Description: "Collection of models that illustrate model use and test models"

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## Buildings.Airflow.Multizone.Examples

Collection of models that illustrate model use and test models

### Information

This package contains examples for the use of models that can be found in Buildings.Airflow.Multizone.

Extends from Modelica.Icons.ExamplesPackage (Icon for packages containing runnable examples).

### Package Content

Name | Description
--- | ---
CO2TransportStep | Model that transport CO2 through buoyancy driven flow
ChimneyShaftNoVolume | Model that demonstrates the chimney effect with a steady-state model of a shaft
ChimneyShaftWithVolume | Model that demonstrates the chimney effect with a dynamic model of a shaft
ClosedDoors | Model with three closed doors
NaturalVentilation | Test model for flow reversal due to density difference
OneEffectiveAirLeakageArea | Model with an effective air leakage area
OneOpenDoor | Model with one open and one closed door
OneRoom | Model with one room for the validation of the multizone air exchange models
Orifice | Model with an orifice
ReverseBuoyancy | Model with four rooms and buoyancy-driven air circulation that reverses direction
ReverseBuoyancy3Zones | Model with three rooms and buoyancy-driven air circulation that reverses direction
ZonalFlow | Model with prescribed air exchange between two volumes

## Buildings.Airflow.Multizone.Examples.CO2TransportStep

Model that transport CO2 through buoyancy driven flow

### Information

This model is based on Buildings.Airflow.Multizone.Validation.ThreeRoomsContam. In addition, a CO2 source has been added to the left room in the bottom floor. At initial time, all volumes have zero CO2 concentration. At t=3600 seconds, CO2 is added to `volWes`. As time progresses, the CO2 is transported to the other rooms, and eventually its concentration decays.

Extends from Buildings.Airflow.Multizone.Validation.ThreeRoomsContam (Model with three rooms for the validation of the multizone air exchange models).

### Modelica definition

model CO2TransportStep "Model that transport CO2 through buoyancy driven flow" extends Buildings.Airflow.Multizone.Validation.ThreeRoomsContam( volWes(nPorts=5), volTop(nPorts=3), volEas(nPorts=6)); Fluid.Sensors.TraceSubstances CO2SenTop(redeclare package Medium = Medium) "CO2 sensor"; Fluid.Sensors.TraceSubstances CO2SenWes(redeclare package Medium = Medium) "CO2 sensor"; Fluid.Sensors.TraceSubstances CO2SenEas(redeclare package Medium = Medium) "CO2 sensor"; Modelica.Blocks.Sources.Pulse pulse( amplitude=8.18E-6, width=1/24/10, period=86400, startTime=3600); Fluid.Sources.TraceSubstancesFlowSource sou( redeclare package Medium = Medium, use_m_flow_in=true, nPorts=1) "CO2 source"; equation connect(sou.m_flow_in, pulse.y); connect(sou.ports[1], volWes.ports[4]); connect(CO2SenWes.port, volWes.ports[5]); connect(CO2SenTop.port, volTop.ports[3]); connect(CO2SenEas.port, volEas.ports[6]); end CO2TransportStep;

## Buildings.Airflow.Multizone.Examples.ChimneyShaftNoVolume

Model that demonstrates the chimney effect with a steady-state model of a shaft

### Information

This model demonstrate buoyancy-induced air flow through a vertical shaft. On the right, there are two flow paths that are connected to a volume, which is kept at 20°C through a feedback controller, and to the ambient, which is at 0°C. The flow path on the very right consists of an orifice and two models that compute the pressure difference Δp between the bottom and top of the medium column using Δp=h ρ g, where h is the height of the medium column, ρ is the density of the medium column and g is the gravity constant.

The top model is parameterized to use the density from the ambient, whereas the bottom model is parameterized to use the density from the room volume, regardless of the flow direction. In the other flow path, the model `sha` is parameterized to use the density of the inflowing medium. Thus, these models can be thought of as a chimney to the left, and a roof with a leakage on the right. The chimney height starts 1.5 m below the roof, and ends 1.5 m above the roof.

The flow boundary condition of the model `boundary` is such that at the start of the simulation, air flows from `boundary` to `roo` until t=600 seconds. Then, the flow rate is set to zero until t=1800 seconds. Since the shaft `sha` is filled with 20°C air, there is a circulation in the clock-wise direction; up the shaft, and down the other flow path. Next, until t=2400 seconds, air is extracted from the volume `roo`, and then the flow rate of `bondary` is set to zero. Since the shaft `sha` is now filed with air at 0°C, there is a counter clock-wise flow; down the shaft, and up the other flow path.

Extends from Modelica.Icons.Example (Icon for runnable examples).

