Modelica.Fluid

Information

Library Modelica.Fluid is a free Modelica package providing components for 1-dimensional thermo-fluid flow in networks of vessels, pipes, fluid machines, valves and fittings. A unique feature is that the component equations and the media models as well as pressure loss and heat transfer correlations are decoupled from each other. All components are implemented such that they can be used for media from the Modelica.Media library. This means especially that an incompressible or compressible medium, a single or a multiple substance medium with one or more phases might be used.

In the next figure, several features of the library are demonstrated with a simple heating system with a closed flow cycle. By just changing one configuration parameter in the system object the equations are changed between steady-state and dynamic simulation with fixed or steady-state initial conditions.

With respect to previous versions, the design of the connectors has been changed in a non-backward compatible way, using the recently developed concept of stream connectors that results in much more reliable simulations (see also Stream-Connectors-Overview-Rationale.pdf). This extension was included in Modelica 3.1. As of Jan. 2009, the stream concept is supported in Dymola 7.1. It is recommended to use Dymola 7.2 (available since Feb. 2009), or a later Dymola version, since this version supports a new annotation to connect very conveniently to vectors of connectors. Other tool vendors will support the stream concept as well.

The following parts are useful, when newly starting with this library:

• Modelica.Fluid.UsersGuide.
• Modelica.Fluid.UsersGuide.ReleaseNotes summarizes the changes of the library releases.
• Modelica.Fluid.Examples contains examples that demonstrate the usage of this library.

Licensed by the Modelica Association under the Modelica License 2
Copyright © 2002-2010, ABB, DLR, Dassault Systèmes AB, Modelon, TU Braunschweig, TU Hamburg-Harburg, Politecnico di Milano.

This Modelica package is free software and the use is completely at your own risk; it can be redistributed and/or modified under the terms of the Modelica License 2. For license conditions (including the disclaimer of warranty) see Modelica.UsersGuide.ModelicaLicense2 or visit http://www.modelica.org/licenses/ModelicaLicense2.

Extends from Modelica.Icons.Package (Icon for standard packages).

Package Content

Name	Description
UsersGuide	User's Guide
Examples	Demonstration of the usage of the library
System	System properties and default values (ambient, flow direction, initialization)
Vessels	Devices for storing fluid
Pipes	Devices for conveying fluid
Machines	Devices for converting between energy held in a fluid and mechanical energy
Valves	Components for the regulation and control of fluid flow
Fittings	Adaptors for connections of fluid components and the regulation of fluid flow
Sources	Define fixed or prescribed boundary conditions
Sensors	Ideal sensor components to extract signals from a fluid connector
Interfaces	Interfaces for steady state and unsteady, mixed-phase, multi-substance, incompressible and compressible flow
Types	Common types for fluid models
Dissipation	Functions for convective heat transfer and pressure loss characteristics
Utilities	Utility models to construct fluid components (should not be used directly)
Icons

Modelica.Fluid.System

Information

A system component is needed in each fluid model to provide system-wide settings, such as ambient conditions and overall modeling assumptions. The system settings are propagated to the fluid models using the inner/outer mechanism.

A model should never directly use system parameters. Instead a local parameter should be declared, which uses the global setting as default. The only exception currently made is the gravity system.g.

Parameters

Type	Name	Default	Description
Environment
AbsolutePressure	p_ambient	101325	Default ambient pressure [Pa]
Temperature	T_ambient	293.15	Default ambient temperature [K]
Acceleration	g	Modelica.Constants.g_n	Constant gravity acceleration [m/s2]
Assumptions
Boolean	allowFlowReversal	true	= false to restrict to design flow direction (port_a -> port_b)
Dynamics
Dynamics	energyDynamics	Modelica.Fluid.Types.Dynamic...	Default formulation of energy balances
Dynamics	massDynamics	energyDynamics	Default formulation of mass balances
Dynamics	momentumDynamics	Modelica.Fluid.Types.Dynamic...	Default formulation of momentum balances, if options available
Initialization
MassFlowRate	m_flow_start	0	Default start value for mass flow rates [kg/s]
AbsolutePressure	p_start	p_ambient	Default start value for pressures [Pa]
Temperature	T_start	T_ambient	Default start value for temperatures [K]
Advanced
MassFlowRate	m_flow_small	0.01	Default small laminar mass flow rate for regularization of zero flow [kg/s]
AbsolutePressure	dp_small	1	Default small pressure drop for regularization of laminar and zero flow [Pa]

Modelica definition

model System 
  "System properties and default values (ambient, flow direction, initialization)"

  package Medium = Modelica.Media.Interfaces.PartialMedium 
    "Medium model for default start values";
  parameter Modelica.SIunits.AbsolutePressure p_ambient=101325 
    "Default ambient pressure";
  parameter Modelica.SIunits.Temperature T_ambient=293.15 
    "Default ambient temperature";
  parameter Modelica.SIunits.Acceleration g=Modelica.Constants.g_n 
    "Constant gravity acceleration";

  // Assumptions
  parameter Boolean allowFlowReversal = true 
    "= false to restrict to design flow direction (port_a -> port_b)";
  parameter Modelica.Fluid.Types.Dynamics energyDynamics=
    Modelica.Fluid.Types.Dynamics.DynamicFreeInitial 
    "Default formulation of energy balances";
  parameter Modelica.Fluid.Types.Dynamics massDynamics=
    energyDynamics "Default formulation of mass balances";
  final parameter Modelica.Fluid.Types.Dynamics substanceDynamics=
    massDynamics "Default formulation of substance balances";
  final parameter Modelica.Fluid.Types.Dynamics traceDynamics=
    massDynamics "Default formulation of trace substance balances";
  parameter Modelica.Fluid.Types.Dynamics momentumDynamics=
    Modelica.Fluid.Types.Dynamics.SteadyState 
    "Default formulation of momentum balances, if options available";

  // Initialization
  parameter Modelica.SIunits.MassFlowRate m_flow_start = 0 
    "Default start value for mass flow rates";
  parameter Modelica.SIunits.AbsolutePressure p_start = p_ambient 
    "Default start value for pressures";
  parameter Modelica.SIunits.Temperature T_start = T_ambient 
    "Default start value for temperatures";

  // Advanced
  parameter Modelica.SIunits.MassFlowRate m_flow_small(min=0) = 0.01 
    "Default small laminar mass flow rate for regularization of zero flow";
  parameter Modelica.SIunits.AbsolutePressure dp_small(min=0) = 1 
    "Default small pressure drop for regularization of laminar and zero flow";


end System;