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Post by byronc on Nov 15, 2015 5:42:18 GMT -8
Vacuum forming a rigidized CFB (Ceramic Fiber Blanket) heat riser tube has obvious advantages. I would think the main one being that of eliminating trapped air pockets that would otherwise destructively "popcorn" under high heat conditions. For my one-off 6" batch I'll probably go with a hexagon shaped riser made of IFB. Those are easy to cut and shape with hand tools.
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morticcio
Full Member
"The problem with internet quotes is that you can't always depend on their accuracy" - Aristotle
Posts: 371
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Post by morticcio on Nov 15, 2015 9:33:14 GMT -8
No problem Peter. From the photos on Jouls' website the riser looks like the wall is about 30mm thick (approx. 210mm outside diameter).
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Post by heatengine22 on Nov 18, 2015 11:28:19 GMT -8
Peter,
Can the Peterberg batch box be taller so that one can load more wood per batch? The taller wood batch would burn down losing height over time and would then be similar to the original design.
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Post by peterberg on Nov 18, 2015 11:47:11 GMT -8
Think of the firebox as it were a tunnel. The back end being the most important, because of the port and how it is situated and sized. So the height and the width in the design is quite tight. However, a tunnel can be made longer, i.e. a deeper firebox. I tried it once, lengthened the firebox by 50% and it still burned clean. The burn happened to be much more violent though. So I reckon making it deeper by 30% would be just good enough. Lighting it would be a bit more inconvenient because of the necessity to lit it in front of the port.
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Post by daniel on Nov 18, 2015 15:01:33 GMT -8
Peter, what is a good way to start the fire in a batch box, as far as arranging the wood etc?
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Post by peterberg on Nov 19, 2015 1:11:27 GMT -8
The best way, i.e. what the Testo recorded, is to make a small fire just in front of the port. When that's catching on, add two or three medium-sized pieces. When that's burning healthy add the rest on top of it. There are also indications that cramming the firebox very full isn't yielding a good burn. So a distance of about 5 cm is recommended to leave between the fuel and the ceiling. Leave also that same distance between the fuel and the main air inlet. No piece of fuel sticking into the port and no burning piece directly against the main inlet.
I tried everything I could think of, bottom lit, several top lit methods and side lit methods as well. The above turned out to be the best, with lowest CO numbers.
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Post by heatengine22 on Nov 24, 2015 10:47:09 GMT -8
Peter,
Continuing with the idea of a taller batch box. My goal is to sustain a longer burn per batch and thus generate more heat. What if I was to put in a series of holes in the upper portion of this taller batch box to allow in more oxygen. As the taller load of wood burned down below each air hole, the holes at that level would be re-sealed restricting oxygen to the batch box. Eventually, all the additional holes (at each level) would be sealed except for the original hole in the back of the box.
Would this work or would this idea create more pollution?
I think if it worked the box would become hotter because more fuel would burn in the box.
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Post by peterberg on Nov 24, 2015 12:49:43 GMT -8
Honestly, I can't see why it would work. As it is now, it proves to be quite difficult to use more than half of the oxygen which is allowed into the box. Allowing more would mean all the excess air will heat up and sent up the chimney. One way to yield more heat (from the same amount of fuel) is to lower the temperature of the gases which are going into the chimney. The other method is to try to create a "lean burn", using as little air as possible. This is much harder to achieve but at the same time it's also much more profitable. My own batch box bell heater, which is new and I am still busy to find out the best method to operate it, is capable of achieving 95% efficiency according to my Testo analizer. That figure isn't just a moment in the burn but average instead, taken from the whole run from begin to end.
Why you want a longer burn escapes me, the thing will generate an awful lot of heat in a relatively short time frame. This combustion core is ideal for larger mass heater configurations. Short, violent bursts of intense heat will be sufficient to charge the mass. Whether this bursts will last for one hour or two isn't really relevant.
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Post by satamax on Nov 24, 2015 13:25:46 GMT -8
Peter, i might be mistaken, but to me a lean burn is excess oxygen. And a rich burn, excess fuel. Adiabatic being the perfect mix. Daft me Stochiometric, not adiabatic. en.wikipedia.org/wiki/Air-fuel_ratio
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Post by heatengine22 on Nov 24, 2015 17:21:17 GMT -8
My way of thinking is that the batch box is limited by the initial load of fuel at the start of the burn. Once the fuel in the box burns a new load of fuel would have to be placed in the box. If I was using a rocket mass heater to provide heat to a ceramic kiln, for example, then I would have additional firebricks that would need heating and I would have to sustain the heat to the kiln over a longer period of time.
If a batch box could be loaded vertically with fuel then gravity would be available to pull the fuel to the base of the burn box. This would act as a continuous feed batch box rocket mass heater.
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Post by peterberg on Nov 25, 2015 3:17:38 GMT -8
Max, you are right, what I meant was a burn with as little excess air as possible.
Heatengine22, the batch box can be fed semi-contniously in the sense that every 20 to 40 minutes fuel can be added. It isn't possible to use it as a J-tube rocket, so all of the batch will be on fire rather quickly.
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eng
New Member
Posts: 18
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Post by eng on Nov 29, 2015 0:29:51 GMT -8
I think I have put this i the wrong place. Satmax I was referring to your range adaption. My apologies for the C.U. Thank you for giving me ideas for converting my Rayburn Stove. Your series of photos were excellent.
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Post by daniel on Nov 30, 2015 2:36:38 GMT -8
Heatengine22, to this idea if you put the box vertically it could become a downdraft with modifications to the port which will prevent wood falling into the secondary burn chamber. I was thinking of trying that.
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Post by satamax on Nov 30, 2015 10:55:33 GMT -8
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Post by oxbowfarm on Dec 3, 2015 12:18:39 GMT -8
How much wiggle room is there in the port depth dimension? In the reference thread for batch box dimensions, the port depth is 2 inches for all CSA. If I'm building my port with bricks, which I'm planning on, the port is going to be .5 to 1 inch deeper than that. I'd prefer to use the bricks as is if possible unless it will degrade performance significantly.
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