Nathan Prince wrote:Sourcing materials for a RMH, cabin is 250-300sqft, r-20 walls, r-30 roof&floor, in hardieness zone 3. As a primary heating source, what would be an ideal flue size and bench mass volume. Other than the heat riser and bench mass, the construction will be heavy steel (at least 1/4").
Because common pipe is in whole inches, what consideration should be given to interior diameter through the tubes?
113m² of workshop 57m² of flat approximately. And around 635 m3. Euro R7 in the walls, but not on all of them. South and east facing entrance walls are not insulated more than R1, flat gables are R2 or 3 big maximum, and R3 in the roof. All of this is euro R values.
And i usually burn this much oak in three burns a day. One morning, 2 evenings. One more in the evening if it's bellow -10C°.
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.