Buildings.Airflow.Multizone
Package with models for multizone airflow and contaminant transport
Information
This package provides models to compute the airflow and contaminant transport between different rooms and between a room and the exterior environment. See the User's Guide for more information.Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).
Package Content
| Name | Description |
|---|---|
 UsersGuide
|
User's Guide |
 DoorDiscretizedOpen
|
Door model using discretization along height coordinate |
 DoorDiscretizedOperable
|
Door model using discretization along height coordinate |
 EffectiveAirLeakageArea
|
Effective air leakage area |
 MediumColumn
|
Vertical shaft with no friction and no storage of heat and mass |
 MediumColumnDynamic
|
Vertical shaft with no friction and storage of heat and mass |
 Orifice
|
Orifice |
 ZonalFlow_ACS
|
Zonal flow with input air change per second |
 ZonalFlow_m_flow
|
Zonal flow with input air change per second |
 Types
|
Package with type definitions |
 Examples
|
Collection of models that illustrate model use and test models |
| Validation
|
Collection of validation models |
 BaseClasses
|
Package with base classes for Buildings.Airflow.Multizone |
Buildings.Airflow.Multizone.DoorDiscretizedOpen
Door model using discretization along height coordinate
Information
This model describes the bi-directional air flow through an open door.
To compute the bi-directional flow, the door is discretize along the height coordinate. An orifice equation is used to compute the flow for each compartment.
In this model, the door is always open. Use the model Buildings.Airflow.Multizone.DoorDiscretizedOperable for a door that can either be open or closed.
Extends from Buildings.Airflow.Multizone.BaseClasses.DoorDiscretized (Door model using discretization along height coordinate).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | forceErrorControlOnFlow | true | Flag to force error control on m_flow. Set to true if interested in flow rate |
| replaceable package Medium | PartialMedium | ||
| Velocity | vZer | 0.001 | Minimum velocity to prevent zero flow. Recommended: 0.001 [m/s] |
| Integer | nCom | 10 | Number of compartments for the discretization |
| PressureDifference | dp_turbulent | 0.01 | Pressure difference where laminar and turbulent flow relation coincide. Recommended: 0.01 [Pa] |
| Geometry | |||
| Length | wOpe | 0.9 | Width of opening [m] |
| Length | hOpe | 2.1 | Height of opening [m] |
| Length | hA | 2.7/2 | Height of reference pressure zone A [m] |
| Length | hB | 2.7/2 | Height of reference pressure zone B [m] |
| Orifice characteristics | |||
| Real | CD | 0.65 | Discharge coefficient |
| Advanced | |||
| MassFlowRate | m1_flow_small | 1E-4*abs(m1_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| MassFlowRate | m2_flow_small | 1E-4*abs(m2_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPort_a | port_a1 | Fluid connector a1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_b | port_b1 | Fluid connector b1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_a | port_a2 | Fluid connector a2 (positive design flow direction is from port_a2 to port_b2) |
| FluidPort_b | port_b2 | Fluid connector b2 (positive design flow direction is from port_a2 to port_b2) |
Modelica definition
model DoorDiscretizedOpen
"Door model using discretization along height coordinate"
extends Buildings.Airflow.Multizone.BaseClasses.DoorDiscretized;
protected
constant Real mFixed = 0.5 "Fixed value for flow coefficient";
constant Real gamma(min=1) = 1.5
"Normalized flow rate where dphi(0)/dpi intersects phi(1)";
constant Real a = gamma
"Polynomial coefficient for regularized implementation of flow resistance";
constant Real b = 1/8*mFixed^2 - 3*gamma - 3/2*mFixed + 35.0/8
"Polynomial coefficient for regularized implementation of flow resistance";
constant Real c = -1/4*mFixed^2 + 3*gamma + 5/2*mFixed - 21.0/4
"Polynomial coefficient for regularized implementation of flow resistance";
constant Real d = 1/8*mFixed^2 - gamma - mFixed + 15.0/8
"Polynomial coefficient for regularized implementation of flow resistance";
equation
m=mFixed;
A = wOpe*hOpe;
kVal = CD*dA*sqrt(2/rho_default);
// orifice equation
for i in 1:nCom loop
dV_flow[i] = Buildings.Airflow.Multizone.BaseClasses.powerLawFixedM(
k=kVal,
dp=dpAB[i],
m=mFixed,
a=a,
b=b,
c=c,
d=d,
dp_turbulent=dp_turbulent);
end for;
end DoorDiscretizedOpen;
Buildings.Airflow.Multizone.DoorDiscretizedOperable
Door model using discretization along height coordinate
Information
This model describes the bi-directional air flow through an open door.
