berko
New Member
Posts: 16
|
Post by berko on Feb 29, 2012 2:11:44 GMT -8
Dear all! There is a house, where i'd like to build a stove with Rocket system, which will heat 2 rooms. I will try to write my train of thought. There are 2 rooms 1,9 and 1,3 kW/h Heating Requirements. (I have calculated this values -15 Celsius Outer and +20 Celsius Inner Temperature so dT~35 Celsius - which is general here) Firebox: Two rooms 1,3+1,9 = 3,2 kW/h. When i burn 1 kg hardwoods i get 4,1 kW energy (assuming 100% efficiency). I calculate 75% efficiency at my stove, so i get ~ 3 kW/kg. I use that stove half day period (i light twice per a day). 12*3,2 =38,4 kW so i need ~ 38,5 kW/12h therefore i have to burn 13 kg/light (exactly 12,83) The shape of firebox will be a Donkey FireTube :-) Room1: 1,9 kW/h Heating Requirment I build the stove from brick, therefore i calculate Heat efficiency of brick. It's about 550 W/m2/h. So i have to build a stove ~ 3,4 m2 area. We use this stove dual mode. First of all to heat and sometimes to cook. Therefore i use a Damper to switch between. Room2: I would like to build a bell or something. But i didn't find any info about sizing of bell. I can calculate the outer area of Bell to transfer 1,3 kW/h but the inner area and shape ? And what's up with the lower flue temperature ? So i'm not sure of it. That's all in first round. I'd love any feedback, advice, idea before i build it Thx, Berko Plan of rooms.
|
|
berko
New Member
Posts: 16
|
Post by berko on Feb 29, 2012 2:18:01 GMT -8
Plan of Heater
|
|
berko
New Member
Posts: 16
|
Post by berko on Feb 29, 2012 2:19:07 GMT -8
Plan 2
|
|
berko
New Member
Posts: 16
|
Post by berko on Feb 29, 2012 2:19:28 GMT -8
Plan3
|
|
berko
New Member
Posts: 16
|
Post by berko on Feb 29, 2012 2:19:47 GMT -8
Plan 4
|
|
berko
New Member
Posts: 16
|
Post by berko on Feb 29, 2012 2:24:57 GMT -8
plan5
|
|
|
Post by Donkey on Feb 29, 2012 8:59:23 GMT -8
I could be wrong about this, but.. I believe you need to calculate the INSIDE area of the bell, not the outside. Also, I'm not too sure about the double heat riser thing. The horizontal feed won't be as efficient as you would like, it will be far more fiddly than a vertical arrangement, you'll be constantly shoving the wood forward. The horizontal run of the feed to the second heat riser (to the heater) looks a bit long, it should be half of the length of the heat riser or less. The bell won't act as a bell should with the heat riser terminating at the top. Inputs to the bell should come in at the bottom or heat will be pumped through too quickly. The space at the top (above the heat riser) may still act as a bell but it will make for a relatively small one and I'm not sure how to judge how effective it will be. It is an interesting concept. You have some experimentation ahead if you really want to do it in this way. Personally, I'd go with one heat riser, run the heat through the cooking area first, then into the bell. It's likely that you could fit a double bell system in the same outer shell as you've planned here (or very nearly the same). I'd place a removable plate directly over the heat riser so that a pot (or pan) could be placed directly on the fire, perhaps two, one in the hot spot and one to simmer with a path between (like a Lorena stove). Flue gasses would pass through the cooking area and into the bottom of the first bell which would be above, then they would pass through a channel which would take them to the bottom of the second bell below and out the chimney in the same place (or roughly so) as you've shown. It seems to me that a smaller bell above would provide a hotter place for the oven while leaving enough heat to drive the rest of the machine. You may need a bypass of some sort to get the thing started.. Peterberg would be the best judge as to whether the thing would work or how well. In any case, you've got some experimenting to do.
|
|
berko
New Member
Posts: 16
|
Post by berko on Feb 29, 2012 12:08:36 GMT -8
I could be wrong about this, but.. I believe you need to calculate the INSIDE area of the bell, not the outside. When i calculate the heat transfer area i view the outside area. But I don't know what's up with inner area. So i need enough heat to transfer to the outer area. I started by your layout. As i know your fire tunnel about 3 ft/ 90 cm. As i see in your picture your heat riser also 3 ft ~ 90 cm. I left from plan the door with air intake on Feed tube (even more Burn tube) and an other door near heat riser 2, where i light up the Burn tube. So i fill up the Burn tube which is about 80 cm long, and i light up it at Heat riser 2. The fire burn from Heat riser 2 to Door of Burn tube. Maybe it will work ... or not ?
|
|
|
Post by Donkey on Feb 29, 2012 17:28:38 GMT -8
When i calculate the heat transfer area i view the outside area. But I don't know what's up with inner area. So i need enough heat to transfer to the outer area. Right. It's not TOO hard to build a bell who's exterior dimensions are correct, but where the interior dimensions are too small. Harder to do the opposite. A slightly generous interior area will almost guarantee an appropriate exterior. The interior area will be the more critical limit. I like my stove, the horizontal feed is rather convenient. I gotta admit though, the wood isn't in the best place for complete combustion as often as a down feed. It's a trade-off fer sure. Either way you cut it, you've got some experimentation ahead. Please to post yer progress! ??
