Temperature fields

Thermal analysis allows temperature fields and heat flows to be determined by calculation. The following physical transfer mechanisms can be taken into account:

• conduction
• convection
• radiation

Problems involving the calculation of temperature fields and heat transfer can be solved either with finite element analysis (FEA) or with flow analysis (CFD).
The key difference between the two methods is that a flow analysis includes the flow domain in addition to the solid bodies. This allows mass transport and the resulting heat transfer coefficients (alpha values) to be determined realistically.

A finite element analysis, by contrast, can only represent solid bodies. The heat transfer coefficients have to be prescribed and must therefore either be known in advance or determined analytically. The advantage of finite element analysis over flow analysis lies in the lower modelling effort and the reduced computation times.

A coupled thermal-mechanical analysis allows the thermo-mechanical stresses resulting from the temperature field to be determined.

Steady-state temperature fields

In a steady-state thermal analysis the temperature field is independent of time. This corresponds, for example, to the steady final state of components after heating up or cooling down, such as in continuous operation.

Transient temperature fields

Unlike a steady-state calculation, a transient analysis accounts for the temperature history over time. Temperature changes result, for example, from a heating process or from changed operating parameters. The heat stored in or released by the component material (heat capacity) is taken into account in the analysis. A transient analysis is carried out whenever it is not certain that the final state produces the most critical loads or stresses.
The time-dependent mechanical loading resulting from the temperature distribution can then be determined by a coupled thermal-mechanical analysis (multiphysics).

Electro-thermal temperature fields

In the simulation of electrically-thermally coupled systems, heat is generated by the current flow — either directly via ohmic resistance (Joule heating) or by induction heating of components.
Transient analyses allow the time-dependent heating of the components to be simulated and conclusions drawn about the resulting temperatures.

Current-dependent temperature of a fuse