WOLFRAM SYSTEMMODELER

Constants

Constants

Wolfram Language

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SystemModel["Modelica.Media.UsersGuide.MediumUsage.Constants"]
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Information

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

Every medium model provides the following constants. For example, if a medium is declared as:

   replaceable package Medium = Modelica.Media.Interfaces.PartialMedium;

then constants "Medium.mediumName", "Medium.nX", etc. are defined:

Type Name Description
StringmediumName Unique name of the medium (is usually used to check whether the media in different components connected together are the same, by providing Medium.mediumName as quantity attribute of the mass flow rate in the connector)
StringsubstanceNames[nS] Names of the substances that make up the medium. If only one substance is present, substanceNames = {mediumName}.
StringextraPropertiesNames[nC] Names of the extra transported substances, outside of mass and energy balances.
BooleansingleState = true, if u and d are not a function of pressure, and thus only a function of a single thermal variable (temperature or enthalpy) and of Xi for a multiple substance medium. Usually, this flag is true for incompressible media. It is used in a model to determine whether 1+nXi (singleState=true) or 2+nXi (singleState=false) initial conditions have to be provided for a volume element that contains mass and energy balance.
AbsolutePressurereference_p Reference pressure for the medium
MassFractionreference_X[nX] Reference composition for the medium
AbsolutePressurep_default Default value for pressure of medium (for initialization)
TemperatureT_default Default value for temperature of medium (for initialization)
SpecificEnthalpyh_default Default value for specific enthalpy of medium (for initialization)
MassFractionX_default[nX] Default value for mass fractions of medium (for initialization)
IntegernS number of substances contained in the medium.
IntegernX Size of the full mass fraction vector X nX=nS.
IntegernXi Number of independent mass fractions. If there is a single substance, then nXi = 0.
BooleanreducedX = true, if the medium has a single substance, or if the medium model has multiple substances and contains the equation sum(X) = 1. In both cases, nXi = nS - 1 (unless fixedX = true).
= false, if the medium has multiple substances and does not contain the equation sum(X)=1, i.e., nXi = nX = nS (unless fixedX = true).
BooleanfixedX = false: the composition of the medium can vary, and is determined by nXi independent mass fractions (see reducedX above).
= true: the composition of the medium is always reference_X, and nXi = 0.
FluidConstantsfluidConstants[nS] Critical, triple, molecular and other standard data that are provided for every substance of a medium.

The record FluidConstants that is defined in PartialMedium contains the following elements

Type Name Description
String iupacName complete IUPAC name
String casRegistryNumber chemical abstracts sequencing number
String chemicalFormula Chemical formula, (brutto, nomenclature according to Hill)
String structureFormula Chemical structure formula
MolarMass molarMass molar mass

This record is extended in the partial packages further down the hierarchy (such as PartialTwoPhaseMedium or PartialMixtureMedium) and may contain some or all of the following elements

Temperature criticalTemperature critical temperature
AbsolutePressure criticalPressure critical pressure
MolarVolume criticalMolarVolume critical molar Volume
Real acentricFactor Pitzer acentric factor
Temperature triplePointTemperature triple point temperature
AbsolutePressure triplePointPressure triple point pressure
Temperature meltingPoint melting point at 101325 Pa
Temperature normalBoilingPoint normal boiling point (at 101325 Pa)
DipoleMoment dipoleMoment dipole moment of molecule in Debye (1 debye = 3.33564e10-30 C.m)
Boolean hasIdealGasHeatCapacity true if ideal gas heat capacity is available
Boolean hasCriticalData true if critical data are known
Boolean hasDipoleMoment true if a dipole moment known
Boolean hasFundamentalEquation true if a fundamental equation
Boolean hasLiquidHeatCapacity true if liquid heat capacity is available
Boolean hasSolidHeatCapacity true if solid heat capacity is available
Boolean hasAccurateViscosityData true if accurate data for a viscosity function is available
Boolean hasAccurateConductivityData true if accurate data for thermal conductivity is available
Boolean hasVapourPressureCurve true if vapour pressure data, e.g., Antoine coefficients are known
Boolean hasAcentricFactor true if Pitzer acentric factor is known
SpecificEnthalpy HCRIT0 Critical specific enthalpy of the fundamental equation
SpecificEntropy SCRIT0 Critical specific entropy of the fundamental equation
SpecificEnthalpy deltah Difference between specific enthalpy model (h_m) and f.eq. (h_f) (h_m - h_f)
SpecificEntropy deltas Difference between specific enthalpy model (s_m) and f.eq. (s_f) (s_m - s_f)