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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

NameDescription
Buildings.Fluid.Actuators.BaseClasses.ActuatorSignal ActuatorSignal Partial model that implements the filtered opening for valves and dampers
Buildings.Fluid.Actuators.BaseClasses.PartialDamperExponential PartialDamperExponential Partial model for air dampers with exponential opening characteristics
Buildings.Fluid.Actuators.BaseClasses.PartialThreeWayValve PartialThreeWayValve Partial three way valve
Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve PartialTwoWayValve Partial model for a two way valve
ValveParameters Model with parameters for valves
Buildings.Fluid.Actuators.BaseClasses.der_equalPercentage der_equalPercentage Derivative of valve opening characteristics for equal percentage valve
Buildings.Fluid.Actuators.BaseClasses.equalPercentage equalPercentage Valve opening characteristics for equal percentage valve
Buildings.Fluid.Actuators.BaseClasses.exponentialDamper exponentialDamper Damper opening characteristics for an exponential damper
Buildings.Fluid.Actuators.BaseClasses.Examples Examples Collection of models that illustrate model use and test models


Buildings.Fluid.Actuators.BaseClasses.ActuatorSignal 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

TypeNameDefaultDescription
Dynamics
Filtered opening
BooleanfilteredOpeningtrue= true, if opening is filtered with a 2nd order CriticalDamping filter
TimeriseTime120Rise time of the filter (time to reach 99.6 % of an opening step) [s]
InitinitModelica.Blocks.Types.Init.I...Type of initialization (no init/steady state/initial state/initial output)
Realy_start1Initial value of output

Connectors

TypeNameDescription
input RealInputyActuator position (0: closed, 1: open)
output RealOutputy_actualActual valve position

Modelica definition

model ActuatorSignal 
  "Partial model that implements the filtered opening for valves and dampers"

  parameter Boolean filteredOpening=true 
    "= true, if opening is filtered with a 2nd order CriticalDamping filter";
  parameter Modelica.SIunits.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 value of output";

  Modelica.Blocks.Interfaces.RealInput y(min=0, max=1) 
    "Actuator position (0: closed, 1: open)";

  Modelica.Blocks.Interfaces.RealOutput y_actual "Actual valve position";

  // Classes used to implement the filtered opening
protected 
  Modelica.Blocks.Interfaces.RealOutput y_filtered if filteredOpening 
    "Filtered valve position in the range 0..1";

  Modelica.Blocks.Continuous.Filter filter(
     order=2,
     f_cut=5/(2*Modelica.Constants.pi*riseTime),
     final init=init,
     final y_start=y_start,
     final analogFilter=Modelica.Blocks.Types.AnalogFilter.CriticalDamping,
     final filterType=Modelica.Blocks.Types.FilterType.LowPass,
     x(each stateSelect=StateSelect.always)) if 
        filteredOpening 
    "Second order filter to approximate valve opening time, and to improve numerics";

equation 
 connect(filter.y, y_filtered);
  if filteredOpening then
  connect(y, filter.u);
  connect(filter.y, y_actual);
  else
    connect(y, y_actual);
  end if;

end ActuatorSignal;

Buildings.Fluid.Actuators.BaseClasses.PartialDamperExponential 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 and variable air volume flow boxes. The model implements the functions that relate the opening signal, the pressure drop and the mass flow rate. The model also defines parameters that are used by different air damper models.

For a description of the opening characteristics and typical parameter values, see the damper model Exponential.