To compute the bi-directional flow, the door is discretize along the height coordinate, and uses an orifice equation to compute the flow for each compartment.
The door can be either open or closed, depending on the input signal y. Set y=0 if the door is closed, and y=1 if the door is open. Use the model Buildings.Airflow.Multizone.DoorDiscretizedOpen for a door that is always closed.
Extends from Buildings.Airflow.Multizone.BaseClasses.DoorDiscretized (Door model using discretization along height coordinate).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | forceErrorControlOnFlow | true | Flag to force error control on m_flow. Set to true if interested in flow rate |
| replaceable package Medium | PartialMedium | ||
| Velocity | vZer | 0.001 | Minimum velocity to prevent zero flow. Recommended: 0.001 [m/s] |
| Integer | nCom | 10 | Number of compartments for the discretization |
| PressureDifference | dp_turbulent | 0.01 | Pressure difference where laminar and turbulent flow relation coincide. Recommended: 0.01 [Pa] |
| Geometry | |||
| Length | wOpe | 0.9 | Width of opening [m] |
| Length | hOpe | 2.1 | Height of opening [m] |
| Length | hA | 2.7/2 | Height of reference pressure zone A [m] |
| Length | hB | 2.7/2 | Height of reference pressure zone B [m] |
| Orifice characteristics | |||
| Real | CD | 0.65 | Discharge coefficient |
| Closed aperture rating conditions | |||
| PressureDifference | dpCloRat | 4 | Pressure drop at rating condition [Pa] |
| Real | CDCloRat | 1 | Discharge coefficient |
| Closed aperture | |||
| Area | LClo | Effective leakage area [m2] | |
| Real | CDClo | 0.65 | Discharge coefficient |
| Real | mClo | 0.65 | Flow exponent for crack |
| Open aperture | |||
| Real | CDOpe | 0.65 | Discharge coefficient |
| Real | mOpe | 0.5 | Flow exponent for door |
| Advanced | |||
| MassFlowRate | m1_flow_small | 1E-4*abs(m1_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| MassFlowRate | m2_flow_small | 1E-4*abs(m2_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPort_a | port_a1 | Fluid connector a1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_b | port_b1 | Fluid connector b1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_a | port_a2 | Fluid connector a2 (positive design flow direction is from port_a2 to port_b2) |
| FluidPort_b | port_b2 | Fluid connector b2 (positive design flow direction is from port_a2 to port_b2) |
| input RealInput | y | Opening signal, 0=closed, 1=open [1] |
Modelica definition
model DoorDiscretizedOperable
"Door model using discretization along height coordinate"
extends Buildings.Airflow.Multizone.BaseClasses.DoorDiscretized;
parameter Modelica.SIunits.PressureDifference dpCloRat(min=0,
displayUnit="Pa") = 4
"|Closed aperture rating conditions|Pressure drop at rating condition";
parameter Real CDCloRat(min=0, max=1)=1
"|Closed aperture rating conditions|Discharge coefficient";
