Burn Phases

[murphyslaw1978]

Are there only 2 burn phases - off-gassing and coaling? Also, does anyone have a chart showing heat output over time in each respective phase?

 

[HotCoals]

That's quite a order to fill...lol.
Throw burn tubes or a cat in the mix and all kinds of diff wood at various levels of being seasoned and there are a few variables.
I hear where there is smoke there is fire but most of the time I can't see the fire..it's usually choked way down and besides my glass is usually to dirty..lol.

 

[Battenkiller]

I hear where there is smoke there is fire but most of the time I can't see the fire..it's usually choked way down and besides my glass is usually to dirty..lol.

Which brings up the third phase of burning...

The chimney fire.

 

[HotCoals]

I hear where there is smoke there is fire but most of the time I can't see the fire..it's usually choked way down and besides my glass is usually to dirty..lol.

Which brings up the third phase of burning...

The chimney fire.

All clean here thanks!
Cat does its job...trust me I been looking.

 

[soupy1957]

I had heard (and read) that there were 3 phases of the burn. I'll see if I can find a chart.

-soupy1957

 

[murphyslaw1978]

Wikipedia does show 3 phases:

Preheating phase, when the unburned fuel is heated up to its flash point and then fire point. Flammable gases start being evolved in a process similar to dry distillation.

Distillation phase or gaseous phase, when the mix of evolved flammable gases with oxygen is ignited. Energy is produced in the form of heat and light. Flames are often visible. Heat transfer from the combustion to the solid maintains the evolution of flammable vapours.

Charcoal phase or solid phase, when the output of flammable gases from the material is too low for persistent presence of flame and the charred fuel does not burn rapidly anymore but just glows and later only smoulders.

 

[CTYank]

Wikipedia does show 3 phases:

Preheating phase, when the unburned fuel is heated up to its flash point and then fire point. Flammable gases start being evolved in a process similar to dry distillation.

Distillation phase or gaseous phase, when the mix of evolved flammable gases with oxygen is ignited. Energy is produced in the form of heat and light. Flames are often visible. Heat transfer from the combustion to the solid maintains the evolution of flammable vapours.

Charcoal phase or solid phase, when the output of flammable gases from the material is too low for persistent presence of flame and the charred fuel does not burn rapidly anymore but just glows and later only smoulders.

First, there's evaporation of water.

The above sounds like these are distinct processes. In fact, they largely proceed in parallel: while some coals on the exterior of a piece are glowing, some wood in the core is having water cooked out, for instance. The description of the "charcoal phase" seems dismissive, given the typical heat output there, unless everything's banked in ash.

 

[BrotherBart]

http://woodheat.org/index.php?option=com_content&view=article&id=59&Itemid=69

 

[Battenkiller]

That's quite a order to fill.

This is the best answer so far IMHO.

I was disregarding the charring stage because the OP was concerned with heat output. Pyrolysis is a heat input reaction.


The proportions of gases produced to charcoal produced are burn-rate dependent. Faster burns produce more smoke, slower burns produce more charcoal. Faster burning woods produce more smoke and less charcoal than slower burning woods. Pine leaves fewer coals but makes more smoke compared to black locust. Introducing more air will speed up the burn rate and skew the proportions to the smoke-producing side.

As far at heat output rate, well, smoke burns tons faster than charcoal because it is a gas. Given the exact amount of air for perfect mixing, it will burn as fast as the smoke is introduced. There is a lot more heat in a pound of charcoal, but it takes a long time to burn so the rate of heat produced is low. Unless you're trying to set a low wood consumption record, most of us are concerned with the rate of heat output rather than where the total amount is derived from. I like active flame because it gets the stove hotter, but the wood disappears faster. That's where the higher heat output rate comes from, by burning more wood faster.

In general, a declining fire will produce less and less heat per hour as the internal flue temps drop and draft gets progressively lower in strength, meaning less air is being drawn into the stove. A charcoal forge has a tuyere at the bottom that forces air directly through coal bed. This can be a powerful electric motor, a hand-crank blower, or a great bellows like smiths of yore used. By forcing air through the coals in an artificial manner, higher burn rates of charcoal are possible, and higher heat output is the result. Your stove doesn't work that way, so you are faced with a steadily weakening engine as the flue gets colder and colder. Eventually, things come to a halt. The ashes may provide enough insulation to keep those coals hot for days, but there will be no noticeable heat output from the stove at that point.


BB... is that what JG said? I hate to cut and paste, or provide links to technical information. It's much more fun to pretend I figured all this stuff out on my own and didn't get it from some Shelton book. ;-)

 

[BrotherBart]

BB... is that what JG said? I hate to cut and paste, or provide links to technical information. It's much more fun to pretend I figured all this stuff out on my own and didn't get it from some Shelton book. ;-)

Why should I even spend time thinking about it? I know for sure that you are gonna be along shortly. :cheese: I am scientifically challenged. I am more of the "Oh look. Fire! Fire make heat. Keep me warm." school.

