<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body style="background-color: rgb(255, 255, 255); line-height: initial;">
<div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">
Dear Dean</div>
<div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">
<br>
</div>
<div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">
One answer to your question has been provided in the form of the Lion Stove with counter-flowing air: make the primary air feed from the back, not under the fuel, with the secondary air limited by a drop-down plate. I believe Xunda makes such a 'closer plate'
on one of their stoves. </div>
<div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">
<br>
</div>
<div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">
A grate can be used to hold up the char to burn it completely. The result (as demonstrated with perhaps 650 institutional Lion Stoves) is a flame in the centre, much better mixing, lower heat loss to the chamber walls, shorter flames, less char production saving
fuel, and lower excess air by a factor of about 6 to 8. </div>
<div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">
<br>
</div>
<div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">
The drawings and photos needed are in the Library in the stoves section at www.newdawnengineering.com. </div>
<div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">
<br>
</div>
<div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">
One of the stove list members built a 'lion cub' which is a domestic version. It was quite successful, he said. He reported it here. </div>
<div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">
<br>
</div>
<div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">
Regards </div>
<div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">
Crispin </div>
<br>
<div>
<div dir="ltr">Dear Kirk and All,
<div><br>
</div>
<div>Generally I think that the study of the TLUD has opened up new thinking about the Rocket. Super insulating the Rocket (and every other trick to improve time, temperature, turbulence) helps to keep only the tips of the sticks burning and to burn up quickly
the made charcoal so the air flow under the sticks is not blocked. If we think of the air flowing under the sticks as 'primary' air and the air flowing on top of the sticks as 'secondary' air the intention is the same as in the TLUD. The primary air controls
the rate of reaction (solid making gas) and the secondary air creates mixing. In the Rocket the flame naturally flows up the back wall and big open spaces occur near the front walls. Almost no mixing, unfortunately.</div>
<div><br>
</div>
<div>Using the primary air to slow the rate of wood gas production and forcing the secondary air to mix cleans up the Rocket as in the TLUD.</div>
<div><br>
</div>
<div>I'm hoping that Kirk and company will come to Stove Camp and figure out how to optimize natural draft mixing in the Rocket.</div>
<div><br>
</div>
<div>Best,</div>
<div><br>
</div>
<div>Dean</div>
<div><br>
<div class="x_gmail_extra"><br>
<div class="x_gmail_quote">On Sun, Apr 26, 2015 at 1:07 AM, kgharris <span dir="ltr">
<<a href="mailto:kgharris@sonic.net" target="_blank">kgharris@sonic.net</a>></span> wrote:<br>
<blockquote class="x_gmail_quote" style="margin:0 0 0 .8ex; border-left:1px #ccc solid; padding-left:1ex">
<u></u>
<div bgcolor="#ffffff">
<div>
<div><font size="2" face="Arial"></font></div>
<font size="2" face="Arial">
<p class="x_MsoNormal" style="line-height:normal; margin:0in 0in 0pt"><span style="font-family:'Arial','sans-serif'; font-size:14pt">Dean,</span><span style="font-family:'Times New Roman','serif'; font-size:14pt"><u></u><u></u><u></u></span></p>
<p class="x_MsoNormal" style="line-height:normal; margin:0in 0in 0pt"><span style="font-family:'Arial','sans-serif'; font-size:14pt"><u></u> <u></u></span></p>
<p class="x_MsoNormal" style="line-height:normal; margin:0in 0in 0pt"><span style="font-family:'Arial','sans-serif'; font-size:14pt">This is a clever idea.<span>
</span>The inner dark radiating surface of the chamber liner would return heat to the flame while it's outer shiny surface, being a less efficient radiator of heat, would radiate less heat outward.<span>
</span>Below are some thoughts which I hope are not too far off base. <u></u><u></u></span></p>
<p class="x_MsoNormal" style="line-height:normal; margin:0in 0in 0pt"><span style="font-family:'Arial','sans-serif'; font-size:14pt"><u></u> <u></u></span></p>
<p class="x_MsoNormal" style="line-height:normal; margin:0in 0in 0pt"><span style="font-family:'Arial','sans-serif'; font-size:14pt">My first inclination is that your rocket stoves are so well insulated that it would make very little difference since all that
heat is being retained anyway.<span> </span>A re-radiating surface would be little more effective than a reflective surface since they both do the same thing, return the heat to the flame. However, if a radiant surface could radiate fast enough to keep the
wall temperature lower than it would be otherwise (conservation of energy, if the surface is radiating heat then there is less heat in the surface so the temperature is lower), then the stove could be operated with cooler walls as well as a hotter flame. This
would be helpful by allowing less heat loss to the outside and by keeping the wall cooler for better lifespan.
