Description: "Package with models for radiosity transfer"

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## Buildings.HeatTransfer.Radiosity

Package with models for radiosity transfer

### Information

This package provides component models for the infrared radiative heat exchange of window assemblies. The models are according to TARCOG 2006, except for the outdoor radiosity, which is computed by Buildings.HeatTransfer.Radiosity.OutdoorRadiosity. The outdoor radiosity is different from the TARCOG implementation so that the same equations are used for windows as are used for opaque walls in the room heat transfer model of the package Buildings.Rooms.

By definition, incoming and outcoming radiosity are both positive. This is required to connect incoming and outcoming radiosity connectors.

#### References

TARCOG 2006: Carli, Inc., TARCOG: Mathematical models for calculation of thermal performance of glazing systems with our without shading devices, Technical Report, Oct. 17, 2006.

Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).

### Package Content

Name | Description
--- | ---
Constant | Generate constant radiosity signal
IndoorRadiosity | Model for indoor radiosity
OpaqueSurface | Model for an opaque surface
OutdoorRadiosity | Model for the outdoor radiosity that strikes the window
RadiositySplitter | Splits the incoming radiosity into two flows based on an input signal
Examples | Collection of models that illustrate model use and test models
BaseClasses | Package with base classes for Buildings.HeatTransfer.Radiosity

## Buildings.HeatTransfer.Radiosity.Constant

Generate constant radiosity signal

### Information

Constant radiosity source. This model requires k ≥ 0.

This model is used in Buildings.HeatTransfer.BaseClasses.DummyConstructionExterior.

Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

### Parameters

Type | Name | Default | Description
--- | --- | --- | ---
Real | k |  | Radiosity that leaves this component (k &ge; 0)

### Connectors

Type | Name | Description
--- | --- | ---
output RadiosityOutflow | JOut | [W]

### Modelica definition

block Constant "Generate constant radiosity signal" parameter Real k(min=0, start=0) "Radiosity that leaves this component (k &ge; 0)"; extends Modelica.Blocks.Icons.Block; Interfaces.RadiosityOutflow JOut; equation JOut = k; end Constant;

## Buildings.HeatTransfer.Radiosity.IndoorRadiosity

Model for indoor radiosity

### Information

Model for the indoor emissive power that hits a window. The computation is according to TARCOG 2006.

#### References

TARCOG 2006: Carli, Inc., TARCOG: Mathematical models for calculation of thermal performance of glazing systems with our without shading devices, Technical Report, Oct. 17, 2006.

Extends from Buildings.HeatTransfer.Radiosity.BaseClasses.RadiosityOneSurface (Model for the radiosity balance of a device with one surface), Buildings.HeatTransfer.Radiosity.BaseClasses.ParametersOneSurface (Parameters that are used to model one surface).

### Parameters

Type | Name | Default | Description
--- | --- | --- | ---
Area | A |  | Surface area [m2]
Emissivity | absIR | 1 | Infrared absorptivity [1]
ReflectionCoefficient | rhoIR | 0 | Infrared reflectivity [1]
TransmissionCoefficient | tauIR | 0 | Infrared transmissivity [1]
Boolean | linearize | false | Set to true to linearize emissive power
Temperature | T0 | 293.15 | Temperature used to linearize radiative heat transfer [K]

### Connectors

Type | Name | Description
--- | --- | ---
input RadiosityInflow | JIn | Incoming radiosity [W]
output RadiosityOutflow | JOut | Outgoing radiosity [W]
HeatPort_a | heatPort | Heat port of the surface

### Modelica definition

model IndoorRadiosity "Model for indoor radiosity" extends Buildings.HeatTransfer.Radiosity.BaseClasses.RadiosityOneSurface; extends Buildings.HeatTransfer.Radiosity.BaseClasses.ParametersOneSurface( final absIR=1, final tauIR=0, final rhoIR=0); Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a heatPort "Heat port of the surface"; protected final parameter Real T03( min=0, final unit="K3") = T0^3 "3rd power of temperature T0"; final parameter Real T04( min=0, final unit="K4") = T0^4 "4th power of temperature T0"; Real T4( min=1E8, start=293.15^4, nominal=1E10, final unit="K4") "4th power of temperature"; equation T4 = if linearize then 4*T03*heatPort.T - 3*T04 else heatPort.T^4; JOut = A*Modelica.Constants.sigma*T4; 0 = heatPort.Q_flow + JIn - JOut; end IndoorRadiosity;

## Buildings.HeatTransfer.Radiosity.OpaqueSurface

Model for an opaque surface

### Information

Model for the emissive power of an opaque surface.

Extends from Buildings.HeatTransfer.Radiosity.BaseClasses.RadiosityOneSurface (Model for the radiosity balance of a device with one surface), Buildings.HeatTransfer.Radiosity.BaseClasses.ParametersOneSurface (Parameters that are used to model one surface).