I was like you in math classes. I wanted to know why, not just accept theorems. More than one teacher advised that we were just gonna accept them and move on rather than spend a couple of thousand years redeveloping them. :-S

 

[Battenkiller]

I was like you in math classes. I wanted to know why, not just accept theorems.

I'm mathematically challenged. My brain hemorrhaged at the end of Calc II. The very thought of going on to differential equations gave me tunnel vision on the drive to school. Seriously. I decided then and there to drop the notion of engineering school and become a biology major instead. A lot more flexibility with the truth there.

 

[Backwoods Savage]

To me there are 3 phases for sure.

1. Put wood in stove.

2. Wood burns.

3. Reload stove.

 

[Hanko]

most people three phases are two wire hook up three wire fuk up

 

[murphyslaw1978]

http://woodheat.org/index.php?option=com_content&view=article&id=59&Itemid=69

I like the inclusion of the water phase - thanks for that. It explains so many things going on prior to actual combustion. I have some red oak the sits out in the cold and doesn't burn well compared to the white oak sitting in the living room.

 

[murphyslaw1978]

That's quite a order to fill.

This is the best answer so far IMHO.

I was disregarding the charring stage because the OP was concerned with heat output. Pyrolysis is a heat input reaction.


The proportions of gases produced to charcoal produced are burn-rate dependent. Faster burns produce more smoke, slower burns produce more charcoal. Faster burning woods produce more smoke and less charcoal than slower burning woods. Pine leaves fewer coals but makes more smoke compared to black locust. Introducing more air will speed up the burn rate and skew the proportions to the smoke-producing side.

As far at heat output rate, well, smoke burns tons faster than charcoal because it is a gas. Given the exact amount of air for perfect mixing, it will burn as fast as the smoke is introduced. There is a lot more heat in a pound of charcoal, but it takes a long time to burn so the rate of heat produced is low. Unless you're trying to set a low wood consumption record, most of us are concerned with the rate of heat output rather than where the total amount is derived from. I like active flame because it gets the stove hotter, but the wood disappears faster. That's where the higher heat output rate comes from, by burning more wood faster.

Good explanations. I just figured there were some tests done on this. It would be interesting to see the same type of wood used in a multitude of experiments using graduated temperatures and air settings. The variables are still many, but I'm guessing the charts would still be effective at explaining just how much heat can be expected from each of the phases.

In general, a declining fire will produce less and less heat per hour as the internal flue temps drop and draft gets progressively lower in strength, meaning less air is being drawn into the stove. A charcoal forge has a tuyere at the bottom that forces air directly through coal bed. This can be a powerful electric motor, a hand-crank blower, or a great bellows like smiths of yore used. By forcing air through the coals in an artificial manner, higher burn rates of charcoal are possible, and higher heat output is the result. Your stove doesn't work that way, so you are faced with a steadily weakening engine as the flue gets colder and colder. Eventually, things come to a halt. The ashes may provide enough insulation to keep those coals hot for days, but there will be no noticeable heat output from the stove at that point.


BB... is that what JG said? I hate to cut and paste, or provide links to technical information. It's much more fun to pretend I figured all this stuff out on my own and didn't get it from some Shelton book. ;-)

 

[DonNC]

I dont know about the phase but once i get a few pieces of really dry wood fully engulfed, I turn the air all the way down and then something cool happens. In short order the wood stops burning but the fire does not go out. It jumps up to the tubes on the ceiling of the stove and stays there. Awesome thing to watch. The stove runs about 560 and stays there when that happens. when it looks like its about to stop I open the air a little until there is a bit of flame at the bottom ...just a little... and then the top picks up again. The book says this is the most efficient setting

Its the really cool looking phase

 

[Big Al]

I dont know about the phase but once i get a few pieces of really dry wood fully engulfed, I turn the air all the way down and then something cool happens. In short order the wood stops burning but the fire does not go out. It jumps up to the tubes on the ceiling of the stove and stays there. Awesome thing to watch. The stove runs about 560 and stays there when that happens. when it looks like its about to stop I open the air a little until there is a bit of flame at the bottom ...just a little... and then the top picks up again. The book says this is the most efficient setting

Its the really cool looking phase

The slpendor of the secondary burn light show. I call it Caveman TV. I never miss an episode.......

 

[DonNC]

I dont know about the phase but once i get a few pieces of really dry wood fully engulfed, I turn the air all the way down and then something cool happens. In short order the wood stops burning but the fire does not go out. It jumps up to the tubes on the ceiling of the stove and stays there. Awesome thing to watch. The stove runs about 560 and stays there when that happens. when it looks like its about to stop I open the air a little until there is a bit of flame at the bottom ...just a little... and then the top picks up again. The book says this is the most efficient setting

Its the really cool looking phase

The slpendor of the secondary burn light show. I call it Caveman TV. I never miss an episode.......

LOL caveman TV!
I was so amazed by that Im calling my wife into the room to look. She looks...says mm hmm...and goes back...but not me... I cant move away... like the 4th qtr of the Pitt Balt game last weekend. Amazing.

