More heat from the flue pipe

[awoodman]

I came across these heat exchanger ideas.............The up draft type and the down draft type.

 

[Todd]

I wouldn't want to ruin the looks of my stove with one of those creosote factories.

 

[Backwoods Savage]

Robbing heat from a flu (now a flew) is one of the worst things you can do. The heat is needed for proper draft. And like Todd stated, I'd hate to ruin the looks of a good stove with one of those.

 

[quads]

Many people made double barrel stoves (one barrel on top of the other) that worked on the same principle. Northern Tool used to sell a kit to make a double barrel stove, maybe they still do. I don't think I would try to heat the house with one, but I had a homemade single barrel stove in a pole building.

 

[spirilis]

FWIW, the second pic is roughly what a Rocket Mass Heater stove uses. Except it doesn't use a metal woodstove underneath, it uses a masonry firebox to the side with unlimited air supply (ala masonry heater) and the flue exit passes through a thermal mass of some kind. With a metal woodstove where firebox temps need to be kept under control via air restriction, both of these ideas are stupid.