Modelica.Fluid.Types

Common types for fluid models

Information

Extends from Modelica.Icons.TypesPackage (Icon for packages containing type definitions).

Package Content

Name	Description
HydraulicConductance	Real type for hydraulic conductance
HydraulicResistance	Real type for hydraulic resistance
Roughness	Real type for roughness of a pipe
Dynamics	Enumeration to define definition of balance equations
CvTypes	Enumeration to define the choice of valve flow coefficient
PortFlowDirection	Enumeration to define whether flow reversal is allowed
ModelStructure	Enumeration with choices for model structure in distributed pipe model

Modelica.Fluid.Types.HydraulicConductance

Real type for hydraulic conductance

Parameters

Modelica.Fluid.Types.HydraulicResistance

Real type for hydraulic resistance

Parameters

Modelica.Fluid.Types.Roughness

Real type for roughness of a pipe

Information

This Real type defines the absolute roughness of the inner surface of a pipe or fitting, i.e., the absolute average height of surface asperities. It has usually to be estimated. In [Idelchik 1994, pp. 105-109, Table 2-5; Miller 1990, p. 190, Table 8-1] many examples are given. As a short summary:

References

Idelchik I.E. (1994):

Handbook of Hydraulic Resistance. 3rd edition, Begell House, ISBN 0-8493-9908-4

Miller D. S. (1990):

Internal flow systems. 2nd edition. Cranfield:BHRA(Information Services).

Extends from Modelica.Icons.TypeReal (Icon for Real types).

Parameters

Modelica.Fluid.Types.Dynamics

Enumeration to define definition of balance equations

Information

Enumeration to define the formulation of balance equations (to be selected via choices menu):

The enumeration "Dynamics" is used for the mass, energy and momentum balance equations respectively. The exact meaning for the three balance equations is stated in the following tables:

In the tables above, the equations are given for one-substance fluids. For multiple-substance fluids and for trace substances, equivalent equations hold.

Medium.singleState is a medium property and defines whether the medium is only described by one state (+ the mass fractions in case of a multi-substance fluid). In such a case one initial condition less must be provided. For example, incompressible media have Medium.singleState = true.

Modelica.Fluid.Types.CvTypes

Enumeration to define the choice of valve flow coefficient

Information

Enumeration to define the choice of valve flow coefficient (to be selected via choices menu):

The details of the coefficients are explained in the User's Guide .

Modelica.Fluid.Types.PortFlowDirection

Enumeration to define whether flow reversal is allowed

Information

Enumeration to define the assumptions on the model for the direction of fluid flow at a port (to be selected via choices menu):

The default is "PortFlowDirection.Bidirectional". If you are completely sure that the flow is only in one direction, then the other settings may make the simulation of your model faster.

Modelica.Fluid.Types.ModelStructure

Enumeration with choices for model structure in distributed pipe model

Information

Enumeration to define the discretization structure of distributed pipe models according to the staggered grid scheme:

The default is "ModelStructure.av_vb", i.e., the distributed pipe has "volumes" at its both ends. The advantage is that connections of the pipe to flow models (like fittings) lead to the desirable structure of alternating volume and flow models, which means that no non-linear algebraic equations occur.

Direct connections of distributed pipes with this option means that two volumes are directly connected together. Due to the stream concept this means that the pressures of the two connected volumes are identical, but the temperatures are not set equal (this corresponds to volumes that are connected together with a very short distance and it needs some time until different volume temperatures are equilibrated). Since the pressures of the volumes are identical, the number of states is reduced and index reduction takes place (which means that medium equations depending on pressure are differentiated and the number of required initial conditions is reduced by one).

The default option "av_vb" cannot be used, if the dynamic pipe is connected to a model with non-differentiable pressure, like a Sources.Boundary_pT with prescribed jumping pressure. The modelStructure can be configured as appropriate in such situations, in order to place a momentum balance between a pressure state of the pipe and a non-differentiable boundary condition (e.g., if the jumping pressure component is connected to port_a, use model structure ModelStructure.a_vb).