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 |
PressureIndependent | Model for an air damper whose mass flow is proportional to the input signal |
Examples | Collection of models that illustrate model use and test models |
Validation | Collection of validation models |
Buildings.Fluid.Actuators.Dampers.Exponential
Air damper with exponential opening characteristics
Information
Model of two flow resistances in series:
- one resistance has a fixed flow coefficient;
- the other resistance represents a damper whose flow coefficient is an exponential function of the opening angle.
The lumped flow coefficient k(y) (function of the fractional opening y) is used to compute the mass flow rate versus pressure drop relation as:
ṁ = sign(Δp) k(y) √ Δp
with regularization near the origin.
For a description of the damper opening characteristics and typical parameter values, see the partial model Buildings.Fluid.Actuators.BaseClasses.PartialDamperExponential.
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 | 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 | |||
MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
PressureDifference | dpDamper_nominal | Pressure drop of fully open damper at nominal mass flow rate [Pa] | |
PressureDifference | dpFixed_nominal | 0 | Pressure drop of duct and resistances other than the damper in series, at nominal mass flow rate [Pa] |
Assumptions | |||
Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
Advanced | |||
Diagnostics | |||
Boolean | show_T | false | = true, if actual temperature at port is computed |
Boolean | from_dp | false | = true, use m_flow = f(dp) else dp = f(m_flow) |
Boolean | linearized | false | = true, use linear relation between m_flow and dp for any flow rate |
Boolean | use_constant_density | true | Set to true to use constant density for flow friction |
Dynamics | |||
Filtered opening | |||
Boolean | use_inputFilter | true | = true, if opening is filtered with a 2nd order CriticalDamping filter |
Time | riseTime | 120 | Rise time of the filter (time to reach 99.6 % of an opening step) [s] |
Integer | order | 2 | Order of filter |
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 [1] |
Real | b | 0.105*90 | Coefficient b for damper characteristics [1] |
Real | yL | 15/90 | Lower value for damper curve [1] |
Real | yU | 55/90 | Upper value for damper curve [1] |
Real | k1 | 0.45 | Loss coefficient for y=1 (pressure drop divided by dynamic pressure) [1] |
Real | l | 0.0001 | Damper leakage, ratio of flow coefficients k(y=0)/k(y=1) |
Connectors
Type | Name | Description |
---|---|---|
FluidPort_a | port_a | Fluid connector a (positive design flow direction is from port_a to port_b) |
FluidPort_b | port_b | Fluid connector b (positive design flow direction is from port_a to port_b) |
input RealInput | y | Actuator position (0: closed, 1: open) |
output RealOutput | y_actual | Actual actuator position |
Modelica definition
Buildings.Fluid.Actuators.Dampers.MixingBox
Outside air mixing box with interlocked air dampers
Information
Model of an outside air mixing box with exponential dampers.
Set y=0
to close the outside air and exhaust air dampers.
See
Buildings.Fluid.Actuators.Dampers.Exponential
for the description of the exponential damper model.
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 |
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 | |||
MassFlowRate | mOut_flow_nominal | Mass flow rate outside air damper [kg/s] | |
PressureDifference | dpDamOut_nominal | dpDamOut_nominal(min=0, disp... | Pressure drop of damper in outside air leg [Pa] |
PressureDifference | dpFixOut_nominal | 0 | Pressure drop of duct and other resistances in outside air leg [Pa] |
MassFlowRate | mRec_flow_nominal | Mass flow rate recirculation air damper [kg/s] | |
PressureDifference | dpDamRec_nominal | dpDamRec_nominal(min=0, disp... | Pressure drop of damper in recirculation air leg [Pa] |
PressureDifference | dpFixRec_nominal | 0 | Pressure drop of duct and other resistances in recirculation air leg [Pa] |
MassFlowRate | mExh_flow_nominal | Mass flow rate exhaust air damper [kg/s] | |
PressureDifference | dpDamExh_nominal | dpDamExh_nominal(min=0, disp... | Pressure drop of damper in exhaust air leg [Pa] |
PressureDifference | dpFixExh_nominal | 0 | Pressure drop of duct and other resistances in 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] |
Integer | order | 2 | Order of filter |
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 | k1 | 0.45 | Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure |
Real | l | 0.0001 | Damper leakage, ratio of flow coefficients k(y=0)/k(y=1) |
Connectors
Type | Name | Description |
---|---|---|
input RealInput | y | Actuator position (0: closed, 1: open) |
output RealOutput | y_actual | Actual actuator 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
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 |
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 | |||
MassFlowRate | mOut_flow_nominal | Mass flow rate outside air damper [kg/s] | |
PressureDifference | dpDamOut_nominal | Pressure drop of damper in outside air leg [Pa] | |
PressureDifference | dpFixOut_nominal | 0 | Pressure drop of duct and other resistances in outside air leg [Pa] |
MassFlowRate | mRec_flow_nominal | Mass flow rate recirculation air damper [kg/s] | |
