoothly approximates: if x > 0 then state_a else state_b |
| pressure
| Return pressure of ideal gas |
| temperature
| Return temperature of ideal gas |
| density
| Return density of ideal gas |
| specificEnthalpy
| Return specific enthalpy |
| specificInternalEnergy
| Return specific internal energy |
| specificEntropy
| Return specific entropy |
| specificGibbsEnergy
| Return specific Gibbs energy |
| specificHelmholtzEnergy
| Return specific Helmholtz energy |
| specificHeatCapacityCp
| Return specific heat capacity at constant pressure |
| specificHeatCapacityCv
| Compute specific heat capacity at constant volume from temperature and gas data |
| isentropicExponent
| Return isentropic exponent |
| velocityOfSound
| Return velocity of sound |
| isentropicEnthalpyApproximation
| Approximate method of calculating h_is from upstream properties and downstream pressure |
| isentropicEnthalpy
| Return isentropic enthalpy |
| isobaricExpansionCoefficient
| Returns overall the isobaric expansion coefficient beta |
| isothermalCompressibility
| Returns overall the isothermal compressibility factor |
| density_derp_T
| Returns the partial derivative of density with respect to pressure at constant temperature |
| density_derT_p
| Returns the partial derivative of density with respect to temperature at constant pressure |
| density_derX
| Returns the partial derivative of density with respect to mass fractions at constant pressure and temperature |
| dynamicViscosity
| Dynamic viscosity |
| thermalConductivity
| Thermal conductivity of gas |
| molarMass
| Return the molar mass of the medium |
| T_h
| Compute temperature from specific enthalpy |
| T_ps
| Compute temperature from pressure and specific entropy |
| dynamicViscosityLowPressure
| Dynamic viscosity of low pressure gases |
| thermalConductivityEstimate
| Thermal conductivity of polyatomic gases(Eucken and Modified Eucken correlation) |
| Inherited |
|---|
 setState_pT
| Return thermodynamic state from p and T |
 setState_ph
| Return thermodynamic state from p and h |
| setState_ps
| Return thermodynamic state from p and s |
| setState_dT
| Return thermodynamic state from d and T |
| density_ph
| Return density from p and h |
| temperature_ph
| Return temperature from p and h |
| pressure_dT
| Return pressure from d and T |
| specificEnthalpy_dT
| Return specific enthalpy from d and T |
| specificEnthalpy_ps
| Return specific enthalpy from p and s |
| temperature_ps
| Return temperature from p and s |
| density_ps
| Return density from p and s |
| specificEnthalpy_pT
| Return specific enthalpy from p and T |
| density_pT
| Return density from p and T |
| ThermoStates | Enumeration type for independent variables |
| mediumName="unusablePartialMedium" | Name of the medium |
| substanceNames={mediumName} | Names of the mixture substances. Set substanceNames={mediumName} if only one substance. |
| extraPropertiesNames=fill("", 0) | Names of the additional (extra) transported properties. Set extraPropertiesNames=fill("",0) if unused |
| singleState | = true, if u and d are not a function of pressure |
| reducedX=true | = true if medium contains the equation sum(X) = 1.0; set reducedX=true if only one substance (see docu for details) |
| fixedX=false | = true if medium contains the equation X = reference_X |
| reference_p=101325 | Reference pressure of Medium: default 1 atmosphere |
| reference_T=298.15 | Reference temperature of Medium: default 25 deg Celsius |
| reference_X=fill(1/nX, nX) | Default mass fractions of medium |
| p_default=101325 | Default value for pressure of medium (for initialization) |
| T_default=Modelica.SIunits.Conversions.from_degC(20) | Default value for temperature of medium (for initialization) |
| h_default=specificEnthalpy_pTX(p_default, T_default, X_default) | Default value for specific enthalpy of medium (for initialization) |
| X_default=reference_X | Default value for mass fractions of medium (for initialization) |
| nS=size(substanceNames, 1) | Number of substances |
| nX=nS | Number of mass fractions |
| nXi=if fixedX then 0 else if reducedX then nS - 1 else nS | Number of structurally independent mass fractions (see docu for details) |
| nC=size(extraPropertiesNames, 1) | Number of extra (outside of standard mass-balance) transported properties |
| C_nominal=1.0e-6*ones(nC) | Default for the nominal values for the extra properties |
 FluidConstants
| Critical, triple, molecular and other standard data of fluid |
 prandtlNumber
| Return the Prandtl number |
 heatCapacity_cp
| Alias for deprecated name |
| heatCapacity_cv
| Alias for deprecated name |
| beta
| Alias for isobaricExpansionCoefficient for user convenience |
| kappa
| Alias of isothermalCompressibility for user convenience |
| density_derp_h
| Return density derivative w.r.t. pressure at const specific enthalpy |
