Modelica.Fluid.Valves

Information

Extends from Modelica.Fluid.Icons.VariantLibrary (Icon for a library that contains several variants of one component).

Package Content

Name	Description
ValveIncompressible	Valve for (almost) incompressible fluids
ValveVaporizing	Valve for possibly vaporizing (almost) incompressible fluids, accounts for choked flow conditions
ValveCompressible	Valve for compressible fluids, accounts for choked flow conditions
ValveLinear	Valve for water/steam flows with linear pressure drop
ValveDiscrete	Valve for water/steam flows with linear pressure drop
BaseClasses	Base classes used in the Valves package (only of interest to build new component models)

Modelica.Fluid.Valves.ValveIncompressible

Information

Valve model according to the IEC 534/ISA S.75 standards for valve sizing, incompressible fluids.

This model assumes that the fluid has a low compressibility, which is always the case for liquids. It can also be used with gases, provided that the pressure drop is lower than 0.2 times the absolute pressure at the inlet, so that the fluid density does not change much inside the valve.

If checkValve is false, the valve supports reverse flow, with a symmetric flow characteric curve. Otherwise, reverse flow is stopped (check valve behaviour).

The treatment of parameters Kv and Cv is explained in detail in the Users Guide.

Extends from BaseClasses.PartialValve (Base model for valves).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
replaceable function valveCharacteristic		linear	Inherent flow characteristic
Flow Coefficient
CvTypes	CvData	CvTypes.OpPoint	Selection of flow coefficient
Area	Av	0	Av (metric) flow coefficient [m2]
Real	Kv	0	Kv (metric) flow coefficient [m3/h]
Real	Cv	0	Cv (US) flow coefficient [USG/min]
Nominal operating point
Pressure	dp_nominal		Nominal pressure drop [Pa]
MassFlowRate	m_flow_nominal		Nominal mass flowrate [kg/s]
Density	rho_nominal	Medium.density_pTX(Medium.p_...	Nominal inlet density [kg/m3]
Real	opening_nominal	1	Nominal opening
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Boolean	checkValve	false	Reverse flow stopped
Advanced
AbsolutePressure	dp_start	dp_nominal	Guess value of dp = port_a.p - port_b.p [Pa]
MassFlowRate	m_flow_start	m_flow_nominal	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]
Pressure	dp_small	system.dp_small	Regularisation of zero flow [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)
input RealInput	opening	Valve position in the range 0-1

Modelica definition

model ValveIncompressible "Valve for (almost) incompressible fluids"
  extends BaseClasses.PartialValve;
import Modelica.Fluid.Types.CvTypes;

initial equation 
  if CvData == CvTypes.OpPoint then
      m_flow_nominal = valveCharacteristic(opening_nominal)*Av*sqrt(rho_nominal)*Utilities.regRoot(dp_nominal, dp_small) 
      "Determination of Av by the operating point";
  end if;

equation 
  // m_flow = valveCharacteristic(opening)*Av*sqrt(d)*sqrt(dp);
  if checkValve then
    m_flow = valveCharacteristic(opening)*Av*sqrt(Medium.density(state_a))*
                  (if dp>=0 then Utilities.regRoot(dp, dp_small) else 0);
  elseif not allowFlowReversal then
    m_flow = valveCharacteristic(opening)*Av*sqrt(Medium.density(state_a))*
                  Utilities.regRoot(dp, dp_small);
  else
    m_flow = valveCharacteristic(opening)*Av*
      smooth(0, Utilities.regRoot(dp, dp_small)*(if dp>=0 then sqrt(Medium.density(state_a)) else sqrt(Medium.density(state_b))));
  end if;

end ValveIncompressible;

Modelica.Fluid.Valves.ValveVaporizing

Information

Valve model according to the IEC 534/ISA S.75 standards for valve sizing, incompressible fluid at the inlet, and possibly two-phase fluid at the outlet, including choked flow conditions.

The model operating range includes choked flow operation, which takes place for low outlet pressures due to flashing in the vena contracta; otherwise, non-choking conditions are assumed.

This model requires a two-phase medium model, to describe the liquid and (possible) two-phase conditions.

The default liquid pressure recovery coefficient Fl is constant and given by the parameter Fl_nominal. The relative change (per unit) of the recovery coefficient can be specified as a given function of the valve opening by replacing the FlCharacteristic function.

If checkValve is false, the valve supports reverse flow, with a symmetric flow characteric curve. Otherwise, reverse flow is stopped (check valve behaviour).

