Yes, this is similar to what I was thinking to have an extra bell that can accumulate the extra heat but in order not to affect the draft directly I would extract the heat via a heat exchanger that does not communicate with the inner flues/bell
I don't have a barell it is a bell type. The firebox and the riser is enclosed inside this bell which is basicall a little room constructed of brick and firebrick. That space above the riser of about 30cm toghether with the rest of the space provides room for some gas separation (so that the hotter air gets a chance to rise and stay while the cooler gases drop and exit. The first combustion occurs in the firebox and continues to burn in the riser (which is insulated) What ou see there to the left is the chimney the exterior wall made of brick, the inside round 200mm refractory sleeves. You have mentioned the barell type of heater. In a classic rocket barrell design with a bench another principle is used and is very different from the bell design because there are flues where hot and colder gases exit somewhat toghether because they are pushed or pulled out through the flue. If the barrel is right above the riser the space is narrow and the gases expand and push out. Some heat is retained on the way out in the mass and is slowly released to the room through radiation. There is no heat produced there through friction. Just wood combustion.
Still, I have a question: I was thinking that the post combustion of the fumes happened when theyr are pushed down in the barell because of the friction. Am I wrong?
It seem's to me that you don't have any barell (may be I'm wrong too and it's not on the pictures), so wheres does this combustion happened?
You have a chimney on the left, did it play any kind of heat extraction, or is it just a xay for the fumes to get out?
Best regards from France.
No. All combustion happens inside the insulated portion of the stove - BEFORE the barrel. Any combustion post-riser is "leftover" and represents either insufficient insulation in the core of the stove, or too much excess air; the barrel cools the gasses more than is optimal for combustion. While there will some times be flames "licking" out of the riser, these flame are at an extremely reduced intensity and are only during the absolute hottest portion of the burn.
After Westcan_xye proposed the idea of adding a fan to help draw more heat from the system before exit… and a few of us shot the idea down… I couldn't help but wonder how well that might work. Then a friend of mine was looking for a way to transfer heat from a potential masonry heater in a garage through a crawlspace under the main house… so i got to wondering if the fan at the end of al long duct buried in thin cob would somehow work.
Recently i have been drying out a 35' x 17' x 3' deep earthen battery with 6" CSA J-feed rocket, so i opted to lengthen the flue run to to about 60' all told, and put an axial fan on the end of it.
The result? Doesn't work. Although the fire looked happy in the J tube, it blew a steady blue out the exhaust. Assuming it was a matter of the fan pulling too fast, i slowed the CFM rate gradually looking for the sweet spot. But there isn't one because the push of the fire itself is always changing. Furthermore, whenever the pull from the fan even slightly exceeds the push from the fire the gasses do not mix well in the elbow. I have put small chunks of wood at the far end of the burn tunnel and the do not combust. All this tells me that the efficiency of the J-feed rocket is very much dependent on having little or no negative pressure downstream from the heat riser. And that factor is constantly changing depending on the rate/intensity/amplitude at which the fire is burning
Glad i tested it before trying it in a permanent build.
Last Edit: Feb 22, 2016 20:21:57 GMT -8 by patamos
Seems the draw of the chimney is always coupled to the push of the fire up the heat riser. I'm guessing that the pushing pressure via gas expansion in the combustion chamber also creates a bit of back pressure… enough to keep the volatiles mixing where we want them to.
Perhaps this is why pellet stoves have carefully metered fuel delivery rates
I would have thought every J tube connected to a chimney would have negative pressure. How is the pull of the fan different to the draw of a chimney?
When the stove is cold and you've got too much ISA, then your flu gas will reach 100% humidity and start condensing and after a bit you've got fog forming in your chimney. Enough fog and you chimney isn't full of lighter than outside-air gas, it's full of heavier than outside-air gas.
