Clearly, I haven't been using the Thermal license much lately so please excuse me if this gripe has been hashed out before.
When creating a Thermal model you can apply a Prescribed Temperature boundary condition. The Help files state clearly that a boundary condition and an initial temperature are all that are needed to run a study. Okay, so I'll assign a Prescribed Temperature the external surfaces of, say, 100F. Then in the Study, I'll specify an Initial Temperature of, say, 500F. The study should then be able to determine the heat transfer values (flux, gradients, time, etc), right. Nope, it barks at you and says that "Prescribed temperatures and Initial temperatures MUST be the same". Curious.just how does heat actually flow in this arrangement? For grins, I complied and attempted to run a study.error, "There are no temperature differences blah blah blah". No kidding!
My work around (Gee, one must come up with a lot of work-arounds for Creo) is to apply a high convection condition and a changing bulk fluid temperature to the surface with changing temperature instead of the prescribed temperature which cannot change. It gets one pretty close.