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

TypeNameDefaultDescription
replaceable package MediumPartialMediumMedium in the component
MassFlowRatem_flow_turbulentif use_deltaM then deltaM*m_...Turbulent flow if |m_flow| >= m_flow_turbulent [kg/s]
Booleanuse_deltaMtrueSet to true to use deltaM for turbulent transition, else ReC is used
RealdeltaM0.3Fraction of nominal mass flow rate where transition to turbulent occurs
Booleanuse_v_nominaltrueSet to true to use face velocity to compute area
Velocityv_nominal1Nominal face velocity [m/s]
AreaAm_flow_nominal/rho_nominal/v...Face area [m2]
BooleanroundDuctfalseSet to true for round duct, false for square cross section
RealReC4000Reynolds number where transition to turbulent starts
RealkFixed Flow coefficient of fixed resistance that may be in series with damper, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2).
Nominal condition
MassFlowRatem_flow_nominal Nominal mass flow rate [kg/s]
Pressuredp_nominal Pressure drop at nominal mass flow rate [Pa]
Initialization
MassFlowRatem_flow.start0Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]
Pressuredp.start0Pressure difference between port_a and port_b [Pa]
Assumptions
BooleanallowFlowReversalsystem.allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
BooleanhomotopyInitializationtrue= true, use homotopy method
Booleanfrom_dpfalse= true, use m_flow = f(dp) else dp = f(m_flow)
Booleanlinearizedfalse= true, use linear relation between m_flow and dp for any flow rate
Booleanuse_constant_densitytrueSet to true to use constant density for flow friction
Diagnostics
Booleanshow_V_flowfalse= true, if volume flow rate at inflowing port is computed
Booleanshow_Tfalse= true, if actual temperature at port is computed (may lead to events)
Dynamics
Filtered opening
BooleanfilteredOpeningtrue= true, if opening is filtered with a 2nd order CriticalDamping filter
TimeriseTime120Rise time of the filter (time to reach 99.6 % of an opening step) [s]
InitinitModelica.Blocks.Types.Init.I...Type of initialization (no init/steady state/initial state/initial output)
Realy_start1Initial value of output
Damper coefficients
Reala-1.51Coefficient a for damper characteristics
Realb0.105*90Coefficient b for damper characteristics
RealyL15/90Lower value for damper curve
RealyU55/90Upper value for damper curve
Realk01E6Flow coefficient for y=0, k0 = pressure drop divided by dynamic pressure
Realk10.45Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure

Connectors

TypeNameDescription
FluidPort_aport_aFluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_bport_bFluid connector b (positive design flow direction is from port_a to port_b)
input RealInputyActuator position (0: closed, 1: open)
output RealOutputy_actualActual valve position

Modelica definition

partial model PartialDamperExponential 
  "Partial model for air dampers with exponential opening characteristics"
   extends Buildings.Fluid.BaseClasses.PartialResistance(
      m_flow_turbulent=if use_deltaM then deltaM * m_flow_nominal else 
      eta_nominal*ReC*sqrt(area)*facRouDuc);
   extends Buildings.Fluid.Actuators.BaseClasses.ActuatorSignal;
 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";
 parameter Boolean use_v_nominal = true 
    "Set to true to use face velocity to compute area";
 parameter Modelica.SIunits.Velocity v_nominal=1 "Nominal face velocity";
 parameter Modelica.SIunits.Area A=m_flow_nominal/rho_nominal/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 turbulent starts";
 parameter Real a(unit="")=-1.51 "Coefficient a for damper characteristics";
 parameter Real b(unit="")=0.105*90 "Coefficient b for damper characteristics";
 parameter Real yL = 15/90 "Lower value for damper curve";
 parameter Real yU = 55/90 "Upper value for damper curve";
 parameter Real k0(min=0) = 1E6 
    "Flow coefficient for y=0, k0 = pressure drop divided by dynamic pressure";
 parameter Real k1(min=0) = 0.45 
    "Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure";
 parameter Boolean use_constant_density=true 
    "Set to true to use constant density for flow friction";
 Medium.Density rho "Medium density";
 parameter Real kFixed(unit="") 
    "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(unit="") 
    "Flow coefficient of damper, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2)";
 Real k(unit="") 
    "Flow coefficient of damper plus fixed resistance, k=m_flow/sqrt(dp), with unit=(kg.m)^(1/2)";
protected 
 parameter Medium.Density rho_nominal=Medium.density(sta0) 
    "Density, used to compute fluid volume";
 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 facRouDuc= if roundDuct then sqrt(Modelica.Constants.pi)/2 else 1;
 parameter Modelica.SIunits.Area area=
    if use_v_nominal then m_flow_nominal/rho_nominal/v_nominal else A 
    "Face velocity used in the computation";
initial equation 
  assert(k0 > k1, "k0 must be bigger than k1.");
  assert(m_flow_turbulent > 0, "m_flow_turbulent must be bigger than zero.");
equation 
  rho = if use_constant_density then 
         rho_nominal 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)*area/Buildings.Fluid.Actuators.BaseClasses.exponentialDamper(
    y=y_actual,
    a=a,
    b=b,
    cL=cL,
    cU=cU,
    yL=yL,
    yU=yU);
  k = if (kFixed>Modelica.Constants.eps) then sqrt(1/(1/kFixed^2 + 1/kDam^2)) else kDam;
  // Pressure drop calculation
  if linearized then
    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;  // from_dp
    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;  // from_dp
    end if; // homotopyInitialization
  end if; // linearized
end PartialDamperExponential;

