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<DIV><FONT face=Arial>Dear Crispin</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial>Thanks for your comprehensive reply! I fully agree with
all your comments, except for those which I extract as follows:</FONT></DIV>
<DIV><FONT face=Arial></FONT> </DIV>
<DIV><FONT face=Arial><STRONG>1</STRONG><EM>: <SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN></EM><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext"><EM>Also, the
maximum heat input rate to the pot, i.e. "pot power", will have an effect on
the required TDR.</EM> </SPAN><SPAN
style="COLOR: windowtext"><o:p></o:p></SPAN>
<DIV>
<P class=MsoNormal><SPAN style="COLOR: windowtext"><EM> </EM></SPAN><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><EM>Aha.
Well this is not the case. The definition of the turn down is not the firepower,
it is the heat gained by the pot. Interestingly, there are major outcomes from
this conceptual difference. The WBT’s classically observed the fire but people
do not cook with the heat of the fire, only the part which gets to the pot. As
you have observed, the heat transfer efficiency varies with firepower and
therefore stating a minimum TDR does not really say anything about the firepower
involved, only the cooking power.</EM></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><EM></EM></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
face=Arial><FONT size=3><STRONG># What I was getting at here is if the stove was
"high powered" to rate well in a "Water Boiling Test", it may be "over-powered"
for what is needed to cook most foods. </STRONG></FONT></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><STRONG><FONT
size=3 face=Arial>Are we "on the same page" now? :-)</FONT></STRONG></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
face=Arial><FONT size=3><STRONG></STRONG></FONT></FONT></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
face=Arial><FONT size=3><STRONG>2:</STRONG><FONT color=#000000> <EM> >
</EM></FONT><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext"><EM>1: For
most efficient cooking, and to reflect most common cooking practises, the pot
should be covered.<o:p></o:p></EM></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p><STRONG> </STRONG></o:p></SPAN><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><STRONG><EM>That
is not relevant to the TDR, though an important programmatic
consideration.</EM></STRONG></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><STRONG><EM><o:p></o:p></EM></STRONG></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><STRONG><o:p><FONT
size=3 face=Arial># Consider two WBT Tests... one with a cover, and one with no
cover, on the same stove. The same amount of "power to the pot" will show a
higher "pot power" when covered, than when not covered, because of extra losses
from the uncovered pot. If the stove was subsequently modified so that "covered
pot" had the same "time to boil", its actual "heat to the pot" would be less
than the "heat to the uncovered pot." Thus, the covered pot would be less likely
to be "overpowered, in relation to the actual energy required for maximum
cooking. Accordingly, the covered pot would require a lower turn-down ratio than
would an uncovered pot, in that most cooking is done with a covered
pot.</FONT></o:p></STRONG></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><STRONG><o:p><FONT
size=3 face=Arial>Does that make sense?</FONT></o:p></STRONG></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><STRONG><o:p></o:p></STRONG></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p><FONT
size=3 face=Arial><STRONG>3:</STRONG> <SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN><EM><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">3: .A stove heating
a covered pot will require a larger TDR than a stove heating an open top pot
with no cover.</SPAN><SPAN style="COLOR: windowtext"><o:p></o:p></SPAN></EM></P>
<DIV>
<P class=MsoNormal><EM><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d"><o:p> </o:p></SPAN><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">This
is debatable and so far I am not convinced<STRONG>.</STRONG></SPAN></EM></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><STRONG><FONT
size=3 face=Arial># I can see </FONT> <FONT face=Arial><FONT size=3>why you
found it "debateable" and why you were "unconvinced"... I think I had my
conclusions reversed, as per explanation in 2: above. I presently feel the
correct statement should be:</FONT></FONT></STRONG></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><EM><FONT color=#000000><STRONG>"A stove heating a covered pot
will require a LOWER TDR than a stove heating an open top pot with no
cover."</STRONG></FONT></EM></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><FONT color=#000000><STRONG>Does that make better sense
now?</STRONG></FONT></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><FONT color=#000000></FONT></FONT></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><FONT color=#000000>4: <EM>><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">4: A stove with
"high pot power input" will require a larger TDR than a pot with a lower "pot
power input."</SPAN><SPAN style="COLOR: windowtext"><o:p></o:p></SPAN></EM></P>
<DIV>
<P class=MsoNormal><EM><SPAN
style="COLOR: #1f497d"><o:p> </o:p></SPAN><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">This
is a no-no because to embed the concept into a Standard means interfering with
preferences of the manufacturer and customer. The deal is between the buyer and
the provider, not the regulator. The regulations are there to protect the
customer and to label a product as being able to perform certain things, such as
to deliver a locally acceptable water boiling rate in a pot with a diameter of
150mm or 300mm (as per the label on the product). The customer knows full well
that a stove that cooks ‘well’ with a 250mm diameter pot will have problems
getting the same cooking experience out of a 400mm diameter pot. What is not
permissible is to have a manufacturer claim that the product ‘cooks well’ with a
400 when a test of the heat transfer rate shows it will only do so if the pot is
