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Post by leland on Jan 25, 2018 4:58:21 GMT -8
Greetings folks,Please, I am writing to ask your opinion on the following concept:
I am about to hire a local company to create a soapstone bell. A bell to store some of the heat from the gases leaving our cookstove. The cookstove currently sends exhaust up a 24 foot insulated chimney.
The bell I wish to have made has two 7" (entry/exit) holes close to the base. The bell is made of 1.25 inch thick soapstone. It is 5.5 feet high and 16 inches square.
Even though you are lacking some details, do you feel I am in the right ballpark? To absorb at least some of that lost heat up the chimney?
Thank you so much! Leland
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Post by matthewwalker on Jan 25, 2018 16:16:57 GMT -8
My opinion is that it is a bad idea to attach a bell to an inefficient burner like you have there. You will fill the bell with creosote and often smoke, creating a dangerous condition where the smoke can ignite and blow the bell apart, or a chimney fire. I'd suggest a cleaner cook stove if you want a mass heater.
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Post by leland on Jan 26, 2018 3:31:11 GMT -8
Thank you so much. I appreciate your concern. You mention looking for a cleaner cook stove - have you used our model before? Is there something you know about our cookstove that suggests it is a less clean burn that others? The wood we burn is well seasoned and we burn it hot. The chimney flue is very long and remains clean upon every inspection. We would only send our exhaust to the bell after the fire was mature - not at the start. If I were using a non-airtight, smoldering cookstove, I could see an issue. This is an amish-made airtight workhorse. A very different creature than most old fashioned cook stoves. Thank you again for your reply. I appreciate it. Do you see our cook stove in a different light now? One more appropriate for a mass heater?
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Post by matthewwalker on Jan 26, 2018 6:18:27 GMT -8
My opinion is that any cook stove of a design like yours is far from clean or efficient, the firebox designs are just not designed well for clean combustion. We are operating in a whole different range of cleanliness and efficiency here, and the traditional designs are extremely poor burners in comparison. I wouldn't recommend running it into a bell.
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manU
New Member
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Post by manU on Apr 6, 2018 15:40:23 GMT -8
Hello leland. I'am courious about your stove because you described it as different from old cookstoves and well made. I would appreciate if you would like to share some more details about it, specially fire box characteristics.
I do think you are in the right path trying to store lost heat in mass. Have you tried your bell yet?
Cheers
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Post by drooster on Apr 7, 2018 9:43:00 GMT -8
I'm sure the guy with the disturbing cornflake-box avatar did not re-enter his thread ...
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manU
New Member
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Post by manU on Apr 10, 2018 16:38:55 GMT -8
Maybe he will be back... Anyway, a frequent question around here is "can I just add a mass bench or else to my current metal box stove or a metal cookstove?" Another question would be: what would be a simple, effective, safe way of extracting more heat of that kind of metal stoves? I think MatthewW already made the most important point to consider. Also I believe some designs may rely on hotter exit temps to work properly. What else to consider? Any threads already about this?
So about Leland's stove, is interesting he mentions the chimney stays clean. So I think either his stove really is burning somehow clean, or my guess is it remains clean because small chimney fires happen often when burning it hot, keeping it clean. Any thoughts?
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Deleted
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Post by Deleted on Apr 11, 2018 1:42:52 GMT -8
Hi manU We tried to add mass to a "normal" cast iron stove and it was a big big failure -- impossible to get the thing NOT to smoke and to EMIT heat ! At the end of two days of testings, there were 5 mm of tar inside the bell.. I think those heaters rely heavily on a strong draft created by high chimney temperatures. If you add mass you will necessarily create more resistance to the flow of gaz and you will have an even worst combustion. Details here : uzume-asso.org/session_batch_2018.html#turbomasseEduardo Marquina tried something also : estufasdeinercia.wordpress.com/2017/01/26/mejora-de-miniestufa/He told me it worked but he had to insulate completely the heater from the inside and he made a very simple bell creating little resistance to the flow of gases. Regards,
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Post by Vortex on Apr 11, 2018 2:34:34 GMT -8
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Post by DCish on Apr 30, 2018 17:02:35 GMT -8
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manU
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Post by manU on May 1, 2018 5:20:13 GMT -8
Thanks for the links. Very intersting projects. One thought I had about converting metal box stoves: maybe the first meter or so of vertical exhaust pipe should be converted into a heat riser like feature. That way it may help with both improving combustion conditions and helping with draft to compensate for lower exit temps.
Example: metal firebox lined with cob and refractory splits, exit of metal box into heat riser is port area, then 1m of insulated heat riser going up, then 180 degree turn and 1m of pipe going down into a bench.
Similar to DCish setup in a way...
Any thoughts? Cheers
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Post by fiedia on Aug 15, 2018 23:48:08 GMT -8
Leland, I built such a bell for testing purpose : A brick bell prototype to improves standard stove efficiencyRead the conclusion to get some ideas about pros & cons. Results are very good regarding heat transfer and wood burning, but it stinks really strong. I will open it in one month and I guess it will be quite full of tar. So I would be very cautious using such bells on long term basis. First my bell was too big and exhaust temp too low (it captured too much heat). the next bell will be smaller. Second it was single skin and therefore untight. the next one will have two skins. Regarding creosote, I am afraid that matthew is right. My flue is quite clean without bell but with the bell and therefore low exhaust temperature, I have to clean it more often. All flamable particules which are usually burnt during a strong fire, accumulate at the bell exhaust. It will be better with your stove but I would definitely use a smaller bell with two skins and add a door for cleaning.
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Post by pinhead on Sept 6, 2018 12:32:11 GMT -8
I echo matthewwalker's sentiments; I'd be less worried about the bell and chimney getting dirty than I would about the thing exploding.
I had an early test stove literally explode (sending the barrel careening into the ceiling) when the draft was strong enough for flame to reach the smoke-filled bell.
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