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Post by pyrophile on Jul 5, 2014 16:01:31 GMT -8
I agree with rising convection but I think that it doesn't rises with the square as radiation does and also that the shape can enhance or reduce it. I don't ignore convection but I try to minimise it and in the other hand to maximise the effects of radiation.
But it is very possible that reality differs with my belief! I haven't experience enough, nor kwnoledge.
About the single bell idea, I consider that there is bell effect ABOVE the heat riser as long as the temperature of the metal walls are below the temperature of the exhaust gases. This happens -I think- in all bells like bread ovens, for instance or water tank (connected for example to solar panels)where water insides the tank stratifies as long as the incomming water is hotter than the water in the tank. That is the principe of the bell, there must be something I miss in your reasoning. I would like to understand better.
About single or double bell, I wanted to keep the stove simple and not enormous. I didn't find a bigger bell than this water tank.
With bricks, It is easier to build larger stove (as I did with the rectangular rocket stove shown above). But power falls!
What you say about the exaust hole makes sense to me and if russian or Chernov's bells are against the floor, they have bigger size than "necessary". That's what I do but now I understand the reason!
If you have time, Peter, could you explain more what you mean with the sentence "Actually, this single bell idea with the combustion chamber inside it isn't acting as a bell pur sang. Simply because of the constant feeding with hot gases stratifying won't occur"?
Thanks for sharing and giving time
Have a nice day (everybody)!
Benoit
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Post by peterberg on Jul 6, 2014 8:12:17 GMT -8
By stratifying, I mean the phenomenon that the hot gases in the bell are built up in layers. Hottest at the top, every next layer down is lower in temperature. Obviously, an enclosed space where gases are spewed in by the riser at high velocity all the gases are mingling all the time. See it as a fountain inside the bell, rising straght up in the middle and curling down against the top and forming an umbrella of fire which goes down along the sides. This is what happened inside my three-barrel model, the space above the riser's end is about 100 cm. When the burn is over however, and the air inlets are closed gases come at a standstill inside so the hottest air will rise to the top.
In a way, this is what in a water boiler tank will occur. Gases are mingling easier and currents move faster than in water so it's the same principle but that is as far as it goes.
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Post by independentenergy on Jul 9, 2014 3:33:17 GMT -8
hello guys,
I reflected on the situation in a double bell rocket stove, the goal is to have the bell heated more evenly, but with a rocket stove, having high heat riser remains concentrated at the head of the people, by adopting a double bell the situation does not improve much, it decreases the ISA but still leaving at least 30cm between the riser and the top of the bell before you arrive, however, to have a stove with high heat and high total that primarily affects people's heads and the ceiling .
So I was raised another question, but you can get this with a rocket stove? or have the heat concentrated in an area that affects the body of the people?
All these situations I always return to the hypothesis of the "broken riser" of matthewwalker
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Post by peterberg on Jul 9, 2014 7:42:49 GMT -8
So I was raised another question, but you can get this with a rocket stove? or have the heat concentrated in an area that affects the body of the people? A double bell system could look like this:  The lower bell sports an upstream channel inside at the back, the upper bell at the front. Just underneath the second upstream channel there's a bypass in the top of the first bell. The firebox inside is one of my experiments described in this thread. This could be very well a batch box rocket now. High heat is extracted and transmitted by the first bell, additionaly more heat is extracted by the second bell. |
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Post by independentenergy on Jul 9, 2014 8:23:16 GMT -8
I had seen that post, you have installed the stove sometime?
The box is very complex.
How big is the height of the first bell?
thank you
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Post by peterberg on Jul 9, 2014 11:36:08 GMT -8
No, this stove has been an experiment only. But the construction of the bells isn't complex at all, in my opinion.
This has been a 6" system, more or less comparable to the later batch boxes. Height of the first bell no more than 5'4".
