Well, they manage to burn petrol at stoechiometric mixture For fulle efficiency, and only manage a yiels of 30/40%
How in the life, can you immagine to do better than engineers?
Let me explain.
You burn wood, and may be you can manage 90% perfect combustion. On petrol they might manage 98% since it's all hydrocarbons.
If ever you"re lucky enough, you can transfer 80% of the energy released to water.
That's already only 72% of the original energy.
Then, you might transform only 70% of that heat energy into rotational energy in the turbine. 0.504% of original energy input. Ok, you can use the heat to heat homes or else. Still need some to create the draft.
Then, you have the electricity production side of it. You can't reach a cos phi, of more that 0.89 or 89% of the energy inputed on the shaft, into electricity, so that's 44.85% of original energy input. And i have used very optimistic figures.
Thomas, cooking plate on top of a batch firebox works wonders to me!
Oven wise, i know some are having problems of low temps right with white ovens.
White oven, no smoke or hot gases allowed in. Separate from the bell.
Black oven, smoke or even fire in the oven itself. Works hotter. That's pizza or old bread ovens. To me, the best idea, i think, is to skip any after riser oven, and use the firebox as an accumulation oven. But only doable on big systems.
Thomas, i only have something like 5 builds, including the trial ones, in J tubes. I switched early to batch.
If you want a bench, i think using Matt's half barrel bell system is good. You only count your half barrels as ISA, not the floor.
And iirc, a 8 incher J can cope with 4 to 6 m² approximately. So 1.86m² for the barrel, half of that 1.86m² per half barrel following that, may be 1.80 since you cut the ends. 1 barrel over the riser, 4 half barrels, as a single bench in the bench. And you should be there. You make a plunger tube at the end of the bench, reaching the chimney, and rise the tube from the floor, is it's not working too well. To adjust for the proper ISA.
Matthew Walker's photo set is half barrels, just tucked in the mud bellow. You leave a one inch lip when you don't want a separation between half barrels.
Why don't people use it more?
Two things, they don't understand it.
And it's not as simple to build as mud around pipes in a bench. Well, so they think.
I like my cheapo method, i buy home heating fuel tanks, or tractor fuel tanks; You know, rectangular metal vessels. Cut two openings at the bottom. For the pipes to link in and out. And cover that with whatever i can get my hands on.
Look at the pics. The secondary burn area is not at all the same. In the DSR. Flame goes up, and gets mixed with secondary air in a rather big chamber. While on Trev's stove, gases goes into the port. Then get bent 90 degrees. And the secondary burn chamber is smaller. Which leads me to think that gases might not have as much time to burn, as the double shoebox.
Thomas, i wouldn't do metal fins myself. Problems of expansion, contraction. First of all.
Then the heat transfer from metal to mass isn't well studied either. My opinion, stay with bricks.
And another opinion of mine. if you increase the inside surface. I think it would be interesting to do something like a double skin of bricks. To accumulate more heat. Instead of releasing your heat fast. Increase the temp of the mass, and it's release time. If you want fast heat, a bell metal top or window in front, to release a bit of fast heat would be in order.
thomas rubino wrote:The slab will warm up some BUT the earth will never warm up and it will continue to steal heat from your core. Your firebox can be build on a perlite/clay base. Your mass can be simply built over several inches/MM thick of cob, with plenty of straw mixed in to make it insulating. Your horizontal pipes lay on top of this.
Well, i agree and disagree. The earth insulates some. And if the construction is by the standards, there should be either a gap under the slab, which can be insulated. Or insulation.
Plus, there is the speed of travel of the heat in the ground. The heat making a cone or sphere of heated ground under the heater. If this is placed in the very middle of the house, it can be of some use. Since the ground warms up , the more you go towards the center of earth. There is a moment heat from the house, and heat from the ground equilibrates. Ok; may be very far! :D
Thomas, i think this has been tested. You should check the finished builds at donkeys.
With a normal triple bell, you can go down to 6.8 m2.
If you do the stub trick, two bricks laid normally take 264cm2 it goes to 638cm2 with one brick perpendicularly for the same original surface. 141% more than the original surface.
So, that would make the bell 7.5m2, since you can't do the stubs on the bell cap. For a single bell. Which would be 9.4 originally.
If you bother to do a triple bell with the stub system. You could end up with a 4.82 m2 bell. Well , no, i'm daft. Forgot the caps. 5.3 may be. A cube of bricks 1.2 x 1.2 x 2m outside. Would do the trick as a single bell with stubs. I would say you could also consider the new shoebox batch. And a plunger tube may be.
Glenn Herbert wrote:It is always considered a very bad idea, and prohibited by code, to connect two appliances to one chimney. Draft can be unreliable, and one may have a bad effect on the functioning of the other.
And in case something went very wrong. It could kill people in the house!
And i would also cut the top of that pipe lengthwise, except for it's mating end; Raise two sides of that cut to weld under that barrel lid, for a bit more depth. Which would accommodate more fly ash. And obviously make a plug to use as a cleanout.
What length of pipe, and how many elbows do you have there?
He wants to use a masonry chimney as mass. If the wall is half outside, it will heat up the birds. Your case is different. You're making a RMH. Not a batch rocket with a bell. Still, if the bench is against an outside wall, remember to insulate bellow and against the wall, to avoid conduction to the outside world. And BTW, nobody told you yet, that a bassement RMH isn't worth much?