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Post by foxtatic on Oct 19, 2022 7:16:45 GMT -8
I’m in the process of designing an RMH next to my kitchen. Trying to figure out where to integrate a white oven.
Build notes: 6” riserless core design, either DSR2 or DSR3. Core and flue will be housed in a brick column around 5’ tall, 2’ wide, 2 & 1/2’ deep (127x60x73 cm.) The “bench/bell/stratification chamber” will sit next to the core column, connected by an open side wall. It will be 36” tall x 36” wide x 20” deep (91x91x50 cm.) This comes out very close to the recommended ISA size.
I would like to put a white oven in this design. Building it above the core would be the hottest location, but more difficult to design considering clearances, supports, refractory materials etc. Putting the white oven in the “bench” side would be very easy to design, but may not be hot enough even with an insulated door.
I have never seen anyone report the temperature inside their bench or bell. Does anyone know how hot this part of the system gets? Do you think it’s too cool there and only worth building an oven in the gas stream above the core? I think around 350 to 400 degrees F would be about the lowest reasonable temp to have a functional oven.
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Post by josephcrawley on Oct 19, 2022 14:25:01 GMT -8
You'll want it as close to the exit of the top shoe box as possible. I would recommend insulating the inside of the bell around the oven to focus the heat on the white oven. The bench will definitely not be warm enough. This is not a DSR but it does include a white oven and works very well. donkey32.proboards.com/thread/3316/7-sidewinder-bake-oven-bench |
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Forsythe
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Post by Forsythe on Oct 20, 2022 12:25:17 GMT -8
I’m in the process of designing an RMH next to my kitchen. Trying to figure out where to integrate a white oven. Build notes: 6” riserless core design, either DSR2 or DSR3. Core and flue will be housed in a brick column around 5’ tall, 2’ wide, 2 & 1/2’ deep (127x60x73 cm.) The “bench/bell/stratification chamber” will sit next to the core column, connected by an open side wall. It will be 36” tall x 36” wide x 20” deep (91x91x50 cm.) This comes out very close to the recommended ISA size. I would like to put a white oven in this design. Building it above the core would be the hottest location, but more difficult to design considering clearances, supports, refractory materials etc. Putting the white oven in the “bench” side would be very easy to design, but may not be hot enough even with an insulated door. The first step I'd recommend is setting targets for the design parameters. (Which function of the multifunction stove is the *most* important one of your needs? And the second most-important?) ... and then go from there. At current, it sounds like this has maybe 3-4 uses. kitchen warming, living room warming, baking, and potentially also cooktop.  I've noticed a general-pattern aphorism with stoves attempting to serve more than 2 dedicated, permanently-designed-for purposes, and do it all off of the heat from 1 single firebox: They almost always suffer from the Jack-of-All-Trades is Master-of-None" pitfall of competing design parameters. ...and those conflicting aspects lead to compromises in the functionality of all 3+ stove purposes. ...Often the best solution is to add another firebox that can fire at a separate time to heat a dedicated part of the oven and/or mass —as is common with masonry heaters and grundöfen that have 1) a "herd" (hob/plancha) 2) a bake-oven, and 3) a thermal storage mass for heating the room gradually, over hours—rather than broiling the living space with heat from a searingly-hot cooktop every time you fire the stove's (single) firebox... ...and then having to fire it again a couple hours later because too much heat went out the cooktop and wasn't stored in the slow-release thermal mass... A really clear demonstration of these conflicting design parameters is the evolution of Firespeaking's "CabinStove" iterations by Max Edelson:  The first design had a low firebox, far below the intended cooktop space, and it pushed the flue gasses immediately downward into *dense* mass before exiting to the chimney. (attempting to avoid wasted thermal loss into the air when the unit was fired only for radiant heating needs.) ...The result was a stove that didn't really work at all as a cooktop, but it did store heat in a small footprint fairly well. The second iteration used some insulating firebrick in the firebox, and pushed flue gasses up-and-across-the-underside of the cooktop/plancha/hob. ....but the firebox was still too low and the hob didn't get hot enough to cook on. (supposedly it didn't store enough heat, either, to keep the cabin warm in which it was built.)  That too-low firebox issue can ruin a cooktop design, as it has for a few folks tinkering with various iterations of vortex stove, for example... The gas stream under a cooktop needs to be shallow/narrow and fast-moving... so the space has to be flattened up along the hob underside before being routed elsewhere to achieve decent oven and cooking surface temps.  