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<DIV><FONT face=Arial>Dear Tom and Frank</FONT></DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px"
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=tmiles@trmiles.com href="mailto:tmiles@trmiles.com">Tom Miles</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=stoves@lists.bioenergylists.org
href="mailto:stoves@lists.bioenergylists.org">'Discussion of biomass cooking
stoves'</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, December 20, 2011 8:54
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [Stoves] Water vapor calc.</DIV>
<DIV><BR></DIV>
<DIV class=WordSection1>
<P class=MsoNormal>Dear Stovers,<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>A few questions if you don’t mind. <o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>Enthalpy of water is 104.73 kj/kg at 25 deg. C</P>
<P class=MsoNormal> </P>
<P class=MsoNormal><FONT face=Arial><FONT size=3># Enthalpy is simply the
total energy content of the fluid with 0 C as the reference. (Or 32 degrees F)
The Joule units mask the simplicity: the reality is that 104.73 kJ/kG = 25,015
calories/kG, which simplifies to 1 calorie per gram per degree C , over 25
degrees C.</FONT></FONT></P>
<P class=MsoNormal><FONT size=3 face=Arial>This is the "Sensible Heat" of
liquid water, also equal to 1 BTU per pound per degree F</FONT></P>
<P class=MsoNormal><FONT size=3 face=Arial></FONT> </P>
<P class=MsoNormal>We need to add 4.186 kj/kg/deg. C (4.186 X 75) 314 to equal
419 to reach 100 deg. C</P>
<P class=MsoNormal> </P>
<P class=MsoNormal><FONT face=Arial><FONT size=3># 4.186 Joules = 1 Calorie.
75 degree rise requires 75 calories per gram.</FONT></FONT></P>
<P class=MsoNormal><FONT size=3 face=Arial></FONT> </P>
<P class=MsoNormal>We need to add (2675 – 419) =2256 kj/kg to get to a vapor.
And have enthalpy of 2675 kj/kg at 100 deg. C. </P>
<P class=MsoNormal> </P>
<P class=MsoNormal><FONT face=Arial><FONT size=3># This is the "Heat of
Vaporization of Water", or the "Latent Heat" associated with the change in
phase from liquid to vapor. </FONT></FONT></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>But then the water vapor goes up to 400 deg. C in a stack.
<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>So we add 1.72 kj/kg / deg. C or 300 X 1.72 = 516. So
516 + 2675 = 3191 kj/kg in the water vapor at 400 deg C. (?)</P>
<P class=MsoNormal><o:p><FONT size=3 face=Arial></FONT></o:p> </P>
<P class=MsoNormal><o:p><FONT size=3 face=Arial># This is the "Sensible Heat
of Water Vapor". </FONT></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>When the vapor cools off it releases a lot of energy. Its
interesting to me that water vapor at 25 deg. C has so much more energy than
water in a liquid! </P>
<P class=MsoNormal> </P>
<P class=MsoNormal><FONT face=Arial><FONT size=3># Yes. The Vapor at 25 C
contains the "Heat of Vaporization" of the water.<o:p></o:p></FONT></FONT></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>How does humidity calculate into all this? </P>
<P class=MsoNormal> </P>
<P class=MsoNormal><FONT face=Arial><FONT size=3># Humidity generally refers
to the amount of water vapor in the air. When water vapor is added to 1 pound
of dry air, there comes a point where it cannot hold any more without
condensing. The "Relative Humidity", RH is then 100%. If teh air only had 75%
of teh amount of water it could hold, then the RH would be
75%.</FONT></FONT></P>
<P class=MsoNormal> </P>
<P class=MsoNormal><FONT size=3 face=Arial>Hope this helps.</FONT></P>
<P class=MsoNormal> </P>
<P class=MsoNormal><FONT size=3 face=Arial>Best wishes,</FONT></P>
<P class=MsoNormal> </P>
<P class=MsoNormal><FONT size=3 face=Arial>Kevin</FONT> </P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>Thanks<o:p></o:p></P>
<P class=MsoNormal>Frank<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal>Frank Shields<o:p></o:p></P>
<P class=MsoNormal>42 Hangar Way<o:p></o:p></P>
<P class=MsoNormal>Watsonville, CA 95076<o:p></o:p></P>
<P class=MsoNormal>(831) 724-5244 tel<o:p></o:p></P>
<P class=MsoNormal>(831) 724-3188 fax<o:p></o:p></P>
<P class=MsoNormal>frank@bioCharlab.com<o:p></o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P>
<P class=MsoNormal><o:p> </o:p></P></DIV>
<P>
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<P align=left color="#000000" avgcert??>No virus found in this
message.<BR>Checked by AVG - <A
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Database: 2109/4692 - Release Date: 12/20/11</P></BLOCKQUOTE></BODY></HTML>