I have tried it, but must conclude there is no way to do this. I also tried to do it by exluding the middle plate, and including another middle plate on the same place. But the solver recognizes a difference in geometry. There is a conflict in initial temperatures, because its defined twice.
Please contact you local VAR and do an enhancement request, it would be a very usefull option to select what initial temperature should have priority.
I have not tried yet SW2016 but it may be able to individually output/input field values that belongs to preliminary defined in the model sub-domains. Those sub-domains could be also entirely in the fluid if disabled (unchecked) in the Component Control list. Check on that enhancement of SW2016 by calling your SW Provider.