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Post by mhkhankan on Jan 25, 2013 16:37:10 GMT -8
2# port width 0.5, height 2.2, depth 0.36 (this last one is not very important, keep the port as short as possible) Looking again at the table we see some differences between my formula results and your SKP file. I am really concerned with width measurement more than the rest. because I think they are not important. Width 54.3 to 51.6, CSA of the port and Depth '' but you said keep it short and it is not important. Could you please explain and correct me if I am wrong? |
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Post by mhkhankan on Jan 25, 2013 17:00:32 GMT -8
1# firebox width 2, height 3, depth 4. Sorry Again please explain the differences? What about tolerances through out the whole system dimensions? could you please mention if any or at least which ones are critical? Another question, Any rules for the flue? Can we use a smaller dimension/CSA? Thank you in advance for everything you do. |
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Post by mhkhankan on Jan 25, 2013 17:06:41 GMT -8
Please explain the difference between black Vs. white Oven. It's really simple, actually. The black oven will become black inside because the smoke path is leading through it. The white oven will stay clean, the smoke path is leading around it. The black variant, when built out of fire bricks will heat up quicker as compared to the white one built of the same material. A steel oven is almost always a white one. Thanks Again, I choose the white oven where the smoke path is leading around it. I will use bricks for the oven and every other part of the system. plus I will fit it on the top of the fire box. But would it affect the P-Channel since hot gasses will pass by it? are Firebricks enough as insulators or do I still need to insulate please elaborate? |
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Post by peterberg on Jan 26, 2013 1:55:10 GMT -8
Is it a rule of thumb or is it math? This is math, definitely. It is leaning on the fact that a square or rectangle is less efficient in corners where the stream slows down. The circle is the most efficient shape, the largest area within the smallest perimeter. It has something to do with the stream building up in layers, in the center the hottest and the highest velocity. Nearer to the sides, slower and cooler. The fast streaming core in a square (vertical) duct will be more or less round, not square at all. Several formulas do exist, some are more complicated and precise than others. I've seen one at permies.com but I can't find it anymore, that one happened to be very exact. I am using a simple one. (2*length*width) / (length+width) = fictional diameter. Try this one, you'll find out that the square is on a par with a diameter of one of the square sides. This simple formula is been used for over a century to calculate the capacity of a rectangle chimney. Mostly by chimney sweeps from Italy, who migrated to the north in the 19th century. One of my grand, grand, grandfathers was one of them. You seem to think every sketch is very precise, but in fact it isn't. Couldn't actually, because of the dimensions of the bricks. The port is 70% of the riser csa, the ratio of 2.2 to 0.5 is an approximation, this could easily be 2.25 to 0.49, whatever is the best fit. I'll look through all your further questions about this, but when using bricks you are bound to get to approximate numbers. Edit: I've found the link to much more comprehensive formula. |
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Post by peterberg on Jan 26, 2013 2:04:15 GMT -8
Looking again at the table we see some differences between my formula results and your SKP file. I am really concerned with width measurement more than the rest. because I think they are not important. Width 54.3 to 51.6, CSA of the port and Depth '' but you said keep it short and it is not important. Could you please explain and correct me if I am wrong? When the port of the 6" version is 40 mm deep, that's alright. I've tested a port of 120 mm deep and had markedly worse results. Conclusion: 30 mm would be alright and 50 mm too. There's some tolerance in these calculations, the quoted dimensions are derived from the model which delivered the best results. Nothing more to it, my sketches are made in such a way that stoves built using these almost certainly will work. |
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Post by peterberg on Jan 26, 2013 2:19:23 GMT -8
What about tolerances through out the whole system dimensions? could you please mention if any or at least which ones are critical? Another question, Any rules for the flue? Can we use a smaller dimension/CSA? The port size and shape are fairly critical, as is the p-channel. Down to a few percentages I would say. Dimensions of the firebox much less so. However, the csa (width*height) of the firebox as compared to the (round) riser not more than a ratio of 3.6. Tested that, any larger and the stove will become unpredictable. No rules for the flue, I've not tested literally everything, sorry. I'll leave that part to people like you, so you can find out some other aspects yourself, publicizing it and joining the list of fame. ;D |
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Post by mhkhankan on Jan 28, 2013 18:12:48 GMT -8
Hi Peter,
The file is ready how can I send it to you to verify it.