### Parameters

Type | Name | Default | Description
--- | --- | --- | ---
Area | A |  | Surface area [m2]
Emissivity | absIR |  | Infrared absorptivity [1]
ReflectionCoefficient | rhoIR | 1 - absIR | Infrared reflectivity [1]
TransmissionCoefficient | tauIR | 1 - rhoIR - absIR | Infrared transmissivity [1]
Boolean | linearize | false | Set to true to linearize emissive power
Temperature | T0 | 293.15 | Temperature used to linearize radiative heat transfer [K]

### Connectors

Type | Name | Description
--- | --- | ---
input RadiosityInflow | JIn | Incoming radiosity [W]
output RadiosityOutflow | JOut | Outgoing radiosity [W]
HeatPort_a | heatPort | Heat port of this surface

### Modelica definition

model OpaqueSurface "Model for an opaque surface" extends Buildings.HeatTransfer.Radiosity.BaseClasses.RadiosityOneSurface; extends Buildings.HeatTransfer.Radiosity.BaseClasses.ParametersOneSurface( final tauIR=1 - rhoIR - absIR, final rhoIR=1 - absIR); Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a heatPort "Heat port of this surface"; protected final parameter Real T03( min=0, final unit="K3") = T0^3 "3rd power of temperature T0"; final parameter Real T04( min=0, final unit="K4") = T0^4 "4th power of temperature T0"; Real T4( min=1E8, start=293.15^4, nominal=1E10, final unit="K4") "4th power of temperature"; equation T4 = if linearize then 4*T03*heatPort.T - 3*T04 else heatPort.T^4; JOut = A*absIR*Modelica.Constants.sigma*T4 + rhoIR*JIn; 0 = heatPort.Q_flow + JIn - JOut; end OpaqueSurface;

## Buildings.HeatTransfer.Radiosity.OutdoorRadiosity

Model for the outdoor radiosity that strikes the window

### Information

Model for the infrared radiosity balance of the outdoor environment.

### Parameters

Type | Name | Default | Description
--- | --- | --- | ---
Area | A |  | Area of receiving surface [m2]
Real | vieFacSky |  | View factor from receiving surface to sky (=1 for roofs)
Boolean | linearize | false | Set to true to linearize emissive power
Temperature | T0 | 293.15 | Temperature used to linearize radiative heat transfer [K]

### Connectors

Type | Name | Description
--- | --- | ---
input RealInput | TOut | Outside temperature [K]
input RealInput | TBlaSky | Black body sky temperature [K]
output RadiosityOutflow | JOut | Radiosity that flows out of component [W]

### Modelica definition

model OutdoorRadiosity "Model for the outdoor radiosity that strikes the window" parameter Modelica.SIunits.Area A "Area of receiving surface"; parameter Real vieFacSky(final min=0, final max=1) "View factor from receiving surface to sky (=1 for roofs)"; parameter Boolean linearize=false "Set to true to linearize emissive power"; parameter Modelica.SIunits.Temperature T0=293.15 "Temperature used to linearize radiative heat transfer"; Real TRad4(unit="K4") "4th power of the mean outdoor temperature"; Modelica.SIunits.Temperature TRad "Mean radiant temperature"; Modelica.Blocks.Interfaces.RealInput TOut( final quantity="ThermodynamicTemperature", final unit="K", min=0) "Outside temperature"; Modelica.Blocks.Interfaces.RealInput TBlaSky( final quantity="ThermodynamicTemperature", final unit="K", min=0) "Black body sky temperature"; Buildings.HeatTransfer.Interfaces.RadiosityOutflow JOut "Radiosity that flows out of component"; protected final parameter Real T03( min=0, final unit="K3") = T0^3 "3rd power of temperature T0"; final parameter Real T04( min=0, final unit="K4") = T0^4 "4th power of temperature T0"; equation TRad4 = (vieFacSky*TBlaSky^4 + (1 - vieFacSky)*TOut^4); JOut = A*Modelica.Constants.sigma*TRad4; TRad = if linearize then (TRad4 + 3*T04)/(4*T03) else TRad4^(1/4); end OutdoorRadiosity;

## Buildings.HeatTransfer.Radiosity.RadiositySplitter

Splits the incoming radiosity into two flows based on an input signal

### Information

This blocks splits the incoming radiosity into two fluxes according to

JOut,1 = u JIn,
JOut,2 = (1-u) JIn.

This block may be used to split the radiosity flux into a fraction that strikes the shaded part of a window, and a fraction that strikes the non-shaded part.

Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

### Connectors

Type | Name | Description
--- | --- | ---
input RadiosityInflow | JIn | Inflowing radiosity [W]
input RealInput | u | u times incoming radiosity
output RadiosityOutflow | JOut_1 | u times incoming radiosity [W]
output RadiosityOutflow | JOut_2 | (1-u) times incoming radiosity [W]

### Modelica definition

block RadiositySplitter "Splits the incoming radiosity into two flows based on an input signal" extends Modelica.Blocks.Icons.Block; Interfaces.RadiosityInflow JIn "Inflowing radiosity"; Modelica.Blocks.Interfaces.RealInput u(min=0, max=1) "u times incoming radiosity"; Interfaces.RadiosityOutflow JOut_1 "u times incoming radiosity"; Interfaces.RadiosityOutflow JOut_2 "(1-u) times incoming radiosity"; equation JOut_1 = u * JIn; JOut_2 = (1-u)* JIn; end RadiositySplitter;