Hello! Newbie here, lots of youtube time logged looking at RMH's.
Hey there. Welcome to the forum. I hope you'll be able to find some good info here on the boards to steer you in the right direction.
Unfortunately, the YouTube search results for "rocket stove" have only a tiny fraction of safe, sane
actual rocket stove builds, which are mostly drowned-out by the prodigious over-abundance of what can be more-accurately described as
rust-and-carbon-monoxide catalyzing structure-fire-precipitators.
One of the most important design principles behind the original, true J-tube or L-tube rocket stove (developed by Ianto Evans and Larry Winiarski) is combustion efficiency... specifically
efficiency in terms of clean, complete combustion, first and foremost with heat harvest happening AFTER clean combustion is completed; downstream of the heat riser.
Clean combustion cannot be achieved in a plain steel tube with the rocket stove's inherent natural-draft design. They have to be made of refractory materials, at least on the interior lining of the firebox and secondary burn chamber ["riser"], to reach clean wood combustion temperatures. ...Temperatures which would burn through unshielded mild steel (turning it to iron oxides) approximately as well as it would burn through the wood fed into the burn chamber... except that the steel tube robs the combustion zone of heat, putting that heat into the air too soon... long before the final combustion byproduct —carbon monoxide— can be cracked into CO2... which requires sustained burn temperatures well above 600ºC (1112ºF).
Aside from the dirty combustion, the steel will spall and rust-through extremely quickly due to the constricted fire-tunnel shape and rapid burn rates... usually breaching the tube wall at some unpredictably inconvenient moment, and in an inconvenient location— often while the stove is at peak operating temp and is weakest— suddenly putting the now-uncontained flame or exhaust gases (or both) into the room.... (
especially given that you're intentionally shooting for the condensation of corrosive pyrolysis compounds within that steel tube.)Sure, J- or L- steel tubes produce less visible smoke than open fires... but that's almost
more dangerous because you cannot see or smell carbon monoxide as its poisoning you.
K-shaped tubes are notorious for sending combustion byproducts and flame back up that 45º-angled feed. J- or L-shaped tubes made of refractories like rated firebrick or castable are vastly more reliable and safer.
...please,
please realize that what you're saying here is that you literally expect to be accumulating lots of unburned, highly flammable VOCs, wood tar, and creosote. That's what a low-temperature, force-cooled fire's liquid condensate
literally is.Yes... it has been done before, but it has been known since the mid-1600s as a "wood vinegar retort" for the production of pyroligneous acid (a mix of acetic acid, acetone, and methanol) plus wood tar and turpentine via
destructive distillation ...ever since Johann Glauber decided to see what would happen if he stuffed a bunch of wood not only into his alchemical furnace's firebox
but also into its distilling retort and named the condensate thus produced "
acetum lignorum."
en.wikipedia.org/wiki/Dry_distillationen.wikipedia.org/wiki/Pyroligneous_acidThose condensates aren't just flammable volatile organic compounds (VOCs)... they're potent solvents and quite toxic... not something you want to be shunting into an open drain right next to a firebox in a living space.
Your water tank, with its internal heat exchanger coil — placed where it is, into and on top of, shock-cooling the whole interior of
what should be the rocket stove's primary [firebox] and secondary [riser] combustion zones ...is essentially a Friedrichs condenser atop a wood vinegar reflux distillation column.
The whole premise behind the Rocket Mass Heater's burn tunnel and riser design is to achieve complete combustion of the wood gasses *first* — and
then harvest the heat by putting it into a heat-storing mass.... which, btw... this "RMH" doesn't have a thermal storage mass so far as I can tell... it looks like you're trying to make a direct-fired water boiler out of a rocket stove and have accidentally reinvented a refluxing wood distillation retort.
(uploading an imbed of your drawing I pulled from the BBCode)
...have a look at some of the other recent threads here on water heating with wood. There are a couple safe ways of doing it — and a whole bunch of really unsafe ways.
