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Post by peterberg on Nov 13, 2014 2:14:37 GMT -8
That's easy. Klemen in Slovenia found out a single masonry bell with a 6" batch box inside could be as large as 6 m2 maximum. I've found out myself that a steel single bell could be around 5 m2. This is all when coupled to an adequate chimney stack, of course.
Imperial measurement: 64.6 sq ft and 53.8 sq ft respectively. These aren't hard numbers so you have to find out yourself what the tolerances are. Just to be sure, best to implement a bypass of some sort. Not in the top of the bell preferably, halfway the bell height would be safer temperature wise.
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Post by PNW Dave on Nov 15, 2014 15:37:31 GMT -8
Thanks for all the help with ISA calcs everyone. Here is what I’ve come up with for my two potential bell sizes. The area of the 9 half barrel bell consisting of barrels 5, 6, 7, 8, & 9 will be like a chaise lounge for two, the idea is to cut the barrels to create a single airspace. Since I want to have each barrel step up .5 to 1 inch, the lounge area could be around 4 inches higher than barrel 1, in hopes that the lounge would not have any problem collecting lots of heat. 9 barrel bench isa (four barrel ends)- 11,927 in. Sq 82.82 ft. Sq 7.6 m. Sq —————————————————---- [ 5 [ 4 [ 3 [ 2 [ 1 [ [ —————————————---- [ 6 ] 7 ] [___]___] [ 8 ] 9 ] [___]___] 6 barrel bench isa (three barrel ends)- 8017 in. Sq 55.67 ft. Sq 5.17 m. Sq —————————————— [ 4 [ 3 [ 2 [ 1 [ [ ————————————— [ 5 ] [___] [ 6 ] [___] I think the process is more important than the end result, since nothing is permanent and we will all learn a lot along the way. This aligns well with my thought process, I really enjoy experimenting with a hands on approach to learning. If my design works well, great! If not, there are tons of proven methods I can revert to. While sharing along the way benefits us all.
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Post by peterberg on Nov 17, 2014 12:19:45 GMT -8
It has been tried out the simple way. Klemen in Slovenia figured out the maximum size for a single bell coupled to a dead end bench. Which happened to be 6 m2 or 64.6 sq ft. I did the metal barrel tower myself, acting as a single bell which was still running well at 5 m2 or 53.8 sq ft. This is all with a 6" batch box rocket as the engine core. In order to calculate for another size of core, see how the ratio is to a 6" core and scale the ISA accordingly.
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Post by patamos on Nov 17, 2014 17:55:12 GMT -8
Is anyone aware of what (if any) difference ought to be calculated when a quick-radiating metal barrel is used for the initial downdraft? Is it included in the ISA of the bell? And how might this vary with denser (non-metal) downdraft chambers?
thanks pat
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Post by patamos on Nov 18, 2014 12:44:18 GMT -8
In other words, do we calculate the ISA of the metal barrel sides and top into the number for metal bells? And calculate the ISA in a downstream earthen bell bench as per masonry bells?
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Post by peterberg on Nov 19, 2014 2:30:01 GMT -8
In other words, do we calculate the ISA of the metal barrel sides and top into the number for metal bells? And calculate the ISA in a downstream earthen bell bench as per masonry bells? That's a way to calculate ISA, yes.
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Post by patamos on Nov 19, 2014 20:41:01 GMT -8
Thank You
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Post by erikweaver on Feb 9, 2015 17:57:24 GMT -8
For a 6-inch system size:
64.6 ÷ 6 = 10.767 ratio to a masonry bell; 53.8 ÷ 6 = 8.967 ratio to a metal bell.
So, for an 8-inch system size:
8 * 10.767 = 86.136 square feet, for a masonry bell; 8 * 8.967 = 71.733333333 square feet, for a metal bell.
As a point of reference, a rectangle 4-feet per side and 5-feet tall with a 4x4 footprint, would be 20-sq.ft. per side (times four) plus a 16-sq.ft. top = (20*4) + 16 = 96 sq. ft.
I recall reading that Peter said the floor's surface area is *not* calculated in sizing the bell, just the walls and top (the floor remains too cool to have enough impact to matter very much).
