Secondary combustion in a double barrel stove?

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turn_n_burn

Burning Hunk
Aug 14, 2015
174
Idaho
I recently had an idea, and I wonder how effective it would be. Yes, it's a barrel stove, but I would be using it in my shop, which is a steel building reinforced by cinderblocks and a thick concrete floor (very little fire risk). I've attached a couple sketches I did on the idea, and I want to get some opinions.

Basically, it's a standard double barrel setup. I've seen guys that have welded a baffle plate a few inches from the top of the the bottom barrel and run secondaries right underneath that, like you would see with a modern EPA stove. My design has the both secondary inlets at the back of the stove on the bottom barrel (one for each side of the firebox) that run about 3/4 the way to the door in the front. They are connected a 90 degree pipe elbow to a curved section of pipe running upwards to stay in contour with the inner wall of the barrel, then through another 90 degree elbow back into straight pipes that then run back to, and up, the chimney. I would use 8 inch steel pipe for the flue connecting the barrels to allow room for the secondary tubes to run inside and up to a few inches below the circulator baffle in the upper barrel,without creating a narrow choke point in the bottom flue pipe. My ultimate aim here is to give the air in the secondaries a long passage through the firebox, ensuring maximum heat transfer to the air. This is also why I run the tubes inside of the flue, to minimize heat loss in the superheated air going through them, as I want the secondary burn to happen in the upper barrel.

I've researched barrel stoves for years now, but I've never seen one with the secondary reaction exclusively in the upper barrel. I may run 3 or 4 pipes thru the upper barrel above the circulation baffle that I could hook a small blower up to, as many people have done. How well would this work?
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It might work, but ignoring the flame thrower you're going to get about using barrel+stove together in the same sentence...


Why do all that work in fabrication? You're going to have a lot invested in that stove. You can pick up a nc30 at home depot for less and have a great product that the insurance company will recognize.
 
It might work, but ignoring the flame thrower you're going to get about using barrel+stove together in the same sentence...


Why do all that work in fabrication? You're going to have a lot invested in that stove. You can pick up a nc30 at home depot for less and have a great product that the insurance company will recognize.

Guessing at - for the fun of it?

Not sure how well this would work at all. But seems to me the main purpose of the second barrel in these setups is for heat transfer. So if you move the major combustion downstream into the HX area, you are going to be losing more heat up the pipe.

Nothing like a good barrel stove thread. :)
 
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You drew up a plan about something you'll probably not do,

100 TIMES BETTER

than people who ask for advice on installs and try to take a "picture".

Well done, grasshopper.
 
First off, I love barrel stoves. Many memories from my youth heating our house in Alaska with one. There are many different barrel thicknesses, use a heave gauge barrel if you want it to last.

As to the secondary air in the upper barrel: I am guessing here too, full disclosure. You will be adding the air in too late in the burn cycle. The will be a cooling that has happened that far away from the flame and I doubt that you will be able to keep it reignited. Not sure how I would feel about secondary air in a barrel stove in the first place, but if I was installing it I would put it in the bottom barrel. The top barrel is really nothing more than a stack robber on a conventional wood stove.
 
Seems like a whole lot of effort to put into a stove made out of metal that thin. If you actually get temps high enough for secondary combustion I am betting it will burn through that barrel pretty quickly. I have seen many burnt out or melted barrels without the added heat of secondary combustion
 
I didn't realize barrel stove threads were so polarizing. This is nothing but a fun side project exploring stove thermodynamics. I'm not planning on heating my house with it. It may end up as a giant patio heater. I already have most of the material I need to build it, so cost is really not an issue, and I love a good, distracting, meandering side project. For as little use as it would get, I'm not concerned about barrels burning out.

My thinking was that the secondary burn would not be overly damaging to the upper barrel. The flames from secondary combustion, though quite hot, do not produce anywhere near the temperatures that the actual firebox (lower barrel) experiences from flames and the radiant heat from the coals. That's also why I thought of running the secondary tubes thru the inside of the flue pipe, to maintain the secondary temps as high as possible to allow a complete burn. Plus, all we have around here to burn is Pine, Juniper and Fir, I don't plan on stuffing it full of hedge or locust and having a puddle of molten steel.

I think I will do it purely as an outdoor stove to start, run it for a season and check the results. Sure, it'll be hideously ugly, but I won't be cold out on the patio whilst having a smoke.

As for the flamethrower comment, no need to worry. I already own one ;)
 
I didn't realize barrel stove threads were so polarizing. This is nothing but a fun side project exploring stove thermodynamics. I'm not planning on heating my house with it. It may end up as a giant patio heater. I already have most of the material I need to build it, so cost is really not an issue, and I love a good, distracting, meandering side project. For as little use as it would get, I'm not concerned about barrels burning out.

My thinking was that the secondary burn would not be overly damaging to the upper barrel. The flames from secondary combustion, though quite hot, do not produce anywhere near the temperatures that the actual firebox (lower barrel) experiences from flames and the radiant heat from the coals. That's also why I thought of running the secondary tubes thru the inside of the flue pipe, to maintain the secondary temps as high as possible to allow a complete burn. Plus, all we have around here to burn is Pine, Juniper and Fir, I don't plan on stuffing it full of hedge or locust and having a puddle of molten steel.

