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Rectangular flame pathways in Wood Stoves, references needed  RSS feed

 
Posts: 20
Location: British Columbia, Canada
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I'm looking for references to this topic either as they relate to the rocket stove concept, or similar references to rectangular flame pathways used in other types of stoves, or heaters. If anyone had links to share on this topic I'd sure appreciate it.

As posted in a previous thread, I plan to build a Massless Rocket Heater with rectangular flame pathways, but I don't want to repeat other peoples mistakes. I did find the following reference on gassification that which used a 9cm X 12cm flame path which sounds promising:

http://stoves.bioenergylists.org/aprogasrocket

A Google search also turned up a thread on permies from 2010, but the outcome of that persons intention to use a rectangular heat riser was never commented on.

I have at least a month before it warms up here enough to work outside, so if anyone encounters further references I'll watch this thread for your posts.

Thanks!
Keith.
 
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Location: Upstate NY, zone 5
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I presume you have a particular reason for wanting to use rectangular flame pathways. If you share that, as well as what you want to use the heater for, people will be better able to give you the best answers instead of a narrow response to a specific question. I see that you are in Canada (near the Pacific, by some of your comments?) so information on your climate will be helpful in advising.
 
Glenn Herbert
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If you are looking for gasification as the Aprovecho article describes, you want a (small) batch box of the type perfected by Peter van den Berg and others. This could be built within the small square/rectangular footprint you mentioned elsewhere, using a metal bell for radiating instead of masonry for heat storage.
http://donkey32.proboards.com/thread/734/peterberg-batch-box-dimensions
 
Keith Coldrain
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Location: British Columbia, Canada
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Hi Glenn;
Unfortunately I'm not near the ocean. South Okanagan Valley which still sees winter temps of as low as -15C or +3F which is cold enough for my blood.

I live in a small travel trailer totally off the grid apart from my cellphone internet access with everything running off 12v from my solar panels and propane for heating cooking and refrigeration. I hoped to add a small supplemental wood heater/stove, preferably one that was removable for outside use in the summer. It gets hot here in summer and adding more heat inside by cooking makes it unbearable.

As for the choice of rectangular pathways, the design, (my own), I described in another thread allowed for a larger than typical sized batch box when combined with the rectangular pathways. The link I posted was only of interest to me because of the shape of the opening used.

Basically I want a larger batch box because I don't want to babysit the stove constantly waiting for its next feeding time, increased feed capacity seems to be the only option.

Thanks for that link. Looks like I have some reading to do there.

Keith.
 
Glenn Herbert
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From your comment that you could see warmer weather to test build outside in a month or two, I thought you were at lower elevation or tempered by the ocean.

Pretty much any rocket stove big enough to have a clean burn is going to drive you out in all but the coldest weather. I lived in a 16' travel trailer for a bunch of years, with a small gas heater in the wall. It takes really good insulation to keep one of those evenly warm. I would suggest looking into a water mass heat storage method rather than try to size the burn to accommodate mild as well as brutal weather. There is another thread somewhere about just that going on now... I can see if I can find it.
 
Glenn Herbert
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Here is someone else working on exactly the same issue...
http://www.permies.com/t/42496/wood-burning-stoves/Mass-heater-tiny-house
 
Keith Coldrain
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Location: British Columbia, Canada
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Thanks again Glenn, but I'm trying to avoid mass based heaters due to mobility issues. My trailer is single axle and neat it's weight capacity. I plan to use it in summer to ho gold panning and metal detecting.

One other use I have for the heater, would be for a temporary arched roof "greenhouse" style shelter I plan to assemble this summer for use as a foul weather work area and just a place where I can sit outside in relative comfort when its cold or rainy. Cabin fever is an issue in such small confines.

Keith.
 
Glenn Herbert
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I think you need some mass to temper the output of your heater in a small space, though it doesn't need to be masonry. A steel drum/tank that can be emptied for moving would work fine. You should be able to add a couple of jackposts or blocks to support the mass while stationary.

Having a water jacket surrounding the combustion zone (not touching it but insulated) would help to keep high temperatures safely away from combustible surfaces, too. A 55 gallon drum is 23" diameter, and you can fit a 4" batch box and riser mostly inside that with a couple inches of water jacket plus air gap. You would probably need to get it welded up professionally to do it right.
 
Keith Coldrain
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Location: British Columbia, Canada
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That's something to consider. Space is very limited inside and any interior modification could effect a tired old structure, (the trailers and mine). I do have a plastic enclosed porch I built using of one of those collapsible gazebos, (about 14' X 7' 6"). And I do use insulated skirting, so leaving the stove outside year round is an option, but it still needs to be semi portable.

I should mention that I do tend to be the type that often does things others have said can't or shouldn't be done. For instance. Everyone I've mentioned my convection propane furnace to and how it needs improvement, has said its as efficient as it can be. I turned up the temp the other day, used my lazer digital thermometer and found that the top of the tank/burner was only 119F then went outside and checked the deflector in front of the exhaust, 312F. That to me seems to be very inefficient and yet another summer time project.

I don't have any barrels at the moment, but I do have the outside metal from an 80 gallon hot water heater and a large tank from a tall compressor that's about barrel with and 6 ft tall. Other materials such as c-channel, angle iron, and a few 20lb and some larger vehicle type propane tanks. My mig welder, assorted other shop tools and generator stay in storage until it warms up.

Keith.
 
Glenn Herbert
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If you have a welder available, you will be able to do a good water heat exchange and storage container which would be totally portable (might want two people to move the tank easier, depends on the size and how thick the metal is). And if you have an enclosure which can shelter the heater in winter next to the trailer, placement becomes infinitely easier - you just need to work out getting the heat inside. A water storage tank with insulation and a circulating radiator coil may work, especially if the tank can be located low enough relative to the trailer floor for gravity circulation.
 
Keith Coldrain
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Location: British Columbia, Canada
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Unfortunately using water outside means more of having to babysit the stove to keep it from freezing and bursting open. A small heat exchanger with ducking either into and from the trailer interior, or from and to the skirted in underside of the trailer would be more likely.

I'm still considering hybrid variations of the 4" rocket heater, but massless ones only. Most rmh's I've seen would need a forklift to move and a tandem axle trailer to haul. Even the more common massless rocket heater variations need a 2 wheeler dolly to move unless disassembled.

Over the next month or two I'll be continuing to research my options for stove design and materials. I'll likely experiment with a narrower vertical (small footprint) system. At present I'm thinking along the lines of a conventional (traditional) style firebox with air and flue dampers, but the later would be directly above the firebox, with a set of baffles above that in a mixing chamber with an insulated chimney above. Of course a preheated air supply included for cleaner burning secondary combustion. By measuring for hot spots in this system I think I can figure out a likely place to extract surplus heat. Some of the entries into last years stove competition seemed to work along similar lines as this.

Keith.

IMG_20150102_121313.JPG
[Thumbnail for IMG_20150102_121313.JPG]
Keith's vertical rocket heater
 
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