Hi Ron,<div><br></div><div>I think that the newest testing data is still Jim Jetter's PowerPoint from the Lima PCIA conference. We are just starting to use the new metrics and have installed the pump and filter PM system next to the light scattering real time PM which is very cool! When you use a clean stove, like a tuned TLUD, the filter stays white after boiling and simmering the water. </div>
<div><br></div><div>Best,</div><div><br></div><div>Dean<br><br><div class="gmail_quote">On Fri, Jun 1, 2012 at 8:49 PM, Ron Larson <span dir="ltr"><<a href="mailto:rongretlarson@comcast.net" target="_blank">rongretlarson@comcast.net</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div bgcolor="#FFFFFF"><div>Dean and list:</div><div><br></div><div> Thanks for the news and your recommendations (below ).</div>
<div><br></div><div> Where can we get the most detail on the testing techniques and the results for different stove types?</div><div><br></div><div>Ron<br><br><br></div><div><br>On May 30, 2012, at 5:55 PM, Dean Still <<a href="mailto:deankstill@gmail.com" target="_blank">deankstill@gmail.com</a>> wrote:<br>
<br></div><div></div><blockquote type="cite"><div><p class="MsoNormal"> Hi All:</p><p class="MsoNormal"><br></p>
<p class="MsoNormal">This winter the new International Working
Agreement (IWA) was ratified in The Hague.
Four health based tiers divide stove performance. A top rated Tier 4 stove (PM and CO) without
a chimney is estimated to protect human health in a small kitchen with 15 air
exchanges per hour. Carbon Monoxide isn’t as bad as Particulate matter when
inhaled so it’s a lot easier to get a 4 (an “A”) for CO but only super clean stoves can make Tier 4 for high power PM. (Low power PM is easier.)</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">Most improved stoves that we have tested recently get 2’s
and 3’s for PM (a little bit of PM causes serious respiratory problems) but
even relatively ‘normal improved' stoves can get into the 4 category for CO. It’s
also possible for stoves to get a “4” for thermal efficiency. The stove has to
score above 45%. We used to think that this kind of score was almost impossible
to achieve. But now the understanding of heat transfer efficiency has been
ratcheted up a notch.</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"> Here’s how we try get a “4” on the IWA report card for thermal efficiency:</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal">We use an acronym (TARP-VE) to remind us of the most
important variables when designing a stove that uses the least fuel to boil and simmer water. </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal" style="margin-left:.5in">1.)<span style="font-family:'Times New Roman';font-size:7pt"> </span><b>Temperature</b>: increase as much as
possible the temperature of the gases/flames touching the pot. </p>
<p class="MsoNormal" style="margin-left:.5in">2.)<span style="font-family:'Times New Roman';font-size:7pt"> </span><b>Area</b>: increase as much as possible the
area of the pot touched by the gases/flames.</p>
<p class="MsoNormal" style="margin-left:.5in">3.)<span style="font-family:'Times New Roman';font-size:7pt"> </span><b>Radiation</b>: Don’t forget how powerful
radiation is! While Rocket type stoves depend on optimizing convection, if the
pot can be exposed to a hot radiating surface, water will boil a lot faster.</p>
<p class="MsoNormal" style="margin-left:.5in">4.)<span style="font-family:'Times New Roman';font-size:7pt"> </span><b>Proximity</b>: Force the hot gases into
narrow channels as close to the pot or griddle without decreasing the velocity
of the flow.</p>
<p class="MsoNormal"> 5.) <b>Velocity</b>:
Slowing the hot gases decreases the heat transfer efficiency. Keep the hot gases flowing as fast as possible without
decreasing the temperature of the gases. Insulate the heat flow path.</p>
<p class="MsoNormal"> 6.) <b>Evaporation</b>: We add this reminder that,
while a very large pot has the advantage that more of the pot is exposed to the heat,
a larger surface of water is evaporating which can make it difficult
to achieve full boil. That’s the reason that traditional pots have large
bottoms and smaller tops. </p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"> OK, dear friends, that’s our newest check list for making stoves more thermally efficient. </p><p class="MsoNormal"><br></p><p class="MsoNormal">Best,</p><p class="MsoNormal"><br></p><p class="MsoNormal">
Dean</p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"> </p>
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