Thermal analyses are generally performed to determine temperature fields, peak temperatures and heat transfer behaviour. The results are frequently used to determine whether peak temperatures are excessive, or as an input in a stress/deflection analysis. Thermal analyses can assess steady-state or transient behaviour, and can include non-linearities.
Examples of thermal analyses performed by Eatec Engineering Analysis are shown below.
Assessment of a squirrel cage motor
An assessment of a squirrel cage motor was undertaken requiring the residual stresses due to the manufacturing process to be included. In order to achieve this, a transient thermal analysis of the rotor was performed to determine the temperature profiles which occurred during the brazing process.
An FE model of a segment of the rotor was generated, representing the steel laminates, copper bars, cage end rings and braze. The thermal resistances at the interfaces were included in the model along with the heat transfer coefficients on the outer surfaces.
A transient thermal analysis was performed to represent the heating of the rotor, the addition of the braze and the subsequent cooling.
The temperature fields were used in subsequent analyses to determine the residual stresses, the stresses occurring during operation and the fatigue life of the rotor.
Assessment of a rotating drum
An assessment of a drum used in a process plant was required to confirm that it would have an acceptable fatigue life. As part of the assessment, transient thermal analyses were performed to determine the temperature distributions within the drum as it was heated up and cooled.
The FE model included the effects of conduction and convection, along with the thermal resistances which occurred at bolted connections.
The calculated temperature fields were applied in a stress analysis, along with mechanical loads, in order to determine the deformation and stresses which occurred during start-up, normal shut-down and abnormal shut-down. The stress ranges and mean stresses were then used to predict the fatigue life of the drum.