cab
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Post by cab on Feb 11, 2011 15:57:19 GMT -8
What is the wood load per burn in this heater?
I am wondering if it could be adapted to include a fire tube heat exchanger, like the one in Richard Hill's heater design, in the bell???
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Post by peterberg on Feb 12, 2011 2:28:40 GMT -8
Load per burn has been 10 kg (22 lbs) when using dense wood. This is the largest configuration tested, scaled up from a much smaller one. The larger one behaved exactly the same as the first, which led to the conclusion it could be scaled up again.
I do think it's entirely possible to use a fire tube heat exchanger in the first bell. Results with several configurations of one, two or three bells suggest it doesn't matter how the heat will be extracted. As long as the size of all the channels remains the same throughout.
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cab
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Post by cab on Feb 12, 2011 6:18:14 GMT -8
What are the physical dimensions of the unit? How large would it need to be to take a 50kg wood load? I would like to get 60,000 btu/hr or so (fired twice a day) output to heat 1000 gallons of water for in floor tubing heat.
Could it be configured such that the flue gas after exiting the siphon turn up 90 degrees then towards the front of the unit 90 degrees through a fire tube heat exchange, then 90 degrees up and out the top? Sketch below....
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Post by peterberg on Feb 12, 2011 9:47:49 GMT -8
Dimensions on the inside of the firebox are: wxdxh=40 x40 x48 cm, which equals 15.7 x15.7 x18.9 inch. The fuel isn't stacked higher than 12 inch, the rest above it has to be open space.
Multiply the above dimensions by 1.75 and you'll get the 50 kg heater about right. The syphon opening has to be enlarged too, probably 14" x 4.5". Chimney size would be 8". Quite a large heater, larger in any case than the contra-flow heaters not uncommon in the U.S.A.
As far as I can judge the sketch, it's about right. The syphon itself ends up vertical and provided it is long enough it will drive the heater beautifully. So, your configuration is possible but I think it's ridiculously enormous.
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Post by zoidberg on Feb 12, 2011 10:06:38 GMT -8
Peter,
It is common knowledge in these forums that RMHs 6" size and smaller are kind of nervous and difficult to deal with, does your design somehow solves the problems small systems have ? Can your design be scaled *down* to about any size ?
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cab
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Posts: 33
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Post by cab on Feb 12, 2011 10:44:59 GMT -8
Dimensions on the inside of the firebox are: wxdxh=40 x40 x48 cm, which equals 15.7 x15.7 x18.9 inch. The fuel isn't stacked higher than 12 inch, the rest above it has to be open space. Multiply the above dimensions by 1.75 and you'll get the 50 kg heater about right. The syphon opening has to be enlarged too, probably 14" x 4.5". Chimney size would be 8". Quite a large heater, larger in any case than the contra-flow heaters not uncommon in the U.S.A. As far as I can judge the sketch, it's about right. The syphon itself ends up vertical and provided it is long enough it will drive the heater beautifully. So, your configuration is possible but I think it's ridiculously enormous. I have to satisfy a 80,000 btu/hr heat load on a -25F day..... Width is fixed at 16". How would 16" wide by 36" deep by say 24" tall work? |
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Post by peterberg on Feb 12, 2011 13:35:38 GMT -8
Width is fixed at 16". How would 16" wide by 36" deep by say 24" tall work? Not the foggiest idea. You have to build it yourself and test it. |
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Post by peterberg on Feb 12, 2011 13:49:08 GMT -8
Can your design be scaled *down* to about any size ? The original test bed was a rather small one. Firebox of 12" x12" x18" high. Could only manage to stuff 7.5 lbs of soft wood in it. Worked like a charm with syphon output temperatures of around 1400 F. again and again. So, it can be scaled down to any size if you ask me. |
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cab
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Post by cab on Feb 12, 2011 13:55:38 GMT -8
Width is fixed at 16". How would 16" wide by 36" deep by say 24" tall work? Not the foggiest idea. You have to build it yourself and test it. Have your fireboxes always had a square floor? |
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Post by zoidberg on Feb 13, 2011 0:54:48 GMT -8
The original test bed was a rather small one. Firebox of 12" x12" x15" high. Could only manage to stuff 7.5 lbs of soft wood in it. How long would it take to burn that amount of firewood, if you do remember ? |
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Post by peterberg on Feb 13, 2011 1:47:58 GMT -8
Have your fireboxes always had a square floor? It has been always very close to square. Deviation less than 1 inch. How long would it take to burn that amount of firewood, if you do remember ? Between 45 and 60 minutes, until the glowing phase is dying out. |
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cab
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Post by cab on Feb 13, 2011 5:45:51 GMT -8
Have you built the siphon section of firebrick as shown in your sketch up graphics or only of castible refractory as in the pictures of actual units?
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Post by peterberg on Feb 13, 2011 9:07:51 GMT -8
Have you built the siphon section of firebrick as shown in your sketch up graphics or only of castible refractory as in the pictures of actual units? Of firebrick in some units, castable refractory in others. I've also used double-walled insulated stainless steel chimney pipe, and vermiculite board at one occasion. The insulation of the pipe crumbled, the 1600 F rated board couldn't stand the heat inside the syphon. High quality castable refractory worked best because of the rapidly heated up one inch walls. Not everybody's job to make the molds and the vibrating table though. |
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cab
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Post by cab on Feb 13, 2011 13:14:32 GMT -8
Have you been working from any formulas for the dimensions of the syphon or found any basic rules for the dimensions?
I am wondering if there is any critical distance how far below the intake the u shaped portion must go, for example...
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Post by peterberg on Feb 14, 2011 1:44:24 GMT -8
Have you been working from any formulas for the dimensions of the syphon or found any basic rules for the dimensions? I am wondering if there is any critical distance how far below the intake the u shaped portion must go, for example... , I do hope you've read this topic in its entirety. If you didn't, please do so now. Please also read this thread, especially the first half, before "Teach" more or less hijacked the topic. You'll find nearly all the answers to your questions are already there. |
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