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Post by dwayne on Jul 17, 2021 6:59:20 GMT -8
I have built a RMS out of a 33 gallon barrel.
have it all together and have ran it about 8 times.
The output from my chimney is zero smoke, and seems to be extremely efficient.
My problem lies in the amount of heat the heat exchanger is putting out. I am
only getting about 250F on the top of my barrel. My output at about six inches
from the barrel exhaust port is approx 1/2 of the temp of the top of the barrel.
This is a 6 inch system all the way through. When my flame is really roaring
and filling up the burn channel, the top of the barrel will get to about 310F
I read about people getting 500+ easily off the top of their barrel. What do
you suggest the problem is?
It has excellent draft. But little heat. It seems to be very efficient because
the exhaust is 100 percent clear.
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Post by Orange on Jul 17, 2021 11:49:19 GMT -8
6 inch J is not suitable for any space imo, to little power.
what's the distance from top of heat riser to barrel?
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Post by martyn on Jul 17, 2021 12:21:02 GMT -8
How have you built it, what materials did you use and how did you insulate ?
You should be able to get 7-800 f on top of the barrel if you have built it to spec and use nice dry fuel.
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Post by dwayne on Jul 17, 2021 12:53:21 GMT -8
6 inch J is not suitable for any space imo, to little power. what's the distance from top of heat riser to barrel? The distance is approx 5 to 6 inches from the top of the barrel. I read about 4" systems getting 7 to 800 degrees. I read about 6 inches climbing up to 900 and 1000. I would think that the one I made would climb to 500. It is just a standard barrel, using 6 inch 1/2 inch steel square for the combustion chamber. Very little brick insulation for now, gotta get it going and working like it is supposed to before I continue the build. The sides of the barrel are about 1/2 the temp of the top. I was wondering if I have to much space between the sides of the combustion chamber and the walls of the heat exchanger. My guess is around 6 inches. The barrel is a tad over 18 inches, and the combustion chamber is 6 inches, leaving 6 inches. |
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Post by dwayne on Jul 17, 2021 12:57:13 GMT -8
How have you built it, what materials did you use and how did you insulate ? You should be able to get 7-800 f on top of the barrel if you have built it to spec and use nice dry fuel. I had no specs. I used a 33 gallon barrel with a 6 inch square steel combustion chamber about 24 inches tall. Barrel is about 30 inches tall and a tad over 18 inches in diameter. The center combustion chamber is a 6 inch square steel that is 24 inches. |
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Post by martyn on Jul 18, 2021 4:11:01 GMT -8
Ok well I dont think you can expect the same performance as an insulated masonry construction .
You really need to build with tried and tested dimensions to achieve max performance .
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Post by pigbuttons on Jul 18, 2021 5:41:49 GMT -8
How far below the top of riser is your barrel's output port?
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Post by peterberg on Jul 18, 2021 12:12:41 GMT -8
Below are some specs. See for yourself Dwayne, whether or not yours is like it should be.
A proper J-tube do consist of three parts. Feed tube, burn tunnel and heat riser. Feed tube is vertical, the fuel is fed in there. Burn tunnel is horizontal, most of the combustion is happening there. Heat riser is vertical again, some combustion is taking place there but the main function is to provide strong draft. Proportions of this three seen in stream direction: feed:tunnel:riser = 1:2:4, measured in the heart of each part. To clarify: feed is measured from top down to heart of tunnel, tunnel from heart feed to heart riser, riser from heart tunnel to top. This assembly should be the same cross section area throughout.
Your steel J-tube need to be at least according to these proportions, most of the time numbers are dictated by the tunnel length. In order to ask questions about your particular Rocket Mass Heater please use the above terminology so others could understand which of the parts you are referring to.
In order to achieve the high temperatures this design is famous for, it need to be insulated all around the combustion core. That is feed, tunnel and riser. A steel tube won't last long this way, the steel won't melt but due to the high temperatures and oxygen-rich environment the material will corrode very rapidly. Even stainless steel won't survive multiple winters this way. This corrosion is the very reason why the J-tube need to be built out of refractory materials of whatever kind.
The combustion core I like to call the front end, the heat extraction system the back end.
The barrel isn't part of the front end, but part of the back end instead. That last one could consist of a bench with or without a chimney pipe in it and/or a masonry or steel bell of whatever shape. The whole of the thing could be built out of cob, bricks, concrete, sidewalk pavers, any combination, you name it.
Hope this helps.
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Post by dwayne on Jul 20, 2021 7:21:55 GMT -8
Thank you all very much for the replies, and thank you Mod for the info.
Like I say, I am very new to this. I understand the concepts, but I do not
know the language you all speak in. Thus, I will make plenty of mistakes.
I would describe my J as about a 1:1.5:3.5 if I were to describe it.
The feed tube is made of Chimney clay, the burn tunnel is made
of Chimney Clay, the heat riser is made of 1/2inch steel square purchased
from a scrap yard.
I tried, however wrong it was (smile) to keep the burn chamber as short
as possible, so the fire would go through the burn chamber and into
the heat riser. The burn chamber's edge is on the very outside of the
barrel, plus about 1.5 inches for sand as an insulation/air sealer.
Most of the barrel is exposed, because I wanted instant heat, a lot of
it. My exhaust seem to be about right in temp. 100 to about 150 for
the highest temp, and that is approx 8 inches from where the exhaust
pipe enters the barrel. (this is dependent upon how hot the barrel is)
Anything less, I am afraid will not have enough heat for an updraft.
updraft chimney pipe is 2.5 stories tall.
I guess one can say at least the exhaust is invisible, so a complete
burn is taking place.
My goal was to get the rocket stove working first to where Ilike it,
then I was going to add more mass as a bench. But for right now,
that more mass may destroy a lot of my heat rising, yet give me
very little mass heat to begin with.
My guess is, with higher temps around 500 or 900, My exhaust
would run round 250 to 500, giving me a little power to heat up
a mass bench for heat storage.
Like I said before, you are talking to a newbe that understands
the principals of combustion's and how a RMS works, but doesn't
understand the jargon or the science of exact dimensions and
other things that make it efficient.
It may be that I am just expecting way to much out of what I have.
Something that is hard for me to accept, when I read about others
having a much higher temp.. . even for smaller systems.
Dwayne
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Post by peterberg on Jul 21, 2021 6:40:45 GMT -8
Insulate around the riser and see what happens. In case it is doing better, insulate all around the J as the next step.
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Post by dwayne on May 23, 2023 22:27:33 GMT -8
After a year and a half of playing around and experimenting...
I was able to solve the problem....
Unlike the info I got here, the problem was solved not by dimensions and
specific J-RMH dimensions, but was solved by the distance the Combustion chamber was from the top of the barrel.
when i got the combustion chamber about 3 to 4 inches max from the top of the barrel, everything ended up working like it should have.
I calculated the area of the exposed air on the top of the combustion chamber to the top of the barrel and made sure it was at least the area of my flu.
My RMH is now mimicking the G2 liberated RMH. output. on the top, down the sides, and out the flu.
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