Buildings.Fluid.Actuators.BaseClasses

Package with base classes for Buildings.Fluid.Actuators

Information

This package contains base classes that are used to construct the models in Buildings.Fluid.Actuators.

Extends from Modelica.Icons.BasesPackage (Icon for packages containing base classes).

Package Content

Name	Description
ActuatorSignal	Partial model that implements the filtered opening for valves and dampers
PartialDamperExponential	Partial model for air dampers with exponential opening characteristics
PartialThreeWayValve	Partial three way valve
PartialTwoWayValve	Partial model for a two way valve
PartialTwoWayValveKv	Partial model for a two way valve using a Kv characteristic
ValveParameters	Model with parameters for valves
der_equalPercentage	Derivative of valve opening characteristics for equal percentage valve
equalPercentage	Valve opening characteristics for equal percentage valve
exponentialDamper	Damper opening characteristics for an exponential damper
Examples	Collection of models that illustrate model use and test models

Buildings.Fluid.Actuators.BaseClasses.ActuatorSignal

Partial model that implements the filtered opening for valves and dampers

Buildings.Fluid.Actuators.BaseClasses.ActuatorSignal

Information

This model implements the filter that is used to approximate the travel time of the actuator. Models that extend this model use the signal y_actual to obtain the current position of the actuator.

See Buildings.Fluid.Actuators.UsersGuide for a description of the filter.

Parameters

Type	Name	Default	Description
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 position of actuator

Connectors

Type	Name	Description
input RealInput	y	Actuator position (0: closed, 1: open)
output RealOutput	y_actual	Actual actuator position

Modelica definition

model ActuatorSignal "Partial model that implements the filtered opening for valves and dampers" constant Integer order(min=1) = 2 "Order of filter"; parameter Boolean use_inputFilter=true "= true, if opening is filtered with a 2nd order CriticalDamping filter"; parameter Modelica.Units.SI.Time riseTime=120 "Rise time of the filter (time to reach 99.6 % of an opening step)"; parameter Modelica.Blocks.Types.Init init=Modelica.Blocks.Types.Init.InitialOutput "Type of initialization (no init/steady state/initial state/initial output)"; parameter Real y_start=1 "Initial position of actuator"; Modelica.Blocks.Interfaces.RealInput y(min=0, max=1) "Actuator position (0: closed, 1: open)"; Modelica.Blocks.Interfaces.RealOutput y_actual "Actual actuator position"; // Classes used to implement the filtered opening protected final parameter Modelica.Units.SI.Frequency fCut=5/(2*Modelica.Constants.pi* riseTime) "Cut-off frequency of filter"; parameter Boolean casePreInd = false "In case of PressureIndependent the model I/O is modified"; Modelica.Blocks.Interfaces.RealOutput y_internal(unit="1") "Output connector for internal use (= y_actual if not casePreInd)"; Modelica.Blocks.Interfaces.RealOutput y_filtered if use_inputFilter "Filtered valve position in the range 0..1"; Buildings.Fluid.BaseClasses.ActuatorFilter filter( final n=order, final f=fCut, final normalized=true, final initType=init, final y_start=y_start) if use_inputFilter "Second order filter to approximate actuator opening time, and to improve numerics"; equation connect(filter.y, y_filtered); if use_inputFilter then connect(y, filter.u); connect(filter.y, y_internal); else connect(y, y_internal); end if; if not casePreInd then connect(y_internal, y_actual); end if; end ActuatorSignal;

Buildings.Fluid.Actuators.BaseClasses.PartialDamperExponential

Partial model for air dampers with exponential opening characteristics

Buildings.Fluid.Actuators.BaseClasses.PartialDamperExponential

Information

Partial model for air dampers with exponential opening characteristics. This is the base model for air dampers. The model implements the functions that relate the opening signal and the flow coefficient. The model also defines parameters that are used by different air damper models.

The model is as in ASHRAE 825-RP except that a control signal of y=0 means the damper is closed, and y=1 means the damper is open. This is opposite of the implementation of ASHRAE 825-RP, but used here for consistency within this library.

For yL < y < yU, the damper characteristics is:

k_d(y) = exp(a+b (1-y))

where kd is the loss coefficient (total pressure drop divided by dynamic pressure) and y is the fractional opening.

Outside this range, the damper characteristics is defined by a quadratic polynomial that matches the damper resistance at y=0 and y=yL or y=yU and y=1, respectively. In addition, the polynomials are such that k_d(y) is differentiable in y and the derivative is continuous.

