Re: LETS ADOPT A UNIVERSAL POT

[Reedtb2@cs.com]

Dear Dean and All:

I like the idea of a universal stove test with a prescribed pot size.  However, I was puzzled during my visit that you boiled 5 lb of water when so many other people (and therefore we do it) seem to use 1 liter.  

I vote for 1 liter because

The test is faster
It is enough to do most cooking since the steam condenses on the food (when there is a lid)
It is easier to divide by 1,000 cm3 than 5 lb or 2.72 liters.

Ron asked this morning whether 3 minutes to boil 1 liter was a record.  Possibly.  We most always boil in less than 7 minutes, sometimes 5 minutes on the various forced draft stoves. FOr water at 20 C boiling at 100 C, 5 minutes to boiling implies a heat transfer rate of (1 liter X 4.18 kJ/liter-degreeX80degrees/300 sec) 1.11 kJ/s = 1.11 kW, a respectable heat transfer.  (The small element on an electric stove consumes 1.5 kW, the large 2.5 kW).  

I hope you are taking a census on the answers, having asked a good question.

Yours truly,          TOM REED             BEF STOVEWORKS

In a message dated 1/5/02 12:25:15 PM Mountain Standard Time, dstill@epud.net writes:


> 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