modelPartialThreeWayValve

Partial three way valve

Extends from IBPSA.Fluid.BaseClasses.PartialThreeWayResistance (Flow splitter with partial resistance model at each port), IBPSA.Fluid.Actuators.BaseClasses.ActuatorSignal (Partial model that implements the filtered opening for valves and dampers), IBPSA.Fluid.Actuators.BaseClasses.ValveParameters (Model with parameters for valves).

Information

Partial model of a three way valve. This is the base model for valves with different opening characteristics, such as linear, equal percentage or quick opening. The three way valve model consists of a mixer where valves are placed in two of the flow legs. The third flow leg has no friction. The flow coefficient Kv for flow from port_1 → port_2 is a parameter. The flow coefficient for the bypass flow from port_3 → port_2 is computed as

         Kv(port_3 → port_2)
  fraK = ----------------------
         Kv(port_1 → port_2)

where 0 < fraK ≤ 1 is a parameter with a default value of fraK=0.7.

Since this model uses two way valves to construct a three way valve, see IBPSA.Fluid.Actuators.BaseClasses.PartialTwoWayValve for details regarding the valve implementation.

Parameters

Type	Name	Default	Description
Real	fraK	0.7	Fraction Kv(port_3→port_2)/Kv(port_1→port_2)
Real	l	{0.0001, 0.0001}	Valve leakage, l=Kv(y=0)/Kv(y=1)
Dynamics › Equations
Modelica.Fluid.Types.Dynamics	energyDynamics (from LumpedVolumeDeclarations)	Modelica.Fluid.Types.Dynamics.DynamicFreeInitial	Type of energy balance: dynamic (3 initialization options) or steady state
Modelica.Fluid.Types.Dynamics	massDynamics (from LumpedVolumeDeclarations)	energyDynamics	Type of mass balance: dynamic (3 initialization options) or steady state
Modelica.Fluid.Types.Dynamics	substanceDynamics (from LumpedVolumeDeclarations)	energyDynamics	Type of independent mass fraction balance: dynamic (3 initialization options) or steady state
Modelica.Fluid.Types.Dynamics	traceDynamics (from LumpedVolumeDeclarations)	energyDynamics	Type of trace substance balance: dynamic (3 initialization options) or steady state
Modelica.SIunits.MassFlowRate	mDyn_flow_nominal (from PartialThreeWayResistance)		Nominal mass flow rate for dynamic momentum and energy balance
Initialization
Medium.AbsolutePressure	p_start (from LumpedVolumeDeclarations)	Medium.p_default	Start value of pressure
Medium.Temperature	T_start (from LumpedVolumeDeclarations)	Medium.T_default	Start value of temperature
Medium.MassFraction[Medium.nX]	X_start (from LumpedVolumeDeclarations)	Medium.X_default	Start value of mass fractions m_i/m
Medium.ExtraProperty[Medium.nC]	C_start (from LumpedVolumeDeclarations)	fill(0, Medium.nC)	Start value of trace substances
Medium.ExtraProperty[Medium.nC]	C_nominal (from LumpedVolumeDeclarations)	fill(1E-2, Medium.nC)	Nominal value of trace substances. (Set to typical order of magnitude.)
Dynamics
Real	mSenFac (from LumpedVolumeDeclarations)	1	Factor for scaling the sensible thermal mass of the volume
Dynamics › Nominal condition
Modelica.SIunits.Time	tau (from PartialThreeWayResistance)	10	Time constant at nominal flow for dynamic energy and momentum balance
Advanced
Boolean	from_dp (from PartialThreeWayResistance)	true	= true, use m_flow = f(dp) else dp = f(m_flow)
Modelica.Fluid.Types.PortFlowDirection	portFlowDirection_1 (from PartialThreeWayResistance)	Modelica.Fluid.Types.PortFlowDirection.Bidirectional	Flow direction for port_1
Modelica.Fluid.Types.PortFlowDirection	portFlowDirection_2 (from PartialThreeWayResistance)	Modelica.Fluid.Types.PortFlowDirection.Bidirectional	Flow direction for port_2
Modelica.Fluid.Types.PortFlowDirection	portFlowDirection_3 (from PartialThreeWayResistance)	Modelica.Fluid.Types.PortFlowDirection.Bidirectional	Flow direction for port_3
Boolean	verifyFlowReversal (from PartialThreeWayResistance)	false	=true, to assert that the flow does not reverse when portFlowDirection_* does not equal Bidirectional
Modelica.SIunits.MassFlowRate	m_flow_small (from PartialThreeWayResistance)		Small mass flow rate for checking flow reversal
Boolean	linearized	{false, false}	= true, use linear relation between m_flow and dp for any flow rate
Boolean	homotopyInitialization	true	= true, use homotopy method
Dynamics › Filtered opening
Boolean	use_inputFilter (from ActuatorSignal)	true	= true, if opening is filtered with a 2nd order CriticalDamping filter
Modelica.SIunits.Time	riseTime (from ActuatorSignal)	120	Rise time of the filter (time to reach 99.6 % of an opening step)
Integer	order (from ActuatorSignal)	2	Order of filter
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 value of output
Flow Coefficient
IBPSA.Fluid.Types.CvTypes	CvData (from ValveParameters)	IBPSA.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.SIunits.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
Nominal condition
Modelica.SIunits.MassFlowRate	m_flow_nominal (from ValveParameters)		Nominal mass flow rate
Modelica.SIunits.PressureDifference	dpValve_nominal (from ValveParameters)		Nominal pressure drop of fully open valve, used if CvData=IBPSA.Fluid.Types.CvTypes.OpPoint
Modelica.SIunits.PressureDifference[2]	dpFixed_nominal	{0, 0}	Nominal pressure drop of pipes and other equipment in flow legs at port_1 and port_3
Advanced › Nominal condition
Modelica.SIunits.Density	rhoStd (from ValveParameters)		Inlet density for which valve coefficients are defined

