Buildings.Fluid.Actuators.Valves
Package with valve models
Information
This package contains component models for two- and three-way valves. For motor models, see Buildings.Fluid.Actuators.Motors.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 |
 TwoWayEqualPercentage
|
Two way valve with equal percentage flow characteristics |
| TwoWayLinear
|
Two way valve with linear flow characteristics |
| 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
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Real | fraK | 0.7 | Fraction Kv(port_3→port_2)/Kv(port_1→port_2) |
| Real | l[2] | {0.0001,0.0001} | Valve leakage, l=Kv(y=0)/Kv(y=1) |
| Real | R | 50 | Rangeability, R=50...100 typically |
| Real | delta0 | 0.01 | Range of significant deviation from equal percentage law |
| Flow Coefficient | |||
| CvTypes | CvData | Buildings.Fluid.Types.CvType... | Selection of flow coefficient |
| Real | Kv | Kv (metric) flow coefficient [m3/h/(bar)^(1/2)] | |
| Real | Cv | Cv (US) flow coefficient [USG/min/(psi)^(1/2)] | |
| Area | Av | Av (metric) flow coefficient [m2] | |
| Pressure-flow linearization | |||
| Real | deltaM | 0.02 | Fraction of nominal flow rate where linearization starts, if y=1 |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| PressureDifference | dpValve_nominal | Nominal pressure drop of fully open valve, used if CvData=Buildings.Fluid.Types.CvTypes.OpPoint [Pa] | |
| PressureDifference | dpFixed_nominal[2] | {0,0} | Nominal pressure drop of pipes and other equipment in flow legs at port_1 and port_3 [Pa] |
| Dynamics | |||
| Equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
| Dynamics | massDynamics | energyDynamics | Type of mass balance: dynamic (3 initialization options) or steady state |
| Nominal condition | |||
| Time | tau | 10 | Time constant at nominal flow for dynamic energy and momentum balance [s] |
| Filtered opening | |||
| Boolean | use_inputFilter | true | = true, if opening is filtered with a 2nd order CriticalDamping filter |
| Time | riseTime | 120 | Rise time of the filter (time to reach 99.6 % of an opening step) [s] |
| Init | init | Modelica.Blocks.Types.Init.I... | Type of initialization (no init/steady state/initial state/initial output) |
| Real | y_start | 1 | Initial value of output |
| Initialization | |||
| AbsolutePressure | p_start | Medium.p_default | Start value of pressure [Pa] |
| Temperature | T_start | Medium.T_default | Start value of temperature [K] |
| 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 |
| ExtraProperty | C_nominal[Medium.nC] | fill(1E-2, Medium.nC) | Nominal value of trace substances. (Set to typical order of magnitude.) |
| Advanced | |||
| Boolean | from_dp | true | = true, use m_flow = f(dp) else dp = f(m_flow) |
| PortFlowDirection | portFlowDirection_1 | Modelica.Fluid.Types.PortFlo... | Flow direction for port_1 |
| PortFlowDirection | portFlowDirection_2 | Modelica.Fluid.Types.PortFlo... | Flow direction for port_2 |
| PortFlowDirection | portFlowDirection_3 | Modelica.Fluid.Types.PortFlo... | Flow direction for port_3 |
| Boolean | linearized[2] | {false,false} | = true, use linear relation between m_flow and dp for any flow rate |
| Boolean | homotopyInitialization | true | = true, use homotopy method |
| Nominal condition | |||
| Density | rhoStd | Medium.density_pTX(101325, 2... | Inlet density for which valve coefficients are defined [kg/m3] |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPort_a | port_1 | First port, typically inlet |
| FluidPort_b | port_2 | Second port, typically outlet |
| FluidPort_a | port_3 | Third port, can be either inlet or outlet |
| input RealInput | y | Actuator position (0: closed, 1: open) |
| output RealOutput | y_actual | Actual valve position |
Modelica definition
model ThreeWayEqualPercentageLinear
"Three way valve with equal percentage and linear characteristics"
extends BaseClasses.PartialThreeWayValve(redeclare TwoWayEqualPercentage res1
(R=R, delta0=delta0), redeclare TwoWayLinear res3);
parameter Real R=50 "Rangeability, R=50...100 typically";
parameter Real delta0=0.01
"Range of significant deviation from equal percentage law";
equation
connect(inv.y, res3.y);
connect(y_actual, inv.u2);
connect(y_actual, res1.y);
end ThreeWayEqualPercentageLinear;
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
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Real | fraK | 0.7 | Fraction Kv(port_3→port_2)/Kv(port_1→port_2) |
| Real | l[2] | {0.0001,0.0001} | Valve leakage, l=Kv(y=0)/Kv(y=1) |
| Flow Coefficient | |||
