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Post by ronyon on Apr 4, 2020 23:36:06 GMT -8
So I'm trying to wedge an 8" batch box into a 15 wide file cabinet. Centering the 10" OD, 8" ID riser in the file cabinet would leave 2.5" x10" of wasted space on either side of it. If I moved the riser all the way to the right in the box, there would be a single 5"x 10" space to the left of it that I could exploit. 5"x 10" happens to have the same c.s.a. as an 8" riser This would put around 4" of burn chamber to the right of the risers center line, and 7.5" to the left of the center line.
Would this unbalanced firebox work OK, or would it just cause problems?
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Post by peterberg on Apr 5, 2020 7:51:56 GMT -8
So I'm trying to wedge an 8" batch box into a 15 wide file cabinet. Centering the 10" OD, 8" ID riser in the file cabinet would leave 2.5" x10" of wasted space on either side of it. If I moved the riser all the way to the right in the box, there would be a single 5"x 10" space to the left of it that I could exploit. 5"x 10" happens to have the same c.s.a. as an 8" riser This would put around 4" of burn chamber to the right of the risers center line, and 7.5" to the left of the center line. Would this unbalanced firebox work OK, or would it just cause problems? This looks like an interesting puzzle. There's a second problem in what you try to achieve but let's try to answer the first. I assume you are talking about the inside of the firebox so there would be 4" to the right of the port and 7.5" to the left. I'd say it would work OK as long as the port isn't situated in the very corner of the firebox. The second possible problem is this: 5" by 10" as a downstream channel seems right for an 8" system but it isn't, not quite. So in case you are planning to use it as such, apply this simple formula. 2xLxW/(L+W)= D, where L is lenght and W is width of the opening, and D is diameter of the equivalent round duct. In your case: 2x10"x5"/(10"+5")= D, 100"/15"= 6.7" as equivalent. This is leaning on the fact that a square or rectangle is not as good as a circle, aerodynamically speaking. This space is too cramped for a downstream channel in an 8" system, sorry. It looks like you are planning for a five-minutes riser. In that case it's a different story since the riser side of things leaves more space than the 10"x5" rectangle you mentioned. The shape of this opening is highly irregular but a rough calculation says it's 60.7 sq" now instead of 50 sq". Could be just enough but not overly so.
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Post by ronyon on Apr 6, 2020 3:33:20 GMT -8
Wow. Peter, an amazing and generous reply, as always. I hadn't understood to apply the diameter of the equivalent rule throughout the system, I just figured it applied to risers only. Now I know better. Given this wee bit of understanding gained, and your rough calculation, I wonder if centering the riser would actually give me more downstream channel space? Would the two 2.5 x 10 + ? spaces be the equivalent of one larger space?
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Post by peterberg on Apr 7, 2020 12:45:26 GMT -8
Given this wee bit of understanding gained, and your rough calculation, I wonder if centering the riser would actually give me more downstream channel space? Would the two 2.5 x 10 + ? spaces be the equivalent of one larger space? It would give you 71.5 sq" in total although coupled to a much larger wall area. Wall friction is one of those things where people meddling with aerodynamics stumbles over. I am inclined to think it won't help, rather the contrary.
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Post by ronyon on Apr 8, 2020 8:24:54 GMT -8
Thanks again Peter. I'll plan on centering the riser and using these immediately adjacent spaces as part of a larger bell,or fill them in with cob, rather than trying to get cute with it.
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