rst
New Member
Posts: 24
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Post by rst on Jun 6, 2014 9:49:49 GMT -8
I've been reading the forums and I think I have a general idea now as to what a "bell" is.
I have the impression that half-barrels can be used as makeshift bells by cutting a short but wide inlet and outlet hole on them near the floor. Is there more to it than this, and is this actually notably more efficient at capturing heat (or are there ways to make it more efficient/effective)? How should sizing of the inlet/outlet holes be done (I'm planning for 8" system)? Should they be sized differently when put together in sequence (i.e., progressively smaller)?
As an extension of this question, how would these affect the overall maximum system length? I had originally intended a 20ft pipe run in a bench, but now I'm considering something like three half-barrels which would then be running into 10ft or so of pipe until it reaches the vertical chimney pipe. Would this be feasible?
Thanks
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Post by DCish on Jun 6, 2014 12:39:13 GMT -8
Peterberg has done much work on bell sizing, mostly for 6 inch systems, I believe. The number I recall offhand is 3 square meters of internal surface area (not counting the floor) available for heat absorption / dissipation for a 6" system. The total area diminishes with the area of each added bell, I forget by how much. There was a recent discussion of bell sizing for 8" systems, too. If you do a search of posts made by Peterberg you should find it pretty quickly, I think. Also, someone else, i think Matthew Walker, has done quite a bit with half-barrels as bells. Also worth doing a few searches under his name... or maybe just with "barrel" and "bell" as search terms. Good luck, and do post how it goes!
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Post by satamax on Jun 6, 2014 12:56:50 GMT -8
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Post by matthewwalker on Jun 7, 2014 6:17:09 GMT -8
You've got the idea, the ends can be cut as large as possible so that the multiple sections act as one bell, or you can make the openings system size down low so each section is an individual bell.
As for length, there are way too many variables to say. One system could struggle with two halves while another might push 10 of them. Combustion core design, materials, radiator size or lack thereof, chimney height, location, bypass or not, etc., etc.
I like to let them develop organically as I build. Get the guts in place, light it up, and start adding sections until you are happy with it. Work on it over a few weeks and figure out what features you want, and what is acceptable performance to you.
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