Karl Harasyn wrote:
What in hoping this would accomplish by having the top of the heat riser submerged, with a jacket around it before passing exhaust is to extract the maximum amount of heat from the fire while also keeping the burn chamber and heat riser hot (as opposed to the water pulling heat directly from an unjacketed heater such as a commercialy available hot tub snorkel stove).
I just want to revisit this - its a perfectly understandable approach to put as much of the hot area into contact with what you want heated. Burn wood, make heat, move heat. The hard part to understand about RMHs is that the gain in efficiency happens during the burn - that the combination of feed tube, burn tube, riser (and bell) are a finely tuned engine for producing heat. Altering a part of the engine can have huge consequences ... so too short a riser, placing the whole thing in water, too much cold back pressure - these are like the potato in your auto exhaust, or some some of intentional de-tuning of your engine. And you can't just have a free-burning stove in a tube and expect it to perform. I do wonder how the proposed idea - inserting the entire bell in the water - would work. It seems to me like all that cooling would act like a brake dragging on the engine, but maybe not.
So to paraphrase Glenn, put the engine outside of the IBC. Wrap it in insulation, then pipe that heat into a stratification chamber in the IBC.
Again, its hard to wrap your head around. I'm going to throw out some random numbers for illustration. The snorkel style stove is (say) 80% efficient at transmitting heat into the water, but because it doesn't burn efficiently only 50% of the potential heat is created. So 40% of the potential heat gets into the water. The RMH "engine" placed outside of the water , even if insulated, is losing heat to the atmosphere and its mass - so let's say that its only 60% efficient at putting heat into the water. BUT its something like 100% efficient at converting potential into actual heat - so 60% of the potential heat gets into the water. That's 50% better than the snorkel, and its all because the "engine" is so much more efficient. Again, numbers are imaginary but the conclusion is, I think, real.
Note that the numbers are very different for heating a house - comparing a standard wood stove to an RMH is slightly unfair b/c the standard stove doesn't try to store heat in a mass. But it does allow Paul to boast about how little wood they use!
So Karl ... building a J tube OUTSIDE the IBC means you can do it with brick/ceramic and it will last longer. Use the propane tank as a stratification chamber in the IBC (I'd suggest at least two of them).