[Stoves] Water heating fuel efficiency formula

[Lanny Henson]

AJH,
Are we mixing calories per gram and kJ per kilogram
I was under the impression that the specific heat of water was 1 calorie per 
gram and all other materials was in relationship to water so 316 ss at .5 is 
half that of water?
Lanny
----- Original Message ----- 
From: <ajheggie at gmail.com>
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>
Sent: Saturday, October 05, 2013 9:11 AM
Subject: Re: [Stoves] Water heating fuel efficiency formula


> [Default] On Fri, 4 Oct 2013 18:14:31 -0400,"Lanny Henson"
> <lannych at bellsouth.net> wrote:
>
>>2- A few points I am still trying to understand is how to calculate the 
>>pot
>>mass since metal has a different specific heat than water. I am using a 
>>316
>>stainless pot so I am using .5 as a factor. Is that about right?
>
> Specific heat of water is 4.187kJ/kg, a quick google suggests 316 ss
> is 0.5kJ/kg so it's less than water by a factor of ~10 but of course
> it weighs 8 times as much so they are similar on a volume basis.
>
>>3- Also I still need the formula for calculating the loss from woods
>>moisture content. I an drying a batch of wood as I type. Before the 
>>moisture
>>here in NW Georgia USA has been but we have had a wet season and the last
>>batch was 14.5%. Wood sure does burn well at 14.5% in my stove.
>>4- Another confusing point is the difference between net and gross 
>>calorific
>
>
> I addressed these two points in my earlier post. Weigh the wood first,
> then dry it at 110-125C until it loses no further weight. Reweigh it
> and subtract the last figure from the first to get the water content.
>
> As a rule of thumb the useable heat (Lower Heating Value), net of
> losses due to latent heat of vaporisation, is the dry weight times the
> calorific value for dry wood (18.6MJ/kg its LHV) minus about 2.7MJ/kg
> for the water content calculated from the above.
>
> AJH
>
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