I don't think bells are supposed to have any internal walls (is that design called something else?) but if they did (to help support the top, for example), the surface area of that would have to be included too, is that right?
If so, that would add up very quickly. OR, because the supporting walls are inside, and they don't really contribute very much to radiation into the room, should one ignore their surface area?
And if one uses supporting internal walls, wouldn't columns be better than walls, because they allow better air flow, and stratification? (Thinking, like the ancient Romans, and others, used to support their heated floors.) That would add even more internal surface area.
For columns, it would seem to make sense to me, to use whatever common brick size one has available, nominally 8-inches where I'm at. Or one could stack half-block, and still have a nominal 8x8 inch column. If 16-inch pavers were used as the top, a 12-inch space could be made between each column.
Do you all think that would provide adequate air movement to allow proper stratification, so as to still perform as a masonry bell?
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Post by peterberg on Feb 10, 2015 2:58:25 GMT -8
I don't think bells are supposed to have any internal walls (is that design called something else?) but if they did (to help support the top, for example), the surface area of that would have to be included too, is that right? Yes, that's right. When the inner walls are touching the outer walls plus the floor and ceiling the bell stops being a bell. It would be a labyrinth type then, with a planned start and a fixed direction of all the gases, being hot or cold. If so, that would add up very quickly. OR, because the supporting walls are inside, and they don't really contribute very much to radiation into the room, should one ignore their surface area? The inner walls aren't contributing to the radiation into the room directly. But that's not the point, the bricks or whatever are extracting heat and as such these are part of the bell's ISA. And if one uses supporting internal walls, wouldn't columns be better than walls, because they allow better air flow, and stratification? (Thinking, like the ancient Romans, and others, used to support their heated floors.) That would add even more internal surface area. Spot on Erik, columns are the best way to go. It's an effective way to add more ISA and more mass at the same time. The size and spacing of the columns greatly depends on the size of the bricks or whatever you want to use to close the top. It's also an elegant way to position an oven somewhere above the riser. Stratification will still occur provided the cross section area right in front of the inlet opening is at the very least four times as large as that opening. In effect, the columns or central wall in a bench for example (standing free from other walls) shouldn't block or restrict the bell below it's minimum size. Those columns are what the Russians did for an awfully long time and still doing today. They build heaters solely with one large size of brick and firebrick. This way they are able to close the top with that same brick size. You are on the right track, it sounds like you are able to visualize the whole thing.
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Post by erikweaver on Feb 10, 2015 11:08:50 GMT -8
Peter, thank you for correcting and affirming as needed, I appreciate your kind guidance.
Is there one or two primary sources for learning about bell design? Something like Evan's "book" on RMH? Or maybe just a one or two page PDF that summarizes the critical elements?
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Post by peterberg on Feb 10, 2015 12:24:48 GMT -8
Not that I know of, Erik, I don't know of a summary either. My way of building up a theory is emperical: doing an experiment to prove or disprove whether a theory is valid or not. When it isn't, devise another setup to check the next brain wave. Insight is aquired slowly this way but it is proven at the same time. The bell thing is reasonably described at Kusznetsov's site The whole theory of free gas movement is unproven, his combustion chambers are crap in my opinion. But the bell idea is quite good documented, it'll take a lot of time to read it all.
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Post by satamax on Feb 10, 2015 12:31:40 GMT -8
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Post by grizbach on Feb 11, 2015 2:04:23 GMT -8
For a 6-inch system size: 64.6 ÷ 6 = 10.767 ratio to a masonry bell; 53.8 ÷ 6 = 8.967 ratio to a metal bell. So, for an 8-inch system size: 8 * 10.767 = 86.136 square feet, for a masonry bell; 8 * 8.967 = 71.733333333 square feet, for a metal bell. Eric, You need to figure for cross section area. 6"=28.27sq" 8"=50.24sq" For a 6"system, 64.6÷28.27=2.285ratio For a 8"system, 50.24x2.285=114.8sq'masonry Terry
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Post by erikweaver on Feb 11, 2015 9:50:57 GMT -8
Thank you Terry, I have made the change to my notes.
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Post by erikweaver on Feb 11, 2015 13:56:35 GMT -8
Thank you Satamax, I read that Short Course the other day. I'm still browsing the web site.
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