Buildings.Fluid.Actuators.BaseClasses.PartialThreeWayValve 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_SI for flow from port_1 -> port_2 is a parameter and the flow coefficient for flow from port_3 -> port_2 is computed as

         Kv_SI(port_1 -> port_2)
  fraK = ----------------------
         Kv_SI(port_3 -> port_2)
where fraK is a parameter.

Since this model uses two way valves to construct a three way valve, see 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.ValveParameters (Model with parameters for valves), Buildings.Fluid.Actuators.BaseClasses.ActuatorSignal (Partial model that implements the filtered opening for valves and dampers).

Parameters

TypeNameDefaultDescription
replaceable package MediumPartialMediumMedium in the component
RealfraK0.7Fraction Kv_SI(port_1->port_2)/Kv_SI(port_3->port_2)
Reall[2]{0,0}Valve leakage, l=Cv(y=0)/Cvs
Flow Coefficient
CvTypesCvDataBuildings.Fluid.Types.CvType...Selection of flow coefficient
RealKv0Kv (metric) flow coefficient [m3/h/(bar)^(1/2)]
RealCv0Cv (US) flow coefficient [USG/min/(psi)^(1/2)]
AreaAv0Av (metric) flow coefficient [m2]
RealKv_SIm_flow_nominal/sqrt(dpValve_...Flow coefficient for fully open valve in SI units, Kv=m_flow/sqrt(dp) [kg/s/(Pa)^(1/2)]
Pressure-flow linearization
RealdeltaM0.02Fraction of nominal flow rate where linearization starts, if y=1
Nominal condition
MassFlowRatem_flow_nominal Nominal mass flow rate [kg/s]
PressuredpValve_nominal6000Nominal pressure drop of fully open valve [Pa]
PressuredpFixed_nominal[2]{0,0}Nominal pressure drop of pipes and other equipment in flow legs at port_1 and port_3 [Pa]
Dynamics
Equations
DynamicsenergyDynamicsModelica.Fluid.Types.Dynamic...Formulation of energy balance
DynamicsmassDynamicsenergyDynamicsFormulation of mass balance
BooleandynamicBalancetrueSet to true to use a dynamic balance, which often leads to smaller systems of equations
MassFlowRatemDyn_flow_nominalm_flow_nominalNominal mass flow rate for dynamic momentum and energy balance [kg/s]
Nominal condition
Timetau10Time constant at nominal flow for dynamic energy and momentum balance [s]
Filtered opening
BooleanfilteredOpeningtrue= true, if opening is filtered with a 2nd order CriticalDamping filter
TimeriseTime120Rise time of the filter (time to reach 99.6 % of an opening step) [s]
InitinitModelica.Blocks.Types.Init.I...Type of initialization (no init/steady state/initial state/initial output)
Realy_start1Initial value of output
Initialization
AbsolutePressurep_startMedium.p_defaultStart value of pressure [Pa]
TemperatureT_startMedium.T_defaultStart value of temperature [K]
MassFractionX_start[Medium.nX]Medium.X_defaultStart value of mass fractions m_i/m [kg/kg]
ExtraPropertyC_start[Medium.nC]fill(0, Medium.nC)Start value of trace substances
ExtraPropertyC_nominal[Medium.nC]fill(1E-2, Medium.nC)Nominal value of trace substances. (Set to typical order of magnitude.)
Advanced
Booleanfrom_dptrue= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanhomotopyInitializationtrue= true, use homotopy method
Booleanlinearized[2]{false,false}= true, use linear relation between m_flow and dp for any flow rate
Nominal condition
DensityrhoStdMedium.density_pTX(101325, 2...Inlet density for which valve coefficients are defined [kg/m3]

