Peter van den Berg

Markus Padourek wrote:Thanks for the information Peter, that does indeed help a lot. The idea would be to have well-insulated houses, and at list for our house designed with passiv solar principle, but not to passive house standards. And how long is each run for you on average?

Duration of a single run is something between 45 minutes and 1 hour, depending on fuel species.

Markus Padourek wrote:I did not know there was a difference between smoke and vapor plume (I am still relatively new to this topic) - what exactly is vapor plume?

Vapor is moist air, lots of water in the exhaust gases. On a chemical level, result of complete combustion is heat, CO² and water. One kilogram of absolutely dry wood will produce 0.5 liter of water. In the exhaust gases this water is in gaseous form so it won't condensate in the chimney as long as the exhaust temperature is above 45 ºC.

Markus Padourek wrote:Is this purely because the hot air meets with the cold air?

Yes, the steam condensates in the cold air as droplets which immediately spreads out and makes clouds of visible "steam" (*fog*) until it spreads out enough to evaporate again. Often the visable plume begins some distance above the chimney exit, 30 cm (1 ft) is no exception.

Markus Padourek wrote:And apart from the different smell this is clear visually because it is purley white fumes, rather than the typical dark ones, right?

Yes, the smell of wet charcoal is from 9-methyl ketone in very small quantities, real complete combustion is very, very close then. Real smoke moves much slower and tend to drift away without disappearing.

Markus Padourek wrote:Also I would be curios, which batchrockets results do you know of? I only know of https://www.uzume.fr/

There's one Dutch guy who used the technology to build his own heater but refuses to recognize my work. He had his heater tested, one page of the report is here:



Another guy, from Belgium this time, implemented his own heater much later, his result page is here:

Markus Padourek wrote: - How long does one generally need to run a RMH for a day in a northern climate for a small house (30-60m2)? 1-2h? And would it be possible to reduce that with passive solar, that on sunny days one might not even need to heat?

It greatly depends on the level of insulation, but in our passive house in the Netherlands we use a 150 mm batchrocket system with a weight of two metric tons. Our house is larger, but the heater is run one charge of 3 to 6 kg soft wood species in the evening while it isn't freezing. The load is tailored to the weather forecast, more sun during the day means a smaller load. During frost periods we run it twice a day, during breakfast and diner. We had a cold spell in February with lots of sun during the day, one evening charge being enough. I have to admit the house sports a lot of glazing facing south, this helps a lot!

Markus Padourek wrote: - If one burns correctly, how much smoke is there visible over the duration of a whole run? I assume there will be some smoke at the start-up and maybe the end? Are there some videos that could be shown?

In a mass heater the core won't cool down completely between burns. We emploi the top-down lighting method, which emits a very little bit of smoke for about 5 minutes during startup. There's lots of water vapor visible during most of the burn of course, exit temperature at the top of the chimney is estimated between 80 and 100 ºC most of the time. This vapor plume dissolves in the air within a couple of meters and is transparent most of the time. It's appearance is much alike the vapor from a condensing natural gas boiler.
No smoke at all at the end of the burn, definitely.
There's a very old video, illustrating what is visable in frosty weather. At the time I could stand there, my head in the plume and frantically sniffing, only to detect a very faint smell of wet charcoal. Mind you, it happened to be a large fire that was raging in my workshop at the time.

Markus Padourek wrote: - How long is the "start-up" phase of a well-built and well-lit batch-box or dsr RMH? Some people were specifically worried about that phase, knowing it is the most polluting one and arguing that one central stove, distributing the heat to all houses, would be more efficient and reduce the pollution from the start-up phase (which I don't think I agree with, if we also consider line-loss and other possibilities we now loose, like cooking, etc).

Starting up time of a warm-but-not-hot batch box rocket is about 5 minutes, 10 minutes tops.

Markus Padourek wrote:Edit: I have also not found resources that go into details about the exact particles that come out of a RMH exhaust and how they compare to other woodstoves (mostly interested here in how dangerous they are for humans), but given that there are RMH here in the EU that have been certified and are far surpassing the current 2020 regulation as well as the upcoming 2022 regulation, I hope that this will provide enough security for people on that front.

Personally, I've seen the results of two tested batchrockets. First and foremost, those things emits very little smoke to begin with, the dangerous particles are organic, i.e. soot. The particles that remain are anorganic, the residue that can't be burned because these are the minerals that are taken up from the soil by the trees. The limit of dust concentration in the 2022 EU rules is 40 mg/m³ if I remember correctly, both the two rockets did 20 mg/m³. Both were bell constructions, which means gas velocity nearly stalls while entering the bell, so most of the dust is settling at the floor of the bell. The first time I checked my heater I stuck my hand through the cleaning hatch and I couldn't feel a thing. I tried again and waved a bit with my fingers, there was some resistance then. Very fine dust, not what one would call ashes from wood burning.