about 250 in diameter.</SPAN></EM></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
face=Arial><FONT size=3><STRONG># I think my >4 statement above is correct,
based on the fact that 'high powered" stove will have a greater excess of power
above that required for normal "maximum required cooking power." The
presumption is that "high power is good" for fast boiling, but that it is bad
because of providing excess power above that required for maximum cooking
effect. In your note to Paul and Lanny on 4 May, it appears that:
</STRONG></FONT></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><STRONG>* 2 watts/square cm. is good for a maximum water
boiling requirement</STRONG></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><STRONG>* 1 watt/square cm is the "normally required
maximum power input, for actually cooking"</STRONG></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><STRONG>* 1/2 watt/square cm is an acceptably "low cooking
heat"</STRONG></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><STRONG>This being the case, why not simply do the test with
whatever pot diameter is chosen, and then calculate back to "Actual watt power
per square cm into the pot", and compare "Actual" with the Absolute Standards"
of 2,1,and 1/2 watts/square cm, apparently required for "good cooking and good
cooking control"? Tests would be run to determine:</STRONG></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><STRONG>a: Stove performance at maximum power input to the pot
when boiling water</STRONG></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><STRONG>b: Stove performance at 2 watt/square
cm input to the pot when boiling water</STRONG></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><STRONG>c: Stove performance at 1 watt/square
cm "normal maximum food cooking power"</STRONG></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"></SPAN><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><STRONG>d: Stove performance at 1/2 watt/square
cm "normal minimum food cooking power" </STRONG></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><STRONG>Input fuel consumption, health parameters, and safety
parameters would also be measured. If the 2,1, and 1/2 numbers were a bit off,
they could easily be changed in the future, with the same test
protocol.</STRONG></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial></FONT></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><STRONG>5:</STRONG> <EM><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">Knowing the rate of
fuel burning at that time enables calculation of the required TDR. </SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d"><o:p></o:p></SPAN></EM></P>
<P class=MsoNormal><EM><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">The
rate of mass loss is one thing, what is burning is quite another. Frank and I
have been discussing how to refine that! It is not so simple with biomass, and
is much more difficult it there is a lot of char involved, but not
impossible.<o:p></o:p></SPAN></EM></P></FONT></SPAN></DIV></FONT></FONT></SPAN>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><EM></EM></FONT></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><FONT
size=3 face=Arial><STRONG># If you knew the "total energy in the fuel charge, at
the start", and the energy remaining in the fuel after the test is
complete, there may be an error in the absolute sense as a result of
pro-rating energy consumed over the burn time, but the error would be
consistent. It would thus be fair to all stoves, and should thus give a
repeatable ranking of all stoves. Is there a better way to do things than
weighing the fuel as it disappears, and assuming that "energy release is
proportional to loss of fuel weight"?</STRONG></FONT></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><STRONG><FONT
size=3 face=Arial></FONT></STRONG></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><STRONG><FONT
size=3 face=Arial>Thanks for your insight into what goes into configuring a good
stove test.</FONT></STRONG></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><STRONG><FONT
size=3 face=Arial></FONT></STRONG></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><STRONG><FONT
size=3 face=Arial>Best wishes,</FONT></STRONG></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><STRONG><FONT
size=3 face=Arial></FONT></STRONG></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><STRONG><FONT
size=3 face=Arial>Kevin</FONT></STRONG></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"></SPAN> </P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"> </SPAN></P></DIV></FONT></o:p></SPAN>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><STRONG><o:p></o:p></STRONG></SPAN></FONT></FONT></SPAN></FONT>-----
Original Message ----- </P></DIV></DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=crispinpigott@gmail.com href="mailto:crispinpigott@gmail.com">Crispin
Pemberton-Pigott</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> Saturday, May 04, 2013 9:01
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Stoves] Stove Definition -
controllability</DIV>
<DIV><BR></DIV>
<DIV class=WordSection1>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt; mso-fareast-language: EN-US">Dear
Kevin<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt; mso-fareast-language: EN-US"><o:p> </o:p></SPAN></P>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt; mso-fareast-language: EN-US">></SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">The question of
"What is an acceptable Turn-Down Ratio?" (TDR) is not a simple
one.</SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d"><o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Actually,
the cooks make it quite simple. If they cannot turn it down far enough to stop
burning their food, they won’t use that stove for that purpose. Obviously the
food preparation methods vary widely around the world so there is no
‘standard’ TDR which will satisfy everyone. That is we I consider the local
comparative performance test the most relevant for any stove programme. That
said, it is worth discussing the idea of a <I>minimum</I> ratio for