The treatment of parameters Kv and Cv is explained in detail in the Users Guide.

Extends from BaseClasses.PartialValve (Base model for valves).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
replaceable function valveCharacteristic		linear	Inherent flow characteristic
Real	Fl_nominal	0.9	Liquid pressure recovery factor
replaceable function FlCharacteristic		Modelica.Fluid.Valves.BaseCl...	Pressure recovery characteristic
Flow Coefficient
CvTypes	CvData	CvTypes.OpPoint	Selection of flow coefficient
Area	Av	0	Av (metric) flow coefficient [m2]
Real	Kv	0	Kv (metric) flow coefficient [m3/h]
Real	Cv	0	Cv (US) flow coefficient [USG/min]
Nominal operating point
Pressure	dp_nominal		Nominal pressure drop [Pa]
MassFlowRate	m_flow_nominal		Nominal mass flowrate [kg/s]
Density	rho_nominal	Medium.density_pTX(Medium.p_...	Nominal inlet density [kg/m3]
Real	opening_nominal	1	Nominal opening
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Boolean	checkValve	false	Reverse flow stopped
Advanced
AbsolutePressure	dp_start	dp_nominal	Guess value of dp = port_a.p - port_b.p [Pa]
MassFlowRate	m_flow_start	m_flow_nominal	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]
Pressure	dp_small	system.dp_small	Regularisation of zero flow [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
replaceable package Medium		Medium in the component
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)
input RealInput	opening	Valve position in the range 0-1
replaceable function FlCharacteristic		Pressure recovery characteristic

Modelica definition

model ValveVaporizing 
  "Valve for possibly vaporizing (almost) incompressible fluids, accounts for choked flow conditions"
  import Modelica.Fluid.Types.CvTypes;
  extends BaseClasses.PartialValve(
    redeclare replaceable package Medium = 
        Modelica.Media.Water.WaterIF97_ph                                    constrainedby 
      Modelica.Media.Interfaces.PartialTwoPhaseMedium);
  parameter Real Fl_nominal=0.9 "Liquid pressure recovery factor";
  replaceable function FlCharacteristic = 
      Modelica.Fluid.Valves.BaseClasses.ValveCharacteristics.one 
    constrainedby 
    Modelica.Fluid.Valves.BaseClasses.ValveCharacteristics.baseFun 
    "Pressure recovery characteristic";
  Real Ff "Ff coefficient (see IEC/ISA standard)";
  Real Fl "Pressure recovery coefficient Fl (see IEC/ISA standard)";
  SI.Pressure dpEff "Effective pressure drop";
  Medium.Temperature T_in "Inlet temperature";
  Medium.AbsolutePressure p_sat "Saturation pressure";
  Medium.AbsolutePressure p_in "Inlet pressure";
  Medium.AbsolutePressure p_out "Outlet pressure";
initial equation 
  assert(not CvData == CvTypes.OpPoint, "OpPoint option not supported for vaporizing valve");
equation 
  p_in = port_a.p;
  p_out = port_b.p;
  T_in = Medium.temperature(state_a);
  p_sat = Medium.saturationPressure(T_in);
  Ff = 0.96 - 0.28*sqrt(p_sat/Medium.fluidConstants[1].criticalPressure);
  Fl = Fl_nominal*FlCharacteristic(opening);
  dpEff = if p_out < (1 - Fl^2)*p_in + Ff*Fl^2*p_sat then 
            Fl^2*(p_in - Ff*p_sat) else dp 
    "Effective pressure drop, accounting for possible choked conditions";
  // m_flow = valveCharacteristic(opening)*Av*sqrt(d)*sqrt(dpEff);
  if checkValve then
    m_flow = valveCharacteristic(opening)*Av*sqrt(Medium.density(state_a))*
                  (if dpEff>=0 then Utilities.regRoot(dpEff, dp_small) else 0);
  elseif not allowFlowReversal then
    m_flow = valveCharacteristic(opening)*Av*sqrt(Medium.density(state_a))*
                  Utilities.regRoot(dpEff, dp_small);
  else
     m_flow = valveCharacteristic(opening)*Av*
      smooth(0, Utilities.regRoot(dpEff, dp_small)*(if dpEff>=0 then sqrt(Medium.density(state_a)) else sqrt(Medium.density(state_b))));
  end if;

end ValveVaporizing;

Modelica.Fluid.Valves.ValveCompressible

Information

Valve model according to the IEC 534/ISA S.75 standards for valve sizing, compressible fluid, no phase change, also covering choked-flow conditions.

