dvawolk
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DSR2 125mm open system (actual project)
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Post by dvawolk on Oct 30, 2013 4:06:34 GMT -8
Hi, all!
Has there already been a talk of calculating approximate ISA for batchbox stoves? There has already been a thread that shows spreadsheet of calculating batchbox dimensions... But not ISA?
If we talk about masonry heaters, bell type. What should one take into account to calculate the ISA of a single bell?
-the weight of wood of a single batch (energy) -the speed of one burn (this is usually 40minutes + coal phase) anything else?
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dvawolk
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DSR2 125mm open system (actual project)
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Post by dvawolk on Oct 31, 2013 5:44:28 GMT -8
I was thinking. Is it enough to make the following simple conclusion: If I burn 6kg in one batcbox and I use 6 sq. meters,then for half the size of batcbox, I need half the surface of ISA?!
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Post by satamax on Oct 31, 2013 8:53:00 GMT -8
Klemen, i'd say, make your batch box test tube thingy. Then connect that to two barrels, like Peter's workshop stove. Then make Another bell etc, till you smoke yourself Then you'll know you have reached the limit
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dvawolk
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DSR2 125mm open system (actual project)
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Post by dvawolk on Oct 31, 2013 10:28:23 GMT -8
This will be the second option... :-)... But it is useful to predict when will I smoke myself out. :-)
But I have just read in the 4inch batcbox thread something useful... ISA between different sizes is connected with squared proportion (That was Peter's reply) So 6 inch compared to 4inch is 6/4=1.5 and for the ISA it is (6/4) squared... that is 2.25...
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Post by lincsoldbird on Oct 31, 2013 12:29:41 GMT -8
It will depend on what the bell is made from and how quick it can remove heat.
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dvawolk
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DSR2 125mm open system (actual project)
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Post by dvawolk on Oct 31, 2013 12:32:04 GMT -8
I agree. But if comparing the same material, there should be some proportions...
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Post by Robert on Oct 31, 2013 13:36:15 GMT -8
Nice thread Klemen. I would also would like to know the formula. Mostlikely i will be building some batch-box one bell type of a stove... bell made of bricks... and i would not like to be smoked by any reason... when i visited Peter in Nl he told me that the safe area for the bell for 6incher would be 5,5 sq meter.
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dvawolk
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DSR2 125mm open system (actual project)
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Post by dvawolk on Nov 1, 2013 0:41:54 GMT -8
Premakultura, I agree with 5 sq. Meters as a reliable ISA for a masonry batcbox, 6". I you look at my project thread, second post,i try to explain how to fine tube the ISA, after the bell has already been built..
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Post by pyrophile on Nov 3, 2013 12:07:07 GMT -8
I am afraid (but I may be wrong) that it is quite difficult to calculate.
A few things participate as the conductivity of the materials used in the stove, but also their different thicknesses (in my mass stoves, the heat accumulated in a bell may cross a flat (10 cm)or standing (5 cm) fired brick then a 10 cm flat earthen or fired brick (or concrete block) and then an eventual plaster. And when the stove is already warm, the exchange is less.
But the caracteristics of the house or of the room(s) are also very important. What about the insulation, the inertie, the materials and so on and so forth?
The experience plays a lot. I don't know how german or austrians stove masons do.
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dvawolk
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DSR2 125mm open system (actual project)
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Post by dvawolk on Nov 4, 2013 5:19:17 GMT -8
I agree that exact calculation would require many more information than practically available just for an approximate estimation.
I am asking about guessing approximate ISA for a system size of similar heaters (batcbox)... 6 inch is already known to be able to work with cca. 6sq. Meters.
There is a recent thread where Peter estimates ISA for 4 inch batcbox to be (6"/4")^2=1.5^2=2.25 times smaller to ISA of 6 inch batcbox... That is interesting to me. Although I would say that the proportions of the ISA should be derived from the volume of the batcbox chamber... Because in his tests of lengthening the batcbox chamber and keeping the system size,the exhaust temperature is higher, so larger ISA could be used... Estimation of ISA based on the volume of batcbox chamber would be: For 4" it is (6"/4")^3=1.5^3=3.38 times smaller compared to 6" batcbox. That is 1.8 sq.meters for 4inch batchbox(masonry material)..