| CvTypes | CvData | Buildings.Fluid.Types.CvType... | Selection of flow coefficient |
| Real | Kv | Kv (metric) flow coefficient [m3/h/(bar)^(1/2)] | |
| Real | Cv | Cv (US) flow coefficient [USG/min/(psi)^(1/2)] | |
| Area | Av | Av (metric) flow coefficient [m2] | |
| Pressure-flow linearization | |||
| Real | deltaM | 0.02 | Fraction of nominal flow rate where linearization starts, if y=1 |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| PressureDifference | dpValve_nominal | Nominal pressure drop of fully open valve, used if CvData=Buildings.Fluid.Types.CvTypes.OpPoint [Pa] | |
| PressureDifference | dpFixed_nominal[2] | {0,0} | Nominal pressure drop of pipes and other equipment in flow legs at port_1 and port_3 [Pa] |
| Dynamics | |||
| Equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
| Dynamics | massDynamics | energyDynamics | Type of mass balance: dynamic (3 initialization options) or steady state |
| Nominal condition | |||
| Time | tau | 10 | Time constant at nominal flow for dynamic energy and momentum balance [s] |
| Filtered opening | |||
| Boolean | use_inputFilter | true | = true, if opening is filtered with a 2nd order CriticalDamping filter |
| Time | riseTime | 120 | Rise time of the filter (time to reach 99.6 % of an opening step) [s] |
| Init | init | Modelica.Blocks.Types.Init.I... | Type of initialization (no init/steady state/initial state/initial output) |
| Real | y_start | 1 | Initial value of output |
| Initialization | |||
| AbsolutePressure | p_start | Medium.p_default | Start value of pressure [Pa] |
| Temperature | T_start | Medium.T_default | Start value of temperature [K] |
| 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 |
| ExtraProperty | C_nominal[Medium.nC] | fill(1E-2, Medium.nC) | Nominal value of trace substances. (Set to typical order of magnitude.) |
| Advanced | |||
| Boolean | from_dp | true | = true, use m_flow = f(dp) else dp = f(m_flow) |
| PortFlowDirection | portFlowDirection_1 | Modelica.Fluid.Types.PortFlo... | Flow direction for port_1 |
| PortFlowDirection | portFlowDirection_2 | Modelica.Fluid.Types.PortFlo... | Flow direction for port_2 |
| PortFlowDirection | portFlowDirection_3 | Modelica.Fluid.Types.PortFlo... | Flow direction for port_3 |
| Boolean | linearized[2] | {false,false} | = true, use linear relation between m_flow and dp for any flow rate |
| Boolean | homotopyInitialization | true | = true, use homotopy method |
| Nominal condition | |||
| Density | rhoStd | Medium.density_pTX(101325, 2... | Inlet density for which valve coefficients are defined [kg/m3] |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPort_a | port_1 | First port, typically inlet |
| FluidPort_b | port_2 | Second port, typically outlet |
| FluidPort_a | port_3 | Third port, can be either inlet or outlet |
| input RealInput | y | Actuator position (0: closed, 1: open) |
| output RealOutput | y_actual | Actual valve position |
Modelica definition
model ThreeWayLinear "Three way valve with linear characteristics"
extends BaseClasses.PartialThreeWayValve(redeclare TwoWayLinear res1,
redeclare TwoWayLinear res3);
equation
connect(inv.y, res3.y);
connect(y_actual, inv.u2);
connect(y_actual, res1.y);
end ThreeWayLinear;
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
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Real | l | 0.0001 | Valve leakage, l=Kv(y=0)/Kv(y=1) |
| Real | phi | if homotopyInitialization th... | Ratio actual to nominal mass flow rate of valve, phi=Kv(y)/Kv(y=1) |
| Real | kFixed | if dpFixed_nominal > Modelic... | Flow coefficient of fixed resistance that may be in series with valve, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2). |
| Real | R | 50 | Rangeability, R=50...100 typically |
| Real | delta0 | 0.01 | Range of significant deviation from equal percentage law |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| PressureDifference | dpValve_nominal | Nominal pressure drop of fully open valve, used if CvData=Buildings.Fluid.Types.CvTypes.OpPoint [Pa] | |
| PressureDifference | dpFixed_nominal | 0 | Pressure drop of pipe and other resistances that are in series [Pa] |
| Flow Coefficient | |||
| CvTypes | CvData | Buildings.Fluid.Types.CvType... | Selection of flow coefficient |
| Real | Kv | Kv (metric) flow coefficient [m3/h/(bar)^(1/2)] | |
| Real | Cv | Cv (US) flow coefficient [USG/min/(psi)^(1/2)] | |
| Area | Av | Av (metric) flow coefficient [m2] | |
| Pressure-flow linearization | |||
