[Stoves] Top lit updraft combustors

[Norbert Senf]

On Fri, Dec 15, 2017 at 7:08 PM, Ronal W. Larson <rongretlarson at comcast.net>
wrote:

> (snip)
> 2.  But re my on-going dialog with Xavier (hugely longer today) on this
> same topic,  I need to point out that Norbert said:  “*When you get into
> the weeds of “what is the repeatability of your laboratory method”, the
> answer is “we don’t know”, and the next best answer is “plus or minus 40%,
> based on limited data”.*
>
> For the WBT under discussion for stoves, I think we are probably about +/-
> 5% (example:   such as Tier 4 re cooking efficiency at 40% +/- 2%).  I’m
> happy enough with 5% repeatability and see in the standard deviations
> numbers much smaller at any single laboratory.  I gather Xavier thinks that
> is not good enough, but I still have to read through his many articles
> provided today to understand his concerns.
>

Hi Ronal:

Just to be clear, I was referring only to repeatability on PM measurements.
In testing that we did on masonry heater with standardized fuel cribs, we
managed to get +/-10% (coefficient of variation), which is the best I have
seen except for pellet stoves. However our repeatability on efficiency
during the same tests was +/- 0.26%.
http://heatkit.com/html/lopez2a.htm
This is "same lab same operator". Much harder to do "different lab,
different operator", as you are required to do (theoretically) for EPA
round-robin proficiency testing.

(snip)
>
> *[RWL3:  Norbert - my interest in this topic is from the perspective of
> char-making stoves (both cooking for this list and heating from yours).  In
> your world, would the practitioners accept the idea that your “kilogram of
> fuel” be modified by subtracting out the fuel that went into char?
> (I’m simplifying here, because char has higher energy density).  I’d
> appreciate anything more you could add on “harmonizing” with char in mind. *
>
> * I like both your above answer and the earlier part I have not copied
> here**;  just want to get your views on this list concerns.    *
>

In our PM testing with cordwood, it is pretty clear that there are no PM
emissions from char (other maybe than flyash). We can shut off our sampler
early with no difference in results. Opacity testing will confirm this.
Therefore, I doubt whether you need to subtract the weight of the leftover
char, which would give you an erroneously higher g/kg number. One of the
"tricks" in EPA certification testing is to prolong the charcoal phase of
the burn as long as possible, which of course reduces your g/h number. Your
g/kg number would remain the same. Everything revolves around the magical
"EPA number" g/h. It should be g/kg, particularly if you want to compare a
wider variety of stoves.

>
> Yes but of course we would be interested in figures for all
> cookstoves, not just TLUDs.
>
> What I want to know is how cheaply could acceptably accurate and
> precise (i.e. repeatable) protocol and equipment be made?
>
> *[RWL4:   I think Andrew is (tn part) here raising the issue of what we
> call a WBT - water boiling test.  A certain load for the test.  Do you see
> anything wrong with a 5-liter standard cookpot of water, where you measure
> both temperature gain and evaporated loss?  (with arguments about how to
> handle char.)  Perhaps describing a little more on your thermal equivalent
> of a reproducible load (with char-making, if you can), valid anywhere on
> earth. *
>

Ha, ha. I met Crispin a few years ago at a workshop that he gave. I knew
him from this list, but never realized he was Canadian. I invited him to
join our MHA technical committee, where he has made some great
contributions to the fundamental science. He has also talked my ear off
about the boiling of water test and what is wrong with it (simmering, for
example). I have no experience with this whatsoever. Maybe you need to
manufacture a "standardized test pot", perhaps with a calibration
certificate and a serial number?


>
> *  Do you think that your test approaches have helped or hurt your
> industry?  (EPA and all the other tests.)  And users?*
>

Definitely helped. We got started with a $100,000.00 project, that was
fortunately funded by others, to test masonry heaters and masonry
fireplaces at a university laboratory. We didn't know anything at the time,
and didn't really learn all that much for the money, except how expensive
it was. We realized we needed be able to do our own testing. Fortunately we
had a connection to OMNI-Test in Oregon, where we met Skip Hayden and he
introduced us to the Condar sampler. We have been able to do some very
fundamental stuff like the (PM) repeatability testing on cordwood, that
simply didn't exist in the literature. We have a pretty exciting project on
the go at the moment in partnership with the Masonry Heater Association of
France, to develop a software simulator for possible use in certifying
one-off handbuilt masonry heaters. We are also working with Crispin and his
new decombustion theory to incorporate additional instrumentation such as
measuring flue gas water content, to look at the changing fuel analysis
during the batch burn.

Our users are heater masons and manufacturers. They have more information
on what innovations to incorporate into their own commercial activities.
The Austrian eco-firebox is a hot topic at the moment. We are also working
with EPA to get a method to certify manufactured masonry heaters, and
possibly one-off site built masonry heaters. Our market is so small that
the actual difference in the air shed is not much, since we are already
clean. We have to compete with dirty "outdoor boilers" in rural areas (and
some urban areas like Fairbanks Alaska), that have literally 100X the PM
emissions from the same piece of wood.


> * I know from watching your video that the emphasis there was on carbon
> buildup on filter paper.  And “our” tests seem to have some of that.  I
> personally doubt  that individual “stove activists” on this list will want
> to get into the detail you showed on your video, but maybe you could say
> more - and about the other hard one: CO.*
>

CO is pretty easy. You need a gas analyzer. For wood, you need a minimum of
something like a Testo 330-2, which has CO dilution. In other words, when
the CO gets above 5,000 ppm, it kicks in 10:1 dilution, which allows you to
continue to measure, and prevents poisoning of the expensive CO sensor.
There are also some very inexpensive NDIR benches available now, which
might portend more affordable CO and CO2 measurements.

CO is interesting to watch, but we don't care that much about it. It is not
regulated in North America, and is not a health issue except in dense urban
areas. When we tested the Austrian eco-labelled air system, PM dropped
about 50% and CO dropped about 80%. We were a lot more excited about the PM
drop, because this is the number that matters here to regulators. Europeans
have told us that the United States is about 10 years ahead of Europe in
air quality regulation. Largely due to California, in particular Los
Angeles. The Europeans are only just now recognizing the PM problem in
urban areas from diesel and wood burning, and addressing this in their
regulations.

Best ............. Norbert

-- 
Norbert Senf
Masonry Stove Builders
25 Brouse Road, RR 5
Shawville Québec J0X 2Y0
819.647.5092
www.heatkit.com
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