### Modelica definition

model ChimneyShaftNoVolume "Model that demonstrates the chimney effect with a steady-state model of a shaft" extends Modelica.Icons.Example; package Medium = Modelica.Media.Air.SimpleAir; Fluid.MixingVolumes.MixingVolume roo( V=2.5*5*5, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, T_start=273.15 + 20, redeclare package Medium = Medium, m_flow_nominal=0.05, p_start=101325, nPorts=3) "Air volume of a room"; Buildings.Airflow.Multizone.Orifice oriChiTop( m=0.5, redeclare package Medium = Medium, A=0.01); Buildings.Fluid.Sources.MassFlowSource_T boundary( redeclare package Medium = Medium, use_m_flow_in=true, T=293.15, nPorts=1); Buildings.Fluid.Sources.Boundary_pT bou0( redeclare package Medium = Medium, T=273.15, nPorts=2); Buildings.Airflow.Multizone.Orifice oriBot( m=0.5, redeclare package Medium = Medium, A=0.01); Modelica.Blocks.Sources.CombiTimeTable mRoo_flow(tableOnFile=false, table=[0, 0.05; 600,0.05; 601,0; 1800,0; 1801,-0.05; 2400,-0.05; 2401,0; 3600,0]) "Mass flow into and out of room to fill the medium column with air of different temperature"; MediumColumn staOut( redeclare package Medium = Medium, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromTop, h=1.5) "Model for stack effect outside the room"; Buildings.Airflow.Multizone.Orifice oriChiBot( m=0.5, redeclare package Medium = Medium, A=0.01); Buildings.HeatTransfer.Sources.PrescribedHeatFlow preHea "Prescribed heat flow"; Buildings.Controls.Continuous.LimPID con( Td=10, yMax=1, yMin=-1, Ti=60, controllerType=Modelica.Blocks.Types.SimpleController.P, k=5) "Controller to maintain volume temperature"; Modelica.Blocks.Sources.Constant TSet(k=293.15) "Temperature set point"; Modelica.Thermal.HeatTransfer.Sensors.TemperatureSensor temSen "Temperature sensor"; Modelica.Blocks.Math.Gain gain(k=3000); Buildings.Airflow.Multizone.MediumColumn sha(redeclare package Medium = Medium, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.actual) "Shaft of chimney"; MediumColumn staIn( redeclare package Medium = Medium, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom, h=1.5) "Model for stack effect inside the room"; equation connect(TSet.y, con.u_s); connect(temSen.T, con.u_m); connect(gain.u, con.y); connect(gain.y, preHea.Q_flow); connect(sha.port_a, oriChiTop.port_a); connect(sha.port_b, oriChiBot.port_b); connect(staOut.port_b, oriBot.port_a); connect(preHea.port, roo.heatPort); connect(roo.heatPort, temSen.port); connect(bou0.ports[1], oriChiTop.port_b); connect(bou0.ports[2], staOut.port_a); connect(oriBot.port_b, staIn.port_a); connect(mRoo_flow.y[1], boundary.m_flow_in); connect(boundary.ports[1], roo.ports[1]); connect(roo.ports[2], staIn.port_b); connect(roo.ports[3], oriChiBot.port_a); end ChimneyShaftNoVolume;

## Buildings.Airflow.Multizone.Examples.ChimneyShaftWithVolume

Model that demonstrates the chimney effect with a dynamic model of a shaft

### Information

This model is identical to Buildings.Airflow.Multizone.Examples.ChimneyShaftNoVolume, except that the chimney model is not steady-state, but rather dynamic as it contains an air volume. The air volume is approximated as being well-mixed. (Stratified volumes could be approximated by using multiple instances of the model `sha` that are connected in series.)

Extends from Modelica.Icons.Example (Icon for runnable examples).

