Buildings.Fluid.Actuators.Dampers

Package with air damper models

Information

This package contains components models for air dampers. For motor models, see Buildings.Fluid.Actuators.Motors.

Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).

Package Content

Name Description

Exponential Air damper with exponential opening characteristics

VAVBoxExponential VAV box with a fixed resistance plus a damper model withe exponential characteristics

MixingBox Outside air mixing box with interlocked air dampers

MixingBoxMinimumFlow Outside air mixing box with parallel damper for minimum outside air flow rate

Name	Description
Exponential	Air damper with exponential opening characteristics
VAVBoxExponential	VAV box with a fixed resistance plus a damper model withe exponential characteristics
MixingBox	Outside air mixing box with interlocked air dampers
MixingBoxMinimumFlow	Outside air mixing box with parallel damper for minimum outside air flow rate

Buildings.Fluid.Actuators.Dampers.Exponential

Air damper with exponential opening characteristics

Buildings.Fluid.Actuators.Dampers.Exponential

Information

This model is an air damper with flow coefficient that is an exponential function of the opening angle. The model is as in ASHRAE 825-RP. 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 = exp(a+b (1-y)).

Outside this range, the damper characteristic 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(y) is differentiable in y and the derivative is continuous.

ASHRAE 825-RP lists the following parameter values as typical:

opposed blades single blades

yL 15/90 15/90

yU 55/90 65/90

k0 1E6 1E6

k1 0.2 to 0.5 0.2 to 0.5

a -1.51 -1.51

b 0.105*90 0.0842*90

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.Actuators.BaseClasses.PartialDamperExponential (Partial model for air dampers with exponential opening characteristics).

Parameters

Type Name Default Description

replaceable package Medium PartialMedium Medium in the component

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 use_v_nominal true Set to true to use face velocity to compute area

Velocity v_nominal 1 Nominal face velocity [m/s]

Area A m_flow_nominal/rho_nominal/v... Face area [m2]

Boolean roundDuct false Set to true for round duct, false for square cross section

Real ReC 4000 Reynolds number where transition to turbulent starts

Real kFixed 0 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

MassFlowRate m_flow_nominal Nominal mass flow rate [kg/s]

Pressure dp_nominal (m_flow_nominal/kDam_nominal... Pressure drop at nominal mass flow rate [Pa]

Initialization

MassFlowRate m_flow.start 0 Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]

Assumptions

Boolean allowFlowReversal system.allowFlowReversal = true to allow flow reversal, false restricts to design direction (port_a -> port_b)

Advanced

MassFlowRate m_flow_small 1E-4*abs(m_flow_nominal) Small mass flow rate for regularization of zero flow [kg/s]

Boolean homotopyInitialization true = true, use homotopy method

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

Diagnostics

Boolean show_V_flow false = true, if volume flow rate at inflowing port is computed

Boolean show_T false = true, if actual temperature at port is computed (may lead to events)

Damper coefficients

Real a -1.51 Coefficient a for damper characteristics

Real b 0.105*90 Coefficient b for damper characteristics

Real yL 15/90 Lower value for damper curve

Real yU 55/90 Upper value for damper curve

Real k0 1E6 Flow coefficient for y=0, k0 = pressure drop divided by dynamic pressure