Max eventually sorted that out, and even built a functional cookstove/bench with a J-tube design instead of a batchbox:  A quick-and-dirty solution, though, is to make the oven portion of your build modular so it can rapidly switch from cooktop/hob to oven by simply employing a reflective & insulative IR baking dome over the hob. This can be as slapdash as a semi-spherical crumple-dome of aluminum foil over a trivet on an RMH barrel....  ...or as bespoke as a fitted, vented, well-insulated (and rigidized] oven dome with a thermometer mounted through the outer wall. (pyroclassic created one of the latter and people are often very surprised by how well they work on a standard RMH barrel-top:  (speaking of jack-of-all-trades/master-of-none: The pyroclassic does a lot of things very well... but it also tries to incorporate a water heating exchanger and lacks sufficient mass to store all the heat it produces ... or to create enough backpressure in high winds... resulting in a cooktop near welding temps if you don't have a water exchanger installed... and yet... experiencing massive creosote buildup if you *do* have the water tubes installed... because they go into and shock-cool the whole secondary combustion zone where clean, smoke-free exhaust would otherwise complete its combustion.) (I'm not including a link to the below guy's build, because he almost always uses air-crete... and advises others to do so, too... but then he appears to be unable to connect the dots as to why his air-crete stove components keep crumbling, overheating, and falling apart. Those are potentially dangerous or even disastrous mistakes that could be avoided as easily as googling the free SDS and technical data sheets to find air-crete's thermal stability range...and then googling the burn temps of an insulated wood fire. Lime-based cements like air-crete aren't thermally compatible with high heat rocketstove components. An insulating refractory would be a far more appropriate material selection.)  Temperature-range figures will vary widely based on 2 hugely-variable design factors: 1) the type of food you'll be baking / the speed at which that baking needs to occur [fast, hot, and crispy for pizza / bread? or slow-roasting sinuous meats to a rendered, succulent tenderness?] ... and 2) the shape and orientation of the flue pathways upstream of that oven, which will determine how much heat is available to that oven after passing the hob/plancha and all other doodads, bells, & whistles in their respective orders... Matt Walker's riserless / tiny house cookstove design features a super-hot cooking hob on top —and a slow-roasting oven on bottom— before piping to flue gasses to the bench. The facing design ("Enki", red, on the right, below) is the inverse of that: super-hot bake oven above the firebox, and a hob cooktop which is just hot enough to boil water, but not as steak-searingly hot as most cooking hobs tend to be at their hottest.  ...And one final observation regarding temp ranges: the low-and-slow roasting ovens in most "Tischherd" (table-like stovetop) / plancha / cooktop-Hob style cookstoves tend to be fairly small in internal volume. the remaining heat in the downstream fluegas just can't properly heat a large baking chamber to the needed temps. Many of the older versions sported a "Wasserschiff" (a container with spigot for keeping a moderate volume of water hot throughout the day, similar in function to the samovar often incorporated into Russian pechki stoves.) That water never actually boils in the Wasserschiff because of its distance in proximity to the firebox, downstream of the hob and oven.   |
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Post by foxtatic on Oct 21, 2022 7:01:56 GMT -8
A very thorough answer! I appreciate it and your other in-depth posts that have changed the way I think about materials.
I'm not trying to stack too many functions here, I've seen that folly before and you provided even more examples. Primary use will be heating. Cooktop is out of the question. Just thought it MIGHT be worth sticking a box in the bell and calling it an oven IF the temps would be high enough to justify it there.
Looks like a proper oven would need to be directly in the gas stream for any decent functionality, which could come with compromises to the primary function of being a mass heater. Plus many additional design considerations. And I want to keep this simple.
That dome top has my wheels turning though. Maybe if I top the "core column" with a low-insulative refractory and build an insulated/radiant reflective arch on top of it, I could harvest some heat there above the chimney outlet. It wouldn't be a proper hob (too far from the cores outlet/not quick thermal transfer material) and wouldn't be a proper oven either (not wrapped in hot gas.) Instead it would be somewhere in between that wouldn't compromise the main function of heating and still be easy to integrate into the design.
With an insulated door, it could still give me a food warming box that might bake and yet still drive heat into the mass even when not in use. All while still being hotter than a box in the bell like I originally proposed. Filling the niche of the microwave if nothing else.
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Post by fiedia on Oct 21, 2022 10:49:43 GMT -8
I measured temps inside the bell of a 5' batch. The black oven was sitting on top of the firebox.
