Can I use an aluminium heatsink in a inox chimney?

Question

I have recently installed a pellet stove with an inox chimney. I realized that the chimney actually warms a lot and part of this heat ends up being dissipated outside the house (where chimney goes out).

I was thinking about ways of optimizing the system. It would be desirable to dissipate as much heat as possible inside since that's the goal of having such a stove.

Part of the chimney is hidden behind the stove and I was thinking of putting on this area some heatsinks to dissipate as most heat as possible inside the room.

Would an aluminium heatsink work? The chimney gets very hot (I haven't checked yet) and aluminium is used in systems up to 200 degrees as far as I know.

Would this be a good idea? would it work?

Answer 1

Most metal stacks are only rated for 5-600 degrees. Yes you can get them glowing red but we used to provide a magnet that had a temp gauge on it when we installed wood stoves.

I have seen fins added to the pipes but would urge caution if you make a cool spot on the pipe creosote will build up in that location, in the 70's we tried all kinds of things that did provide extra heat to the house, I know of 1 house that had copper tubing around the stack on the single wall section, where the copper was in contact the creosote built up in less than a year. Because of the spiral it created a "turbo torch" like fire that melted the stack and really smoke damaged a large section of the home including destroying the family room.

Back then we used a lot of "steam" bladders in the fire box, these were great for heating if the proper safeties were in place but required the plumbing to enter and exit the fire box usually through the refractory cement bottom. We put quite a few in to heat hot tubs back then but wood heat is not as popular so you don't see much of this today.

Use caution and know that the stack, if over heated, can melt aluminum, tin, etc, You may get more heat but watch out for creosote buildup.

Answer 2

How chimneys work: they carry exhaust gases up and out of your house because those gases are so much hotter than the ambient air. If you cool down this exhaust too much, it might not succeed in leaving your house, and those gases (e.g. carbon monoxide) will make you unhappy and/or dead.

The principle is sound -- extracting more heat from the exhaust is exactly what highly efficient condensing heating systems do, for example. But those systems usually have an electric blower to force the gases out. In your case modifying the chimney system is risky. The safe option would be to seek out a more efficient stove and chimney system that has been designed and tested together.