parameter Modelica.SIunits.Area LClo(min=0)
"|Closed aperture|Effective leakage area";
parameter Real CDOpe=0.65 "|Open aperture|Discharge coefficient";
parameter Real CDClo=0.65 "|Closed aperture|Discharge coefficient";
parameter Real mOpe = 0.5 "|Open aperture|Flow exponent for door";
parameter Real mClo= 0.65 "|Closed aperture|Flow exponent for crack";
Modelica.Blocks.Interfaces.RealInput y(min=0, max=1, unit="1")
"Opening signal, 0=closed, 1=open";
protected
parameter Modelica.SIunits.Area AOpe=wOpe*hOpe "Open aperture area";
parameter Modelica.SIunits.Area AClo(fixed=false) "Closed aperture area";
Real kOpe "Open aperture flow coefficient, k = V_flow/ dp^m";
Real kClo "Closed aperture flow coefficient, k = V_flow/ dp^m";
Real fraOpe "Fraction of aperture that is open";
initial equation
AClo=CDClo/CDCloRat * LClo * dpCloRat^(0.5-mClo);
equation
fraOpe =y;
kClo = CDClo * AClo/nCom * sqrt(2/rho_default);
kOpe = CDOpe * AOpe/nCom * sqrt(2/rho_default);
// flow exponent
m = fraOpe*mOpe + (1-fraOpe)*mClo;
// opening area
A = fraOpe*AOpe + (1-fraOpe)*AClo;
// friction coefficient for power law
kVal = fraOpe*kOpe + (1-fraOpe)*kClo;
// orifice equation
for i in 1:nCom loop
dV_flow[i] = Buildings.Airflow.Multizone.BaseClasses.powerLaw(
k=kVal,
dp=dpAB[i],
m=m,
dp_turbulent=dp_turbulent);
end for;
end DoorDiscretizedOperable;
Buildings.Airflow.Multizone.EffectiveAirLeakageArea
Effective air leakage area
Information
This model describes the one-directional pressure driven air flow through a crack-like opening, using the equation
V̇ = k Δpm,
where V̇ is the volume flow rate, k is a flow coefficient and m is the flow exponent. The flow coefficient is
k = L CD,Rat ΔpRat(0.5-m) (2/ρ0)0.5,
where L is the effective leakage area, CD,Rat is the discharge coefficient at the reference condition, ΔpRat is the pressure drop at the rating condition, and ρ0 is the mass density at the medium default pressure, temperature and humidity.
The effective air leakage area L can be obtained, for example, from the ASHRAE fundamentals (ASHRAE, 1997, p. 25.18). In the ASHRAE fundamentals, the effective air leakage area is based on a reference pressure difference of ΔpRat = 4 Pa and a discharge coefficient of CD,Rat = 1. A similar model is also used in the CONTAM software (Dols and Walton, 2002). Dols and Walton (2002) recommend to use for the flow exponent m=0.6 to m=0.7 if the flow exponent is not reported with the test results.
Note: The parameter CD does not affect this model, and it will
be removed in future releases.
References
- ASHRAE, 1997. ASHRAE Fundamentals, American Society of Heating, Refrigeration and Air-Conditioning Engineers, 1997.
- Dols and Walton, 2002. W. Stuart Dols and George N. Walton, CONTAMW 2.0 User Manual, Multizone Airflow and Contaminant Transport Analysis Software, Building and Fire Research Laboratory, National Institute of Standards and Technology, Tech. Report NISTIR 6921, November, 2002.
