|
|
Post by erikweaver on Nov 19, 2014 16:19:38 GMT -8
Is turbulence in the fire riser helpful, for mixing the gases and helping them to burn more completely?
If so, has anyone tried making alternate courses of the fire riser slightly proud (sticking out) relative to the course above and below it?
It seems like that ought to disrupt the laminar flow up the fire riser. But maybe that's too late to contribute to a more complete burn?
It seems like another way to do this, would be to slightly twist each course, making an uneven edge every course, again disrupting the laminar flow.
I don't have a gas tester, so I wouldn't be able to tell if this would do anything worth while or not. So I'm curious if anyone else has tried something along these lines.
A similar question could be asked about the burn chamber, but given the air flow seems to be along the roof of the burn chamber, I'm assuming peterberg's trip wire and p-channel are the way to go there.
|
|
|
|
Post by ericvw on Nov 19, 2014 17:25:20 GMT -8
Hello erikweaver and welcome from a similarly named (eriC) member,
Is it safe to assume ur building a J? Peterberg has described before about a SMOOTH surface in the heat riser, but he will also tell some to try it for the knowledge and experience! I'm pretty sure he has said introducing drag in the riser is straight out a bad idea.... An OLD house you say? How's your structural support looking, even at 50 lbs/ sq ft?
Anxious to see what you come up with,
Eric VW
|
|
|
|
Post by patamos on Nov 19, 2014 20:40:01 GMT -8
See Peter Berg's posts on 'kick tail' at the bottom back of the heat riser.
Also, dragon heaters.com has a page showing clear diagrams.
|
|
|
|
Post by PNW Dave on Nov 19, 2014 22:44:40 GMT -8
I came across this video a while ago, seems like the effect would be beneficial in a riser-
|
|
|
|
Post by Daryl on Nov 20, 2014 1:46:46 GMT -8
Many, many stoves have a second combustion chamber. The more research I do, the more I find this is the case. The second combustion chambers are located on the top or bottom of the burn box. They are also called reburn chambers. The riser can be considered a second combustion chamber. It is set up exactly as one would be...only sideways.
There are examples on the internet of shapes, metal objects, and air being added in the riser (or second combustion chamber).
Yes, there shouldn't be a drag to the flow and a good balance has to be acquired. But according to the multiple sources of fire science that I have read up on, there will be residual elements left over from the main chamber. It seems to make sense that a tweak to the riser may help.
|
|
|
|
Post by erikweaver on Nov 20, 2014 8:16:09 GMT -8
Hello erikweaver and welcome from a similarly named (eriC) member, Is it safe to assume ur building a J? Peterberg has described before about a SMOOTH surface in the heat riser, but he will also tell some to try it for the knowledge and experience! I'm pretty sure he has said introducing drag in the riser is straight out a bad idea.... An OLD house you say? How's your structural support looking, even at 50 lbs/ sq ft? Anxious to see what you come up with, Eric VW I guess "old" is a relative term. My house was built in 1947 if I recall correctly; something on that order anyway, so about 67 years ago. And it has some quirks I've found over the years, so I try not to assume too much about parts I haven't actually looked at. Areas of the floor I have seen in adjacent rooms to the living room use 2x10s for the floor joists and spaced between 14 and 16 inches on center. I haven't yet looked up the weight rating for those dimensions. The span is 18-feet. I think I could brace the basement with 4x4's post and beam, and then build on the living room floor safely. But it would be a real mess, because that area of the basement is a finished living space, and not an area in which I really want to tear the ceiling off. My other option for building the RMH is to enclose the front porch, which is concrete, and build on that. I'm not concerned about weight there, although I would need to insulate the concrete from excessive heat, of course. In many ways, this would be a lot easier space in which to build. The living room and proposed enclosed porch both are all the east side of the house, which is my leeward side, as most wind comes from the west and north, and most storms come in from the west. So I might be able to get away with a floor level exhaust. On the other hand, this is not a "baggie" style air-tight home! It does have air movement. So I do have some concern about proper draft. (I plan on testing this.) My building project is a two-stage plan. This winter I would like to just build the basic J-style rocket stove and barrel. If I can keep the weight down, I can install that in my living room for the winter, and exhaust out the window at the wall shared with the front porch, using the sneaky "dryer exhaust" idea (and testing the draft at that location). J-style rocket stove is the basic configuration I'm planning for the full RMH, which I plan to build next summer/fall (2015). At a later date, perhaps 2016 or 17, I would enjoy trying a batch-style system, but that would be a later project. So that's the background info. As to just trying alternate proud courses of brick in the riser, or the twisted option, my problem is that I don't know how I would test the results. If I cannot test the results, I think I just have to take my best guess and build it. This is why I was hoping someone has already tried and tested this idea. I'm hoping for an interesting discussion, or links to experiments and test results. |
|
|
|
Post by erikweaver on Nov 20, 2014 8:35:54 GMT -8
See Peter Berg's posts on 'kick tail' at the bottom back of the heat riser. Also, dragon heaters.com has a page showing clear diagrams. Yes, I've read Peter's posts and found them extremely interesting. And Dragon does have nice images of the design; for that matter, I like their solution to piping the secondary air intake around to the p-channel. I might weld up something along those lines for the final install, although I may brick or cob over it, as I prefer that look to metal. My thought was about adding additional "kicks" going up the vertical fire riser. If Peter addresses that question, I must have missed it; ericvw thought he addressed it too. |