Connectors

TypeNameDescription
FluidPort_aport_1 
FluidPort_bport_2 
FluidPort_aport_3 
input RealInputyActuator position (0: closed, 1: open)
output RealOutputy_actualActual valve position

Modelica definition

partial model PartialThreeWayValve "Partial three way valve"
    extends Buildings.Fluid.BaseClasses.PartialThreeWayResistance(
      final mDyn_flow_nominal = m_flow_nominal,
        redeclare replaceable Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve
            res1 constrainedby 
      Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve(
               redeclare package Medium = Medium,
               l=l[1],
               deltaM=deltaM,
               dpValve_nominal=dpValve_nominal,
               dpFixed_nominal=dpFixed_nominal[1],
               dp(start=dpValve_nominal/2),
               from_dp=from_dp,
               linearized=linearized[1],
               homotopyInitialization=homotopyInitialization,
               m_flow_nominal=m_flow_nominal,
               CvData=CvData,
               Kv_SI=Kv_SI,
               Kv=Kv,
               Cv=Cv,
               Av=Av,
               final filteredOpening=false),
        redeclare FixedResistances.LosslessPipe res2(
          redeclare package Medium = Medium, m_flow_nominal=m_flow_nominal),
        redeclare replaceable Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve
            res3 constrainedby 
      Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve(
               redeclare package Medium = Medium,
               l=l[2],
               deltaM=deltaM,
               dpValve_nominal=dpValve_nominal,
               dpFixed_nominal=dpFixed_nominal[2],
               dp(start=dpValve_nominal/2),
               from_dp=from_dp,
               linearized=linearized[2],
               homotopyInitialization=homotopyInitialization,
               m_flow_nominal=m_flow_nominal,
               CvData=CvData,
               Kv_SI=fraK*Kv_SI,
               Kv=fraK*Kv,
               Cv=fraK*Cv,
               Av=fraK*Av,
               final filteredOpening=false));
    extends Buildings.Fluid.Actuators.BaseClasses.ValveParameters(
      dpValve_nominal=6000,
      rhoStd=Medium.density_pTX(101325, 273.15+4, Medium.X_default));
    extends Buildings.Fluid.Actuators.BaseClasses.ActuatorSignal;

  parameter Real fraK(min=0, max=1) = 0.7 
    "Fraction Kv_SI(port_1->port_2)/Kv_SI(port_3->port_2)";
  parameter Real[2] l(min=0, max=1) = {0, 0} "Valve leakage, l=Cv(y=0)/Cvs";
  parameter Real deltaM = 0.02 
    "Fraction of nominal flow rate where linearization starts, if y=1";
  parameter Medium.MassFlowRate m_flow_nominal(min=0) "Nominal mass flow rate";
  parameter Modelica.SIunits.Pressure 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 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";
equation 

  connect(uni.y, inv.u1);
end PartialThreeWayValve;

Buildings.Fluid.Actuators.BaseClasses.PartialTwoWayValve 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 or quick opening.

Modelling options

The following options have been adapted from the valve implementation in Modelica.Fluid and are described in Buildings.Fluid.Actuators.BaseClasses.ValveParameters.

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.

To prevent the derivative d/dP (m_flow) to be infinite near the origin, this model linearizes the pressure drop vs. 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.