Real k1 0.45 Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure

Type	Name	Default	Description
replaceable package Medium	PartialMedium	Medium in the component
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	use_v_nominal	true	Set to true to use face velocity to compute area
Velocity	v_nominal	1	Nominal face velocity [m/s]
Area	A	m_flow_nominal/rho_nominal/v...	Face area [m2]
Boolean	roundDuct	false	Set to true for round duct, false for square cross section
Real	ReC	4000	Reynolds number where transition to turbulent starts
Real	kFixed	0	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
MassFlowRate	m_flow_nominal		Nominal mass flow rate [kg/s]
Pressure	dp_nominal	(m_flow_nominal/kDam_nominal...	Pressure drop at nominal mass flow rate [Pa]
Initialization
MassFlowRate	m_flow.start	0	Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
MassFlowRate	m_flow_small	1E-4*abs(m_flow_nominal)	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	homotopyInitialization	true	= true, use homotopy method
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
Diagnostics
Boolean	show_V_flow	false	= true, if volume flow rate at inflowing port is computed
Boolean	show_T	false	= true, if actual temperature at port is computed (may lead to events)
Damper coefficients
Real	a	-1.51	Coefficient a for damper characteristics
Real	b	0.105*90	Coefficient b for damper characteristics
Real	yL	15/90	Lower value for damper curve
Real	yU	55/90	Upper value for damper curve
Real	k0	1E6	Flow coefficient for y=0, k0 = pressure drop divided by dynamic pressure
Real	k1	0.45	Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure

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)

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)

Modelica definition

model Exponential 
  "Air damper with exponential opening characteristics"
  extends Buildings.Fluid.Actuators.BaseClasses.PartialDamperExponential(
  final dp_nominal=(m_flow_nominal/kDam_nominal)^2,
  dp(nominal=10),
  final kFixed=0);
protected 
   parameter Real kDam_nominal(fixed=false) 
    "Flow coefficient for damper, k=m_flow/sqrt(dp), with unit=(kg*m)^(1/2)";
   parameter Real kThetaSqRt_nominal(min=0, fixed=false) 
    "Flow coefficient, kThetaSqRt = sqrt(pressure drop divided by dynamic pressure)";
initial algorithm 
   kThetaSqRt_nominal :=Buildings.Fluid.Actuators.BaseClasses.exponentialDamper(
    y=1,
    a=a,
    b=b,
    cL=cL,
    cU=cU,
    yL=yL,
    yU=yU) "y=0 is closed";
   assert(kThetaSqRt_nominal>0, "Flow coefficient must be strictly positive.");
   kDam_nominal :=sqrt(2*rho_nominal)*A/kThetaSqRt_nominal 
    "flow coefficient for resistance base model, kDam=k=m_flow/sqrt(dp)";
end Exponential;

Buildings.Fluid.Actuators.Dampers.VAVBoxExponential

VAV box with a fixed resistance plus a damper model withe exponential characteristics

Buildings.Fluid.Actuators.Dampers.VAVBoxExponential

Information

Model of two resistances in series. One resistance has a fixed flow coefficient, the other resistance is an air damper whose flow coefficient is an exponential function of the opening angle.

If dp_nominalIncludesDamper=true, then the parameter dp_nominal is equal to the pressure drop of the damper plus the fixed flow resistance at the nominal flow rate. If dp_nominalIncludesDamper=false, then dp_nominal does not include the flow resistance of the air damper.

Extends from Buildings.Fluid.Actuators.BaseClasses.PartialDamperExponential (Partial model for air dampers with exponential opening characteristics).

Parameters

Type Name Default Description

replaceable package Medium PartialMedium Medium in the component

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 use_v_nominal true Set to true to use face velocity to compute area

Velocity v_nominal 1 Nominal face velocity [m/s]

Area A m_flow_nominal/rho_nominal/v... Face area [m2]

Boolean roundDuct false Set to true for round duct, false for square cross section

Real ReC 4000 Reynolds number where transition to turbulent starts

Real kFixed sqrt(kResSqu) 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

MassFlowRate m_flow_nominal Nominal mass flow rate [kg/s]

Pressure dp_nominal Pressure drop at nominal mass flow rate [Pa]

Boolean dp_nominalIncludesDamper true set to true if dp_nominal includes the pressure loss of the open damper

Initialization

MassFlowRate m_flow.start 0 Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]

Assumptions

Boolean allowFlowReversal system.allowFlowReversal = true to allow flow reversal, false restricts to design direction (port_a -> port_b)

