[Stoves] Calculation help

[Frank Shields]

Dear Crispin, stovers,

I realize for biomass the difference between J used in evaporation (2256
j/g) and energy in water at 450c (2854 j/g) is well within the 'noise' of
biomass fuel so doesn't matter which one we use. And if we all are using the
2256 value that is what I will do. But it seems since the hydrogen in
biomass never is in a liquid state or  never even water vapor before going
from solid state to water vapor at ~450  that we should be using 2854 ((2256
+(1.72 X 350)). if we think none of it is condensed to release its energy
before blowing past the pot of water. 

At least that is the way I think about it mow. 

For the LHV calculation of methane;  I see wiki says the HHV is product of
water in liquid form and LLV is product of water in vapor form - same way
you calculate biomass. But, of course water is never in the liquid form
(until it completely condenses at below 100c.). Hydrogen is held by carbon
or then water vapor at the combustion temp. so I am surprised they calculate
(estimate) it the way they do. 

So I will not bother anyone with more questions, will calculate as everyone
does (subtract energy from water liquid to water vapor) and just think I
don't understand what really goes on or believe that everyone has just
agreed to use this method as an estimate to LHV. 

Appreciate your help and  time.


Regards
Frank


Frank Shields
42 Hangar Way
Watsonville,  CA  95076
(831) 724-5244 tel
(831) 724-3188 fax
frank at bioCharlab.com








-----Original Message-----
From: stoves-bounces at lists.bioenergylists.org
[mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of Crispin
Pemberton-Pigott
Sent: Friday, January 06, 2012 7:00 PM
To: Discussion of biomass cooking stoves
Subject: Re: [Stoves] Calculation help

Yes that us the correct enthalpy but not all of it is 'lost', by definition.
The definition of 'lost' is taken to mean 'unusable heat', not actual
losses. 

Any gas below 100 C is not going to boil much water so it is considered lost
if below that temperature. 

So be careful when calculating the actual heat in something (referenced to 0
C) and losses. Usually LHV is the usable heat above 100 C for most things
and above 150 for commercial heat exchangers in the USA. 

Regards
Crispin
-----Original Message-----
From: "Frank Shields" <frank at compostlab.com>
Sender: stoves-bounces at lists.bioenergylists.org
Date: Fri, 6 Jan 2012 14:12:25
To: 'Discussion of biomass cooking stoves'<stoves at lists.bioenergylists.org>
Reply-To: Discussion of biomass cooking stoves
	<stoves at lists.bioenergylists.org>
Subject: Re: [Stoves] Calculation help

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