Extends from Buildings.Airflow.Multizone.Orifice (Orifice).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Boolean | forceErrorControlOnFlow | true | Flag to force error control on m_flow. Set to true if interested in flow rate |
| Real | m | 0.65 | Flow exponent, m=0.5 for turbulent, m=1 for laminar |
| Boolean | useDefaultProperties | true | Set to false to use density and viscosity based on actual medium state, rather than using default values |
| PressureDifference | dp_turbulent | 0.1 | Pressure difference where laminar and turbulent flow relation coincide. Recommended = 0.1 [Pa] |
| Length | lWet | sqrt(A) | Wetted perimeter used for Reynolds number calculation [m] |
| Area | L | Effective leakage area [m2] | |
| Orifice characteristics | |||
| Area | A | L*CDRat/CD*dpRat^(0.5 - m) | Area of orifice [m2] |
| Real | CD | 0.65 | Discharge coefficient |
| Rating conditions | |||
| PressureDifference | dpRat | 4 | Pressure drop at rating condition [Pa] |
| Real | CDRat | 1 | Discharge coefficient |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| 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 |
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
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) |
Modelica definition
model EffectiveAirLeakageArea "Effective air leakage area"
extends Buildings.Airflow.Multizone.Orifice(
m=0.65,
final A=L * CDRat/CD * dpRat^(0.5-m));
parameter Modelica.SIunits.PressureDifference dpRat(min=0,
displayUnit="Pa") = 4
"|Rating conditions|Pressure drop at rating condition";
parameter Real CDRat(min=0, max=1)=1
"|Rating conditions|Discharge coefficient";
parameter Modelica.SIunits.Area L(min=0) "Effective leakage area";
initial equation
assert(CD > 0.649 and CD < 0.651,
"The parameter CD does not affect the model " + getInstanceName() + " and will be removed in future releases.",
level=AssertionLevel.warning);
end EffectiveAirLeakageArea;
Buildings.Airflow.Multizone.MediumColumn
Vertical shaft with no friction and no storage of heat and mass
Information
This model describes the pressure difference of a vertical medium column. It can be used to model the pressure difference caused by stack effect.
The model can be used with the following three configurations, which are
controlled by the setting of the parameter densitySelection:
-
top: Use this setting to use the density from the volume that is connected toport_a. -
bottom: Use this setting to use the density from the volume that is connected toport_b. -
actual: Use this setting to use the density based on the actual flow direction.
The settings top and bottom
should be used when rooms or different floors of a building are
connected since multizone airflow models assume that each floor is completely mixed.
For these two seetings, this model will compute the pressure between the center of the room
and an opening that is at height h relative to the center of the room.
The setting actual may be used to model a chimney in which
a column of air will change its density based on the flow direction.
In this model, the parameter h must always be positive, and the port port_a must be
at the top of the column.
For a steady-state model, use Buildings.Airflow.Multizone.MediumColumnDynamic instead of this model.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | Modelica.Media.Interfaces.Pa... | Medium in the component | |
| Length | h | 3 | Height of shaft [m] |
| densitySelection | densitySelection | Select how to pick density | |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
Connectors
| Type | Name | Description |
|---|---|---|
| replaceable package Medium | Medium in the component | |
| 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) |
Modelica definition
model MediumColumn
"Vertical shaft with no friction and no storage of heat and mass"
import Modelica.Constants;
replaceable package Medium = Modelica.Media.Interfaces.PartialMedium
"Medium in the component";
parameter Modelica.SIunits.Length h(min=0) = 3 "Height of shaft";
parameter Buildings.Airflow.Multizone.Types.densitySelection densitySelection
"Select how to pick density";
parameter Boolean allowFlowReversal=true
"= false to simplify equations, assuming, but not enforcing, no flow reversal";
Modelica.Fluid.Interfaces.FluidPort_a port_a(
redeclare package Medium = Medium,
m_flow(min=if allowFlowReversal then -Constants.inf else 0),
p(start=Medium.p_default))
"Fluid connector a (positive design flow direction is from port_a to port_b)";
Modelica.Fluid.Interfaces.FluidPort_b port_b(
redeclare package Medium = Medium,
m_flow(max=if allowFlowReversal then +Constants.inf else 0),
p(start=Medium.p_default))
"Fluid connector b (positive design flow direction is from port_a to port_b)";
Modelica.SIunits.VolumeFlowRate V_flow
"Volume flow rate at inflowing port (positive when flow from port_a to port_b)";
Modelica.SIunits.MassFlowRate m_flow
"Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction)";
Modelica.SIunits.PressureDifference dp(displayUnit="Pa")
"Pressure difference between port_a and port_b";
Modelica.SIunits.Density rho "Density in medium column";
protected
Medium.ThermodynamicState sta_a=Medium.setState_phX(
port_a.p,
actualStream(port_a.h_outflow),
actualStream(port_a.Xi_outflow)) "Medium properties in port_a";
Medium.MassFraction Xi[Medium.nXi] "Mass fraction used to compute density";
initial equation
// The next assert tests for all allowed values of the enumeration.
