low power testing

["Dean Still" <dstill@epud.net>]

Dear Friends,

Dr. Karve writes:

Experience with
>solar cookers and also with the hot box show, that one does not even
require
>a temperature of 100 degrees Celsius for cooking.  With the pot just
>simmering, there would be very little evaporation, and, as you have rightly
>mentioned, the efficiency of the stove would be near zero, and yet the
>cooking process would be completed with very little fuel

In my limited experience, a pot when simmering, needs to be kept close to
boiling temperatures for food to cook in normal time periods. Hayboxes need
to keep as close to boiling temperatures as possible since cooking almost
ceases to occur below 170F. When the water is kept near to boiling, there is
a lot of evaporation, not a little. If the temperature dropped significantly
so that there was little evaporation, cooking times greatly increase which
requires a greater input of fuel.

Measuring latent heat scores high if the stove/pot combination is good at
sending just the right amount of heat to keep the pot gently boiling. So the
stove needs to be able to give off adjustable amounts of heat. Needs to have
good turn down. Tami is so right when she says that the wasteful part of a
stove would be blowing too much heat past the pot. (Eindhoven charts exist
that describe the optimal relationship and I'll try to look this up.)The
stove/pot combo scores badly as well if it delivers too little heat because
water temperatures fall and there is less evaporation. Wisps of steam start
happening around 140F and build up to raging plumes at 212F. So I like the
steam measuring test because if I just measure sensible heat the stove is
not tested for ability to adjust heat delivered. On the other hand,
measuring the water temperature rise is entirely sensible.

Best,

Dean




-
Stoves List Archives and Website:
http://www.crest.org/discussion/stoves/200202/
http://crest.org/discussiongroups/resources/stoves/ (Under construction)
http://www.ikweb.com/enuff/public_html/Stoves.html (Original)

Stoves List Moderators:
Ron Larson, ronallarson@qwest.net
Alex English, english@adan.kingston.net
Elsen L. Karstad, elk@wananchi.com www.chardust.com

List-Post: <mailto:stoves@crest.org>
List-Help: <mailto:stoves-help@crest.org>
List-Unsubscribe: <mailto:stoves-unsubscribe@crest.org>
List-Subscribe: <mailto:stoves-subscribe@crest.org>

Sponsor the Stoves List: http://www.crest.org/discuss3.html
-
Other Biomass Stoves Events and Information:
http://www.bioenergy2002.org
http://www.crest.org/articles/static/1/1010424940_7.html Bioenergy
http://www.crest.org/articles/static/1/1011975339_7.html Gasification
http://www.crest.org/articles/static/1/1011975672_7.html Carbon

For information about CHAMBERS STOVES
http://www.ikweb.com/enuff/public_html/Chamber.htm