<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:st1="urn:schemas-microsoft-com:office:smarttags" xmlns="http://www.w3.org/TR/REC-html40"
xmlns:ns0="http://schemas.microsoft.com/office/2004/12/omml">
<head>
<meta http-equiv=Content-Type content="text/html; charset=utf-8">
<meta name=Generator content="Microsoft Word 11 (filtered medium)">
<!--[if !mso]>
<style>
v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style>
<![endif]--><o:SmartTagType
namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="PostalCode"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="State"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="City"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="place"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="Street"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="address"/>
<o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags"
name="PersonName"/>
<!--[if !mso]>
<style>
st1\:*{behavior:url(#default#ieooui) }
</style>
<![endif]-->
<style>
<!--a:link
{mso-style-priority:99;}
span.MSOHYPERLINK
{mso-style-priority:99;}
a:visited
{mso-style-priority:99;}
span.MSOHYPERLINKFOLLOWED
{mso-style-priority:99;}
p.MSOPLAINTEXT
{mso-style-priority:99;}
li.MSOPLAINTEXT
{mso-style-priority:99;}
div.MSOPLAINTEXT
{mso-style-priority:99;}
p.MSONOSPACING
{mso-style-priority:1;}
li.MSONOSPACING
{mso-style-priority:1;}
div.MSONOSPACING
{mso-style-priority:1;}
p.MSONOSPACINGCXSPFIRST
{mso-style-priority:1;}
li.MSONOSPACINGCXSPFIRST
{mso-style-priority:1;}
div.MSONOSPACINGCXSPFIRST
{mso-style-priority:1;}
p.MSONOSPACINGCXSPMIDDLE
{mso-style-priority:1;}
li.MSONOSPACINGCXSPMIDDLE
{mso-style-priority:1;}
div.MSONOSPACINGCXSPMIDDLE
{mso-style-priority:1;}
p.MSONOSPACINGCXSPLAST
{mso-style-priority:1;}
li.MSONOSPACINGCXSPLAST
{mso-style-priority:1;}
div.MSONOSPACINGCXSPLAST
{mso-style-priority:1;}
span.PLAINTEXTCHAR
{mso-style-priority:99;}
/* Font Definitions */
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:"Lucida Sans Unicode";
panose-1:2 11 6 2 3 5 4 2 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:Calibri;}
a:link, span.MsoHyperlink
{color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{color:purple;
text-decoration:underline;}
p.MsoPlainText, li.MsoPlainText, div.MsoPlainText
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:Calibri;}
span.PlainTextChar
{font-family:Calibri;}
p.msonospacing, li.msonospacing, div.msonospacing
{margin-top:5.0pt;
margin-right:0in;
margin-bottom:5.0pt;
margin-left:0in;
font-size:11.0pt;
font-family:Arial;
color:#1F497D;}
p.msonospacingCxSpFirst, li.msonospacingCxSpFirst, div.msonospacingCxSpFirst
{mso-style-type:export-only;
margin-top:5.0pt;
margin-right:0in;
margin-bottom:0in;
margin-left:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:Arial;
color:#1F497D;}
p.msonospacingCxSpMiddle, li.msonospacingCxSpMiddle, div.msonospacingCxSpMiddle
{mso-style-type:export-only;
margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:Arial;
color:#1F497D;}
p.msonospacingCxSpLast, li.msonospacingCxSpLast, div.msonospacingCxSpLast
{mso-style-type:export-only;
margin-top:0in;
margin-right:0in;
margin-bottom:5.0pt;
margin-left:0in;
font-size:11.0pt;
font-family:Arial;
color:#1F497D;}
span.EmailStyle20
{mso-style-type:personal-reply;
font-family:Arial;
color:navy;}
@page Section1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.Section1
{page:Section1;}
-->
</style>
<!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang=EN-US link=blue vlink=purple>
<div class=Section1>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Dear Crispin, <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>My GEK was painted bright fire engine red
with some special paint. The paint changed color from red to gray-black around
the lower area. What does that tell us? And can painted surfaces effect or be
good indicators of how hot a surface is(?) or the e value? <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Great info –thanks<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><st1:PersonName w:st="on"><font size=2 color=navy
face=Arial><span style='font-size:10.0pt;font-family:Arial;color:navy'>Frank</span></font></st1:PersonName><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<p class=MsoNormal><st1:PersonName w:st="on"><font size=2 color=navy
face=Arial><span style='font-size:10.0pt;font-family:Arial;color:navy'>Frank</span></font></st1:PersonName><font
