This is somewhat confusing.
The so called "vapor" would carry a unit of thermal energy to the point where "vapor" can expand into, most likely, to the opposite end of metal tube where "vapor" is held. This is in assumption that "vapor" can travel there, that vaporized liquid is moving inside sealed enclosure.
Now, what happens when you heat up liquid inside sealed enclosure? A liquid would start expanding into a gas, creating internal pressure several orders of magnitude of starting pressure (if it can expand). The case can be easily demonstrated with steam engines or frozen water, where in both cases base liquid expands to create more pressure than at liquid state.
At some point of time thermal saturation can be reached to have all of the liquid converted into gas (again, if pressure is maintained boiling point of liquid will change dramatically, so higher temperatures are required for liquid -> gas conversion), at which point we have some nice steam pipe about to burst into small explosion due to all of the accumulated pressure.
In short, I find it hard to believe that a small sealed system would be used to convert liquid into vapor just to transfer heat over short distance due to all of the pressure involved. It would be believable to use liquid which can transfer heat much more efficiently than copper.