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Post by #FreeLab - Freedom Laboratory on Mar 8, 2012 1:18:12 GMT -8
Hello,
I am now designing a heating rocket stove for local sqatting community in Warsaw. There are two design nuances I would need your help with.
We shall be using the concept shown at page 42 of Approvecho's book "Designing Improved Wood Burning Heating Stoves", while slightly modified: - The heat exchanger will be vertical, sitting on top of a rocket stove. - There will be no fan. - For heat accumulation, the heat exchanger will be filled with loose gravel.
Now, the questions are: 1. For a room of 4 x 5 x 2.5 meters, what size of the heat exchanger (and the stove) should be used? 2. How can we calculate size of the heat exchanger vs gravel pebbles size to achieve uniform flow cros-section size?
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Post by pluton5 on Mar 8, 2012 2:42:08 GMT -8
witam,,, zrób jakiœ szkic tego co chcesz zrobiæ,jestem pod wra¿eniem,¿e ktoœ w Polsce nareszcie siê zainteresowa³ piecykami RS,RMH pozdrawiam andrzej kalifor8@wp.pl
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Post by Donkey on Mar 8, 2012 8:21:05 GMT -8
I'm not familiar with that book. Do you have an image, or link out?
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Post by #FreeLab - Freedom Laboratory on Mar 8, 2012 12:11:59 GMT -8
Hi, The book is available here: #FreeLab Rocket Stove Workshop materials. Attached please find a rough sketch, hopefully showing what is the idea. Petros
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bud
New Member
Posts: 11
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Post by bud on Mar 8, 2012 12:13:13 GMT -8
Kirk,
It's apparently one of the original publications of Approvecho. download link is listed here:http://www.aprovecho.org/lab/pubs/arcpubs
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Post by #FreeLab - Freedom Laboratory on Mar 10, 2012 7:57:49 GMT -8
Guys, any hint re: my initial question?
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Post by Donkey on Mar 10, 2012 11:36:53 GMT -8
Well, I'm having a hard time downloading the book, I keep getting corrupted files. Also, for some reason, I can't load the large version of the image you posted. Grrr! Can't very well answer the question without some idea of what yer talking about. I'll try again in a few minuets, but first a stab in the dark kinda comment.. With standard rocket stoves, I don't think anyone's really quantified how much heat is stored/produced by a given amount of bench (assuming that's what you are asking). The very little bit that I can see of the small version makes me think that you are NOT building a standard rocket stove, perhaps even not a rocket stove at all.. ??
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Post by Donkey on Mar 10, 2012 11:56:22 GMT -8
Aha!! I finally got the book. Page 42.. Interesting stove, but NOT a rocket stove, mate. You might want to ask your question of the folks over at Aprovecho.. It's their gizmo after all.
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Post by woodburner on Mar 10, 2012 15:09:44 GMT -8
Well, I'm having a hard time downloading the book, I keep getting corrupted files. Also, for some reason, I can't load the large version of the image you posted. Grrr! I had the same problems, but I used the link bud posted, it's aproviecho's site, and theres a few more interesting publications there too.
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Post by #FreeLab - Freedom Laboratory on Mar 10, 2012 22:25:19 GMT -8
Donkey, What I am taking from the book is just the heat exchanger thing, modified. It will be sitting on top of the classic J-shaped combustion chamber rocket stove. So it will be a rocket stove, cross my heart. My major question concerns the heat exchanger. It is the pebble granularity vs. the whole HX diameter, to meet air intake crosscut surface. I can, of course, optimize it by the assuption that we have all pebbles round and equal (just some spreatsheet tweaking), but perhaps someone has already solved this problem in a better way?
Anyway, we plan to build several RS version this year, as infrastructure modules for our off-the-grid facility in Poland - kitchen, bath, and possibly even power/heat cogeneration. There is also a plan to make very cheap and simple RS to be distributed among poor and homeless people before the winter. Last winter took a toll of over 70 people dead in Poland due to hypothermia or carbon monoxide poisoning. I believe rocket stove can help others to survive.
Petros
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Post by peterberg on Mar 11, 2012 2:35:04 GMT -8
So, the goal is a rocket stove with a 50 gallon barrel on top. As I understand it, you want the smoke exhausting through the barrel which is filled with pebbles. Admittedly, there ought to be room between the pebbles so the gases should be able to stream through. How much room there will be is highly depending on the size, shape and uniformity of the stones/brick fragments/or whatever.
A major and easily overlooked flaw of this idea is the start-up phase. The rocket, when cold, will generate some smoke until it'll come up to temperature. This smoke is dissipated through the pebble barrel and will leave some soot behind in there. The net result will be a gas path which will be clogging up in a certain number of start ups. Cleaning can only be done by emptying the barrel, scrubbing the pebbles and putting it all back again.
A way to circumvent this problem is to use a by-pass until the rocket is burning cleanly. But even then, there isn't a way to check the rate of pollution inside the barrel. Prone to errors, and it could be dangerous too.
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Post by #FreeLab - Freedom Laboratory on Mar 11, 2012 2:43:25 GMT -8
Good point, Peterberg. I will keep it in mind for future designs and hopefully will come up with some solution. At this time, however, we shall only need the heating for couple months, probably no more than 8-10 weeks. I will make short user guide for the community, pointing out that when the heating period is over, they should dismantle the HX, take some pictures and a sample of pebbles for me and wash the remaining thoroughly. After this procedure we will be able to estimate the rate of soot residuals growth. What do you think about it?
Petros
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Post by leewaytoo on Mar 11, 2012 4:42:04 GMT -8
if you could get two barrels with increasing diameters that fit the formula then use the second barrel over the top of the burn barrel. use pipes that run vertical in that space between the outer barrel and the burn barrel, fill around the pipes with cob/or something that will retain heat. your exhaust will pass through horizontally thru this second barrel space and then exit on to where ever your exhaust goes to outside. so this second barrel would contain your "bench" with the air tubes convecting your heat, hopefully. so maybe it might work..
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hpmer
Full Member
Posts: 240
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Post by hpmer on Mar 11, 2012 5:09:43 GMT -8
If space is the issue, why not stack the second barrel on top of the first, extend the now uninsulated heat riser thru the middle and surround that with your pebbles?
Probably not quite as efficient as horizontal, but gets around the sooting issue Peterberg described. Somewhere on this board is a link to a guy in Australia I think that used this concept to heat water (not pebbles) and he seemed quite pleased with the results.
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Post by leewaytoo on Mar 11, 2012 5:13:49 GMT -8
something like this
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