| Real | deltaM | 0.02 | Fraction of nominal flow rate where linearization starts, if y=1 |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Advanced | |||
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | homotopyInitialization | true | = true, use homotopy method |
| Boolean | linearized | false | = true, use linear relation between m_flow and dp for any flow rate |
| Nominal condition | |||
| Density | rhoStd | Medium.density_pTX(101325, 2... | Inlet density for which valve coefficients are defined [kg/m3] |
| Dynamics | |||
| Filtered opening | |||
| Boolean | use_inputFilter | true | = true, if opening is filtered with a 2nd order CriticalDamping filter |
| Time | riseTime | 120 | Rise time of the filter (time to reach 99.6 % of an opening step) [s] |
| Init | init | Modelica.Blocks.Types.Init.I... | Type of initialization (no init/steady state/initial state/initial output) |
| Real | y_start | 1 | Initial value of output |
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 | y | Actuator position (0: closed, 1: open) |
| output RealOutput | y_actual | Actual valve position |
Modelica definition
model TwoWayEqualPercentage
"Two way valve with equal percentage flow characteristics"
extends BaseClasses.PartialTwoWayValveKv(phi=if homotopyInitialization then
homotopy(actual=Buildings.Fluid.Actuators.BaseClasses.equalPercentage(
y_actual,
R,
l,
delta0), simplified=l + y_actual*(1 - l)) else
Buildings.Fluid.Actuators.BaseClasses.equalPercentage(
y_actual,
R,
l,
delta0));
parameter Real R=50 "Rangeability, R=50...100 typically";
parameter Real delta0=0.01
"Range of significant deviation from equal percentage law";
initial equation
// Since the flow model Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow computes
// 1/k^2, the parameter l must not be zero.
assert(l > 0, "Valve leakage parameter l must be bigger than zero.");
assert(l < 1/R, "Wrong parameters in valve model.\n" + " Rangeability R = " +
String(R) + "\n" + " Leakage flow l = " + String(l) + "\n" + " Must have l < 1/R = "
+ String(1/R));
end TwoWayEqualPercentage;
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
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Real | l | 0.0001 | Valve leakage, l=Kv(y=0)/Kv(y=1) |
| Real | phi | l + y_actual*(1 - l) | Ratio actual to nominal mass flow rate of valve, phi=Kv(y)/Kv(y=1) |
| Real | kFixed | if dpFixed_nominal > Modelic... | Flow coefficient of fixed resistance that may be in series with valve, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2). |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| PressureDifference | dpValve_nominal | Nominal pressure drop of fully open valve, used if CvData=Buildings.Fluid.Types.CvTypes.OpPoint [Pa] | |
| PressureDifference | dpFixed_nominal | 0 | Pressure drop of pipe and other resistances that are in series [Pa] |
| Flow Coefficient | |||
| CvTypes | CvData | Buildings.Fluid.Types.CvType... | Selection of flow coefficient |
| Real | Kv | Kv (metric) flow coefficient [m3/h/(bar)^(1/2)] | |
| Real | Cv | Cv (US) flow coefficient [USG/min/(psi)^(1/2)] | |
| Area | Av | Av (metric) flow coefficient [m2] | |
| Pressure-flow linearization | |||
| Real | deltaM | 0.02 | Fraction of nominal flow rate where linearization starts, if y=1 |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Advanced | |||
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | homotopyInitialization | true | = true, use homotopy method |
| Boolean | linearized | false | = true, use linear relation between m_flow and dp for any flow rate |
| Nominal condition | |||
| Density | rhoStd | Medium.density_pTX(101325, 2... | Inlet density for which valve coefficients are defined [kg/m3] |
| Dynamics | |||
| Filtered opening | |||
| Boolean | use_inputFilter | true | = true, if opening is filtered with a 2nd order CriticalDamping filter |
| Time | riseTime | 120 | Rise time of the filter (time to reach 99.6 % of an opening step) [s] |
| Init | init | Modelica.Blocks.Types.Init.I... | Type of initialization (no init/steady state/initial state/initial output) |
| Real | y_start | 1 | Initial value of output |
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 | y | Actuator position (0: closed, 1: open) |
| output RealOutput | y_actual | Actual valve position |
Modelica definition
model TwoWayLinear "Two way valve with linear flow characteristics"
extends BaseClasses.PartialTwoWayValveKv(phi=l + y_actual*(1 - l));
initial equation
// Since the flow model Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow computes
// 1/k^2, the parameter l must not be zero.