size=2 color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'> Shields</span></font><font color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Control Laboratories, Inc.</span></font><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><st1:Street w:st="on"><st1:address w:st="on"><font size=2
color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>42 Hangar Way</span></font></st1:address></st1:Street><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><st1:place w:st="on"><st1:City w:st="on"><font size=2
color=navy face=Arial><span style='font-size:10.0pt;font-family:Arial;
color:navy'>Watsonville</span></font></st1:City><font size=2 color=navy
face=Arial><span style='font-size:10.0pt;font-family:Arial;color:navy'>, <st1:State
w:st="on">CA</st1:State> <st1:PostalCode w:st="on">95076</st1:PostalCode></span></font></st1:place><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>(831) 724-5422 tel</span></font><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>(831) 724-3188 fax</span></font><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><a href="mailto:frank@compostlab.com">frank@compostlab.com</a></span></font><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><a href="http://www.compostlab.com">www.compostlab.com</a></span></font><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Calibri><span style='font-size:
11.0pt;color:navy'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Calibri><span style='font-size:
11.0pt;color:navy'> </span></font><o:p></o:p></p>
</div>
<div>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-family:"Times New Roman"'>
<hr size=2 width="100%" align=center tabindex=-1>
</span></font></div>
<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
stoves-bounces@lists.bioenergylists.org
[mailto:stoves-bounces@lists.bioenergylists.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Crispin Pemberton-Pigott<br>
<b><span style='font-weight:bold'>Sent:</span></b> Wednesday, September 14,
2011 7:50 PM<br>
<b><span style='font-weight:bold'>To:</span></b> '<st1:PersonName w:st="on">Discussion
of biomass cooking stoves</st1:PersonName>'<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [Stoves] flames
touching pot</span></font><font size=3 face="Times New Roman"><span
style='font-size:12.0pt;font-family:"Times New Roman"'><o:p></o:p></span></font></p>
</div>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoPlainText><font size=2 face=Calibri><span lang=EN-CA
style='font-size:11.0pt'>Dear Paul and AJH<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 face=Calibri><span lang=EN-CA
style='font-size:11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoPlainText><font size=2 face=Calibri><span lang=EN-CA
style='font-size:11.0pt'>AJH >I don't for sure but dull red is around
600-700C for a black body, I'd guess stainless would be around 0.9 emissivity ,
so a bit hotter, of course the outside is losing heat by radiation, conduction
and convection so the other side of the steel can be hotter.<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'><o:p> </o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'><o:p> </o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>That would be a bit high for stainless
unless it is badly darkened. Before jumping in with a number I wondered if you
had checked a few values with a surface contact thermocouple. The low chrome
stainless steels darken quite a bit at high temp so the surface finish
dominates (it can still be shiny). Discoloured 400 series is still pretty low.<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'><o:p> </o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>Engineering toolbox says:<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>Values of </span></font><font size=4
color=black face="Lucida Sans Unicode"><span lang=EN-CA style='font-size:14.0pt;
font-family:"Lucida Sans Unicode";color:black'>ɛ</span></font><font
color=black><span lang=EN-CA style='color:black'><o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>Steel Oxidized
0.79<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>Steel Polished
0.07<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>Stainless Steel,
weathered 0.85<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>Stainless Steel,
polished
0.075<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>Stainless Steel, type
301
0.54 - 0.63<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>Steel Galvanized
Old
0.88<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>Steel Galvanized
New
0.23<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'><o:p> </o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>I have attached a photo of a fuel hopper