This model can be used with gases and vapours, with arbitrary pressure ratio between inlet and outlet.

The product Fk*xt is given by the parameter Fxt_full, and is assumed constant by default. The relative change (per unit) of the xt coefficient with the valve opening can be specified by replacing the xtCharacteristic function.

If checkValve is false, the valve supports reverse flow, with a symmetric flow characteric curve. Otherwise, reverse flow is stopped (check valve behaviour).

The treatment of parameters Kv and Cv is explained in detail in the Users Guide.

Extends from BaseClasses.PartialValve (Base model for valves).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
replaceable function valveCharacteristic		linear	Inherent flow characteristic
Real	Fxt_full	0.5	Fk*xt critical ratio at full opening
replaceable function xtCharacteristic		Modelica.Fluid.Valves.BaseCl...	Critical ratio characteristic
Flow Coefficient
CvTypes	CvData	CvTypes.OpPoint	Selection of flow coefficient
Area	Av	0	Av (metric) flow coefficient [m2]
Real	Kv	0	Kv (metric) flow coefficient [m3/h]
Real	Cv	0	Cv (US) flow coefficient [USG/min]
Nominal operating point
Pressure	dp_nominal		Nominal pressure drop [Pa]
MassFlowRate	m_flow_nominal		Nominal mass flowrate [kg/s]
Density	rho_nominal	Medium.density_pTX(Medium.p_...	Nominal inlet density [kg/m3]
Real	opening_nominal	1	Nominal opening
AbsolutePressure	p_nominal		Nominal inlet pressure [Pa]
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Boolean	checkValve	false	Reverse flow stopped
Advanced
AbsolutePressure	dp_start	dp_nominal	Guess value of dp = port_a.p - port_b.p [Pa]
MassFlowRate	m_flow_start	m_flow_nominal	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]
Pressure	dp_small	system.dp_small	Regularisation of zero flow [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)
input RealInput	opening	Valve position in the range 0-1
replaceable function xtCharacteristic		Critical ratio characteristic

Modelica definition

model ValveCompressible 
  "Valve for compressible fluids, accounts for choked flow conditions"
  extends BaseClasses.PartialValve;
  import Modelica.Fluid.Types.CvTypes;
  parameter Medium.AbsolutePressure p_nominal "Nominal inlet pressure";
  parameter Real Fxt_full=0.5 "Fk*xt critical ratio at full opening";
  replaceable function xtCharacteristic = 
      Modelica.Fluid.Valves.BaseClasses.ValveCharacteristics.one 
    constrainedby 
    Modelica.Fluid.Valves.BaseClasses.ValveCharacteristics.baseFun 
    "Critical ratio characteristic";
  Real Fxt;
  Real x "Pressure drop ratio";
  Real xs "Saturated pressure drop ratio";
  Real Y "Compressibility factor";
  Medium.AbsolutePressure p "Inlet pressure";
protected 
  parameter Real Fxt_nominal(fixed=false) "Nominal Fxt";
  parameter Real x_nominal(fixed=false) "Nominal pressure drop ratio";
  parameter Real xs_nominal(fixed=false) 
    "Nominal saturated pressure drop ratio";
  parameter Real Y_nominal(fixed=false) "Nominal compressibility factor";

initial equation 
  if CvData == CvTypes.OpPoint then
    // Determination of Av by the nominal operating point conditions
    Fxt_nominal = Fxt_full*xtCharacteristic(opening_nominal);
    x_nominal = dp_nominal/p_nominal;
    xs_nominal = smooth(0, if x_nominal > Fxt_nominal then Fxt_nominal else x_nominal);
    Y_nominal = 1 - abs(xs_nominal)/(3*Fxt_nominal);
    m_flow_nominal = valveCharacteristic(opening_nominal)*Av*Y_nominal*sqrt(rho_nominal)*Utilities.regRoot(p_nominal*xs_nominal, dp_small);
  else
    // Dummy values
    Fxt_nominal = 0;
    x_nominal = 0;
    xs_nominal = 0;
    Y_nominal = 0;
  end if;