<span> </span>A hotter flame would not be more efficient unless there is enough preheated air, mixing, and dwell time to take advantage of the extra heat.<span>
</span>Back to the basics required for a fire;</span><span style="font-family:'Arial','sans-serif'; font-size:14pt"> fuel, oxygen, and heat.<span>
</span>If there is not enough air then increasing the heat won’t help.</span><span style="font-family:'Times New Roman','serif'; font-size:14pt"><u></u><u></u></span></p>
<p class="x_MsoNormal" style="line-height:normal; margin:0in 0in 0pt"><span style="font-family:'Arial','sans-serif'; font-size:14pt"><u></u> <u></u></span></p>
<p class="x_MsoNormal" style="line-height:normal; margin:0in 0in 0pt"><span style="font-family:'Arial','sans-serif'; font-size:14pt">If I were working on improving the efficiency of the natural draft rocket stove, I would want to first design an experiment
that would tell me what the gas flow is inside the stove. Where is any excess air, flame and any unburned wood gas, how are they moving, and how much of each is present?
<span> I understand from Dr. Winiarski that the flow up through the chimney is not symetrical and contains excess unmixed air.
</span>A 3D computer model of flowing gasses through the stove could allow ideas to form for improved mixing of air with wood gas and flame. This could allow a secondary burn using the excess preheated air already in the stove, and perhaps some method of concentrating
the flame for increased dwell time. A clean burn is not necessarily hotter, but rather more complete. I agree with what you said in an earlier e-mail, that a clean low soot flame requires excess air to make sure all the fuel and soot is burned. The excess
air cannot be allowed to cool the flame, so using the excess preheated air that is already in the stove is the way to go.<span>
</span>With improved mixing and dwell time, increasing flame temperature by radiating heat from the wall could help.<u></u><u></u></span></p>
<p class="x_MsoNormal" style="line-height:normal; margin:0in 0in 0pt"><span style="font-family:'Arial','sans-serif'; font-size:14pt"><u></u> <u></u></span></p>
<p class="x_MsoNormal" style="line-height:normal; margin:0in 0in 0pt"><span style="font-family:'Arial','sans-serif'; font-size:14pt">Kirk</span><span style="font-family:'Times New Roman','serif'; font-size:14pt"><u></u><u></u></span></p>
<p class="x_MsoNormal" style="margin:0in 0in 10pt"><span style="line-height:115%; font-size:14pt"><u></u><font face="Calibri"> </font><u></u></span></p>
</font></div>
<div><font size="2" face="Arial"></font> </div>
<blockquote dir="ltr" style="border-left:#000000 2px solid; padding-left:5px; padding-right:0px; margin-left:5px; margin-right:0px">
<div style="font:10pt arial">----- Original Message ----- </div>
<div style="font:10pt arial; background:#e4e4e4"><b>From:</b> <a title="deankstill@gmail.com" href="mailto:deankstill@gmail.com" target="_blank">
Dean Still</a> </div>
<div style="font:10pt arial"><b>To:</b> <a title="stoves@lists.bioenergylists.org" href="mailto:stoves@lists.bioenergylists.org" target="_blank">
Discussion of biomass cooking stoves</a> </div>
<div style="font:10pt arial"><b>Sent:</b> Saturday, April 25, 2015 3:36 PM</div>
<div style="font:10pt arial"><b>Subject:</b> Re: [Stoves] Inner color of combustion chamber?</div>
<div><br>
</div>
<div dir="ltr">Hi All,
<div><br>
</div>
<div>We were wondering if an inner refractory metal black wall would absorb the IR (get very hot) and then emit back into</div>
<div>the fire. The outside of the metal wall would be shiny and then not emit very much into the stove body?</div>
<div><br>
</div>
<div>Best,</div>
<div><br>
</div>
<div>Dean</div>
</div>
<div class="x_gmail_extra"><br>
<div class="x_gmail_quote">On Fri, Apr 24, 2015 at 3:12 PM, Bamboo Science Group <span dir="ltr">
<<a href="mailto:greg@bamboosciencegroup.com" target="_blank">greg@bamboosciencegroup.com</a>></span> wrote:<br>
<blockquote class="x_gmail_quote" style="border-left:#ccc 1px solid; margin:0px 0px 0px 0.8ex; padding-left:1ex">
Dean<br>
Great topic<br>
When I was designing solar thermal panels for INCO in 1979, we used a coating (selective) process (chrome oxide spinel that had a alpha ( absorptivity) of 0.9 and and epsilon ( emissivity) of 0.04) on stainless steel that allowed it to perform at parity with