The damper characteristics is then used to compute the flow coefficient k(y) as:

k(y) = (2 ρ ⁄ k_d(y))^1/2 A

where A is the face area, which is computed using the nominal mass flow rate m_flow_nominal, the nominal velocity v_nominal and the density of the medium.

ASHRAE 825-RP lists the following parameter values as typical (note that the default values in the model correspond to opposed blades).

	opposed blades	single blades
yL	15/90	15/90
yU	55/90	65/90
k1	0.2 to 0.5	0.2 to 0.5
a	-1.51	-1.51
b	0.105*90	0.0842*90

(The loss coefficient in fully closed position k0 is computed based on the leakage coefficient and the coefficient in fully open position.)

References

P. Haves, L. K. Norford, M. DeSimone and L. Mei, A Standard Simulation Testbed for the Evaluation of Control Algorithms & Strategies, ASHRAE Final Report 825-RP, Atlanta, GA.

Extends from Buildings.Fluid.BaseClasses.PartialResistance (Partial model for a hydraulic resistance), Buildings.Fluid.Actuators.BaseClasses.ActuatorSignal (Partial model that implements the filtered opening for valves and dampers).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
MassFlowRate	m_flow_turbulent	if use_deltaM then deltaM*m_...	Turbulent flow if \|m_flow\| >= m_flow_turbulent [kg/s]
Boolean	use_deltaM	true	Set to true to use deltaM for turbulent transition, else ReC is used
Real	deltaM	0.3	Fraction of nominal mass flow rate where transition to turbulent occurs
Boolean	roundDuct	false	Set to true for round duct, false for square cross section
Real	ReC	4000	Reynolds number where transition to turbulence starts
Nominal condition
MassFlowRate	m_flow_nominal		Nominal mass flow rate [kg/s]
PressureDifference	dp_nominal	dpDamper_nominal + dpFixed_n...	Pressure drop at nominal mass flow rate [Pa]
PressureDifference	dpDamper_nominal		Pressure drop of fully open damper at nominal mass flow rate [Pa]
PressureDifference	dpFixed_nominal	0	Pressure drop of duct and resistances other than the damper in series, at nominal mass flow rate [Pa]
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	linearized	false	= true, use linear relation between m_flow and dp for any flow rate
Boolean	use_constant_density	true	Set to true to use constant density for flow friction
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 position of actuator
Damper coefficients
Real	a	-1.51	Coefficient a for damper characteristics [1]
Real	b	0.105*90	Coefficient b for damper characteristics [1]
Real	yL	15/90	Lower value for damper curve [1]
Real	yU	55/90	Upper value for damper curve [1]
Real	k1	0.45	Loss coefficient for y=1 (pressure drop divided by dynamic pressure) [1]
Real	l	0.0001	Damper leakage, ratio of flow coefficients k(y=0)/k(y=1)

