Buildings.Fluid.Actuators.Dampers
Package with air damper models
Information
This package contains component 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 |
 MixingBox
|
Outside air mixing box with interlocked air dampers |
 MixingBoxMinimumFlow
|
Outside air mixing box with parallel damper for minimum outside air flow rate |
 VAVBoxExponential
|
VAV box with a fixed resistance plus a damper model withe exponential characteristics |
 Examples
|
Collection of models that illustrate model use and test models |
Buildings.Fluid.Actuators.Dampers.Exponential
Air damper with exponential opening characteristics
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
kd(y) = 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
kd(y) is
differentiable in y and the derivative is continuous.
The damper characteristics kd(y) is then used to compute the flow coefficient k(y) as
k(y) = (2 ρ ⁄ kd(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. The flow coefficient k(y)
is used to compute the mass flow rate versus pressure
drop relation as
m = sign(Δp) k(y) √ Δp
with regularization near the origin.
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 | |
| 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 |
| 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 |
| 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] | |
| PressureDifference | dp_nominal | (m_flow_nominal/kDam_default... | Pressure drop 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 | homotopyInitialization | true | = true, use homotopy method |
| 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 value of output |
| 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) |
| output RealOutput | y_actual | Actual valve position |
Modelica definition
model Exponential "Air damper with exponential opening characteristics"
extends Buildings.Fluid.Actuators.BaseClasses.PartialDamperExponential(
final dp_nominal=(m_flow_nominal/kDam_default)^2,
dp(nominal=10),
final kFixed=0);
protected
parameter Real kDam_default = sqrt(2*rho_default)*A/kThetaSqRt_default
"Flow coefficient for damper, k=m_flow/sqrt(dp), with unit=(kg*m)^(1/2)";
parameter Real kThetaSqRt_default(min=0)=
Buildings.Fluid.Actuators.BaseClasses.exponentialDamper(
y=1,
a=a,
b=b,
cL=cL,
cU=cU,
yL=yL,
yU=yU)
"Flow coefficient, kThetaSqRt = sqrt(pressure drop divided by dynamic pressure)";
initial algorithm
assert(kThetaSqRt_default>0, "Flow coefficient must be strictly positive.");
end Exponential;
Buildings.Fluid.Actuators.Dampers.MixingBox
Outside air mixing box with interlocked air dampers
Information
Model of an outside air mixing box with air dampers.
Set y=0 to close the outside air and exhast air dampers.
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.ActuatorSignal (Partial model that implements the filtered opening for valves and dampers).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | Modelica.Media.Interfaces.Pa... | 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 |
| 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 |
| 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] | |
| PressureDifference | dpOut_nominal | Pressure drop outside air leg [Pa] | |
| MassFlowRate | mRec_flow_nominal | Mass flow rate recirculation air damper [kg/s] | |
| PressureDifference | dpRec_nominal | Pressure drop recirculation air leg [Pa] | |
| MassFlowRate | mExh_flow_nominal | Mass flow rate exhaust air damper [kg/s] | |
| PressureDifference | dpExh_nominal | Pressure drop exhaust air leg [Pa] | |
| 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 value of output |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Advanced | |||
| 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 |
|---|---|---|
| input RealInput | y | Actuator position (0: closed, 1: open) |
| output RealOutput | y_actual | Actual valve position |
| replaceable package Medium | Medium in the component | |
| 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) |
Modelica definition
model MixingBox "Outside air mixing box with interlocked air dampers"
extends Buildings.Fluid.Actuators.BaseClasses.ActuatorSignal;
replaceable package Medium =
Modelica.Media.Interfaces.PartialMedium "Medium in the component";
import Modelica.Constants;
parameter Boolean allowFlowReversal = true
"= false to simplify equations, assuming, but not enforcing, no flow reversal";
VAVBoxExponential damOA(
redeclare package Medium = Medium,
dp_nominal=dpOut_nominal,
dp_nominalIncludesDamper=dp_nominalIncludesDamper,
from_dp=from_dp,
linearized=linearized,
use_deltaM=use_deltaM,
deltaM=deltaM,
roundDuct=roundDuct,
ReC=ReC,
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,
final use_inputFilter=false);
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 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";
VAVBoxExponential damExh(
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,
roundDuct=roundDuct,
ReC=ReC,
a=a,
b=b,
yL=yL,
yU=yU,
k0=k0,
k1=k1,
use_constant_density=use_constant_density,
allowFlowReversal=allowFlowReversal,
final use_inputFilter=false) "Exhaust air damper";
VAVBoxExponential damRec(
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,
roundDuct=roundDuct,
ReC=ReC,
a=a,
b=b,
yL=yL,
yU=yU,
k0=k0,
k1=k1,
use_constant_density=use_constant_density,
allowFlowReversal=allowFlowReversal,
final use_inputFilter=false) "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.PressureDifference 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.PressureDifference 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.PressureDifference dpExh_nominal(min=0, displayUnit="Pa")
"Pressure drop exhaust air leg";
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.Sources.Constant uni(k=1) "Unity signal";
Modelica.Blocks.Math.Add add(k2=-1) "Adder";
protected
parameter Medium.Density rho_default=Medium.density(sta_default)
"Density, used to compute fluid volume";
parameter Medium.ThermodynamicState sta_default=
Medium.setState_pTX(T=Medium.T_default, p=Medium.p_default, X=Medium.X_default)
"Default medium state";
equation
connect(uni.y, add.u1);
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);
connect(y_actual, add.u2);
connect(y_actual, damOA.y);
connect(y_actual, damExh.y);
end MixingBox;
Buildings.Fluid.Actuators.Dampers.MixingBoxMinimumFlow
Outside air mixing box with parallel damper for minimum outside air flow rate
Information
Model of an outside air mixing box with air dampers and a flow path for the minimum outside air flow rate.