Suffice to say, batchrocket don't sport an ash drawer because there's no need to, anorganic ash particles are a very very small percentage of the wood's makeup.
I hope this helps.

Batchrockets with no riser at all do exist. They're not on the site as yet, most of my time is gobbled up by experimenting. Those newer cores are called Double Shoebox Rocket, or DSR for short. There are two of those, DSR1 and DSR2. As it happens, DSR2's development has been ready for more than a year, DSR1+ is being worked on as we speak.

A very longish thread on Donkey's forum describes the development of DSR2, https://donkey32.proboards.com/thread/3503/double-shoebox-rocket-mark-ii drawings are released on the same forum.
To save you the time to find these drawings here's the post in which the first is released.
https://donkey32.proboards.com/post/33244/thread
Three others are released further down the above thread, on the following pages.

NB: Have a look at my YouTube channel, there are a number of videos about DSR1 and 2.
https://www.youtube.com/user/peterberg10/videos
The latest one does show very well what it's all about, is fire visability like this what you have in mind?

Maruf Miliunas wrote:So is the batch rocket burn just as clean and hot as the Kuznetsov per se?

Kuznetzov's heaters are generally larger than mine, another marked difference is this: my designs are checked over and over again. I spent years and a substantial sum of money in order to be able to come up with hard numbers and test results. Igor's designs aren't measured at all, as far as I know of. In my opinion it's highly unlikely his heaters and the underlying principles are tested at all, it seems to be all theory and told over and over again.

So the answer to your question would be more like: my batchrocket designs are burning hot and clean, my test data are there to back up such a claim. A small number of builders have had their implementations tested and approved for sale within the European Union.

What the numbers and results of Igor Kuznetsov's heaters would be remains an open question.

Maruf Miliunas wrote:Also, are there any mentions of air intake systems? I heard of designing an air pathway from the outside to warm up as it flows underneath the house before it enters the burn chamber, though I haven't found any information on that.

In my experience, outdoor air supplies other than a small open window at the wind side of the house would provide more problems than being solved.
Have a look at this website:
https://woodheat.org/outdoor-air-supplies.html
Reading "The Outdoor Air Myth Exposed" is highly recommended.

The first picture is from one of my earlier developments, in fact one of my own drawings, years before I adopted the batch box rocket idea. Around 2009 or 2010 I'm inclined to say. Its firebox isn't the same as Kusznetzov's, there's no lattice work at the firebox' ceiling, but a J-tube like afterburner behind it instead.

The heat extraction part happened to be based on what Kuznetsov and Podgorodnikov before him were building, bell-like constructions. In this particular experimental heater I tried to verify Igor's theories, it didn't made any significant difference. Efficiency-wise, as well as for quality of combustion. At the time, I used a Testo 327 to measure what the output of the heater was. The only difference which was evident happened to be the fact that with the so-called "dry slots" open, the chimney temperature went up much more rapidly as compared to closed slots.

On Donkey's forum there's a quite longish thread about what I did and how. In case anyone is interested, here's the link:
https://donkey32.proboards.com/thread/40
and another thread following the above since it was hyjacked more or less by some eager people.
https://donkey32.proboards.com/thread/113

Magnesia chrome bricks are great for mass, very heavy and virtually indestructable. Not good in places where you need heat quickly, they tend to gobble up lots of heat. So, not for the riser or firebox or whatever.

You are right Solomon. Is it possible to split the relevant posts off to a separate thread? Any staff person that has more experience handling that type of problem than me?

Edit: OK, it turned out to be very easy, so have done it already.

Solomon Parker wrote:Peter, there was some mention of ash buildup in one spot of the back wall curve suggesting the possibility of some slight adjustment to the curve.

Yes, that's true. It's a spot where a small amount of ash will come to rest, just before the ramp of the back sweep starts. That patch is there always, it doesn't grow so I wouldn't use the phrase "accumulating" for that. Interestingly enough, it happened to be the same in my development model so in the final design the back sweep was made sligtly longer. But as Donkey reported the patch is still there, all other ash in the burn tunnel will be blown out and settles in the bell, manifold or other wider part in the system. In itself, this is a huge improvement as compared to the simple shape of the original which can be easily clogged up completely by accumulating ashes.

So you could try to resolve this particular small niggle, but my guess would be: another spot will hold some ash, possibly more than before. As long as the back sweep ramp itself stayes free, it's a hard surface where ash is blown off quite easily. In contrast with a large patch of ash forming a soft surface which could lead to building up.

Solomon Parker wrote:I'm presently 3d printing a 25% version for close inspection. Maybe I'll start a new thread about possible modifications. Do you have any suggestions or do you think it's as good as it gets?

You do the 3D printing directly from the SketchUp drawing? Interesting!
In my view, this is as good as it gets, there's very little room for improvement and a whole lot for killing off the present behaviour. Only a rigid test program could establish whether or not any modification is worthwhile.