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Jeremiah,<br>
<br>
Your question is not quite on the mark because what I've described
is downstream from the calculation of room loads where techniques
such as the Weighting Factor or the Heat Balance methods come into
play. Before I get to that issue, though, I want to point out that
the "Adjust Loads" procedure I described is done automatically by
DOE-2 and totally invisible to the User; I did so only to explain
why<span> Bhartendu</span> (the original poster) was not seeing any
conduction loads through the ceiling. <br>
<br>
Now, back to this "Adjust Loads" procedure, there is no simulation
program I know of that solves simultaneously for the heat flows and
the zone temperature. DOE-2 does it in the two-step way that others
and I have just described. When you said "compared to the Heat
Balance Method", I assume you're thinking of EnergyPlus. So, how
does EnergyPlus meet this problem? Whereas DOE-2 does one year of
LOADS and then one year of SYSTEMS, EnergyPlus does them in the same
time step, but also sequentially. Therefore, EnergyPlus calculates
the heat flows using the zone temperature from the previous time
step which are then used in its HVAC simulation without adjustment.
This should be okay when zone temperatures don't change, but what
about at morning start-up when temperatures could change by 5-10 F
within one hour? I've always wondered whether that's why EnergyPlus
gives much lower heating loads in mild California climates than does
DOE-2? As far as which procedure is "more realistic", I can't say.<br>
<br>
Joe<br>
<pre class="moz-signature" cols="90">Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
<a class="moz-txt-link-abbreviated" href="mailto:yjhuang@whiteboxtechnologies.com">yjhuang@whiteboxtechnologies.com</a>
<a class="moz-txt-link-freetext" href="http://weather.whiteboxtechnologies.com">http://weather.whiteboxtechnologies.com</a> for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"
</pre>
<br>
On 8/19/2013 9:57 PM, Jeremiah Crossett wrote:
<blockquote
cite="mid:CAPsP_xTjc9wbNCwBn7ZA_9o=TE5KMfg0Sm5QGGvc7n3xVFqugA@mail.gmail.com"
type="cite">
<div dir="ltr">
<div class="gmail_default" style="font-family:
tahoma,sans-serif; font-size: small; color: rgb(51, 51, 51);">Joe, Just
wondering, given your expertise how would you compare this to
the heat balance method.., and what do you think is more
realistic? </div>
<div class="gmail_extra"><br clear="all">
<div>
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style="font-family: Verdana,sans-serif;"><br>
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<div>
<div style="text-align: center;"><b><span style=""><font
color="#000099" size="1"><b style="font-family:
Verdana,sans-serif;">Jeremiah D. Crossett</b><span
style="font-family: Verdana,sans-serif;"> </span><font
face="Verdana, sans-serif">| Senior </font><font
face="Verdana, sans-serif">Analyst</font><font
face="Verdana, sans-serif"> | Phase Change
Energy Solutions</font></font></span></b></div>
<b>
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size="1"><font color="#000099" face="Verdana,
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NC 27203 | Mobile <a moz-do-not-send="true"
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style="background-color: transparent;"><b
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href="http://www.phasechange.com"
target="_blank">www.phasechange.com</a> </b></b></div>
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src="http://i.imgur.com/Sldxf.jpg"></div>
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color="#0000fe"><br>
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<br>
<br>
<div class="gmail_quote">On Mon, Aug 19, 2013 at 6:14 PM, Joe
Huang <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:yjhuang@whiteboxtechnologies.com"
target="_blank">yjhuang@whiteboxtechnologies.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
0.8ex; border-left: 1px solid rgb(204, 204, 204);
padding-left: 1ex;">
<div text="#000000" bgcolor="#ffffff"> Just to repeat what
David and Rodrigo have already sad, DOE-2 calculates
conduction loads in a two step process. In LOADS, a
constant reference temperature is specified, which DOE-2
uses to calculate the amount of heat flow through the
surfaces. This is the LOADS loads summarized in the LS-E
and LS-F reports. In SYSTEMS, DOE-2 calculates the true
temperature of the zone based on the loads passed from
LOADS, as well as the actions of the HVAC system. In
the course of this calculation, the heat flows ("loads")
from LOADS are adjusted, but this is not done surface by
surface, but in total using the so-called "Zone
Conductance" times the difference between the actual
zone temperature and the reference temperature used in
LOADS. At this point, heat flows through internal walls
are also considered, using the difference between this
hour's zone temperature and the previous hour's zone