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 actuator position

Modelica definition

partial model PartialDamperExponential "Partial model for air dampers with exponential opening characteristics" extends Buildings.Fluid.BaseClasses.PartialResistance( final dp_nominal=dpDamper_nominal+dpFixed_nominal, final m_flow_turbulent=if use_deltaM then deltaM * m_flow_nominal else eta_default*ReC*sqrt(A)*facRouDuc); extends Buildings.Fluid.Actuators.BaseClasses.ActuatorSignal; parameter Modelica.Units.SI.PressureDifference dpDamper_nominal(displayUnit= "Pa") "Pressure drop of fully open damper at nominal mass flow rate"; parameter Modelica.Units.SI.PressureDifference dpFixed_nominal(displayUnit= "Pa") = 0 "Pressure drop of duct and resistances other than the damper in series, at nominal mass flow rate"; parameter Boolean use_deltaM = true "Set to true to use deltaM for turbulent transition, else ReC is used"; parameter Real deltaM = 0.3 "Fraction of nominal mass flow rate where transition to turbulent occurs"; final parameter Modelica.Units.SI.Velocity v_nominal=(2/rho_default/k1* dpDamper_nominal)^0.5 "Nominal face velocity"; final parameter Modelica.Units.SI.Area A=m_flow_nominal/rho_default/v_nominal "Face area"; parameter Boolean roundDuct = false "Set to true for round duct, false for square cross section"; parameter Real ReC=4000 "Reynolds number where transition to turbulence starts"; parameter Real a(unit="1")=-1.51 "Coefficient a for damper characteristics"; parameter Real b(unit="1")=0.105*90 "Coefficient b for damper characteristics"; parameter Real yL(unit="1") = 15/90 "Lower value for damper curve"; parameter Real yU(unit="1") = 55/90 "Upper value for damper curve"; final parameter Real k0(min=0, unit="1") = 2 * rho_default * (A / kDamMin)^2 "Loss coefficient for y=0 (pressure drop divided by dynamic pressure)"; parameter Real k1(min=0, unit="1") = 0.45 "Loss coefficient for y=1 (pressure drop divided by dynamic pressure)"; parameter Real l(min=1e-10, max=1) = 0.0001 "Damper leakage, ratio of flow coefficients k(y=0)/k(y=1)"; parameter Boolean use_constant_density=true "Set to true to use constant density for flow friction"; Medium.Density rho "Medium density"; final parameter Real kFixed = if dpFixed_nominal > Modelica.Constants.eps then m_flow_nominal / sqrt(dpFixed_nominal) else Modelica.Constants.inf "Flow coefficient of fixed resistance that may be in series with damper, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2)."; Real kDam "Flow coefficient of damper, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2)"; Real k "Flow coefficient of damper plus fixed resistance, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2)"; protected parameter Medium.Density rho_default=Medium.density(sta_default) "Density, used to compute fluid volume"; parameter Real facRouDuc= if roundDuct then sqrt(Modelica.Constants.pi)/2 else 1 "Shape factor used to compute the hydraulic diameter for round ducts"; parameter Real kL = Buildings.Fluid.Actuators.BaseClasses.exponentialDamper( y=yL, a=a, b=b, cL=cL, cU=cU, yL=yL, yU=yU)^2 "Loss coefficient at the lower limit of the exponential characteristics"; parameter Real kU = Buildings.Fluid.Actuators.BaseClasses.exponentialDamper( y=yU, a=a, b=b, cL=cL, cU=cU, yL=yL, yU=yU)^2 "Loss coefficient at the upper limit of the exponential characteristics"; parameter Real[3] cL={ (Modelica.Math.log(k0) - b - a)/yL^2, (-b*yL - 2*Modelica.Math.log(k0) + 2*b + 2*a)/yL, Modelica.Math.log(k0)} "Polynomial coefficients for curve fit for y < yl"; parameter Real[3] cU={ (Modelica.Math.log(k1) - a)/(yU^2 - 2*yU + 1), (-b*yU^2 - 2*Modelica.Math.log(k1)*yU - (-2*b - 2*a)*yU - b)/(yU^2 - 2*yU + 1), (Modelica.Math.log(k1)*yU^2 + b*yU^2 + (-2*b - 2*a)*yU + b + a)/(yU^2 - 2*yU + 1)} "Polynomial coefficients for curve fit for y > yu"; parameter Real kDamMax = (2 * rho_default / k1)^0.5 * A "Flow coefficient of damper fully open, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2)"; parameter Real kTotMax = if dpFixed_nominal > Modelica.Constants.eps then sqrt(1 / (1 / kFixed^2 + 1 / kDamMax^2)) else kDamMax "Flow coefficient of damper fully open plus fixed resistance, with unit=(kg.m)^(1/2)"; parameter Real kDamMin = l * kDamMax "Flow coefficient of damper fully closed, with unit=(kg.m)^(1/2)"; parameter Real kTotMin = if dpFixed_nominal > Modelica.Constants.eps then sqrt(1 / (1 / kFixed^2 + 1 / kDamMin^2)) else kDamMin "Flow coefficient of damper fully closed + fixed resistance, with unit=(kg.m)^(1/2)"; initial equation assert(dpDamper_nominal > Modelica.Constants.eps, "In " + getInstanceName() + ": dpDamper_nominal must be strictly greater than zero."); assert(dpFixed_nominal >= 0, "In " + getInstanceName() + ": dpFixed_nominal must be greater than zero."); assert(yL < yU, "In " + getInstanceName() + ": yL must be strictly lower than yU."); assert(m_flow_turbulent > 0, "In " + getInstanceName() + ": m_flow_turbulent must be strictly greater than zero."); assert(k1 >= 0.2, "In " + getInstanceName() + ": k1 must be greater than 0.2. k1=" + String(k1)); assert(k1 < kU, "In " + getInstanceName() + ": k1 must be strictly lower than exp(a + b * (1 - yU)). k1=" + String(k1) + ", exp(...) = " + String(kU)); assert(k0 <= 1e10, "In " + getInstanceName() + ": k0 must be lower than 1e10. k0=" + String(k0)); assert(k0 > kL, "In " + getInstanceName() + ": k0 must be strictly higher than exp(a + b * (1 - yL)). k0=" + String(k0) + ", exp(...) = " + String(kL)); equation rho = if use_constant_density then rho_default else Medium.density(Medium.setState_phX( port_a.p, inStream(port_a.h_outflow), inStream(port_a.Xi_outflow))); // flow coefficient, k = m_flow/sqrt(dp) kDam=sqrt(2*rho)*A/Buildings.Fluid.Actuators.BaseClasses.exponentialDamper( y=y_actual, a=a, b=b, cL=cL, cU=cU, yL=yL, yU=yU); k = if dpFixed_nominal > Modelica.Constants.eps then sqrt(1/(1/kFixed^2 + 1/kDam^2)) else kDam; end PartialDamperExponential;