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Cramer
Junior Member
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Post by Cramer on Dec 15, 2013 20:27:00 GMT -8
Okay, new here just today. A few minutes ago in fact. What the heck does the abbreviation ISA mean? Trying to learn something here but when technical abbreviations are not explained learning can be quite difficult.
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Post by peterberg on Dec 16, 2013 1:36:33 GMT -8
It's Internal Surface Area. Important for the combination of a rocket/bell combination. Too large surface area inside the bell will lead to a very low stack temperature, a wet chimney and inevitably stalling of the stove. Stall is another term, this time out of the aircraft industry. When the speed of the plane becomes too low the wings doesn't produce lift anymore and the plane will drop down, vertically.
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Post by satamax on Dec 16, 2013 2:00:44 GMT -8
It's Internal Surface Area. Important for the combination of a rocket/bell combination. Too large surface area inside the bell will lead to a very low stack temperature, a wet chimney and inevitably stalling of the stove. Stall is another term, this time out of the aircraft industry. When the speed of the plane becomes too low the wings doesn't produce lift anymore and the plane will drop down, vertically. Peter, on the stalling side, if one could vent through the wall, at the bottom of the bell, temporarily, this wouldn't happen until the stack warms up? So bigger bells could be used? On a side note, I have that problem with the green machine. Tho, i can't vent outside realy, as my workshop is lower than the ground, so, when i vent through the window, smoke comes back inside flowing like water!
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Post by peterberg on Dec 16, 2013 4:41:51 GMT -8
I don't think that would work. In order to get the stove going, you do need chimney draft. Moreover, when the smoke is vented through the wall instead of the stack, how do you heat the stack then?
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Post by satamax on Dec 16, 2013 6:06:48 GMT -8
I don't think that would work. In order to get the stove going, you do need chimney draft. Moreover, when the smoke is vented through the wall instead of the stack, how do you heat the stack then? By having a bare pipe inside the bell? Well, let see what we agree on. In order to get the stove going, you need chimney draft? Well, i realy thought rockets were kind of self drawing, up to a certain extent. If we have a opening at the bottom in the side of the bell, which can be opened or closed, to evacuate cool gases to the outside world. Would that work? I would say yes. As long as there's no restrictions. It's like leaving a bare rocket in the outside world. Do we agree, this one draws? www.youtube.com/watch?v=dM-GbmlVGXo Then the hot gases heat up the bell, and replace the cooler ones? This in turn via conduction heats up the bell and the chimney stack. Ok, may be not fast enough. Having a plunger pipe in the bell, instead of a brick chimney or insulated pipe on the side of the bell owes to have faster heating capacities? Better yet, have a vane on top of the bell where the hot gases can be fed directly to the chimney stack, during the time it takes to warm up? This would prime the chimney faster. Then comes the relation between heat transfer capacity of the bell material, and it's radiating surface with the rest of the system. Radiation of the outside surface of the bell slows down with the decrease of the temperature diferential between it's surface and the surounding air. Then you reach a state when the mass of the bell , due to it's heat transfer capacity, it's heat storing capacity and it's radiating capacity is at near equilibrium. You can't charge up the mass anymore. The gases are in a sort of inside stasis, they stay in the bell, kinde of stored hot, pushing cooler ones out, but, the cooler ones aren't much cooler, since the bell can't take much more heat. So, that means that when we reach that state, it could be possible to charge another bell. If we do a cool exhaust at first, going out of the bell, we might be able to heat bigger a bell than we thought is possible originaly with a normal chimney stack. Which would be there, but start drawing only when the gases in it get hotter than the surounding air. The problem arises when we can't exhaust gases at bell floor level, and the walls of that bell take more of the leftover heat than is acceptable to power the chimney. That's when the bell is too big. But if we can cool the gases further and they exhaust at the bottom, going downwards, we can have a bigger bell. Or at least i think. I wonder if there would be another point where the gases would be cooler than the surounding air around the bell, at the bottom, and they would pull heat from the house. But i doubdt it. I went verbose there! Sorry.
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