### Modelica definition

model ChimneyShaftWithVolume "Model that demonstrates the chimney effect with a dynamic model of a shaft" extends Modelica.Icons.Example; package Medium = Buildings.Media.Air; Fluid.MixingVolumes.MixingVolume roo( V=2.5*5*5, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, T_start=273.15 + 20, redeclare package Medium = Medium, m_flow_nominal=0.05, p_start=101325, nPorts=3) "Air volume of a room"; Buildings.Airflow.Multizone.Orifice oriChiTop( m=0.5, redeclare package Medium = Medium, A=0.01); Buildings.Fluid.Sources.MassFlowSource_T boundary( redeclare package Medium = Medium, use_m_flow_in=true, T=293.15, nPorts=1); Buildings.Fluid.Sources.Boundary_pT bou0( redeclare package Medium = Medium, T=273.15, nPorts=2); Buildings.Airflow.Multizone.Orifice oriBot( m=0.5, redeclare package Medium = Medium, A=0.01); Modelica.Blocks.Sources.CombiTimeTable mRoo_flow(tableOnFile=false, table=[0, 0.05; 600,0.05; 601,0; 1800,0; 1801,-0.05; 2400,-0.05; 2401,0; 3600,0]) "Mass flow into and out of room to fill the medium column with air of different temperature"; MediumColumn staOut( redeclare package Medium = Medium, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromTop, h=1.5) "Model for stack effect outside the room"; Buildings.Airflow.Multizone.Orifice oriChiBot( m=0.5, redeclare package Medium = Medium, A=0.01); Buildings.HeatTransfer.Sources.PrescribedHeatFlow preHea "Prescribed heat flow"; Buildings.Controls.Continuous.LimPID con( Td=10, yMax=1, yMin=-1, Ti=60, controllerType=Modelica.Blocks.Types.SimpleController.P, k=5) "Controller to maintain volume temperature"; Modelica.Blocks.Sources.Constant TSet(k=293.15) "Temperature set point"; Modelica.Thermal.HeatTransfer.Sensors.TemperatureSensor temSen "Temperature sensor"; Modelica.Blocks.Math.Gain gain(k=3000); Buildings.Airflow.Multizone.MediumColumnDynamic sha(redeclare package Medium = Medium, m_flow_nominal=0.05, V=3, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial) "Shaft of chimney"; MediumColumn staIn( redeclare package Medium = Medium, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom, h=1.5) "Model for stack effect inside the room"; equation connect(TSet.y, con.u_s); connect(temSen.T, con.u_m); connect(gain.u, con.y); connect(gain.y, preHea.Q_flow); connect(sha.port_a, oriChiTop.port_a); connect(sha.port_b, oriChiBot.port_b); connect(staOut.port_b, oriBot.port_a); connect(preHea.port, roo.heatPort); connect(roo.heatPort, temSen.port); connect(bou0.ports[1], oriChiTop.port_b); connect(bou0.ports[2], staOut.port_a); connect(oriBot.port_b, staIn.port_a); connect(mRoo_flow.y[1], boundary.m_flow_in); connect(boundary.ports[1], roo.ports[1]); connect(roo.ports[2], staIn.port_b); connect(roo.ports[3], oriChiBot.port_a); end ChimneyShaftWithVolume;

## Buildings.Airflow.Multizone.Examples.ClosedDoors

Model with three closed doors

### Information

This model consists of three volumes that are connected among each other through three doors that all have the same geometry. All doors are closed, but they are not air-tight. Heat is added and removed from `volB` which induces a small air flow through the doors.

This model uses Buildings.Media.Specialized.Air.PerfectGas as the medium because Buildings.Media.Air does not account for expansion if air the air is heated.

Extends from Modelica.Icons.Example (Icon for runnable examples).

### Modelica definition

model ClosedDoors "Model with three closed doors" extends Modelica.Icons.Example; package Medium = Buildings.Media.Specialized.Air.PerfectGas; Buildings.Airflow.Multizone.DoorDiscretizedOperable dooAB( redeclare package Medium = Medium, LClo=20*1E-4, forceErrorControlOnFlow=true) "Discretized door"; Buildings.Fluid.MixingVolumes.MixingVolume volA( redeclare package Medium = Medium, V=2.5*5*5, nPorts=4, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, m_flow_nominal=0.01); Buildings.Fluid.MixingVolumes.MixingVolume volB( redeclare package Medium = Medium, V=2.5*5*5, nPorts=4, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, m_flow_nominal=0.01); Buildings.HeatTransfer.Sources.PrescribedHeatFlow PrescribedHeatFlow1; Modelica.Blocks.Sources.Sine Sine1(freqHz=1/3600); Modelica.Blocks.Math.Gain Gain1(k=100); Buildings.Fluid.MixingVolumes.MixingVolume volC( redeclare package Medium = Medium, V=2.5*5*5, nPorts=4, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, m_flow_nominal=0.01); Buildings.Airflow.Multizone.DoorDiscretizedOperable dooAC( redeclare package Medium = Medium, LClo=20*1E-4, forceErrorControlOnFlow=true) "Discretized door"; Modelica.Blocks.Sources.Constant yDoor(k=0) "Input signal for door opening"; Buildings.Airflow.Multizone.DoorDiscretizedOperable dooBC( redeclare package Medium = Medium, LClo=20*1E-4, forceErrorControlOnFlow=true) "Discretized door"; equation connect(Gain1.y, PrescribedHeatFlow1.Q_flow); connect(Sine1.y, Gain1.u); connect(yDoor.y, dooAB.y); connect(yDoor.y, dooAC.y); connect(yDoor.y, dooBC.y); connect(PrescribedHeatFlow1.port, volB.heatPort); connect(volC.ports[1], dooAC.port_b1); connect(volC.ports[2], dooAC.port_a2); connect(volC.ports[3], dooBC.port_b1); connect(volC.ports[4], dooBC.port_a2); connect(volB.ports[1], dooAB.port_b1); connect(volB.ports[2], dooAB.port_a2); connect(volB.ports[3], dooBC.port_a1); connect(volB.ports[4], dooBC.port_b2); connect(volA.ports[1], dooAC.port_b2); connect(volA.ports[2], dooAC.port_a1); connect(volA.ports[3], dooAB.port_b2); connect(volA.ports[4], dooAB.port_a1); end ClosedDoors;