This is a rough draft.
Well I live now in the northern part of Italy, its cold and that's what made me think of searching for DIY Heater systems so I landed here.
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Post by peterberg on Jan 29, 2013 1:22:13 GMT -8
The file is ready how can send it to you to verify it. You can send it to my mail address. See personal message. |
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Post by satamax on Jan 29, 2013 2:36:10 GMT -8
Hi Peter, The file is ready how can send it to you to verify it. This is a rough draft. Well I live now in the northern part of Italy, its cold and that's what made me think of searching for DIY Heater systems so I landed here. Which side? If around turin, to towards the french border, we could meet at some point. I'm at about 40km from the winter olympic sites. |
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Post by mhkhankan on Jan 29, 2013 5:55:06 GMT -8
Hi Max,
Well, I live near the city of Varese. I do not know how far is that from you. I would love to meet and learn from you guys. Please share your opinion and guidance if you can.
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Post by satamax on Jan 29, 2013 9:30:36 GMT -8
Mhkhankan, we're living about 270km away. I'm nearly full west of Turin, just after the Italian/French border. As for sharing my opinions. I should admit i haven't the brain set onto RMH lately. I have the impression of turning dumb.
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cab
New Member
Posts: 33
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Post by cab on Jan 29, 2013 19:38:02 GMT -8
However, the csa (width*height) of the firebox as compared to the (round) riser not more than a ratio of 3.6. Tested that, any larger and the stove will become unpredictable. So for a 6in dia riser, the csa is roughly 28in2. 3.6 x 28in2 = 100 in2 so the firebox can be a maximum of 10 in wide by 10 in tall for a 6 in flue  or am I misunderstanding something? |
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Post by peterberg on Jan 30, 2013 1:46:58 GMT -8
So for a 6in dia riser, the csa is roughly 28in2. 3.6 x 28in2 = 100 in2 so the firebox can be a maximum of 10 in wide by 10 in tall for a 6 in flue or am I misunderstanding something? It's the ratio of my own prototype, which delivered very good results. The rectangle of the firebox is slightly larger than that, because you have to subtract the sloped sides of the firebox. For example, my prototype is 8.68" wide and 13.02" high which will total up to 113.06 in2. The area of the sloped sides would be 3.5"x3.5"= 12.25 in2. This subtracted from the firebox opening will result in 100.81 in2. Very close to the 1:3.6 ratio, which is 101.79 in2 by the way. Before you ask: a firebox using another ratio than 2:3:4 for height, width and depth isn't tested. Therefore, I don't know how these will perform. |
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cab
New Member
Posts: 33
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Post by cab on Jan 30, 2013 10:25:47 GMT -8
I'm guessing you meant 2:3:4 for width, height, and depth.
10" x 10" cross section on the firebox makes me wonder how realistic this would be for real batch heating in a practical application. 2 splits and a little kindling and its full- Maybe ok for a very very small space I suppose if you don't mind refilling the firebox every hour.
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Post by Donkey on Jan 30, 2013 13:25:23 GMT -8
I have been UTTERLY surprised by how much heat one of these little stoves can put out.
I'd love to see what an 8 inch version can do.
Having said that, there's only so much heat that a piece of wood can produce. It's a beautiful thing that RMHs can A) make the most of the fuel and B) capture and thus make the most of the heat.
In the end, the limiting factor WILL be how many cubic (whichevers) that need to be heated over how many BTUs being produced.
Keep in mind though that the REAL goal is to heat the people, the house doesn't really need it.. That thought alone can (and maybe should) change your heating strategy, at least somewhat, for the better.
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or am I misunderstanding something?