Buildings.Fluid.Actuators.BaseClasses.PartialThreeWayValve

Partial three way valve

Buildings.Fluid.Actuators.BaseClasses.PartialThreeWayValve

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 Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve for details regarding the valve implementation.

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

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
Conservation equations
Dynamics	energyDynamics	Modelica.Fluid.Types.Dynamic...	Type of energy balance: dynamic (3 initialization options) or steady state
MassFlowRate	mDyn_flow_nominal	m_flow_nominal	Nominal mass flow rate for dynamic momentum and energy balance [kg/s]
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 position of actuator
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	verifyFlowReversal	false	=true, to assert that the flow does not reverse when portFlowDirection_* does not equal Bidirectional
MassFlowRate	m_flow_small	m_flow_nominal*1e-4	Small mass flow rate for checking flow reversal [kg/s]
Boolean	linearized[2]	{false,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]

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 actuator position

Modelica definition

partial model PartialThreeWayValve "Partial three way valve" extends Buildings.Fluid.BaseClasses.PartialThreeWayResistance( m_flow_small = m_flow_nominal*1e-4, final mDyn_flow_nominal = m_flow_nominal, redeclare replaceable Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve res1 constrainedby Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve( deltaM=deltaM, dp(start=dpValve_nominal/2), from_dp=from_dp, final linearized=linearized[1], final homotopyInitialization=homotopyInitialization, final CvData=Buildings.Fluid.Types.CvTypes.OpPoint, final m_flow_nominal=m_flow_nominal, final dpValve_nominal=dpValve_nominal, final dpFixed_nominal=dpFixed_nominal[1], final use_inputFilter=false), redeclare FixedResistances.LosslessPipe res2( m_flow_nominal=m_flow_nominal), redeclare replaceable Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve res3 constrainedby Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve( deltaM=deltaM, dp(start=dpValve_nominal/2), from_dp=from_dp, final linearized=linearized[2], final homotopyInitialization=homotopyInitialization, final CvData=Buildings.Fluid.Types.CvTypes.OpPoint, final m_flow_nominal=m_flow_nominal, final dpValve_nominal=dpValve_nominal/fraK^2, final dpFixed_nominal=dpFixed_nominal[2], final use_inputFilter=false)); extends Buildings.Fluid.Actuators.BaseClasses.ActuatorSignal; extends Buildings.Fluid.Actuators.BaseClasses.ValveParameters( rhoStd=Medium.density_pTX(101325, 273.15+4, Medium.X_default)); constant Boolean homotopyInitialization = true "= true, use homotopy method"; parameter Modelica.Units.SI.PressureDifference dpFixed_nominal[2]( each displayUnit="Pa", each min=0) = {0,0} "Nominal pressure drop of pipes and other equipment in flow legs at port_1 and port_3"; parameter Real fraK(min=0, max=1) = 0.7 "Fraction Kv(port_3→port_2)/Kv(port_1→port_2)"; parameter Real[2] l(each min=0, each max=1) = {0.0001, 0.0001} "Valve leakage, l=Kv(y=0)/Kv(y=1)"; parameter Real deltaM = 0.02 "Fraction of nominal flow rate where linearization starts, if y=1"; parameter Boolean[2] linearized = {false, false} "= true, use linear relation between m_flow and dp for any flow rate"; protected Modelica.Blocks.Math.Feedback inv "Inversion of control signal"; Modelica.Blocks.Sources.Constant uni(final k=1) "Outputs one for bypass valve"; initial equation assert(homotopyInitialization, "In " + getInstanceName() + ": The constant homotopyInitialization has been modified from its default value. This constant will be removed in future releases.", level = AssertionLevel.warning); equation connect(uni.y, inv.u1); end PartialThreeWayValve;

Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve

Partial model for a two way valve

Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve

Information

Partial model for a two way valve. This is the base model for valves with different opening characteristics, such as linear, equal percentage, quick opening or pressure-independent.

