.Modelica.Media.UsersGuide.MediumUsage.Constants .Modelica.Media.UsersGuide.MediumUsage.ConstantsEvery 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 |
| String | mediumName | 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) |
| String | substanceNames[nS] | Names of the substances that make up the medium. If only one substance is present, substanceNames = {mediumName}. |
| String | extraPropertiesNames[nC] | Names of the extra transported substances, outside of mass and energy balances. |
| Boolean | singleState | = 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. |
| AbsolutePressure | reference_p | Reference pressure for the medium |
| MassFraction | reference_X[nX] | Reference composition for the medium |
| AbsolutePressure | p_default | Default value for pressure of medium (for initialization) |
| Temperature | T_default | Default value for temperature of medium (for initialization) |
| SpecificEnthalpy | h_default | Default value for specific enthalpy of medium (for initialization) |
| MassFraction | X_default[nX] | Default value for mass fractions of medium (for initialization) |
| Integer | nS | number of substances contained in the medium. |
| Integer | nX | Size of the full mass fraction vector X nX=nS. |
| Integer | nXi | Number of independent mass fractions. If there is a single substance, then nXi = 0. |
| Boolean | reducedX | = 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). |
| Boolean | fixedX | = 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. |
| FluidConstants | fluidConstants[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) |