what temperatures would a person want at the top of the barrel to be safe? what are the average temps people are seeing out there ?, I was testing mine out and I am getting about 660F at top center of barrel.
That sounds pretty good. I have heard of people getting up to 1000F on the top of the barrel, which is as hot as you would ever want. I once got about 500-550F on the top of the barrel in a temporary demo 6" system.
I don't know how accurate these magnetic thermometers are (see photo below), but mine routinely goes past the 900 degree F mark using a batch-box type configuration. Placement of the thermometer is ~5 cm below the top rim of the barrel and is magnetically attached to the barrel side-wall. The temp will then fluctuate between ~400F and 900F depending on type/quality and amount of wood/scrap being loaded into the burn box.
“The most important decision we make is whether we believe we live in a friendly or hostile universe.”― Albert Einstein
Anthony, what type of combustion core? J-tube, batch-box, what not?
Back in March I was testing a freshly built 6" batch-box with IFB heat riser. Burning only one third of a fire box load of very dry beech, the top center of the barrel easily peaked to 650° F. and 500 to 550° F. on the upper most barrel sides. The mass isn't fully dry yet either.
I am sorry it took so long to get back to your question, for some reason my email never notified me of messages,
my system I built is a 6"refractory cast core, I feed it wood pellets from the top( like wood on the j type) but is sealed around the pellet feed tube, it gets its air from the front L shaped unit, so mine I guess would be considered a L style, when I tested it out in the garage I was getting nice temps from 600-650F on top barrel, then I built some different shaped pellet baskets to experiment and see what things would do so far the half V style seem to give me the best temps, I am still experimenting to try and get more heat out of it, I now have it installed in my house, I removed my wood stove and set the rocket heater up, and it also works fine in my house, I just would like to get a little more heat out of it cause I have a huge house to heat, 2500sqft, I built a plenum around the barrel and hooked to my ductwork and hooked up a fan to plenum to move the heat( just like a furnace) it does work better than I expexted, I have about 6' of pipe going to my masonary chimney and the temp on the exhaust pipe is only about 100 F so I am not losing much heat out the chimney... my theory might be that I need to feed it more fuel to get more BTUS out of it???...still experimenting, this fall I might buy a bag of rice coal and try that...because there is about 13,000 btu energy in a pound compared to 8,000 in wood pellets ???
Location: Southern alps, on the French side of the french /italian border 5000ft elevation
you are correct, I have no mass to my system, just using the barrel as my heat exchanger and forcing the heat off barrel through my ductwork with a fan (like a furnace).
my only downfall that I may see is the longer burn tunnel, the reason I made it longer is I needed room around the barrel to have a plenum, my burn tunnel is 20" and my heat riser is 40", I so far have not had any problems with it running like it should though... it sounds like a rocket ,temps anywhere from 550-650 F, I may try insulating the heat riser a little more, maybe with a ceramic blanket, right now the ,cast core and heat riser are made out of castable refractory cement /perlite, 1/1 by volume, with 2 inch sidewalls, the core/tunnel section is inside a metal box with perlite surrounding it 1" all around it.
when I get a chance I will upload the pictures of it.