Re: LETS ADOPT A UNIVERSAL POT

[Larry Winiarski <larryw@proaxis.com>]

Dean and all

I strongly agree with Don  that we should use the larger quantity of water
and start time from the lighting of the match.It is much more
representative of the real world conditions--for the reasons that Don gave
as well as the other practical problems of feeding the fire and tending
it.This will be better reflected in trying to heat a "family size"amount of
water!

God Bless

Larry






At 08:22 PM 1/5/02 -0600, Don O'Neal wrote:
>Dean:
>
>I agree with standardizing on pot size and shape in order to compare data.
>
>But we also need to standardize more than the pot.  We should standardize
starting water temperature and
>whether from a hot stove or cold stove.  A hot-stove test masks
thermal-mass issues.  A cast iron high-mass combustion chamber 'well
insulated' will compare favorably with 'Kens finest' after an hour of heat
up but in that first hour it points out the follies of a high mass elbow.
(An expensive re-education on my part)
>
>I feel  that to get good comparative results (including elbow thermal mass
effects) our test should start at room temperature and that time zero is
the striking of the match.   A longer test (larger water volume, I suggest
1.5 gallons or its equivalent in liters) averages out the irregularities of
start up and by using a cold stove, would includes thermal-mass differences.
>
>
>
>
>This is not an unusual size pot for the Guatemala highlands.  Probably
about 3 gallons, most are about half of this..
>
>Dollar General here carries an economical stainless steel pot with lid ( a
little smaller than this) that
>is about right.  Larry took one back with him when he was here.  Maybe he
can show you that as a suggestion.
>
>Anyway standardization is a good idea.
>
>Regards DON
>
>HELPS International
>
>
>
>----- Original Message ----- 
>From: "Dean Still" <dstill@epud.net>
>To: <stoves@crest.org>; "horizon" <horizon@engr.colostate.edu>; "brad"
<bvanappel@yahoo.com>; "Cousins, Ananda" <ACousins@seattleu.edu>; "Daniel
M. Kammen" <kammen@Princeton.EDU>; "David Pennise"
<dpennise@uclink4.berkeley.edu>; "Delacie Barney"
<delaciebarney@yahoo.com>; "Derick Calderon" <entre16@intelnet.net.gt>;
"Don O'Neal" <dononeal@fni.com>; "Elizabeth Bates"
<elizabethb@itdg.org.uk>; "Frank Vignola" <fev@darkwing.uoregon.edu>;
"George Rudy" <rudy@wehi.EDU.AU>; "Grant Ballard-Tremeer"
<grant@ecoharmony.com>; "Jeff Conant" <jeff@hesperian.org>; "Jonathan E.
Sinton" <jesldc@dante.lbl.gov>; "Karissa Ansell-Bell"
<krisab@OREGON.UOREGON.EDU>; "Ken Goyer" <goyen@efn.org>; "Kenmore, Peter
(AGPP)" <Peter.Kenmore@fao.org>; "kenneth mark bryden"
<kmbryden@iastate.edu>; "kevin hallinan"
<Kevin.Hallinan@notes.udayton.edu>; "Kirk R. Smith"
<krksmith@uclink4.berkeley.edu>; "Lanny Henson" <lanny@roman.net>; "Larry
Winiarski" <larryw@proaxis.com>; "Laurie Childers" <childers@peak.org>;
"Lisa Buttner" <LButtner@winrock.org>; "Marian Grebanier"
<gandanga@dsl-only.net>; "Patrick Flynn" <pattiflynn@hotmail.com>; "peter
scott" <apropeter@hotmail.com>; "Peter Verhaart" <verhaarp@cqu.edu.au>;
"Richard Boyt" <rdboyt@yahoo.com>; "richard njagu"
<richardnjagu@yahoo.com>; "Rogerio Miranda" <rmiranda@sdnnic.org.ni>; "Ron
Larson" <ronallarson@qwest.net>; "Stuart Conway"
<stuart@treeswaterpeople.org>; "Tami Bond" <tami.bond@noaa.gov>; "Tempra
Board" <tempra@treeswaterpeople.org>; "Tom Miles" <tmiles@trmiles.com>
>Sent: Friday, January 04, 2002 5:21 PM
>Subject: Re: LETS ADOPT A UNIVERSAL POT
>
>
>> Dear Lanny,
>> 
>> Glad to hear that you want to continue the Rocket Wok project. I'll try
from
>> my end to use the stove as much as possible, get the students to use it and
>> give it a real try out. And I'll get you all the feedback. Also inform the
>> List.
>> 
>> I looked at your improved pot skirt and my two cents worth would be that
>> using a insulated Rocket combustion chamber under the pot gives us a lot of
>> draft so I wouldn't think that diminished draft would be a problem. Mark
>> Bryden who advises me about stoves, has the idea that increasing the force
>> with which hot flue gases contact the pot helps to punch through a still
air
>> boundry layer so I wonder about the value of increasing dwell time, slowing
>> hot gases, as a big determinant of heat transfer. I don't know and the
>> perfect test might be to compare results from a straight skirt and your
>> spiral. I do know that the right sized gap has a tremendous effect on heat
>> transfer and that this gap is very small. Larry uses as a rule of thumb
>> keeping the same cross sectional area all through the stove so bigger pots
>> use smaller gaps.
>> 
>> Of course, the pot shape is a huge factor. A pot that touches more water
>> inside is better, therefore a large diameter pot with a little water in it
>> boils quickly. In our tests, big pots generally score higher than small
>> pots.
>> 
>> Could I then take this opportunity to forward a suggestion which Ron and I
>> tossed about on a train heading from Rugby to London? Let's form one center
>> of sanity in the bigger stove world here on the CREST list and all agree on
>> a pot size/amount of water that we all use in our tests! Then we can
compare
>> results of tests. Until we do so, this factor will confound comparisons.
>> 
>> At Aprovecho we now use a nine inch in diameter steel pot that is five
>> inches high. We use five pounds of water in it. But I'm perfectly happy to
>> switch to liters!!
>> 
>> If we establish the UNIVERSAL POT SIZE FOR TESTING/AMOUNT OF WATER we will
>> have done something that the befuddled stove world has not accomplished in
>> decades! Let's do it and maybe we'll force the rest of the stove world to
>> follow...
>> 
>> Best,
>> 
>> Dean
>> 
>> 
>
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>
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>


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