Thermal analysis excavated cylinder

Hello,

I am super green at matlab. Most of the code is adapted from examples I have found.

I am trying to find the steady state temperature distribution of a cylinder. When I look at the 3D plot, I can see there 12 faces identified, but when I try to apply the BC for all, the code returns an error.

Error using pde.ThermalModel/thermalBC (line 130)

Face ID exceeds the number of faces in the Geometry.

Error in realcylinder (line 16)

thermalBC(thermalmodel,'Face',6,'Temperature',T2);

If I comment out the additional faces it seems to work but it does not show what I want because, as I understand it, the unspecified BC are taken as insulated.

Could anyone tell me what grave mistake I am making?

Note that the additional faces are generated by "Thinkercad"

However, when I use another stl file generated by Solidworks, the error is different:

Boundary condition must be specified on a face for 3-D geometry and on an edge of 2-D geometry.

Thank you for your help.

Max

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

importGeometry(thermalmodel,'cylinder.stl');

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

axis equal

mesh=generateMesh(thermalmodel,'Hmax',5)

pdemesh(thermalmodel);

pdegplot(model,'FaceLabel','on','FaceAlpha',0.5)

axis equal

T1 =180;

T2 = 25;

thermalProperties(thermalmodel,'ThermalConductivity',0.15);

thermalBC(thermalmodel,'Face',2,'Temperature',T1);

thermalBC(thermalmodel,'Face',3,'Temperature',T1);

thermalBC(thermalmodel,'Face',4,'Temperature',T2);

%thermalBC(thermalmodel,'Face',5,'Temperature',T2);

thermalBC(thermalmodel,'Face',6,'Temperature',T2);

%thermalBC(thermalmodel,'Face',7,'Temperature',T2);

%thermalBC(thermalmodel,'Face',8,'Temperature',T2);

%thermalBC(thermalmodel,'Face',9,'Temperature',T2);

%thermalBC(thermalmodel,'Face',10,'Temperature',T2);

%thermalBC(thermalmodel,'Face',11,'Temperature',T2);

%thermalBC(thermalmodel,'Face',12,'Temperature',T2); %Temperature downside

results = solve(thermalmodel);

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

UPDATE

Now, from this code:

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

importGeometry(thermalmodel,'cylinder_2.stl');

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

axis equal

mesh=generateMesh(thermalmodel,'Hmax',5)

pdemesh(thermalmodel);

pdegplot(thermalmodel,'FaceLabel','on','FaceAlpha',0.5)

% axis equal

% T1 =90;%Temperature inside

% T2 = 25;%Room Temperature

thermalProperties(thermalmodel,'ThermalConductivity',0.386,'MassDensity',8.933*10^(3),'SpecificHeat',0.386);

thermalBC(thermalmodel,'Face',1,'Temperature',T2);

thermalBC(thermalmodel,'Face',2,'Temperature',T2);

thermalBC(thermalmodel,'Face',3,'Temperature',T2);

thermalBC(thermalmodel,'Face',4,'Temperature',T1);

thermalBC(thermalmodel,'Face',5,'Temperature',T1);

results = solve(thermalmodel);

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

I get this figure:

But it yet does not show a real distribution. I feel that the BC set the outer temperature, but what I really would like to do is set th eroom temperature and allow the surface temperature be whatever it should be.

Thank you