[Stoves] Energy calcs.

[Frank Shields]

oH my - A QUIZE here in front of everyone!

Enthalpy of liquid water at 95c is 399 kj/kg
Enthalpy of vapor water at 100c is 2675.6 (so it must be a little less for
95c)

So it takes a little less than 2277 energy kj/kg?
If enthalpy of water vapor is 2546 at 25c and 2676 at 100c So it takes 1.72
j/c/g to heat the water vapor?
So 2277 - (1.72 X 5) = 2268?

Thanks
 
Frank




-----Original Message-----
From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Crispin Pemberton-Pigott
Sent: Monday, October 15, 2012 11:06 AM
To: Stoves
Subject: Re: [Stoves] Energy calcs.

Dear Frank

You are right about the 2676 but remember that the heat taken to evaporate
water AT 0 deg is only 2501. I have questioned the difference in the past
but forgot the reason. 

HHV calcs may use that number (?) but I think it is cooled to 20 not 0. You
can check. 

Here is a question for you: if the local boiling point is 95 deg C, what is
the local latent heat of evaporation?

Regards
Crispin jumping in Jakarta
-----Original Message-----
From: "Frank Shields" <frank at compostlab.com>
Date: Mon, 15 Oct 2012 09:04:58
To: <crispinpigott at gmail.com>; 'Discussion of biomass cooking
stoves'<stoves at lists.bioenergylists.org>
Subject: RE: [Stoves] Energy calcs.

Dear Crispin, 
So its 2676 (enthalpy vapor @100c) - 419 liquid at 100c = 2257.   
I get confused when there is no 'liquid' water as the H is in the wood
structure.

I realize all this in 'real world'  differs with  site specific. I will use
the 2257 value and thank you all (again) for reviewing this. Seems if I
leave it for a year I need to start over in understanding it. 

Thanks

Frank





-----Original Message-----
From: Stoves [mailto:stoves-bounces at lists.bioenergylists.org] On Behalf Of
Crispin Pemberton-Pigott
Sent: Sunday, October 14, 2012 4:33 PM
To: Stoves
Subject: Re: [Stoves] Energy calcs.

Frank, that water vapour number must be relative to some normative
temperature. It doesn't match the usual numbers. 

It it was relative to condensed water at 100 C it would be 2257. If relative
to water at 0 C it would be 2501. 

486 g x 2257 = the latent heat of condensation which is what I would
subtract from the HHV (bomb calorimeter). 

It is not absolutely correct but that is what people have agreed to do. For
almost all biomass the deduction per dry kg will be 1.32 MJ per dry ash-free
kilogram. 

Regards
Crispin in the perpetual summer of Singapore -----Original Message-----
From: "Frank Shields" <frank at compostlab.com>
Sender: "Stoves" <stoves-bounces at lists.bioenergylists.org>
Date: Sun, 14 Oct 2012 12:58:58
To: 'Discussion of biomass cooking stoves'<stoves at lists.bioenergylists.org>
Reply-To: Discussion of biomass cooking stoves
	<stoves at lists.bioenergylists.org>
Subject: [Stoves] Energy calcs.

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