To prevent the derivative d/dP (m_flow) to be infinite near the origin, this model linearizes the pressure drop versus flow relation ship. The region in which it is linearized is parameterized by

  m_turbulent_flow = deltaM * m_flow_nominal

Because the parameterization contains Kv_SI, the values for deltaM and dp_nominal need not be changed if the valve size changes.

In contrast to the model in Modelica.Fluid, this model uses the parameter Kv_SI, which is the flow coefficient in SI units, i.e., it is the ratio between mass flow rate in kg/s and square root of pressure drop in Pa.

Options

This model allows different parameterization of the flow resistance. The different parameterizations are described in Buildings.Fluid.Actuators.BaseClasses.ValveParameters.

Implementation

The two way valve models are implemented using this partial model, as opposed to using different functions for the valve opening characteristics, because each valve opening characteristics has different parameters.

Extends from Buildings.Fluid.BaseClasses.PartialResistance (Partial model for a hydraulic resistance), Buildings.Fluid.Actuators.BaseClasses.ValveParameters (Model with parameters for valves), Buildings.Fluid.Actuators.BaseClasses.ActuatorSignal (Partial model that implements the filtered opening for valves and dampers).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
MassFlowRate	m_flow_turbulent	deltaM*abs(m_flow_nominal)	Turbulent flow if \|m_flow\| >= m_flow_turbulent [kg/s]
Real	l	0.0001	Valve leakage, l=Kv(y=0)/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	dp_nominal	dpValve_nominal + dpFixed_no...	Pressure drop at nominal mass flow rate [Pa]
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	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 position of actuator

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 actuator position

Modelica definition

partial model PartialTwoWayValve "Partial model for a two way valve" extends Buildings.Fluid.BaseClasses.PartialResistance( final dp_nominal=dpValve_nominal + dpFixed_nominal, dp(nominal=6000), final m_flow_turbulent = deltaM * abs(m_flow_nominal)); extends Buildings.Fluid.Actuators.BaseClasses.ValveParameters( rhoStd=Medium.density_pTX(101325, 273.15+4, Medium.X_default)); extends Buildings.Fluid.Actuators.BaseClasses.ActuatorSignal; parameter Modelica.Units.SI.PressureDifference dpFixed_nominal( displayUnit="Pa", min=0) = 0 "Pressure drop of pipe and other resistances that are in series"; parameter Real l(min=1e-10, max=1) = 0.0001 "Valve leakage, l=Kv(y=0)/Kv(y=1)"; input Real phi "Ratio actual to nominal mass flow rate of valve, phi=Kv(y)/Kv(y=1)"; parameter Real kFixed(unit="", min=0) = 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 kVal(unit="", min=Modelica.Constants.small) "Flow coefficient of valve, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2)."; Real k(unit="", min=Modelica.Constants.small) "Flow coefficient of valve and pipe in series, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2)."; initial equation assert(dpFixed_nominal > -Modelica.Constants.eps, "In " + getInstanceName() + ": Model requires dpFixed_nominal >= 0 but received dpFixed_nominal = " + String(dpFixed_nominal) + " Pa."); end PartialTwoWayValve;

Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValveKv

Partial model for a two way valve using a Kv characteristic

Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValveKv

Information

Partial model for valves with different opening characteristics, such as linear, equal percentage or quick opening. This partial extends from Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve and also contains the governing equations for these three two way valve models.

Implementation

Models that extend this model need to provide a binding equation for the flow function phi. An example of such a code can be found in Buildings.Fluid.Actuators.Valves.TwoWayLinear.

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	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	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 position of actuator

