[Stoves] A few stove questions

[frank]

Dear Per-Einar Rosenhave,

Thanks for this info. Not sure what I was thinking but things have 
clicked and now it all seems so simple. The 2260 J/g is a 'rate' the 
water leaves the pot and the energy it takes with it.

As for the heat capacity of water it is 4.186 J/C/g reported in this 
stove book. Meaning for every increase in temperature there needs impute 
in addition to what is already there of 4.186 J/g of water? OR does it 
mean there is 4.186 J/g energy in the gram of water and  going from 55 
deg to 56 deg it stays about the same. Only going from 4.186 to 4.219 
with a temperature increase of 85 deg. (15 to 100)?


Thanks again.
Frank





Per-Einar Rosenhave wrote:

>Dear Frank,
>
>The specific heat capacity of water is 4.219 [kJ/kgK] at 100 deg. Celsius
>and 1 atmosphere. 4.186 [kJ/kgK] is correct for 15 deg. Celsius.
>
>If water at a pressure of 1 atmosphere is at 100 Deg. Celsius it is at
>boiling point. Any additional energy input will be used for evaporating the
>water. The temperature will be constant but the water will change it's phase
>from liquid to gas.
>
>The 2260 J/g you are referring to is the Latent heat of evaporation (2,270
>kJ/kg).  So put short, - for every 2270 J you add to water at boiling point
>1 gram of it will evaporate.
>
>See also:
>http://www.engineeringtoolbox.com/water-thermal-properties-d_162.html
>
>
>With kind regards 
>Per-Einar Rosenhave, Associate Professor 
>Vestfold University College, Faculty of Maritime Education 
>Norway Please visit: www.tunoshisho.org/
>
>
>-----Original Message-----
>From: stoves-bounces at listserv.repp.org
>[mailto:stoves-bounces at listserv.repp.org] On Behalf Of frank
>Sent: 06 March 2008 18:34
>Cc: Discussion of biomass cooking stoves
>Subject: [Stoves] A few stove questions
>
>Dear stovers,
>I have a few questions:
>
>Does water at boiling have 1561 J/g energy? That is 4.186 J/C/g starting 
>at -273 deg C (0 deg K).and going to + 100 deg C?
>
>If you need an additional 2260 J/g after the water reaches 100 deg C to 
>bring it to a boil that is like bringing the temperature to (2260 / 
>4.186) 540 deg. C but water does not go above 100 deg C (?). How is this 
>energy stored until it builds up to boiling point? Where is it?
>
>If measuring the temperature along a very tall stack is there a place 
>where the temperature drops to 100 deg C (but still has the +2260 J/g 
>energy) and the water condenses releasing the +2260 J/g so the 
>temperature goes up?
>
>If the fire under Lannys stove is of the size that before the heat 
>exits  it is reduced (fins and length) to below 100 deg C.  will the 
>released heat be included in heating the water and we should go by the 
>HHV and not the LHV of the wood? And is this a goal of producing the 
>'perfect' stove?
>
>
>Thanks again,
>Frank
>
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-- 
Frank Shields
Soil Control Lab
42 Hangar way
Watsonville, CA  95076
(831) 724-5422 tel
(831) 724-3188 fax
frank at compostlab.com
www.compostlab.com