Applying convection coefficient to face in 2D thermal simulation?

Hi

I am simulating a heat source in a pipe filled with air using 2d FEM. The innermost circle represents the heat source. The other 2 circles represent the inner and outer diameters of the pipe. Since the pipe is filled with air, the triangular elements between the pipe and the heat source will have a heat convection coefficient. I understand that thermal boundary conditions can be specified only for edges in 2d FEM using thermalBC. So if I use thermalBC here, how do I specify that the elements in air have a convection coefficient?

Will it be correct to use the following

thermalBC(thermalModel,'Edge',[1,2,3,4],'ConvectionCoefficient',300,'AmbientTemperature',25)

Appreciate any help in sorting this out.

Thanks

Answer 1

[Zuber Khan]

Hi,

In 2D Finite Element Method (FEM) simulations, specifying thermal boundary conditions for edges is indeed done using thermalBC. However, when you want to model convection within the domain (i.e., the air inside the pipe), you need to use a different approach.

To specify that the elements in the air have a convection coefficient, you can use thermalProperties to define the thermal properties of the elements within the domain. This is different from applying boundary conditions on the edges.

According to me, you can follow the below mentioned approach:

1) You need to specify the thermal conductivity, density, and specific heat for the air region. Use thermalProperties to set these properties for the elements within the air region. You can refer to the following code snippet.

thermalProperties(thermalModel, 'ThermalConductivity', 0.054, ...
                               'MassDensity', 1.35, ...
                               'SpecificHeat', 1350,...
                               'RegionType','face'...
                               'RegionID',3);

2) Use thermalBC to apply the convection boundary condition on the edges where the air interacts with the pipe walls.

thermalBC(thermalModel, 'Edge', [1, 2, 3, 4], ...
                         'ConvectionCoefficient', 300, ...
                         'AmbientTemperature', 25);

Kindly adjust the region IDs and edge IDs according to your specific geometry.

For more information related to thermalProperties function, you can refer to the following documentation:

https://www.mathworks.com/help/pde/ug/pde.thermalmodel.thermalproperties.html

I hope it will help!

Regards

Zuber