performance reviews.<o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="COLOR: windowtext"> <o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">Fundamentally,
the Cook has to control the heat to the pot for two reasons:</SPAN><SPAN
style="COLOR: windowtext"><o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">1: To cook it
properly</SPAN><SPAN style="COLOR: windowtext"><o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">2: To cook it
efficiently</SPAN><SPAN style="COLOR: windowtext"><o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN style="COLOR: #1f497d"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">I
agree these are the considerations the cook applies.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">If the stove does
not have an adequately high TDR, the Cook may be able to compensate
by:</SPAN><SPAN style="COLOR: windowtext"><o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">1: Adding extra
water and allow it to boil off</SPAN><SPAN
style="COLOR: windowtext"><o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">2: Move the pot
to a cool part of the stove top.</SPAN><SPAN
style="COLOR: windowtext"><o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN style="COLOR: #1f497d"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">The
methods reported are:<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Taking
off the lid which reduces the effective heating power by creating a large
additional loss of heat from the whole pot.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Adding
cold water.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Moving
the pot away from the fire laterally.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Elevating
the pot/food above the fire (common with roasted meat in a standard
BBQ)<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Stopping
any fanning of the fire<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Removing
fuel (fuel metering)<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Closing
air vents (air metering)<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Splashing
water on the fire (also common with a BBQ)<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Adding
a wet piece of fuel<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Removing
a heat transfer increasing device like a pot skirt<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Moving
the pot to a second or third (etc) hole on the stove where the heat is less
intense (common in Indonesia)<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Venting
ambient air into the chimney to reduce the draft (arguably a form of air
metering – used by John Davies in his packed bed coal
gasifier)<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Inserting
a plate between the heat source and the cooking vessel<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Transferring
the pot or the contents of the pot to a retain heat
cooker.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">>…</SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">Thus, a TDR of
perhaps only 2 may suffice with a non-covered pot, while a TDR of 6 may be
required if the pot is covered. </SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d"><o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">While
I understand your point, the standardisation of a minimum requirement would
consider dominant cooking methods and allow the market to sort out the
different between, say, 4:1 and 6:1 products. <o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">The required TDR
will depend on whether the cooking pot is covered or not.</SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d"><o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">I
believe the cook will have a practical approach: if the food is going to cook
adequately (meaning not at a particularly high power which another stove may
have) there should be a minimum cooking power and a minimum turn down. I do
not like the idea that it has to be a particular number of Watts that the
stove has to yield or turn down to. The reason for this is there are a large
number of cooking appliances for a wide range of things and any stated limit
will immediately rule out stoves that are perfectly capable of delivering a
needed cooked product. In order to have a viable and broadly applied standard,
it will have to be relative to some stated ratios rather than ranges. It is
reasonable for a national standard for domestic stoves to have an upper power
limit on what is considered ‘domestic’.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">If
a pot lid is off by local convention, the net cooking power will necessarily
be reduced for any given firepower. I cannot state with certainty that it will
allow the proper cooking of all foods with a lower TDR. It might even have to
be higher. Remember that the only viable method of determining the TDR is to
test the amount of heat getting into the pot and even with the lid off, at low
temperatures that rate is pretty much the same as a pot with a lid on. In
other words the ΔT and the water evaporated are still going to give a
realistic value of heat gained, even if more of that heat is passed into the
air in the form of water vapour. I am not convinced the reduced cooking
efficiency (net heat in water) is lower or higher.<o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="COLOR: windowtext"> <o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">>…</SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">One notable
exception would be when the Cook purposely wants to boil away excess water, to
thicken the food.</SPAN><SPAN
style="COLOR: windowtext"><o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="COLOR: windowtext"> <o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">I
feel this does not impact the TDR.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">Also, the maximum
heat input rate to the pot, ie "pot power", will have an effect on
the required TDR. </SPAN><SPAN
style="COLOR: windowtext"><o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="COLOR: windowtext"> <o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Aha.