## Buildings.Airflow.Multizone.Examples.NaturalVentilation

Test model for flow reversal due to density difference

### Information

This model illustrates buoyancy-driven natural ventilation between two volumes of air. The volume `volA` can be considered as the volume of a room, and the volume `volOut` is parameterized to be very large to emulate outside air. The outside air is 20°C and at initial time, the room air is 18°C. This induces an airflow in counter clock-wise direction. Since heat is added to the room air volume, its temperature raises above the temperature of the outside, which causes the air flow to reverse its direction.

Extends from Modelica.Icons.Example (Icon for runnable examples).

### Modelica definition

model NaturalVentilation "Test model for flow reversal due to density difference" extends Modelica.Icons.Example; package Medium = Buildings.Media.Air; Buildings.Fluid.MixingVolumes.MixingVolume volA( redeclare package Medium = Medium, V=2.5*10*5, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, T_start=273.15 + 18, nPorts=2, m_flow_nominal=0.001); Buildings.Airflow.Multizone.Orifice oriOutBot( redeclare package Medium = Medium, A=0.1, m=0.5, dp_turbulent=0.1); Buildings.Airflow.Multizone.MediumColumn colOut( redeclare package Medium = Medium, h=3, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom); Buildings.Airflow.Multizone.Orifice oriOutTop( redeclare package Medium = Medium, A=0.1, m=0.5, dp_turbulent=0.1); Buildings.Airflow.Multizone.MediumColumn colRooTop( redeclare package Medium = Medium, h=3, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom); Buildings.Fluid.MixingVolumes.MixingVolume volOut( redeclare package Medium = Medium, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, V=1E10, T_start=273.15 + 20, nPorts=2, m_flow_nominal=0.001); Buildings.HeatTransfer.Sources.PrescribedHeatFlow preHeaFlo; Modelica.Blocks.Sources.Step q_flow( height=-100, offset=100, startTime=3600); equation connect(q_flow.y, preHeaFlo.Q_flow); connect(oriOutBot.port_b, volOut.ports[1]); connect(preHeaFlo.port, volA.heatPort); connect(volA.ports[1], oriOutBot.port_a); connect(volA.ports[2], colRooTop.port_b); connect(colRooTop.port_a, oriOutTop.port_a); connect(volOut.ports[2], colOut.port_b); connect(colOut.port_a, oriOutTop.port_b); end NaturalVentilation;

## Buildings.Airflow.Multizone.Examples.OneEffectiveAirLeakageArea

Model with an effective air leakage area

### Information

This model consists of a model for an effective air leakage area that is connected to two air volumes. Air flows due to the addition of air to the volume `volA` and because heat is exchanged with `volB`.

Extends from Modelica.Icons.Example (Icon for runnable examples).

### Modelica definition

model OneEffectiveAirLeakageArea "Model with an effective air leakage area" extends Modelica.Icons.Example; package Medium = Buildings.Media.Air; Buildings.Fluid.MixingVolumes.MixingVolume volA( redeclare package Medium = Medium, V=2.5*5*5, nPorts=2, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, m_flow_nominal=0.01); Buildings.Fluid.MixingVolumes.MixingVolume volB( redeclare package Medium = Medium, V=2.5*5*5, nPorts=1, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, m_flow_nominal=0.01); Buildings.HeatTransfer.Sources.PrescribedHeatFlow preHeaFlo; Modelica.Blocks.Sources.Sine Sine1(freqHz=1/3600); Modelica.Blocks.Math.Gain Gain1(k=100); Buildings.Airflow.Multizone.EffectiveAirLeakageArea cra(redeclare package Medium = Medium, L=20E-4); Buildings.Fluid.Sources.MassFlowSource_T sou( redeclare package Medium = Medium, nPorts=1, use_m_flow_in=true); Modelica.Blocks.Sources.Ramp ramSou( duration=3600, height=0.01, offset=0, startTime=1800); equation connect(sou.ports[1], volA.ports[1]); connect(ramSou.y, sou.m_flow_in); connect(volB.ports[1], cra.port_b); connect(volA.ports[2], cra.port_a); connect(preHeaFlo.port, volB.heatPort); connect(Gain1.y, preHeaFlo.Q_flow); connect(Gain1.u, Sine1.y); end OneEffectiveAirLeakageArea;

## Buildings.Airflow.Multizone.Examples.OneOpenDoor

Model with one open and one closed door

### Information

This model consists of two doors with the same geometry. For t ≤ 1000 seconds, the door `dooOpeClo` is closed, and afterwards it is open. The door `dooOpe` is always open. Heat is added to the volume `volB`, which causes a density difference between `volA` and `volB`. This density difference induces a bi-directional airflow through both doors. Both doors have exactly the same bi-directional airflow rates.