assert(l > 0, "Valve leakage parameter l must be bigger than zero.");
end TwoWayLinear;
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
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Real | l | 0.0001 | Valve leakage, l=Kv(y=0)/Kv(y=1) |
| Real | phi | l + y_actual*(1 - l) | Ratio actual to nominal mass flow rate of valve, phi=Kv(y)/Kv(y=1) |
| Real | kFixed | if dpFixed_nominal > Modelic... | Flow coefficient of fixed resistance that may be in series with valve, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2). |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| PressureDifference | dpValve_nominal | Nominal pressure drop of fully open valve, used if CvData=Buildings.Fluid.Types.CvTypes.OpPoint [Pa] | |
| PressureDifference | dpFixed_nominal | 0 | Pressure drop of pipe and other resistances that are in series [Pa] |
| Flow Coefficient | |||
| CvTypes | CvData | Buildings.Fluid.Types.CvType... | Selection of flow coefficient |
| Real | Kv | Kv (metric) flow coefficient [m3/h/(bar)^(1/2)] | |
| Real | Cv | Cv (US) flow coefficient [USG/min/(psi)^(1/2)] | |
| Area | Av | Av (metric) flow coefficient [m2] | |
| Pressure-flow linearization | |||
| Real | deltaM | 0.02 | Fraction of nominal flow rate where linearization starts, if y=1 |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Advanced | |||
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Boolean | from_dp | true | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | homotopyInitialization | true | = true, use homotopy method |
| Boolean | linearized | false | = true, use linear relation between m_flow and dp for any flow rate |
| Real | l2 | 0.01 | Gain for mass flow increase if pressure is above nominal pressure |
| Real | deltax | 0.02 | Transition interval for flow rate |
| Nominal condition | |||
| Density | rhoStd | Medium.density_pTX(101325, 2... | Inlet density for which valve coefficients are defined [kg/m3] |
| Dynamics | |||
| Filtered opening | |||
| Boolean | use_inputFilter | true | = true, if opening is filtered with a 2nd order CriticalDamping filter |
| Time | riseTime | 120 | Rise time of the filter (time to reach 99.6 % of an opening step) [s] |
| Init | init | Modelica.Blocks.Types.Init.I... | Type of initialization (no init/steady state/initial state/initial output) |
| Real | y_start | 1 | Initial value of output |
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 | y | Actuator position (0: closed, 1: open) |
| output RealOutput | y_actual | Actual valve position |
Modelica definition
model TwoWayPressureIndependent
"Model of a pressure-independent two way valve"
extends Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve(
final linearized=false,
from_dp=true,
phi=l + y_actual*(1 - l));
parameter Real l2(min=1e-10) = 0.01
"Gain for mass flow increase if pressure is above nominal pressure";
parameter Real deltax=0.02 "Transition interval for flow rate";
protected
parameter Real coeff1=l2/dp_nominal*m_flow_nominal
"Parameter for avoiding unnecessary computations";
parameter Real coeff2=1/coeff1
"Parameter for avoiding unnecessary computations";
constant Real y2dd=0 "Second derivative at second support point";
Modelica.SIunits.MassFlowRate m_flow_set "Requested mass flow rate";
