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Post by ronyon on Feb 17, 2014 23:10:19 GMT -8
So could a bell be filled with stone, steel, aluminum, glass bottles and other fairly large bits of debrie, to increase both the mass and the surface area? Nothing too small lest we create insulative air pockets, but base ball size would seem good. Nothing too flat either, rough or round would be better to avoid stemming the free flow of gasses.
Since bell sizing seems based on internal surface area , adding this junk might allow for fine tuning. Basically this is like Matt's bricks stacked inside a bell build but with random shapes to increase surface area.
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Post by peterberg on Feb 18, 2014 2:33:53 GMT -8
I'd say you are missing some other point about bells. They need to be a great deal wider than the channel leading to it in order to slow down the velocity of the gases. That's the main requirement to let gravity does the separation of hotter and cooler gases. When stacking bricks inside a bell you have to keep in mind the open space should be at least 4 times as wide as the inlet channel.
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Post by Robert on Feb 18, 2014 4:56:26 GMT -8
When stacking bricks inside a bell you have to keep in mind the open space should be at least 4 times as wide as the inlet channel. by 4 times wide you mean ISA or CSA? I was thinking to make one stove by filling the barrel with the bricks... something like this stoves from Finland: link - link2
So than as i understand the space above the heat riser will be a bell but in the bottom part if the space beetwen the bricks and the riser will not be 4 times wider, it will act more as a contraflow and channel systems?
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Post by peterberg on Feb 18, 2014 9:52:38 GMT -8
I am talking about CSA. Four times is an estimate, but I'd reasoned more will be better. See the good info thread by Erica Wisner, gases heating up from 20 C to 1000 C will expand 4.3 times so compensation like that is called for in order to achieve separation of hotter and cooler gases by gravity. The links do show a poor man's Swedish kakelugn (hope this is spelled right), instead of tiles on the outside there's a barrel around it. And yes, it will act as a contraflow system when the space is too tight. Moreover, a true bell does have both the inlet and outlet close to floor level. When built too tight, stratification will not take place and the bulk of the gases will shortcut to the exhaust opening.
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Post by ronyon on Feb 18, 2014 10:52:54 GMT -8
Thank you Peter. I suppose some added mass inside might be ok, but not so much as to make the bell act like a bench? Maybe orderly stacks would be better, as their effect on cross section could be easily calculated.
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Post by peterberg on Feb 18, 2014 13:21:21 GMT -8
I suppose some added mass inside might be ok, but not so much as to make the bell act like a bench? Maybe orderly stacks would be better, as their effect on cross section could be easily calculated. Correct. The Russian bells do sport those orderly stacks because of the way those are built. Nearly always, the top is closed using the same bricks as the rest of the stove. These are fairly large bricks but nevertheless too small to span the bell in one go. To make it possible they build columns of bricks inside to support the closing bricks. Those columns are free standing and won't touch the sides of the bell. This way, there's mass added and some internal surface area as well.
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Post by satamax on Feb 28, 2014 5:26:51 GMT -8
When stacking bricks inside a bell you have to keep in mind the open space should be at least 4 times as wide as the inlet channel. by 4 times wide you mean ISA or CSA? I was thinking to make one stove by filling the barrel with the bricks... something like this stoves from Finland: link - link2
So than as i understand the space above the heat riser will be a bell but in the bottom part if the space beetwen the bricks and the riser will not be 4 times wider, it will act more as a contraflow and channel systems? Sandy/endruner has given it a try. Don't know how good this is, but there's data there. blog.dragonheaters.com/derrick-8-rocket-masonry-heater-part-2-data-log-3-hour-burn/By the way, we haven't seen Endruner over here for a while!
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