pde themral model, thermally connect two cells

Hi,

This question is related to one of my other quetion but would like to ask it separately.

I have this thermal model in pde. Two cell regions, no gpa between them. After assign with different conductivities (not sure if that's relevant), I solved it (code and model attached) and the result is shown below.

As you can see, cell 2 was thermally isolated from cell 1 (where heat flux and BC were assigned).

Any reason why matlab didn't see them as thermally connected? I check other examples on the web like this one (openExample('pde/FindThermalConductivityForCellsOf3DGeometryExample'). And no specific operation was necessary to connect the regions.

And it would be great if I can put a thermal resistance [C/(W*m2)] between them.

My code:

% Import the geometry

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

importGeometry(thermalmodel,'PCBA_Dummy_PRT_2.stl');

pdegplot(thermalmodel, 'FaceAlpha',0.5)

% Mesh the Geometry and Determine the Part size

generateMesh(thermalmodel,'Hmax',.09);

thermalmodel.Mesh

% Show cell

pdegplot(thermalmodel,'FaceAlpha',0.25,'CellLabel','on')

title('Geometry with Cell Labels')

% Show face

pdegplot(thermalmodel,'FaceLabels','on','FaceAlpha',0.5);

title('Geometry with Cell Labels')

xLength = max(thermalmodel.Mesh.Nodes(1,:)) - min(thermalmodel.Mesh.Nodes(1,:))

yLength = max(thermalmodel.Mesh.Nodes(2,:)) - min(thermalmodel.Mesh.Nodes(2,:))

zLength = max(thermalmodel.Mesh.Nodes(3,:)) - min(thermalmodel.Mesh.Nodes(3,:))

% Setup the Material Properties

u = symunit;

tc = vpa(52) *u.Watt/(u.m*u.Kelvin)

tc = rewrite(tc,u.W/(u.in*u.Kelvin))

tc = double(separateUnits(tc));

thermalProperties(thermalmodel,'Cell',1,'ThermalConductivity',tc);

thermalProperties(thermalmodel,'Cell',2,'ThermalConductivity',tc*2);

% Show thermal properties

mpa = findThermalProperties(thermalmodel.MaterialProperties,'Cell',1:2);

Cell_1 = mpa(1)

Cell_2 = mpa(2)

% Set up the Boundary Conditions

htc = vpa(25) *u.Watt/(u.m^2*u.Kelvin);

htc = rewrite(htc,u.Watt/(u.in^2*u.Kelvin));

htc = double(separateUnits(htc));

thermalBC(thermalmodel,'Face',2,'Temperature',55);

thermalBC(thermalmodel,'Face',4,'Temperature',55);

thermalBC(thermalmodel,'Face',6,'HeatFlux',25);

% Solve the FEA analysis

tic

results = solve(thermalmodel);

time = toc

t_max = max(results.Temperature)

pdeplot3D(thermalmodel,'ColorMapData',results.Temperature)

title('Temperature in K')

colorbar

Thank you!

Derek

Answer 1

[Ravi Kumar]

Hi Derek,

Multidomains in the imported geometry, using STL file, are not recoganized as connected cells of the same geometry. If the cells are concentric, then you can use multicuboid to create such a geometry.

Regards,

Ravi

[Derek Feng]

Thank you, Ravi.

As you can see from my image, it's not concentric at all. Probably not, but can I thermally connect the two cells from multidomains?

[LORIS VALENTI]

Ehi...I have your same problem. Did you find a solution for the problem? Thanks a lot!