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Post by bernardbon on Mar 13, 2013 22:04:37 GMT -8
hi,
craftsmanship. I have a question on the concrete. The temperature difference at each end of each piece is very large. Deformation of the concrete supports this constraint without cracking? How many years the concrete can withstand regular use?
Bernard,
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Post by peterberg on Mar 14, 2013 3:08:35 GMT -8
Temperature difference between ends are less than you would expect. Levels at the bottom of the feed can reach easily 1000 C. (1830 F.). Admittedly, in the experimental model there are some minor cracks after creating a thermal runaway repeatedly. It's still in one piece, nothing to be worry about.
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Post by pinhead on Mar 14, 2013 4:41:37 GMT -8
Hello peterberg. Do you think you could give a solid definition of thermal runaway? I have a feeling I understand what you're talking about but the term could have multiple definitions depending on the situation.
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Post by peterberg on Mar 14, 2013 6:00:56 GMT -8
Do you think you could give a solid definition of thermal runaway? I have a feeling I understand what you're talking about but the term could have multiple definitions depending on the situation. What I would call a thermal runaway for my experimental rocket heater: Letting it run in the highest possible mode, hours on end. The feed tube stuffed with very dry and small fuel, keeping it going in so-called pulse mode. This is a situation where it is geared up to a state which delivers an about 60% higher than normal burn rate. Consuming fuel at a racing pace, outputting oodles of heat. See the Hypothetical stove thread. And here is a diagram of a 3+ hour run like that. All the down-reaching green peaks representing an exceptional low O2 level, even down to 2.5% in one instance. And it's sounding like in this video clip. During such a run the inside of the entire tunnel is glowing red-hot. Keep in mind, this is a mini rocket heater, system size is a mere 4x4".
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Post by smarty on Mar 18, 2013 1:04:39 GMT -8
Hmmm I wonder what the shipping would come to if I ordered the smallest one from the uk? Let me know when you have some available for sale - just the cast core. I might be interested.
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Post by blindpig on Mar 23, 2013 8:26:08 GMT -8
Peter, Have you a temperature measurement at the top of the insulated riser pipe? I'm interested to find out if using a design like yours would allow an insulated chamber above it to melt a crucible of aluminum. Don
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Post by peterberg on Mar 23, 2013 13:02:16 GMT -8
During the development of this core, the temperature at the top of the riser isn't measured. My design of the batch box rocket is, and it could easily produce temperatures ranging from 500 to 900 C. (932 - 1650 F.). My quess: the 6" J-tube core could be capable of about the same.
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Post by volodymyr on Mar 24, 2013 7:03:33 GMT -8
Hi endrunner, what about cleanout in your construction?let me know how you'll get ash out from this gismo,pls? regards
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Post by endrunner on Mar 25, 2013 9:22:55 GMT -8
If you are building a rocket heater and only using the core, then you can put clean outs at the usual locations.
Sometimes there is a bit of ash below the feed tube, from the tails of the prior burn. if you want you can suck out, but there is so little we often don't bother, we just start the next fire.
The full heaters can either remove the barrel, and or door at the back.
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Post by endrunner on Mar 25, 2013 9:27:54 GMT -8
blindpig,
I will try to get you some numbers, but I can tell you that in a test burn of the 6", with a double barrel, where the top of the barrel was over a meter from the top of the heat riser, the temperature of the top the barrel still got to 650F, with the coolest point around 325F at the lower end of the barrel. This is about 6ft of barrel height all radiating that much heat.
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Post by endrunner on Mar 28, 2013 10:13:49 GMT -8
We did a test of the 6" today with only one barrel. I clocked the outside top of the barrel temp about every 5 min. Here were the results. All temps in F
Mins Barrel Temp 5 172 10 362 15 494 20 596 25 683 30 691 40 765 45 930 50 over 1000 - probably 1020 (based on -20 degree reading 60 900 .. 130 950
The bottom of the barrel ranged from 350-412
fuel was dried oak
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Post by Donkey on Mar 28, 2013 11:35:10 GMT -8
Endrunner, Interesting. Last year, canyon and I took a series of readings from a quickie horizontal feed stove that we assembled at Cob Cottage. The stove consisted of his (canyon's) 6 inch horizontal fed kit with a 50 gallon barrel over the heat riser, feeding to a bell, made of a small, 16 gallon drum. We marked rows from top to bottom, spaced around both the the barrel and the bell and from time to time, measured temperatures at the marks. I've got our results somewhere, in an .xls document.. Ok, I found it. The document only shows temperature readings from our 16 gallon bell. I'll need to look deeper for the readings off of the primary barrel too. My feeling is that we don't have enough data to point to anything, though I think the patterns shown on the skin of the bell point to patterns of flow within the stove. This could be an interesting avenue for more study. The file is here if anyone is interested.
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Post by sneekypete on Apr 3, 2013 18:29:41 GMT -8
Hello I had posted a question some where else on the forum about a RMH build I was attempting to replace a wood stove in the corner of a large room I only have a minimal amount of Thermal mass area possible and this RMH would have to occupy an area of a 5' x 5' 7" in the corner of a room where the wood stove used to be, I was going to put the feed tube burn tunnel and hand built square barrel in the center of the 5' x 5' 7" area and wrap the piping covered with mass around it or kind of circling it and ending the piping in the back behind the barrel where it originally came out and then straight up the chimney The whole thing would still be within the space my old wood stove took up and it would use my original 6in chimney I’m needing the temperature output of the square barrel section of this RMH to come close to the temps the original wood stove it would be replacing was capable of to give me the instant heat I need The mass would be an added bonus Too bad there couldn’t be more but space an issue
I see from the above data that you easily achieve the temperatures I would need to replace my old inefficient stove but you fail to mention what size barrel and internal dimensions utilizing the dragon core I’m wondering if all the usual rules apply in spacing of the barrel from the top of the heat riser and if in your data collection you in any way insulated your heat riser or didn’t need to due to its material How tall is the dragon heaters heat riser? What is the spacing to the top of the barrel and also the spacing down the sides? My question really is how to utilize this core to its fullest with the components around it I know I'm asking a lot of questions I just want to get close to right the first time in my build I’m thinking that using the Dragon core and riser will get me closer to the temps the old wood stove did for immediate heat with the added bonus of the mass surrounding it It sounds like just the ticket for my project Thanks
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Post by endrunner on Apr 4, 2013 5:59:54 GMT -8
The above numbers were using a 6" burner and 30 gallon barrel. We tested the same burner with a 55 gallon barrel. To my mind this was better because the max temps were 600- 700F. Which I think is a safer level to operate at. The difference is the amount surface area the heat is being distributed over. The heat riser is 30". From my testing of the various sizes, the normal rules for rocket heaters don't apply exactly. They all seem to need the next size up for barrels. In other words the 4" runs better at at 30 gallon barrel and the 6" with a 55 gallon barrel and the 8" probably will need 2 55 gallon barrels, to avoid the crazy barrel temps a full bore. I have a testo 330 and a temperature data logger with 8 temps I will be using to provide a more detailed profile. We will also be testing a design like the link here, that uses a double bell. The area to the right of the burner is a large firebrick lined bell and the 2nd bell is under the burner. The barrel exhaust scrapes past an oven, but the oven thing could be eliminated. it has a 3x3 foot print. www.dragonheaters.com/wood-fired-stove-oven-and-masonry-heater/
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Post by matthewwalker on Apr 4, 2013 9:36:54 GMT -8
The website looks great Sandy. Congrats on getting it up. That is a really nice looking heater.
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