// Testing against densitySelection > 0 gives an error in OpenModelica as enumerations start with 1.
assert(densitySelection == Buildings.Airflow.Multizone.Types.densitySelection.fromTop
or densitySelection == Buildings.Airflow.Multizone.Types.densitySelection.fromBottom
or densitySelection == Buildings.Airflow.Multizone.Types.densitySelection.actual,
"You need to set the parameter \"densitySelection\" for the model MediumColumn.");
equation
// Design direction of mass flow rate
m_flow = port_a.m_flow;
// Pressure difference between ports
// Xi is computed first as it is used in two expression, and in one
// of them only one component is used.
// We test for Medium.nXi == 0 as Modelica.Media.Air.SimpleAir has no
// moisture and hence Xi[1] is an illegal statement.
// We first compute temperature and then invoke a density function that
// takes temperature as an argument. Simply calling a density function
// of a medium that takes enthalpy as an argument would be dangerous
// as different media can have different datum for the enthalpy.
if (densitySelection == Buildings.Airflow.Multizone.Types.densitySelection.fromTop) then
Xi = inStream(port_a.Xi_outflow);
rho = Buildings.Utilities.Psychrometrics.Functions.density_pTX(
p=port_a.p,
T=Medium.temperature(Medium.setState_phX(port_a.p, inStream(port_a.h_outflow), Xi)),
X_w=if Medium.nXi == 0 then 0 else Xi[1]);
elseif (densitySelection == Buildings.Airflow.Multizone.Types.densitySelection.fromBottom) then
Xi = inStream(port_b.Xi_outflow);
rho = Buildings.Utilities.Psychrometrics.Functions.density_pTX(
p=port_b.p,
T=Medium.temperature(Medium.setState_phX(port_b.p, inStream(port_b.h_outflow), Xi)),
X_w=if Medium.nXi == 0 then 0 else Xi[1]);
else
Xi = actualStream(port_a.Xi_outflow);
rho = Buildings.Utilities.Psychrometrics.Functions.density_pTX(
p=port_a.p,
T=Medium.temperature(Medium.setState_phX(port_a.p, actualStream(port_a.h_outflow), Xi)),
X_w=if Medium.nXi == 0 then 0 else Xi[1]);
end if;
V_flow = m_flow/Medium.density(sta_a);
dp = port_a.p - port_b.p;
dp = -h*rho*Modelica.Constants.g_n;
// Isenthalpic state transformation (no storage and no loss of energy)
port_a.h_outflow = inStream(port_b.h_outflow);
port_b.h_outflow = inStream(port_a.h_outflow);
// Mass balance (no storage)
port_a.m_flow + port_b.m_flow = 0;
// Transport of substances
port_a.Xi_outflow = inStream(port_b.Xi_outflow);
port_b.Xi_outflow = inStream(port_a.Xi_outflow);
port_a.C_outflow = inStream(port_b.C_outflow);
port_b.C_outflow = inStream(port_a.C_outflow);
end MediumColumn;
Buildings.Airflow.Multizone.MediumColumnDynamic
Vertical shaft with no friction and storage of heat and mass
Information
This model contains a completely mixed fluid volume and models that take into account the pressure difference of a medium column that is at the same temperature as the fluid volume. It can be used to model the pressure difference caused by a stack effect.
Set the parameter use_HeatTransfer=true to expose
a heatPort. This heatPort can be used
to add or subtract heat from the volume. This allows, for example,
to use this model in conjunction with a model for heat transfer through
walls to model a solar chimney that stores heat.
For a steady-state model, use Buildings.Airflow.Multizone.MediumColumn instead of this model.
In this model, the parameter h must always be positive, and the port port_a must be
at the top of the column.
