Joel Hollingsworth wrote:My understanding is founded in theory, not practice, so take this with a grain of salt:
The barrel serves partly to mix the combustion gasses and cause a secondary burn, so...
I do believe that the basics of the "rocket" burner can be made to work here, and work well.
I may have wandered a bit earlier: to some important points:
* Use the vertical insulated burn tube to consume the fuel. With enough air inlet (and some way to control it perhaps) and a tall burn tube, you probably don't need to concern yourself with secondary burn or mixing of fuel/air (it's done in the tall tube).
* go from the top of this, directly to your "black radiator" horizontal run across the ceiling.
This takes the maximum released energy and puts it right into the skin of the HX pipe. Suggest to minimize the distance between the burn tube top and the radiator pipe, if you wish to direct the released heat using your parabolic reflector, otherwise it will furiously warm up the air right there, and whatever is nearest the pipe.
* The "primer" (small heat release at the beginnning of the final run up & out) is a good idea. With your electric fan, it might not be needed. WIth a tall "Rocket" burn tube, the fan might only be needed to keep the draft at start-up, until it heats up the guts.
I maintain that the barrel is not needed. It is the heat exchanger of choice for that design: a flat space at the top of the burn for some cooking utility, and it re-directs the flow back down to the lower exhaust into the cob mass horizontal run. This is the heat exhanger for the "mass heater".
You aren't using this. You're using immediate heat, from the exhaust, right into the room air.
I do not know what success you will have with your controlled stack burn, and self-feeding of the fuel from the stack into the burn area at the base of the insulated vertical burn tube.
You may very well be the one to innovate this with a "rocket stove".
All we've seen in the literature is the "L" and the "J" with their respective methods (either the continuous manual feed into the lower part of the "L", the other the self feeding, bottom burning sticks of the "J".
If this clears it up a bit:
All that makes it a "rocket" is the insulated vertical burn chamber. This creates a fast moving energetic colllumn of air, by maximizing the time the 3 sides of the fire trangle are present in the most favorable conditions.
I ignored fuel input and everything upstream.. This might very well sit above the floor: you won't need much more than 40" of vertical insulated burn tube for a complete combustion and very energetic flame.
At the top, it'll be furiously hot. over-build as necessary.
Erica Wisner wrote:
They used to sell stove pipe in giant S-curves and other fancy shapes. History responded with a lot of deadly chimney fires. Steel tends to go "sproing" when heated, especially when heated unevenly by burning creosote. Current building code limits stovepipe lengths to about 6' (? maybe 8'?) so there are de facto expansion joints in any long run; and manufacturers' instructions usually emphasize vertical or near-vertical installation, with straps and clearances from combustibles.
Theoretically creosote shouldn't be a problem with clean-burning stove designs. But theoretically we never burn wet wood either, nor "damp down" our fires and smolder them through the night.
Well you gave me a bit of help with this. I was still going to build a test version of this but from all the posts I was starting to think this might not work. But I'm sorta of hard headed and still will build this test version. I have read about this type of stove and many think its the only stove to use.
There may be many modifications that I will have to do when building this to make it work but that is the fun of it.
Ken, it can be pretty simple. Build the J-tube rocket part, you get lots of heat and clean combustion. Replace the thermal mass part with your cast iron radiative heater. It will work, as I've said before faster heat-up and cool down but less staying power so you either will need to feed the fire more often or accept larger temperature swings. Not a big deal. You may also need fans to move the heat around a bit, much hotter closer to the stove.
Erica Wisner wrote:
J-tube rocket stoves don't work with an inside diameter less than 4" - it's been tried, and they just plug up from the viscosity of the air itself in that small a tube. You might be able to do it with fans, but the burn is likely to be dirty and unreliable. Pocket rockets do OK at 4" with a short, fast exhaust (not a round-the-room adventure).