 

[Big Al]

I dont know about the phase but once i get a few pieces of really dry wood fully engulfed, I turn the air all the way down and then something cool happens. In short order the wood stops burning but the fire does not go out. It jumps up to the tubes on the ceiling of the stove and stays there. Awesome thing to watch. The stove runs about 560 and stays there when that happens. when it looks like its about to stop I open the air a little until there is a bit of flame at the bottom ...just a little... and then the top picks up again. The book says this is the most efficient setting

Its the really cool looking phase

The slpendor of the secondary burn light show. I call it Caveman TV. I never miss an episode.......

LOL caveman TV!
I was so amazed by that Im calling my wife into the room to look. She looks...says mm hmm...and goes back...but not me... I cant move away... like the 4th qtr of the Pitt Balt game last weekend. Amazing.

Yep. I've lingered many a night past my bed time, lying on the floor in front of the stove, mesmerized..........

The wife thinks it looks cool but she won't sit there and stare at it for any lenght of time.

 

[Battenkiller]

Lady BK is a dedicated fire watcher. Every summer night we can, she's got the chiminea stuffed with dry wood. I mix the drinks and grab the cigars while she finishes the dishes, and she just can't wait to go out and strike that match and sit back for the show. If it's buggy, we'll go out to her woman cave (screened-in gazebo) and have a fire in her fire pit there. We'll sit there for hours, mostly in silence, just watching the fire and mentally taking note of how the fire shifts, trying to predict when and where the next good spot to drop a split will open up. Same on our summer camping vacations. It's the highlight of her day, really.

So... I just asked her for her thoughts on secondary displays. An exact quote: "Eh... Well, I think they're pretty cool looking, but it's not something I'd want to sit around and watch or anything."


There goes that bargaining chip out the window. :-S

 

[Big Al]

Lady BK is a dedicated fire watcher. Every summer night we can, she's got the chiminea stuffed with dry wood. I mix the drinks and grab the cigars while she finishes the dishes, and she just can't wait to go out and strike that match and sit back for the show. If it's buggy, we'll go out to her woman cave (screened-in gazebo) and have a fire in her fire pit there. We'll sit there for hours, mostly in silence, just watching the fire and mentally taking note of how the fire shifts, trying to predict when and where the next good spot to drop a split will open up. Same on our summer camping vacations. It's the highlight of her day, really.

So... I just asked her for her thoughts on secondary displays. An exact quote: "Eh... Well, I think they're pretty cool looking, but it's not something I'd want to sit around and watch or anything."


There goes that bargaining chip out the window. :-S

That's an interesting conclusion. I wonder why the different attitude toward secondaries?

Cool that you can sit and watch in silence for so long. Speaks volumes about your marriage.

Of course, I had a marraige like that once, though the silence wasn't comfortable, mutal, or a positive sign. >:-(

 

[daleeper]

Lady BK is a dedicated fire watcher. Every summer night we can, she's got the chiminea stuffed with dry wood. I mix the drinks and grab the cigars while she finishes the dishes, and she just can't wait to go out and strike that match and sit back for the show. If it's buggy, we'll go out to her woman cave (screened-in gazebo) and have a fire in her fire pit there. We'll sit there for hours, mostly in silence, just watching the fire and mentally taking note of how the fire shifts, trying to predict when and where the next good spot to drop a split will open up. Same on our summer camping vacations. It's the highlight of her day, really.

So... I just asked her for her thoughts on secondary displays. An exact quote: "Eh... Well, I think they're pretty cool looking, but it's not something I'd want to sit around and watch or anything."


There goes that bargaining chip out the window. :-S

You do realize that's the best way to get you out of the house when smoking those cigars, don't you?

 

[Battenkiller]

That's an interesting conclusion. I wonder why the different attitude toward secondaries?

Cool that you can sit and watch in silence for so long. Speaks volumes about your marriage.

Of course, I had a marraige like that once, though the silence wasn't comfortable, mutal, or a positive sign. >:-(

I feel the same way, really. We're just so into a natural open fire. The sounds, the look of the yellow flames, the occasional waft of cherry smoke... all part of the ambiance. We have a nice fireplace to use in the living room, but the place is usually too warm to light it. Don't get me wrong, if the stove was upstairs (and it actually had glass in it) I'd watch away most evenings, but it just ain't like looking at the real McCoy.

Marriage... yeah, we have a great one. Ups and downs, just like everybody else, but she's my very best friend in the world, no doubt about that. She's beautiful, funny as hell, smart as a whip, generous to a fault, not afraid to get dirty with hard work, and she even likes cigars and whisky. I mean, c'mon... how many guys can sit around sipping single-malt and smoking cigars with their best friend and then go rumple up the sheets later on that night? ;-)

The silence, though, is just something that seems to evolve out of necessity. It's like being trapped on a desert island with your best fishing buddy, and he says, "Did I tell you the time I caught...", and you've heard the same story 657 times in the last year alone. There are no real surprises anymore. Very comfortable, but a bit sad. Sometimes I think we should divorce for a couple of years and then get back together, get to know each other all over again. But I'd miss the hell out of her... and all of her charms.

 

[HotCoals]

That was beautiful post Battenkiller.

 

[oldspark]

BK is your favorite song "do you like pina coladas"? :lol: