modelTwoWayEqualPercentage
Two way valve with equal percentage flow characteristics
Extends from BaseClasses.PartialTwoWayValveKv (Partial model for a two way valve using a Kv characteristic).
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.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | homotopyInitialization (from PartialResistance) | true | = true, use homotopy method |
| Modelica.Units.SI.MassFlowRate | m_flow_turbulent (from PartialResistance) | Turbulent flow if |m_flow| >= m_flow_turbulent | |
| Real | l (from PartialTwoWayValve) | 0.0001 | Valve leakage, l=Kv(y=0)/Kv(y=1) |
| Real | kFixed (from PartialTwoWayValve) | if dpFixed_nominal > Modelica.Constants.eps then m_flow_nominal/sqrt(dpFixed_nominal) else 0 | 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 |
| Assumptions | |||
| Boolean | allowFlowReversal (from PartialTwoPort) | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Nominal condition | |||
| Modelica.Units.SI.MassFlowRate | m_flow_nominal (from PartialTwoPortInterface) | Nominal mass flow rate | |
| Modelica.Units.SI.PressureDifference | dp_nominal (from PartialResistance) | Pressure drop at nominal mass flow rate | |
| Modelica.Units.SI.PressureDifference | dpValve_nominal (from ValveParameters) | Nominal pressure drop of fully open valve, used if CvData=Buildings.Fluid.Types.CvTypes.OpPoint | |
| Modelica.Units.SI.PressureDifference | dpFixed_nominal (from PartialTwoWayValve) | 0 | Pressure drop of pipe and other resistances that are in series |
| Advanced | |||
| Modelica.Units.SI.MassFlowRate | m_flow_small (from PartialTwoPortInterface) | 1E-4*abs(m_flow_nominal) | Small mass flow rate for regularization of zero flow |
| Boolean | from_dp (from PartialResistance) | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
| Real | n (from PartialResistance) | 2 | Flow exponent, n=1 for laminar, n=2 for turbulent |
| Boolean | linearized (from PartialResistance) | false | = true, use linear relation between m_flow and dp for any flow rate |
| Advanced › Diagnostics | |||
| Boolean | show_T (from PartialTwoPortInterface) | false | = true, if actual temperature at port is computed |
| Flow Coefficient | |||
| Buildings.Fluid.Types.CvTypes | CvData (from ValveParameters) | Buildings.Fluid.Types.CvTypes.OpPoint | Selection of flow coefficient |
| Real | Kv (from ValveParameters) | Kv (metric) flow coefficient [m3/h/(bar)^(1/2)] | |
| Real | Cv (from ValveParameters) | Cv (US) flow coefficient [USG/min/(psi)^(1/2)] | |
| Modelica.Units.SI.Area | Av (from ValveParameters) | Av (metric) flow coefficient | |
| Pressure-flow linearization | |||
| Real | deltaM (from ValveParameters) | 0.02 | Fraction of nominal flow rate where linearization starts, if y=1 |
| Advanced › Nominal condition | |||
| Modelica.Units.SI.Density | rhoStd (from ValveParameters) | Inlet density for which valve coefficients are defined | |
| Dynamics › Actuator position | |||
| Boolean | use_strokeTime (from ActuatorSignal) | true | Set to true to continuously open and close valve using strokeTime |
| Modelica.Units.SI.Time | strokeTime (from ActuatorSignal) | 120 | Time needed to fully open or close actuator |
| Modelica.Blocks.Types.Init | init (from ActuatorSignal) | Modelica.Blocks.Types.Init.InitialOutput | Type of initialization (no init/steady state/initial state/initial output) |
| Real | y_start (from ActuatorSignal) | 1 | Initial position of actuator |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Fluid.Interfaces.FluidPort_a | port_a (from PartialTwoPort) | Fluid connector a (positive design flow direction is from port_a to port_b) | |
| Modelica.Fluid.Interfaces.FluidPort_b | port_b (from PartialTwoPort) | Fluid connector b (positive design flow direction is from port_a to port_b) | |
| Modelica.Blocks.Interfaces.RealInput | y (from ActuatorSignal) | Actuator position (0: closed, 1: open) | |
| Modelica.Blocks.Interfaces.RealOutput | y_actual (from ActuatorSignal) | Actual actuator position |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.MassFlowRate | m_flow (from PartialTwoPortInterface) | port_a.m_flow | Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) |
| Modelica.Units.SI.PressureDifference | dp (from PartialTwoPortInterface) | port_a.p - port_b.p | Pressure difference between port_a and port_b |
| Medium.ThermodynamicState | sta_a (from PartialTwoPortInterface) | if allowFlowReversal then Medium.setState_phX(port_a.p, noEvent(actualStream(port_a.h_outflow)), noEvent(actualStream(port_a.Xi_outflow))) else Medium.setState_phX(port_a.p, noEvent(inStream(port_a.h_outflow)), noEvent(inStream(port_a.Xi_outflow))) | Medium properties in port_a |
| Medium.ThermodynamicState | sta_b (from PartialTwoPortInterface) | if allowFlowReversal then Medium.setState_phX(port_b.p, noEvent(actualStream(port_b.h_outflow)), noEvent(actualStream(port_b.Xi_outflow))) else Medium.setState_phX(port_b.p, noEvent(port_b.h_outflow), noEvent(port_b.Xi_outflow)) | Medium properties in port_b |
| Real | phi (from PartialTwoWayValve) | Ratio actual to nominal mass flow rate of valve, phi=Kv(y)/Kv(y=1) | |
| Real | kVal (from PartialTwoWayValve) | Flow coefficient of valve, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2). | |
| Real | k (from PartialTwoWayValve) | Flow coefficient of valve and pipe in series, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2). |
Revisions
-
June 10, 2021, by Michael Wetter:
Changed implementation of the filter and changed the parameterorderto a constant as most users need not change this value.
This is for #1498. -
August 7, 2020, by Ettore Zanetti:
changed the computation ofphiusingmax(0.1*l, . )to avoid phi=0. See issue 1376. -
February 21, 2020, by Michael Wetter:
Changed icon to display its operating state.
This is for #1294. -
November 9, 2019, by Filip Jorissen:
Guarded the computation ofphiusingmax(0, . )to avoid negative phi. See issue 1223. -
April 4, 2014, by Michael Wetter:
Moved the assignment of the flow functionphito the model instantiation because in its base class, the keywordinputhas been added to the variablephi. -
March 27, 2014 by Michael Wetter:
Revised model for implementation of new valve model that computes the flow function based on a table. -
February 20, 2012 by Michael Wetter:
Renamed parameterdp_nominaltodpValve_nominal, and added new parameterdpFixed_nominal. See Buildings.Fluid.Actuators.UsersGuide. -
February 14, 2012 by Michael Wetter:
Added filter to approximate the travel time of the actuator. -
March 25, 2011, by Michael Wetter:
Added homotopy method. -
June 5, 2008 by Michael Wetter:
First implementation.