Modelica.Fluid.Fittings

Information

Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).

Package Content

Name	Description
Bends	Flow models for bends
Orifices	Flow models for orifices
GenericResistances	Flow models for generic resistances
SimpleGenericOrifice	Simple generic orifice defined by pressure loss coefficient and diameter (only for flow from port_a to port_b)
SharpEdgedOrifice	Pressure drop due to sharp edged orifice (for both flow directions)
AbruptAdaptor	Pressure drop in pipe due to suddenly expanding or reducing area (for both flow directions)
MultiPort	Multiply a port; useful if multiple connections shall be made to a port exposing a state
TeeJunctionIdeal	Splitting/joining component with static balances for an infinitesimal control volume
TeeJunctionVolume	Splitting/joining component with static balances for a dynamic control volume
BaseClasses	Base classes used in the Fittings package (only of interest to build new component models)

Modelica.Fluid.Fittings.SimpleGenericOrifice

Information

This pressure drop component defines a simple, generic orifice, where the loss factor ζ is provided for one flow direction (e.g., from loss table of a book):

   Δp = 0.5*ζ*ρ*v*|v|
      = 8*ζ/(π^2*D^4*ρ) * m_flow*|m_flow|

where

• Δp is the pressure drop: Δp = port_a.p - port_b.p
• D is the diameter of the orifice at the position where ζ is defined (either at port_a or port_b). If the orifice has not a circular cross section, D = 4*A/P, where A is the cross section area and P is the wetted perimeter.
• ζ is the loss factor with respect to D that depends on the geometry of the orifice. In the turbulent flow regime, it is assumed that ζ is constant.
  For small mass flow rates, the flow is laminar and is approximated by a polynomial that has a finite derivative for m_flow=0.
• v is the mean velocity.
• ρ is the upstream density.

Since the pressure loss factor zeta is provided only for a mass flow from port_a to port_b, the pressure loss is not correct when the flow is reversing. If reversing flow only occurs in a short time interval, this is most likely uncritical. If significant reversing flow can appear, this component should not be used.

Extends from Modelica.Fluid.Interfaces.PartialTwoPortTransport (Partial element transporting fluid between two ports without storage of mass or energy), Modelica.Fluid.Interfaces.PartialLumpedFlow (Base class for a lumped momentum balance).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Length	pathLength	0	Length flow path [m]
Diameter	diameter		Diameter of orifice [m]
Real	zeta		Loss factor for flow of port_a -> port_b
Boolean	use_zeta	true	= false to obtain zeta from dp_nominal and m_flow_nominal
AbsolutePressure	dp_nominal	1e3	Nominal pressure drop [Pa]
MassFlowRate	m_flow_nominal	1	Mass flow rate for dp_nominal [kg/s]
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Dynamics
Dynamics	momentumDynamics	Types.Dynamics.SteadyState	Formulation of momentum balance
Advanced
AbsolutePressure	dp_start	0.01*system.p_start	Guess value of dp = port_a.p - port_b.p [Pa]
MassFlowRate	m_flow_start	system.m_flow_start	Guess value of m_flow = port_a.m_flow [kg/s]
MassFlowRate	m_flow_small	system.m_flow_small	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	from_dp	true	= true, use m_flow = f(dp) else dp = f(m_flow)
AbsolutePressure	dp_small	system.dp_small	Turbulent flow if |dp| >= dp_small [Pa]
Diagnostics
Boolean	show_T	true	= true, if temperatures at port_a and port_b are computed
Boolean	show_V_flow	true	= true, if volume flow rate at inflowing port is computed

Connectors

Type	Name	Description
FluidPort_a	port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_b	Fluid connector b (positive design flow direction is from port_a to port_b)

