grga
Junior Member
Posts: 76 
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Post by grga on Aug 21, 2017 4:01:02 GMT -8
I am also interested how the white oven will operate. I will hopefully soon start similar project myself.
Other questions are:
- what will be the experience about bypass is it necessary or can be simplified and not used
- is the chimney closure a safe think regarding monoxide. I know that it is energy efficient as it completely closes the stove, but usually they said that the stoves should not be closed after the burning but only at the air entrance. Any thoughts on that are welcome.
I like your work and writing very much!
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Post by Jura on Aug 21, 2017 10:53:40 GMT -8
I am also interested how the white oven will operate. I will hopefully soon start similar project myself. Nice you dropped a line as I was about to send you PM as it was you who has already questioned Klemen about the white oven & I thought you had already build your ownstove with an oven. Other questions are: - what will be the experience about bypass is it necessary or can be simplified and not used I wouldnt skip it if you want to have a smokless startup. - is the chimney closure a safe think regarding monoxide. well .. we have a periodically burn stoves after ~an hour even the glowing phase is over and so is the CO danger The heat is transmitted not only by convection but also via radation, closing the air entry helps to stop the air flow, but doesn't stop radiation toward the getting colder and colder chimney. the question is how much heat we may loose that way For myself I will install a chimney closure but never for sb. else. btw. I have realized I have seen somewher a white oven placed higher than right over a firebox. It was a job of friend of mine Artur Milicki Here is a build of him  Maybe he 'd find some time to write us how such placed oven operates |
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grga
Junior Member
Posts: 76
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Post by grga on Aug 23, 2017 11:38:42 GMT -8
Hi Jura!
I did made a test set up with the oil drum as a bell and a white oven on top which was made from 3 cm shamote bricks and isolated but the rest of the barrel was not isolated (similarly to the case when you want to heat the house) - max temp in oven was maybe up to 200C after longer run (2 or 3 full loads) and max fire
The idea to place the oven on top of batch box I see in two other projects and it seems a good idea to me - see the link in this thread.
For my build I plan to place batch box and the oven a bit higher in the bell (batch box cca. at least 0.5 m from floor) where are a bit higher temps...
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Post by Jura on Aug 24, 2017 0:12:16 GMT -8
I did made a test set up with the oil drum as a bell and a white oven on top which was made from 3 cm shamote bricks and isolated but the rest of the barrel was not isolated (similarly to the case when you want to heat the house) - max temp in oven was maybe up to 200C after longer run (2 or 3 full loads) and max fire Surprisingly low temp. range as for the white oven placed right over the heat riser (if I understood you correctly). For my build I plan to place batch box and the oven a bit higher in the bell (batch box cca. at least 0.5 m from floor) where are a bit higher temps... Exactly what I'am building right now. 40 cm elevated core (heat riser ends @ 1,8 m) and I will place the oven the way its floor will be at 155 cm. I'm pondering whether it wouldn't be prudent to cover the top of the oven with a chamotte brick layer to accumulate some energy and protect the oven form to high temp (if case such occured) |
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dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 271
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Post by dvawolk on Sept 20, 2017 3:23:01 GMT -8
Soooo.
Temperatures outside came close 10°C in previous week and the owner started a small fire... It was a small fire, always less than 1kg of wood, bypass open...
Today i started a small fire 0,5kg of thin wood in front of the port, bypass open. It started somehow lazy... I also needed to have slightly opened door (a 1-2cm gap).
After that i loaded another 1.5kg of wood and the rocket sound was much more obvious. But only with slightly open door (and air inlet opened). When i closed the door tight only the air inlet was open and the rocket sound almost disappeared.
After that i loaded about 3kg of wood, i removed the threshold, totally open the air inlet (removed the inlet door) nad the rocket sound started very obviously. After a few minutes a also closed the door. Bypass still open.
After 10-15 minutes stack temperature reached 150°C, so i closed the bypass. I didn't feel much difference in burning if the bypass was open or shut at this time. But the stack temperature dropped to 80°C. At that time there were mainly water vapours outside the chimney. It burned that way to the coal phase... I let primary inlet open so that gas flow would suck moisture through the chimney and dry heater faster.
Hm, i felt it was a bit lazy in rocketing (??). When i started my cold stove yesterday 6" batchbox it was a much faster start. I would say that this is a difference in vermiculite board only heat riser in my stove compared to chamotte riser surrounded by vermiculite board. Also i would say that it needs a thorough drying prior to judgement...