Well this is not the case. The definition of the turn down is not the
firepower, it is the heat gained by the pot. Interestingly, there are major
outcomes from this conceptual difference. The WBT’s classically observed the
fire but people do not cook with the heat of the fire, only the part which
gets to the pot. As you have observed, the heat transfer efficiency varies
with firepower and therefore stating a minimum TDR does not really say
anything about the firepower involved, only the cooking
power.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">In
summary:</SPAN><SPAN style="COLOR: windowtext"><o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">1: For most
efficient cooking, and to reflect most common cooking practises, the pot
should be covered.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">That
is not relevant to the TDR, though an important programmatic
consideration.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">2: Heating pots
with no cover will require more cooking fuel, but by addition of
water, burning or scorching of foods can be prevented, with a lower TDR.
This assumes that adding water during cooking is acceptable to the
Cook.</SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d"><o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">That
is a cooking technique, not a TDR.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">3: .A stove
heating a covered pot will require a larger TDR than a stove heating an open
top pot with no cover.</SPAN><SPAN
style="COLOR: windowtext"><o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">This
is debatable and so far I am not convinced.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">4: A stove with
"high pot power input" will require a larger TDR than a pot with a lower "pot
power input."</SPAN><SPAN
style="COLOR: windowtext"><o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN style="COLOR: #1f497d"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">This
is a no-no because to embed the concept into a Standard means interfering with
preferences of the manufacturer and customer. The deal is between the buyer
and the provider, not the regulator. The regulations are there to protect the
customer and to label a product as being able to perform certain things, such
as to deliver a locally acceptable water boiling rate in a pot with a diameter
of 150mm or 300mm (as per the label on the product). The customer knows full
well that a stove that cooks ‘well’ with a 250mm diameter pot will have
problems getting the same cooking experience out of a 400mm diameter pot. What
is not permissible is to have a manufacturer claim that the product ‘cooks
well’ with a 400 when a test of the heat transfer rate shows it will only do
so if the pot is about 250 in diameter.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">With
respect to controllability, a cooking stove needs some form of power
regulating in terms of the heat getting to the pot. How that is achieved is up
to the manufacturer. I have seen one stove that could turn down only about 10%
and the mechanism used was to stop producing so much CO2 and produced CO
instead. It worked…..!<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="COLOR: windowtext"> <o:p></o:p></SPAN></P></DIV>
<DIV>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">The actual TDR
required can be measured with present day instrumentation in common use. Once
the maximum "high pot power input" rate is measured, the fire can be turned
down, or allowed to die down slowly, and the point where water temperature
starts to fall can also be measured. </SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d"><o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Unfortunately
that turns out to be imprecise. It is best to determining the heat transfer
rate using cold pots of water, swapping them when the water reaches 65 to 70
deg C( before any evaporation takes place). It is quite easy to get a 2-3%
precision on the whole operation (depending on the fuel type and the care take
to measure it).<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d">></SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: windowtext">Knowing the rate
of fuel burning at that time enables calculation of the required TDR.
</SPAN><SPAN
style="FONT-FAMILY: 'Arial','sans-serif'; COLOR: #1f497d"><o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">The
rate of mass loss is one thing, what is burning is quite another. Frank and I
have been discussing how to refine that! It is not so simple with biomass, and
is much more difficult it there is a lot of char involved, but not
impossible.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Thanks
so much for your thoughtful inputs.<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Regards<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt">Crispin<o:p></o:p></SPAN></P>
<P class=MsoNormal><SPAN
style="FONT-FAMILY: 'Calibri','sans-serif'; COLOR: #1f497d; FONT-SIZE: 11pt"><o:p> </o:p></SPAN></P></DIV></DIV>
<P>
<HR>
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