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Topic of this week in our office: When to use FEA for thermal analysis and when to use CFD?

As many people know, we are not only selling Siemens software and hardware…we also use it on daily basis. And as many know, if you close FE guys with Simcenter 3D and CFD guys with STAR-CCM+ to one room, big discussions about analysis are also here on daily basis. This week, main discussion in TechSim was about thermal analysis and what is better to use for solving it…and that motivated me to write something about it.

Heat transfer and how to simulate it is o common engineering. In the past, analyzes have been performed mainly in FE due to their complexity, but this solution may not always be the best solution..

First a little about heat transfer. Heat can be transmitted by three main principles:: CONDUCTION (solids), CONVECTION (fluid) and RADIATION. To choose better solution (FEA or CFD), understanding your particular problem is essential.

Thermal analysis in FE allows:

• enter convention coefficient values

• define solid interface thermal resistance

• input radiation effects (based on ambient temperature, surface emissivity, view factor).

However, what you have to be sure about in temperature FE analysis is the predictability of convection an its correct description.  What does it mean in practice? When flow effects (in fluid/gas) are unpredictable, your boundary conditions and convention coefficicients can be uncertain and you should move to CFD. Another important thing is radiation. In the FEA, radiation must be defined by accurate emissivity and ambient conditions. In practice, this often leads to time-consuming procurement and an overall reduction in the efficiency of the process. o if the effect of radiation is not negligible, it is again advisable to switch to CFD, which is a more robust method for these cases.
 

CFD Solution of Thermal Analysis

In CFD analyzes it is easy to enter all necessary data and predict all three types of heat transfer. This means that if you have a complex model and you need to input convective coefficcients, conductive resistance and radiation effects.

So why to solve heat transfer in FEA? The answer is simple: if you can predict forced convection and radiation is negligible, FEA will lead you to the result faster.

Our little office struggle ended in a draw (also because Simcenter 3D and STAR-CCM + can both count both FEA and CFD) Conclusion? We go on in the same mode, CFD guys prefer STAR-CCM +, and FEA guys prefer Simcenter 3D for thermal analysis :DD

What they didn't teach you in school about heat transfer?