Advanced

MassFlowRate m_flow_small 1E-4*abs(m_flow_nominal) Small mass flow rate for regularization of zero flow [kg/s]

Boolean homotopyInitialization true = true, use homotopy method

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

Diagnostics

Boolean show_V_flow false = true, if volume flow rate at inflowing port is computed

Boolean show_T false = true, if actual temperature at port is computed (may lead to events)

Damper coefficients

Real a -1.51 Coefficient a for damper characteristics

Real b 0.105*90 Coefficient b for damper characteristics

Real yL 15/90 Lower value for damper curve

Real yU 55/90 Upper value for damper curve

Real k0 1E6 Flow coefficient for y=0, k0 = pressure drop divided by dynamic pressure

Real k1 0.45 Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure

Type	Name	Default	Description
replaceable package Medium	PartialMedium	Medium in the component
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	use_v_nominal	true	Set to true to use face velocity to compute area
Velocity	v_nominal	1	Nominal face velocity [m/s]
Area	A	m_flow_nominal/rho_nominal/v...	Face area [m2]
Boolean	roundDuct	false	Set to true for round duct, false for square cross section
Real	ReC	4000	Reynolds number where transition to turbulent starts
Real	kFixed	sqrt(kResSqu)	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
MassFlowRate	m_flow_nominal		Nominal mass flow rate [kg/s]
Pressure	dp_nominal		Pressure drop at nominal mass flow rate [Pa]
Boolean	dp_nominalIncludesDamper	true	set to true if dp_nominal includes the pressure loss of the open damper
Initialization
MassFlowRate	m_flow.start	0	Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
MassFlowRate	m_flow_small	1E-4*abs(m_flow_nominal)	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	homotopyInitialization	true	= true, use homotopy method
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
Diagnostics
Boolean	show_V_flow	false	= true, if volume flow rate at inflowing port is computed
Boolean	show_T	false	= true, if actual temperature at port is computed (may lead to events)
Damper coefficients
Real	a	-1.51	Coefficient a for damper characteristics
Real	b	0.105*90	Coefficient b for damper characteristics
Real	yL	15/90	Lower value for damper curve
Real	yU	55/90	Upper value for damper curve
Real	k0	1E6	Flow coefficient for y=0, k0 = pressure drop divided by dynamic pressure
Real	k1	0.45	Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure

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)

Modelica definition

model VAVBoxExponential 
  "VAV box with a fixed resistance plus a damper model withe exponential characteristics"
  extends Buildings.Fluid.Actuators.BaseClasses.PartialDamperExponential(
  dp(nominal=dp_nominal),
  final kFixed=sqrt(kResSqu));
  parameter Boolean dp_nominalIncludesDamper = true 
    "set to true if dp_nominal includes the pressure loss of the open damper";
protected 
  parameter Modelica.SIunits.Pressure dpDamOpe_nominal = k1*m_flow_nominal^2/2/Medium.density(sta0)/A^2 
    "Pressure drop of fully open damper at nominal flow rate";
  parameter Real kResSqu(unit="kg.m", fixed=false) 
    "Resistance coefficient for fixed resistance element";
initial equation 
  kResSqu = if dp_nominalIncludesDamper then 
       m_flow_nominal^2 / (dp_nominal-dpDamOpe_nominal) else 
       m_flow_nominal^2 / dp_nominal;
  assert(kResSqu > 0,
         "Wrong parameters in damper model: dp_nominal < dpDamOpe_nominal"
          + "\n  dp_nominal = "       + String(dp_nominal)
          + "\n  dpDamOpe_nominal = " + String(dpDamOpe_nominal));
end VAVBoxExponential;

Buildings.Fluid.Actuators.Dampers.MixingBox

Outside air mixing box with interlocked air dampers

Buildings.Fluid.Actuators.Dampers.MixingBox

Information

Model of an outside air mixing box with air dampers. Set y=0 to close the outside air and exhast air dampers.

