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Post by patamos on Mar 6, 2014 9:50:29 GMT -8
Thanks guys,
Ya i was surprised at how quickly it took off when still wet. This was probably doe to the extensive vertical flue run above, but also maybe indicates that i have some heat to spare. We'll see once i get back there and things are dried out. Maybe a small bell on the upstairs floor. The clients are super jazzed. Their first experience of hanging out on a conductive heat source
I placed the window where the feed tunnel transitions to the burn tunnel. Lined it with ceramic felt and insulated cob on the outside.
The heat riser i cast using cardboard sona tubes. And a castable high temp refractory mix from a company called clayburn. My first cast i discovered that the material wanted to set up super quick. So i did another one in stages. 6.5" ID, 3/4" thick. 28" tall.
Many thanks to you guys and everyone else who offered input. Having this kind of open source support community is so valuable:)
well being
pat
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Post by patamos on Mar 5, 2014 21:46:43 GMT -8
Alright folks, After 6 days in a very cold house i brought it very near completion. After 10 minutes of cranky wet start up it took off like a 'rocket' The bypass damper works great. Everything doing what it ought to. I had to depart before it all had a chance to fully dry out - not to mention the whole 1600' of house with many a wet brown-coated wall... The crux of the biscuit, and the crux of this thread's title was how to stabilize the downdraft chamber. As you can see in the photos it was a bit of a patchwork quilt. I opted to mortar the brick pieces together with a silica sand-clay, as furnace cement just didn't seem to fare as well with all the moisture coming and going as i went about drying segments with a propane flame weeder torch. Outside of those joints i laid a skin of 3/4"+ of cob plaster with fine chopped straw. Dried the cob a fair bit to shrink it down. then bedded strips of 2" x 2' fiberglass mesh in thin layers of mortar, taking care to overlap and wrap in various directions. So far it seems to be holding up well. I opted to oversize the feed, burn and HR dimensions to 6.5"x6.5" CSA. The downdraft and first 4' of primary flue are roughly double that. after which it all goes where i was hoping it would, including readily up the 6" CSA flue. Whew. more of the stories in the photobucket pics. apologies for the double images. couldn't figure out how to delete them... (sigh, yes i am a luddite) s895.photobucket.com/user/patamos/library/?sort=3&page=1
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Post by patamos on Mar 3, 2014 8:47:47 GMT -8
I've been thinking along the lines of adobe bells too. Perhaps embedding soaker hose in the cobb/adobe and having some kind of moisture sensor/control to keep the material from wetting out.
Regarding reheating the exhaust for the sake of draft, having a bypass flue near the initial downdraft could make that work. I've just completed one with the damper installed into the galvy T, and there are enough holes in and around the damper to keep letting a bit of warm exhaust through. Changing the angle at which it meets the downdraft flow can adjust the effect. These bypass flues also resolve many (if not all?) of the cold start issues, which means the system can be tweaked for maximal heat harvesting when warmed up.
With all this wondering we are doing, i am still curious to know how true is the initial assumption that 'the fine particles are bound to the exhaust gas stream'? Running a comparison between 3 RMHs with identical fire chambers and downdraft arrangements, but one with no mass harvesting, one with metal flue runs in mass, and one with adobe flue runs in mass... could tell us a fair bit
well being
pat
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Post by patamos on Feb 17, 2014 10:26:57 GMT -8
Hey gang. Thanks Trance. Nice smiley Robert I've yet to get back over to finish it. Thought i'd be there by now but got wrangled in to helping a friend wrap up a big(ger than she thought iit'd be) finish plaster of a house. That and emergency repair of my neighbour's septic system... And 10 million other things... I am heading back to finish it in a few days and am beginning to think seriously of how best to create the double skin for the downdraft chamber. ONce the gasses go from the heat riser to bottom griddle deck i want to send them all to one side and down. Planning to surround the heat riser in ceramic wool and then 3" of clay perlite held in by a brick perimeter that will also support the griddle deck. On the downdraft chamber i am thinking of cobb on the surface closest to the heat riser and bricks for the outer side. Then 1/4" of ceramic felt, then 1" of cobb, then 1/2" fiberglass mesh, then another 1/2" of cobb. I think i have a good sense of where things will want to expand and contract... and how this approach will keep the outer skin tight. But i am less sure about how the inner skin of brick build up will fare over the long term. One question is whether to set them tight with furnace cement or with a bit thicker clay sand mortar??? ideas are most welcome thanks for following this post pat
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Post by patamos on Jan 31, 2014 23:35:07 GMT -8
Thanks Kari, That is very helpful information. Sounds like there is some potential to this non-fired clay material
Yes i have often heard of clay's amazing capacity to absorb and release water - some varieties can hold up to 30x their own weight before wetting out... So, although unfired, it could keep stable enough with additions of vapour/mist/w.h.y.