equation 
  p = noEvent(if dp>=0 then port_a.p else port_b.p);
  Fxt = Fxt_full*xtCharacteristic(opening);
  x = dp/p;
  xs = smooth(0, if x < -Fxt then -Fxt else if x > Fxt then Fxt else x);
  Y = 1 - abs(xs)/(3*Fxt);
  // m_flow = valveCharacteristic(opening)*Av*Y*sqrt(d)*sqrt(p*xs);
  if checkValve then
    m_flow = valveCharacteristic(opening)*Av*Y*sqrt(Medium.density(state_a))*
      (if xs>=0 then Utilities.regRoot(p*xs, dp_small) else 0);
  elseif not allowFlowReversal then
    m_flow = valveCharacteristic(opening)*Av*sqrt(Medium.density(state_a))*
                  Utilities.regRoot(p*xs, dp_small);
  else
    m_flow = valveCharacteristic(opening)*Av*Y*
      smooth(0, Utilities.regRoot(p*xs, dp_small)*(if xs>=0 then sqrt(Medium.density(state_a)) else sqrt(Medium.density(state_b))));
/*
    m_flow = valveCharacteristic(opening)*Av*Y*
                  Modelica.Fluid.Utilities.regRoot2(p*xs, dp_small, Medium.density(state_a), Medium.density(state_b));
*/
  end if;

end ValveCompressible;

Modelica.Fluid.Valves.ValveLinear

Information

This very simple model provides a pressure drop which is proportional to the flowrate and to the opening input, without computing any fluid property. It can be used for testing purposes, when a simple model of a variable pressure loss is needed.

A medium model must be nevertheless be specified, so that the fluid ports can be connected to other components using the same medium model.

The model is adiabatic (no heat losses to the ambient) and neglects changes in kinetic energy from the inlet to the outlet.

Extends from Modelica.Fluid.Interfaces.PartialTwoPortTransport (Partial element transporting fluid between two ports without storage of mass or energy).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
AbsolutePressure	dp_nominal		Nominal pressure drop at full opening [Pa]
MassFlowRate	m_flow_nominal		Nominal mass flowrate at full opening [kg/s]
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]
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)
input RealInput	opening	=1: completely open, =0: completely closed

Modelica definition

model ValveLinear 
  "Valve for water/steam flows with linear pressure drop"
  extends Modelica.Fluid.Interfaces.PartialTwoPortTransport;
  parameter SI.AbsolutePressure dp_nominal 
    "Nominal pressure drop at full opening";
  parameter Medium.MassFlowRate m_flow_nominal 
    "Nominal mass flowrate at full opening";
  final parameter Types.HydraulicConductance k = m_flow_nominal/dp_nominal 
    "Hydraulic conductance at full opening";
  Modelica.Blocks.Interfaces.RealInput opening(min=0,max=1) 
    "=1: completely open, =0: completely closed";

equation 
  m_flow = opening*k*dp;

  // 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 ValveLinear;

Modelica.Fluid.Valves.ValveDiscrete

Information

This very simple model provides a (small) pressure drop which is proportional to the flowrate if the Boolean open signal is true. Otherwise, the mass flow rate is zero. If opening_min > 0, a small leakage mass flow rate occurs when open = false.

This model can be used for simplified modelling of on-off valves, when it is not important to accurately describe the pressure loss when the valve is open. Although the medium model is not used to determine the pressure loss, it must be nevertheless be specified, so that the fluid ports can be connected to other components using the same medium model.

The model is adiabatic (no heat losses to the ambient) and neglects changes in kinetic energy from the inlet to the outlet.

In a diagram animation, the valve is shown in "green", when it is open.

Extends from Modelica.Fluid.Interfaces.PartialTwoPortTransport (Partial element transporting fluid between two ports without storage of mass or energy).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Pressure	dp_nominal		Nominal pressure drop at full opening=1 [Pa]
MassFlowRate	m_flow_nominal		Nominal mass flowrate at full opening=1 [kg/s]
Real	opening_min	0	Remaining opening if closed, causing small leakage flow
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]
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)
input BooleanInput	open

Modelica definition

model ValveDiscrete 
  "Valve for water/steam flows with linear pressure drop"
  extends Modelica.Fluid.Interfaces.PartialTwoPortTransport;
  parameter SI.Pressure dp_nominal "Nominal pressure drop at full opening=1";
  parameter Medium.MassFlowRate m_flow_nominal 
    "Nominal mass flowrate at full opening=1";
  final parameter Types.HydraulicConductance k = m_flow_nominal/dp_nominal 
    "Hydraulic conductance at full opening=1";
  Modelica.Blocks.Interfaces.BooleanInput open;
  parameter Real opening_min(min=0)=0 
    "Remaining opening if closed, causing small leakage flow";
equation 
  m_flow = if open then 1*k*dp else opening_min*k*dp;

  // 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 ValveDiscrete;