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Dear Curtis, Gaurav and Cheney<br>
<br>
I cannot profess to understand radiation exchange in the depth I
really should. I do however have some experience of energyplus and
one thing I wouldn't want to attempt in it is Virtual partitions.
Under most circumstances its gradient based or node based
displacement vent models are probably superior to the "stacked"
volumes approach.<br>
<br>
I'm still unconvinced regarding the need for virtual partitions to
denote perimeter zones for the following reasons:<br>
<ul>
<li>The 15ft perimeter in LEED appears to be relating to
speculative office space that could be subject to fit-out. A
fit-out would be undertaken with solid partitions. Therefore,
why not model with solid partitions?<br>
</li>
<li>If, on the other hand, the perimeter zone requirement relates
to varying access to daylight, modelling of daylight sensors may
better serve this purpose.</li>
<li>The virtual partition seems to be a rather artificial boundary
possibly subject to an expensive computational overhead and
convergence issues.</li>
</ul>
Finally, I feel these points must also be weighed against the
designers judgement as to whether Air temperature (or Space
conditioning based on Air temperature) will vary significantly
across the floor plate.<br>
<br>
Best regards<br>
<br>
Chris<br>
<br>
On 26/01/2011 17:26, Curtis Pedersen wrote:
<blockquote
cite="mid:58B8D82D-154D-4772-9632-FCBB8509F6E3@illinois.edu"
type="cite">Chris and other responders:
<div><br>
</div>
<div>Depending on what heat transfer modes your simulation
includes, results from a "virtual partition" can be incorrect.
If you have intersurface long wave radiation exchange, a black
partition will cut the radiation exchange in half (check it out
in a good heat transfer text). EnergyPlus, which does radiant
exchange, has a feature called "infrared transparent surfaces",
which are black, massless, low thermal resistance surfaces that
compensate for the reduction in radiation exchange. </div>
<div><br>
</div>
<div>Curtis Pedersen</div>
<div>Professor Emeritus, University of Illinois</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div> <br>
<div>
<div>On Jan 26, 2011, at 10:28 AM, Chris Yates wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">
<div bgcolor="#ffffff" text="#000000"> Hello,<br>
<br>
<i>Virtual partition: a transparent partition with no mass
and no thermal resistance. If the simulation employs an
air flow network it may also be considered as a hole
allowing air to pass through the partition. Usually used
to define a perimeter zone. (BTW this isn't quoting any
source, just what I understand!)</i><br>
<br>
I feel I may be describing a cultural nuance of energy
modelling in the UK. So I'd like to ask the following:<br>
<ul>
<li>Do engineers in countries apart from the UK use
"virtual partitions"?</li>
<li>What benefits do virtual partitions have over
physical partitions?</li>
</ul>
Any other comments will be gratefully received.<br>
<br>
Many thanks<br>
<div class="moz-signature">-- <br>
<div>
<p>Chris Yates <span style="color: rgb(79, 98, 40);">C
Eng MCIBSE</span></p>
<p><i style="">Building Physics Consultant<o:p></o:p></i></p>
<p>Tel:<span style=""> </span>+447960731576</p>
<p>Email: <a moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:chris.malcolm.yates@gmail.com">chris.malcolm.yates@gmail.com</a></p>
<p>Skype: <span class="SpellE">christopher.m.yates</span></p>
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</blockquote>
<br>
<div class="moz-signature">-- <br>
<div>
<p>Chris Yates <span style="color: rgb(79, 98, 40);">C Eng
MCIBSE</span></p>
<p><i style="">Building Physics Consultant<o:p></o:p></i></p>
<p>Tel:<span style=""> </span>+447960731576</p>
<p>Email: <a class="moz-txt-link-abbreviated" href="mailto:chris.malcolm.yates@gmail.com">chris.malcolm.yates@gmail.com</a></p>
<p>Skype: <span class="SpellE">christopher.m.yates</span></p>
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