[Stoves] Pot shells / Fin shells

Sun Jul 28 16:14:38 CDT 2013

Dear Lanny

The problem is the missing figure is the mass of fuel when the pot as boiled
so I can't get an efficiency without making some (big) guesses.

If the energy needed to simmer the rice for 30 minutes is 20% of the boiling
energy, the system efficiency (which is the analogy of fuel efficiency) is
34%, conditioned on the following:

If the charcoal remaining is useable in the next fire, it can be treated as
'unused fuel'. If you want an accurate figure, you would have to use this
duel in a new fire and get the performance so that the amount of char
remaining is the same as what you put in during that burn. 

The 34% figure assumes the char is not burnable in the next fire.

If it is (all of it) the system efficiency is 51% based on the simmering
assumption.

It should be remembered that the thermal efficiency should consider the
thermal mass of the pot (mass x specific x change in temperature. If it
does, the reported figure will be higher.

Regards

Crispin

From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Lanny Henson
Sent: Sunday, July 28, 2013 3:37 PM
To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] Pot shells / Fin shells

Well I had 186 LB of water and rice, the rice was 50 lb. 

Rice has a specific heat capacity of about .33 which is about the same as
16.5 of water so deduct 33.5 from 186 for a mass of about 152.5 lb water
equivalent.

I started with 15 LB. of wood and had 2.95 LB. left over = 12.05 LB. of wood
used, and there was 1.5 LB. of charcoal left.

The simmer time was about 30 min.

The wrapper is 60" x and the vat is 48" long . I estimate the water was
contacting about 36" of the 60" wrapper so the contact area was about 12 sq.
ft.

Does that give you the numbers you need?

Lanny

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