Modelica definition

model SimpleGenericOrifice 
  "Simple generic orifice defined by pressure loss coefficient and diameter (only for flow from port_a to port_b)"

  extends Modelica.Fluid.Interfaces.PartialTwoPortTransport;

  extends Modelica.Fluid.Interfaces.PartialLumpedFlow(
    final pathLength = 0,
    final momentumDynamics = Types.Dynamics.SteadyState);

  parameter SI.Diameter diameter "Diameter of orifice";
  parameter Real zeta "Loss factor for flow of port_a -> port_b";
  parameter Boolean use_zeta = true 
    "= false to obtain zeta from dp_nominal and m_flow_nominal";

  // Operational conditions
  parameter SI.AbsolutePressure dp_nominal = 1e3 "Nominal pressure drop";
  parameter SI.MassFlowRate m_flow_nominal = 1 "Mass flow rate for dp_nominal";

  parameter Boolean from_dp = true 
    "= true, use m_flow = f(dp) else dp = f(m_flow)";
  parameter Medium.AbsolutePressure dp_small = system.dp_small 
    "Turbulent flow if |dp| >= dp_small";

  // Variables
  Real zeta_nominal(start = zeta);
  Medium.Density d = 0.5*(Medium.density(state_a) + Medium.density(state_b));
  Modelica.SIunits.Pressure dp_fg(start=dp_start) 
    "pressure loss due to friction and gravity";
  Modelica.SIunits.Area A_mean = Modelica.Constants.pi/4*diameter^2 
    "mean cross flow area";

equation 
  if use_zeta then
    zeta_nominal = zeta;
  else
    dp_nominal = BaseClasses.lossConstant_D_zeta(diameter, zeta_nominal)/d*m_flow_nominal^2;
  end if;

  Ib_flow = 0;
  F_p = A_mean*(Medium.pressure(state_b) - Medium.pressure(state_a));
  F_fg = A_mean*dp_fg;

  /*
   dp = 0.5*zeta*d*v*|v|
      = 0.5*zeta*d*1/(d*A)^2 * m_flow * |m_flow|
      = 0.5*zeta/A^2 *1/d * m_flow * |m_flow|
      = k/d * m_flow * |m_flow|
   k  = 0.5*zeta/A^2
      = 0.5*zeta/(pi*(D/2)^2)^2
      = 8*zeta/(pi*D^2)^2
  */
  if from_dp then
    m_flow = Utilities.regRoot2(
        dp_fg,
        dp_small,
        Medium.density(state_a)/BaseClasses.lossConstant_D_zeta(diameter, zeta_nominal),
        Medium.density(state_b)/BaseClasses.lossConstant_D_zeta(diameter, zeta_nominal));
  else
    dp_fg = Utilities.regSquare2(
        m_flow,
        m_flow_small,
        BaseClasses.lossConstant_D_zeta(diameter, zeta_nominal)/Medium.density(state_a),
        BaseClasses.lossConstant_D_zeta(diameter, zeta_nominal)/Medium.density(state_b));
  end if;

  // Isenthalpic state transformation (no storage and no loss of energy)
  port_a.h_outflow = inStream(port_b.h_outflow);
  port_b.h_outflow = inStream(port_a.h_outflow);

end SimpleGenericOrifice;

Modelica.Fluid.Fittings.SharpEdgedOrifice

Information

Extends from BaseClasses.QuadraticTurbulent.BaseModel (Generic pressure drop component with constant turbulent loss factor data and without an icon).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
LossFactorData	data	BaseClasses.QuadraticTurbule...	Loss factor data
Length	length		Length of orifice [m]
Diameter	diameter		Inner diameter of pipe (= same at port_a and port_b) [m]
Diameter	leastDiameter		Smallest diameter of orifice [m]
Angle_deg	alpha		Angle of orifice [deg]
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
AbsolutePressure	dp_start	0.01*system.p_start	Guess value of dp = port_a.p - port_b.p [Pa]
MassFlowRate	m_flow_start	system.m_flow_start	Guess value of m_flow = port_a.m_flow [kg/s]
MassFlowRate	m_flow_small	system.m_flow_small	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	from_dp	true	= true, use m_flow = f(dp) else dp = f(m_flow)
Boolean	use_Re	false	= true, if turbulent region is defined by Re, otherwise by dp_small or m_flow_small
AbsolutePressure	dp_small	system.dp_small	Turbulent flow if |dp| >= dp_small [Pa]
Diagnostics
Boolean	show_T	true	= true, if temperatures at port_a and port_b are computed
Boolean	show_V_flow	true	= true, if volume flow rate at inflowing port is computed
Boolean	show_Re	false	= true, if Reynolds number is included for plotting

