FEATool Multiphysics v1.10
Finite Element Analysis Toolbox
This example models resistive Joule heating where the resulting current from an applied electric potential will heat a thin spiral shaped Tungsten wire, such as can be found in incandescent light bulbs. The filament reaches an equilibrium temperature where the internal heat generation is balanced by radiative heat loss through the boundaries.
Two physics modes are involved, conductive media DC for the electric potential V, and heat transfer for the temperature T. Since the coupling is one way where only the heat transfer source term depends on the potential, the model will be solved in two steps. First for the electric potential, and then for the temperature using the pre-calculated potential, this saves computational time.
This model is available as an automated tutorial by selecting Model Examples and Tutorials... > Multiphysics > Resistive Heating in a Tungsten Filament from the File menu. Or alternatively, follow the step-by-step instructions below.
The filament geometry will be imported from an STL file Instead of creating it with the built-in CAD tools.
The built-in grid generator does not support imported CAD geometries so the external Gmsh grid generator is recommended (Gmsh will automatically be downloaded and installed if not available when selected).
5e-4into the Subdomain Grid Size edit field.
1/52.8e-9into the Electric conductivity edit field.
19.25e3into the Density edit field.
133.9776into the Heat capacity edit field.
173into the Thermal conductivity edit field.
1/52.8e-9*(Vx^2+Vy^2+Vz^2)for the temperature source term, effectively coupling the gradient of the electric potential to the temperature field.
Apply a potential difference of 0.2 V between the two ends.
0into the Electric potential edit field.
0.2into the Electric potential edit field.
5.670367e-8into the Radiation constant edit field.
80+273.15into the Ambient temperature edit field.
The end boundaries are assumed held at room temperature.
20+273.15into the Temperature edit field.
After the problem has been solved FEATool will automatically switch to postprocessing mode and here display the computed electric potential.
To solve for the temperature field, switch back to Equation mode activate the heat transfer physics mode and de-activate the electric potential.
The current solution has to be used as initial guess to use the computed potential since it is deactivated, also decrease the Non-linear relaxation parameter to help with convergence.
0.8into the Non-linear relaxation parameter (ratio of new to old solution to use) edit field.
After the solver has converged, plot the temperature and verify that the maximum temperature is around 690.
The resistive heating in a tungsten filament multiphysics model has now been completed and can be saved as a binary (.fea) model file, or exported as a programmable MATLAB m-script text file, or GUI script (.fes) file.