Buildings.Fluid.Actuators.Valves

Package with valve models

Information

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

Package Content

Name	Description
ThreeWayEqualPercentageLinear	Three way valve with equal percentage and linear characteristics
ThreeWayLinear	Three way valve with linear characteristics
ThreeWayTable	Three way valve with table-specified characteristics
TwoWayEqualPercentage	Two way valve with equal percentage flow characteristics
TwoWayLinear	Two way valve with linear flow characteristics
TwoWayPolynomial	Two way valve with polynomial characteristic
TwoWayPressureIndependent	Model of a pressure-independent two way valve
TwoWayQuickOpening	Two way valve with quick opening flow characteristics
TwoWayTable	Two way valve with table-specified flow characteristics
Data	Data records for table-based valves
Examples	Collection of models that illustrate model use and test models
Validation	Collection of validation models

Buildings.Fluid.Actuators.Valves.ThreeWayEqualPercentageLinear

Three way valve with equal percentage and linear characteristics

Information

Three way valve with equal percentage characteristics between port_1 and port_2 and linear opening characteristic between port_3 and port_2. Such opening characteristics were typical for valves from Landis & Gyr (now Siemens).

This model is based on the partial valve models Buildings.Fluid.Actuators.BaseClasses.PartialThreeWayValve and Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve. See Buildings.Fluid.Actuators.BaseClasses.PartialThreeWayValve for the implementation of the three way valve and see Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve for the implementation of the regularization near the origin.

Extends from BaseClasses.PartialThreeWayValve (Partial three way valve).

Parameters

Connectors

Modelica definition

Buildings.Fluid.Actuators.Valves.ThreeWayLinear

Three way valve with linear characteristics

Information

Three way valve with linear opening characteristic.

This model is based on the partial valve models Buildings.Fluid.Actuators.BaseClasses.PartialThreeWayValve and Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve. See Buildings.Fluid.Actuators.BaseClasses.PartialThreeWayValve for the implementation of the three way valve and see Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve for the implementation of the regularization near the origin.

Extends from BaseClasses.PartialThreeWayValve (Partial three way valve).

Parameters

Connectors

Modelica definition

Buildings.Fluid.Actuators.Valves.ThreeWayTable

Three way valve with table-specified characteristics

Information

Three way valve with table-specified opening characteristics. A separate characteristic for each flow path is used.

Each flow path uses an instance of the model Buildings.Fluid.Actuators.Valves.TwoWayTable. Therefore, this model needs to be parameterized the same way as Buildings.Fluid.Actuators.Valves.TwoWayTable. Specifically, the mass flow rate for the fully open valve is determined based on the value of the parameter CvData. For the different valve positions y ∈ [0, 1], this nominal flow rate is scaled by the values of the parameter flowCharacteristics1 and flowCharacteristics3, respectively. These parameters declare a table of the form

where l = K_v(y=0)/K_v(y=1) > 0 is the valve leakage. The first row is the valve opening, and the second row is the mass flow rate, relative to the mass flow rate of the fully open valve, under the assumption of a constant pressure difference across the valve. A suggested value for the valve leakage is l=0.0001. If l = 0, then this model will replace it with l = 10^-8 for numerical reasons. For example, if a valve has K_v=0.5 [m³/h/bar^1/2] and a linear opening characteristics and a valve leakage of l=0.0001, then one would set

 CvData=Buildings.Fluid.Types.CvTypes.Kv
 Kv = 0.5
 flowCharacteristics1(y={0,1}, phi={0.0001,1})
 flowCharacteristics3(y={0,1}, phi={0.0001,1})

Note, however, that Buildings.Fluid.Actuators.Valves.ThreeWayLinear provides a more efficient implementation for this simple case.

The parameters flowCharacteristics1 and flowCharacteristics3 must meet the following requirements, otherwise the model stops with an error:

• Their arrays y and phi must be strictly monotonic increasing.
• The first value must satisfy y[1]=0, and phi[1] must be equal to the leakage flow rate, which must be bigger than zero. Otherwise, a default value of 1E-8 is used.
• The last values must satisfy y[end]=1 and phi[end]=1.

This model is based on the partial valve model Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve. Check this model for more information, such as the regularization near the origin.

For an example that specifies an opening characteristics, see Buildings.Fluid.Actuators.Valves.Examples.TwoWayValveTable.

Extends from BaseClasses.PartialThreeWayValve (Partial three way valve).

Parameters

Connectors

Modelica definition

Buildings.Fluid.Actuators.Valves.TwoWayEqualPercentage

Two way valve with equal percentage flow characteristics

Information

Two way valve with an equal percentage valve opening characteristic.

This model is based on the partial valve model Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve. Check this model for more information, such as the regularization near the origin.

Extends from BaseClasses.PartialTwoWayValveKv (Partial model for a two way valve using a Kv characteristic).

Parameters

Connectors

Modelica definition

Buildings.Fluid.Actuators.Valves.TwoWayLinear

Two way valve with linear flow characteristics

Information

Two way valve with linear opening characteristic.

This model is based on the partial valve model Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve. Check this model for more information, such as the regularization near the origin.

Extends from BaseClasses.PartialTwoWayValveKv (Partial model for a two way valve using a Kv characteristic).