Extends from Modelica.Icons.Example (Icon for runnable examples).

### Modelica definition

model OneOpenDoor "Model with one open and one closed door" extends Modelica.Icons.Example; package Medium = Modelica.Media.Air.SimpleAir; Buildings.Airflow.Multizone.DoorDiscretizedOpen dooOpe(redeclare package Medium = Medium) "Discretized door"; Buildings.Fluid.MixingVolumes.MixingVolume volA( redeclare package Medium = Medium, V=2.5*5*5, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, nPorts=4, m_flow_nominal=0.01); Buildings.Fluid.MixingVolumes.MixingVolume volB( redeclare package Medium = Medium, V=2.5*5*5, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, nPorts=4, m_flow_nominal=0.01); Buildings.HeatTransfer.Sources.PrescribedHeatFlow preHeaFlo; Modelica.Blocks.Sources.Sine heaSou(freqHz=1/3600); Modelica.Blocks.Math.Gain Gain1(k=100); Buildings.Airflow.Multizone.DoorDiscretizedOperable dooOpeClo(redeclare package Medium = Medium, LClo=20*1E-4) "Discretized door"; Modelica.Blocks.Sources.Ramp ramp( duration=120, height=1, offset=0, startTime=1000); equation connect(Gain1.y, preHeaFlo.Q_flow); connect(heaSou.y, Gain1.u); connect(ramp.y, dooOpeClo.y); connect(preHeaFlo.port, volB.heatPort); connect(volA.ports[1], dooOpeClo.port_b2); connect(volA.ports[2], dooOpeClo.port_a1); connect(volA.ports[3], dooOpe.port_b2); connect(volA.ports[4], dooOpe.port_a1); connect(volB.ports[1], dooOpe.port_b1); connect(volB.ports[2], dooOpe.port_a2); connect(volB.ports[3], dooOpeClo.port_b1); connect(volB.ports[4], dooOpeClo.port_a2); end OneOpenDoor;

## Buildings.Airflow.Multizone.Examples.OneRoom

Model with one room for the validation of the multizone air exchange models

### Information

This model has been used to validate buoyancy-driven air flow between two volumes. The volume `volEas` is at 20°C and the volume `volOut` is at 10°C. This initial condition induces a clock-wise airflow between the two volumes.

Extends from Modelica.Icons.Example (Icon for runnable examples).

### Modelica definition

model OneRoom "Model with one room for the validation of the multizone air exchange models" extends Modelica.Icons.Example; package Medium = Buildings.Media.Air; Buildings.Fluid.MixingVolumes.MixingVolume volEas( redeclare package Medium = Medium, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, T_start=273.15 + 20, V=2.5*5*5, nPorts=2, m_flow_nominal=0.001, massDynamics=Modelica.Fluid.Types.Dynamics.SteadyStateInitial); Buildings.Airflow.Multizone.Orifice oriOutBot( redeclare package Medium = Medium, A=0.01, m=0.5); Buildings.Airflow.Multizone.MediumColumn colOutTop( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom); Buildings.Airflow.Multizone.Orifice oriOutTop( redeclare package Medium = Medium, A=0.01, m=0.5); Buildings.Airflow.Multizone.MediumColumn colEasInTop( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom); Buildings.Fluid.MixingVolumes.MixingVolume volOut( redeclare package Medium = Medium, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, T_start=273.15 + 10, V=1E12, p_start=Medium.p_default, nPorts=2, m_flow_nominal=0.001, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial); Buildings.Airflow.Multizone.MediumColumn colEasInBot( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromTop); Buildings.Airflow.Multizone.MediumColumn colOutBot( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromTop); equation connect(colEasInTop.port_a, oriOutTop.port_a); connect(colEasInTop.port_b, volEas.ports[1]); connect(colEasInBot.port_a, volEas.ports[2]); connect(colEasInBot.port_b, oriOutBot.port_a); connect(oriOutBot.port_b, colOutBot.port_b); connect(colOutBot.port_a, volOut.ports[1]); connect(colOutTop.port_b, volOut.ports[2]); connect(colOutTop.port_a, oriOutTop.port_b); end OneRoom;

## Buildings.Airflow.Multizone.Examples.Orifice

Model with an orifice

### Information

This model demonstrates the use of the orifice model. The pressure difference across the orifice model changes between -1 Pascal and +1 Pascal, which causes air to flow through the orifice.

