Heat Pipe/Thermosyphon Used as Insulator

Heat pipes insulate the tundra from the heat of the oil in the Alaska Pipeline. Look at a picture of the pipeline. Even this might be stretching the definition of an insulator.

Heat pipes move heat. That's it.

I would not call them insulators.

I've been through thinking the figure below(a cross section of Flat Plate type heat pipe)

How about @ Th<Tc; where Th & Tc are temperatures correspondingly. I really wanted to evaluate at conductivity at that condition, either it could behave such like an insulator.

By theoretical analysis @ Th<Tc when all of the medium would be converted to saturated vapor state, heat transfer from top & bottom plate will be at mode of convection which will be minimal and I think this heat pipe will behave as insulator.

But if Th>Tc, heat pipe will be functional of transferring heat to other side of the plate.

I kinda think, this flat plate heat pipe could be utilized as upper cover/ceiling of cars, definitely only for tropical countries where fuel consumption might be less due to saving energy from air conditioning units. However, this cars will not be applicable for colder countries of course, the configuration tells, you'll get to be frozen inside.

Though water hammer effect is abit of an issue using heat pipe on moving cars.

I don't know but i think it will work.