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Post by Esteban Campestre Abejil on Aug 17, 2014 8:36:34 GMT -8
Hi Guys. I'm whriting from Chile, southamerica. Sorry for my bad english. I'm Tarzan I'm working in a 4-inch system too, with horizontal feed. I tried to keep the batchbox proportions as similar to those used in 6-inch systems I've seen here in the forum. I've been forced to modify some. The principal has been the depth of the batchbox, because firewood here usually is 33 cm long. So I modified that from 28,8 cm to 38 cm. I'm trying to create a very efficient heat exchanger (the smallest as possible), because our house is small, we haven't space for a mass here and we don't feel happy to waste heat throwing it outside. I'll share soon my heat exchanger design. I congratulate you on your excellent forum and the multitude of innovative ideas that are developing and sharing here. Esteban.
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Post by satamax on Aug 17, 2014 9:28:00 GMT -8
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Post by peterberg on Aug 17, 2014 12:21:26 GMT -8
I've been forced to modify some. The principal has been the depth of the batchbox, because firewood here usually is 33 cm long. So I modified that from 28,8 cm to 38 cm. Hallo Esteban, welcome to the boards. Regarding the batchbox proportions: keep as close to the original as you can. The only exception happened to be the depth of the firebox, an increase of 50% is tested and tolerable. All the other measurements are crucial, the thing is fairly critical balancing between working excellent or not at all. Use the spreadsheet introduced here: batch box dimensions. When it's not mass but small footprint you are after, you could use some small barrels stacked upon each other, forming a single bell. I'd wish you succes, as far as I know you are the first builder of such a stove in Chile.
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Post by ericvw on Aug 17, 2014 12:52:11 GMT -8
Welcome, Esteban! What a wonderful thing to have someone south of the EQUATOR implementing a Rocket heater! Boy, are you in for a treat, both with the heater and the excellent advice and experience of these rocketing folks! Please follow the excel spreadsheet closely as Peter suggests.... it's dead on accurate. And of course keep posting and add some pics when they become available. Glad to have you in the fold, Eric VW
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Post by Esteban Campestre Abejil on Aug 17, 2014 13:48:03 GMT -8
Thanx a lot, Satamax, Peterberg and EricVW. Your advices and greeting are so importan to us. I'm following this forum for some months, but only about a week I comes a registered member. I've learned a lot here and with Ianto Evans book. The excel spreadsheet es wonderfull. My design dimensions are taken from an interesting post of Dvawolk, but the spreadsheet es more complete My thoughts regarding the heat exchanger are directed to make it as small as possible (a long column of 2 to 3 barrels one above the other, it seems not very recomandable in a highly seismic country like Chile). To do this I figured a way to almost double the dissipation surface. These are some old pictures (before I thought in a frontal feed), but I think it will serve to illustrate where I'm going. I promise to share the current design barely finish it (I should make it more realistic, as the availability of materials and costs). A 3D view of the sketchup modelI'm looking forward to your comments. Esteban.
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Post by peterberg on Aug 17, 2014 23:54:41 GMT -8
This is very interesting, could work in my opinion. One proviso though: a batch box runs better with more space above the riser than pictured here.
Where about are you in Chili? It's a very stretched out country with very large winter temperature differences between north and south.
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Post by Esteban Campestre Abejil on Aug 18, 2014 6:03:25 GMT -8
One proviso though: a batch box runs better with more space above the riser than pictured here. I read about it (the space in the top of the heat riser), but I was doubting about how big it should be. I have given this 5 cm. How much would you recommend? Where about are you in Chili? It's a very stretched out country with very large winter temperature differences between north and south. We currently live in the south, on the coast near the city of Valdivia (39°48'30" S, 73°14'30" W). Here occurred the largest earthquake of the twentieth century, in 1960. It is a very rainy and humid climate, indeed the rainiest area of Chile. Here deforestation is a serious problem. In the past this was a great forest, the "Valdivian Rainforest". But today the native forest recedes rapidly thanks in large part to the exploitation of firewood, giving way to eucalyptus. Eucalyptus, plus the derofestación of hills and other factors have resulted that in 10 years rainfall descended from 2400 to 1800 mm annually. This is killing local ecosystems, while authorities seem not to want know what is obvious to anyone who observes a little. This is a bad for all of southern Chile. Therefore we care help spread more sustainable heating systems. The average wood used here is 8 or 9 cubic meters per year. Another question: Here it is difficult to get perlite or vermiculite. I've been checking on other high temperature insulating, such as ceramic wool (1050ºC continuous tolerates this material. 1270ºC sporadic), but it is expensive! This stove is actually a first test. It is intended to remain in this house currently rented. But we want to build another more definitive in a house we hope to build next year, on the big island of Chiloé (further south). Do you know of any economic insulation we can use? Maybe something more handcrafted. In Evans's book I read that you can use a mixture of clay and sawdust. But I guess it should not be as efficient and certainly heavier. Here I have available a very good clay used in pottery. If so, what thick should be used in the heat riser? (sorry! my english!!)
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Post by satamax on Aug 18, 2014 8:53:59 GMT -8
Esteban.
Your drawings bother me! Where is the downdraft in the barrel, in the second drawing?
