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Post by jseasky on Jan 18, 2012 20:06:05 GMT -8
peterberg. thanks for quick answer.
I have thoroughly understanded what you say.
To confirm, I summarize it .
1.if the syphon openning must be higher then 90mm, it's ok.
2.if I want to make the firebox lager, try to lengthen the height about 1/6 ratio of distance-from bottom of firebox to edge of syphon openning.
3.be careful of intake volume amount. slit is half of cross-section area of air duct.
and intake is half of the slit again. so intake is quarter of the csa of duct.
here, i have questions.
in common sence, aboundent air supply may good to combustion.
but in your design, intake in botton and both side air slit look unsufficient.
Is there any rule to calculate the c.s.a of intake according to the volume of firebox?
And any ratio to separete total intake into bottom intake and side slit ?
Again thanks your commemts!!
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Post by peterberg on Jan 19, 2012 3:34:30 GMT -8
...in common sence, aboundent air supply may good to combustion. but in your design, intake in botton and both side air slit look unsufficient. This is a sensible question, the answer is a bit complicated, as always. Common knowledge dictates a large supply of fresh air, because literally everybody is tuning his/her fire by ear and eye. First, it's a good thing to realize that an average 20% of the volume of air only, do consist of oxygen. The rest of it are considered ballast gases, it won't contribute to combustion at all, quite the contrary. So, an abundance of fresh air will cool down the fire, some of it will react (5% is already very good) all the rest will be heated and sent up the chimney to warm the birds. So the volume of the exhaust stream is enormous, one reason to use a large chimney. Monitoring the temperature of the exhaust more often than not is leading to the wrong conclusion, because the thermometer doesn't say anything about the volume of gases passing by. All the time, there's lots of oxygen in the exhaust, unused. What I've done, is trying to optimize the air supply both in volume and location. This ultimately resulted in a tiny supply, using half or more of the available oxygen volume, very high combustion temperature, good mixing of combustible matter and air, a higher exhaust temperature in a smaller chimney c.s.a. and a low volume of gases passing through. The Testo analyzer did show a much, much better efficiency, despite the hotter exhaust. Conclusion should be: the rewards of running a healthy fire using a cramped inlet are definitely greater, as opposed to cooling down the exhaust temperature only. Is there any rule to calculate the c.s.a of intake according to the volume of firebox? And any ratio to separete total intake into bottom intake and side slit ? I'm sorry, to my knowledge, nobody has come up with a calculation model yet. The ratio between front and side intake volume is changing during the course of a run, mainly as a consequence of heating up of the ducts. The inlet openings are misleading in that respect, they are a good point to start with. |
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Post by peterberg on Jan 19, 2012 7:02:32 GMT -8
Please keep us posted on the progress of the guy in Belgium... , The guy in Belgium has completed his stove. It's built as a commercial project, the customer was very fond of this setup. The syphon is located on the left, primary air from the right and through the door. Results were pretty good, but not excellent. Some minor tweaks need to be done, in order to make this a very nice mass heater. Unfortunately, because it's a commercial build, I can't tell you much about it. More information about the builder you can ask via personal message. |
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Post by nonius on Oct 21, 2012 6:35:21 GMT -8
Can you add a bell to a regular wood stove (instead of the "rocket"?)
This is probably an idea/ question out of ignorance, but would like to hear the facts :-)
When installing the woodstove (modern 70%, secundairy air, etc) in our house the technician did not want to make any bends (2x 45) in the flue even if it would be more aesthetic in our living room.
Also regulations on woodstoves seem to emphasize straight chimneys, no horizontal parts, etc
Here in this project I see the smoke/gasses are stopped-collected (top of Bell) and cooled in the bell or multiple bells with counterflows and other complex channeling, without any warnings of chimney fire, back-smoke, CO-poisoning, etc.
What is the difference? Can one build a masonry bell on top of a standard woodstove, like leading the chimney straight into the Bell chamber?
Nonius
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Post by peterberg on Oct 22, 2012 0:53:47 GMT -8
What is the difference? Can one build a masonry bell on top of a standard wood stove, like leading the chimney straight into the Bell chamber? The difference lies in the efficiency of the burn. Of course, you can place a bell chamber on top or at the side of a normal iron stove. But... you have to run this stove at the top of its nerves from then on. No slow burning, overnight fires or tuning back anymore. This will create a dirty burn and the lower chimney temperature will cause all the tars to condensate in the chimney. One guy in the Netherlands that I know of, placed a 16 gallon oil drum on top of his cheap and nasty wood stove. The paint of the drum did burn off within half an hour. He had to clean the drum first and used another one on top, so he extracted heat with two drums. The chimney temp went down dramatically and his shed has been cosy warm from then on. But... he admitted tuning the stove down wasn't possible anymore. So he had to run brief, hot fires and had no complaints from the neighbors anymore. The bell itself should be without baffles or anything else, preferably 10 times wider than the exhaust pipe. Outlet should be as close as possible to the bottom, inlet just a bit higher up to avoid a bypass effect. In this way, it isn't important where the pipes are placed at the circumference of the bell as long as the top is closed. This top of the bell chamber will be hottest. When using masonry or the like for the bell, it has to be larger because of the slower heat transfer, but it will work nevertheless. Try it, it's surprisingly efficient. |
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mikik
New Member
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Post by mikik on Dec 13, 2012 7:25:08 GMT -8
I have added masonry bell (double) to my existing stove and I can confirm that it is "surprisingly" efficient. At first I build it as experiment, but it stays until I build a proper masonry mass heater. Thank you for the great information on this forum. And special thanks to Peter and Donkey for sharing their work and knowledge. Will tray to attach some pics.
Vladimir
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