Modelica.Fluid.Types

Common types for fluid models

Information





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

Package Content




NameDescription


Modelica.Fluid.Types.HydraulicConductance HydraulicConductance
Real type for hydraulic conductance


Modelica.Fluid.Types.HydraulicResistance HydraulicResistance
Real type for hydraulic resistance


Modelica.Fluid.Types.Roughness 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
Modelica.Fluid.Types.HydraulicConductance

Real type for hydraulic conductance


Parameters




NameDescription


quantity 


unit 






Modelica.Fluid.Types.HydraulicResistance
Modelica.Fluid.Types.HydraulicResistance

Real type for hydraulic resistance


Parameters




NameDescription


quantity 


unit 






Modelica.Fluid.Types.Roughness
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:





  
Type of pipe
      Roughness


  
Smooth pipes
      Drawn brass, copper, aluminium, glass, etc.
       0.0025 mm
  

  
Steel pipes
      New smooth pipes
      0.025 mm
  

  
Mortar lined, average finish
      0.1 mm
  

  
Heavy rust
      1 mm
  

  
Concrete pipes
      Steel forms, first class workmanship
      0.025 mm
  

  
Steel forms, average workmanship
      0.1 mm
  

  
Block linings
      1 mm
  





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




NameDescription


quantity 


unit 


displayUnit 






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):






Dynamics.Meaning


DynamicFreeInitialDynamic balance, Initial guess value



FixedInitialDynamic balance, Initial value fixed



SteadyStateInitialDynamic balance, Steady state initial with guess value



SteadyStateSteady state balance, Initial guess value






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:






Mass balance 

Dynamics.
    Balance equation
    Initial condition



 DynamicFreeInitial
     no restrictions 
     no initial conditions 



 FixedInitial
     no restrictions 
     if Medium.singleState then 

           no initial condition

         else p=p_start 



 SteadyStateInitial
     no restrictions 
     if Medium.singleState then 

           no initial condition

         else der(p)=0 



 SteadyState
     der(m)=0  
     no initial conditions 




 





Energy balance 

Dynamics.
    Balance equation
    Initial condition



 DynamicFreeInitial
     no restrictions 
     no initial conditions 



 FixedInitial
     no restrictions 
     T=T_start or h=h_start 



 SteadyStateInitial
     no restrictions 
     der(T)=0 or der(h)=0 



 SteadyState
     der(U)=0  
     no initial conditions 




 





Momentum balance 

Dynamics.
    Balance equation
    Initial condition



 DynamicFreeInitial
     no restrictions 
     no initial conditions 



 FixedInitial
     no restrictions 
     m_flow = m_flow_start 



 SteadyStateInitial
     no restrictions 
     der(m_flow)=0 



 SteadyState
     der(m_flow)=0 
     no initial conditions 






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):






CvTypes.
    Meaning



Av
    Av (metric) flow coefficient



Kv
    Kv (metric) flow coefficient



Cv
    Cv (US) flow coefficient



OpPoint
    Av defined by operating point







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):






PortFlowDirection.
    Meaning



Entering
    Fluid flow is only entering the port from the outside



Leaving
    Fluid flow is only leaving the port to the outside



Bidirectional
    No restrictions on fluid flow (flow reversal possible)






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:






ModelStructure.
    Meaning



av_vb
    port_a - volume - flow model - volume - port_b



a_v_b
    port_a - flow model - volume - flow model - port_b



av_b
    port_a - volume - flow model - port_b



a_vb
    port_a - flow model - volume - port_b






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).







Automatically generated Mon Sep 23 17:20:49 2013.