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Post by pyrophile on Jul 9, 2014 13:20:02 GMT -8
Yes Peter, I totally share your description of bell system. In fact, the stove with vertical water tank was my first batch box rocket stove and I didn't suppose that flames would touch the top of the bell! It was not what I wanted as I wanted to have free space above the heat riser, with a combustion ending in the riser, not above! And I agree that bell effect is much less. That is also why I wanted a quite large cylinder, so that there could be convection in such a place. I think that there is, as there is also convection (then stratification) in a bread oven if there is a not too big fire. It was (still is) a metal stove, then a cylindrical shape was the easyest to find. For metal, I would not use anymore such a cylinder but a rectangular shape as I did with the concrete J rocket stove shown above. For example, I found for a very different project a 1500 or 1800 liters gasoil tank.  Or this one for a cylindrical shape !  In a big cylinder, there can be stratification! For a big room! And double bell! I agree with Independentenergy that a batch box rocket reaches quickly height limits (human head height). The advantage with a rectangular shape is that there is a lot of convection , then stratification because there is a lot of free space. As I said, I prefer to avoid to build one bell upon another one but rather two bells side by side or even a single bell quite large (the one in concrete and brick) to stay at head 's height. The second bell must have somme height to work well, that is to absorb all the energy produced for one full day. Another problem with 2 bells one upon the other one is that you may have to insulate beetween the bells because the top of the first bell is quite hot.Then the bottom of the second bell becomes warm whereas it should be the coldest part of the stove. This appears mainly with stoves fired each day, once a day (then a big fire, every day). There is also the possibility of one bell surrounded by another bell. Benoit |
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Post by satamax on Jul 9, 2014 20:38:15 GMT -8
Benoit, i ran some calculations last year or the year before. With home heating oil, the good ones are around 1000L 1200L for a six incher. A thyousand liter is about 5m² without accounting for the floor. Near ideal dimensions. The next shape i'd love to try heatkit.com/research/2009/lopez-rocket.htmAnd since you're in france. Another intresting one, in one of our old houses, would be to use a doorway in a big interior structural wall. In my flat, for example, the wall behind me is about 60 thick. Fitted with a rocket in the doorway, one metal plate affixed to the front, one to the back, and you have a nice bell and mass combination. One advantage of mass, is that it doesn't heat up more near the top. Heat distributes more evenly, when there's no convection movements. |
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Post by pyrophile on Jul 21, 2014 11:50:48 GMT -8
Satamax Yes, a place beetween two walls would be great! In Britany where I live, walls are 60 to 80 cm thick, but earthen made or stone made! No possibility! That's why I made a large rocket "wall" with concrete blocks and bricks, earthen plastered, a bit similar to the you've shown :  Do you know David Szumilo in Alps who build stoves and plays with fire? Benoit |
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Post by satamax on Jul 21, 2014 12:01:46 GMT -8
Nope, Benoit, never heard of him, tho i'll check! An idea which crossed my mind, instead of using a double wall as shown in the lopez rocket link. Another option would be to use one of thoses doorways in thoses thick walls, to make a bell, by bolting a metal plate to the front and back, and inserting a rocket in there, with the feed outside. Then route to the chimney. Or you could also close the bell with bricks too. Strawbale insulation on the perimeter of the house. A "doorway rocket" near the center, and that would give a rather efficient heating system  |
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Post by pyrophile on Jul 21, 2014 14:11:59 GMT -8
Satamax
Don't you think that those metal plates will be way too hot and the wall not heating at all? (if I understood well!)
Benoit
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Post by satamax on Jul 22, 2014 9:35:52 GMT -8
Satamax Don't you think that those metal plates will be way too hot and the wall not heating at all? (if I understood well!) Benoit Well, they wouldn't go any higher than a barrel, i'd think. And since the temp inside the "bell" should be the same or thereabouts as the plates, i think the wall should heat! I'm imagining two big metal plates, with a metal flat frame riveted with big forged rivets !D A bit of old industrial style, mixed with modern technology of the rocket! Instant steampunk! If made well, one could pretend the house has always been heated that way |
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Post by pyrophile on Jul 22, 2014 23:28:20 GMT -8
Sorry I was not clear, I will explain what I meant another way :
If you have those two big conductive metal plates, you will dissipate most of your power during firing as you will have at least twice the radiating surface of one barrel combined to a bigger bell effect (that doesn't exist in the barrel and allows to have heat for the bench).
I think also that the bell would be much too small.
And the walls on sides would not get so much heat (little exchange at this place). And would radiate it at very low rate. The wall above the bell would be heated a bit more but no so much because of the size of the bell (too little). And where would it radiate? At what temperature (how many tons storing a few Kwh?)
In my opinion, very litte heat would be stored and a lot lost.
But I may be wrong and other may have another opinion.
Benoit
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Post by satamax on Jul 23, 2014 9:59:33 GMT -8
Benoit,
let say, 80 wide doorway and 60 thick wall. 210cm high doorway.
0.6 x 2.1 x2 = 2.52m²
0.8 x 2.1 x 2 = 3.36m²
0.8 x 0.6 =0.48m²
So you have a total of 6.36m² of isa. That would be good enough for a 6 incher!
You have spot on 3m² of exchange surface with mass.
And 3.36m² exchange surface with metal for quick heat. Ok, it's a bit much.
A barrel is 1.87m² of isa.
Let's cut back the rear plate, and replace it with bricks, a double layer, for example. And you have a fair bit of mass alltogether, with 1.68m² of radiating steel.
Still not convinced? That in a little house, in a central wall, with a strawbale insulated perimeter; would be near ideal!
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Post by pyrophile on Jul 28, 2014 11:35:36 GMT -8
Satamax, I don't want you to believe that I try to think the opposite of what you think.
I still am not convinced, even in a rather little house very well insulated. Maybe you are right, I have no plans to examinate.
I think that the only parts to radiate will be the two "doors" full of bricks, let say. Each "door" is about 1.7 m2. If your room is really little, it can be OK but 1.7m2 is very little!
I would have no hope for the other sides of the stove (small sides made by the thickness of the walls and top).
There are many things to say and I don't know where to begin...
With plans (in french : "des plans de la maisons"), indication of materials, insulation, role of the rooms (sleeping room, kitchen, desk...), I could help more(if I can help).7
Once more, I lack information and I may be wrong.
Regards
Benoit
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