Extends from Buildings.Fluid.Interfaces.LumpedVolumeDeclarations (Declarations for lumped volumes).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Length | h | 3 | Height of shaft [m] |
| Volume | V | Volume in medium shaft [m3] | |
| Nominal condition, used only for steady-state model | |||
| MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |
| Dynamics | |||
| Equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
| Dynamics | massDynamics | energyDynamics | Type of mass balance: dynamic (3 initialization options) or steady state |
| Real | mSenFac | 1 | Factor for scaling the sensible thermal mass of the volume |
| Initialization | |||
| AbsolutePressure | p_start | Medium.p_default | Start value of pressure [Pa] |
| Temperature | T_start | Medium.T_default | Start value of temperature [K] |
| MassFraction | X_start[Medium.nX] | Medium.X_default | Start value of mass fractions m_i/m [kg/kg] |
| ExtraProperty | C_start[Medium.nC] | fill(0, Medium.nC) | Start value of trace substances |
| ExtraProperty | C_nominal[Medium.nC] | fill(1E-2, Medium.nC) | Nominal value of trace substances. (Set to typical order of magnitude.) |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| Heat transfer | |||
| Boolean | use_HeatTransfer | false | = true to use the HeatTransfer model |
| replaceable model HeatTransfer | Modelica.Fluid.Vessels.BaseC... | Wall heat transfer | |
Connectors
| Type | Name | Description |
|---|---|---|
| replaceable package Medium | Medium in the component | |
| 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) |
| HeatPort_a | heatPort | Heat port to exchange energy with the fluid volume |
| Assumptions | ||
| Heat transfer | ||
| replaceable model HeatTransfer | Wall heat transfer | |
Modelica definition
model MediumColumnDynamic
"Vertical shaft with no friction and storage of heat and mass"
extends Buildings.Fluid.Interfaces.LumpedVolumeDeclarations;
import Modelica.Constants;
replaceable package Medium = Modelica.Media.Interfaces.PartialMedium
"Medium in the component";
parameter Modelica.SIunits.Length h(min=0) = 3 "Height of shaft";
parameter Boolean allowFlowReversal=true
"= false to simplify equations, assuming, but not enforcing, no flow reversal";
parameter Modelica.SIunits.MassFlowRate m_flow_nominal(min=0)
"Nominal mass flow rate";
Modelica.Fluid.Interfaces.FluidPort_a port_a(
redeclare final package Medium = Medium,
m_flow(min=if allowFlowReversal then -Constants.inf else 0),
p(start=Medium.p_default))
"Fluid connector a (positive design flow direction is from port_a to port_b)";
Modelica.Fluid.Interfaces.FluidPort_b port_b(
redeclare final package Medium = Medium,
m_flow(max=if allowFlowReversal then +Constants.inf else 0),
p(start=Medium.p_default))
"Fluid connector b (positive design flow direction is from port_a to port_b)";
// m_flow_nominal is not used by vol, since this component
// can only be configured as a dynamic model.
Buildings.Fluid.MixingVolumes.MixingVolume vol(
final nPorts=2,
redeclare final package Medium = Medium,
final m_flow_nominal=m_flow_nominal,
final V=V,
final energyDynamics=energyDynamics,
final massDynamics=massDynamics,
final p_start=p_start,
final T_start=T_start,
final X_start=X_start,
final C_start=C_start) "Air volume in the shaft";
MediumColumn colTop(
redeclare final package Medium = Medium,
final densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromBottom,
h=h/2,
final allowFlowReversal=allowFlowReversal)
"Medium column that connects to top port";
MediumColumn colBot(
redeclare final package Medium = Medium,
final densitySelection=Buildings.Airflow.Multizone.Types.densitySelection.fromTop,
h=h/2,
final allowFlowReversal=allowFlowReversal)
"Medium colum that connects to bottom port";
parameter Modelica.SIunits.Volume V "Volume in medium shaft";
// Heat transfer through boundary
parameter Boolean use_HeatTransfer = false
"= true to use the HeatTransfer model";
replaceable model HeatTransfer =
Modelica.Fluid.Vessels.BaseClasses.HeatTransfer.IdealHeatTransfer
constrainedby
Modelica.Fluid.Vessels.BaseClasses.HeatTransfer.PartialVesselHeatTransfer
"Wall heat transfer";
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a heatPort if use_HeatTransfer
"Heat port to exchange energy with the fluid volume";
equation
connect(colBot.port_a, vol.ports[1]);
connect(vol.ports[2], colTop.port_b);
connect(colTop.port_a, port_a);
connect(colBot.port_b, port_b);
connect(heatPort, vol.heatPort);
end MediumColumnDynamic;
Buildings.Airflow.Multizone.Orifice
Orifice
Information
This model describes the mass flow rate and pressure difference relation of an orifice in the form
V̇ = k Δpm,
where V̇ is the volume flow rate, k is a flow coefficient and m is the flow exponent. The flow coefficient is
k = CD A (2/ρ0)0.5,
where CD is the discharge coefficient, A is the cross section area and ρ0 is the mass density at the medium default pressure, temperature and humidity.
