WOLFRAM SYSTEM MODELER
SystemSystem properties and default values (ambient, flow direction, initialization) |
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Wolfram Language
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SystemModel["Modelica.Fluid.System"]
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Information
This information is part of the Modelica Standard Library maintained by the Modelica Association.
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 exceptions are:
- the gravity system.g,
- the global system.eps_m_flow, which is used to define a local m_flow_small for the local m_flow_nominal:
m_flow_small = system.eps_m_flow*m_flow_nominal
The global system.m_flow_small and system.dp_small are classic parameters. They do not distinguish between laminar flow and regularization of zero flow. Absolute small values are error prone for models with local nominal values. Moreover dp_small can generally be obtained automatically. Consider using the new system.use_eps_Re = true (see Advanced tab).
Parameters (17)
| p_ambient |
Value: 101325 Type: AbsolutePressure (Pa) Description: Default ambient pressure |
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| T_ambient |
Value: 293.15 Type: Temperature (K) Description: Default ambient temperature |
| g |
Value: Modelica.Constants.g_n Type: Acceleration (m/s²) Description: Constant gravity acceleration |
| allowFlowReversal |
Value: true Type: Boolean Description: = false to restrict to design flow direction (port_a -> port_b) |
| energyDynamics |
Value: Modelica.Fluid.Types.Dynamics.DynamicFreeInitial Type: Dynamics Description: Default formulation of energy balances |
| massDynamics |
Value: energyDynamics Type: Dynamics Description: Default formulation of mass balances |
| substanceDynamics |
Value: massDynamics Type: Dynamics Description: Default formulation of substance balances |
| traceDynamics |
Value: massDynamics Type: Dynamics Description: Default formulation of trace substance balances |
| momentumDynamics |
Value: Modelica.Fluid.Types.Dynamics.SteadyState Type: Dynamics Description: Default formulation of momentum balances, if options available |
| m_flow_start |
Value: 0 Type: MassFlowRate (kg/s) Description: Default start value for mass flow rates |
| p_start |
Value: p_ambient Type: AbsolutePressure (Pa) Description: Default start value for pressures |
| T_start |
Value: T_ambient Type: Temperature (K) Description: Default start value for temperatures |
| use_eps_Re |
Value: false Type: Boolean Description: = true to determine turbulent region automatically using Reynolds number |
| m_flow_nominal |
Value: if use_eps_Re then 1 else 1e2 * m_flow_small Type: MassFlowRate (kg/s) Description: Default nominal mass flow rate |
| eps_m_flow |
Value: 1e-4 Type: Real Description: Regularization of zero flow for |m_flow| < eps_m_flow*m_flow_nominal |
| dp_small |
Value: 1 Type: AbsolutePressure (Pa) Description: Default small pressure drop for regularization of laminar and zero flow |
| m_flow_small |
Value: 1e-2 Type: MassFlowRate (kg/s) Description: Default small mass flow rate for regularization of laminar and zero flow |
Used in Examples (20)
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Modelica.Fluid.Examples Simple model of a heating system |
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Modelica.Fluid.Examples.DrumBoiler Complete drum boiler model, including evaporator and supplementary components |
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Modelica.Fluid.Examples.Tanks Demonstrating the usage of SimpleTank |
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Modelica.Fluid.Examples.Tanks Two tanks connected with pipes at different heights |
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Modelica.Fluid.Examples.Tanks Show the treatment of empty tanks |
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Modelica.Fluid.Examples.ControlledTankSystem Demonstrating the controller of a tank filling/emptying system |
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Modelica.Fluid.Examples.AST_BatchPlant Model of an experimental batch plant |
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Modelica.Fluid.Examples.AST_BatchPlant.Test Tank with one time-varying top inlet mass flow rate and a bottom outlet into the ambient |
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Modelica.Fluid.Examples.AST_BatchPlant.Test |
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Modelica.Fluid.Examples.AST_BatchPlant.Test Demonstrates a tank with one constant top inlet mass flow rate and a bottom outlet into the ambient |
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Modelica.Fluid.Examples.AST_BatchPlant.Test Demonstrates a tank with one constant top inlet mass flow rate and a bottom outlet into the ambient |
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Modelica.Fluid.Examples.AST_BatchPlant.Test Demonstrates a tank with one constant top inlet mass flow rate and a bottom outlet into the ambient |
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Modelica.Fluid.Examples.AST_BatchPlant.Test Demonstrates a tank with one constant top inlet mass flow rate and a bottom outlet into the ambient |
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Modelica.Fluid.Examples Multi-way connections of pipes and incompressible medium model |
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Modelica.Fluid.Examples Comparing a circular with a non-circular pipe |
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Modelica.Fluid.Examples.HeatExchanger Simulation for the heat exchanger model |
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Modelica.Fluid.Examples.TraceSubstances Demonstrates a room volume with CO2 accumulation |
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Modelica.Fluid.Examples.TraceSubstances Demonstrates a room volume with CO2 controls |
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Modelica.Fluid.Examples Demonstrates the parameterization of a pump and a pipe for given nominal values |
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Modelica.Fluid.Examples.Explanatory Differences between using one port with and without explicit junction model and two port sensors for fluid temperature measuring |
Used in Components (9)
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Modelica.Fluid.Examples.HeatExchanger.BaseClasses Simple heat exchanger model |
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Modelica.Fluid.Examples.HeatExchanger.BaseClasses Pipe wall with capacitance, assuming 1D heat conduction and constant material properties |
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Modelica.Fluid.Machines.BaseClasses.PumpMonitoring Interface for pump monitoring |
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Modelica.Fluid.Interfaces Partial component with two ports |
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Modelica.Fluid.Interfaces Common interface for heat transfer models |
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Modelica.Fluid.Interfaces Lumped volume with mass and energy balance |
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Modelica.Fluid.Interfaces Base class for a lumped momentum balance |
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Modelica.Fluid.Interfaces Base class for distributed volume models |
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Modelica.Fluid.Interfaces Base class for a distributed momentum balance |