Extends from Buildings.BaseClasses.BaseIconLow (Base icon with model name below the icon).

Parameters

Type Name Default Description

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 use_v_nominal true Set to true to use face velocity to compute area

Velocity v_nominal 1 Nominal face velocity [m/s]

Boolean roundDuct false Set to true for round duct, false for square cross section

Real ReC 4000 Reynolds number where transition to turbulent starts

Area AOut mOut_flow_nominal/rho_nomina... Face area outside air damper [m2]

Area AExh mExh_flow_nominal/rho_nomina... Face area exhaust air damper [m2]

Area ARec mRec_flow_nominal/rho_nomina... Face area recirculation air damper [m2]

Nominal condition

Boolean dp_nominalIncludesDamper false set to true if dp_nominal includes the pressure loss of the open damper

MassFlowRate mOut_flow_nominal Mass flow rate outside air damper [kg/s]

Pressure dpOut_nominal Pressure drop outside air leg [Pa]

MassFlowRate mRec_flow_nominal Mass flow rate recirculation air damper [kg/s]

Pressure dpRec_nominal Pressure drop recirculation air leg [Pa]

MassFlowRate mExh_flow_nominal Mass flow rate exhaust air damper [kg/s]

Pressure dpExh_nominal Pressure drop exhaust air leg [Pa]

Assumptions

Boolean allowFlowReversal system.allowFlowReversal = true to allow flow reversal, false restricts to design direction (port_a -> port_b)

Advanced

MassFlowRate m_flow_small 1E-4*mOut_flow_nominal Small mass flow rate for regularization of zero flow [kg/s]

Boolean from_dp true = 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

Damper coefficients

Real a -1.51 Coefficient a for damper characteristics

Real b 0.105*90 Coefficient b for damper characteristics

Real yL 15/90 Lower value for damper curve

Real yU 55/90 Upper value for damper curve

Real k0 1E6 Flow coefficient for y=0, k0 = pressure drop divided by dynamic pressure

Real k1 0.45 Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure

Type	Name	Default	Description
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	use_v_nominal	true	Set to true to use face velocity to compute area
Velocity	v_nominal	1	Nominal face velocity [m/s]
Boolean	roundDuct	false	Set to true for round duct, false for square cross section
Real	ReC	4000	Reynolds number where transition to turbulent starts
Area	AOut	mOut_flow_nominal/rho_nomina...	Face area outside air damper [m2]
Area	AExh	mExh_flow_nominal/rho_nomina...	Face area exhaust air damper [m2]
Area	ARec	mRec_flow_nominal/rho_nomina...	Face area recirculation air damper [m2]
Nominal condition
Boolean	dp_nominalIncludesDamper	false	set to true if dp_nominal includes the pressure loss of the open damper
MassFlowRate	mOut_flow_nominal		Mass flow rate outside air damper [kg/s]
Pressure	dpOut_nominal		Pressure drop outside air leg [Pa]
MassFlowRate	mRec_flow_nominal		Mass flow rate recirculation air damper [kg/s]
Pressure	dpRec_nominal		Pressure drop recirculation air leg [Pa]
MassFlowRate	mExh_flow_nominal		Mass flow rate exhaust air damper [kg/s]
Pressure	dpExh_nominal		Pressure drop exhaust air leg [Pa]
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
MassFlowRate	m_flow_small	1E-4*mOut_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	from_dp	true	= 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
Damper coefficients
Real	a	-1.51	Coefficient a for damper characteristics
Real	b	0.105*90	Coefficient b for damper characteristics
Real	yL	15/90	Lower value for damper curve
Real	yU	55/90	Upper value for damper curve
Real	k0	1E6	Flow coefficient for y=0, k0 = pressure drop divided by dynamic pressure
Real	k1	0.45	Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure

Connectors

Type Name Description

FluidPort_a port_Out Fluid connector a (positive design flow direction is from port_a to port_b)