PressureDifference | dpDamRec_nominal | Pressure drop of damper in recirculation air leg [Pa] | |
PressureDifference | dpFixRec_nominal | 0 | Pressure drop of duct and other resistances in recirculation air leg [Pa] |
MassFlowRate | mExh_flow_nominal | Mass flow rate exhaust air damper [kg/s] | |
PressureDifference | dpDamExh_nominal | Pressure drop of damper in exhaust air leg [Pa] | |
PressureDifference | dpFixExh_nominal | 0 | Pressure drop of duct and other resistances in exhaust air leg [Pa] |
MassFlowRate | mOutMin_flow_nominal | Mass flow rate minimum outside air damper [kg/s] | |
PressureDifference | dpDamOutMin_nominal | dpDamOutMin_nominal(min=0, d... | Pressure drop of damper in minimum outside air leg [Pa] |
PressureDifference | dpFixOutMin_nominal | 0 | Pressure drop of duct and other resistances in 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] |
Integer | order | 2 | Order of filter |
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 | k1 | 0.45 | Flow coefficient for y=1, k1 = pressure drop divided by dynamic pressure |
Real | l | 0.0001 | Damper leakage, ratio of flow coefficients k(y=0)/k(y=1) |
Connectors
Type | Name | Description |
---|---|---|
input RealInput | y | Actuator position (0: closed, 1: open) |
output RealOutput | y_actual | Actual actuator 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
Buildings.Fluid.Actuators.Dampers.PressureIndependent
Model for an air damper whose mass flow is proportional to the input signal
Information
Model for an air damper whose airflow is proportional to the input signal, assuming
that at y = 1
, m_flow = m_flow_nominal
. This is unless the pressure difference
dp
is too low,
in which case a kDam = m_flow_nominal/sqrt(dp_nominal)
characteristic is used.
The model is similar to Buildings.Fluid.Actuators.Valves.TwoWayPressureIndependent, except for adaptations for damper parameters. Please see that documentation for more information.
Computation of the damper opening
The fractional opening of the damper is computed by
- inverting the quadratic flow function to compute the flow coefficient from the flow rate and the pressure drop values (under the assumption of a turbulent flow regime);
- inverting the exponential characteristics to compute the fractional opening from the loss coefficient value (directly derived from the flow coefficient).
The quadratic interpolation used outside the exponential domain in the function Buildings.Fluid.Actuators.BaseClasses.exponentialDamper yields a local extremum. Therefore, the formal inversion of the function is not possible. A cubic spline is used instead to fit the inverse of the damper characteristics. The central domain of the characteritics having a monotonous exponential profile, its inverse can be properly approximated with three equidistant support points. However, the quadratic functions used outside of the exponential domain can have various profiles depending on the damper coefficients. Therefore, five linearly distributed support points are used on each side domain to ensure a good fit of the inverse.
Note that below a threshold value of the input control signal (fixed at 0.02), the fractional opening is forced to zero and no more related to the actual flow coefficient of the damper. This avoids steep transients of the computed opening while transitioning from reverse flow. This is to be considered as a modeling workaround (avoiding the introduction of an additional state variable) to prevent control chattering during shut off operation where the pressure difference at the damper boundaries can vary between slightly positive and negative values due to outdoor pressure variations.
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 | 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 | |||
MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
PressureDifference | dpDamper_nominal | Pressure drop of fully open damper at nominal mass flow rate [Pa] | |
PressureDifference | dpFixed_nominal | 0 | Pressure drop of duct and resistances other than the damper in series, at nominal mass flow rate [Pa] |
Assumptions | |||
Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
Advanced | |||
Diagnostics | |||
Boolean | show_T | false | = true, if actual temperature at port is computed |
Boolean | from_dp | 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 |
Real | l2 | 0.01 | Gain for mass flow increase if pressure is above nominal pressure [1] |
Real | deltax | 0.02 | Transition interval for flow rate [1] |
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] |
Integer | order | 2 | Order of filter |
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 [1] |
Real | b | 0.105*90 | Coefficient b for damper characteristics [1] |
Real | yL | 15/90 | Lower value for damper curve [1] |
Real | yU | 55/90 | Upper value for damper curve [1] |
Real | k1 | 0.45 | Loss coefficient for y=1 (pressure drop divided by dynamic pressure) [1] |
Real | l | 0.0001 | Damper leakage, ratio of flow coefficients k(y=0)/k(y=1) |
Connectors
Type | Name | Description |
---|---|---|
FluidPort_a | port_a | Fluid connector a (positive design flow direction is from port_a to port_b) |
FluidPort_b | port_b | Fluid connector b (positive design flow direction is from port_a to port_b) |
input RealInput | y | Actuator position (0: closed, 1: open) |
output RealOutput | y_actual | Actual actuator position |