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Billy,<br>
I typically put a buffer storage tank in those loops instead of a
pipe. The idea is the same. The volume of the tank (or pipe) should
be a little more than the volume of fluid that the pump in the loop
can transfer in one timestep.<br>
Best,<br>
David<br>
<br>
<br>
On 2/20/2012 22:16, <a class="moz-txt-link-abbreviated" href="mailto:coolbilly1999@gmail.com">coolbilly1999@gmail.com</a> wrote:
<blockquote cite="mid:88A1DA4407C24A75AC15B08938D5E985@BillyPC"
type="cite">
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<div style="FONT-FAMILY: 'Calibri'; COLOR: #000000; FONT-SIZE:
12pt">
<div>Hi Matt,</div>
<div> </div>
<div>Thanks for the detailed explanation. I will try to
shorten the timestep. Actually, I also tried adding a pipe
between the cooling coil and chiller to store adequate flow
as mentioned in the documentation which I neglected before.
And it works pretty well and I will look into the other
warnings you mentioned. Thanks for your help again.</div>
<div> </div>
<div>Best regards,</div>
<div>Billy </div>
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'Calibri'; COLOR: #000000; FONT-SIZE: small; FONT-WEIGHT:
normal; TEXT-DECORATION: none">
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<div> </div>
<div style="BACKGROUND: #f5f5f5">
<div style="font-color: black"><b>From:</b> <a
moz-do-not-send="true" title="duffy@tess-inc.com"
href="mailto:duffy@tess-inc.com">Matt Duffy</a> </div>
<div><b>Sent:</b> Monday, February 20, 2012 8:53 AM</div>
<div><b>To:</b> <a moz-do-not-send="true"
title="coolbilly1999@gmail.com"
href="mailto:coolbilly1999@gmail.com">Billy Chen</a>
; <a moz-do-not-send="true"
title="trnsys-users@cae.wisc.edu"
href="mailto:trnsys-users@cae.wisc.edu">trnsys-users@cae.wisc.edu</a>
</div>
<div><b>Subject:</b> Re: [TRNSYS-users] Need helps to
solve the absorption chiller (Type677) issue</div>
</div>
</div>
<div> </div>
</div>
<div style="FONT-STYLE: normal; DISPLAY: inline; FONT-FAMILY:
'Calibri'; COLOR: #000000; FONT-SIZE: small; FONT-WEIGHT:
normal; TEXT-DECORATION: none">Billy,<br>
<br>
I looked at your listing file, and I noticed other important
things about your simulation. First of all, the timestep you
are using is much too large. You will notice in the TESS
HVAC Solar Absorption example, the timestep is 5 minutes
(note the equation in the control cards to implement this)
in order to consider the control decisions and flow rates
during that timestep. When using a large timestep, an
extraordinary amount of fluid is being sent through your
system, and if you are not simulating adequate capacitance
or storage in that loop, it will lead to components not
converging. Also, please note the other warnings at the end
of your listing file about the independent variables being
above or below the specified range in the performance data
files. The TRNSYS data interpolation routine does not
extrapolate, so if you send it an independent variable that
is not within the specified range, it will use the dependent
variable at that end(or beginning) of the range and not
extrapolate.<br>
<br>
Best regards,<br>
<br>
Matt Duffy<br>
<br>
<br>
<!--replyfwdwrap-->
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BACKGROUND-REPEAT: repeat-x; BACKGROUND-POSITION: 50% top"><strong>-----
Original Message -----</strong><br>
<strong>From:</strong> "Billy Chen"
<a class="moz-txt-link-rfc2396E" href="mailto:coolbilly1999@gmail.com"><coolbilly1999@gmail.com></a> <br>
<strong>Sent:</strong> Fri, February 17, 2012 17:22<br>
<strong>Subject:</strong> [TRNSYS-users] Need helps to
solve the absorption chiller (Type677) issue<br>
<br>
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<div>Hi TRNSYS users,</div>
<div> </div>
<div>I am building an absorption chiller model
for a medium office, and I used the similar
components from the TESS example (Restaurant
with absorption chiller). However, when I ran
the simulation, I got tons of warnings (from
SYS Message 441), and the simulation
terminated because it exceeded the limit of
warnings. The warning said as below:</div>
<div> </div>
<div>*** Warning at time :
3717.000000<br>
Generated by Unit : Not applicable or
not available<br>
Generated by Type : Not applicable or
not available<br>
TRNSYS Message 441 : The inputs to the
listed units have not converged at this
timestep. The values at the last iteration
will be used and the simulation will proceed.<br>
Reported information : UNITS: 12 13 18</div>
<div> </div>
<div>UNIT 12 is Type 677 double effect chiller</div>
<div>UNIT 13 is Type 144 pump</div>
<div>UNIT 18 is Type 697b cooling coil</div>
<div> </div>
<div>I checked the input units and I can't
figure out the problem. Could someone give me
some advice?</div>
<div> </div>
<div>And I also found out a problem when I ran
the TESS Restaurant example, the chilled water
outlet temperature is always going up over 100
degree C. But the temperature from the air
temperature from cooling coil looks
reasonable. It confuses me a lot. Does anyone
find this problem before and have any
suggestion on that?</div>
<div> </div>
<div>I attached the LST file and the plot for
the chiller water temp. I really appreciate
any help.</div>
<div> </div>
<div>Best regards,</div>
<div> </div>
<div>Billy</div>
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<pre class="moz-signature" cols="72">--
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI 53703 USA
P:+1.608.274.2577
F:+1.608.278.1475
<a class="moz-txt-link-abbreviated" href="mailto:d.bradley@tess-inc.com">d.bradley@tess-inc.com</a>
<a class="moz-txt-link-freetext" href="http://www.tess-inc.com">http://www.tess-inc.com</a>
<a class="moz-txt-link-freetext" href="http://www.trnsys.com">http://www.trnsys.com</a></pre>
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