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.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 |
| 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 |
| 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] | |
| PressureDifference | dpOut_nominal | Pressure drop outside air leg [Pa] | |
| MassFlowRate | mRec_flow_nominal | Mass flow rate recirculation air damper [kg/s] | |
| PressureDifference | dpRec_nominal | Pressure drop recirculation air leg [Pa] | |
| MassFlowRate | mExh_flow_nominal | Mass flow rate exhaust air damper [kg/s] | |
| PressureDifference | dpExh_nominal | Pressure drop exhaust air leg [Pa] | |
| MassFlowRate | mOutMin_flow_nominal | Mass flow rate minimum outside air damper [kg/s] | |
| PressureDifference | dpOutMin_nominal | Pressure drop minimum outside air leg [Pa] | |
| 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 value of output |
| Real | yOutMin_start | y_start | Initial value of signal for minimum outside air damper |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Advanced | |||
| 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 |
|---|---|---|
| input RealInput | y | Actuator position (0: closed, 1: open) |
| output RealOutput | y_actual | Actual valve position |
| 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) |
| 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) |
| output RealOutput | yOutMin_actual | Actual valve position |
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;
final parameter Modelica.SIunits.Area AOutMin = mOutMin_flow_nominal/rho_default/v_nominal
"Face area minimum outside air damper";
parameter Modelica.SIunits.MassFlowRate mOutMin_flow_nominal
"Mass flow rate minimum outside air damper";
parameter Modelica.SIunits.PressureDifference dpOutMin_nominal(min=0,
displayUnit="Pa")
"Pressure drop minimum outside air leg";
parameter Real yOutMin_start=y_start
"Initial value of signal for minimum outside air damper";
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)";
Modelica.Blocks.Interfaces.RealOutput yOutMin_actual "Actual valve position";
Buildings.Fluid.Actuators.Dampers.VAVBoxExponential damOAMin(
redeclare package Medium = Medium,
dp_nominalIncludesDamper=dp_nominalIncludesDamper,
from_dp=from_dp,
linearized=linearized,
use_deltaM=use_deltaM,
deltaM=deltaM,
v_nominal=v_nominal,
roundDuct=roundDuct,
ReC=ReC,
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,
final use_inputFilter=false) "Damper for minimum outside air intake";
protected
Modelica.Blocks.Interfaces.RealOutput yOutMin_filtered if use_inputFilter
"Filtered damper position in the range 0..1";
Modelica.Blocks.Continuous.Filter filterOutMin(
order=2,
f_cut=5/(2*Modelica.Constants.pi*riseTime),
final init=init,
final y_start=yOutMin_start,
final analogFilter=Modelica.Blocks.Types.AnalogFilter.CriticalDamping,
final filterType=Modelica.Blocks.Types.FilterType.LowPass,
x(each stateSelect=StateSelect.always)) if
use_inputFilter
"Second order filter to approximate valve opening time, and to improve numerics";
equation
connect(filterOutMin.y, yOutMin_filtered);
if use_inputFilter then
connect(yOutMin, filterOutMin.u);
connect(filterOutMin.y, yOutMin_actual);
else
connect(yOutMin, yOutMin_actual);
end if;
//////
connect(port_OutMin, damOAMin.port_a);
connect(damOAMin.port_b, port_Sup);
connect(yOutMin_actual, damOAMin.y);
end MixingBoxMinimumFlow;
Buildings.Fluid.Actuators.Dampers.VAVBoxExponential
VAV box with a fixed resistance plus a damper model withe exponential characteristics
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 | |
| 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 |
| 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 |
| 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] | |
| PressureDifference | 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 |
| 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 | homotopyInitialization | true | = true, use homotopy method |
| 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 value of output |
| 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) |
| output RealOutput | y_actual | Actual valve position |
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.PressureDifference dpDamOpe_nominal(displayUnit="Pa")=
k1*m_flow_nominal^2/2/Medium.density(sta_default)/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;