Hello everyone and thanks for the kind words.
I posted the video a couple of weeks ago, so I was surprised to see a big spike in the vimeo view count this morning. I guess, this means it got cold wherever you guys are. Heating season is on
you are right. Looking at my exhaust temps, I could have increased the thermal mass and made the top section (which is one large bell) larger. On the other hand, my place is not very big and I will see this winter how I fare with the dimensions I chose. One of the reasons I did not go bigger, aside from over heating the place, was that I was not sure how much I could alter the plans I had, without it stopping to work (chimney draft and all). It was the first stove I ever built, so I mostly tried to stick to the things I knew were working in the original design.
As for the classification of the stove, this particular design shares properties with different types of stoves and I'm no expert. I put it here under wood burning stoves mostly because it burns wood and the category seemed to me more general, which might just be because I'm not a native speaker. But I see no problem with flame wars. They would appear fitting when it comes to stoves and "things heating up" is a good thing for the approaching cold season
Here is how I would describe Trev's vortex design, my stove is based on:
The way the burn chamber is constructed there is some horizontal rocket action going on upping the temps.
The way the thermal mass is constructed it is a masonry stove.
The way it looks on the burn chamber side with the glass door is like a wood stove.
The way it can be used is like a kitchen wood stove with its cook top and oven.
The way it behaves is like the Kachelofen (Grundofen - ask google for pics, I did not get a proper translation. It is typical for Austria and southern Germany) I grew up with. It stores and radiates heat for 10-12 hours.
well, if you live in a really nice place I could consider building one for you. Then again, if the place had palm trees, you would not need a stove
But if you are half serious about the idea, talk to Trev over at donkey32. He has actually built several for other people and he is the real pro.
As for efficiency, I will know more after the winter. I made some temp measurements on my third burn with one of these laser thermometers, but it is off ebay and I'm sure it is not industry quality and might be off a little. Better and more meaningful stats I can provide after the winter. Here is what I noted down and recall:
Since I still lack a scale, I don't know how much wood I used in that burn but I would estimate it was:
20 pounds of really dry mixed wood (beech, birch, chestnut, stuff).
Half of the wood to start the fire. Half of the wood added after about an hour
burn time: about 2.5 hours
heat in the burn chamber (pointing in the fire) reaching 1700 °F
insulated walls of the burn chamber reaching about 1200 °F
top cook plate reaches about 830°F (water does get boiling quickly)
glowing coals: about 4 hours in. Burn chamber walls radiate 850 °F inside. A little wait and you have perfect pizza temps. 2 hours later it is bread time.
exhaust pipe temps right out the stove peak at 300°F (i also built a short cut for a better draft, which I use when kindling the fire) and go down to about 170°F. When the fire is out, I flip a lever to put the damper of the pipe to use.
surface of thermal mass reaching 180°F in some parts on top. 150°F in others. Since the surface is not smooth (like metal or tiles) but rough, it can be touched and leaned against, though during the hottest time of the cycle I would not press myself against it for too long
after 10 hours: thermal mass temp is at 110°F
after 12 hours: thermal mass temp is at 90°F
after 18 hours: burn chamber walls (inside) still radiate in the 90s. Thermal mass section has room temp (71°F)
I plan to experiment with a heat sink around the stove pipe to reduce heat loss through the exhaust.
One further modification I plan is a tube for secondary air in the top half of the burn chamber. The burn is clean as it is, but oxygen is always fun to add and should give even better efficiency burning all gasses. At least I think it will.
I don't think I need any of these improvements to make my place warmer (though we will see in winter - I'm in the alps at 4000 ft), but if these tweaks make the stove more efficient, they will save some wood.