Pieces back in place after mortaring, and modded the air channel into two pieces:
Ready for fires!
Now the Rocket Stove is at a point where it works fine (does take a while to warm up…), as a space heater, which isn’t what I need, so If I want to get any use from it for heating, I need to run some ducting, which I drew up some plans for:
Thinking about a new steel rocket stove heat exchanger design today, this is what I’ve come up with:
Water travels up the copper tube(s), pretty self explanatory, red arrows are the hot air. 12mm copper cost around $5 per m, so not ridiculously expensive… Ideally the air gap between the tubes at the top would total say 110% of the heat riser cross sectional area, so it can flow just a little easier through the heat exchanger with maximum contact. Also dont want to cool the heat riser too much, nor stop the flow of gasses by forcing the air down (as opposed to it falling down due to being heavy after burning) Hmm…
I modified the location of the fire box to be closer to the heat riser. Which wasn’t super keen to play along when I tried to get a fire going.
Now that I cut a vertical feed tube, I may have been better off with just horizontal, as the vertical feeder didnt want to stay alight.. Maybe just needs better adjustments.
I think I’m ready to bin the cement design. The heat riser is too wide, people are getting really good results with all metal smaller designs. Although if I can get the fire box to work, I could possibly have success running an metal air duct in a spiral through the drum as a hot air blower, then run that duct through a window… 125mmx3.6m ducting cost $24 (for outside the drum to house) so… not impossible.
Seems there are an endless supply of people using wood stoves to create water heaters, even a few who are generating steam for power generation. It’s so easy for me to complicate this with ideas use steam mechanical energy to pump hot water, I think first I want to understand how I can get efficient thermal transfer from the heat riser to a liquid, ie water heating. The most common way I’ve seen on youtube is heaps of copper tube, one guy used 150 feet just for steam!
Ok so this is an awesome rocket stove, just using a tree trunk section and some chainsaw work!
I’ve noticed the most common pipe diameter is around 3 inch around, and people seem to be getting heaps of heat with this. Mines way more than that, on the previous page, I showed a 3 inch diameter is 127cm sq thanks wolfram alpha! Whereas mine has a 190cm sq feed tube and 255 cm sq heat riser… So I guess if I can get this thing burning really well, it will burn through wood pretty dam quickly.
Finished the burn tube part of the mould tonight, that means the actual mould design is finished! Just need to touch stuff up, make sure that hopefully I can take this thing apart when the mould sets, make sure it will hold still while the concrete sets and doesnt lift up anywhere or anything. So 8 days so far, not quite a week, but meh its basically ready to pour now.
I sealed the internal parts together with silicon that was laying around, which hopefully will be easy enough to break apart once the mould has set, but strong enough to hold for any shocks or whatever when I pour the mould.
Yesterday I was able to source some 190mm diameter cardboard tube for free, which will make a perfect vertical burn tube size. Today I’m drawing up the dimensions for the concrete mould, and I found out I can get a 25kg bag of high temperature cement for $40, which should hopefully be enough for the jawb.
Now to make the mould dimensions, and get it made.
So the base of the mould is 2 sheets of ply thick, then there’s a bunch of stuff going on on top of that. All these cut off’s will go on the bottom, to create an air gap for thermal insulation on the bottom.