Extends from Modelica.Icons.Example (Icon for runnable examples).

### Modelica definition

model Orifice "Model with an orifice" extends Modelica.Icons.Example; package Medium = Buildings.Media.Air; Buildings.Airflow.Multizone.Orifice ori(redeclare package Medium = Medium, A= 0.2); Buildings.Fluid.Sources.Boundary_pT roo1( redeclare package Medium = Medium, use_p_in=true, nPorts=1, T=278.15); Buildings.Fluid.Sources.Boundary_pT roo2( redeclare package Medium = Medium, use_p_in=true, nPorts=1, T=293.15); Modelica.Blocks.Sources.Ramp Ramp1( duration=0.5, height=2, offset=-1, startTime=0.25); Modelica.Blocks.Sources.Constant Pre(k=100000); Modelica.Blocks.Math.Add Add1; Fluid.Sensors.DensityTwoPort den1(redeclare package Medium = Medium, m_flow_nominal=0.1, initType=Modelica.Blocks.Types.Init.InitialState) "Density sensor"; Fluid.Sensors.DensityTwoPort den2(redeclare package Medium = Medium, m_flow_nominal=0.1, initType=Modelica.Blocks.Types.Init.InitialState) "Density sensor"; equation connect(Pre.y, Add1.u1); connect(Ramp1.y, Add1.u2); connect(Pre.y, roo1.p_in); connect(Add1.y, roo2.p_in); connect(roo1.ports[1], den1.port_a); connect(den1.port_b, ori.port_a); connect(ori.port_b, den2.port_a); connect(den2.port_b, roo2.ports[1]); end Orifice;

## Buildings.Airflow.Multizone.Examples.ReverseBuoyancy

Model with four rooms and buoyancy-driven air circulation that reverses direction

### Information

This model is similar than Buildings.Airflow.Multizone.Validation.ThreeRoomsContam but it has four instead of three rooms. The outdoor conditions are held constant at 10°C and atmospheric pressure. All four rooms are at different temperatures, with the rooms on the bottom floor being initially at a higher temperature than the rooms on the bottom floor. As time progresses, the temperatures of the two rooms on the respective floors asymptotically approach each other. The bottom floor eventually cools below the temperature of the top floor, because the bottom floor directly exchanges air with the outside.

Extends from Modelica.Icons.Example (Icon for runnable examples).