The stove will be burned daily now with a similar amount of wood to get i to dry state. How long would that be? 1 or 2 weeks maybe?
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dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 271
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Post by dvawolk on Sept 20, 2017 3:32:28 GMT -8
And the second thing is appearance...
There is a small crack formed (prior to lightning).
And i did a mistake when i painted with diluted water glass (Pottasium) over the parts that were oiled (and dried) prior to that... The surface there didn't suck water glass inside so it dried on the surface and formed a foggy film. At some places i will have to slightly sand the surface and oil that parts again...
The other problem is that it was hard to cover the whole surface with the same amount of water glass. Also the jute mesh sucked more of water glass from the surface - and now at some places it formed a mesh appearance. I will cover the whole surface with water glass diluted only by 1:1 with water... Previously i diluted it with 1:3 to 1:4 parts of water... I should have cover it with water glass more thoroughly (i think).
And maybe it would be a better option to paint with diluted water glass (1:4) FIRST, then leave it to dry and after that oil it on the desired parts. This is speculation i will try that somewhere else... But one thing is for sure: do not put water glass on non-porous surfaces (oiled surfaces included..)...
Will make some photos next time. I hope to get some feedback from you, especially regarding the layziness of the rocket and drying times (the wall is 15cm thick at some parts).
Best regards,
Klemen
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Post by Jura on Sept 20, 2017 5:59:07 GMT -8
And the second thing is appearance... There is a small crack formed (prior to lightning). Would love to see where the crack formed. looking forward for the photos. And i did a mistake when i painted with diluted water glass (Pottasium) over the parts that were oiled (and dried) prior to that... yeap..I try to avoid oils' (any hydrophobic substances) usage if the surface is going to be worked with. The other problem is that it was hard to cover the whole surface with the same amount of water glass. Also the jute mesh sucked more of water glass from the surface - and now at some places it formed a mesh appearance. I will cover the whole surface with water glass diluted only by 1:1 with water... Previously i diluted it with 1:3 to 1:4 parts of water... I should have cover it with water glass more thoroughly (i think). I heard of a brick stove treated with a sodium silicate, left for a longer period in a pretty moist climate and after starting a fire it gave a birth to marvelous "crystals" of "the water glass" on the clay surface. I wouldn't call it laziness during the drying phase at all. Peter claimed ppl get lazy with time and for the sake of easy burn leave the bypass ajar during normal stove operation which of course decreases overall burn efficiency. (more flue gases go directly to the chimney) That's what I'd rank a sin of indolence. How about the white oven temps ? Have you happen to pay attention to it ? |
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Post by pinhead on Sept 20, 2017 6:05:10 GMT -8
Soooo. Temperatures outside came close 10°C in previous week and the owner started a small fire... It was a small fire, always less than 1kg of wood, bypass open... Today i started a small fire 0,5kg of thin wood in front of the port, bypass open. It started somehow lazy... I also needed to have slightly opened door (a 1-2cm gap). After that i loaded another 1.5kg of wood and the rocket sound was much more obvious. But only with slightly open door (and air inlet opened). When i closed the door tight only the air inlet was open and the rocket sound almost disappeared. After that i loaded about 3kg of wood, i removed the threshold, totally open the air inlet (removed the inlet door) nad the rocket sound started very obviously. After a few minutes a also closed the door. Bypass still open. After 10-15 minutes stack temperature reached 150°C, so i closed the bypass. I didn't feel much difference in burning if the bypass was open or shut at this time. But the stack temperature dropped to 80°C. At that time there were mainly water vapours outside the chimney. It burned that way to the coal phase... I let primary inlet open so that gas flow would suck moisture through the chimney and dry heater faster. Hm, i felt it was a bit lazy in rocketing (??). When i started my cold stove yesterday 6" batchbox it was a much faster start. I would say that this is a difference in vermiculite board only heat riser in my stove compared to chamotte riser surrounded by vermiculite board. Also i would say that it needs a thorough drying prior to judgement... The stove will be burned daily now with a similar amount of wood to get i to dry state. How long would that be? 1 or 2 weeks maybe? Generally when comparing a low-mass riser such as vermiculite board or ceramic-fiber to a higher-mass riser such as chamotte (if I'm understanding the term correctly) or firebrick, the low-mass version will invariably "rocket" much more aggressively, all else being equal. I've built two different versions of the batch box - one with a clay-ash-perlite riser and an identical one with a ceramic-fiber riser. The ceramic-fiber version beat the higher-mass version in every conceivable way. Having said that, the clay-ash-perlite (or in your case, chamotte) was probably adequate for the job it was doing, though I'd say the two versions are in different leagues. However, no meaningful inference can be made when comparing your two stoves until this one is thoroughly dried out. |
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Post by peterberg on Sept 21, 2017 1:02:48 GMT -8
Klemen,
What you've got here is a wet heater as the very edge of what can be achieved. I'll second Pinhead in this, you can't make any meaningful inference until the thing is bone dry.