Connectors

Type	Name	Description
FluidPort_a	port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_b	Fluid connector b (positive design flow direction is from port_a to port_b)

Modelica definition

model SharpEdgedOrifice 
  "Pressure drop due to sharp edged orifice (for both flow directions)"
    import NonSI = Modelica.SIunits.Conversions.NonSIunits;
  extends BaseClasses.QuadraticTurbulent.BaseModel(final data=
          BaseClasses.QuadraticTurbulent.LossFactorData.sharpEdgedOrifice(
          diameter,
          leastDiameter,
          length,
          alpha));
  parameter SI.Length length "Length of orifice";
  parameter SI.Diameter diameter 
    "Inner diameter of pipe (= same at port_a and port_b)";
  parameter SI.Diameter leastDiameter "Smallest diameter of orifice";
  parameter NonSI.Angle_deg alpha "Angle of orifice";

end SharpEdgedOrifice;

Modelica.Fluid.Fittings.AbruptAdaptor

Information

Extends from BaseClasses.QuadraticTurbulent.BaseModelNonconstantCrossSectionArea (Generic pressure drop component with constant turbulent loss factor data and without an icon, for non-constant cross section area).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
LossFactorData	data	BaseClasses.QuadraticTurbule...	Loss factor data
Diameter	diameter_a		Inner diameter of pipe at port_a [m]
Diameter	diameter_b		Inner diameter of pipe at port_b [m]
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
AbsolutePressure	dp_start	0.01*system.p_start	Guess value of dp = port_a.p - port_b.p [Pa]
MassFlowRate	m_flow_start	system.m_flow_start	Guess value of m_flow = port_a.m_flow [kg/s]
MassFlowRate	m_flow_small	system.m_flow_small	Small mass flow rate for regularization of zero flow [kg/s]
AbsolutePressure	dp_small	system.dp_small	Turbulent flow if |dp| >= dp_small [Pa]
Diagnostics
Boolean	show_T	true	= true, if temperatures at port_a and port_b are computed
Boolean	show_V_flow	true	= true, if volume flow rate at inflowing port is computed
Boolean	show_Re	false	= true, if Reynolds number is included for plotting
Boolean	show_totalPressures	false	= true, if total pressures are included for plotting
Boolean	show_portVelocities	false	= true, if port velocities are included for plotting

Connectors

Type	Name	Description
FluidPort_a	port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_b	Fluid connector b (positive design flow direction is from port_a to port_b)

Modelica definition

model AbruptAdaptor 
  "Pressure drop in pipe due to suddenly expanding or reducing area (for both flow directions)"
  extends BaseClasses.QuadraticTurbulent.BaseModelNonconstantCrossSectionArea(final data=
          BaseClasses.QuadraticTurbulent.LossFactorData.suddenExpansion(
          diameter_a, diameter_b));
  parameter SI.Diameter diameter_a "Inner diameter of pipe at port_a";
  parameter SI.Diameter diameter_b "Inner diameter of pipe at port_b";

end AbruptAdaptor;

Modelica.Fluid.Fittings.MultiPort

Information

This model is useful if multiple connections shall be made to a port of a volume model exposing a state, like a pipe with ModelStructure av_vb. The mixing is shifted into the volume connected to port_a and the result is propageted back to each ports_b.

