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Post by peterberg on Oct 14, 2015 16:52:53 GMT -8
Sounds very interesting Peter, what is the system size of this latest creation? I like the idea of getting the batch box up off the floor to save one's back, and have been thinking of building a tall narrow "wall" Russian style heater with a batch fire box. What is the outside dimensions of your bell, and is it single wall or double wall brick or barrel(s)? This is a 6" system. The outside dimensions are 98 cm square and 210 cm high. No barrels, no bricks. The whole thing is double wall castable refractory stacked in a building system. Pictures and results in December I would reckon.
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Post by patamos on Oct 15, 2015 8:20:12 GMT -8
I have a question whether this would work: if the riser will go into a larger collection area then split down in 4 tubes of system CSA and then collect into a large area where they could exit to the chimney. The top portion should act as a bell for stratification, the tubes give a 5 sq meter of release surface? Daniel, with this kind of manifold you might face the issue of flue gasses preferring just one or two of the tubes rather than spreading out in to all four before reconvening. Gasses, like water, will tend to take the path of least resistance as they head towards the exit. Benoit (pyrophile) posted some articles about these forces earlier this year.
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Post by daniel on Oct 15, 2015 8:43:05 GMT -8
Thanks, I thought this could happen and was trying to find a way to make them spread evenly in these tubes, I did some small scale test with smoke to see how it flows. Maybe stacking them in a cascade way will make like an inverted cascade of gases flow from the higher dead end tubes to the nex dead end tubes a little lower and forward toward the exit, they should follow this path
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Post by westcan_yxe on Nov 2, 2015 21:06:27 GMT -8
I've seen in this thread concerns over being careful to not extract so much heat that one cools the gasses to the point where the system won't draft properly, and of course it seems that many RMH users have to put some care into lighting a cold heater and preventing downdrafts in stoves that aren't being closely supervised. I've searched the entire forum and can't find anyone using variable speed inline duct fans in the chimney. These are cheap, easy to wire, and are built to handle temperatures that one might see at the end of a flue or stack in a system with abundant heat extraction. Ianto describes his system as having temps around 150F in the stack. A conventional forced air furnace would be generating temperatures in that range, which is why I suspect an inline duct fan would work great in a RMH system. Zero effort would be required to light the thing, zero chance of downdraft, and an opportunity to wring every single last BTU of heat out of the gasses, and a variable speed switch allows for tweaking of the gas flow rates. It seems like it would solve so many problems in so many RMH systems. Wire a thermostat to it if you want to be able to have it shut off automatically once gasses drop below a certain threshold so it doesn't cool your whole system off if it is unattended.
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Post by DCish on Nov 3, 2015 5:41:27 GMT -8
One thing I love about these heaters is that they are optimized to run on their own power. This makes them safer and more useful in the event of a power outage. Imagine a setup that relies on an electric fan, running at full tilt, then the power goes out. What design features would you need to make sure it is safe under those conditions?
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Post by westcan_yxe on Nov 3, 2015 7:43:29 GMT -8
One thing I love about these heaters is that they are optimized to run on their own power. This makes them safer and more useful in the event of a power outage. Imagine a setup that relies on an electric fan, running at full tilt, then the power goes out. What design features would you need to make sure it is safe under those conditions? I live in a very rural setting with power outages several times each year so I own a generator and one of those portable battery power-packs with a built in inverter. I've also used a solar to battery rig with a separate inverter for camping and other light mobile applications. The tech becomes cheaper and more powerful and reliable each year. I feel like in the RMH community there is a deliberate, almost Luddite rejection of modern tech despite people stating a desire to advance the effectiveness of the systems. I propose that for under $150 a person could modify an RMH heater and have it always light like a dream whether cold or windy, never puff back smoke, never downdraft, and offer the ability to stop worrying about ISA in the construction of the heat extraction/storage and just suck every last bit of heat out of the system while using an absolutely trivial amount of electricity. Power outages are very infrequent and very easy to deal with especially for an enthusiast who is already in a culture of sustainability, or prepping, or permie culture, or off-grid living. If someone is calling themselves prepared they already know how to deal with power outages.
