Transient heat transfer

General Questions
1

Hey,
I tried to carry out a heat transfer analysis. I created several blocks of different materials. I defined:

  • material models from a library, all of them had thermal properties defined
  • contacts: bonded
  • Initial temperature for all surfaces: 20 degrees
  • boundary condition temperature on one surface: 700 degrees
  • loads: radiation 0.5
    And I added models such as the boltzman constant. The problem is that the obtained results are not correct. The lowest temperature is below zero. I tried doing a steady-state analysis and the results were already correct. Where should I look for the problem? I have attached screenshots of the results and boundary conditions
    heat transfer
    heat transfer1502×1662 280 KB
2

Is the initial temperature applied to all nodes in the model (the whole part or parts - also inside) ? In transient analysis, heat will need some time to propagate but cold regions should use initial temperature. Sometimes it’s also because of too coarse mesh but I would check the initial conditions first.

3

Hey,
You’re right. The problem was caused by incorrect selection of objects. I selected all surfaces instead of objects and only external nodes were added. Thanks for help