WOLFRAM SYSTEMMODELER

System

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

Wolfram Language

In[1]:=
SystemModel["Modelica.Fluid.System"]
Out[1]:=

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

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 (23)

PumpingSystem

Modelica.Fluid.Examples

Model of a pumping system for drinking water

HeatingSystem

Modelica.Fluid.Examples

Simple model of a heating system

DrumBoiler

Modelica.Fluid.Examples.DrumBoiler

Complete drum boiler model, including evaporator and supplementary components

ThreeTanks

Modelica.Fluid.Examples.Tanks

Demonstrating the usage of SimpleTank

TanksWithOverflow

Modelica.Fluid.Examples.Tanks

Two tanks connected with pipes at different heights

EmptyTanks

Modelica.Fluid.Examples.Tanks

Show the treatment of empty tanks

ControlledTanks

Modelica.Fluid.Examples.ControlledTankSystem

Demonstrating the controller of a tank filling/emptying system

BatchPlant_StandardWater

Modelica.Fluid.Examples.AST_BatchPlant

OneTank

Modelica.Fluid.Examples.AST_BatchPlant.Test

Tank with one time-varying top inlet mass flow rate and a bottom outlet into the ambient

TwoTanks

Modelica.Fluid.Examples.AST_BatchPlant.Test

TankWithEmptyingPipe1

Modelica.Fluid.Examples.AST_BatchPlant.Test

Demonstrates a tank with one constant top inlet mass flow rate and a bottom outlet into the ambient

TankWithEmptyingPipe2

Modelica.Fluid.Examples.AST_BatchPlant.Test

Demonstrates a tank with one constant top inlet mass flow rate and a bottom outlet into the ambient

TanksWithEmptyingPipe1

Modelica.Fluid.Examples.AST_BatchPlant.Test

Demonstrates a tank with one constant top inlet mass flow rate and a bottom outlet into the ambient

TanksWithEmptyingPipe2

Modelica.Fluid.Examples.AST_BatchPlant.Test

Demonstrates a tank with one constant top inlet mass flow rate and a bottom outlet into the ambient

IncompressibleFluidNetwork

Modelica.Fluid.Examples

Multi-way connections of pipes and incompressible medium model

BranchingDynamicPipes

Modelica.Fluid.Examples

Multi-way connections of pipes with dynamic momentum balance, pressure wave and flow reversal

NonCircularPipes

Modelica.Fluid.Examples

Comparing a circular with a non-circular pipe

HeatExchangerSimulation

Modelica.Fluid.Examples.HeatExchanger

simulation for the heat exchanger model

RoomCO2

Modelica.Fluid.Examples.TraceSubstances

Demonstrates a room volume with CO2 accumulation

RoomCO2WithControls

Modelica.Fluid.Examples.TraceSubstances

Demonstrates a room volume with CO2 controls

InverseParameterization

Modelica.Fluid.Examples

Demonstrates the parameterization of a pump and a pipe for given nominal values

MeasuringTemperature

Modelica.Fluid.Examples.Explanatory

Differences between using one port with and without explicit junction model and two port sensors for fluid temperature measuring

MomentumBalanceFittings

Modelica.Fluid.Examples.Explanatory

Illustrating a case in which kinetic terms play a major role in the momentum balance

Used in Components (9)

BasicHX

Modelica.Fluid.Examples.HeatExchanger.BaseClasses

Simple heat exchanger model

WallConstProps

Modelica.Fluid.Examples.HeatExchanger.BaseClasses

Pipe wall with capacitance, assuming 1D heat conduction and constant material properties

PumpMonitoringBase

Modelica.Fluid.Machines.BaseClasses.PumpMonitoring

Interface for pump monitoring

PartialTwoPort

Modelica.Fluid.Interfaces

Partial component with two ports

PartialHeatTransfer

Modelica.Fluid.Interfaces

Common interface for heat transfer models

PartialLumpedVolume

Modelica.Fluid.Interfaces

Lumped volume with mass and energy balance

PartialLumpedFlow

Modelica.Fluid.Interfaces

Base class for a lumped momentum balance

PartialDistributedVolume

Modelica.Fluid.Interfaces

Base class for distributed volume models

PartialDistributedFlow

Modelica.Fluid.Interfaces

Base class for a distributed momentum balance