thermodynamic related.
temperature
pressure
initial conditions as they apply to model regions and surfaces and volumes
it is important to use simple enough and representive physical mesh model
both to simplify boundary definition and improve simulation speed complex regions require tighter mesh and cuspid or broken surfaces and surfaces tag will also. so model mesh is best acquired from clean simplified solidbody models
gaps and materials matter of course and things like air gaps, epoxied windings and thermal paste and oil film are tricky to represent but can be done. of course the pressure vessel material and deformation characteristics can be a factor and it may be that for simulation of that you hold temp constant or not.. so boundary condition is such broad topic and definition . it can include material change and also bulk transfer characteristic and material properties associated with heat transfer in solids and fluids... including phase change and eutectic transitions or what ever parameter is populated for model. There is no magical simulation. the results are based on mesh decomposition to get massive number of linear equations the and application of traditional formula to get solutions. and many cases do not converge if not set up correctly and take forever or crash.
takes a long time to do accurate and complex model and small geometry and boundary definition errors resulting in implied continuity or lack there of will result in total garbage results. lots of ways to get garbage result from these tools ..he he
especially if not selecting library material
similar to required inputs for closed and or steady state systems . to be fair its been a brief age since i used these products but i imagine its only incrementally improved