modelMixingBox

Outside air mixing box with interlocked air dampers

Extends from AixLib.Fluid.Actuators.BaseClasses.ActuatorSignal (Partial model that implements the filtered opening for valves and 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 AixLib.Fluid.Actuators.Dampers.Exponential for the description of the exponential damper model.

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	roundDuct	false	Set to true for round duct, false for square cross section
Real	ReC	4000	Reynolds number where transition to turbulence starts
Dynamics › Actuator position
Boolean	use_strokeTime (from ActuatorSignal)	true	Set to true to continuously open and close valve using strokeTime
Modelica.Units.SI.Time	strokeTime (from ActuatorSignal)	120	Time needed to fully open or close actuator
Modelica.Blocks.Types.Init	init (from ActuatorSignal)	Modelica.Blocks.Types.Init.InitialOutput	Type of initialization (no init/steady state/initial state/initial output)
Real	y_start (from ActuatorSignal)	1	Initial position of actuator
Assumptions
Boolean	allowFlowReversal	true	= false to simplify equations, assuming, but not enforcing, no flow reversal
Nominal condition
Modelica.Units.SI.MassFlowRate	mOut_flow_nominal		Mass flow rate outside air damper
Modelica.Units.SI.PressureDifference	dpDamOut_nominal		Pressure drop of damper in outside air leg
Modelica.Units.SI.PressureDifference	dpFixOut_nominal	0	Pressure drop of duct and other resistances in outside air leg
Modelica.Units.SI.MassFlowRate	mRec_flow_nominal		Mass flow rate recirculation air damper
Modelica.Units.SI.PressureDifference	dpDamRec_nominal		Pressure drop of damper in recirculation air leg
Modelica.Units.SI.PressureDifference	dpFixRec_nominal	0	Pressure drop of duct and other resistances in recirculation air leg
Modelica.Units.SI.MassFlowRate	mExh_flow_nominal		Mass flow rate exhaust air damper
Modelica.Units.SI.PressureDifference	dpDamExh_nominal		Pressure drop of damper in exhaust air leg
Modelica.Units.SI.PressureDifference	dpFixExh_nominal	0	Pressure drop of duct and other resistances in exhaust air leg
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
Modelica.Blocks.Interfaces.RealInput	y (from ActuatorSignal)	Actuator position (0: closed, 1: open)
Modelica.Blocks.Interfaces.RealOutput	y_actual (from ActuatorSignal)	Actual actuator position
Modelica.Fluid.Interfaces.FluidPort_a	port_Out	Fluid connector a (positive design flow direction is from port_a to port_b)
Modelica.Fluid.Interfaces.FluidPort_b	port_Exh	Fluid connector b (positive design flow direction is from port_a to port_b)
Modelica.Fluid.Interfaces.FluidPort_a	port_Ret	Fluid connector a (positive design flow direction is from port_a to port_b)
Modelica.Fluid.Interfaces.FluidPort_b	port_Sup	Fluid connector b (positive design flow direction is from port_a to port_b)

Components

Type	Name	Description
AixLib.Fluid.Actuators.Dampers.Exponential	damOA	Outdoor air damper
AixLib.Fluid.Actuators.Dampers.Exponential	damExh	Exhaust air damper
AixLib.Fluid.Actuators.Dampers.Exponential	damRec	Recirculation air damper
Modelica.Blocks.Sources.Constant	uni	Unity signal
Modelica.Blocks.Math.Add	add	Adder

Name	Description
Medium	Medium in the component

Revisions

February 7, 2025, by Jelger Jansen:
Removed import statement. This is for IBPSA, #1961.
September 21, 2021, by Michael Wetter:
Corrected typo in comments.
This is for #1525.
June 10, 2021, by Michael Wetter:
Changed implementation of the filter and changed the parameter order to a constant as most users need not change this value.
This is for #1498.
December 23, 2019, by Antoine Gautier:
Updated parameter bindings consistently with refactoring of AixLib.Fluid.Actuators.BaseClasses.PartialDamperExponential.
This is for #1188.
January 18, 2019, by Jianjun Hu:
Limited the media choice to moist air only. See #1050.
March 24, 2017, by Michael Wetter:
Renamed filteredInput to use_inputFilter.
This is for #665.
March 22, 2017, by Michael Wetter:
Removed the assignments of AOut, AExh and ARec as these are done in the damper instance using a final assignment of the parameter. This allows scaling the model with m_flow_nominal, which is generally known in the flow leg, and v_nominal, for which a default value can be specified.
This is for #544.
January 22, 2016, by Michael Wetter:
Corrected type declaration of pressure difference. This is for #404.
December 14, 2012 by Michael Wetter:
Renamed protected parameters for consistency with the naming conventions.
February 14, 2012 by Michael Wetter:
Added filter to approximate the travel time of the actuator.
February 3, 2012, by Michael Wetter:
Removed assignment of m_flow_small as it is no longer used in its base class.
February 23, 2010 by Michael Wetter:
First implementation.