|
Post by Jura on Oct 25, 2017 3:19:14 GMT -8
I'd like a shorter riser so i can cook. My concern is will the short riser 4-8B have enough power and velocity to push the gasses trough a massive bench (without bypass)... Have a look at shilo's realizations @ his facebook profile. Unfortunately he hardly ever responds to private msgs
|
|
|
scandal
Oct 26, 2017 7:22:32 GMT -8
Post by byronc on Oct 26, 2017 7:22:32 GMT -8
|
|
|
scandal
Oct 26, 2017 12:11:56 GMT -8
Post by Orange on Oct 26, 2017 12:11:56 GMT -8
I'd like a shorter riser so i can cook. My concern is will the short riser 4-8B have enough power and velocity to push the gasses trough a massive bench (without bypass)... Have a look at shilo's realizations @ his facebook profile. Unfortunately he hardly ever responds to private msgs beautiful work, he has riserless models with bench so I guess 4B is working. Could not figure if he uses bypass or not.
|
|
|
Post by DCish on Oct 26, 2017 18:10:58 GMT -8
Byron, thanks for posting that link, I wouldn't have known about that thread otherwise!
Orange, some time ago I stopped finding it useful to think of the after-port area as the "heat riser." A post by Donkey years ago presented the math that illustrates how much draft is induced by a very hot, very short "riser" vs a much cooler, but longer chimney. It became very clear to me that a "proper" chimney is really where it makes sense to turn for reliable draft. At that point the "riser" can be oriented in any direction, and is now in my mind just a "secondary burn chamber" or "afterburner." Work by Shilo, Matt, Peter, and my own tinkering confirms this. The critical element seems to be using a 90* turn to induce turbulence as quickly as possible following the port and introduction of secondary air. However, if someone were to find a way to introduce the required mixing without using a 90* turn, I am sure there could be design flexibility there as well. Of course, that would take lots of imagining and testing to work out. The port plus a 90* turn into a "system size" expansion area is such a dead simply way to achieve reliable mixing, though, that I haven't seen anyone here take up the exploration of an alternate turbulator. Walker's design is probably the furthest departure in that it more or less uses a longer, port-sized "tunnel" with a 90* turn in it, followed by an expansion chamber, then a 90* shift to vertical. He gets great testo numbers, so there must be good mixing happening. Whether most of this is due to the 90* turn in the tunnel, or the expansion chamber, or what could presumably be teased out of one was so inclined. However, the port + 90* turn into an expansion chamber is a super-simple, super-reliable mechanism with great flexibility of design.
|
|
|
Post by Jura on Oct 27, 2017 0:20:13 GMT -8
beautiful work, he has riserless models with bench so I guess 4B is working. Could not figure if he uses bypass or not. It is one of the question I also paid him, but it seems to me that I saw one applied in one of the films on his youtube channel or those videos on facebook
|
|
|
scandal
Oct 27, 2017 12:55:12 GMT -8
Post by Orange on Oct 27, 2017 12:55:12 GMT -8
I'm just concerned because "back in the days" of j-tubes, flue pipes and elbows shortening the riser would bring smoke back. I wonder why bells haven't been "invented" earlier, its not only more efficient but easier to build and cheaper.
|
|
|
Post by pyrophile on Oct 27, 2017 14:23:33 GMT -8
Bells are one hundred years old but are better know (a bit!) in Russia where they were developped during the 20th century for industrial ovens using wood (at the begining) and then coal . Stoves could also be made with bells,and factories made some kinds of kits. Bells are not so easy to "calculate".
Benoit
|
|
|
scandal
Oct 30, 2017 9:09:44 GMT -8
Post by Orange on Oct 30, 2017 9:09:44 GMT -8
yea, I think people forgot about the bells.
with the riserless heaters I guess it is because of insulating materials that they have clean burning so they don't need long risers for complete combustion.
