I have been kicking around the idea of a RMH for a while, and had some ideas that popped up that I wondered might improve efficiency &/ safety.
What if, instead of using a 55 gallon drum, a person used a cylinder of smooth rolled steel, then to that steel, you attached angles of 2-1/2X2 with a 1/2 flange made from 16, or 18ga stock, that was tacked, or spot welded to the barrel, with a slight overlap onto the angle before it, where it would also be spot welded. this would result in multiple square channels around the circumference of the barrel, the air inside these channels would warm from the heat directly coming from the barrel, and the vertical stands would act as fins further drawing heat away from the barrel, you would loose some of the infrared heat coming off the barrel but it would heat more air, and the outer surface might be enough cooler to avoid catastrophic burns as well.
Another thought was if you fabricated your barrel, installing a flange on the bottom& sealed the top, then attached a second rolled piece over the first that was 2-3" larger in diameter, resulting in a water jacket completely enveloping the barrel (vented) this water could be circulated for in floor heating& such.
allen lumley wrote:Our Rocket Mass Heater RMH, needs to quickly create the Freaky High Temperatures and Generate the Great efficiencies of its clean
burn ! As the water in the water jacket will rapidly steal the heat needed to maintain the high Combustion temperatures- never getting
above 212 itself - We have to expect that we would have all of the products of incomplete combustion for a while with every time we
light a fire in our RMH This would prolong the amount of time that your RMH needs operator attention 2 or 3 Xs standard -
This type of burn is the kind of smoky fire that annoys your neighbors - if you have any !
As I understand, it is critical for the temps to get super hot i the flame tunnel& the insulated chimney, after that, you have the barrel which is the primary heat exchange, there you want to extract as much heat as possible, 1 to heat the space, 2 to collapse the gas cloud to settle to the exhaust manifold, then through your secondary heat exchange, aka mass bench.
You could add the fins to a 55 gallon barrel, but you would have to make notches to clear the ridges rolled into the drums, so it would be much easier to do it with a straight wall drum.
The outdoor boilers lack the insulated fire chamber& insulated chimneys.
It is occasionally possible to find a smooth-walled 55 gallon drum - I got one off craigslist for $20.
The critical area is the internal combustion zone, however it might make a difference if the water jacket surrounds the top as well as the sides of the barrel. There you might get condensation which could drip back into the heat riser. I have an experiment planned for when I am not busy with critical projects to test a water jacketed RMH for tiny home heating. I will probably end up adding a deflector plate inside the top of the inner barrel, after I try it without.
I believe the barrel is intendedto pull heat out of the exhaust gasses, causing them to drop and push on through the mass.
I would like to see a water jacket that was open topped and did not need to be welded, maybe two steel cylinders,the inner one closed topped , both set in a hydrolic cement?