I am thinking now of a mass heater i helped build in which all the flues beyond the fire box were home-made unfired adobe brick. I wonder if something like that (and so many of the old mass heaters through out the world..) would register lower fine particle emissions than similar designs with buried metal flue runs... The owner lives nearby, so i could always go do a test.
Bell chambers lined with a 1/2" of cobb plaster might be an even better set up. And/but if elevated temperatures are a deterrent to potentially beneficial intermolecular forces, then perhaps an unfired flue liner or small bell nearer the exhaust exit would be more effective
??
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Post by patamos on Jan 30, 2014 14:32:29 GMT -8
Hi Y'all,
Peter, I am a little confused about carving the brick to create the trip wire. Is the centre of the brick (with the arrow tip towards the burn chamber) the part to grind/carve to 5mm depth? Or is this central pointy surface what i want to be hanging down more - which means i am to carve the sides of the brick around it?
Any help is much appreciated
thanks
pat
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Post by patamos on Jan 30, 2014 14:24:04 GMT -8
Hey Folks,
Well, looks like pushing exhaust gas down into water is not plausible, even spread out across a radiator. Just not enough pressure, as other's have alluded. My theory that expanding the surface area interface between gas and liquid is probably whacked. Turning the rad over and submerging it just below surface to get the gasses to bubble up might work once the gasses are pumping... But there would be all kinds technicalities in stabilizing that kind of set up.
Another thought: Much natural building literature talks about the slight electro-static charge evoked by unfired clay as it is dehydrating. They say having unfired clay surfaces within a dwelling helps the indoor quality by causing the tiny air-bourne dust and mould particles to clump together and fall to the ground. Although we are dealing with moving air... what about an unfired clay brick chimney with an inside surface that is purposefully dampened?
Could enough electro-static charge be evoked to at least get the unwanted 2.5 micron and smaller particles to clump together before exiting the stack?
I may be wallowing a little too far down the rabbit hole in this one...
p
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Post by patamos on Jan 29, 2014 10:32:34 GMT -8
Further thoughts..
The manner in which air is drawn into the body (pull created by musculo-skeletal activity on a pleural vapour barrier) is part of the picture. Dividing the larger passageways into smaller ones (bronchi into bronchioles) creates a higher ratio of surface area to volume. Then a gas-liquid (air-blood) perfusion occurs across a semi-permeable membrane. The basic layout of mammalian physiology offers a design template. Kind of like a perforated automobile radiator - except the direction of thermal transfer is reversed. You wouldn't want to get too small with the tubules, but somewhere in the pressure-volume-surface area-perforation equation i imagine the transfer of pressurized flue gas into and through near-surface water could be made to work.
Perhaps poking many tiny holds on one surface of a prebuilt heat exchanger, plumbing it up to the exhaust flue just above the heat riser and setting on the surface of a shallow pool.... would tell us something
p
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Post by patamos on Jan 29, 2014 9:08:35 GMT -8
Ho Y'all
To clarify for Ronyon, the 6" downdraft pipe was mostly submerged at about a 45 angle with only 1.5" open above water line. My sense was that the small amount of combustion i had going in that size of a system was not using up the available space in the riser and downdraft tube.
On further reflection, some or much of the steam i was noticing was probably coming from the slightly damp cedar i was burning.
I agree with Pinhead about full submersion not working. Next to earth, water is the densest material in our world, so pushing through it takes tremendous force. When inhaling through a water bong one is applying the powerful contraction of the body's diaphragm and/or intercostal (between rib) muscles to a very small aperture (bong tube). Inhalation via expansion of the ribcage expansion alone generates tremendous heat - as the yogis on frozen lakes in Kashmir demonstrate when they dry out blankets dipped in the icy water with their nasarga bhastrika breathing technique... This much to say, the energy that goes into creating such air pressure differentials is considerable...
There could be ways to tweak the flue to water interface for slight sub-surface bubble action. I'll experiment with that soon for curiosity's sake. I'm imagining a sort of corrosion resistant manifold with many perforated tubes that sit/floats on the water surface... with perforations facing down into the water and gasses bubbling out from there.
Curious also to see what Matt and others discover with TEG draft enhancements...