| density_derh_p
| Return density derivative w.r.t. specific enthalpy at constant pressure |
| specificEnthalpy_pTX
| Return specific enthalpy from p, T, and X or Xi |
| specificEntropy_pTX
| Return specific enthalpy from p, T, and X or Xi |
| density_pTX
| Return density from p, T, and X or Xi |
| temperature_phX
| Return temperature from p, h, and X or Xi |
| density_phX
| Return density from p, h, and X or Xi |
| temperature_psX
| Return temperature from p,s, and X or Xi |
| density_psX
| Return density from p, s, and X or Xi |
| specificEnthalpy_psX
| Return specific enthalpy from p, s, and X or Xi |
| MassFlowRate
| Type for mass flow rate with medium specific attributes |
| AbsolutePressure
| Type for absolute pressure with medium specific attributes |
| Density
| Type for density with medium specific attributes |
| DynamicViscosity
| Type for dynamic viscosity with medium specific attributes |
| EnthalpyFlowRate
| Type for enthalpy flow rate with medium specific attributes |
| MassFraction
| Type for mass fraction with medium specific attributes |
| MoleFraction
| Type for mole fraction with medium specific attributes |
| MolarMass
| Type for molar mass with medium specific attributes |
| MolarVolume
| Type for molar volume with medium specific attributes |
| IsentropicExponent
| Type for isentropic exponent with medium specific attributes |
| SpecificEnergy
| Type for specific energy with medium specific attributes |
| SpecificInternalEnergy
| Type for specific internal energy with medium specific attributes |
| SpecificEnthalpy
| Type for specific enthalpy with medium specific attributes |
| SpecificEntropy
| Type for specific entropy with medium specific attributes |
| SpecificHeatCapacity
| Type for specific heat capacity with medium specific attributes |
| SurfaceTension
| Type for surface tension with medium specific attributes |
| Temperature
| Type for temperature with medium specific attributes |
| ThermalConductivity
| Type for thermal conductivity with medium specific attributes |
| PrandtlNumber
| Type for Prandtl number with medium specific attributes |
| VelocityOfSound
| Type for velocity of sound with medium specific attributes |
| ExtraProperty
| Type for unspecified, mass-specific property transported by flow |
| CumulativeExtraProperty
| Type for conserved integral of unspecified, mass specific property |
| ExtraPropertyFlowRate
| Type for flow rate of unspecified, mass-specific property |
| IsobaricExpansionCoefficient
| Type for isobaric expansion coefficient with medium specific attributes |
| DipoleMoment
| Type for dipole moment with medium specific attributes |
| DerDensityByPressure
| Type for partial derivative of density with respect to pressure with medium specific attributes |
| DerDensityByEnthalpy
| Type for partial derivative of density with respect to enthalpy with medium specific attributes |
| DerEnthalpyByPressure
| Type for partial derivative of enthalpy with respect to pressure with medium specific attributes |
| DerDensityByTemperature
| Type for partial derivative of density with respect to temperature with medium specific attributes |
| DerTemperatureByPressure
| Type for partial derivative of temperature with respect to pressure with medium specific attributes |
 SaturationProperties
| Saturation properties of two phase medium |
| FluidLimits
| Validity limits for fluid model |
| FixedPhase
| Phase of the fluid: 1 for 1-phase, 2 for two-phase, 0 for not known, e.g., interactive use |
 Basic
| The most basic version of a record used in several degrees of detail |
| IdealGas
| The ideal gas version of a record used in several degrees of detail |
| TwoPhase
| The two phase fluid version of a record used in several degrees of detail |
The used formula are based on the method of Chung et al (1984, 1988) referred to in ref [1] chapter 9.
The formula 9-4.10 is the one being used. The Formula is given in non-SI units, the following conversion constants were used to
transform the formula to SI units:
[1] Bruce E. Poling, John E. Prausnitz, John P. O'Connell, "The Properties of Gases and Liquids" 5th Ed. Mc Graw Hill.
T. Skoglund, Lund, Sweden, 2004-08-31
This function provides two similar methods for estimating the
thermal conductivity of polyatomic gases.
The Eucken method (input method == 1) gives good results for low temperatures,
but it tends to give an underestimated value of the thermal conductivity
(lambda) at higher temperatures.
The Modified Eucken method (input method == 2) gives good results for
high-temperatures, but it tends to give an overestimated value of the
thermal conductivity (lambda) at low temperatures.
Modelica.Media.IdealGases.Common.SingleGasNasa.ThermodynamicState
Modelica.Media.IdealGases.Common.SingleGasNasa.BaseProperties
Modelica.Media.IdealGases.Common.SingleGasNasa.setState_pTX