Modelica.Fluid.Valves

Components for the regulation and control of fluid flow

Information



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

Package Content

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

Modelica.Fluid.Valves.ValveIncompressible Modelica.Fluid.Valves.ValveIncompressible

Valve for (almost) incompressible fluids

Information


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

The parameters of this model are explained in detail in PartialValve (the base model for valves).

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 characteristic curve. Otherwise, reverse flow is stopped (check valve behaviour).

The treatment of parameters Kv and Cv is explained in detail in the User's Guide.

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

Parameters

NameDescription
replaceable package MediumMedium in the component
replaceable function valveCharacteristicInherent flow characteristic
Flow Coefficient
CvDataSelection of flow coefficient
AvAv (metric) flow coefficient [m2]
KvKv (metric) flow coefficient [m3/h]
CvCv (US) flow coefficient [USG/min]
Nominal operating point
dp_nominalNominal pressure drop [Pa]
m_flow_nominalNominal mass flowrate [kg/s]
rho_nominalNominal inlet density [kg/m3]
opening_nominalNominal opening
Filtered opening
filteredOpening= true, if opening is filtered with a 2nd order CriticalDamping filter
riseTimeRise time of the filter (time to reach 99.6 % of an opening step) [s]
leakageOpeningThe opening signal is limited by leakageOpening (to improve the numerics)
Assumptions
allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
checkValveReverse flow stopped
Advanced
dp_startGuess value of dp = port_a.p - port_b.p [Pa]
m_flow_startGuess value of m_flow = port_a.m_flow [kg/s]
m_flow_smallSmall mass flow rate for regularization of zero flow [kg/s]
use_Re= true, if turbulent region is defined by Re, otherwise by m_flow_small
Diagnostics
show_T= true, if temperatures at port_a and port_b are computed
show_V_flow= true, if volume flow rate at inflowing port is computed

Connectors

NameDescription
port_aFluid connector a (positive design flow direction is from port_a to port_b)
port_bFluid connector b (positive design flow direction is from port_a to port_b)
openingValve position in the range 0..1
opening_filteredFiltered valve position in the range 0..1

Modelica.Fluid.Valves.ValveVaporizing Modelica.Fluid.Valves.ValveVaporizing

Valve for possibly vaporizing (almost) incompressible fluids, accounts for choked flow conditions

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 parameters of this model are explained in detail in PartialValve (the base model for valves).

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 characteristic curve. Otherwise, reverse flow is stopped (check valve behaviour).

The treatment of parameters Kv and Cv is explained in detail in the User's Guide.

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

Parameters

NameDescription
replaceable package MediumMedium in the component
replaceable function valveCharacteristicInherent flow characteristic
Fl_nominalLiquid pressure recovery factor
replaceable function FlCharacteristicPressure recovery characteristic
Flow Coefficient
CvDataSelection of flow coefficient
AvAv (metric) flow coefficient [m2]
KvKv (metric) flow coefficient [m3/h]
CvCv (US) flow coefficient [USG/min]
Nominal operating point
dp_nominalNominal pressure drop [Pa]
m_flow_nominalNominal mass flowrate [kg/s]
rho_nominalNominal inlet density [kg/m3]
opening_nominalNominal opening
Filtered opening
filteredOpening= true, if opening is filtered with a 2nd order CriticalDamping filter
riseTimeRise time of the filter (time to reach 99.6 % of an opening step) [s]
leakageOpeningThe opening signal is limited by leakageOpening (to improve the numerics)
Assumptions
allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
checkValveReverse flow stopped
Advanced
dp_startGuess value of dp = port_a.p - port_b.p [Pa]
m_flow_startGuess value of m_flow = port_a.m_flow [kg/s]
m_flow_smallSmall mass flow rate for regularization of zero flow [kg/s]
use_Re= true, if turbulent region is defined by Re, otherwise by m_flow_small
Diagnostics
show_T= true, if temperatures at port_a and port_b are computed
show_V_flow= true, if volume flow rate at inflowing port is computed

Connectors

NameDescription
replaceable package MediumMedium in the component
port_aFluid connector a (positive design flow direction is from port_a to port_b)
port_bFluid connector b (positive design flow direction is from port_a to port_b)
openingValve position in the range 0..1
opening_filteredFiltered valve position in the range 0..1
replaceable function FlCharacteristicPressure recovery characteristic

Modelica.Fluid.Valves.ValveCompressible Modelica.Fluid.Valves.ValveCompressible

Valve for compressible fluids, accounts for choked flow conditions

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.