Sending gasses through air misting sounds interesting. The condensation from that would offer some phase change heat. Perhaps a TEG could power a small pump that returns the condensed water back up into the flue gasses for more misting. If this does catch the small particles it is intended to, then some soft of inline fluid filter pre or post pump might work... If this kind of thing flies, then the whole interface between fire and water heating could take a quantum leap...
thoughts for now
well being
pat
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Post by patamos on Jan 27, 2014 22:39:52 GMT -8
I wonder how these temps would compare - all other things being equal - to vortex's (semi?) widening sloping riser? Might the gasses be happier if they have more freedom to expand sooner across the sloped surface? A J-feed or batch box with 12" of vertical riser then widening to 12" across by 6" deep at 45 degrees slope?
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Post by patamos on Jan 27, 2014 22:18:03 GMT -8
Okay, built up a makeshift 6" L-feed with 4' of fairly well insulated 1/4" steel riser. 2 galvy swivel elbows and another 5' of 6" galvy pipe towards the ground at 60 degrees or so. Not the most powerful set up, but drafted well enough on its own with medium orange flamage in the core. When i placed the end of the downdraft tube in a tote full of water, it did fine til i tried to submerge the last 1.5" of pipe. Then it started back drafting out the feed tube. Tried it a few times, same result... Of particular interest was that the draft didn't depreciate noticeably between 0% and 80% submersion. Perhaps this is because the system CSA had volume to spare for the amount of fire it was running, and a little venturi acceleration at the end was not a problem. And/or, the water being very cold, could have amplified the cooling/contraction of the exhaust gasses. Not surprisingly, a great deal of steam was added to the exhaust upon final exit... Which gets me to thinking about phase change heat generation and yet another phase change if one were to add a condenser set up. All of which would make for considerable complexity (As an aside, re phase change, check out Central Rocky Mtn Permaculture Institute's greenhouse heating if you haven't already) So a low powered system does not exert the PSI necessary to push through the density of near-surface water. Perhaps a batch box with a tall riser and much less of a downdraft run before contacting the water would. As i do not have that set up handy i'd best hand it off to the next curious explorer who does... And from there, how does one go about measuring micron sized emissions? well being pat
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Post by patamos on Jan 25, 2014 23:01:08 GMT -8
Oh this is something. As i was catching up on the last few posts here my mind was drifting over to the way ceramic filters take micron size impurities out of water. Then drifted into imagining some sort of... well... water bong. Morphic resonance or what. How about a giant bell-aquarium ?!?!? With mind bending bubble action nothing like water for heat absorption/distribution... get the fire cranking up a bypass flue then o'er she goes . thip thip for sure. we might have to reinvent the bell shape and ISA equations. but man that will be fun to figure out. A rocket core, a couple of elbows, a length of pipe and a bucket of water ought to tell us something. I'm busy tomorrow, but monday...? Maybe sink the flue well down into a deeper pool but with many small holes in the side walls of the submerged flue to expand its exit CSA(?) If straight down into the water filter seems too thick then maybe the flue can become wide and horizontal just below the water surface level to reduce the back pressure... in a wider shallower pool. And if not through the medium then what about tight across its surface in contained path... or through a looser fabric that sweats water ala pressurized irrigation tubing.... does anyone know how many kilojoules are used in the average human's bong inhalation? getting batty... just throwing things out there...
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Post by patamos on Jan 24, 2014 22:34:38 GMT -8
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Post by patamos on Jan 24, 2014 21:59:53 GMT -8
Seems one of the keys is going back through the assumptions behind the statements that Matt was told: That 'once these particles enter the gas stream they aren't coming out'. Is that information based on an assumption that everyone is running their exhaust hot and straight up a vertical flue? If so, then velocity is a contributing factor and the low velocity of large horizontal bell ceilings are involving a whole different dynamic. In this case passive mechanical filtration ala pinhead's last post might hold some promise.
If the suspension of micro sized particles is more a matter of sub-atomic repulsion/attraction... then electro-magnetic solutions may be the ticket. In either case, i wonder what effect different kinds of filter material may have. Eg. is there a readily available material out there that particularly attracts and binds the suspended particles?
well being pat
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Post by patamos on Jan 24, 2014 20:35:18 GMT -8
Thanks Trance and Donkey, It may be the luddite in me, but when i go to remove one of the double images in certain posts they both disappear. I'll putter a bit more and then get into this photobucket thing soon anyway. For now i have two boys (monkeys i'd say) climbing all over me well being pat
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