I measured that bell temp is dropping very fast from top to bottom. I guess that if you put the oven at bench level, the temperature will not be high enough to bake bred or pizza.
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Forsythe
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Post by Forsythe on Oct 22, 2022 13:13:21 GMT -8
Just thought it MIGHT be worth sticking a box in the bell and calling it an oven IF the temps would be high enough to justify it there. Looks like a proper oven would need to be directly in the gas stream for any decent functionality, which could come with compromises to the primary function of being a mass heater. Plus many additional design considerations. And I want to keep this simple. Yeah, for 350-400°F, the white oven would probably need to either share a sidewall with the firebox, or be directly above it, with flue gas wrapping around 5 sides. **Sidenote:** a white oven can sometimes even get too hot if it is built with the firebox's roof serving directly as the oven's floor. White ovens in contraflow heaters are usually built with a 2" gap space between the fire box roof and oven floor: The flue gas comes up from the rear of the firebox, and partially flows under the oven back-to-front (splitting towards Left and Right at the front), with the rest of the gas stream continuing up behind the oven's rear wall, flowing over the top, then descending along the left and right sides where it meets the split streams that had flowed under the firebox floor.  ...Some early designs of North American masonry heaters had been built with a refractory cast slab serving as firebox roof AND white oven floor; those bake chambers got too hot to bake in while the fire was burning, and had you had to wait at least 45 minutes or longer after the fire died for the bake oven to cool enough to avoid burning the bottom of your food. It sounds like this might work... but I'm not 100% clear on how the "core column" would be arranged... are we still talking about a DSR, or about a batchbox-and-riser design? The image brought to mind with your description is one of a batch box with a domed/arched oven structure placed on top of the firebox with the batchbox riser behind the oven's rear wall. That could certainly work for a bake chamber in a bell. ...come to think of it: might even work with the DSR3 (or Trev's 4" Vortex cookstove) if you put the bake chamber on top of the 2nd "shoebox" (or on top of the Vortex afterburner,) and split the exhaust stream at the front like the 4" vortex cookstove does, and then routed the flue gas up along the Left and Right sides of the oven walls, instead of traveling all the way around to the rear again... (also similar to the contraflow white oven described above, except that the hot gasses would be ascending along the sidewalls of the oven, and filling the bell from there.) If your oven door was well insulated and kept closed when charging the thermal mass bell, that shouldn't cause any appreciable heat losses... might actually help to keep a more-even temperature gradient between floor and ceiling, as the white oven walls would simply be a thermal mass feature at mid-height within the bell...) Now you've got my wheels turning!  |
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Post by foxtatic on Oct 24, 2022 5:36:28 GMT -8
In this case I'm talking about a riserless core, one of the DSR iterations. The exhaust still shoots up towards the roof of the core column (by which I mean a taller part of the bell that encompasses the core and flue.) Since the ceiling of the core column is naturally the hottest part of the bell, I would let it be hot and made of refractory and not insulate it as one usually would. This oven would only be bottom heated: I would simply build an insulated and reflective arch on top of the core column. It would be an oven outside the gas stream, yet still within the insulated envelope of the hottest part of the bell. Not as effective as an oven inside the gas stream of the bell heated on all sides. But also much easier to build with fewer considerations for gas flow and initial starting draft. I do like the notion you presented of building an oven directly on top of the top shoebox of a DSR or Vortex (and I see how that would be too hot in a standard batch box.) Might not work so well with either DSR design though since the DSR2 exhaust port awkwardly exits towards the front of the top core box, and the DSR3 only exhausts in the back so your oven could be no deeper than 15 inches in a 6" system. That leaves the Vortex the way you drew that Vortex with exhaust on either side wrapping around an oven is indeed interesting! |
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Post by martyn on Oct 24, 2022 6:10:16 GMT -8
From my experience with vortex stoves, that might be more like a micro wave or a pottery kiln than a 180c oven ha ha …
Perhaps if the bottom had an air gap between the top of the afterburner and the oven floor and the oven its self was made from 32mm refractory cement it would be more practical to use and also hold some heat for prolonged cooking.
I have a sort of oven in my J tube barrel that has been extremely successful for cooking bread, jacket potatoes etc but even then, the temps can easily be 350c and at that temp it is more akin to a cremation pod!
Placing my vermiculite oven box on top of the hot plate is by far the most controllable method that I use as an oven, you can raise it slightly up or down, use a lid or as a rotisserie or even as a fan oven.