FluidPort_b port_Exh Fluid connector b (positive design flow direction is from port_a to port_b)

FluidPort_a port_Ret Fluid connector a (positive design flow direction is from port_a to port_b)

FluidPort_b port_Sup Fluid connector b (positive design flow direction is from port_a to port_b)

input RealInput y Damper position (0: closed, 1: open)

Type	Name	Description
FluidPort_a	port_Out	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_Exh	Fluid connector b (positive design flow direction is from port_a to port_b)
FluidPort_a	port_Ret	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_Sup	Fluid connector b (positive design flow direction is from port_a to port_b)
input RealInput	y	Damper position (0: closed, 1: open)

Modelica definition

model MixingBox "Outside air mixing box with interlocked air dampers"
  extends Buildings.BaseClasses.BaseIconLow;
  outer Modelica.Fluid.System system "System wide properties";
  replaceable package Medium =
      Modelica.Media.Interfaces.PartialMedium "Medium in the component";
  import Modelica.Constants;

  parameter Boolean allowFlowReversal = system.allowFlowReversal 
    "= true to allow flow reversal, false restricts to design direction (port_a -> port_b)";

  VAVBoxExponential damOA(A=AOut,
    redeclare package Medium = Medium,
    dp_nominal=dpOut_nominal,
    dp_nominalIncludesDamper=dp_nominalIncludesDamper,
    from_dp=from_dp,
    linearized=linearized,
    use_deltaM=use_deltaM,
    deltaM=deltaM,
    use_v_nominal=use_v_nominal,
    v_nominal=v_nominal,
    roundDuct=roundDuct,
    ReC=ReC,
    m_flow_small=m_flow_small,
    a=a,
    b=b,
    yL=yL,
    yU=yU,
    k0=k0,
    k1=k1,
    use_constant_density=use_constant_density,
    allowFlowReversal=allowFlowReversal,
    m_flow_nominal=mOut_flow_nominal);
  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 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 Modelica.SIunits.Area AOut=mOut_flow_nominal/rho_nominal/v_nominal 
    "Face area outside air damper";
  VAVBoxExponential damExh(                            A=AExh,
    redeclare package Medium = Medium,
    m_flow_nominal=mExh_flow_nominal,
    dp_nominal=dpExh_nominal,
    dp_nominalIncludesDamper=dp_nominalIncludesDamper,
    from_dp=from_dp,
    linearized=linearized,
    use_deltaM=use_deltaM,
    deltaM=deltaM,
    use_v_nominal=use_v_nominal,
    v_nominal=v_nominal,
    roundDuct=roundDuct,
    ReC=ReC,
    m_flow_small=m_flow_small,
    a=a,
    b=b,
    yL=yL,
    yU=yU,
    k0=k0,
    k1=k1,
    use_constant_density=use_constant_density,
    allowFlowReversal=allowFlowReversal) "Exhaust air damper";
  parameter Modelica.SIunits.Area AExh=mExh_flow_nominal/rho_nominal/v_nominal 
    "Face area exhaust air damper";
  VAVBoxExponential damRec(                            A=ARec,
    redeclare package Medium = Medium,
    m_flow_nominal=mRec_flow_nominal,
    dp_nominal=dpRec_nominal,
    dp_nominalIncludesDamper=dp_nominalIncludesDamper,
    from_dp=from_dp,
    linearized=linearized,
    use_deltaM=use_deltaM,
    deltaM=deltaM,
    use_v_nominal=use_v_nominal,
    v_nominal=v_nominal,
    roundDuct=roundDuct,
    ReC=ReC,
    m_flow_small=m_flow_small,
    a=a,
    b=b,
    yL=yL,
    yU=yU,
    k0=k0,
    k1=k1,
    use_constant_density=use_constant_density,
    allowFlowReversal=allowFlowReversal) "Recirculation air damper";
  parameter Modelica.SIunits.Area ARec=mRec_flow_nominal/rho_nominal/v_nominal 
    "Face area recirculation air damper";