I think I will do it purely as an outdoor stove to start, run it for a season and check the results. Sure, it'll be hideously ugly, but I won't be cold out on the patio whilst having a smoke.

As for the flamethrower comment, no need to worry. I already own one ;)
And as a fun experiment go for it by all means. The danger I see with threads like this is someone will read it and build one for their house not realizing your experiment was not meant for that.
 
The hate for barrel stoves is because the threads go like this:

A: How can I get more heat from my barrel stove. Also there is a funny smell when it burns.

B: Burn dry wood. Be careful or you'll burn your house down. Give us some pictures of the install.

C: Don't use a barrel stove. The barrels burn through.

A: Here are some pictures. My cousin said the smell might be my dog, he is pretty old.

B: Is that... the same stove you have fires in? Is it holding up a couch??

C: Don't use that barrel stove. It has already burned through. You will definitely burn your house down. Why is a couch touching the stove? It looks like it has a fire in it. Is this a photoshop?

A: I needed to stop the side of the stove from falling off so I pushed the couch up against it. I checked the tag and it is fireproof. The holes in the stove are not too bad, I have seen worse. I didn't come here for a lecture. Here is a picture of the dog, do you think the smell could be coming from him?

B: Well, you can get a much safer stove for under $1000. That and some dry wood will solve some of your problems. How are you venting this thing?

D: As per NTSME14D, subparagraph 11, "There shall be no rayon-upholstered furniture within 10 feet of a barrel stove, though these clearances may be reduced if a full time firefighter is garrisoned within 36 inches of the stove..." I don't see the firefighter in that picture.

C: The smell is coming from the COUCH because it is MELTING. Do not burn that stove and take the couch off of it.

A: I am not going to let some gummint bureaucrat tell me where to put my couch. I tried moving it and a burning log rolled out of the stove and singed my dog. Had to put it back. Everyone saying my wood was wet got me looking and it turns out that all the holes I shot in the roof to try to get that meth-head Earl off of there last summer are leaking water down into the living room wood pile, so some of the wood is pretty wet. I've seen wetter, though. Do you guys think a damper would help? This stove has to last another 10 years.

...and so forth.
 
Wow.
 
The hate for barrel stoves is because the threads go like this:

A: How can I get more heat from my barrel stove. Also there is a funny smell when it burns.

B: Burn dry wood. Be careful or you'll burn your house down. Give us some pictures of the install.

C: Don't use a barrel stove. The barrels burn through.

A: Here are some pictures. My cousin said the smell might be my dog, he is pretty old.

B: Is that... the same stove you have fires in? Is it holding up a couch??

C: Don't use that barrel stove. It has already burned through. You will definitely burn your house down. Why is a couch touching the stove? It looks like it has a fire in it. Is this a photoshop?

A: I needed to stop the side of the stove from falling off so I pushed the couch up against it. I checked the tag and it is fireproof. The holes in the stove are not too bad, I have seen worse. I didn't come here for a lecture. Here is a picture of the dog, do you think the smell could be coming from him?

B: Well, you can get a much safer stove for under $1000. That and some dry wood will solve some of your problems. How are you venting this thing?

D: As per NTSME14D, subparagraph 11, "There shall be no rayon-upholstered furniture within 10 feet of a barrel stove, though these clearances may be reduced if a full time firefighter is garrisoned within 36 inches of the stove..." I don't see the firefighter in that picture.

C: The smell is coming from the COUCH because it is MELTING. Do not burn that stove and take the couch off of it.

A: I am not going to let some gummint bureaucrat tell me where to put my couch. I tried moving it and a burning log rolled out of the stove and singed my dog. Had to put it back. Everyone saying my wood was wet got me looking and it turns out that all the holes I shot in the roof to try to get that meth-head Earl off of there last summer are leaking water down into the living room wood pile, so some of the wood is pretty wet. I've seen wetter, though. Do you guys think a damper would help? This stove has to last another 10 years.

...and so forth.


Post of the year! (So far!)
 
Actually, the barrel stove threads typically degenerate into an argument about what is and is not a garage, or an argument about what some local code says about unlisted stoves, or an argument over whether insurance company X will pay out a claim related to an unlisted stove in an outbuilding that may or may not be a garage.

My version's more fun, though.
 
Actually, the barrel stove threads typically degenerate into an argument about what is and is not a garage, or an argument about what some local code says about unlisted stoves, or an argument over whether insurance company X will pay out a claim related to an unlisted stove in an outbuilding that may or may not be a garage.

My version's more fun, though.
I did like your version. Very creative. I think most of us can agree that fire does not belong in barrels.
 
The hate for barrel stoves is because the threads go like this:

A: How can I get more heat from my barrel stove. Also there is a funny smell when it burns.

B: Burn dry wood. Be careful or you'll burn your house down. Give us some pictures of the install.

C: Don't use a barrel stove. The barrels burn through.

A: Here are some pictures. My cousin said the smell might be my dog, he is pretty old.

B: Is that... the same stove you have fires in? Is it holding up a couch??