made of 3CR12 which has a rough surface but is reasonably white. The </span></font><font
size=4 color=black face="Lucida Sans Unicode"><span lang=EN-CA
style='font-size:14.0pt;font-family:"Lucida Sans Unicode";color:black'>ɛ</span></font><font
color=black><span lang=EN-CA style='color:black'> is about 0.75 maybe less.<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'><o:p> </o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>I am speaking up on the subject because it
can be quite dangerous for children if there are stainless steel components of
a stove that can be touched. They have such difficulty getting rid of heat that
the temperature is very high before it does so. On the other hand the inability
to radiate away significant heat and the poor conduction coefficient (about ½
that of mild steel) means stainless is a pretty good insulating and therefore
combustion chamber material if it is not further insulated on the back.<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'><o:p> </o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>In the attached photo of a BLDD5.2 from
the SeTAR Centre the temperature inside is far above the outside surface in spite
of the significant heat radiating away from the outside (making it visible to
the camera). So it has the advantages of being strong, corrosion resistant, hot
and insulating with a poor radiation coefficient. This combination works best
when the whole system is small and when the oxygen level in the hot region is
low.<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'><o:p> </o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>We make bread ovens from stainless steel
with a bright finish and the </span></font><font size=4 color=black
face="Lucida Sans Unicode"><span lang=EN-CA style='font-size:14.0pt;font-family:
"Lucida Sans Unicode";color:black'>ɛ</span></font><font color=black><span
lang=EN-CA style='color:black'> is 0.4 when it is new.<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'><o:p> </o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>For those who are not familiar with the
term “</span></font><font size=4 color=black face="Lucida Sans Unicode"><span
lang=EN-CA style='font-size:14.0pt;font-family:"Lucida Sans Unicode";
color:black'>ɛ</span></font><font color=black><span lang=EN-CA
style='color:black'>” it is used in the formula that calculates how much heat
radiates away from a surface into the surrounding environment. It is called
‘grey body radiation’ because things are not truly black. The formula is </span></font><font
size=4 color=black face="Lucida Sans Unicode"><span lang=EN-CA
style='font-size:14.0pt;font-family:"Lucida Sans Unicode";color:black'>ɛ</span></font><font
color=black><span lang=EN-CA style='color:black'> * 5.6703*10<sup>-8</sup>*
Temperature in Deg Kelvin * surface area in sq metres.<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'><o:p> </o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>If you want to try something interesting,
make up a case with an </span></font><font size=4 color=black
face="Lucida Sans Unicode"><span lang=EN-CA style='font-size:14.0pt;font-family:
"Lucida Sans Unicode";color:black'>ɛ</span></font><font size=4 color=black><span
lang=EN-CA style='font-size:14.0pt;color:black'>,</span></font><font
color=black><span lang=EN-CA style='color:black'> a temperature and an area.
Then lower the </span></font><font size=4 color=black face="Lucida Sans Unicode"><span
lang=EN-CA style='font-size:14.0pt;font-family:"Lucida Sans Unicode";
color:black'>ɛ</span></font><font color=black><span lang=EN-CA
style='color:black'>. You will see the heat radiating drop proportionally. Then
increase the temperature until the radiated heat equals the original case. You
will be surprised. A low emissivity surface has to be a lot hotter to radiate
the same energy as a high emissivity one. That is why cast iron stoves are
painted and polished flat black. In real life the convective heat transfer
increases with the temperature as well so it is not so straight forward to get
accurate numbers.<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'><o:p> </o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>Regards<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'>Crispin<o:p></o:p></span></font></p>
<p class=MsoPlainText><font size=2 color=black face=Calibri><span lang=EN-CA
style='font-size:11.0pt;color:black'><o:p> </o:p></span></font></p>
</div>
</body>
</html>