WOLFRAM SYSTEMMODELER

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.SIunits.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:

  1. Pressure p and specific enthalpy h are the most natural choice for general applications. This is the recommended choice for most general purpose applications.
  2. Pressure p and temperature T are the most natural choice for applications where air is always in the same phase (liquid or gas).
  3. 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