Advice on Building Half Barrel Bench with 6-inch Batch Box

I built a 6-inch batch  box. I now need to connect it to half barrels in my bench. See pictures.

I want to connect 2.5 meters length of half barrels, then exit using 8-inch tubing.

I am not clear how to connect the half barrel to the heat exchanging barrel. See my photo. The gasses will need to move down from the full barrel and connect to the half barrel about 8 inches below it. I think I read somewhere that the height of the entrance into the half barrels needs to be lower than the exit on the other end. Is that correct? If so, by how much?

Dustin
Sichuan Province, China

Actually, the exit should be lower or maybe equal in height with the entrance into the half barrels.You want the hot gases to be able to rise and stratify at the top, so the coldest gases sink and go out the exit.

You can cut a hole in the bottom of the end of the half barrel for entrance and exit. If you want the half barrels to act as one bell (so the tops are all the same temperature), you would cut out all of the mating barrel ends except for a small strip at the bottom, to allow smooth flow between the barrels. You would want to seal these two barrel ends together so gases would not leak out at the joint.

You can use a piece of 8" duct to go from below the vertical barrel to the end of the horizontal barrel. You want to give the hot gases a smooth path from one to the other, using whatever shape of sheetmetal you can get or make to do this. It is important to not have a "kink" or constriction in the flow at the exit (called the "manifold") from the first barrel, but make this transition a bit bigger than the rest of the system for easy flow.

Glenn
I decided to use iron sheets to cover the space inside the bench (rather than half barrels). The height will be about 35cm and width 60 cm. The length will be 2 or 3 meters. What I am not sure about is whether to make the length 3 meters, or whether 2 meters will give better performance. Do you think 3 meters will be too long for my system?

Dustin

Peter van den Berg's recommendation is that a 6" batch box can support around 57 square feet (5.3 m2) of bell surface (internal surface, not including the floor), so it looks like 3m length would be best. It might be able to support a slightly larger bell surface.