peace
New Member
Posts: 19
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Post by peace on Sept 20, 2010 15:13:05 GMT -8
1. In Ianto's book there's a diagram showing that it's better to have round exit flue because in a square, the gases don't flow as well...
For making a brick exit flue would it be ok if it's tall & thin(9" by 6") with cob rounding up top and at the bottom to make it flow better?
Or will the gasses basically flow virtually as well through a square?
2. For insulation under the bench, could slip wood shavings work or would they burn?
Thank you VERY much for all your help and teachings and kindness and openness, Daniel
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hpmer
Full Member
Posts: 240
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Post by hpmer on Sept 20, 2010 16:35:00 GMT -8
2. For insulation under the bench, could slip wood shavings work or would they burn? Not sure if they would burn under the bench, but the benefit to sawdust in a cob mix in the heat riser is that they do burn out, leaving small air pockets which are the real insulator. The key is sawdust mixed in with cob, which then burns out leaving cob with tiny air pockets. |
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Post by Donkey on Sept 20, 2010 17:12:58 GMT -8
Umm...
1) I wouldn't, the cob is likely to be ALSO rough, which will loose you more than you gain.
Just make the flue slightly larger..
2) Wood shavings probably will burn. What's the floor made of? will it burn too? If not, mix the wood shavings with a little clay slip. The chips will char out leaving the clay (filled w/ holes) behind, which is still insulative.
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Post by peterberg on Sept 21, 2010 8:26:45 GMT -8
...Or will the gasses basically flow virtually as well through a square? Somewhere I used to have a simple formula to recalculate a rectangle to a circle. Just to show how the flow in a round chimney is compared to other shapes. OK, here it is... 2 x W x L ------------ =Df W + L Df is the fictive diameter. When you try a square, you'll find it to be equivalent to a circle with a diameter which is the same as the side of the square. Hope this will make sense, I'm not sure the wording is right... |
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Post by Donkey on Sept 22, 2010 9:18:18 GMT -8
Thanks Peter.. I'll definitely add that one to my tool box.
Usually, I've needed to figure from a given pipe size, as the pipe is the limiting factor design wise..
Take your pipe, figure the area of the circle, then find the square root of that.
The square root will be the length of each side (assuming perfect square).
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