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<div class="moz-cite-prefix">Dear Michal, (and Stovers)<br>
<br>
I am sending this reply and your message (below) to the 500+
readers of the Stoves Listserv. Any replies from them need to be
sent to you also at Michal Usowicz
<a class="moz-txt-link-rfc2396E" href="mailto:usowicz@mail.usf.edu"><usowicz@mail.usf.edu></a> because you are not subscribed to
the Stoves Listserv.<br>
<br>
About chimneys, I am not qualified to respond. My only comment is
to question the size (and probable expense) of what you are
discussing. <br>
<br>
Dr TLUD<br>
<pre class="moz-signature" cols="72">Paul S. Anderson, PhD aka "Dr TLUD"
Email: <a class="moz-txt-link-abbreviated" href="mailto:psanders@ilstu.edu">psanders@ilstu.edu</a> Skype: paultlud Phone: +1-309-452-7072
Website: <a class="moz-txt-link-abbreviated" href="http://www.drtlud.com">www.drtlud.com</a></pre>
On 3/23/2013 7:23 AM, Michal Usowicz wrote:<br>
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cite="mid:CAHEP6_e8xDb54rsAsi6jq_nhBO+Leatr99Ns=9CKZq=ZvLUE3w@mail.gmail.com"
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<p class="MsoNormal" style="margin:0in 0in 0pt"><font size="3"><font
face="Calibri">Dr Anderson,</font></font></p>
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<p class="MsoNormal" style="margin:0in 0in 0pt"><font size="3"><font
face="Calibri">I hope that
everything is going wonderfully with you and that your TLUDs
are still
burning!<span style=""> </span>I recently got to
Madagascar
for Peace Corps service and things have been progressing
well.<span style=""> </span>My host family for pre-service
training here
cooks with wood inside but they are planning to build a
chimney and I would
like to help them construct a good one.<span style="">
</span>Large diameter (about 3-4 ft) brick chimneys similar
to what you may
expect to see in US homes are common in the community that
my host family is in
and I think a brick chimney will be the best solution to
ventilating the home
in this context.<span style=""> </span></font></font></p>
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<p class="MsoNormal" style="margin:0in 0in 0pt"><font size="3"><font
face="Calibri">A large
diameter, natural draft, brick chimney seems like a straight
forward problem
but I wanted to make sure that I was not making any
mistakes.<span style=""> </span>I thought you may be a
good person to ask
even though I know this isn’t your exact specialty.<span
style=""> </span>I expect the chimney will be about
15-20 ft
tall and at least the hearth will have a rectangular
cross-sectional area of
3.5x4 ft^2 since that it the current size of my host
mother’s fireplace
(although I am unsure if my host family will construct the
chimney with a
taper).<span style=""> </span>It will primarily be made
out of
clay bricks and mortar.<span style=""> </span>Could you
please give me some guidance on the following questions?</font></font></p>
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<p class="MsoListParagraphCxSpMiddle" style="margin:0in 0in 0pt
0.5in"><span style=""><span style=""><font size="3"
face="Calibri">1.</font><span style="font:7pt/normal
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Roman";font-size-adjust:none;font-stretch:normal">
</span></span></span><font size="3"><font face="Calibri"><span
style=""> </span><span style=""> </span>Is there a good
rule of thumb for the minimum
chimney height to have good draw from the hearth?<span
style=""> </span>The only way that I have to estimate
this is
using the chimney effect equation (ie flow is proportional
to Area, height^0.5)
and I found that for practical chimney heights for my
situation (ie 15-20 ft)
there was not a significant change in the flow rate of the
chimney.<span style=""> </span>However, for the equation
to apply the
chimney needs to be adiabatic, which I think is a bad
assumption in this
case.<span style=""> </span>Do you think 15 ft will be
tall
enough or does it need to be taller?</font></font></p>
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<p class="MsoListParagraphCxSpMiddle" style="margin:0in 0in 0pt
0.5in"><span style=""><span style=""><font size="3"
face="Calibri">2.</font><span style="font:7pt/normal
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Roman";font-size-adjust:none;font-stretch:normal">
</span></span></span><font size="3"><font face="Calibri">I
do not understand the effects of geometry on
chimney draw and was curious if there is a problem with
necking down the
chimney significantly after the hearth?<span style="">
</span>I suspect that my host family may copy the design of
a neighbor’s
chimney (since they are hiring the same mason to build
theirs) which tapers
down asymmetrically (ie the left wall is slanted and the
right is straight)
after the hearth from about 2x3.5 ft^2 at the base to
about 2x1 ft^2 over
about 6 ft.<span style=""> </span><span style=""> </span></font></font></p>
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<p class="MsoListParagraphCxSpMiddle" style="margin:0in 0in 0pt
0.5in"><span style=""><span style=""><font size="3"
face="Calibri">3.</font><span style="font:7pt/normal
"Times New
Roman";font-size-adjust:none;font-stretch:normal">
</span></span></span><font size="3"><font face="Calibri">Along
the lines of the previous question, I am
concerned that the rain cap for the chimneys may choke the
flow.<span style=""> </span>The rain caps of the chimneys
here is a thin
slab of concrete set at the top of the chimney with 1-3
bricks at each
corner.<span style=""> </span>Do I need to pay attention
to
the size of the gaps under the rain cap?</font></font></p>
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<p class="MsoListParagraphCxSpMiddle" style="margin:0in 0in 0pt
0.5in"><span style=""><span style=""><font size="3"
face="Calibri">4.</font><span style="font:7pt/normal
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Roman";font-size-adjust:none;font-stretch:normal">
</span></span></span><font size="3"><font face="Calibri">I
know if you build the chimney shorter than the
apex of the house the chimney effect of the house may
overwhelm the effect of
the chimney.<span style=""> </span>Do you have any
intuition
or advice about the height difference between the chimney
and the roof apex
that is needed to avoid this?<span style=""> </span></font></font></p>
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<p class="MsoListParagraphCxSpMiddle" style="margin:0in 0in 0pt
0.5in"><span style=""><span style=""><font size="3"
face="Calibri">5.</font><span style="font:7pt/normal
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</span></span></span><font size="3"><font face="Calibri">I
feel intuitively that it would be a good idea
to minimize the height of the hearth entrance to capture the
smoke plume before
it spreads but I am not sure if this matters if there is
good draw in the
chimney.<span style=""> </span>Do you have an opinion on
this?</font></font></p>
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<p class="MsoListParagraphCxSpLast" style="margin:0in 0in 0pt
0.5in"><span style=""><span style=""><font size="3"
face="Calibri">6.</font><span style="font:7pt/normal
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</span></span></span><font size="3"><font face="Calibri">Have
you ever heard of Rumsford chimneys?<span style=""> </span>I
had a construction engineer friend of mine
build one in his house and he said that the draw from the
chimney was
excellent.<span style=""> </span>I was just curious if you
had
heard of it and if you had an opinion of it.<span style="">
</span></font></font></p>
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<p class="MsoNormal" style="margin:0in 0in 0pt 0.25in"><font
size="3"><font face="Calibri">Again I hope that everything is
going
well with you.<span style=""> </span>I would really
appreciate
any advice you may be able to give.</font></font></p>
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<p class="MsoNormal" style="margin:0in 0in 0pt"><font size="3"><font
face="Calibri">Sincerely,</font></font></p>
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<p class="MsoNormal" style="margin:0in 0in 0pt"><font size="3"><font
face="Calibri">Michal
Usowicz</font></font></p>
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