temperature of the adjacent space, e.g., the Attic or
Plenum. If you are interested in this number, I believe
it can be extracted in an hourly report. <br>
<br>
In reference to Rodrigo's question, I don't see any
benefit in forcing a heat flow between the room and the
attic by using different reference temperatures. You
will simply get a constant heat flow at that temperature
difference throughout the simulation. In reality, attics
are generally colder than the room in the winter and
warmer than the room in the summer, so the derived heat
flow with this temperature difference doesn't get you
any closer to reality, in my opinion.<br>
<br>
Joe<br>
<pre cols="90">Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
<a moz-do-not-send="true" href="mailto:yjhuang@whiteboxtechnologies.com" target="_blank">yjhuang@whiteboxtechnologies.com</a>
<a moz-do-not-send="true" href="http://weather.whiteboxtechnologies.com" target="_blank">http://weather.whiteboxtechnologies.com</a> for simulation-ready weather data
(o) <a moz-do-not-send="true" href="tel:%28925%29388-0265" value="+19253880265" target="_blank">(925)388-0265</a>
(c) <a moz-do-not-send="true" href="tel:%28510%29928-2683" value="+15109282683" target="_blank">(510)928-2683</a>
"building energy simulations at your fingertips"
</pre>
<div>
<div> <br>
On 8/19/2013 12:05 PM, David Wood wrote:
<blockquote type="cite">
<div>
<div>
<div>Hi All,<br>
<br>
</div>
The LS-C report comes from the LOADS
simulation portion of DOE 2.2. The plenum
reference temperature used in LOADS is
adjusted in the SYSTEMS portion of the program
and the loads in the spaces adjacent to the
plenum are corrected <br>
correspondingly.<br>
<br>
</div>
Dave Wood<br>
</div>
<div><br>
<br>
<div>On Thu, Aug 8, 2013 at 8:58 AM, Rodrigo
Cerqueira <span><<a moz-do-not-send="true"
href="mailto:rodrigo.cerqueira@mra.qc.ca"
target="_blank">rodrigo.cerqueira@mra.qc.ca</a>></span>
wrote:<br>
<blockquote>
<div lang="FR-CA">
<div>
<p><span lang="EN-US">Hi, </span></p>
<p> <span lang="EN-US">This happens
because the load calculation is made
with a fixed temperature (see
picture). All the spaces, include
plenum zones, have the same
temperature by default (70°F). So,
all roof load appears in the plenum
spaces. To considerate the roof
load, you have to change this
temperature in plenum spaces and a
part of roof load will appear like
"internal surface conduction". But
I'm not sure if this is a good
practice. </span><span>Maybe
someone else has an opinion about
that. </span></p>
<p><span> </span></p>
<p><span><img moz-do-not-send="true"></span><span>
</span></p>
<p><span> </span></p>
<p><b><span>Rodrigo Cerqueira, </span></b><span>ing.
jr, M.Ing.<b> </b></span></p>
<p><b><span>Simulation énergétique </span></b></p>
<p><span> </span></p>
<p><span><img moz-do-not-send="true"
alt="signatureCouriel"> </span></p>
<p><span> </span></p>
<p><span> </span></p>
<p><span> </span></p>
<div>
<p><b><span lang="FR">De :</span></b><span
lang="FR"> <a
moz-do-not-send="true"
href="mailto:equest-users-bounces@lists.onebuilding.org"
target="_blank">equest-users-bounces@lists.onebuilding.org</a>
[mailto:<a moz-do-not-send="true"
href="mailto:equest-users-bounces@lists.onebuilding.org" target="_blank">equest-users-bounces@lists.onebuilding.org</a>]
<b>De la part de</b> Bhartendu
Awasthi<br>
<b>Envoyé :</b> 8 août 2013 06:35<br>
<b>À :</b> <a
moz-do-not-send="true"
href="mailto:equest-users@lists.onebuilding.org"
target="_blank">equest-users@lists.onebuilding.org</a>;
<a moz-do-not-send="true"
href="mailto:bldg-sim@lists.onebuilding.org"
target="_blank">bldg-sim@lists.onebuilding.org</a><br>
<b>Objet :</b> [Equest-users] Roof
Conduction Load </span></p>
</div>
<p> </p>
<div>
<p>Hi All, </p>
<div>
<p> </p>
</div>
<div>
<pre><span>I am doing an energy simulation model in eQuest. I noticed that the load through roof conduction in LS-C is zero where as in LS-B (for plenum space) it is showing some load.</span><span> </span></pre>
<pre><span> </span></pre>
<pre><span>As per my understanding this load should appear in LS-C also.</span><span> </span></pre>
<pre><span>Also, if I reduce the U value of the roof, the load through roof reduces and can be accounted in LS-B only (plenum space).</span><span> </span></pre>
<pre><span> </span></pre>
<pre><span>Refer attached LS-C and LS-B reports.</span><span> </span></pre>
<pre><span>Any help will be appreciated.</span><span> </span></pre>
<pre><span> </span></pre>
<pre><span> </span></pre>
<pre><span>Thanks & Regards</span><span> </span></pre>
<pre><span> </span></pre>
<pre><span>Bhartendu Awasthi</span><span> </span></pre>
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<br>
-- <br>
<div>
<div><span><span><span></span></span><span><span></span></span><span><span>Regards,<br>
</span></span></span></div>
<div><span><span><span></span><br>
David S. Wood<br>
Principal<br>
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