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 actuator position

Modelica definition

partial model PartialTwoWayValveKv "Partial model for a two way valve using a Kv characteristic" extends Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve; equation kVal = phi*Kv_SI; if (dpFixed_nominal > Modelica.Constants.eps) then k = sqrt(1/(1/kFixed^2 + 1/kVal^2)); else k = kVal; end if; if linearized then // This implementation yields m_flow_nominal = phi*kv_SI * sqrt(dp_nominal) // if m_flow = m_flow_nominal and dp = dp_nominal m_flow*m_flow_nominal_pos = k^2 * dp; else if homotopyInitialization then if from_dp then m_flow=homotopy(actual=Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp(dp=dp, k=k, m_flow_turbulent=m_flow_turbulent), simplified=m_flow_nominal_pos*dp/dp_nominal_pos); else dp=homotopy(actual=Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow(m_flow=m_flow, k=k, m_flow_turbulent=m_flow_turbulent), simplified=dp_nominal_pos*m_flow/m_flow_nominal_pos); end if; else // do not use homotopy if from_dp then m_flow=Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_dp(dp=dp, k=k, m_flow_turbulent=m_flow_turbulent); else dp=Buildings.Fluid.BaseClasses.FlowModels.basicFlowFunction_m_flow(m_flow=m_flow, k=k, m_flow_turbulent=m_flow_turbulent); end if; end if; // homotopyInitialization end if; // linearized end PartialTwoWayValveKv;

Buildings.Fluid.Actuators.BaseClasses.ValveParameters

Model with parameters for valves

Information

Model that computes the flow coefficients of valves. This base class allows the following modeling options, which have been adapted from the valve implementation in Modelica.Fluid to specify the valve flow coefficient in fully open conditions:

CvData = Buildings.Fluid.Types.CvTypes.Av: the flow coefficient is given by the metric Av coefficient (m^2).
CvData = Buildings.Fluid.Types.CvTypes.Kv: the flow coefficient is given by the metric Kv coefficient (m^3/h).
CvData = Buildings.Fluid.Types.CvTypes.Cv: the flow coefficient is given by the US Cv coefficient (USG/min).
CvData = Buildings.Fluid.Types.CvTypes.OpPoint: the flow is computed from the nominal operating point specified by dp_nominal and m_flow_nominal.

The treatment of parameters Kv and Cv is explained in detail in the Users Guide.

In contrast to the model in Modelica.Fluid, this model uses the protected parameter Kv_SI, which is the flow coefficient in SI units, i.e., it is the ratio between mass flow rate in kg/s and square root of pressure drop in Pa. The value of Kv_SI is computed based on the parameters Av, Kv, Cv, or, if CvData = Buildings.Fluid.Types.CvTypes.OpPoint, based on m_flow_nominal and dpValve_nominal. Conversely, if CvData <> Buildings.Fluid.Types.CvTypes.OpPoint, then dpValve_nominal is computed based on Av, Kv, or Cv, and the nominal mass flow rate m_flow_nominal. Therefore, if CvData <> Buildings.Fluid.Types.CvTypes.OpPoint, then specifying a value for dpValve_nominal is a syntax error.

Parameters

Type	Name	Default	Description
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]
Advanced
Nominal condition
Density	rhoStd		Inlet density for which valve coefficients are defined [kg/m3]

Modelica definition

partial model ValveParameters "Model with parameters for valves" parameter Buildings.Fluid.Types.CvTypes CvData=Buildings.Fluid.Types.CvTypes.OpPoint "Selection of flow coefficient"; parameter Real Kv( fixed= if CvData==Buildings.Fluid.Types.CvTypes.Kv then true else false) "Kv (metric) flow coefficient [m3/h/(bar)^(1/2)]"; parameter Real Cv( fixed= if CvData==Buildings.Fluid.Types.CvTypes.Cv then true else false) "Cv (US) flow coefficient [USG/min/(psi)^(1/2)]"; parameter Modelica.Units.SI.Area Av(fixed=if CvData == Buildings.Fluid.Types.CvTypes.Av then true else false) "Av (metric) flow coefficient"; parameter Real deltaM = 0.02 "Fraction of nominal flow rate where linearization starts, if y=1"; parameter Modelica.Units.SI.MassFlowRate m_flow_nominal "Nominal mass flow rate"; parameter Modelica.Units.SI.PressureDifference dpValve_nominal( displayUnit="Pa", min=0, fixed=if CvData == Buildings.Fluid.Types.CvTypes.OpPoint then true else false) "Nominal pressure drop of fully open valve, used if CvData=Buildings.Fluid.Types.CvTypes.OpPoint"; parameter Modelica.Units.SI.Density rhoStd "Inlet density for which valve coefficients are defined"; protected parameter Real Kv_SI( min=0, fixed= false) "Flow coefficient for fully open valve in SI units, Kv=m_flow/sqrt(dp) [kg/s/(Pa)^(1/2)]"; initial equation if CvData == Buildings.Fluid.Types.CvTypes.OpPoint then Kv_SI = m_flow_nominal/sqrt(dpValve_nominal); Kv = Kv_SI/(rhoStd/3600/sqrt(1E5)); Cv = Kv_SI/(rhoStd*0.0631/1000/sqrt(6895)); Av = Kv_SI/sqrt(rhoStd); elseif CvData == Buildings.Fluid.Types.CvTypes.Kv then Kv_SI = Kv*rhoStd/3600/sqrt(1E5) "Unit conversion m3/(h*sqrt(bar)) to kg/(s*sqrt(Pa))"; Cv = Kv_SI/(rhoStd*0.0631/1000/sqrt(6895)); Av = Kv_SI/sqrt(rhoStd); dpValve_nominal = (m_flow_nominal/Kv_SI)^2; elseif CvData == Buildings.Fluid.Types.CvTypes.Cv then Kv_SI = Cv*rhoStd*0.0631/1000/sqrt(6895) "Unit conversion USG/(min*sqrt(psi)) to kg/(s*sqrt(Pa))"; Kv = Kv_SI/(rhoStd/3600/sqrt(1E5)); Av = Kv_SI/sqrt(rhoStd); dpValve_nominal = (m_flow_nominal/Kv_SI)^2; else assert(CvData == Buildings.Fluid.Types.CvTypes.Av, "Invalid value for CvData. Obtained CvData = " + String(CvData) + "."); Kv_SI = Av*sqrt(rhoStd); Kv = Kv_SI/(rhoStd/3600/sqrt(1E5)); Cv = Kv_SI/(rhoStd*0.0631/1000/sqrt(6895)); dpValve_nominal = (m_flow_nominal/Kv_SI)^2; end if; end ValveParameters;

