[Stoves] Water heating fuel efficiency formula

[Jock Gill]

Gents,

While efficiency is certainly an interesting concept, it will be deeply influenced by the shape of the pot as well as the location of the pot.  I find that a flat bottom container set inside a closed kettle (domed container such as a modified Weber grill), boils water beautifully. The benefit is that ALL surfaces of the pot and the top surface of the water are exposed to temperatures above 350 degrees F.  The temperature of the exhaust gases exceeds 400 degrees F.  

Further, set to the side, not directly over the heat source, I can simmer the water while I cook over the heat source.  Or I can boil water over the heat source and slow cook food at about 350 degrees F in the off center portions of the grill.

How would we measure the efficiency of such a system, an iCan TLUD, that provides useful heat for about 70 minutes from about 3 pounds of wood pellets and also harvests almost 20% of the weight of the feed stock as charcoal?

I note that the system I use does not deposit soot on either the pots or the food.  So clean up is much easier. Pots can stay shiny after use.  I will have a 12 page PDF on all of this next week.

In the end, I think cooks are going to be more interested in the cooking methods and results than just about anything else.  If we want a stove to be adopted, the operation of the stove has to be straight forward and the food simply has to taste significantly better than the alternatives.  Have we yet considered taste tests as a crucial metric for evaluating stoves?  And, of course, I would also like to see gardening tests done with the residues created by stoves.  Are some residues more valuable than others? What are the differences?  Are residues waste products of low value or are they high value co-products?

Just what are the benefits that will convince a person to adopt a new cooking technology? Are they compelling enough to convince a customer at the top of the pyramid - at least for back yard and deck cooking?

Regards,

Jock

Jock Gill
P.O. Box 3
Peacham,  VT 05862

Cell: (617) 449-8111

:> Extract CO2 from the atmosphere! <:

Sent from my iPad

> On Oct 3, 2013, at 3:07 AM, ajheggie at gmail.com wrote:
> 
> [Default] On Sun, 29 Sep 2013 14:41:32 -0400,"Lanny Henson"
> <lannych at bellsouth.net> wrote:
> 
>> I need the formula or spread sheet, for fuel efficiency, for heating water, 
>> considering the moisture content of wood,  and using red oak as fuel. Not a 
>> water boiling test with simmering,  just a water heating test.
> 
> Lanny 
> 
> What form do you want this to take?
> 
> My guess is red oak will have a calorific content of around the 18.6
> MJ per kilo average suggested for most biomass. When you burn it
> completely it gives off CO2 and water. All the water, both the
> original moisture content and the water formed from oxidising the
> hydrogen atoms in the fuel, in the exhaust contains 2.3MJ of latent
> heat and the sensible heat from the exhaust temperature. This heat in
> water vapour and the sensible heat of the other exhaust gasses, mostly
> nitrogen, any remaining oxygen from the excess air and CO2, is waste
> heat, the other waste heat is the heat conducted, radiated and
> convected from the stove body. The remainder, the usable heat is what
> gets into the pot. 
> 
> The simplest conversion of the potential heat in the wood to usable
> heat in the pot is to weigh the wood used, calculate its heat value
> and measure the rise in temperature of the pot contents and calculate
> the heat input. Divide the first by the second value and you have an
> overall wood to pot efficiency as a first approximation.
> 
> Beyond that you get into the realms of interminable arguments about
> whether to allow for residual energy in any char left and how many
> fairies can dance on a pin head.
> 
> AJH
> 
> _______________________________________________
> Stoves mailing list
> 
> to Send a Message to the list, use the email address
> stoves at lists.bioenergylists.org
> 
> to UNSUBSCRIBE or Change your List Settings use the web page
> http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org
> 
> for more Biomass Cooking Stoves,  News and Information see our web site:
> http://stoves.bioenergylists.org/
>