This information is part of the Modelica Standard Library maintained by the Modelica Association.
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
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 (the Modelica_Fluid library is currently
under development to provide 1D therm-fluid flow components for
single and multiple substance flow with one and multiple phases).
The Modelica.Media library has the following
- Balance equations and media model equations
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.
summarizes the changes of the library releases.
provides information about the authors of the library as well as