Thanks for the input. I had read quite a while ago that some European wood stove manufacturers have been experimenting with this concept. (
https://www.sintef.no/en/projects/2021/pcm-stove/) But, maybe cost prohibitive? Industrial paraffin is presently about $1355/ ton. It would take no where near a ton though. The heat exchanger would need to be liquid tight as the wax does melt (hence, the phase change). I believe the paraffin can be formulated to work at the temp. needed for the exhaust gases. I am thinking of greater "acceptance" into the market if someone like Liberator Rocket stove produced a "accessory" for mass heat storage for their stoves with an "add-on heat battery". Something that could be adapted more easily into existing homes. The concept of these heaters is so exceptional, I don't know why they are not used more. But I would guess lack of knowledge that they exist, and the fact that they are site-built which some people will just not take on ... and is an impediment to acceptance with building codes and insurance companies. The paraffin PCM does work the same as a masonry mass, in that it releases heat long after the fire is out. It does it more effectively because of the latent heat energy. Was wondering if someone possibly experimented with the concept.
that is thin and flexible enough to "bend" to the round shape of the barrel. Then bolting it to the barrel. Possibly add a sheet of heat transfer film between the aluminum and the steel barrel).