The parameters of this model are explained in detail in PartialValve (the base model for valves).

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 characteristic curve. Otherwise, reverse flow is stopped (check valve behaviour).

The treatment of parameters Kv and Cv is explained in detail in the User's Guide.

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

Parameters

NameDescription
replaceable package MediumMedium in the component
replaceable function valveCharacteristicInherent flow characteristic
Fxt_fullFk*xt critical ratio at full opening
replaceable function xtCharacteristicCritical ratio characteristic
Flow Coefficient
CvDataSelection of flow coefficient
AvAv (metric) flow coefficient [m2]
KvKv (metric) flow coefficient [m3/h]
CvCv (US) flow coefficient [USG/min]
Nominal operating point
dp_nominalNominal pressure drop [Pa]
m_flow_nominalNominal mass flowrate [kg/s]
rho_nominalNominal inlet density [kg/m3]
opening_nominalNominal opening
p_nominalNominal inlet pressure [Pa]
Filtered opening
filteredOpening= true, if opening is filtered with a 2nd order CriticalDamping filter
riseTimeRise time of the filter (time to reach 99.6 % of an opening step) [s]
leakageOpeningThe opening signal is limited by leakageOpening (to improve the numerics)
Assumptions
allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
checkValveReverse flow stopped
Advanced
dp_startGuess value of dp = port_a.p - port_b.p [Pa]
m_flow_startGuess value of m_flow = port_a.m_flow [kg/s]
m_flow_smallSmall mass flow rate for regularization of zero flow [kg/s]
use_Re= true, if turbulent region is defined by Re, otherwise by m_flow_small
Diagnostics
show_T= true, if temperatures at port_a and port_b are computed
show_V_flow= true, if volume flow rate at inflowing port is computed

Connectors

NameDescription
port_aFluid connector a (positive design flow direction is from port_a to port_b)
port_bFluid connector b (positive design flow direction is from port_a to port_b)
openingValve position in the range 0..1
opening_filteredFiltered valve position in the range 0..1
replaceable function xtCharacteristicCritical ratio characteristic

Modelica.Fluid.Valves.ValveLinear Modelica.Fluid.Valves.ValveLinear

Valve for water/steam flows with linear pressure drop

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

NameDescription
replaceable package MediumMedium in the component
m_flow_nominalNominal mass flowrate at full opening [kg/s]
Nominal operating point
dp_nominalNominal pressure drop at full opening [Pa]
Assumptions
allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
dp_startGuess value of dp = port_a.p - port_b.p [Pa]
m_flow_startGuess value of m_flow = port_a.m_flow [kg/s]
m_flow_smallSmall mass flow rate for regularization of zero flow [kg/s]
Diagnostics
show_T= true, if temperatures at port_a and port_b are computed
show_V_flow= true, if volume flow rate at inflowing port is computed

Connectors

NameDescription
port_aFluid connector a (positive design flow direction is from port_a to port_b)
port_bFluid connector b (positive design flow direction is from port_a to port_b)
opening=1: completely open, =0: completely closed

Modelica.Fluid.Valves.ValveDiscrete Modelica.Fluid.Valves.ValveDiscrete

Valve for water/steam flows with linear pressure drop

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

NameDescription
replaceable package MediumMedium in the component
m_flow_nominalNominal mass flowrate at full opening=1 [kg/s]
opening_minRemaining opening if closed, causing small leakage flow
Nominal operating point
dp_nominalNominal pressure drop at full opening=1 [Pa]
Assumptions
allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
dp_startGuess value of dp = port_a.p - port_b.p [Pa]
m_flow_startGuess value of m_flow = port_a.m_flow [kg/s]
m_flow_smallSmall mass flow rate for regularization of zero flow [kg/s]
Diagnostics
show_T= true, if temperatures at port_a and port_b are computed
show_V_flow= true, if volume flow rate at inflowing port is computed

Connectors

NameDescription
port_aFluid connector a (positive design flow direction is from port_a to port_b)
port_bFluid connector b (positive design flow direction is from port_a to port_b)
open 

Automatically generated Mon Sep 23 17:20:48 2013.