If you have nice clay, and access to old bricks or roofing tiles, floor tiles etc. You could grind a nice chamotte, and make yourself a nice core with it. Then just get some rockwool (not glasswool) and hold this around the batch box and heat riser with sheet steel or even chickenwire. Rockwool, if held correctly, is plenty good enough. Tho, you need 4 inches of insulation.
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Post by Esteban Campestre Abejil on Aug 18, 2014 9:10:04 GMT -8
Returning to the dilemma of the heat exchanger...
I must meet three basic conditions: 1) You must take up little space (ideally 50 x 70 cm base) 2) It should not be too high (ideally 1.3 m) 3) should dissipate maximum heat (how much is the minimum that should come out of the exhaust?)
The cylindrical design that presented to you miss the 1st condition: bring down the gases surrounding the "heat riser" takes up too much space in the back, while leaving a free and useless space above batchbox. In this, we must add the required space for the exhaust pipe, making it inconveniently long in depth (my english! Sorry!).
I'm thinking it would be a good alternative to send the gases from the heat riser to the front (above batchbox) and make it down the sides of the stove, keeping the intermediate air flows, as in the previous image. Maybe putting some vertical flat panels where the smoke down, separated by other panels where air rises. I think a picture would help to understand what I imagine (soon).
I have doubts about how to ensure that the hot gases circulate through these panels really equally and how that whole circuit would be cleaned.
I do not know if the complexity of building would be justified, although it is always easier to work with flat plates instead of curved. Anyway, I think it's worth draw and calculate costs.
Mother! If only I had a bigger house!
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Post by Esteban Campestre Abejil on Aug 18, 2014 9:36:38 GMT -8
Esteban. Your drawings bother me! Where is the downdraft in the barrel, in the second drawing? Oh! Sorry Satamax. Hot combustion gases downdraft is represented in the leftside draw. In the right side, the air flow, ascending. If you have nice clay, and access to old bricks or roofing tiles, floor tiles etc. You could grind a nice chamotte, and make yourself a nice core with it. Then just get some rockwool (not glasswool) and hold this around the batch box and heat riser with sheet steel or even chickenwire. Rockwool, if held correctly, is plenty good enough. Tho, you need 4 inches of insulation. I will build the heat riser with an iron pipe 5mm thick. I guess it's enough. It need to be thicker? Does the mixture of clay and grinded old bricks you recommend me is for insulation? I feel lost in this regard. My problem for insulate is that here is very difficult to find high temperature insulation. Only isolating walls are available. Do not tolerate a lot of heat. Perlite is available at 800 km (Chile is long like a noodle!) or maybe 500, not less. Esteban.
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Post by satamax on Aug 18, 2014 11:53:49 GMT -8
Esteban, "metal is doomed" no metal in the burning parts of a rocket, otherwise it will fail miserably! Rockwool or stone wool is plenty good enough, if you have a refractory clay part to protect it from the highest temps of the burn. en.wikipedia.org/wiki/Mineral_woolYou don't have any of that stuff around? For the bell, if you can manage 70x50x130cm, you have a 3.5m² bell, which seems sound with a 4 incher. So, you won't have room for aditional mass; You will either have to live without mass, exept, may be, the wall behind the stove. Or you could pile some bricks or else on a rectangular bell.
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Post by satamax on Aug 18, 2014 11:56:00 GMT -8
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Post by Esteban Campestre Abejil on Aug 18, 2014 14:34:58 GMT -8
Thanx, Satamax!
The mineral wool sold here resists 800ºC only. So I figured it would not be appropriate for the heat riser. It is good news!
Some new questions:
How thick should be firebricks to protect the mineral wool? 1 inch is enough?
I should put 10 cm insulation in the heat riser. What thickness should I put around the combustion chamber?
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Post by DCish on Aug 18, 2014 16:32:13 GMT -8
Just a thought, but I believe a batch box will dump a lot of heat very quickly. With no mass to store it, I'd think you'd have a quick heat, then a quick cool... Is that what you are hoping for? I don't think I've read of a rocket tuned for long burns yet, most develop high heat quickly and rely on thermal mass to spread out the heat over time.
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Post by Esteban Campestre Abejil on Aug 18, 2014 20:44:16 GMT -8
You have a good point there, @dcish. I would love to build a mass rocket stove here. But I can not because the house is not mine, I rent. But I think... This will be an 4-inch system. If you compare it with a 6-inch system there are a enormous difference: 6-inch area is about 176 cm2. 4-inch area is about 78 cm2. This means that a 4-inch system will burn a very small amount of wood per hour. I suppose that will be suficient heat to keep warm a bad isolated house like this. My son and I did a very primitive experiment to estimate how much firewood consuming an 4 inch rocket: we build a "J" with coffee cans (4 inches) and larger ones to contain a mixture of clay and sand, as thermal mass. We do not use insulation because the object was to find out how much wood could devour, and compare it's consumtion with ours current stove (we call her "The Paleolithic Stove"!). The result was that the prehistoric "J" coffee cans consumed less than half of paleolithic one, letting go by the exhaust a very hot and almost no visible smoke. Of course, after a week of use, the cans were corroded by fire and all became just a nice memory of father and son. This gave us a hint: If a Paleolithic stove (that don't stop throwing smelly smoke like crazy) is able to heat our house (with some difficulty), a rocket stove with equal dimensions should achieve that with maybe third firewood consumption. Of course, this is just a guess. Maybe someone could help me calculate how much energy would produce a rocket stove as I'm planning Hugs!
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