|
|
|
Post by Donkey on Feb 29, 2012 21:20:28 GMT -8
berko, Have you built a rocket stove before? If not, you might want to build a by-the-numbers, standard rocket, lash together in the yard before trying any innovating. Doin' it the tried and true way first will give you a good foundation to work from. Best to make a low risk jobbie that can be modified easily in a safe place first.
|
|
berko
New Member
Posts: 16
|
Post by berko on Feb 29, 2012 23:06:35 GMT -8
berko, Have you built a rocket stove before? Yes, i have built some classic test rocket, therefore i fall in love with rocket Yes. And i looking for something about this ... but nothing ... (although i'm waiting a Russian source ) Here in central Europe, i can calculate and build tunnel stoves (kachelofen) exactly becouse there are some standard. If i comply with these standard, my stove will work. But i didn't find standards about bell/contraflow/rocket stoves. But it's a challenge So If I have understood correctly your stove isn't as efficient as a classic rocket thanks to horizontal burn tube . Can you judge your stove efficient ? Yes of course. I build a test stove like on plans, and i post my progress.
|
|
|
Post by Donkey on Mar 1, 2012 8:58:37 GMT -8
I don't have any of that fancy (or otherwise) test gear, so I won't hazard a guess at numbers.. I rely on my nose and ears to tell me when to fiddle with the fire, when it's not running at it's peak.. The word "efficiency" is one of those that gets tossed about a bit too much and without qualifiers, can mean little to nothing. Here we're talking about how efficient the stove is at mixing wood-gas with air and how efficiently the stove can turn that mix into fire. This process seems to work best (in my horizontal feed) when the wood is packed in tightly. The air flows in and is forced to go around and through all of the wood, as the wood burns and the pile settles, more air goes directly over the top and less goes through the pile, reducing it's ability to mix completely. I can (and often do) go outside and with my nose, judge when the wood needs an adjustment. You can smell a difference even before any visible smoke is exiting the chimney. I have noticed that while the stove in my house seems to need adjustment less often than (say) the one in my shower house (standard down feed, smaller box, smaller wood, burns down quicker) it will dwell in a less efficient mode for longer. There is a "period" of burn for a load of wood, early in the period when wood is placed in the stove (even a hot stove) there is a little ramp up time where the wood is heating and beginning to burn, there will be some smoke and poor efficiency. Then there is a period of clean burning, the wood is in the right place, air is flowing through, mixing is optimal, clear sailing. Towards the end, the fire will disarrange, airflow and mixing will be hampered, the exhaust will dirty up again, smoke a little and finally (if not re-stoked) die out. With a down-feed, the middle, clear sailing time seems to be rather extended and you don't see that final, dirtier ramp down till almost the end. In my horizontal feed, that dirtier end bit can sometimes be the extended period and the thing will need an adjustment to finish it's burn cleanly. I hope that was understandable. Once again, don't get me wrong, I LOVE my stove.. It is rather convenient to feed the thing regular cord-wood rather than smaller stuff, it's nice that I can pack in a whole lot more wood in one setting and there is less fiddling with the fire in general.. There are trade-offs. As to the specifics of bells, Peterberg is FAR better qualified to go into that than me. Speaking of bells and Russian sources, have you been to Kuznetsov's site?
|
|
|
Post by peterberg on Mar 1, 2012 13:34:48 GMT -8
As to the specifics of bells, Peterberg is FAR better qualified to go into that than me. I would think Donkey is right, the double riser set-up doesn't look good. You know, a stove which is designed to do all won't be excellent in any of the goals you're after. As for bells, the first one I've built had an internal surface area of 9500 square inch, not counting the bottom of it. Very high and narrow with a small footprint. The rocket inside could only burn some 4 pounds of fuel at any given time. Nearly all the produced heat could be stored by the bell around it. As a consequence, the efficiency of that design has been very high, sometimes as high as 95%. The rocket itself has been built as a 7" system. And yes, I do posses some fancy test gear made by Testo.
|
|
berko
New Member
Posts: 16
|
Post by berko on Mar 1, 2012 23:51:59 GMT -8
I hope that was understandable. Once again, don't get me wrong, I LOVE my stove.. It is rather convenient to feed the thing regular cord-wood rather than smaller stuff, it's nice that I can pack in a whole lot more wood in one setting and there is less fiddling with the fire in general.. There are trade-offs. Yes, it was logical and edifying. Thanks again Donkey No. My friend found an old original russian book and he is scanning now. I haven't seen it, but i'm hoping
|
|
berko
New Member
Posts: 16
|
Post by berko on Mar 2, 2012 0:40:18 GMT -8
I would think Donkey is right, the double riser set-up doesn't look good. First of all thanks your reply. I think there are some misunderstanding. Maybe i was ambiguous. I have 2 riser but at the same time i use either of them . When i would like to heat, i close heater 1 and open heater 2. I fill burn tube and burn it. Another time, when i would like to cook i close riser 2 and open riser 1. Can you tell me something about the temperature of stack gas (exit stack gas) ? And something about gap between the wall of bell and heat riser ? And gap between the top of riser and top of bell ? Built your bell from bricks (Brick on edge) ? I have many questons, but i hope so my questions isn't too tiresome
|
|