For turbulent flow, set m=1/2 and for laminar flow, set m=1. Large openings are characterized by values close to 0.5, while values near 0.65 have been found for small crack-like openings (Dols and Walton, 2002).
References
- W. Stuart Dols and George N. Walton, CONTAMW 2.0 User Manual, Multizone Airflow and Contaminant Transport Analysis Software, Building and Fire Research Laboratory, National Institute of Standards and Technology, Tech. Report NISTIR 6921, November, 2002.
Extends from Buildings.Airflow.Multizone.BaseClasses.PowerLawResistance (Flow resistance that uses the power law).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | Medium in the component | |
| Boolean | forceErrorControlOnFlow | true | Flag to force error control on m_flow. Set to true if interested in flow rate |
| Real | m | 0.5 | Flow exponent, m=0.5 for turbulent, m=1 for laminar |
| Boolean | useDefaultProperties | true | Set to false to use density and viscosity based on actual medium state, rather than using default values |
| PressureDifference | dp_turbulent | 0.1 | Pressure difference where laminar and turbulent flow relation coincide. Recommended = 0.1 [Pa] |
| Length | lWet | sqrt(A) | Wetted perimeter used for Reynolds number calculation [m] |
| Orifice characteristics | |||
| Area | A | Area of orifice [m2] | |
| Real | CD | 0.65 | Discharge coefficient |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal |
| 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 |
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
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) |
Modelica definition
model Orifice "Orifice"
extends Buildings.Airflow.Multizone.BaseClasses.PowerLawResistance(
m=0.5,
k=CD*A*sqrt(2.0/rho_default));
parameter Real CD=0.65 "|Orifice characteristics|Discharge coefficient";
end Orifice;
Buildings.Airflow.Multizone.ZonalFlow_ACS
Zonal flow with input air change per second
Information
This model computes the air exchange between volumes.
Input is the air change per seconds. The volume flow rate is computed as
V_flow = ACS * V
where ACS is an input and the volume V is a parameter.