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Post by daniel on Nov 3, 2015 9:33:52 GMT -8
It is not as much avoiding technology as not wanting to be let down by it like in a power shortage. If power is cut (depending of how often this could happen in your community) you need a backup of energy which is comprised of batteries, power inverters, cables and a whole bunch of things, these have a certain usable life after which they need to be replaced, they get to be expensive in the long run. You could use that money for a trip and enjoy some nice things. Keep it simple
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Post by patamos on Nov 3, 2015 22:35:30 GMT -8
Well a few responses come to mind: - Yes i am somewhat of a luddite. - KISS -A good by-pass damper solves all the starting issues - Combined with a slightly oversized bell it can be tweaked on the fly to optimize combustion and harvesting efficiency under all internal and external thermal conditions. The flue gas exit temps can be brought down into the 40c range… Anything below that is splitting hairs.
- Finally, and most concertedly, we all have enough electro-mechanical white noise in our lives. Ya some in line fans are very quiet. But our felt-sense awareness picks up on the subtlest of noises/vibrations. The sound of a hearth fire is woven into our phylo-genetic memory as 'deeply soothing'. The sound/feel of an electric fan... is quite the opposite.
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Post by daniel on Nov 4, 2015 1:15:46 GMT -8
Hi Patamos, I have a bell of 5.8 sq meters not counting the ceiling a 1.44 well insulated riser for a 8" system, it seems to work well for the first time I lit it while still somewhat wet (my windows got all foggy) and this with little medium quality pine wood. If the space around the riser is about 10cm except for the space above the firebox which is larger should that be ok as a bell in your opinion? I found a nail red hot in the firebox with that amount of wood
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Post by Vortex on Nov 4, 2015 1:49:11 GMT -8
For me the beauty in the design of these stoves is their simplicity, so if it needs an electric fan to work it's a bad design.
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Post by daniel on Nov 4, 2015 12:31:07 GMT -8
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Post by satamax on Nov 4, 2015 12:57:50 GMT -8
Daniel, what's your base size? I mean heat riser's diameter?
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Post by patamos on Nov 4, 2015 22:06:55 GMT -8
Daniel, Glad it is working!! Regarding bell sizing, ya, the other dimensions matter. INcluding height and insulation of your exit flue. In general i would refer to Peter's formulas as he had done the bulk of research on these matters. Others like Satamax have a better grasp of the specific numbers than i do.
The jury is out as to whether your barrel is considered a bell or not. It certainly sheds much heat, but the stratified free gas movement (which may or may not define a bell…) is not likely happening in that turbid an environment. If anything the barrel downdraft is behaving more like a flue run, with gasses being pushed out by positive pressure in the heat riser and pulled down/along by negative pressure in the exit flue.
Part of why i so often advocate for inclusion of the bypass flue is because it is part of the design of the old grundofens i first learn to build. Usually it involves two exits at the top back of a tall firebox, with one side having an adjustable plate. Once the operator is familiar with the look and sound of optimized combustion, they can tweak the damper to vary the percentage of gasses running through the harvesting chambers. As has been discussed on earlier threads, the bell sizing without a bypass damper is based on making sure the system works under all conditions. When that particular ISA and mass is more saturated with heat (later in the burn or after reloading…) it is less efficient at harvesting. So my proposal is to slightly oversize the ISA of the bell to enhance harvesting under such conditions, but also use the bypass to stretch the effective operating capacity in the other direction as well.
The double flue is an old technique, being rediscovered by many of the fine folk who participate in this forum.
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Post by daniel on Nov 4, 2015 23:53:43 GMT -8
Hi, you raise some very good points here which I have been contemplating for years now. I did participate years ago to build a downdraft gaseification heater with bread oven, very massive and I started to build one for myself but stopped at the time for lack of casting materials etc. The way I see the differences and similarities the downdraft is similar in the first and secondary burn they have a narrowing passage and a secondary injection (we used a metal bar with holes), they usually have a recommended space of 75mm around and all the gases cold and hot flow straight down, the space a above the secondary chamber (similar to a riser) is not as high and is followed by a piece right above which directs the flow down, there is no space above the riser to hold hot gases (that space can not be too big as in the rocket barrel setup) Now my heater has 30cm above the riser and the firebox is in the bell with a whole lot of space above and around it, The channels around the firebox are a bit over 10cm but I have a huge space above the firebox ceiling. I am convinced now that the bell theory is working great and I hope to follow with some data about it. Here is a link to a first little burn s1073.photobucket.com/user/dpodbereschi/media/MVI_30351_zpsgqoabvmr.mp4.hthttp://vid1073.photobucket.com/albums/w396/dpodbereschi/MVI_30351_zpsgqoabvmr.mp4ml
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Post by daniel on Nov 5, 2015 0:14:33 GMT -8
The link above does not work, I should have used this one
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