Modelica.SIunits.PressureDifference dp_min(displayUnit="Pa")
"Minimum pressure difference required for delivering requested mass flow rate";
Modelica.SIunits.PressureDifference dp_x, dp_x1, dp_x2, dp_y2, dp_y1
"Support points for interpolation flow functions";
Modelica.SIunits.MassFlowRate m_flow_x, m_flow_x1, m_flow_x2, m_flow_y2,
m_flow_y1 "Support points for interpolation flow functions";
Modelica.SIunits.MassFlowRate m_flow_smooth
"Smooth interpolation result between two flow regimes";
Modelica.SIunits.PressureDifference dp_smooth
"Smooth interpolation result between two flow regimes";
equation
m_flow_set = m_flow_nominal*phi;
kVal = Kv_SI;
if (dpFixed_nominal > Modelica.Constants.eps) then
k = sqrt(1/(1/kFixed^2 + 1/kVal^2));
else
k = kVal;
end if;
dp_min = Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow(
m_flow=m_flow_set,
k=k,
m_flow_turbulent=m_flow_turbulent);
if from_dp then
m_flow_x = 0;
m_flow_x1 = 0;
m_flow_x2 = 0;
dp_y1 = 0;
dp_y2 = 0;
dp_smooth = 0;
dp_x = dp - dp_min;
dp_x1 = -dp_x2;
dp_x2 = deltax*dp_min;
// min function ensures that m_flow_y1 does not increase further for dp_x > dp_x1
m_flow_y1 = Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp(
dp=min(dp, dp_min + dp_x1),
k=k,
m_flow_turbulent=m_flow_turbulent);
// max function ensures that m_flow_y2 does not decrease further for dp_x < dp_x2
m_flow_y2 = m_flow_set + coeff1*max(dp_x, dp_x2);
m_flow_smooth = noEvent(smooth(2, if dp_x <= dp_x1 then m_flow_y1 elseif
dp_x >= dp_x2 then m_flow_y2 else
Buildings.Utilities.Math.Functions.quinticHermite(
x=dp_x,
x1=dp_x1,
x2=dp_x2,
y1=m_flow_y1,
y2=m_flow_y2,
y1d=Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp_der(
dp=dp_min + dp_x1,
k=k,
m_flow_turbulent=m_flow_turbulent,
dp_der=1),
y2d=coeff1,
y1dd=Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp_der2(
dp=dp_min + dp_x1,
k=k,
m_flow_turbulent=m_flow_turbulent,
dp_der=1,
dp_der2=0),
y2dd=y2dd)));
else
dp_x = 0;
dp_x1 = 0;
dp_x2 = 0;
m_flow_y1 = 0;
m_flow_y2 = 0;
m_flow_smooth = 0;
m_flow_x = m_flow - m_flow_set;
m_flow_x1 = -m_flow_x2;
m_flow_x2 = deltax*m_flow_set;
// min function ensures that dp_y1 does not increase further for m_flow_x > m_flow_x1
dp_y1 = Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow(
m_flow=min(m_flow, m_flow_set + m_flow_x1),
k=k,
m_flow_turbulent=m_flow_turbulent);
// max function ensures that dp_y2 does not decrease further for m_flow_x < m_flow_x2
dp_y2 = dp_min + coeff2*max(m_flow_x, m_flow_x2);
dp_smooth = noEvent(smooth(2, if m_flow_x <= m_flow_x1 then dp_y1 elseif
m_flow_x >= m_flow_x2 then dp_y2 else
Buildings.Utilities.Math.Functions.quinticHermite(
x=m_flow_x,
x1=m_flow_x1,
x2=m_flow_x2,
y1=dp_y1,
y2=dp_y2,
y1d=Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow_der(
m_flow=m_flow_set + m_flow_x1,
k=k,
m_flow_turbulent=m_flow_turbulent,
m_flow_der=1),
y2d=coeff2,
y1dd=Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow_der2
(
m_flow=m_flow_set + m_flow_x1,
k=k,
m_flow_turbulent=m_flow_turbulent,
m_flow_der=1,
m_flow_der2=0),
y2dd=y2dd)));
end if;
if homotopyInitialization then
if from_dp then
m_flow = homotopy(actual=m_flow_smooth, simplified=m_flow_nominal_pos*dp/
dp_nominal_pos);
else
dp = homotopy(actual=dp_smooth, simplified=dp_nominal_pos*m_flow/