Parameters

Connectors

Modelica definition

Buildings.Fluid.Actuators.Valves.TwoWayPolynomial

Two way valve with polynomial characteristic

Information

Two way valve with polynomial opening characteristic. The polynomial coefficients are defined using parameter c. The elements of c are coefficients for increasing powers of y, starting with the power 0, which corresponds to a fixed offset. This valve model can be used to implement valves with a custom opening characteristic, such as a combination of a linear and an equal percentage characteristic.

This model is based on the partial valve model Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve. Check this model for more information, such as the regularization near the origin.

Extends from Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValveKv (Partial model for a two way valve using a Kv characteristic).

Parameters

Connectors

Modelica definition

Buildings.Fluid.Actuators.Valves.TwoWayPressureIndependent

Model of a pressure-independent two way valve

Information

Two way valve with a pressure-independent valve opening characteristic. The mass flow rate is controlled such that it is nearly equal to its set point y*m_flow_nominal, unless the pressure dp is too low, in which case a regular Kv characteristic is used.

Main equations

First the minimum pressure head dp_min required for delivering the requested mass flow rate y*m_flow_nominal is computed. If dp > dp_min then the requested mass flow rate is supplied. If dp < dp_min then m_flow = Kv/sqrt(dp). Transition between these two flow regimes happens in a smooth way.

Typical use and important parameters

This model is configured by setting m_flow_nominal to the mass flow rate that the valve should supply when it is completely open, i.e., y = 1. The pressure drop corresponding to this working point can be set using dpValve_nominal, or using a Kv, Cv or Av value. The parameter dpValve_fixed can be used to add additional pressure drops, although in this valve it is equivalent to add these to dpValve_nominal.

The parameter l2 represents the non-ideal leakage behaviour of this valve for high pressures. It is assumed that the mass flow rate will rise beyond the requested mass flow rate y*m_flow_nominal if dp > dpValve_nominal+dpFixed_nominal. The parameter l2 represents the slope of this rise: d(m_flow)/d(dp) = l2* m_flow_nominal/dp_nominal. In the ideal case l2=0, but this may introduce singularities, for instance when connecting this component with a fixed mass flow source.

Options

Parameter deltax sets the duration of the transition region between the two flow regimes as a fraction of dp_nominal or m_flow_nominal, depending on the value of from_dp.

Implementation

Note that the result in the transition region when using from_dp = true is not identical to the result when using from_dp = false.

Variables *_y1 and *_y2 serve a dual use. They are used to 1) compute the support points at *_x1 and *_x2, which should not depend on m_flow or dp and 2) to compute the flow functions when outside of this regime, which does depend on m_flow or dp. Min and max functions are therefore used such that one equation can serve both puroposes.

Extends from Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve (Partial model for a two way valve).

Parameters

Connectors

Modelica definition

Buildings.Fluid.Actuators.Valves.TwoWayQuickOpening

Two way valve with quick opening flow characteristics

Information

Two way valve with a power function for the valve opening characteristic. Valves that need to open quickly typically have such a valve characteristics.

This model is based on the partial valve model Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve. Check this model for more information, such as the regularization near the origin.

Extends from BaseClasses.PartialTwoWayValveKv (Partial model for a two way valve using a Kv characteristic).

Parameters

Connectors

Modelica definition

Buildings.Fluid.Actuators.Valves.TwoWayTable

Two way valve with table-specified flow characteristics

Information

Two way valve with opening characteristic that is configured through a table.

The mass flow rate for the fully open valve is determined based on the value of the parameter CvData. For the different valve positions y ∈ [0, 1], this nominal flow rate is scaled by the values of the parameter flowCharacteristics. The parameter flowCharacteristics declares a table of the form

where l = K_v(y=0)/K_v(y=1) > 0 is the valve leakage. The first row is the valve opening, and the second row is the mass flow rate, relative to the mass flow rate of the fully open valve, under the assumption of a constant pressure difference across the valve. A suggested value for the valve leakage is l=0.0001. If l = 0, then this model will replace it with l = 10^-8 for numerical reasons. For example, if a valve has K_v=0.5 [m³/h/bar^1/2] and a linear opening characteristics and a valve leakage of l=0.0001, then one would set

 CvData=Buildings.Fluid.Types.CvTypes.Kv
 Kv = 0.5
 flowCharacteristics(y={0,1}, phi={0.0001,1})
 

Note, however, that Buildings.Fluid.Actuators.Valves.TwoWayLinear provides a more efficient implementation for this simple case.

The parameter flowCharacteristics must meet the following requirements, otherwise the model stops with an error:

• Their arrays y and phi must be strictly monotonic increasing.
• The first value must satisfy y[1]=0, and phi[1] must be equal to the leakage flow rate, which must be bigger than zero. Otherwise, a default value of 1E-8 is used.
• The last values must satisfy y[end]=1 and phi[end]=1.

This model is based on the partial valve model Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve. Check this model for more information, such as the regularization near the origin.

For an example that specifies an opening characteristics, see Buildings.Fluid.Actuators.Valves.Examples.TwoWayValveTable.

Extends from BaseClasses.PartialTwoWayValveKv (Partial model for a two way valve using a Kv characteristic).

Parameters

Connectors

Modelica definition