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<div class="moz-cite-prefix">I have a different opinion about
chillers: A single central unit creates a single point of failure
for the entire facility, and maintenance requires everything to be
shut down at once. I would rather have the (several small)
chillers where I can see them, and I don't trust facilities people
to do the maintenance properly. Same advice for UPS. Out of sight,
out of mind. Also, if you have numerous chillers then you should
keep a spare handy, just as you would for vacuum pumps.<br>
<div class="moz-signature"> <br>
<font size="-2">--------------------------------<br>
Michael Rooks <br>
Yale Institute of Nanoscience and Quantum Engineering <br>
<a href="http://nano.yale.edu">nano.yale.edu</a>
</font>
<br>
<br>
<br>
<br>
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On 03/16/2015 12:26 PM, Michael Khbeis wrote:<br>
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<div>Loik </div>
<div><br>
</div>
<div>I think that having the electrical load converted to heat
load and having the diversity factor is sufficient. You can
subtract the heat load dissipated through chilled water but that
is presumably also being fed by your primary chiller. I would
err on the side of being conservative since cleanrooms always
end up being packed to a maximum density of equipment and people
during their lifespans - give yourself a 20% margin at the
least. I also would not discount the impact of the filter fan
unit heat dissipation. Since you are recycling most of the air
several times the joule heating from the FFUs will cause a
noticeable temperature rise. Given the class of your Cleanroom
the FFU density will not be as high but I would add them into
the load calc. </div>
<div><br>
</div>
<div>Finally, regarding central chiller vs multiple point of use
units - much easier to keep spare parts on hand and do PMs on a
central chiller unit as these are usually handled by the
building facilities folks. In my opinion, multiple point of use
chillers are a maintenance nightmare and you often end up buying
something quickly to replace or augment a failing unit. It is
nearly impossible to keep multiple point of use units running
consistently if you don't have dedicated maintenance staff. The
exception to this is if your tools all required different or
special temperatures and you end up needing multiple
water-to-water heat exchangers then point of use chillers may
make sense. </div>
<div><br>
</div>
<div>Best,<br>
<br>
<div><span style="background-color: rgba(255, 255, 255, 0);">Dr.
Michael Khbeis</span>
<div><span style="background-color: rgba(255, 255, 255, 0);">Washington
Nanofab Facility<br>
University of Washington<br>
Fluke Hall, Box 352143<br>
(O) <a moz-do-not-send="true" href="tel:206.543.5101"
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<div><br>
On Mar 16, 2015, at 7:36 AM, Loïk GENCE <<a
moz-do-not-send="true"
href="mailto:Loik.gence@cetuc.puc-rio.br">Loik.gence@cetuc.puc-rio.br</a>>
wrote:<br>
<br>
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Hi Everyone,<br>
<br>
I am working on the design of a small cleanroom facility
(70m2) ISO 5/6. Right now, I am dealing with the problem of
thermal load,<br>
Which is crucial here in Rio, where the average outside
temperature is of 30 deg C with a relative humidity of 75-80
%.<br>
<br>
I would like to have your help and/or comments on several
points:<br>
<br>
Most of the manufacturers do not provide a value for the
thermal load (why?). Assuming 2 or max 3 people working
simultaneously in the cleanrooms, and usual cleanroom value:
22 deg C - 55% humidity. The main issue is: how can I estimate
the cooling power required for the Air Conditioning System
(ACS)?<br>
<br>
I have the list of equipments we'll have and the corresponding
electrical power. I assumed the heat generated by 2 users and
added the total electrical power dissipated as heat inside of
the cleanroom, using a simultaneity factor of 0.75 (all
equipments won't be turned on at the same time) and neglected
the heat produced by the filter fan and lightning. <br>
<b> </b><b><br>
</b><b> - Is it reasonable for dimensioning the ACS
cooling power ? </b><br>
<br>
Also most of the equipments have a cooling water circuit. But
the cooling power needed is well described in the installation
manual provided with the equipments. <br>
<br>
<b> - Should I subtract from the </b><b>ACS cooling
power</b><b> value, </b><b> the cooling po</b><b>wer </b><b>from
the chillers?</b><br>
<br>
- <b>Do you think a central and unique chiller
(placed outside of the building) is preferred to several
smaller chillers placed closer to the equipment?</b><br>
<br>
<br>
I thank you very much for your kind help or comments.<br>
<br>
<br>
regards,<br>
<br>
Loïk.<br>
<br>
<pre class="moz-signature" cols="72">--
__________________________________________
Dr. Loïk Gence
PUC-RIO/CETUC-LABSEM
End Rua Marques de São Vicente, 225-Gavea
CEP:22451-900 Rio de Janeiro, RJ-Brasil
(Telefone) +55 (021) 3527-2193
(Mobile) +55 (021) 99156-5558
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="mailto:loik.gence@cetuc.puc-rio.br">loik.gence@cetuc.puc-rio.br</a>
__________________________________________</pre>
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