I have some 1/4" thick wall aluminum pipe which came from a boom off a commercial fishboat. On a 6" system RMH, could I use several of these pieces in place of a single piece of 6" metal duct?
The catch is that while the pipe is very thick...and very heavy...it is either 3 1/2" or 4" inside diameter. Now the net area of a 6" pipe is 28.27 square inches and the net area of a piece of 3 1/2" pipe is 9.62 square inches. Therefore three of these pieces add up to 28.82 square inches. I have enough to make 4 pieces of suitable length to go in the bench I'm planning. I could make a manifold to connect these pipes at the exit of the barrel, and I could do the same thing where the pipes would connect to the flue heading outside. This flue, incidentally, is a standard 6" flue already existing in the cabin, and goes straight up through the roof. It has the stainless steel sections once it gets to the roof.
I think that because of the greater surface area of the walls in this small diameter pipe that there will be more drag on the exhaust, hence the idea to use 4 pipes instead of three - which almost perfectly matches the csa of a 6" tube.
This would be a straight line system, not doubling back on itself.
Now this means that the pipes would be about 7 feet long, theoretically somewhat short to extract all the heat. But I was thinking that because I can use 4 of these pipes, side by side, that the aluminum might just do a good job of extracting the heat.
Now I'm a very old carpenter, (me and Noah built the ark, but he had better PR) not so much a metal guy, although I do get around with metal OK...after a fashion.
Can I get your thoughts on whether this even has a remote chance of working?
The section in this pic is a 3 1/2" piece inside a 4" piece, and therefore the walls are 1/2" thick!
keith s elliot : Jesus Wept ! Am I understanding that the aluminum boom that you wish to re-purpose has a taper to it and therefor The four sections, each 7' long
would each individually vary in size ? I certainly would not take on this challenge if I did not have to, but your build would probably be unique !
My first assumption would be that it would be very hard to get this system to draft ! That could be planned for -so that you could pop the clean out cap off of your clean
out at the base of your chimney, put a lit candle in there to get the draw started, and warm things up a little! Then replace the clean outs cap and build a very small fire
of fine split very dry kindling and proceed from there, I expect that this would be needed about every time !
So, If you want to try this idea, try it first out doors, simulating the Thermal Mass by passing the pipes through a wooden box filled with sand for testing purposes. At
ether end you will need to create a very large manifold to channel the gases from the Rocket Mass Heaters RMHs Burner Base and then another Manifold again at the
other end to channel your Hot Exhaust Gas flow to they base of your 6'' system. I rather expect that you will lose a great deal of heat up the chimney, instead of the
150dF allowable due to Your extremely clean burning RMH, i would expect temperatures near twice that !
When putting the finishing touches on your test build, remember that you will need to have a vertical chimney several feet taller than any nearby objects as soon as
you install your barrel over the Heat Riser !
This is where I always ask, have you been to rocketstoves.com to download your PDF Copy of the Brand New 3rd Edition of Evans' and Jackson's Great Book
"Rocket MassHeaters"? Enter discount code ' matchstick ' !
With over 100,000 Rocket Mass Heaters RMHs, built world wide most have been made following 'The Book' and 95% of all the first time builds (that worked) came from
'The Book' ! Hope this is timely and helps, For the Good of the Craft !
Think like Fire ! Flow like a Gas ! Don't be the Marshmallow ! As always your Comments and questions are solicited and Welcome ! Big AL
Success has a Thousand Fathers , Failure is an Orphan
Allen Lumley, yes I bought the book just a few days ago. Not trying to re-invent the wheel here, just seeing if this might work. It's a shame the pipe isn't 6", that would be perfect.
The pipe is either 3 1/2" or 4", and they used the smaller size where they joined the pipe in the middle. Then at the top end of the boom, they used a 3 1/2" section with massive clamps. I actually have a total of almost 40' of this pipe.
I think I might try to see if I can make this work just for the hell of it. You never know. I can always revert to plan B...which would be the book way. It's always nice to be able to use what one has on hand.
BTW, I have to say the book by Ianto is absolutely the most fascinating thing I have ever read. Been through it twice and definitely need to read it several more times.