Extends from Buildings.Airflow.Multizone.BaseClasses.ZonalFlow (Flow across zonal boundaries of a room).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | ||
| Boolean | useDefaultProperties | false | Set to true to use constant density |
| Volume | V | Volume of room [m3] | |
| Advanced | |||
| MassFlowRate | m1_flow_small | 1E-4*abs(m1_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| MassFlowRate | m2_flow_small | 1E-4*abs(m2_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPort_a | port_a1 | Fluid connector a1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_b | port_b1 | Fluid connector b1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_a | port_a2 | Fluid connector a2 (positive design flow direction is from port_a2 to port_b2) |
| FluidPort_b | port_b2 | Fluid connector b2 (positive design flow direction is from port_a2 to port_b2) |
| input RealInput | ACS | Air change per seconds, relative to the smaller of the two volumes |
Modelica definition
model ZonalFlow_ACS "Zonal flow with input air change per second"
extends Buildings.Airflow.Multizone.BaseClasses.ZonalFlow;
parameter Boolean useDefaultProperties = false
"Set to true to use constant density";
parameter Modelica.SIunits.Volume V "Volume of room";
Modelica.Blocks.Interfaces.RealInput ACS
"Air change per seconds, relative to the smaller of the two volumes";
protected
Modelica.SIunits.VolumeFlowRate V_flow
"Volume flow rate at standard pressure";
Modelica.SIunits.MassFlowRate m_flow "Mass flow rate";
parameter Medium.ThermodynamicState sta_default = Medium.setState_pTX(T=Medium.T_default,
p=Medium.p_default, X=Medium.X_default);
parameter Modelica.SIunits.Density rho_default=Medium.density(sta_default)
"Density, used to compute fluid volume";
Medium.ThermodynamicState sta_a1_inflow=
Medium1.setState_phX(port_a1.p, port_b1.h_outflow, port_b1.Xi_outflow)
"Medium properties in port_a1";
Medium.ThermodynamicState sta_a2_inflow=
Medium1.setState_phX(port_a2.p, port_b2.h_outflow, port_b2.Xi_outflow)
"Medium properties in port_a2";
equation
when useDefaultProperties and initial() then
assert( abs(1-rho_default/((Medium.density(sta_a1_inflow) + Medium.density(sta_a2_inflow))/2)) < 0.2,
"Wrong density. Densities need to match.");
// The next three lines have been removed as they cause
// a compilation error in OpenModelica.
// + "\n Medium.density(sta_a1) = " + String(Medium.density(sta_a1_inflow))
// + "\n Medium.density(sta_a2) = " + String(Medium.density(sta_a2_inflow))
// + "\n rho_nominal = " + String(rho_default));
end when;
V_flow = V * ACS;
m_flow / V_flow = if useDefaultProperties then rho_default else (Medium.density(sta_a1_inflow) + Medium.density(sta_a2_inflow))/2;
// assign variable in base class
port_a1.m_flow = m_flow;
port_a2.m_flow = m_flow;
end ZonalFlow_ACS;
Buildings.Airflow.Multizone.ZonalFlow_m_flow
Zonal flow with input air change per second
Information
This model computes the air exchange between volumes.
Input is the mass flow rate from
port_a1 to port_b1 and from
port_a2 to port_b2.
Extends from Buildings.Airflow.Multizone.BaseClasses.ZonalFlow (Flow across zonal boundaries of a room).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | PartialMedium | ||
| Advanced | |||
| MassFlowRate | m1_flow_small | 1E-4*abs(m1_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| MassFlowRate | m2_flow_small | 1E-4*abs(m2_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| Diagnostics | |||
| Boolean | show_T | false | = true, if actual temperature at port is computed |
Connectors
| Type | Name | Description |
|---|---|---|
| FluidPort_a | port_a1 | Fluid connector a1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_b | port_b1 | Fluid connector b1 (positive design flow direction is from port_a1 to port_b1) |
| FluidPort_a | port_a2 | Fluid connector a2 (positive design flow direction is from port_a2 to port_b2) |
| FluidPort_b | port_b2 | Fluid connector b2 (positive design flow direction is from port_a2 to port_b2) |
| input RealInput | mAB_flow | Mass flow rate from A to B, positive if flow from port_a1 to port_b1 |
| input RealInput | mBA_flow | Mass flow rate from B to A, positive if flow from port_a2 to port_b2 |
Modelica definition
model ZonalFlow_m_flow "Zonal flow with input air change per second"
extends Buildings.Airflow.Multizone.BaseClasses.ZonalFlow;
Modelica.Blocks.Interfaces.RealInput mAB_flow "Mass flow rate from A to B, positive if flow from port_a1 to port_b1";
Modelica.Blocks.Interfaces.RealInput mBA_flow "Mass flow rate from B to A, positive if flow from port_a2 to port_b2";
equation
port_a1.m_flow = mAB_flow;
port_a2.m_flow = mBA_flow;
end ZonalFlow_m_flow;