BOOH V

[Nutcase]

I'd guess that the flue pipe wasn't a (relatively) expensive nickel chromium alloy, so perhaps the burners will survive longer. Cheap experiment.

My impression is that the peak heat zone effectively extends to the surface of the wood as it burns, just going by how things have shown heat damage so far.

[Nutcase]

Yesterday the weather was nice here, so I got a chance to set up and run. Aside from the horizontally loaded wood, I stuck in the piece of mortar coated blanket with some stuff on it.



You can see a burner on the left, a couple bits of copper wire, a 45˚ 1/2" copper elbow, already somewhat flattened in an earlier test, and the refractory mortar pita bread square at the right. The white granules are perlite.

[Nutcase]

The system began to draw immediately. However, it was slow to accelerate compared to the best run with BOOH IV. It didn't stop smoking until 7 min into the run. At around 8 min, the flames finally began to turn the corner into the chimney. The barrel top was a 290˚ at that point. Even after turning the corner, the temp rise was comparatively slow, taking 11 min more to max out the thermometer at 900˚. High on the side of the barrel, it was at 730˚.



The barrel has acquired a dark band all around at this level, except on parts of the circumference not shown here where the first run with BOOH I burnt off the paint even more extensively. That first run was probably pretty hot.

[Nutcase]

Here's a shot down the burn channel, just because fire is pretty. The urbanite chunks were there to prop up the ends of the sticks earlier.



There are things to see with practical implications, looking down the burn channel, though they don't show well in snapshots. Maybe I'll set up on a table today so it will be more convenient to watch. You can see streamlines of smoke and streamlines of flame, quenching near surfaces, semistable vortices...
I think the system was more sluggish for a combination of reasons related to the configuration. The burn channel is long, so the fire has to build up more before it turns the corner. Lengthwise flow reduces the amount of air getting to the surface of the wood, so the char doesn't burn off, slowing heat transfer into the wood. The air entering the system is less turbulent because it doesn't have to make a turn at the inlet.

[Nutcase]

Here's a shot down the burn channel after the fire burnt down.



Not too informative. The main thing is that the channel is not obviously damaged.Just ignore that flap in the back, was there from the slapdash construction of the join to the chimney. I'll do something about it eventually. The burner was already a bit bent out of shape, but it seems to have sagged some more to conform to its support. The orange may be from dirt incorporated into the bark of the fir. I'm not entirely sure about that. It is certainly a fuel residue.

[matt walker]

I was going to say that I think the horizontal feed may be hindering the complete burning of the fuel due to it being not as capable a carburetor as a verticle, but man, those are some high temps. That barrel face temp is a really hot rocket stove, in my experience.

[Nutcase]

Here is an overview of the test tray:



You can see that the tray has acquired several more fractures, and it is beginning to fall apart, and the pita square has changed from buff to light green. The copper bits didn't melt, but they are all have flaky oxide layers. The elbow is somewhat more flattened.

This photo shows one particularly glossy and melted patch of the tray:



Regardless of the nominal temperature rating for this mortar, it isn't holding up to the temperatures in this setup. You can see some bits of perlite in this shot as well. It appears unaffected.

Finally, the pita square is worth a closer look:



The magenta streak is where there was a piece of copper wire. The cracks look like the result of uneven shrinkage, rather than heat stress per se or mechanical damage.

The bottom line here is that the refractory mortar I have in hand now probably isn't going to be very useful. I'm reading up on a variety of other options for a hotface and/or cast system components. Here's a link to one particularly extensive and informative thread on this topic:

[Nutcase]

[matt walker]

Awesome link NC, thank you. I can tell you definitively from my own experiments, rule out anything with portland(the cement). Frankly, you are close enough to Portland(the city) that if I were you I would go back to High Temp Inc. and get some 3000 degree hot face refractory. 50 lbs ought to be around $40 or so.

[Nutcase]

I will certainly be going back to HT, so I am restricting my research to things they sell right now, by and large.