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WOLFRAM SYSTEM MODELER

Air_Base

Properties of dry air calculated using the equation of state by Lemmon et. al.

Package Contents

	ThermodynamicState Thermodynamic state
	BaseProperties Base properties of air
	density_ph Computes density as a function of pressure and specific enthalpy
	temperature_ph Computes temperature as a function of pressure and specific enthalpy
	temperature_ps Compute temperature from pressure and specific enthalpy
	density_ps Computes density as a function of pressure and specific enthalpy
	pressure_dT Computes pressure as a function of density and temperature
	specificEnthalpy_dT Computes specific enthalpy as a function of density and temperature
	specificEnthalpy_pT Computes specific enthalpy as a function of pressure and temperature
	specificEnthalpy_ps Computes specific enthalpy as a function of pressure and temperature
	density_pT Computes density as a function of pressure and temperature
	dynamicViscosity Return dynamic viscosity as a function of the thermodynamic state record
	thermalConductivity Thermal conductivity of air
	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
	specificGibbsEnergy Return specific Gibbs energy
	specificHelmholtzEnergy Return specific Helmholtz energy
	specificEntropy Specific entropy of air
	specificHeatCapacityCp Specific heat capacity at constant pressure of air
	specificHeatCapacityCv Specific heat capacity at constant volume of air
	isentropicExponent Return isentropic exponent
	isothermalCompressibility Isothermal compressibility of air
	isobaricExpansionCoefficient Isobaric expansion coefficient of air
	velocityOfSound Return velocity of sound as a function of the thermodynamic state record
	density_derh_p Density derivative by specific enthalpy
	density_derp_h Density derivative by pressure
	setState_dTX Return thermodynamic state of air as function of d and T
	setState_phX Return thermodynamic state of air as function of p and h
	setState_psX Return thermodynamic state of air as function of p and s
	setState_pTX Return thermodynamic state of air as function of p and T
	setSmoothState Return thermodynamic state so that it smoothly approximates: if x > 0 then state_a else state_b
	isentropicEnthalpy
	molarMass Return the molar mass of the medium

Package Constants (23)

ThermoStates	Value: Type: IndependentVariables Description: Enumeration type for independent variables
mediumName	Value: "Air" Type: String Description: Name of the medium
substanceNames	Value: {"air"} Type: String[:] Description: Names of the mixture substances. Set substanceNames={mediumName} if only one substance.
extraPropertiesNames	Value: fill("", 0) Type: String[:] Description: Names of the additional (extra) transported properties. Set extraPropertiesNames=fill("",0) if unused
singleState	Value: false Type: Boolean Description: = true, if u and d are not a function of pressure
reducedX	Value: true Type: Boolean Description: = true if medium contains the equation sum(X) = 1.0; set reducedX=true if only one substance (see docu for details)
fixedX	Value: true Type: Boolean Description: = true if medium contains the equation X = reference_X
reference_p	Value: 101325 Type: AbsolutePressure (Pa) Description: Reference pressure of Medium: default 1 atmosphere
reference_T	Value: 298.15 Type: Temperature (K) Description: Reference temperature of Medium: default 25 deg Celsius
reference_X	Value: fill(1 / nX, nX) Type: MassFraction[nX] (kg/kg) Description: Default mass fractions of medium
p_default	Value: 101325 Type: AbsolutePressure (Pa) Description: Default value for pressure of medium (for initialization)
T_default	Value: Modelica.Units.Conversions.from_degC(20) Type: Temperature (K) Description: Default value for temperature of medium (for initialization)
h_default	Value: specificEnthalpy_pTX(p_default, T_default, X_default) Type: SpecificEnthalpy (J/kg) Description: Default value for specific enthalpy of medium (for initialization)
X_default	Value: reference_X Type: MassFraction[nX] (kg/kg) Description: Default value for mass fractions of medium (for initialization)
C_default	Value: fill(0, nC) Type: ExtraProperty[nC] Description: Default value for trace substances of medium (for initialization)
nS	Value: size(substanceNames, 1) Type: Integer Description: Number of substances
nX	Value: nS Type: Integer Description: Number of mass fractions
nXi	Value: if fixedX then 0 else if reducedX then nS - 1 else nS Type: Integer Description: Number of structurally independent mass fractions (see docu for details)
nC	Value: size(extraPropertiesNames, 1) Type: Integer Description: Number of extra (outside of standard mass-balance) transported properties
C_nominal	Value: 1.0e-6 * ones(nC) Type: Real[nC] Description: Default for the nominal values for the extra properties
ph_explicit	Value: Type: Boolean Description: True if explicit in pressure and specific enthalpy
dT_explicit	Value: Type: Boolean Description: True if explicit in density and temperature
pT_explicit	Value: Type: Boolean Description: True if explicit in pressure and temperature

Information

This information is part of the Modelica Standard Library maintained by the Modelica Association.

This model calculates medium properties for air in the liquid, gas and two phase regions. Three variable pairs can be the independent variables of the model:

Pressure p and specific enthalpy h are the most natural choice for general applications. This is the recommended choice for most general purpose applications.
Pressure p and temperature T are the most natural choice for applications where air is always in the same phase (liquid or gas).
Density d and temperature T are explicit variables of the Helmholtz function in the near-critical region and can be the best choice for applications with super-critical or near-critical states.

The following quantities are always computed:

Variable	Unit	Description
T	K	temperature
u	J/kg	specific internal energy
d	kg/m^3	density
p	Pa	pressure
h	J/kg	specific enthalpy

In some cases additional medium properties are needed. A component that needs these optional properties has to call one of the functions listed in Modelica.Media.UsersGuide.MediumUsage.OptionalProperties and in Modelica.Media.UsersGuide.MediumUsage.TwoPhase.

Many further properties can be computed. Using the well-known Bridgman's Tables, all first partial derivatives of the standard thermodynamic variables can be computed easily.

Wolfram Language

In[1]:=

SystemModel["Modelica.Media.Air.ReferenceAir.Air_Base"]

Out[1]:=

Extended by (3)

Air_dT

Modelica.Media.Air.ReferenceAir

ReferenceAir.Air_dT: Detailed dry air model (130 ... 2000 K) explicit in d and T

Air_pT

Modelica.Media.Air.ReferenceAir

ReferenceAir.Air_pT: Detailed dry air model (130 ... 2000 K) explicit in p and T

Air_ph

Modelica.Media.Air.ReferenceAir

ReferenceAir.Air_ph: Detailed dry air model (130 ... 2000 K) explicit in p and h