m_flow_nominal_pos);
end if;
else
if from_dp then
m_flow = m_flow_smooth;
else
dp = dp_smooth;
end if;
end if;
end TwoWayPressureIndependent;
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
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Real | l | 0.0001 | Valve leakage, l=Kv(y=0)/Kv(y=1) |
| Real | phi | if homotopyInitialization th... | Ratio actual to nominal mass flow rate of valve, phi=Kv(y)/Kv(y=1) |
| Real | kFixed | if dpFixed_nominal > Modelic... | Flow coefficient of fixed resistance that may be in series with valve, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2). |
| Real | alp | 2 | Parameter for valve characteristics, alp>0 |
| Real | delta0 | 0.01 | Range of significant deviation from power law |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| PressureDifference | dpValve_nominal | Nominal pressure drop of fully open valve, used if CvData=Buildings.Fluid.Types.CvTypes.OpPoint [Pa] | |
| PressureDifference | dpFixed_nominal | 0 | Pressure drop of pipe and other resistances that are in series [Pa] |
| Flow Coefficient | |||
| CvTypes | CvData | Buildings.Fluid.Types.CvType... | Selection of flow coefficient |
| Real | Kv | Kv (metric) flow coefficient [m3/h/(bar)^(1/2)] | |
| Real | Cv | Cv (US) flow coefficient [USG/min/(psi)^(1/2)] | |
| Area | Av | Av (metric) flow coefficient [m2] | |
| Pressure-flow linearization | |||
| Real | deltaM | 0.02 | Fraction of nominal flow rate where linearization starts, if y=1 |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Advanced | |||
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | homotopyInitialization | true | = true, use homotopy method |
| Boolean | linearized | false | = true, use linear relation between m_flow and dp for any flow rate |
| Nominal condition | |||
| Density | rhoStd | Medium.density_pTX(101325, 2... | Inlet density for which valve coefficients are defined [kg/m3] |
| Dynamics | |||
| Filtered opening | |||
| Boolean | use_inputFilter | true | = true, if opening is filtered with a 2nd order CriticalDamping filter |
| Time | riseTime | 120 | Rise time of the filter (time to reach 99.6 % of an opening step) [s] |
| Init | init | Modelica.Blocks.Types.Init.I... | Type of initialization (no init/steady state/initial state/initial output) |
| Real | y_start | 1 | Initial value of output |
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 | y | Actuator position (0: closed, 1: open) |
| output RealOutput | y_actual | Actual valve position |
Modelica definition
model TwoWayQuickOpening
"Two way valve with quick opening flow characteristics"
extends BaseClasses.PartialTwoWayValveKv(phi=if homotopyInitialization then
homotopy(actual=l + Modelica.Fluid.Utilities.regPow(
y_actual,
alpInv,
delta0)*(1 - l), simplified=l + y_actual*(1 - l)) else l +
Modelica.Fluid.Utilities.regPow(
y_actual,
alpInv,
delta0)*(1 - l));
parameter Real alp=2 "Parameter for valve characteristics, alp>0";
parameter Real delta0=0.01 "Range of significant deviation from power law";
protected
parameter Real alpInv=1/alp "Inverse of alpha";
initial equation
// Since the flow model Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow computes
// 1/k^2, the parameter l must not be zero.