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

TypeNameDefaultDescription
replaceable package MediumPartialMediumMedium in the component
MassFlowRatem_flow_turbulentdeltaM*abs(m_flow_nominal)Turbulent flow if |m_flow| >= m_flow_turbulent [kg/s]
Reall0.0001Valve leakage, l=Cv(y=0)/Cvs
Nominal condition
MassFlowRatem_flow_nominal Nominal mass flow rate [kg/s]
Pressuredp_nominaldpValve_nominal + dpFixed_no...Pressure drop at nominal mass flow rate [Pa]
PressuredpValve_nominal6000Nominal pressure drop of fully open valve [Pa]
PressuredpFixed_nominal0Pressure drop of pipe and other resistances that are in series [Pa]
Initialization
MassFlowRatem_flow.start0Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]
Pressuredp.start0Pressure difference between port_a and port_b [Pa]
Flow Coefficient
CvTypesCvDataBuildings.Fluid.Types.CvType...Selection of flow coefficient
RealKv0Kv (metric) flow coefficient [m3/h/(bar)^(1/2)]
RealCv0Cv (US) flow coefficient [USG/min/(psi)^(1/2)]
AreaAv0Av (metric) flow coefficient [m2]
RealKv_SIm_flow_nominal/sqrt(dpValve_...Flow coefficient for fully open valve in SI units, Kv=m_flow/sqrt(dp) [kg/s/(Pa)^(1/2)]
Pressure-flow linearization
RealdeltaM0.02Fraction of nominal flow rate where linearization starts, if y=1
Assumptions
BooleanallowFlowReversalsystem.allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
BooleanhomotopyInitializationtrue= true, use homotopy method
Booleanfrom_dpfalse= true, use m_flow = f(dp) else dp = f(m_flow)
Booleanlinearizedfalse= true, use linear relation between m_flow and dp for any flow rate
Diagnostics
Booleanshow_V_flowfalse= true, if volume flow rate at inflowing port is computed
Booleanshow_Tfalse= true, if actual temperature at port is computed (may lead to events)
Nominal condition
DensityrhoStdMedium.density_pTX(101325, 2...Inlet density for which valve coefficients are defined [kg/m3]
Dynamics
Filtered opening
BooleanfilteredOpeningtrue= true, if opening is filtered with a 2nd order CriticalDamping filter
TimeriseTime120Rise time of the filter (time to reach 99.6 % of an opening step) [s]
InitinitModelica.Blocks.Types.Init.I...Type of initialization (no init/steady state/initial state/initial output)
Realy_start1Initial value of output

Connectors

TypeNameDescription
FluidPort_aport_aFluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_bport_bFluid connector b (positive design flow direction is from port_a to port_b)
input RealInputyActuator position (0: closed, 1: open)
output RealOutputy_actualActual valve 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,
       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),
      dpValve_nominal=6000);
  extends Buildings.Fluid.Actuators.BaseClasses.ActuatorSignal;
  parameter Modelica.SIunits.Pressure 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=Cv(y=0)/Cvs";
  Real phi "Ratio actual to nominal mass flow rate of valve, phi=Cv(y)/Cv(y=1)";
protected 
 parameter Real kFixed(unit="") = if dpFixed_nominal > Modelica.Constants.small
    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 
  // 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(dpFixed_nominal > -Modelica.Constants.small, "Require dpFixed_nominal >= 0. Received dpFixed_nominal = "
        + String(dpFixed_nominal) + " Pa.");
equation 
 kVal = phi*Kv_SI;
 k = if (dpFixed_nominal > Modelica.Constants.eps) then sqrt(1/(1/kFixed^2 + 1/kVal^2)) else kVal;

 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 PartialTwoWayValve;

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:

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 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.

