Hi @msaygin, When you have two different geometry objects that are in contact and have the same material, both the DEVICE solvers (CHARGE, HEAT) will combine the geometries to create a single domain. This particular behavior allows users to create complex structures by combining simple primitives. However, in your case since the solver is combining the lead and the heater together and converting it into one domain, you no longer have a heater. One workaround for you would be as follows:
Create a copy of the heater material in the material database. Then in your simulation assign the main material to the lead and the copy to the heater (or the other way round, it doesn’t matter). Now when you run the simulation the solver will not combine the lead and the heater since to the solver these now have different materials assigned. However, the simulation result will be accurate since the materials in both regions are identical in their thermal properties. Please let me know if you have any further questions.