dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 272
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Post by dvawolk on Jun 27, 2017 8:50:58 GMT -8
Progress... I am just about to mount metal white oven... And put 3cm of vermiculite boards arround the heat riser...    I helped myself with some welding rods bound to right dimensions so that they held the heat riser together while the mortar was curing (below). Not shown in the photo is a wooden "spacer" that is very useful, too. It holds the splits 18cm apart and it hangs from the upper edge... I used it in heat riser and when building the square chimney inside the bell...   This is it for now... |
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Post by drooster on Jun 27, 2017 9:54:07 GMT -8
Still a very smart good-looking build.
Sitting on it will be comfy, what final colour and surface will go on the concrete slab tops?
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dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 272
|
Post by dvawolk on Jun 30, 2017 7:12:25 GMT -8
Still a very smart good-looking build. Sitting on it will be comfy, what final colour and surface will go on the concrete slab tops? Hi, drooster, almost all will be clay plastered, the color is yet to be decided. Some bricks will also be seen. |
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dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 272
|
Post by dvawolk on Jun 30, 2017 7:20:18 GMT -8
Progress... Heatriser is finished. Oven frame is inserted. I also added a tower of bricks on the back of firebox that will support chamotte slabs on the ceiling of the bell... Simple clips helped me a lot when I needed to secure them while the mortar was curing. It is such an easy thing to build with perfect chamotte bricks - but such a pain in the ass when building with old clay bricks of regular shapes😵...      |
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Post by Dan (Upstate NY, USA) on Jul 2, 2017 4:47:12 GMT -8
Nice, I don't have anything of value to add today, just like looking at everyone's builds.
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Post by peterberg on Jul 4, 2017 1:21:49 GMT -8
That vertical chamotte chimney inside the bell. It will be heated from both sides... Do you think that is should be taken into account when calculating ISA? At the begining of heating it would be effective ISA but after awhile it won't accept heat any more... The sides of that internal chimney that are exposed to the bell will heat up much faster than the inside. Just because the hot gases are rushing up inside, maintaining a fast streaming core, the walls won't become hot quickly. A bell works by stratification, the gases resist to go down and in the process are shedding heat to the walls. In general, I'm inclined to neglect the inside of the There's also another very important effect in play. Heat will be shed fastest where the temperature difference is greatest when the hot gases are forced down, against their natural tendency. And since energy is streaming from high to low, the gases tend to give off most heat to the coldest places. Until another spot in the same horizontal plane is coldest, and so forth. |
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dvawolk
Full Member
DSR2 125mm open system (actual project)
Posts: 272
|
Post by dvawolk on Jul 4, 2017 9:04:49 GMT -8
There's also another very important effect in play. Heat will be shed fastest where the temperature difference is greatest when the hot gases are forced down, against their natural tendency. And since energy is streaming from high to low, the gases tend to give off most heat to the coldest places. Until another spot in the same horizontal plane is coldest, and so forth. If i understand that correctly: - If we compare bell system to channel system - different thicknesses in walls are less of a problem in bells compared to different thicknesses in channels that have no stratification of gasses... Would that statement be correct? Still it is better to have similar wall thickness all over the system... As of my ISA... I checked it today again and found out that i am 0,83 sq. meters over suggested ISA (7,6 sq. meters form 18cm system size)... Since the bell ceiling is just 30cm over the heat riser i can not lower it down... I found some kind of a solution. I you see the image below. I am thinking of adding a vermiculite boards on the wall that is left and right of the heat riser. This way i can easily cover about 0,7 sq. meters of a brick wall (with vermiculite board on both sides). Since the vermiculite board is insulative, it would take much less of a heat than a brick wall... It won't be the same as taking away 0,7 sq meters of ISA, but i imagine that effectively it would help...  |
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Post by drooster on Jul 4, 2017 9:17:50 GMT -8
... the color is yet to be decided. Some bricks will also be seen. I'm happy about that : I like the look of the bricks. How about a subtle earthy paint job on the slab tops? |
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Post by peterberg on Jul 4, 2017 12:09:55 GMT -8
If i understand that correctly: - If we compare bell system to channel system - different thicknesses in walls are less of a problem in bells compared to different thicknesses in channels that have no stratification of gasses... Would that statement be correct? Still it is better to have similar wall thickness all over the system... Not entirely correct. A bell system is a more efficient heat extractor, nothing to do with wall thickness. Above that, heat is very even distributed in a bell as compared to a horizontal channelled system. In a vertical upstream channel heat is rushing through, just briefly touching the walls... I understand this heater sports a bypass isn't it? No need to stay exactly within the recommended limits I would say. In case I'm wrong and a bypass is absent, your vermiculite board solution is correct. |
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Post by satamax on Jul 4, 2017 13:35:59 GMT -8
Peter, do you remember my early experiments. On one of my first j tubes, made out of gas bottles, i made an upright chimney out of one of those 35kg bottles. I was exhausting from 139mm diameter. Into a 290mm gas bottles, slowing the flow right down. It was heating real well. Better than when i transformed it into a Bell.
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Post by peterberg on Jul 4, 2017 23:40:08 GMT -8
Of course, when there's a much, much wider section in a vertical chimney the flow will slow down and more heat could be extracted by the walls. So you are right in this respect, but I was talking about a straight vertical chimney, not widening at any point.
To be honest, I don't recall you transforming the same thing into a bell but if you did, there have been almost certainly other factors in play. For example, the cross section area of the gas bottle you mention is exactly four times the csa of the exhaust leading into it. With tolerances this tight, just a small flaw could influence the whole working of the thing. The exhaust pipe sticking into the propane canister could be such a flaw, I've seen it happening at Adiel's workshop during my visit in 2015.
By the way, nowadays I am a strong advocate of somewhat larger proportions like 1 to 5 as absolute minimum for a properly sized bell.
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Post by satamax on Jul 5, 2017 0:53:25 GMT -8
Yep Peter. Too tight a tolerance. Led to the bell working badly. Can't find the thread tho.
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Post by pyrophile on Jul 6, 2017 9:21:17 GMT -8
Peter, what do you mean 1 to 5? Width/lenght? Height/wide?
Is a drawing possible?
Thanks
Benoit
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Post by peterberg on Jul 6, 2017 10:14:08 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.
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