<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:x="urn:schemas-microsoft-com:office:excel" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=iso-8859-1"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:Wingdings;
panose-1:5 0 0 0 0 0 0 0 0 0;}
@font-face
{font-family:Wingdings;
panose-1:5 0 0 0 0 0 0 0 0 0;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0mm;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p.MsoPlainText, li.MsoPlainText, div.MsoPlainText
{mso-style-priority:99;
mso-style-link:"Plain Text Char";
margin:0mm;
margin-bottom:.0001pt;
font-size:10.5pt;
font-family:Consolas;
mso-fareast-language:EN-US;}
p.MsoNoSpacing, li.MsoNoSpacing, div.MsoNoSpacing
{mso-style-priority:1;
margin-top:5.0pt;
margin-right:0mm;
margin-bottom:5.0pt;
margin-left:0mm;
mso-add-space:auto;
font-size:11.0pt;
font-family:"Arial","sans-serif";
color:#1F497D;}
p.MsoNoSpacingCxSpFirst, li.MsoNoSpacingCxSpFirst, div.MsoNoSpacingCxSpFirst
{mso-style-priority:1;
mso-style-type:export-only;
margin-top:5.0pt;
margin-right:0mm;
margin-bottom:0mm;
margin-left:0mm;
margin-bottom:.0001pt;
mso-add-space:auto;
font-size:11.0pt;
font-family:"Arial","sans-serif";
color:#1F497D;}
p.MsoNoSpacingCxSpMiddle, li.MsoNoSpacingCxSpMiddle, div.MsoNoSpacingCxSpMiddle
{mso-style-priority:1;
mso-style-type:export-only;
margin:0mm;
margin-bottom:.0001pt;
mso-add-space:auto;
font-size:11.0pt;
font-family:"Arial","sans-serif";
color:#1F497D;}
p.MsoNoSpacingCxSpLast, li.MsoNoSpacingCxSpLast, div.MsoNoSpacingCxSpLast
{mso-style-priority:1;
mso-style-type:export-only;
margin-top:0mm;
margin-right:0mm;
margin-bottom:5.0pt;
margin-left:0mm;
mso-add-space:auto;
font-size:11.0pt;
font-family:"Arial","sans-serif";
color:#1F497D;}
p.MsoListParagraph, li.MsoListParagraph, div.MsoListParagraph
{mso-style-priority:34;
margin-top:0mm;
margin-right:0mm;
margin-bottom:0mm;
margin-left:36.0pt;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
span.PlainTextChar
{mso-style-name:"Plain Text Char";
mso-style-priority:99;
mso-style-link:"Plain Text";
font-family:Consolas;}
span.EmailStyle20
{mso-style-type:personal-compose;
font-family:"Calibri","sans-serif";
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri","sans-serif";
mso-fareast-language:EN-US;}
.MsoPapDefault
{mso-style-type:export-only;
mso-margin-top-alt:auto;
mso-margin-bottom-alt:auto;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:72.0pt 72.0pt 72.0pt 72.0pt;}
div.WordSection1
{page:WordSection1;}
/* List Definitions */
@list l0
{mso-list-id:556747327;
mso-list-type:hybrid;
mso-list-template-ids:259803286 1766892490 269025283 269025285 269025281 269025283 269025285 269025281 269025283 269025285;}
@list l0:level1
{mso-level-start-at:615;
mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Symbol;
mso-fareast-font-family:Calibri;
mso-bidi-font-family:"Times New Roman";}
@list l0:level2
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:"Courier New";}
@list l0:level3
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Wingdings;}
@list l0:level4
{mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Symbol;}
@list l0:level5
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:"Courier New";}
@list l0:level6
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Wingdings;}
@list l0:level7
{mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Symbol;}
@list l0:level8
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:"Courier New";}
@list l0:level9
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Wingdings;}
@list l1
{mso-list-id:1935941253;
mso-list-type:hybrid;
mso-list-template-ids:-351479900 1537253050 269025283 269025285 269025281 269025283 269025285 269025281 269025283 269025285;}
@list l1:level1
{mso-level-start-at:615;
mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Symbol;
mso-fareast-font-family:Calibri;
mso-bidi-font-family:"Times New Roman";}
@list l1:level2
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:"Courier New";}
@list l1:level3
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Wingdings;}
@list l1:level4
{mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Symbol;}
@list l1:level5
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:"Courier New";}
@list l1:level6
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Wingdings;}
@list l1:level7
{mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Symbol;}
@list l1:level8
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:"Courier New";}
@list l1:level9
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Wingdings;}
ol
{margin-bottom:0mm;}
ul
{margin-bottom:0mm;}
