The wood is loaded directly into the first barrel. The bottom of the barrel can be lined with firebrick.
I don't know if this would be considered a rocket stove or not.
That is an exact drawing of my sawdust burning stove if you rotated the whole drawing through 90 degrees. Where your label "hot" is the doorway. The bottom barrel is lined with engineering bricks and an industrial air filter is used to hold the sawdust. The paper in the filter burnt out on the first firing. It works very well keeping our polytunnel frost free lighting at 11pm and normally still going at 9am.
A barrel stove kit could be used with this one.
If I were doing this and hadn't done much experimenting with burn chamber construction I'd go with a tried and true. Frankly, the Dragon Heater core is the only tested shippable core I know of with solid data on it's efficiency, and those numbers are fantastic. To my mind there's not much reason to keep looking to refine a J, Peter's done the heavy lifting here and Cindy is tackling the difficult task of producing them for a very reasonable price. If you are frugal and have skills and materials you can get awfully close using E&E's proven brick designs, or the various home casting methods available.
I posted a simple medium mass bell design on Donkey's board just the other day. It's basically the second drum you have drawn there with some bricks stacked inside for mass. Solves the sealing problem with just masonry and adds a little mass to a lightweight metal barrel bell.
So, if I were looking for a solution along these lines, I'd put a proven J-tube in a barrel in a classic RMH configuration. Come out low from that first barrel, which is a riser/radiator combo, not a bell per se, and then bring the exhaust straight up to enter high on the side of the second barrel bell. Then exhaust down low from there and out of the house. I have basically this exact same setup in my bedroom right now for testing purposes, using my stand alone Walker Stove as the front end riser/radiator. Last night's test took the room from 59°F to over 80°F with one 4lb load and one 6lb load of dry fir. A little over an hour burn time and I had to shut it down. Room was still 68°F this morning after a night of 43°F outdoor overnight temps.
Matt Walker wrote:Come out low from that first barrel, which is a riser/radiator combo, not a bell per se, and then bring the exhaust straight up to enter high on the side of the second barrel bell. Then exhaust down low from there and out of the house.
I order to persuade the second barrel to act as a true bell, the inlet and exhaust should be both low in the side. In case both openings are fairly close to each other it will be sufficient to place the inlet slightly higher up. Not much, the lower side level with the top side of the exhaust. This way, the gases are allowed to stratify, hottest the highest.
In the construction you suggest a lot of the gases will follow the same path from inlet to exhaust opening. It will heat up, of course, but a bell construction will absorb more heat so the end temperature will be lower.