Library Modelica.Media is a
free Modelica package providing a standardized
interface to fluid media models and specific media models based on
this interface. A fluid medium model defines
algebraic equations for the intensive
thermodynamic variables used in the mass and
energy balance of component models. Optionally,
additional medium properties can be computed such as dynamic
viscosity or thermal conductivity. Medium models are defined for
single and multiple substance
fluids with one and multiple
phases.
A large part of the library provides specific medium models that
can be directly utilized. This library can be used in all types of
Modelica fluid libraries that may have different connectors and
design philosophies. It is particularly utilized in the
Modelica.Fluid library (1D therm-fluid flow components for single
and multiple substance flow with one and multiple phases). The
Modelica.Media library has the following main features:
- Balance equations and media model equations are decoupled. This
means that the used medium model does usually not have an influence
on how the balance equations are formulated. For example, the same
balance equations are used for media that use pressure and
temperature, or pressure and specific enthalpy as independent
variables, as well as for incompressible and compressible media
models. A Modelica tool will have enough information to generate as
efficient code as a traditional (coupled) definition. This feature
is described in more detail in section
Static State Selection.
- Optional variables, such as dynamic viscosity, are only
computed if needed in the corresponding component.
- The independent variables of a medium model do not influence
the definition of a fluid connector port. Especially, the media
models are implemented in such a way that a connector may have the
minimum number of independent medium variables in a connector and
still get the same efficiency as if all medium variables are passed
by the connector from one component to the next one (the latter
approach has the restriction that a fluid port can only connect two
components and not more). Note, the Modelica.Fluid library uses the
first approach, i.e., having a set of independent medium variables
in a connector.
- The medium models are implemented with regards to efficient
dynamic simulation. For example, two phase medium models trigger
state events at phase boundaries (because the medium variables are
not differentiable at this point).
This User's Guide has the following main parts:
- Medium usage
describes how to use a medium model from this library in a
component model.
- Medium
definition describes how a new fluid medium model has to be
implemented.
- ReleaseNotes
summarizes the changes of the library releases.
- Contact provides
information about the authors of the library as well as
acknowledgements.
Contents
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