### Modelica definition

model ReverseBuoyancy "Model with four rooms and buoyancy-driven air circulation that reverses direction" extends Modelica.Icons.Example; package Medium = Buildings.Media.Air; Buildings.Fluid.MixingVolumes.MixingVolume volBotEas( redeclare package Medium = Medium, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, V=2.5*5*5, T_start=273.15 + 25, nPorts=5, m_flow_nominal=0.001) "Volume of bottom floor, east room"; Buildings.Airflow.Multizone.Orifice oriOutBot( redeclare package Medium = Medium, m=0.5, A=0.01, dp_turbulent=0.1); Buildings.Airflow.Multizone.MediumColumn colOutTop( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom); Buildings.Airflow.Multizone.Orifice oriOutTop( redeclare package Medium = Medium, m=0.5, A=0.01, dp_turbulent=0.1); Buildings.Airflow.Multizone.MediumColumn colEasInTop( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom); Buildings.Airflow.Multizone.MediumColumn colEasInBot( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromTop); Buildings.Airflow.Multizone.MediumColumn colOutBot( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromTop); MediumColumn colWesBot( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom); Buildings.Airflow.Multizone.Orifice oriWesTop( redeclare package Medium = Medium, m=0.5, A=0.01, dp_turbulent=0.1); Buildings.Airflow.Multizone.MediumColumn colWesTop( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromTop); Buildings.Airflow.Multizone.DoorDiscretizedOperable dooOpeClo( redeclare package Medium = Medium, LClo=20*1E-4, wOpe=1, hOpe=2.2, hA=3/2, hB=3/2, CDOpe=0.78, CDClo=0.78, nCom=10, vZer=0.01, dp_turbulent=0.1) "Discretized door"; Buildings.Fluid.Delays.DelayFirstOrder volBotWes( redeclare package Medium = Medium, m_flow_nominal=1.2, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, tau=2.5*5*5, T_start=273.15 + 22, nPorts=3, p_start=101325) "Volume of bottom floor, west room"; Modelica.Blocks.Sources.Constant ope(k=1); Buildings.Airflow.Multizone.MediumColumn col1EasBot( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom); Buildings.Airflow.Multizone.Orifice oriEasTop( redeclare package Medium = Medium, m=0.5, A=0.01, dp_turbulent=0.1); Buildings.Airflow.Multizone.MediumColumn colEasTop( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromTop); Buildings.Fluid.MixingVolumes.MixingVolume volTopEas( redeclare package Medium = Medium, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, V=2.5*5*10, T_start=273.15 + 21, nPorts=3, m_flow_nominal=0.001) "Volume of top floor, east room"; Buildings.Fluid.MixingVolumes.MixingVolume volTopWes( redeclare package Medium = Medium, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, T_start=273.15 + 20, V=2.5*5*10, nPorts=3, m_flow_nominal=0.001) "Volume of top floor, west room"; Buildings.Airflow.Multizone.DoorDiscretizedOperable dooOpeCloTop( redeclare package Medium = Medium, LClo=20*1E-4, wOpe=1, hOpe=2.2, hA=3/2, hB=3/2, CDOpe=0.78, CDClo=0.78, nCom=10, vZer=0.01, dp_turbulent=0.1) "Discretized door"; Fluid.Sources.FixedBoundary volOut( redeclare package Medium = Medium, p=100000, T=283.15, nPorts=2) "Ambient conditions"; equation connect(ope.y, dooOpeClo.y); connect(ope.y, dooOpeCloTop.y); connect(oriEasTop.port_b, colEasTop.port_b); connect(oriWesTop.port_b, colWesBot.port_a); connect(oriWesTop.port_a, colWesTop.port_b); connect(oriOutBot.port_b, colOutBot.port_b); connect(colEasInBot.port_b, oriOutBot.port_a); connect(colEasInTop.port_a, oriOutTop.port_a); connect(oriOutTop.port_b, colOutTop.port_a); connect(volBotWes.ports[1], dooOpeClo.port_b2); connect(volBotWes.ports[2], dooOpeClo.port_a1); connect(colWesBot.port_b, volBotWes.ports[3]); connect(volTopWes.ports[1], colWesTop.port_a); connect(volTopWes.ports[2], dooOpeCloTop.port_b2); connect(volTopWes.ports[3], dooOpeCloTop.port_a1); connect(volTopEas.ports[1], dooOpeCloTop.port_b1); connect(dooOpeCloTop.port_a2, volTopEas.ports[2]); connect(colEasTop.port_a, volTopEas.ports[3]); connect(oriEasTop.port_a, col1EasBot.port_a); connect(dooOpeClo.port_b1, volBotEas.ports[1]); connect(dooOpeClo.port_a2, volBotEas.ports[2]); connect(colEasInBot.port_a, volBotEas.ports[3]); connect(colEasInTop.port_b, volBotEas.ports[4]); connect(col1EasBot.port_b, volBotEas.ports[5]); connect(colOutBot.port_a, volOut.ports[1]); connect(colOutTop.port_b, volOut.ports[2]); end ReverseBuoyancy;

## Buildings.Airflow.Multizone.Examples.ReverseBuoyancy3Zones

Model with three rooms and buoyancy-driven air circulation that reverses direction

### Information

This model is similar than Buildings.Airflow.Multizone.Validation.ThreeRoomsContam. However, the initial temperatures are such that at the start of the simulation, the flow direction between the three rooms reverses direction.

At the start of the simulation, the outdoor temperature is 15°C, and the temperatures of the volumes are 20°C at the top, 22°C at the bottom west and 25°C at the bottom east. Thus, initially there is a net flow circulation in the counter-clock direction. Because the volume on the east exchanges air with the outside, it cools down fast. Once it cooled down sufficiently, the flow direction between the three rooms reverses because the air in the bottom east is heaviest.

Extends from Modelica.Icons.Example (Icon for runnable examples).

