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| Stoves Archive for May 2002 |
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| 102 messages, last added Tue Nov 26 17:31:37 2002 |
[Date Index][Thread Index]
Re: Air is Number 1!
Tom R, Tom M, and all,
Tom R's message is left below for reference. (and Tom needs to forward
this to the gasification list because I cannot post to that list.)
First, I agree that we start with the principles!!!!!!!! And all of the
principles I know about stoves and gasification I learned from Tom Reed, or
on the Stoves list, or a little at Boy Scout camp.
Second, Tom wrote:
> AIR CONTACT IS THE MOST IMPORTANT PART OF STOVE DESIGN.
>
>So, in stove design, first focus on the principles - how the pyrolysis will
>occur, how the resulting gases will access oxygen, then worry about Paul's
>four principles which are certainly also VERY important.
>
>o fuel
>o combustion chamber
>o physical structure
>o the cooking
>
>(However, aren't combustion chamber and physical structure the same thing?)
No, they are NOT the same.
Structure (physical structure) of a stove includes things like legs, and
oven, and plancha, and pot-insert holes, ventilation that is not primarily
for increased draft, and where you place the combustion chamber.
The combustion chamber is where the burning takes place. And therefore,
the construction of the combustion chamber DOES include the issue of how to
get the air into the right places at the right time in the right amounts.
Physical structure and combustion chamber are VERY DIFFERENT, but we must
be aware of one as we develop the other, or we will get into trouble quickly.
I believe there is no confusion about what is meant by "fuel" and by
"cooking" as being two other components for consideration when doing stove
development.
Back to the issue of "air" and Tom's statement that "AIR CONTACT IS THE
MOST IMPORTANT PART OF STOVE DESIGN". I agree!!!!!!!!
But that air contact takes place where? It takes place in and around the
combustion chamber.
However, as I think further about air, I realize that all air is NOT the
same. The air in Illinois (650 feet above sea level, humid in summer) and
the air in Denver (5200 feet ASL and "Denver dry") are not the same air.
Also, a unit of preheated secondary air at 400 degrees F is not the same
air as the exact same molecules as a unit prior to being preheated.
Now the question is: Do we as stove designers make an issue of "aires"
(plural) like we make an issue of "fuels" (plural)? Or can the "combustion
chamber" attributes actually incorporate the issues about "air" being
pre-heated or fan-forced or something?
Let us not neglect the importance of air. Air is like fuel: If either air
or fuel is absent, there will not be any combustion. Now THAT is a
principle!!! (See, Tom, you have taught me well.)
(Smile).
Well, I just now thought that I should modify my list of components to become:
combustion materials (fuels and air)
combustion chamber (generating energy from the combustion materials)
structure (holding together the physical parts in a usable way)
cooking (getting use from the "stove", such as pot-configurations for
socially-defined methods of cooking, to also include space-heating if needed)
Please let me re-phrase those 4 components:
stove combustion materials (fuels and air)
stove combustion chamber (generating energy from the combustion materials)
stove structure (holding together the physical parts in a usable way)
stove cooking (getting use from the "stove", such as pot-configurations for
socially-defined methods of cooking, to also include space-heating if needed)
I hope that this has helped clarify why I have separated the issues of
stoves development
into 4 components.
Interestingly, those of us on the Stove list serve have our own specialties
in the 4 components. Many are combustion chamber specialists. Others are
fuels people. A smaller number are into the structure issues. And a few
(anybody??) on the Stoves list are focused on the cooking issues. And yet
we all seek "stove" improvement.
Have a good weekend !!
(or if you do not read this until you are back at work, I hope you had a
good weekend.)
Paul
At 05:28 AM 5/24/02 -0600, Tom Reed wrote:
>Dear Paul, Tom and All:
>
>Tom Miles hits it on the head. Phlogiston (oxygen) access is the most
>important part of biomass combustion, gasification and stove design!
>(Dephlogisticated air is the original name for the combustion gases exiting
>your exhaust pipe, since the oxygen has been consumed, making a useful, hot,
>non oxidizing gas. Try it for pyrolysis.)
>
>I have a commercial stove that is dreadful because the air enters at the
>wrong places - too much at bottom (releasing volatiles and gases too
>quickly), not nearly enough at the top, so gases aren't burned before they
>reach their target, the pot being heated. By rearranging the air holes it
>burns beautifully inside the stove.
>
>I find that most stove tinkerers tend to focus on materials of construction
>first and principles last. This needs to be reversed. AIR CONTACT IS THE
>MOST IMPORTANT PART OF STOVE DESIGN.
>
>So, in stove design, first focus on the principles - how the pyrolysis will
>occur, how the resulting gases will access oxygen, then worry about Paul's
>four principles which are certainly also VERY important.
>
>o fuel
>o combustion chamber
>o physical structure
>o the cooking
>
>(However, aren't combustion chamber and physical structure the same thing?)
>
>Another MAJOR piece of the puzzle is water content (measured by weighing,
>heating to 105C for an hour (depending on size), then reweighing. Wood with
>30% moisture (jungle wood) is barely related to wood with 7% moisture
>(Denver Dry).
>
>Combustion of dry wood requires 6 kg of air for each kg of wood. For 30%
>moisture wood it only requires 4.2 kg. Pyrolysis of dry wood requires < 1
>kg air/kg wood; for 30% moisture wood pyrolysis requires 2 to 3 kg air/kg
>wet wood.
>
>So, principles first, application second will get us to a new generation of
>cookstoves!
>
>Yours truly, TOM REED
>BEF STOVEWORKS
>
>PS: I spent a day with Paul in Normal Illinois discussing all this and
>seeing a battery of new kinds of stoves that he is making. Very ingenious.
>There's a lot of room for inovation in solving the world stove problem, but
>it had better start with the principles.
Paul S. Anderson, Ph.D., Fulbright Prof. to Mozambique 8/99 - 7/00
Rotary University Teacher Grantee to Mozambique >10 mo of 2001-2003
Dept of Geography - Geology (Box 4400), Illinois State University
Normal, IL 61790-4400 Voice: 309-438-7360; FAX: 309-438-5310
E-mail: psanders@ilstu.edu - Internet items: www.ilstu.edu/~psanders
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