a black oxide on copper ( fin and tube). The parity was achieved despite the overwhelmingly superior conductance of copper versus s/s.<br>
The high alpha allows absorption of the short wave solar radiation and the low epsilon slows the longer wave radiation emission in this flat plate solar collector application. These "selective" surfaces have cavernous surface area structure, utilizing the peaks
and valleys of the coating to slow down the emissivity of the longer wave radiation.<br>
<br>
So you want an low emissivity coating for your refractory material to reduce ( inhibit) the black body radiation. SERI could certainly help out in this area as they are acquainted with high-temperature selective coatings for their work on concentrating collectors.<br>
<br>
Sent from my iPad<br>
<br>
> On Apr 24, 2015, at 5:07 PM, Dean Still <<a href="mailto:deankstill@gmail.com" target="_blank">deankstill@gmail.com</a>> wrote:<br>
><br>
> Hi All,<br>
><br>
> At the Aprovecho weekly meeting we were discussing how to improve performance in a Rocket stove. We were wondering about radiation.<br>
><br>
> Would temperatures rise if the inside of the refractory metal combustion chamber was black and the outside shiny?<br>
><br>
> Best,<br>
><br>
> Dean<br>
> _______________________________________________<br>
> Stoves mailing list<br>
><br>
> to Send a Message to the list, use the email address<br>
> <a href="mailto:stoves@lists.bioenergylists.org" target="_blank">stoves@lists.bioenergylists.org</a><br>
><br>
> to UNSUBSCRIBE or Change your List Settings use the web page<br>
> <a href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org" target="_blank">
http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</a><br>
><br>
> for more Biomass Cooking Stoves, News and Information see our web site:<br>
> <a href="http://stoves.bioenergylists.org/" target="_blank">http://stoves.bioenergylists.org/</a><br>
><br>
<br>
_______________________________________________<br>
Stoves mailing list<br>
<br>
to Send a Message to the list, use the email address<br>
<a href="mailto:stoves@lists.bioenergylists.org" target="_blank">stoves@lists.bioenergylists.org</a><br>
<br>
to UNSUBSCRIBE or Change your List Settings use the web page<br>
<a href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org" target="_blank">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</a><br>
<br>
for more Biomass Cooking Stoves, News and Information see our web site:<br>
<a href="http://stoves.bioenergylists.org/" target="_blank">http://stoves.bioenergylists.org/</a><br>
<br>
</blockquote>
</div>
<br>
</div>
<p></p>
<hr>
<p></p>
_______________________________________________<br>
Stoves mailing list<br>
<br>
to Send a Message to the list, use the email address<br>
<a href="mailto:stoves@lists.bioenergylists.org" target="_blank">stoves@lists.bioenergylists.org</a><br>
<br>
to UNSUBSCRIBE or Change your List Settings use the web page<br>
<a href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org" target="_blank">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</a><br>
<br>
for more Biomass Cooking Stoves, News and Information see our web site:<br>
<a href="http://stoves.bioenergylists.org/" target="_blank">http://stoves.bioenergylists.org/</a><br>
<br>
<p></p>
<hr>
<p></p>
<a></a>
<p align="left" color="#000000">No virus found in this message.<br>
Checked by AVG - <a href="http://www.avg.com" target="_blank">www.avg.com</a><br>
Version: 2015.0.5863 / Virus Database: 4334/9623 - Release Date: 04/25/15</p>
<p></p>
<p></p>
</blockquote>
</div>
<br>
_______________________________________________<br>
Stoves mailing list<br>
<br>
to Send a Message to the list, use the email address<br>
<a href="mailto:stoves@lists.bioenergylists.org">stoves@lists.bioenergylists.org</a><br>
<br>
to UNSUBSCRIBE or Change your List Settings use the web page<br>
<a href="http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org" target="_blank">http://lists.bioenergylists.org/mailman/listinfo/stoves_lists.bioenergylists.org</a><br>
<br>
for more Biomass Cooking Stoves, News and Information see our web site:<br>
<a href="http://stoves.bioenergylists.org/" target="_blank">http://stoves.bioenergylists.org/</a><br>
<br>
<br>
</blockquote>
</div>
<br>
</div>
</div>
</div>
</div>
</body>
</html>