### Modelica definition

model ReverseBuoyancy3Zones "Model with three rooms and buoyancy-driven air circulation that reverses direction" extends Modelica.Icons.Example; package Medium = Buildings.Media.Air; Buildings.Fluid.MixingVolumes.MixingVolume volEas( redeclare package Medium = Medium, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, V=2.5*5*5, T_start=273.15 + 25, nPorts=5, m_flow_nominal=0.001); Buildings.Airflow.Multizone.Orifice oriOutBot( redeclare package Medium = Medium, m=0.5, A=0.01, dp_turbulent=0.1); Buildings.Airflow.Multizone.MediumColumn colOutTop( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom); Buildings.Airflow.Multizone.Orifice oriOutTop( redeclare package Medium = Medium, m=0.5, A=0.01, dp_turbulent=0.1); Buildings.Airflow.Multizone.MediumColumn colEasInTop( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom); Buildings.Fluid.MixingVolumes.MixingVolume volOut( redeclare package Medium = Medium, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, V=1E12, T_start=273.15 + 15, nPorts=2, m_flow_nominal=0.001); Buildings.Airflow.Multizone.MediumColumn colEasInBot( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromTop); Buildings.Airflow.Multizone.MediumColumn colOutBot( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromTop); Buildings.Airflow.Multizone.MediumColumn colWesBot( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom); Buildings.Airflow.Multizone.Orifice oriWesTop( redeclare package Medium = Medium, m=0.5, A=0.01, dp_turbulent=0.1); Buildings.Airflow.Multizone.MediumColumn colWesTop( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromTop); Buildings.Airflow.Multizone.DoorDiscretizedOperable dooOpeClo( redeclare package Medium = Medium, LClo=20*1E-4, wOpe=1, hOpe=2.2, hA=3/2, hB=3/2, CDOpe=0.78, CDClo=0.78, nCom=10, vZer=0.01, dp_turbulent=0.1) "Discretized door"; Modelica.Blocks.Sources.Constant ope(k=1); Buildings.Airflow.Multizone.MediumColumn col1EasBot( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom); Buildings.Airflow.Multizone.Orifice oriEasTop( redeclare package Medium = Medium, m=0.5, A=0.01, dp_turbulent=0.1); Buildings.Airflow.Multizone.MediumColumn colEasTop( redeclare package Medium = Medium, h=1.5, densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromTop); Buildings.Fluid.MixingVolumes.MixingVolume volTop( redeclare package Medium = Medium, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, T_start=273.15 + 20, m_flow_nominal=0.001, V=2.5*10*10, nPorts=2); Buildings.Fluid.MixingVolumes.MixingVolume volWes( redeclare package Medium = Medium, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, massDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial, V=2.5*5*5, T_start=273.15 + 22, nPorts=3, m_flow_nominal=0.001); equation connect(dooOpeClo.port_b2, volWes.ports[1]); connect(dooOpeClo.port_a1, volWes.ports[2]); connect(dooOpeClo.port_b1, volEas.ports[1]); connect(dooOpeClo.port_a2, volEas.ports[2]); connect(colWesTop.port_b, oriWesTop.port_a); connect(oriWesTop.port_b, colWesBot.port_a); connect(colWesBot.port_b, volWes.ports[3]); connect(colEasTop.port_b, oriEasTop.port_b); connect(oriEasTop.port_a, col1EasBot.port_a); connect(colEasInBot.port_a, volEas.ports[3]); connect(colEasInTop.port_b, volEas.ports[4]); connect(col1EasBot.port_b, volEas.ports[5]); connect(colOutTop.port_b, volOut.ports[1]); connect(volOut.ports[2], colOutBot.port_a); connect(colOutBot.port_b, oriOutBot.port_b); connect(oriOutBot.port_a, colEasInBot.port_b); connect(colEasInTop.port_a, oriOutTop.port_a); connect(oriOutTop.port_b, colOutTop.port_a); connect(ope.y, dooOpeClo.y); connect(colWesTop.port_a, volTop.ports[1]); connect(colEasTop.port_a, volTop.ports[2]); end ReverseBuoyancy3Zones;

## Buildings.Airflow.Multizone.Examples.ZonalFlow

Model with prescribed air exchange between two volumes

### Information

This example illustrates the use of the model that exchanges a prescribed air exchange rate between the volumes that are attached to it. The constant block prescribes the air exchange rate to 5 air changes per hour. This amount of air flows from `rooA` to `rooB`, and from `rooB` to `rooA`.

Extends from Modelica.Icons.Example (Icon for runnable examples).

### Parameters

Type | Name | Default | Description
--- | --- | --- | ---
Volume | volA | 100 | Volume of room A [m3]
Volume | volB | 1 | Volume of room B [m3]

### Modelica definition

model ZonalFlow "Model with prescribed air exchange between two volumes" extends Modelica.Icons.Example; package Medium = Buildings.Media.Air; parameter Modelica.SIunits.Volume volA=100 "Volume of room A"; parameter Modelica.SIunits.Volume volB=1 "Volume of room B"; Buildings.Fluid.MixingVolumes.MixingVolume rooA( V=volA, redeclare package Medium = Medium, X_start={0.015,0.985}, T_start=303.15, nPorts=2, m_flow_nominal=0.001, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial) "Room A"; Buildings.Fluid.MixingVolumes.MixingVolume rooB( V=volB, redeclare package Medium = Medium, X_start={0.01,0.99}, T_start=293.15, nPorts=2, m_flow_nominal=0.001, energyDynamics=Modelica.Fluid.Types.Dynamics.FixedInitial) "Room B"; Modelica.Blocks.Sources.Constant ACS_con(k=5/3600); ZonalFlow_ACS zonFlo(redeclare package Medium = Medium, V=min(volA, volB)); equation connect(rooA.ports[1], zonFlo.port_a1); connect(zonFlo.port_b1, rooB.ports[1]); connect(zonFlo.port_b2, rooA.ports[2]); connect(zonFlo.port_a2, rooB.ports[2]); connect(zonFlo.ACS, ACS_con.y); end ZonalFlow;