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# internalHeatSource

Specify internal heat source for a thermal model

## Description

example

internalHeatSource(thermalmodel,heatSourceValue) specifies an internal heat source for the thermal model. This syntax declares that the entire geometry is a heat source.

### Note

Use internalHeatSource for specifying internal heat generators, that is, for specifying heat sources that belong to the geometry of the model. To specify a heat influx from an external source, use the thermalBC function with the HeatFlux parameter.

example

internalHeatSource(thermalmodel,heatSourceValue,RegionType,RegionID) specifies geometry regions of type RegionType with ID numbers in RegionID as heat sources. Always specify heatSourceValue first, then specify RegionType and RegionID.

heatSource = internalHeatSource(___) returns the heat source object.

## Examples

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Create a transient thermal model.

thermalmodel = createpde('thermal','transient');

Import the geometry.

gm = importGeometry(thermalmodel,'SquareBeam.STL');

Set thermal conductivity to 0.2, mass density to 2700e-9, and specific heat to 920.

thermalProperties(thermalmodel,'ThermalConductivity',0.2, ...
'MassDensity',2700e-9, ...
'SpecificHeat',920)
ans =
ThermalMaterialAssignment with properties:

RegionType: 'cell'
RegionID: 1
ThermalConductivity: 0.2000
MassDensity: 2.7000e-06
SpecificHeat: 920

Specify that the entire geometry generates heat at the rate 2e-4.

internalHeatSource(thermalmodel,2e-4)
ans =
HeatSourceAssignment with properties:

RegionType: 'cell'
RegionID: 1
HeatSource: 2.0000e-04

thermalModel = createpde('thermal','transient');

Create the geometry.

SQ1 = [3; 4; 0; 3; 3; 0; 0; 0; 3; 3];
D1 = [2; 4; 0.5; 1.5; 2.5; 1.5; 1.5; 0.5; 1.5; 2.5];
gd = [SQ1 D1];
sf = 'SQ1+D1';
ns = char('SQ1','D1');
ns = ns';
dl = decsg(gd,sf,ns);

geometryFromEdges(thermalModel,dl);

Set thermal conductivity to 50, mass density to 2500, and specific heat to 600.

thermalProperties(thermalModel,'ThermalConductivity',50, ...
'MassDensity',2500, ...
'SpecificHeat',600);

Specify that face 1 generates heat at 25.

internalHeatSource(thermalModel,25,'Face',1)
ans =
HeatSourceAssignment with properties:

RegionType: 'face'
RegionID: 1
HeatSource: 25

Use a function handle to specify an internal heat source that depends on coordinates.

Create a thermal model for transient analysis and include the geometry. The geometry is a rod with a circular cross section. The 2-D model is a rectangular strip whose y-dimension extends from the axis of symmetry to the outer surface, and whose x-dimension extends over the actual length of the rod.

thermalmodel = createpde('thermal','transient');
g = decsg([3 4 -1.5 1.5 1.5 -1.5 0 0 .2 .2]');
geometryFromEdges(thermalmodel,g);

The heat is generated within the rod due to the radioactive decay. Therefore, the entire geometry is an internal nonlinear heat source and can be represented by a function of the y-coordinate, for example, $\mathit{q}=2000\mathit{y}$.

q = @(location,state)2000*location.y;

Specify the internal heat source for the transient model.

internalHeatSource(thermalmodel,q)
ans =
HeatSourceAssignment with properties:

RegionType: 'face'
RegionID: 1
HeatSource: @(location,state)2000*location.y

## Input Arguments

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Thermal model, specified as a ThermalModel object. The model contains the geometry, mesh, thermal properties of the material, internal heat source, boundary conditions, and initial conditions.

Geometric region type, specified as 'Face' for a 2-D model or 'Cell' for a 3-D model.

Example: internalHeatSource(thermalmodel,25,'Cell',1)

Data Types: char | string

Geometric region ID, specified as a vector of positive integers. Find the region IDs by using pdegplot.

Example: internalHeatSource(thermalmodel,25,'Cell',1:3)

Data Types: double

Heat source value, specified as a number or a function handle. Use a function handle to specify the internal heat source that depends on space, time, or temperature. The function must be of the form

heatSourceValue = heatSourceFun(location,state)

The solver passes location data as a structure array with the fields location.x, location.y, and, for 3-D problems, location.z. The state data is a structure array with the fields state.u, state.ux, state.uy, state.uz (for 3-D problems), and state.time (for transient problems). The state.u field contains the solution vector. The state.ux, state.uy, state.uz fields are estimates of the solution’s partial derivatives at the corresponding points of the location structure. The state.time field contains time at evaluation points.

heatSourceFun must return a row vector heatSourceValue with the number of columns equal to the number of evaluation points, M = length(location.x).

Example: internalHeatSource(thermalmodel,25)

Data Types: double | function_handle

### Output Arguments

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Handle to heat source, returned as an object. heatSourceValue associates the heat source value with the geometric region.

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