  parameter Boolean dp_nominalIncludesDamper=false 
    "set to true if dp_nominal includes the pressure loss of the open damper";

  parameter Modelica.SIunits.MassFlowRate mOut_flow_nominal 
    "Mass flow rate outside air damper";
  parameter Modelica.SIunits.Pressure dpOut_nominal(min=0, displayUnit="Pa") 
    "Pressure drop outside air leg";

  parameter Modelica.SIunits.MassFlowRate mRec_flow_nominal 
    "Mass flow rate recirculation air damper";
  parameter Modelica.SIunits.Pressure dpRec_nominal(min=0, displayUnit="Pa") 
    "Pressure drop recirculation air leg";

  parameter Modelica.SIunits.MassFlowRate mExh_flow_nominal 
    "Mass flow rate exhaust air damper";
  parameter Modelica.SIunits.Pressure dpExh_nominal(min=0, displayUnit="Pa") 
    "Pressure drop exhaust air leg";

  parameter Modelica.Media.Interfaces.PartialMedium.MassFlowRate m_flow_small=1E-4
      *mOut_flow_nominal "Small mass flow rate for regularization of zero flow";
  parameter Boolean from_dp=true 
    "= true, use m_flow = f(dp) else dp = f(m_flow)";
  parameter Boolean linearized=false 
    "= true, use linear relation between m_flow and dp for any flow rate";
  parameter Boolean use_constant_density=true 
    "Set to true to use constant density for flow friction";
  parameter Real a=-1.51 "Coefficient a for damper characteristics";
  parameter Real b=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=1E6 
    "Flow coefficient for y=0, k0 = pressure drop divided by dynamic pressure";
  parameter Real k1=0.45 
    "Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure";

  Modelica.Fluid.Interfaces.FluidPort_a port_Out(redeclare package Medium =
        Medium, m_flow(start=0, min=if allowFlowReversal then -Constants.inf else 
                0)) 
    "Fluid connector a (positive design flow direction is from port_a to port_b)";
  Modelica.Fluid.Interfaces.FluidPort_b port_Exh(redeclare package Medium =
        Medium, m_flow(start=0, max=if allowFlowReversal then +Constants.inf else 
                0)) 
    "Fluid connector b (positive design flow direction is from port_a to port_b)";
  Modelica.Fluid.Interfaces.FluidPort_a port_Ret(redeclare package Medium =
        Medium, m_flow(start=0, min=if allowFlowReversal then -Constants.inf else 
                0)) 
    "Fluid connector a (positive design flow direction is from port_a to port_b)";
  Modelica.Fluid.Interfaces.FluidPort_b port_Sup(redeclare package Medium =
        Medium, m_flow(start=0, max=if allowFlowReversal then +Constants.inf else 
                0)) 
    "Fluid connector b (positive design flow direction is from port_a to port_b)";
  Modelica.Blocks.Interfaces.RealInput y "Damper position (0: closed, 1: open)";
  Modelica.Blocks.Sources.Constant uni(k=1) "Unity signal";

  Modelica.Blocks.Math.Add add(k2=-1);

protected 
  parameter Medium.Density rho_nominal=Medium.density(sta_nominal) 
    "Density, used to compute fluid volume";
  parameter Medium.ThermodynamicState sta_nominal=
     Medium.setState_pTX(T=Medium.T_default, p=Medium.p_default, X=Medium.X_default);
equation 
  connect(y, damOA.y);
  connect(y, damExh.y);
  connect(uni.y, add.u1);
  connect(y, add.u2);
  connect(add.y, damRec.y);
  connect(damOA.port_a, port_Out);
  connect(damExh.port_b, port_Exh);
  connect(port_Sup, damOA.port_b);
  connect(damRec.port_b, port_Sup);
  connect(port_Ret, damExh.port_a);
  connect(port_Ret, damRec.port_a);
end MixingBox;

Buildings.Fluid.Actuators.Dampers.MixingBoxMinimumFlow

Outside air mixing box with parallel damper for minimum outside air flow rate

Buildings.Fluid.Actuators.Dampers.MixingBoxMinimumFlow

Information

Model of an outside air mixing box with air dampers and a flow path for the minimum outside air flow rate.

