After yesterday’s post on designing my heating options for the cabin, I got a flood of the usual “you’re doing it wrong” emails. Not that I’m complaining, I actually found most to be very helpful and I’m grateful to everyone who took the time to write them.
Using some of the suggested improvements and a bit more browsing on YouTube, I came up with some modifications. One of the things that struck me after I made the initial post is that a pellet stove is basically a Rocket Stove on its side. It’s pretty much the same principle of thoroughly burning the fuel by mixing the air with the wood gas generated during the combustion process.
As with many pellet stove designs, this means it would benefit from a vortex generator; basically a static fan that sits in the flame allowing the gases moving past the blades to spin up (as opposed to an active fan which does the spinning). Also, the exhaust tube is much too small which can cause a potential backdraft through the cleanout or, more disastrously, out the hopper setting fire the rest of the fuel. The quicker I get the flames out the exhaust, the better it is. The gases will continue to combust in the exhaust tube as well, so really the burning process extends out the stove cabinet.
It did surprise me that I didn’t really need a second starter burner to get the gases going up the flue. I thought this would have been absolutely essential to prevent a backdraft, but apparently, as long as the air is coming from below in the primary burner, the hot gasses will exit the larger opening. Flames travelling the path of least resistance and all.
One thing I overlooked in the previous design is how I’m going to clean the whole thing. No matter how “clean burning” Rocket Stoves are, I imagine eventually you’re gonna need to clean the tubes In the rare circumstance of an incomplete burn, perhaps due to incorrectly prepared fuel, you would still need the option of a cleanout. This is why I worry when I see elaborately constructed Rocket Stoves built into the dwelling. If things go wrong, you’re in a whole heap of trouble and have a humongous mess on your hands deconstructing the whole thing. A hole or two here and there to clean, couldn’t hurt.
I still have to decide how long I want the exhaust tube to be before connecting with the flue. Obviously, it can’t be too long since that runs the risk of a potential backdraft, but I also want to get as much heat into the living space before it leaves the cabin envelope. I’ll need to do some experimenting.
Now I need some welding lessons.