Anyone attach aluminum or steel heat sinks to your stove?

Reporting back on my addition of heat sink fins to the Kodiak---I realize we're 20% under normal degree days, but I'm using MUCH LESS coal this year, and emptying ashes every 3 days vs. 2 days. I have to think the heat sinks are working. Ashes are more complete, much less totally unburned coal in the pan. IR gauge shows the fins (240-300 degrees)---hotter than my stack temp (120 degrees), and fan usage is cooling the fins down predictably. I keep the MPD closed except for shaking/filling. Overall I have 4 times the surface area via fins than the slab sides, much more heat is radiating/convecting to the room.

My supplemental oil usage is cut in half also, again I realize the warm winter is a factor here; but I'll probably use half the annual amount. (Last year 400 gallons)

I couldn't be happier, and I suggest to anyone skeptical to add as much finned area as possible. The heatsink compound is also necessary, I left an area untreated and can see the temp difference. I thought it wasn't needed, but it really makes a difference.

Best of luck...

I have been seriously thinking about doing the same thing, so I was happy to find your thread. But if I put a straight-edge on the side of my stove, horizontally, there is a noticeable bowing that would make it hard to get good contact. Vertically there is less bowing, but still some. Has that Dow 340 compound stayed in place for you to improve heat transfer? I figure for extremes the transfer compound (or the right type of gasket?) would have to be good up to 900 or 1000 degrees. I checked JB Weld, and as I recall it is good only to 600*. So I'm still looking for the right material. Suggestions, anyone?

Mine was bowed also, as the steel is formed (bent) but the aluminum lays flat via the bolts drawing it to the side. The Dow 340 I'm told is good to 400 degrees? I'm sure there's something out there better, see earlier posts in my thread. I don't know how critical it is if you are running it so hot, with or without compound 50 degrees of transfer is negligible as you are looking to bleed heat off of it anyway. If the fins are anywhere from 400 or higher they're really hot relatively anyway.
Think about setting a piece of aluminum on the flat top surface, it'll be close to the temp of the surface it's setting on. You won't remove heat as quickly as it's transferred to the heat sink. I have a fan trained on one area for test, it can't remove enough heat to make a difference worth worrying about.

Again, it's either to the room or up the chimney!

Once you tighten the bolts, any piece of aluminum will bend to the contour of a couple degrees of arc. Trust me... I was worried about the steel/aluminum differential of expansion etc, it doesn't mean a thing. Just think MULTIPLES OF SURFACE AREA to dissipate heat. Best $$$ you can spend on ebay. Lots of heat sinks out there.

For the "Not-so-Fancy"

Welding works if you use steel fins...and no heatsink compound will be needed either.

Ever have a peak under a "Yukon's" furnace jacket?

McGiever wrote:For the "Not-so-Fancy"

Welding works if you use steel fins...and no heatsink compound will be needed either.

That too was my thought, but NOT in my spouse's opinion which carries more weight than mine.

"How are we saving money if you keep SPENDING more money?" Good point. My 'black energy' program here is usually vetoed initially, hard to project savings through the skepticism...

63roundbadge wrote:My 'black energy' program here is usually vetoed initially, hard to project savings through the skepticism...

Mine too, usually. But the other day we were discussing a different coal stove and she said, "Well, this is your thing, so go ahead with whatever you want." It was even said in a normal, reasonable, non-disapproving tone of voice. I looked twice to make sure it was the same woman as for the last 41 years, and it was. So, I will let that approval remain as the decision of record, and I will NOT ask again, lest the verdict should change.

hmm , from what I've read so far , coal fires are very different "beasts" from wood fires...
I would suggest to cover the whole stove with aluminum heatsinks, big in height with lots of fins + encase them all in a thin steel sheet and add a big cfm blower DOWN in order to blow air over them and heat upwards(hot air rises, right? "a kick" from a fan wouldn't hurt).
The addition of a heat exchanger would be overkill in these conditions?!
Now , I wonder why didn't all those big coal stove manufacturers didn't think of this and more intriguing , why didn't they manufactured allready something similar to this?
Or they did and I have no ideea?!

gowriel wrote:Or they did and I have no ideea?!

They did. Some antiques provided for extended flue passages that could be switched in and out. Others provided means for a drum to added on top. Some modern stoves use a double skin with a blower to increase heat exchange efficiency.

Don't forget a certain amount of heat in the flue is necessary to maintain draft and also to prevent condensation of corrosive flue gas.

franco b wrote:Don't forget a certain amount of heat in the flue is necessary to maintain draft and also to prevent condensation of corrosive flue gas.

Very true. I think I've pretty much hit the 'sweet spot' on my Kodiak for pulling heat without compromising or changing the draft. I can imagine aluminum fins are not factory because they're easily damaged. However, cast iron or steel integrated into the shell would be nice and add to the efficiency (imo). There's probably a reason be it aesthetic or financial for the absence of them from the factory.

gowriel wrote:hmm , from what I've read so far , coal fires are very different "beasts" from wood fires...
I would suggest to cover the whole stove with aluminum heatsinks, big in height with lots of fins + encase them all in a thin steel sheet and add a big cfm blower DOWN in order to blow air over them and heat upwards(hot air rises, right? "a kick" from a fan wouldn't hurt).
The addition of a heat exchanger would be overkill in these conditions?!
Now , I wonder why didn't all those big coal stove manufacturers didn't think of this and more intriguing , why didn't they manufactured allready something similar to this?
Or they did and I have no ideea?!