Extends from Buildings.Fluid.Actuators.Dampers.MixingBox (Outside air mixing box with interlocked air dampers).

Parameters

Type Name Default Description

replaceable package Medium PartialMedium Medium in the component

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 use_v_nominal true Set to true to use face velocity to compute area

Velocity v_nominal 1 Nominal face velocity [m/s]

Boolean roundDuct false Set to true for round duct, false for square cross section

Real ReC 4000 Reynolds number where transition to turbulent starts

Area AOut mOut_flow_nominal/rho_nomina... Face area outside air damper [m2]

Area AExh mExh_flow_nominal/rho_nomina... Face area exhaust air damper [m2]

Area ARec mRec_flow_nominal/rho_nomina... Face area recirculation air damper [m2]

Area AOutMin Face area minimum outside air damper [m2]

Nominal condition

Boolean dp_nominalIncludesDamper false set to true if dp_nominal includes the pressure loss of the open damper

MassFlowRate mOut_flow_nominal Mass flow rate outside air damper [kg/s]

Pressure dpOut_nominal Pressure drop outside air leg [Pa]

MassFlowRate mRec_flow_nominal Mass flow rate recirculation air damper [kg/s]

Pressure dpRec_nominal Pressure drop recirculation air leg [Pa]

MassFlowRate mExh_flow_nominal Mass flow rate exhaust air damper [kg/s]

Pressure dpExh_nominal Pressure drop exhaust air leg [Pa]

MassFlowRate mOutMin_flow_nominal Mass flow rate minimum outside air damper [kg/s]

Pressure dpOutMin_nominal Pressure drop minimum outside air leg [Pa]

Assumptions

Boolean allowFlowReversal system.allowFlowReversal = true to allow flow reversal, false restricts to design direction (port_a -> port_b)

Advanced

MassFlowRate m_flow_small 1E-4*mOut_flow_nominal Small mass flow rate for regularization of zero flow [kg/s]

Boolean from_dp true = 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

Damper coefficients

Real a -1.51 Coefficient a for damper characteristics

Real b 0.105*90 Coefficient b for damper characteristics

Real yL 15/90 Lower value for damper curve

Real yU 55/90 Upper value for damper curve

Real k0 1E6 Flow coefficient for y=0, k0 = pressure drop divided by dynamic pressure

Real k1 0.45 Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure

Type	Name	Default	Description
replaceable package Medium	PartialMedium	Medium in the component
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	use_v_nominal	true	Set to true to use face velocity to compute area
Velocity	v_nominal	1	Nominal face velocity [m/s]
Boolean	roundDuct	false	Set to true for round duct, false for square cross section
Real	ReC	4000	Reynolds number where transition to turbulent starts
Area	AOut	mOut_flow_nominal/rho_nomina...	Face area outside air damper [m2]
Area	AExh	mExh_flow_nominal/rho_nomina...	Face area exhaust air damper [m2]
Area	ARec	mRec_flow_nominal/rho_nomina...	Face area recirculation air damper [m2]
Area	AOutMin		Face area minimum outside air damper [m2]
Nominal condition
Boolean	dp_nominalIncludesDamper	false	set to true if dp_nominal includes the pressure loss of the open damper
MassFlowRate	mOut_flow_nominal		Mass flow rate outside air damper [kg/s]
Pressure	dpOut_nominal		Pressure drop outside air leg [Pa]
MassFlowRate	mRec_flow_nominal		Mass flow rate recirculation air damper [kg/s]
Pressure	dpRec_nominal		Pressure drop recirculation air leg [Pa]
MassFlowRate	mExh_flow_nominal		Mass flow rate exhaust air damper [kg/s]
Pressure	dpExh_nominal		Pressure drop exhaust air leg [Pa]
MassFlowRate	mOutMin_flow_nominal		Mass flow rate minimum outside air damper [kg/s]
Pressure	dpOutMin_nominal		Pressure drop minimum outside air leg [Pa]
Assumptions
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
MassFlowRate	m_flow_small	1E-4*mOut_flow_nominal	Small mass flow rate for regularization of zero flow [kg/s]
Boolean	from_dp	true	= 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
Damper coefficients
Real	a	-1.51	Coefficient a for damper characteristics
Real	b	0.105*90	Coefficient b for damper characteristics
Real	yL	15/90	Lower value for damper curve
Real	yU	55/90	Upper value for damper curve
Real	k0	1E6	Flow coefficient for y=0, k0 = pressure drop divided by dynamic pressure
Real	k1	0.45	Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure

