Model BaseProperties is a model within package PartialMedium and contains the declarations of the minimum number of variables that every medium model is supposed to support. A specific medium inherits from model BaseProperties and provides the equations for the basic properties.
The BaseProperties model contains the following 7+nXi variables (nXi is the number of independent mass fractions defined in package PartialMedium):
| Variable | Unit | Description |
| T | K | Temperature |
| p | Pa | Absolute pressure |
| d | kg/m3 | Density |
| h | J/kg | Specific enthalpy |
| u | J/kg | Specific internal energy |
| Xi[nXi] | kg/kg | Structurally independent mass fractions |
| R_s | J/(kg.K) | Specific gas constant (of mixture if applicable) |
| MM | kg/mol | Molar mass |
In order to implement an actual medium model, one can extend from this base model and add 5 equations that provide relations among these variables. Equations will also have to be added in order to set all the variables within the ThermodynamicState record state.
If standardOrderComponents=true, the full composition vector X[nX] is determined by the equations contained in this base class, depending on the independent mass fraction vector Xi[nXi].
Additional 2 + nXi equations will have to be provided when using the BaseProperties model, in order to fully specify the thermodynamic conditions. The input connector qualifier applied to p, h, and nXi indirectly declares the number of missing equations, permitting advanced equation balance checking by Modelica tools. Please note that this doesn't mean that the additional equations should be connection equations, nor that exactly those variables should be supplied, in order to complete the model. For further information, see the Modelica.Media User's guide, and Section 4.7 (Balanced Models) of the Modelica 3.4 specification.
| Name | Description |
|---|---|
| InputAbsolutePressure | Pressure as input signal connector |
| InputSpecificEnthalpy | Specific enthalpy as input signal connector |
| InputMassFraction | Mass fraction as input signal connector |