AixLib.Fluid.FixedResistances.Junction

# .AixLib.Fluid.FixedResistances.Junction

Flow splitter with fixed resistance at each port

## Information

Model of a flow junction with an optional fixed resistance in each flow leg and an optional mixing volume at the junction.

The pressure drop is implemented using the model AixLib.Fluid.FixedResistances.PressureDrop. If its nominal pressure drop is set to zero, then the pressure drop model will be removed. For example, the pressure drop declaration

      m_flow_nominal={ 0.1, 0.1,  -0.2},
      dp_nominal =   {500,    0, -6000}

would model a flow mixer that has the nominal flow rates and associated pressure drops as shown in the figure below. Note that `port_3` is set to negative values. The negative values indicate that at the nominal conditions, fluid is leaving the component.

If `energyDynamics <> Modelica.Fluid.Types.Dynamics.SteadyState`, then at the flow junction, a fluid volume is modeled. The fluid volume is implemented using the model AixLib.Fluid.Delays.DelayFirstOrder. The fluid volume has the size

      V = sum(abs(m_flow_nominal[:])/3)*tau/rho_nominal

where `tau` is a parameter and `rho_nominal` is the density of the medium in the volume at nominal condition. Setting `energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial` can help reducing the size of the nonlinear system of equations.

## Revisions

- April 14, 2020, by Michael Wetter:
  Changed `homotopyInitialization` to a constant.
  This is for IBPSA, #1341.
- February 26, 2020, by Michael Wetter:
  Changed icon to display its operating state.
  This is for #1294.
- March 26, 2018 by Filip Jorissen:
  Removed `final allowFlowReversal=true` from all resistances since this overrides the default simplification when the flow is not bidirectional. This change can lead to smaller algebraic loops. This is for issue 898.
- December 1, 2016, by Michael Wetter:
  Renamed model from `SplitterFixedResistanceDpM` to `FlowJunction` and removed the parameters `use_dh`, `dh` and `ReC`.
  This is for issue 451.
- October 14, 2016 by Michael Wetter:
  Added to Annex 60 library.
  Updated comment for parameter `use_dh`.
  This is for issue 451.
- Removed parameter `dynamicBalance` that overwrote the setting of `energyDynamics` and `massDynamics`. This is for Annex 60, issue 411.
- February 1, 2012 by Michael Wetter:
  Expanded documentation.
- August 4, 2011 by Michael Wetter:
  Added `final allowFlowReversal=true` to all resistances since it is impractical to avoid flow reversal in large flow networks where such a setting may be useful.
- June 11, 2008 by Michael Wetter:
  Based class on AixLib.Fluid.BaseClasses.PartialThreeWayFixedResistance.
- July 20, 2007 by Michael Wetter:
  First implementation.

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