|
|
|
Post by erikweaver on Nov 20, 2014 8:43:49 GMT -8
I came across this video a while ago, seems like the effect would be beneficial in a riser- Yes, that is pretty much what I was imagining happening. Slower rise, and greater mixing. Seems like it would mix the gases better, and help with the burn. On the other hand, I seem to recall there is a limit to this, beyond which it is no longer a benefit (the details I do not recall, nor did I find them when I searched the threads, which is why I started this thread). Did Peter Berg say that the temperatures were too low in the riser, and that the mixing had to take place earlier in the burn to be effective? Maybe I read that somewhere else? Someone was talking about the temperatures and the timing of the heat and gas mixture as both being important variables for a complete burn. You can't just add turbulence and heat wherever you want and expect the same results. But I've read so much these past few weeks, my memory is experiencing turbulence! heheh |
|
|
|
Post by erikweaver on Nov 20, 2014 8:47:08 GMT -8
Many, many stoves have a second combustion chamber. The more research I do, the more I find this is the case. The second combustion chambers are located on the top or bottom of the burn box. They are also called reburn chambers. The riser can be considered a second combustion chamber. It is set up exactly as one would be...only sideways. There are examples on the internet of shapes, metal objects, and air being added in the riser (or second combustion chamber). Yes, there shouldn't be a drag to the flow and a good balance has to be acquired. But according to the multiple sources of fire science that I have read up on, there will be residual elements left over from the main chamber. It seems to make sense that a tweak to the riser may help. Any idea how one would test such changes to the fire riser without access to a gas analyzer? Is simply reading a temperature gauge and sniffing the air going to be sufficient? |
|
|
|
Post by Daryl on Nov 20, 2014 10:07:39 GMT -8
Sometimes a tiny change can be noticed. Have you built one yet? Otherwise, some form of temperature gauge.
|
|
|
|
Post by PNW Dave on Nov 20, 2014 13:15:08 GMT -8
Yes, that is pretty much what I was imagining happening. Slower rise, and greater mixing. Seems like it would mix the gases better, and help with the burn. On the other hand, I seem to recall there is a limit to this, beyond which it is no longer a benefit (the details I do not recall, nor did I find them when I searched the threads, which is why I started this thread). Did Peter Berg say that the temperatures were too low in the riser, and that the mixing had to take place earlier in the burn to be effective? Maybe I read that somewhere else? Someone was talking about the temperatures and the timing of the heat and gas mixture as both being important variables for a complete burn. You can't just add turbulence and heat wherever you want and expect the same results. But I've read so much these past few weeks, my memory is experiencing turbulence! heheh Well, my thought was more about pure speed in the riser as opposed to mixing and burning in the riser. I think that it is ideal to have the vast majority of combustion take place in the burn tunnel (referring to J-tube, not batch box of course) but that may need to be qualified by an expert. I think Peter's work with the P-channel, tripwire and kick tail pretty much takes care of the mixing and burn aspects. I also read so much that I suffer from "memory turbulence" lol. |
|
|
|
Post by wiscojames on Nov 20, 2014 13:18:04 GMT -8
'memory turbulence' - you haven't copyrighted that have you? I'd like to start using it in my work.
|
|
|
|
Post by DCish on Nov 20, 2014 13:53:27 GMT -8
If I were to try this I think I would try some version of Peterberg's trip wire where it is a ramp that the gasses then fall off of. That would give less friction than a full proud brick. And I'd probably try one ring of this at some point up the riser after I surmise that the turbulence from the burn tunnel to heat riser transition has settled into laminar flow, though I do not know where to guess that that might happen. I would fear that alternating proud courses would give significant friction that would rob the system of some of the power given by the riser, which would then have to be compensated for by, say, a taller final chimney or hotter exhaust temps to give greater draft.
Also keep in mind that the heated envelope of your house (1 or 2 stories?) will act as a chimney trying to draw air into the house. Your stove and chimney combination will have to generate enough power to overcome this force to get air to exit your flue rather than be drawn into the house backward through your stove.
|
|
|
|
Post by erikweaver on Nov 21, 2014 8:58:01 GMT -8
'memory turbulence' - you haven't copyrighted that have you? I'd like to start using it in my work. heheh, feel free to use the phrase if you like |
|
|
|
Post by erikweaver on Nov 21, 2014 9:10:08 GMT -8
Sometimes a tiny change can be noticed. Have you built one yet? Otherwise, some form of temperature gauge. No, not intentionally. Although the dry stacked columns I have been experimenting with are not perfectly smooth, of course. The most recent one, for example, had about a 1/8 to 1/4 offset in the first course above the "roof line" of the burn chamber. If I were to try to figure it out with temperature readings, I think I'd be inclined to want a series of thermocouplers set into the riser, probably every course, so I could establish a heat profile. Then I'd begin testing alterations. However, I'm just working with a few analogue thermometers right now, primarily using them to get an idea of the temperature rise and fall around the core (to help determine insulation needs for the in-home temporary rocket stove/barrel this winter). I suppose I could however, re-stack the fire riser and try the slight twist all the way up, just to see if I notice any change for the next test. |
|