My heater is also one at the very edge, I always start the thing with the door ajar while the air inlet is fully open. Started from cold running a full batch it won't produce higher chimney temperatures than 80º C.
Air inlet opening isn't a static thing after all, the air speed is equally important. When my heater is thoroughly warm and running full tilt the door is closed and the air inlet reduced to half, which means it's only 1/8 of the riser csa. And the thing is roaring like mad at that very moment, I assure you!
It is possible to run these heaters by ear and one eye on the chimney temp, the process is developing always along the same lines. Now I come to think about it: this could be a very nice way to control the thing by a small computer and a servo motor operated inlet, temperature and air speed are the only required data...
Any takers?
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grga
Junior Member
Posts: 76
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Post by grga on Sept 21, 2017 3:52:19 GMT -8
It is possible to run these heaters by ear and one eye on the chimney temp, the process is developing always along the same lines. Now I come to think about it: this could be a very nice way to control the thing by a small computer and a servo motor operated inlet, temperature and air speed are the only required data... Any takers? I was already thinking about making some automatic control of air inlet. Can it be specified by a simple rules or phases and objectives in each phase to make control. Also what would desired values for V and chimney T be? can it be specified simply by a set of phases something similar to this: phase : no fire -> temperature of the core lower than 150C -> no action all closed start fire -> triggered manually by a button and start timer -> open air to max for 5 minutes or until desired V (?) and Tmin (? 40C) is reached fire present -> core T more than 200C-> control air inlet to achieve desired Air speed V and or? chimney T fire done-> indicated by temperature of the core Tc<400C and timer >60 minutes ->close air inlet |
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kpl
New Member
Posts: 47
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Post by kpl on Sept 22, 2017 3:41:00 GMT -8
Air speed is quite difficult to measure, compared to temperature. Probably it's enough to measure temperature change, probably in several locations, like bell and flue. Now I come to think about it: this could be a very nice way to control the thing by a small computer and a servo motor operated inlet, temperature and air speed are the only required data... Any takers? |
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Post by drooster on Sept 22, 2017 9:25:07 GMT -8
Air speed is quite difficult to measure, compared to temperature. My car (1993 Volvo) and many others use an Air-Mass-Meter to feed data to the engine's CPU. Perhaps that could be a simple solution to measuring the input. Other engine management systems use slightly different metering systems. One of them would fit the purpose ideally. |
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kpl
New Member
Posts: 47
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Post by kpl on Sept 22, 2017 11:08:57 GMT -8
car MAF also came first to my mind, but it usually uses "heated wire" principle, which is quite difficult to interface. There is no cheap simple arduino solution, or at least I have not seen one. Air speed is quite difficult to measure, compared to temperature. My car (1993 Volvo) and many others use an Air-Mass-Meter to feed data to the engine's CPU. Perhaps that could be a simple solution to measuring the input. Other engine management systems use slightly different metering systems. One of them would fit the purpose ideally. |
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Post by alphakilo on Sept 28, 2017 10:01:34 GMT -8
Exactly what I mentioned yesterday, the cross section area of the inlet opening of the bell versus the cross section area of the bell itself. The greater the difference, the more the velocity of the gases will be slowed down. When slowed down sufficiently, gravity can do its thing and let the hotter gases rise relative to the coolest. Hi I am new in this interesting forum and I don't understand everything. When you say the "inlet opening of the bell" I understand the exit of the riser. That multiplied by 5 to have the correct cross-section of the bell, or I am completely off? Thanks again for all the info. |
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Post by peterberg on Sept 28, 2017 11:32:01 GMT -8
Hi Alphakilo, welcome to the boards.
The inlet opening of the bell could be the riser's exit, yes. But in a double bell system that inlet could be anywhere else in the second bell.
But to answer your question, the riser's cross section area multiplied by 5 will give you the minimum cross section of the bell. But there's no such thing as the correct csa value. In practise, more is better and as such I didn't find a maximum value, yet.
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