If multiple connections were directly made to the volume, then ideal mixing would take place in the connection set, outside the volume. This is normally not intended.

Connectors

Type	Name	Description
FluidPort_a	port_a
FluidPorts_b	ports_b[nPorts_b]

Modelica definition

model MultiPort 
  "Multiply a port; useful if multiple connections shall be made to a port exposing a state"

  function positiveMax
    input Real x;
    output Real y;
  algorithm 
    y :=max(x, 1e-10);
  end positiveMax;

  import Modelica.Constants;

  replaceable package Medium=Modelica.Media.Interfaces.PartialMedium;

  // Ports
  parameter Integer nPorts_b=0 
    "Number of outlet ports (mass is distributed evenly between the outlet ports";

  Modelica.Fluid.Interfaces.FluidPort_a port_a(
    redeclare package Medium=Medium);
  Modelica.Fluid.Interfaces.FluidPorts_b ports_b[nPorts_b](
    redeclare each package Medium=Medium);

  Medium.MassFraction ports_b_Xi_inStream[nPorts_b,Medium.nXi] 
    "inStream mass fractions at ports_b";
  Medium.ExtraProperty ports_b_C_inStream[nPorts_b,Medium.nC] 
    "inStream extra properties at ports_b";

equation 
  // Only one connection allowed to a port to avoid unwanted ideal mixing
  for i in 1:nPorts_b loop
    assert(cardinality(ports_b[i]) <= 1,"
each ports_b[i] of boundary shall at most be connected to one component.
If two or more connections are present, ideal mixing takes
place with these connections, which is usually not the intention
of the modeller. Increase nPorts_b to add an additional port.
");
  end for;

  // mass and momentum balance
  0 = port_a.m_flow + sum(ports_b.m_flow);
  ports_b.p = fill(port_a.p, nPorts_b);

  // mixing at port_a
  port_a.h_outflow = sum({positiveMax(ports_b[j].m_flow)*inStream(ports_b[j].h_outflow) for j in 1:nPorts_b})
                       / sum({positiveMax(ports_b[j].m_flow) for j in 1:nPorts_b});
  for j in 1:nPorts_b loop
     // expose stream values from port_a to ports_b
     ports_b[j].h_outflow  = inStream(port_a.h_outflow);
     ports_b[j].Xi_outflow = inStream(port_a.Xi_outflow);
     ports_b[j].C_outflow  = inStream(port_a.C_outflow);

     ports_b_Xi_inStream[j,:] = inStream(ports_b[j].Xi_outflow);
     ports_b_C_inStream[j,:] = inStream(ports_b[j].C_outflow);
  end for;
  for i in 1:Medium.nXi loop
    port_a.Xi_outflow[i] = (positiveMax(ports_b.m_flow)*ports_b_Xi_inStream[:,i])
                         / sum(positiveMax(ports_b.m_flow));
  end for;
  for i in 1:Medium.nC loop
    port_a.C_outflow[i] = (positiveMax(ports_b.m_flow)*ports_b_C_inStream[:,i])
                         / sum(positiveMax(ports_b.m_flow));
  end for;
end MultiPort;

Modelica.Fluid.Fittings.TeeJunctionIdeal

Information

Extends from Modelica.Fluid.Fittings.BaseClasses.PartialTeeJunction (Base class for a splitting/joining component with three ports).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component

Connectors

Type	Name	Description
FluidPort_a	port_1
FluidPort_b	port_2
FluidPort_a	port_3

Modelica definition

model TeeJunctionIdeal 
  "Splitting/joining component with static balances for an infinitesimal control volume"
  extends Modelica.Fluid.Fittings.BaseClasses.PartialTeeJunction;

equation 
  connect(port_1, port_2);
  connect(port_1, port_3);
end TeeJunctionIdeal;