--></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-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Dear Thermally Active Friends<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Determining the thermal efficiency of a stove as a space heater or as a cooker:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The SeTAR <i>HPT</i> Spreadsheet calculates the thermal efficiency of a stove used as a space heater based on the elemental fuel composition (ultimate analysis), the stack temperature and gas composition.<span style='mso-fareast-language:EN-CA'><o:p></o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:EN-CA'><o:p> </o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:EN-CA'>It uses the Siegert Method of calculating thermal efficiency. This is standard in Germany and much of Europe. It considers the ‘chemical losses’ of CO not burning to CO2. It calculates using the HHV and considers that heat released combustion of Hydrogen in the fuel has produced water that was condensed and cooled to the ambient air (actually the stove air supply temperature).<o:p></o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:EN-CA'><o:p> </o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:EN-CA'>See Page 2/14 of <o:p></o:p></span></p><p class=MsoNormal><span style='mso-fareast-language:EN-CA'><a href="http://www.docstoc.com/docs/70550236/Enthalpy-of-Formation-Worksheet">http://www.docstoc.com/docs/70550236/Enthalpy-of-Formation-Worksheet</a> <o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>This document shows both outputs values for some realistic cases. See the difference between the ‘Standard’ efficiency as calculated in the USA and the ‘Siegert’ efficiency. The cause of the difference is that the calculation methods are quite different.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Normally the Siegert efficiency value is higher but you can see on pages 5/ and 9/14 that the Siegert calculated efficiency is lower than the Standard Efficiency when the stack temperature is high.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>In fact, the fuel heat number used in the US (in some industries) is <i>not</i> the LHV value which assumes that water vapour and gases are cooled by the heat exchanger to 100C and that heat was captured (the normal way to get LHV).<sup>1</sup><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Some industries use 150 C as the practical limit for extracting useable heat so the ‘loss’ is an additional 50° C for everything passing through the device. There are good (industrial) reasons for this, however there is obviously confusion caused when trying to decide which method has been applied by someone else.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The Siegert method is used in the <i>HTP</i> even if the instantaneous efficiency is different some of the time. With space heating stoves, sometimes the HHV is appropriate because the exhaust gases are condensing and going out as white ‘fog’, sometimes even running down as liquid inside the chimney (the black liquid that drops out) and sometimes it goes out as water vapour indicating that the LHV is appropriate. So a decision was taken to use the European Siegert method across the board for stating space heating efficiency.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Prof Philip Lloyd (Cape Town) has reported difficulty determining the thermal efficiency of ethanol stoves because of condensation of moisture taking place on the bottom of pots (HHV) early in the test but later this is not the case (LHV). However this situation being unusual, in general the LHV is used for cooking. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>In the case of cooking pots on stoves, the same <i>HTP</i> spreadsheet uses the LHV (in common with most protocols) because in the vicinity of the cooking region of most stoves the likelihood and frequency of moisture condensing on the pots throughout the cooking process is very low. If you were designing a condensing heat exchanger instead of cooking, the method should be appropriate to that case.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>In summary: the SeTAR <i>Heterogeneous Test Protocol</i> uses the Siegert method for determining the thermal efficiency as a space heater which means it uses the HHV of the fuel, and uses the standard LHV values when determining the efficiency of cooking over the fire.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>These efficiencies are separately reported on the spreadsheet.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Regards<o:p></o:p></p><p class=MsoNormal>Crispin<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><sup>1</sup> [Also see S Baldwin’s discussion of this in his 1987 book – I agree with his suggestion but it is not the standard method: it is that LHV values over-report the actual cooking efficiency of stoves by .06 MJ/kg of biomass fuels because of the enthalpy of gases between 100 C and the standard ambient air source temperature.]<o:p></o:p></p></div></body></html>