assert(l > 0, "Valve leakage parameter l must be bigger than zero.");
end TwoWayQuickOpening;
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
| y | 0 | ... | 1 |
| φ | l | ... | 1 |
where l = Kv(y=0)/Kv(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 Kv=0.5 [m3/h/bar1/2] 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:
-
The arrays in
flowCharacteristics.yandflowCharacteristics.phimust be strictly monotonic increasing. -
The first value must satisfy
flowCharacteristics.y[1]=0, andflowCharacteristics.phi[1]must be equal to the leakage flow rate, which must be bigger than zero. Otherwise, a default value of1E-8is used. -
The last values must satisfy
flowCharacteristics.y[end]=1andflowCharacteristics.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
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Real | l | phiLooUp.table[1, 2] | Valve leakage, l=Kv(y=0)/Kv(y=1) |
| Real | phi | phiLooUp.y[1] | Ratio actual to nominal mass flow rate of valve, phi=Kv(y)/Kv(y=1) |
| Real | kFixed | if dpFixed_nominal > Modelic... | Flow coefficient of fixed resistance that may be in series with valve, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2). |
| Generic | flowCharacteristics | Table with flow characteristics | |
| Nominal condition | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| PressureDifference | dpValve_nominal | Nominal pressure drop of fully open valve, used if CvData=Buildings.Fluid.Types.CvTypes.OpPoint [Pa] | |
| PressureDifference | dpFixed_nominal | 0 | Pressure drop of pipe and other resistances that are in series [Pa] |
| Flow Coefficient | |||
| CvTypes | CvData | Buildings.Fluid.Types.CvType... | Selection of flow coefficient |
| Real | Kv | Kv (metric) flow coefficient [m3/h/(bar)^(1/2)] | |
| Real | Cv | Cv (US) flow coefficient [USG/min/(psi)^(1/2)] | |
| Area | Av | Av (metric) flow coefficient [m2] | |
| Pressure-flow linearization | |||
| Real | deltaM | 0.02 | Fraction of nominal flow rate where linearization starts, if y=1 |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Advanced | |||
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
| Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Boolean | homotopyInitialization | true | = true, use homotopy method |
| Boolean | linearized | false | = true, use linear relation between m_flow and dp for any flow rate |
| Nominal condition | |||
| Density | rhoStd | Medium.density_pTX(101325, 2... | Inlet density for which valve coefficients are defined [kg/m3] |
| Dynamics | |||
| Filtered opening | |||
| Boolean | use_inputFilter | true | = true, if opening is filtered with a 2nd order CriticalDamping filter |
| Time | riseTime | 120 | Rise time of the filter (time to reach 99.6 % of an opening step) [s] |
| Init | init | Modelica.Blocks.Types.Init.I... | Type of initialization (no init/steady state/initial state/initial output) |
| Real | y_start | 1 | Initial value of output |
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 | y | Actuator position (0: closed, 1: open) |
| output RealOutput | y_actual | Actual valve position |
Modelica definition
model TwoWayTable
"Two way valve with table-specified flow characteristics"
extends BaseClasses.PartialTwoWayValveKv(phi=phiLooUp.y[1], final l=phiLooUp.table[
1, 2]);
parameter Data.Generic flowCharacteristics "Table with flow characteristics";
// Since the flow model Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow computes
// 1/k^2, the flowCharacteristics.phi[1] must not be zero.
// We therefore set a lower bound.
protected
Modelica.Blocks.Tables.CombiTable1D phiLooUp(
final tableOnFile=false,
final table=[flowCharacteristics.y, cat(
1,
{max(flowCharacteristics.phi[1], 1E-8)},
{flowCharacteristics.phi[i] for i in 2:size(flowCharacteristics.phi, 1)})],
final columns=2:2,
final smoothness=Modelica.Blocks.Types.Smoothness.ContinuousDerivative)
"Normalized mass flow rate for the given valve position under the assumption of a constant pressure";
initial equation
assert(abs(flowCharacteristics.y[1]) < Modelica.Constants.eps, "flowCharateristics.y[1] must be 0.");
assert(abs(flowCharacteristics.y[size(flowCharacteristics.y, 1)] - 1) <
Modelica.Constants.eps, "flowCharateristics.y[end] must be 1.");
assert(abs(flowCharacteristics.phi[size(flowCharacteristics.phi, 1)] - 1) <
Modelica.Constants.eps, "flowCharateristics.phi[end] must be 1.");
// Assert that the sequences are strictly monotonic increasing
assert(Buildings.Utilities.Math.Functions.isMonotonic(x=flowCharacteristics.y,
strict=true), "The values for y in flowCharacteristics must be strictly monotone increasing.");
assert(Buildings.Utilities.Math.Functions.isMonotonic(x=flowCharacteristics.phi,
strict=true), "The values for phi in flowCharacteristics must be strictly monotone increasing.");
equation
connect(phiLooUp.u[1], y_actual);
end TwoWayTable;