Connectors

Type	Name	Description
Modelica.Fluid.Interfaces.FluidPort_a	port_1 (from PartialThreeWayResistance)	First port, typically inlet
Modelica.Fluid.Interfaces.FluidPort_b	port_2 (from PartialThreeWayResistance)	Second port, typically outlet
Modelica.Fluid.Interfaces.FluidPort_a	port_3 (from PartialThreeWayResistance)	Third port, can be either inlet or outlet
Modelica.Blocks.Interfaces.RealInput	y (from ActuatorSignal)	Actuator position (0: closed, 1: open)
Modelica.Blocks.Interfaces.RealOutput	y_actual (from ActuatorSignal)	Actual valve position

Components

Type	Name	Description
IBPSA.Fluid.Interfaces.PartialTwoPortInterface	res1 (from PartialThreeWayResistance)
IBPSA.Fluid.Interfaces.PartialTwoPortInterface	res2 (from PartialThreeWayResistance)
IBPSA.Fluid.Interfaces.PartialTwoPortInterface	res3 (from PartialThreeWayResistance)
IBPSA.Fluid.Delays.DelayFirstOrder	vol (from PartialThreeWayResistance)	Fluid volume to break algebraic loop

Revisions

March 24, 2017, by Michael Wetter:
Renamed filteredInput to use_inputFilter.
This is for #665.
January 22, 2016, by Michael Wetter:
Corrected type declaration of pressure difference. This is for #404.
December 17, 2015, by Michael Wetter:
Removed assignment redeclare final package Medium=Medium as this is now done in the base class. This is for https://github.com/lbl-srg/modelica-buildings/issues/475.
November 23, 2015 by Filip Jorissen:
Corrected valve leakage value to avoid warnings.
February 28, 2013, by Michael Wetter:
Reformulated assignment of parameters. Removed default value for dpValve_nominal, as this parameter has the attribute fixed=false for some values of CvData. In this case, assigning a value is not allowed. Corrected wrong documentation of parameter fraK(min=0, max=1) = 0.7. The documenation was Fraction Kv(port_1→port_2)/Kv(port_3→port_2) instead of Fraction Kv(port_3→port_2)/Kv(port_1→port_2). Because the parameter set correctly its attributes min=0 and max=1, instances of this model used the correct value.
April 12, 2012 by Michael Wetter:
Removed duplicate declaration of m_flow_nominal.
February 20, 2012 by Michael Wetter:
Renamed parameter dp_nominal to dpValve_nominal, and added new parameter dpFixed_nominal=0. See IBPSA.Fluid.Actuators.UsersGuide.
March 25, 2011, by Michael Wetter:
Added homotopy method.
June 3, 2008 by Michael Wetter:
First implementation.