|
|
|
Post by DCish on Oct 30, 2017 17:49:55 GMT -8
yea, I think people forgot about the bells. with the riserless heaters I guess it is because of insulating materials that they have clean burning so they don't need long risers for complete combustion. Orange, a riser must also be insulated in order to work. The point of the riser, if you read Ianto Evans' book, is three-fold. The first purpose is to serve as an insulated turbulator to mix the gasses (bottom of riser). The second purpose is to provide an extended, highly insulated path for the mixed gasses to fully combust in before the next stove elements begin harvesting heat. The third function is to get some draft going by having a crazy-hot internal "chimney" (hence the name "riser") followed by a quick-cooling area (the barrel) where the gasses lose heat quickly, thus being less bouyant, and falling more readily in contrast to the super-hot gases in the riser. The thing is, when you do the math, the actual amount of draft produced by this effect is rather small. It is far more powerful and reliable to just add a few feet of chimney at the end. By doing this, you no longer need the third function of the "riser," thus it no longer needs to be vertical -- draft is being provided by a regular chimney at the end of the system. Leaving about 260ºF of heat or so in the chimney serves two purposes. It ensures enough reliable draft to run the system, and it is hot enough to ensure there isn't dangerous creosote formation (creosote precipitating out at about 250ºF - feel free to confirm that number. I re-checked it just now via an old Kentucky Dept of Energy document - I think it's right, but I'm open to correction). So, as long as you produce the right amount of mixing of secondary air and provide a highly insulated area for it to complete combustion in, it can go up, to the side, or even theoretically down, if you have the need and inclination (proof of concept is the commercial twinfire stove where draft is established, then a lever is flipped, re-routing gases down for secondary burn). The trick is, finding just the right way to induce turbulence, and the right conditions for the secondary burn requires lots of tinkering and testing. Enter here the work of Peter, Matthew, and others who own flue gas analyzers and who spend time testing various configurations until the find one with good results that is reliably and simply reproducible. It's not that some other configuration wouldn't work, it's just that it might require lots of refining to get right.
|
|
|
Post by Orange on Oct 31, 2017 4:19:24 GMT -8
thanks DC dor the explanation. As for the exit temps, Peter said around 75C (167F) is excellent. I guess because the heat extraction is maximal without having condensation and creosote doesn't form on a clean burn.
|
|
|
Post by pinhead on Oct 31, 2017 6:19:35 GMT -8
I've run my batch rocket with chimney temps as low as 85°F without any hint of performance degradation and no creosote formation.
This is after the core and heat riser have both been thoroughly heated - enough to burn cleanly with reduced draft.
I'm able to get away with this due to the inclusion of a bell bypass, in which the "warm-up" phase is accelerated with high(er) chimney temps for additional draft. 160°F seems to be a really good temperature to maintain during warm-up and, if no bypass is installed, also a good temperature to maintain throughout operation of the RMH.
|
|
|
scandal
Nov 15, 2017 10:32:21 GMT -8
Post by Jura on Nov 15, 2017 10:32:21 GMT -8
I'd like a shorter riser so i can cook. My concern is will the short riser 4-8B have enough power and velocity to push the gasses trough a massive bench (without bypass)... I watched all the shilos and adiels films and in all new realisations they used a bypass. With such long benches and the curved flow channels there must be a really good chimney to offer smokeless startup.
|
|
|
scandal
Nov 15, 2017 15:08:42 GMT -8
Post by Orange on Nov 15, 2017 15:08:42 GMT -8
I noticed it too. You can check out my build, I'll probably but it further in the bell.
|
|
|
Post by shilo on Jan 31, 2018 2:37:36 GMT -8
sorry about my disappearing if you have no tall riser than you need a stronger draft. you can get it with a better chimney in a better location or with a hotter chimney or with a better weather or with the aid of electricity. I'm strongly recommend to use a bypass and we install one to any customer.
|
|
|
scandal
Jan 31, 2018 3:11:50 GMT -8
Post by Jura on Jan 31, 2018 3:11:50 GMT -8
sorry about my disappearing Hurray! Welcome back Thanks for answering. I was asking you even via facebook whether there are any hidden construction tricks, hacks or differences (in size, positioning, others ) in your setup in comparison to the standard batchbox. - - In some post you say there is no any difference. Would you confirm it now?
- - What would be the max bench piping length for a 15 cm system with
2 -90 deg and 1 -180 degree turns.? - - What diameter of it would you advise? (the chimney is 15 cm in diameter )
|
|