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

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
ValveDiscreteRamp	Valve for water/steam flows with discrete opening signal and ramp opening
BaseClasses	Base classes used in the Valves package (only of interest to build new component models)

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.

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

Connectors

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

Connectors

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

Connectors

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

Connectors

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

Connectors

Modelica.Fluid.Valves.ValveDiscreteRamp

Valve for water/steam flows with discrete opening signal and ramp opening

Information

This model is similar to ValveDiscrete, except that the valve opens gradually with an opening time Topen and closes gradually with a closing time Tclose instead of doing so abruptly. This can help to avoid unrealistic phenomena such as reversing flows when accurate fluid models with small compressiblity are employed.

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

Parameters

Connectors