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Post by fiedia on Oct 25, 2022 5:48:21 GMT -8
I looked for "vermiculite oven" but did not find any relevant answer. Could you please give more details ?
Thank you
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Post by martyn on Oct 25, 2022 6:09:12 GMT -8
Yeah sure, near the end I write 180c but I meant the 80c!
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Forsythe
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Post by Forsythe on Oct 25, 2022 17:04:18 GMT -8
From my experience with vortex stoves, that might be more like a micro wave or a pottery kiln than a 180c oven ha ha … I have a sort of oven in my J tube barrel that has been extremely successful for cooking bread, jacket potatoes etc but even then, the temps can easily be 350c and at that temp it is more akin to a cremation pod! Placing my vermiculite oven box on top of the hot plate is by far the most controllable method that I use as an oven, you can raise it slightly up or down, use a lid or as a rotisserie or even as a fan oven. Yes, good points, all. I probably should have noted in my concept drawing that the refractory wall thicknesses and the respective burn/bake chamber's internal volumes were not drawn to an exacting scale. It was really only meant to convey the concept for directing the combustion gasses for a white oven on top within a larger heater bell. I do think this general layout would work for a white oven if Trev's afterburner sported his original all-around insulation on roof, rear, and sidewalls, ( shown in the drawing as a thin gray layer at the afterburner roof, between the afterburner cavity and oven floor slab) and if the bake chamber were made with decently-thick refractory (maybe 2"-2.5" thick castable or dense firebrick slab for the white oven floor.) Dense refractory will diffuse the heat a whole lot more than a steel or cast iron cooktop hob, and it won't transmit the abundant infrared-wavelengths from the ultra-bright flames directly through itself, unimpeded, the way that ceramic glass cooktops do. Best baking performance would probably be done on a trivet baking rack to lift the bakeware up off the oven floor, cooking via convection à la conventional oven. I was thinking that the afterburner roof's insulation would A) ensure clean combustion without robbing heat before secondary burn was completed, and B) help avoid a superheated hot-spot right in the middle of the oven floor... and it would avoid having to include an air-gap between afterburner and oven floor, which would then either raise the roof of the left- and right- horizontal flue paths (thereby slowing their horizontal flow) — or would impede those cooler, post-combustion gasses' contribution to the oven's temperature by separating them from the oven floor with the same air-gap separating the afterburner from oven. ...and within the context of being built into a heater bell, one would have the problem of air expansion within the air gap, and thus needing to give those air-gap gasses a place to expand into... in order to escape from that [enclosed] air gap... otherwise I would be afraid of it either becoming pressurized and going kaboom like a giant ceramic popcorn kernel... or splitting along a seam and then sucking-in, entrapping, and condensing air (accumulating moisture) as the stove cooled down. Maybe if you left the rear wall of an air gap open to the bell... but then you'd more-quickly lose the accumulated bake oven's heat into the bell's gas space, which might shorten the available baking time at sufficient cooking temps. |
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Post by ronyon on Nov 8, 2022 13:27:05 GMT -8
Great thread!
My own "conventional" oven is heated from the bottom only.
It's an old Chambers brand oven, built to conserve gas.
The bottom is a 1/2 inch plate of cast iron and the the walls are heavily insulated, with what I dare not think(probably asbestos).
It came with instructions on how to cook a second meal on the residual heat from the first one.
When our furnace went out , I piled all my loose fire bricks in it and ran it on high.
Even now, light it on cold mornings , to warm up the kitchen.
So what I'm getting is that an oven consisting of an insulated box with a door built over a hot point on the bell might work, but making the floor of the oven the ceiling of the firebox might make the oven unusably hot.
If the space between the oven floor and the top of the firebox was built correctly, we could run cool air through it, and thus control the temperature.
The air passages could pass under the oven and up through the bell, picking up heat, and creating a draft, like a solar chimney.
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jonasp
Junior Member
Posts: 102
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Post by jonasp on Jan 25, 2023 7:51:45 GMT -8
Really interesting thread!
Has anyone actually tested the white oven inside the top of a bell?
I'm considering implementing this in a vortex mass heater but it's completely guess work for me if it'll actually get high enough temperatures..
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Post by fiedia on Jan 25, 2023 14:36:38 GMT -8
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jonasp
Junior Member
Posts: 102
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Post by jonasp on Jan 25, 2023 23:46:51 GMT -8
Thanks for sharing, really interesting! |
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