Option 1 is allow lots of room air up the chimney (bypassing the fire), so that the fog is diluted and swept up the chimney. Option 2 is heat up the chimney so that there's less condensing and the fog is warmer and it's still lighter than the outside air. Option 3 is do nothing, and hope that the back pressure doesn't stall your heat-riser, dull your fire and then (as the heat riser temp. drops, dump the whole chimney full of fog into your living room, gassing all occupants. By this time, of course, your CO detector will be screaming blue murder. At least, mine was. You do have a CO detector, I hope.
If you have a functioning fan, then it would overcome gravity, but I really wouldn't like a solution that was designed to permanently have a chimney full of heavier-than-air gas, just waiting to gas the family in the event of a power-cut.
Just wanted to say Thanks for this thread. I have been reading this board for the past few months in prep for a first time build. The progression of the designs since the beginning has been great to watch/read
TexasGonzo: Sooooo glad I found this site! Its always rewarding to find such a super group of folks! To any and all, feel free to PM me anytime. Thanks for having me!
Mar 11, 2019 18:56:41 GMT -8
jlmtech: GADGET: CONSIDER USING A JET PUMP INSTEAD OF A BLOWER FAN TO INDUCE DRAFT; NO CLOGGING.
Mar 26, 2019 8:19:28 GMT -8
michaelegan: i am unable to open the sketchup files on my mac. I used sketchup a few years back but apparently the company now requires a subscription. does anyone have any advice/instructions on how to use the program or how to view pictures without spending money?
Aug 20, 2019 18:41:48 GMT -8
mannytheseacow: michaelegan: download AutoCAD student version for free... import .SKP
Aug 23, 2019 13:33:44 GMT -8
topbaza: hi everyone, been searching all over net and this is were i need to be i think!!
Sept 28, 2019 6:16:25 GMT -8
anounaki: Hi, why I cant upload photos when I make new tread to this forum?
Feb 28, 2020 2:09:40 GMT -8
ahansen: photos under 1 mb not possible?
Jun 4, 2020 0:09:21 GMT -8
belgiangulch: Photo's are possible. They must be downloaded elsewhere and the image url (adress) is copyied.
Sept 14, 2020 7:26:15 GMT -8
belgiangulch: While creating a thread click on the small picture in the banner above the reply. A box pops up, paste the image url in the box. Pay no attention to the huge list of numbers and such.When you finish and hit reply your post with pictures will come up.
Sept 14, 2020 7:29:27 GMT -8
deadstarsstillburn: Hi there. I was directed this way by folks on the Permies.com website and am hoping I can get some information on how a total newbie can get started designing, siting, building, and not-dying-in-a-horrible-house-fire with a new RMH in a 160-year old home
Oct 21, 2020 6:52:10 GMT -8
deadstarsstillburn: The people over there recommended either a 6" batchbox or an 8" J-tube. I don't know what those are but am going to try to figure that out. What I need is a blueprint that I can scale to fit the need for my house. I have something likne 5000 square feet
Oct 21, 2020 6:53:00 GMT -8
deadstarsstillburn: but I do not need to heat all of it by any means. probably only need to heat half of that, maybe less.
Oct 21, 2020 6:53:15 GMT -8
deadstarsstillburn: moreover, the house has 3 storeys (large attic) so I assume if I get very efficient heating on the ground floor, that will go a long way toward heating the upstairs as well, no?
Oct 21, 2020 6:53:59 GMT -8
BenAlexanderT: Happy new year everybody. I wish you the best
Dec 31, 2020 15:06:14 GMT -8
Solomon: Anybody in Southern Oregon, in Jackson or Josephine counties?
Jan 16, 2021 21:54:43 GMT -8
gnomedome: i realsie this is from 2009
Apr 14, 2021 8:30:44 GMT -8
gnomedome: i realize this is from 2009 id love to see the photos from this ..as im looking to build a sauna soon similar to this .... if anyody sees this post firstname.lastname@example.org..... the photos in this post did not show up
Apr 14, 2021 8:32:00 GMT -8