Connectors

Type	Name	Description
FluidPort_a	port_Out	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_Exh	Fluid connector b (positive design flow direction is from port_a to port_b)
FluidPort_a	port_Ret	Fluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_b	port_Sup	Fluid connector b (positive design flow direction is from port_a to port_b)
input RealInput	y	Damper position (0: closed, 1: open)
FluidPort_a	port_OutMin	Fluid connector a (positive design flow direction is from port_a to port_b)
input RealInput	yOutMin	Damper position minimum outside air (0: closed, 1: open)

Modelica definition

model MixingBoxMinimumFlow 
  "Outside air mixing box with parallel damper for minimum outside air flow rate"
 extends Buildings.Fluid.Actuators.Dampers.MixingBox;
  import Modelica.Constants;

  parameter Modelica.SIunits.Area AOutMin 
    "Face area minimum outside air damper";

  parameter Modelica.SIunits.MassFlowRate mOutMin_flow_nominal 
    "Mass flow rate minimum outside air damper";
  parameter Modelica.SIunits.Pressure dpOutMin_nominal(min=0, displayUnit="Pa") 
    "Pressure drop minimum outside air leg";

  Modelica.Fluid.Interfaces.FluidPort_a port_OutMin(redeclare package Medium =
        Medium, m_flow(start=0, min=if allowFlowReversal then -Constants.inf else 
                0)) 
    "Fluid connector a (positive design flow direction is from port_a to port_b)";
  Modelica.Blocks.Interfaces.RealInput yOutMin 
    "Damper position minimum outside air (0: closed, 1: open)";

  VAVBoxExponential damOAMin(
    redeclare package Medium = Medium,
    dp_nominalIncludesDamper=dp_nominalIncludesDamper,
    from_dp=from_dp,
    linearized=linearized,
    use_deltaM=use_deltaM,
    deltaM=deltaM,
    use_v_nominal=use_v_nominal,
    v_nominal=v_nominal,
    roundDuct=roundDuct,
    ReC=ReC,
    m_flow_small=m_flow_small,
    a=a,
    b=b,
    yL=yL,
    yU=yU,
    k0=k0,
    k1=k1,
    use_constant_density=use_constant_density,
    allowFlowReversal=allowFlowReversal,
    m_flow_nominal=mOutMin_flow_nominal,
    dp_nominal=dpOutMin_nominal,
    A=AOutMin) "Damper for minimum outside air intake";
equation 
  connect(port_OutMin, damOAMin.port_a);
  connect(damOAMin.port_b, port_Sup);
  connect(yOutMin, damOAMin.y);
end MixingBoxMinimumFlow;

Automatically generated Fri Nov 4 08:27:07 2011.

	opposed blades	single blades
yL	15/90	15/90
yU	55/90	65/90
k0	1E6	1E6
k1	0.2 to 0.5	0.2 to 0.5
a	-1.51	-1.51
b	0.105*90	0.0842*90