They did think of it. They thought of it and put it into practice 100 plus years ago. It was called a circulator stove. Or you could get on that was both a radiant stove and a circulator at the same time, they called those, "Double Heaters."

A very good way to increase the convection efficiency of a stove is to break up the natural flow of air as it rises and is warmed by the stove. A skirt or band of flat metal around the middle and top of the stove greatly increases the turbulance of natural convection and thus heats better.

The bad thing about sucking too much heat out the fire too fast is that it lowers the overall temperature in the firebox and because of that combustion efficiency drops quite a bit. A stove with not enough radiant surface area or combustion area above the fire can render more heat with a blower, for example, but; at the cost of combustion efficiency.

63roundbadge wrote:cast iron or steel [fins] integrated into the shell would be nice and add to the efficiency

If you look at antique cast iron stoves, there were often fancy 3-dimensional designs cast into the surfaces. Other than esthetics, part of the reason was to increase radiant surface area, so I have read.

rberq wrote:

63roundbadge wrote:cast iron or steel [fins] integrated into the shell would be nice and add to the efficiency

If you look at antique cast iron stoves, there were often fancy 3-dimensional designs cast into the surfaces. Other than esthetics, part of the reason was to increase radiant surface area, so I have read.

Exactly, even the lettering of the maker and any wording increased surface area even in small amounts. My point was specifically for the Alaska Kodiak, which would make a great stove even better. The Kodiak's been in my estimation incredibly easy to use, easy on the eyes and as clean as a stove can be. The hopper feed is icing on the cake, perfect banking and run times.

wsherrick wrote:They did think of it. They thought of it and put it into practice 100 plus years ago. It was called a circulator stove. Or you could get on that was both a radiant stove and a circulator at the same time, they called those, "Double Heaters."

A very good way to increase the convection efficiency of a stove is to break up the natural flow of air as it rises and is warmed by the stove. A skirt or band of flat metal around the middle and top of the stove greatly increases the turbulance of natural convection and thus heats better.

The bad thing about sucking too much heat out the fire too fast is that it lowers the overall temperature in the firebox and because of that combustion efficiency drops quite a bit. A stove with not enough radiant surface area or combustion area above the fire can render more heat with a blower, for example, but; at the cost of combustion efficiency.

After some "rigurous reading" on the internet, I got to the conclusion that if someone wants to burn coal , this must be done in something very similar to a furnace with very good insulating properties(think of all insulating materials used in furnaces or even the space shuttle "bottom" ), to ensure good burning efficiency of the coal , and the resulted heat(wich could be quite high) to be captured in a big heat exchanger with thin "walls" sheet metal + a ventilator to move heat in the room from the heat exchanger!
I mean, this is my thinking after the advices from several members on this forum , a lot of reading about burning coal!
I started with a big metal box and I ended up from where I started:
burning efficiency and a thin sheet of stainless steel heat exchanger...
For the moment beeing , I'll "leave it " like that!

gowriel wrote:

wsherrick wrote:They did think of it. They thought of it and put it into practice 100 plus years ago. It was called a circulator stove. Or you could get on that was both a radiant stove and a circulator at the same time, they called those, "Double Heaters."

A very good way to increase the convection efficiency of a stove is to break up the natural flow of air as it rises and is warmed by the stove. A skirt or band of flat metal around the middle and top of the stove greatly increases the turbulance of natural convection and thus heats better.

The bad thing about sucking too much heat out the fire too fast is that it lowers the overall temperature in the firebox and because of that combustion efficiency drops quite a bit. A stove with not enough radiant surface area or combustion area above the fire can render more heat with a blower, for example, but; at the cost of combustion efficiency.

After some "rigurous reading" on the internet, I got to the conclusion that if someone wants to burn coal , this must be done in something very similar to a furnace with very good insulating properties(think of all insulating materials used in furnaces or even the space shuttle "bottom" ), to ensure good burning efficiency of the coal , and the resulted heat(wich could be quite high) to be captured in a big heat exchanger with thin "walls" sheet metal + a ventilator to move heat in the room from the heat exchanger!
I mean, this is my thinking after the advices from several members on this forum , a lot of reading about burning coal!
I started with a big metal box and I ended up from where I started:
burning efficiency and a thin sheet of stainless steel heat exchanger...
For the moment beeing , I'll "leave it " like that!

Guess what, you are talking about a Base Heater. What better insulator than the fire's heat itself around the out side of the fire and then a long path for the hot exhuast to follow to radiate most of of the available heat into the room. So if you made it like that you are on the right track.

@wsherrick : I haven't even started yet!
Too cold , too busy with other things, but as soon as the weather will be "hotter" than minus 15 degrees Celsius + a 10 km/h wind I'll probably get started...