Buildings.Fluid.Actuators.BaseClasses.der_equalPercentage

Derivative of valve opening characteristics for equal percentage valve

Information

This function computes the derivative of the opening characteristics of an equal percentage valve.

The function is the derivative of Buildings.Fluid.Actuators.BaseClasses.equalPercentage.

Extends from Modelica.Icons.Function (Icon for functions).

Inputs

Type	Name	Description
Real	y	Valve opening signal, y=1 is fully open
Real	R	Rangeability, R=50...100 typically
Real	l	Valve leakage, l=Kv(y=0)/Kv(y=1)
Real	delta	Range of significant deviation from equal percentage law
Real	der_y	Derivative of valve opening signal

Outputs

Type	Name	Description
Real	der_phi	Derivative of ratio actual to nominal mass flow rate, dphi/dy

Modelica definition

function der_equalPercentage "Derivative of valve opening characteristics for equal percentage valve" extends Modelica.Icons.Function; input Real y "Valve opening signal, y=1 is fully open"; input Real R "Rangeability, R=50...100 typically"; input Real l(min=0, max=1) "Valve leakage, l=Kv(y=0)/Kv(y=1)"; input Real delta "Range of significant deviation from equal percentage law"; input Real der_y "Derivative of valve opening signal"; output Real der_phi "Derivative of ratio actual to nominal mass flow rate, dphi/dy"; protected Real a "Polynomial coefficient"; Real b "Polynomial coefficient"; Real c "Polynomial coefficient"; Real logR "=log(R)"; Real z "Auxiliary variable"; Real q "Auxiliary variable"; Real p "Auxiliary variable"; algorithm if y < delta/2 then der_phi := (R^(delta-1) - l) / delta * der_y; else if (y > (3/2 * delta)) then der_phi := R^(y-1)*Modelica.Math.log(R) * der_y; else logR := Modelica.Math.log(R); z := (3*delta/2); q := delta*R^z*logR; p := R^z; a := (q - 2*p + 2*R^delta)/(delta^3*R); b := (-5*q + 12*p - 13*R^delta + l*R)/(2*delta^2*R); c := (7*q - 18*p + 24*R^delta - 6*l*R)/(4*delta*R); der_phi := (c + y * ( 2*b + 3*a*y)) * der_y; end if; end if; end der_equalPercentage;

Buildings.Fluid.Actuators.BaseClasses.equalPercentage

Valve opening characteristics for equal percentage valve

Information

This function computes the opening characteristics of an equal percentage valve.

The function is used by the model Buildings.Fluid.Actuators.Valves.TwoWayEqualPercentage.

For y < delta/2, the valve characteristics is linear. For y > 3*delta/2 the valve characteristics is equal percentage. In between, a cubic spline is used to ensure that the valve characteristics is once continuously differentiable with respect to y.

Extends from Modelica.Icons.Function (Icon for functions).