C: Don't use that barrel stove. It has already burned through. You will definitely burn your house down. Why is a couch touching the stove? It looks like it has a fire in it. Is this a photoshop?

A: I needed to stop the side of the stove from falling off so I pushed the couch up against it. I checked the tag and it is fireproof. The holes in the stove are not too bad, I have seen worse. I didn't come here for a lecture. Here is a picture of the dog, do you think the smell could be coming from him?

B: Well, you can get a much safer stove for under $1000. That and some dry wood will solve some of your problems. How are you venting this thing?

D: As per NTSME14D, subparagraph 11, "There shall be no rayon-upholstered furniture within 10 feet of a barrel stove, though these clearances may be reduced if a full time firefighter is garrisoned within 36 inches of the stove..." I don't see the firefighter in that picture.

C: The smell is coming from the COUCH because it is MELTING. Do not burn that stove and take the couch off of it.

A: I am not going to let some gummint bureaucrat tell me where to put my couch. I tried moving it and a burning log rolled out of the stove and singed my dog. Had to put it back. Everyone saying my wood was wet got me looking and it turns out that all the holes I shot in the roof to try to get that meth-head Earl off of there last summer are leaking water down into the living room wood pile, so some of the wood is pretty wet. I've seen wetter, though. Do you guys think a damper would help? This stove has to last another 10 years.

...and so forth.

Can you please do one for the why can't I get my stove over 200 degrees threads too??

I do not know much about barrel stoves but I wanted to say your drawing was awesome. I am what my wife calls a "visual learner". I was pretty lost trying to figure out what you were talking about, the pictures cleared everything up. Good luck, be sure to keep us updated if you end up building it
 
Barrels come in many different thicknesses. As thin as 24 and as thick as 16 gauge, if I am remembering correctly. Just like stove pipe, use the wrong kind and it will burn through. Use a thicker one and it will last a very ling time. Saying a barrel will burn out quickly is similar to saying that a chimney liner will fail quickly because there are low quality liners on the market that do fail (my neighbor has a woodstove installed in his house and it is ran through B vent, talk about unsafe). The barrel stove we used in our Alaska house was made from a thick walled barrel, shortened 10 inches and had a cooktop on the front top of it. It lasted over 20 years of hard burning. Cranked out a LOT of heat too.

Saying that a barrel is not made to contain fire is no different than saying that a piece of plate steel is not intended as a stove, it was made to build a ship. Or that a stone is not intended for containing fire, but is intended to build buildings on. Cast iron is not for stoves, it is for sewing machine treadle bases. Barrels are nothing more or less that a round piece of steel with two ends on it. But, I do think that the secondary afterburner is pushing things a little bit.
 
Barrels come in many different thicknesses. As thin as 24 and as thick as 16 gauge, if I am remembering correctly. Just like stove pipe, use the wrong kind and it will burn through. Use a thicker one and it will last a very ling time. Saying a barrel will burn out quickly is similar to saying that a chimney liner will fail quickly because there are low quality liners on the market that do fail (my neighbor has a woodstove installed in his house and it is ran through B vent, talk about unsafe). The barrel stove we used in our Alaska house was made from a thick walled barrel, shortened 10 inches and had a cooktop on the front top of it. It lasted over 20 years of hard burning. Cranked out a LOT of heat too.

Saying that a barrel is not made to contain fire is no different than saying that a piece of plate steel is not intended as a stove, it was made to build a ship. Or that a stone is not intended for containing fire, but is intended to build buildings on. Cast iron is not for stoves, it is for sewing machine treadle bases. Barrels are nothing more or less that a round piece of steel with two ends on it. But, I do think that the secondary afterburner is pushing things a little bit.
Yes some barrels are thicker. But I would never think of using a stove made from 16 ga in my house. It is just to thin or my comfort. And if I wouldn't feel comfortable with the safety of it in my house I won't put one or recommend one for someone else
 
Aside from the metal being too thin, the barrel stove is handicapped by its shape. If you put the baffle and tubes in the top barrel, you are doing 50% of your combustion up at the flue exit.

If you put it in the bottom barrel, you can't fit much wood in there.

If you add a third barrel, you are going to have a serious creosote fire in the top barrel eventually, unless it has a gasketed door to permit regular cleaning.

Take that design and build it with steel plates instead of barrels, and you could end up with a project that is just as interesting but lasts longer and works better.

I think the allure of the barrel stove is 'old barrels are free', and a project that you have put so much thought into is not well served by the prerequisite that old barrels be involved.

Please don't be discouraged by our grouching, but do make sure the finished product is installed and operated safely.

I think it's super cool that you are designing and building stuff to see how it works!
 
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I completely agree with everything jetsam said it sounds like a cool project to mess around with but to me it seems like wasted work to put into a couple barrels
 
Jetsam, that was the most humorous analogy I have heard in many years and probably the most revealing and descriptive as well. I can see exactly what you're talking about.
 
How did your project turn out? I’m a barrel stove fan. Put the word Sotz in front of it and it’s surprising how many positive posts you’ll get.

I hope you pursued it. If so I’d like to hear more.