Parameters

TypeNameDefaultDescription
Flow Coefficient
CvTypesCvDataBuildings.Fluid.Types.CvType...Selection of flow coefficient
RealKv0Kv (metric) flow coefficient [m3/h/(bar)^(1/2)]
RealCv0Cv (US) flow coefficient [USG/min/(psi)^(1/2)]
AreaAv0Av (metric) flow coefficient [m2]
RealKv_SIm_flow_nominal/sqrt(dpValve_...Flow coefficient for fully open valve in SI units, Kv=m_flow/sqrt(dp) [kg/s/(Pa)^(1/2)]
Pressure-flow linearization
RealdeltaM0.02Fraction of nominal flow rate where linearization starts, if y=1
Nominal condition
MassFlowRatem_flow_nominal Nominal mass flow rate [kg/s]
PressuredpValve_nominal Nominal pressure drop of fully open valve [Pa]
Advanced
Nominal condition
DensityrhoStd 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) = 0 
    "Kv (metric) flow coefficient [m3/h/(bar)^(1/2)]";
  parameter Real Cv(
    fixed= if CvData==Buildings.Fluid.Types.CvTypes.Cv then true else false) = 0 
    "Cv (US) flow coefficient [USG/min/(psi)^(1/2)]";
  parameter Modelica.SIunits.Area Av(
    fixed= if CvData==Buildings.Fluid.Types.CvTypes.Av then true else false) = 0 
    "Av (metric) flow coefficient";
  parameter Real deltaM = 0.02 
    "Fraction of nominal flow rate where linearization starts, if y=1";
  parameter Modelica.SIunits.MassFlowRate m_flow_nominal(min=0) 
    "Nominal mass flow rate";
  parameter Modelica.SIunits.Pressure dpValve_nominal(displayUnit="Pa",
                                                      min=Modelica.Constants.small) 
    "Nominal pressure drop of fully open valve";

  parameter Real Kv_SI(
    min=0,
    fixed= if CvData==Buildings.Fluid.Types.CvTypes.OpPoint then true else false,
    start=m_flow_nominal/sqrt(dpValve_nominal)) = m_flow_nominal/sqrt(dpValve_nominal) 
    "Flow coefficient for fully open valve in SI units, Kv=m_flow/sqrt(dp) [kg/s/(Pa)^(1/2)]";

  parameter Modelica.SIunits.Density rhoStd 
    "Inlet density for which valve coefficients are defined";

initial equation 
    Kv_SI = Av * sqrt(rhoStd);
    Kv_SI = Kv*rhoStd/3600/sqrt(1E5) 
    "Unit conversion m3/(h*sqrt(bar)) to kg/(s*sqrt(Pa))";
    Kv_SI = Cv*rhoStd*0.0631/1000/sqrt(6895) 
    "Unit conversion USG/(min*sqrt(psi)) to kg/(s*sqrt(Pa))";
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 TwoWayValveEqualPercentage.

Inputs

TypeNameDefaultDescription
Realy Valve opening signal, y=1 is fully open
RealR Rangeability, R=50...100 typically
Reall Valve leakage, l=Cv(y=0)/Cvs
Realdelta Range of significant deviation from equal percentage law
Realder_y Derivative of valve opening signal

Outputs

TypeNameDescription
Realder_phiDerivative of ratio actual to nominal mass flow rate, dphi/dy

Modelica definition

function der_equalPercentage 
  "Derivative of valve opening characteristics for equal percentage valve"

  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=Cv(y=0)/Cvs";
  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 TwoWayValveEqualPercentage.

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.

Inputs

TypeNameDefaultDescription
Realy Valve opening signal, y=1 is fully open
RealR Rangeability, R=50...100 typically
Reall Valve leakage, l=Cv(y=0)/Cvs
Realdelta Range of significant deviation from equal percentage law

Outputs

TypeNameDescription
RealphiRatio 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);

  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=Cv(y=0)/Cvs";
  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 Dampers.Exponential.

For yL < y < yU, the damper characteristics is

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

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

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

Inputs

TypeNameDefaultDescription
Realy Control signal, y=0 is closed, y=1 is open
Reala Coefficient a for damper characteristics
Realb Coefficient b for damper characteristics
RealcL[3] Polynomial coefficients for curve fit for y < yl
RealcU[3] Polynomial coefficients for curve fit for y > yu
RealyL Lower value for damper curve
RealyU Upper value for damper curve

Outputs

TypeNameDescription
RealkThetaSqRtFlow coefficient, kThetaSqRT = =sqrt(kTheta) = sqrt(pressure drop/dynamic pressure)

Modelica definition

function exponentialDamper 
  "Damper opening characteristics for an exponential damper"
  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) 
    "Flow coefficient, kThetaSqRT = =sqrt(kTheta) = 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;

Automatically generated Wed Feb 29 16:52:11 2012.