Modelica.Fluid.Fittings.TeeJunctionVolume

Information

Extends from Modelica.Fluid.Fittings.BaseClasses.PartialTeeJunction (Base class for a splitting/joining component with three ports), Modelica.Fluid.Interfaces.PartialLumpedVolume (Lumped volume with mass and energy balance).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Volume	fluidVolume	V	Volume [m3]
Volume	V		Mixing volume inside junction [m3]
Assumptions
Dynamics
Dynamics	energyDynamics	system.energyDynamics	Formulation of energy balance
Dynamics	massDynamics	system.massDynamics	Formulation of mass balance
Initialization
AbsolutePressure	p_start	system.p_start	Start value of pressure [Pa]
Boolean	use_T_start	true	= true, use T_start, otherwise h_start
Temperature	T_start	if use_T_start then system.T...	Start value of temperature [K]
SpecificEnthalpy	h_start	if use_T_start then Medium.s...	Start value of specific enthalpy [J/kg]
MassFraction	X_start[Medium.nX]	Medium.X_default	Start value of mass fractions m_i/m [kg/kg]
ExtraProperty	C_start[Medium.nC]	fill(0, Medium.nC)	Start value of trace substances

Connectors

Type	Name	Description
FluidPort_a	port_1
FluidPort_b	port_2
FluidPort_a	port_3

Modelica definition

model TeeJunctionVolume 
  "Splitting/joining component with static balances for a dynamic control volume"
  extends Modelica.Fluid.Fittings.BaseClasses.PartialTeeJunction;
  extends Modelica.Fluid.Interfaces.PartialLumpedVolume(
    final fluidVolume = V);

  parameter SI.Volume V "Mixing volume inside junction";

equation 
  // Only one connection allowed to a port to avoid unwanted ideal mixing
  assert(cardinality(port_1) <= 1,"
port_1 of volume can at most be connected to one component.
If two or more connections are present, ideal mixing takes
place with these connections which is usually not the intention
of the modeller.
");
  assert(cardinality(port_2) <= 1,"
port_2 of volume can at most be connected to one component.
If two or more connections are present, ideal mixing takes
place with these connections which is usually not the intention
of the modeller.
");
  assert(cardinality(port_3) <= 1,"
port_3 of volume can at most be connected to one component.
If two or more connections are present, ideal mixing takes
place with these connections which is usually not the intention
of the modeller.
");

  // Boundary conditions
  port_1.h_outflow = medium.h;
  port_2.h_outflow = medium.h;
  port_3.h_outflow = medium.h;

  port_1.Xi_outflow = medium.Xi;
  port_2.Xi_outflow = medium.Xi;
  port_3.Xi_outflow = medium.Xi;

  port_1.C_outflow = C;
  port_2.C_outflow = C;
  port_3.C_outflow = C;

  // Mass balances
  mb_flow = port_1.m_flow + port_2.m_flow + port_3.m_flow "Mass balance";
  mbXi_flow = port_1.m_flow*actualStream(port_1.Xi_outflow)
              + port_2.m_flow*actualStream(port_2.Xi_outflow)
              + port_3.m_flow*actualStream(port_3.Xi_outflow) 
    "Component mass balances";

  mbC_flow  = port_1.m_flow*actualStream(port_1.C_outflow)
            + port_2.m_flow*actualStream(port_2.C_outflow)
            + port_3.m_flow*actualStream(port_3.C_outflow) 
    "Trace substance mass balances";

  // Momentum balance (suitable for compressible media)
  port_1.p = medium.p;
  port_2.p = medium.p;
  port_3.p = medium.p;

  // Energy balance
  Hb_flow = port_1.m_flow*actualStream(port_1.h_outflow)
            + port_2.m_flow*actualStream(port_2.h_outflow)
            + port_3.m_flow*actualStream(port_3.h_outflow);
  Qb_flow = 0;
  Wb_flow = 0;

end TeeJunctionVolume;