I'm having trouble with simulating the time taken for a section of an assembly to return to ambient temperature, after being brought up to 65 degrees C within 1 second, with the heat source immediately switched off thereafter. The assembly itself is a thin glass rod surrounded by a cuboid of a copper alloy.

The input conditions that I am using for the transient thermal simulation are convection effects upon the outer surfaces of the assembly, the initial temperature at 300K and the input temperature acting upon only the glass cylindrical rod of 65 degrees C.

Heat is meant to spread outwards from the heated point, causing the central glass rod to eventually cool to ambient temperatures. However, I am finding that the simulation accurately displays the time taken for the glass rod to heat up, but the temperature does not decrease after this point.

Is it likely that I am missing a setting in a transient simulation to allow me to observe the effects of heat loss, and the time taken for a point on the assembly to drop from the heated temperature of 65 degrees C to 300K?

Thanks,

Manpreet