Inputs

Type	Name	Description
Real	y	Valve opening signal, y=1 is fully open
Real	R	Rangeability, R=50...100 typically
Real	l	Valve leakage, l=Kv(y=0)/Kv(y=1)
Real	delta	Range of significant deviation from equal percentage law

Outputs

Type	Name	Description
Real	phi	Ratio actual to nominal mass flow rate, phi=Cv(y)/Cv(y=1)

Modelica definition

function equalPercentage "Valve opening characteristics for equal percentage valve" annotation(derivative=der_equalPercentage); extends Modelica.Icons.Function; input Real y "Valve opening signal, y=1 is fully open"; input Real R "Rangeability, R=50...100 typically"; input Real l(min=0, max=1) "Valve leakage, l=Kv(y=0)/Kv(y=1)"; input Real delta "Range of significant deviation from equal percentage law"; output Real phi "Ratio actual to nominal mass flow rate, phi=Cv(y)/Cv(y=1)"; protected Real a "Polynomial coefficient"; Real b "Polynomial coefficient"; Real c "Polynomial coefficient"; Real d "Polynomial coefficient"; Real logR "=log(R)"; Real z "Auxiliary variable"; Real q "Auxiliary variable"; Real p "Auxiliary variable"; algorithm if y < delta/2 then phi := l + y * (R^(delta-1) - l) / delta; else if (y > (3/2 * delta)) then phi := R^(y-1); else logR := Modelica.Math.log(R); z := (3*delta/2); q := delta*R^z*logR; p := R^z; a := (q - 2*p + 2*R^delta)/(delta^3*R); b := (-5*q + 12*p - 13*R^delta + l*R)/(2*delta^2*R); c := (7*q - 18*p + 24*R^delta - 6*l*R)/(4*delta*R); d := (-3*q + 8*p - 9*R^delta + 9*l*R)/(8*R); phi := d + y * ( c + y * ( b + y * a)); end if; end if; end equalPercentage;

Buildings.Fluid.Actuators.BaseClasses.exponentialDamper

Damper opening characteristics for an exponential damper

Information

This function computes the opening characteristics of an exponential damper.

The function is used by the model Buildings.Fluid.Actuators.Dampers.Exponential.

For yL < y < yU, the damper characteristics is

k_d(y) = exp(a+b (1-y)).

Outside this range, the damper characteristic is defined by a quadratic polynomial.

Note that this implementation returns sqrt(k_d(y)) instead of k_d(y). This is done for numerical reason since otherwise k_d(y) may be an iteration variable, which may cause a lot of warnings and slower convergence if the solver attempts k_d(y) < 0 during the iterative solution procedure.

Extends from Modelica.Icons.Function (Icon for functions).

Inputs

Type	Name	Description
Real	y	Control signal, y=0 is closed, y=1 is open
Real	a	Coefficient a for damper characteristics
Real	b	Coefficient b for damper characteristics
Real	cL[3]	Polynomial coefficients for curve fit for y < yl
Real	cU[3]	Polynomial coefficients for curve fit for y > yu
Real	yL	Lower value for damper curve
Real	yU	Upper value for damper curve

Outputs

Type	Name	Description
Real	kThetaSqRt	Square root of loss coefficient, sqrt(pressure drop/dynamic pressure)

Modelica definition

function exponentialDamper "Damper opening characteristics for an exponential damper" extends Modelica.Icons.Function; input Real y(min=0, max=1, unit="") "Control signal, y=0 is closed, y=1 is open"; input Real a(unit="") "Coefficient a for damper characteristics"; input Real b(unit="") "Coefficient b for damper characteristics"; input Real[3] cL "Polynomial coefficients for curve fit for y < yl"; input Real[3] cU "Polynomial coefficients for curve fit for y > yu"; input Real yL "Lower value for damper curve"; input Real yU "Upper value for damper curve"; output Real kThetaSqRt(min=0) "Square root of loss coefficient, sqrt(pressure drop/dynamic pressure)"; protected Real yC(min=0, max=1, unit="") "y constrained to 0 <= y <= 1 to avoid numerical problems"; algorithm if y < yL then yC :=max(0, y); kThetaSqRt := sqrt(Modelica.Math.exp(cL[3] + yC * (cL[2] + yC * cL[1]))); else if (y > yU) then yC := min(1, y); kThetaSqRt := sqrt(Modelica.Math.exp(cU[3] + yC * (cU[2] + yC * cU[1]))); else kThetaSqRt := sqrt(Modelica.Math.exp(a+b*(1-y))) "y=0 is closed"; end if; end if; end exponentialDamper;