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Mohamed,<br>
Chun Kwon is correct in his comments. I thought I would just add
some other things that I noticed. <br>
<br>
1. As Chun Kwon mentioned, you need to add some thermal capacitance
(probably in the form of a tank) in the cooling water loop. You also
need to reduce your timestep to something on the order of 5 minutes.
Make sure that all of the storage tanks in the simulation can hold
at least 1 timestep of fluid in them. The two tanks in your
simulation are rather small (1m3 and 0.3m3) given the flow rates on
your chiller. <br>
2. You have used the same flow rate equation to set all three flow
rates on the absorption chiller (hot water, cooling water, and
chilled water). All of the machines that I have seen have a certain
ratio of these flow rates. I have never seen a machine where all
three rated flow rates were the same. This might be skewing the
performance of the chiller.<br>
3. The thermal capacitance of your building zones is left at the
default value of 1.2*ZoneVolume, which accounts only for the thermal
capacitance of the air in the zone, not for any of the furnishings.
A better value would be approximately 1.2*5*ZoneVolume<br>
4. The chiller's capacity is left at its default value of 1500kW
which seems rather high, especially given the size of the cooling
coil.<br>
5. You correctly caught that you have to set the number of Type4
tank nodes on both the parameters and the outputs tab of the Type4
proforma. However, be careful, the question that you have to answer
is slightly different. In one case it asks how many nodes there are
and in the other case it asks how many nodes there are in addition
to the top and bottom nodes.<br>
<br>
What is specifically going on in your simulation is that the long
time step, the lack of capacitance in the cooling loop, and the very
large chiller capacity are causing one of the flow streams to not
only freeze but to drop well below -273C at which point the
psychrometrics routine generates an error.<br>
Kind regards,<br>
David<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 9/10/2013 07:38, Mohamed Adel wrote:<br>
</div>
<blockquote
cite="mid:179041044.17929.1378816714156.JavaMail.open-xchange@mail.sl-rasch.de"
type="cite">
<meta content="text/html; charset=ISO-8859-1"
http-equiv="Content-Type">
<div style="position: relative;">
<div> Dear All, </div>
<div> </div>
<div> While modeling a wet cooling tower in a simulation i
always receive an error from the utility routine
psycho-metrics. Please advise how to fix this error. </div>
<div> Kindly find attached the needed data. </div>
<div> </div>
<div> Best Regards <br>
<br>
Mohamed Adel <br>
M.Sc. Ing. <br>
<br>
SL-Rasch GmbH <br>
Special & Lightweight Structures <br>
Kesslerweg 22 <br>
D-70771 Leinfelden-Oberaichen <br>
t: 0049 176-32315274 <br>
<a class="moz-txt-link-abbreviated" href="mailto:mail:mohamed.adel@Sl-rasch.de">mail:mohamed.adel@Sl-rasch.de</a> </div>
</div>
<div id="ox-signature"> Best Regards <br>
<br>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
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<pre class="moz-signature" cols="72">--
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David BRADLEY
Principal
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