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Francisco,<br>
I believe that TRNFlow's "horizontal opening" models allow flow only
in one direction at a given time step. I would guess that what happens
in your simulation is that when the zone is hotter than ambient, the
building wants to exhaust air and that when the building is colder than
ambient it doesn't (maybe it even backflows). Since air and go only one
direction at a timestep, the model tries to exhaust air but enough goes
out during a timestep that the building decides that no, it should
intake air and tries that. But it intakes enough air that the building
controls decide no, it should exhaust...and round and round, never
converging. <br>
<br>
I believe that TRNFlow has something called a "relaxation solver"
built in (controlled from the TRNSYS control cards) that tries to cope
with this problem by first relaxing, then tightening the solution
tolerances to come up with a stable solution. A trick that is possible
when using CONTAM (type97) is to use a short timestep (1 minute max)
and delay the zone temperatures that are being passed to the airflow
model but I don't think that's possible with TRNFlow. There is some
research being done on how best to provide a path up and a path down
for airflow in a bulk airflow model such as CONTAM or TRNFlow (COMIS)
but as it is a cooperative agreement and not funded, there isn't a
timeline on it.<br>
Regards,<br>
David<br>
<br>
<br>
On 9/27/2010 02:59, Mariëlle Nuchelmans wrote:
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<p class="MsoNormal"><font color="navy" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: navy;" lang="EN-GB">Are
you using a thermostate
or an equation to control the cooling? You should use an thermostate.
An
equation gives a zero or an one, so it can go off/on/off/on and your
program crashes
(on because it reaches setpoint and then off because wanted temperature
is
reached) A thermostate has a dead band and it chooses on/off after 5
iterations. It is less accurate but your program runs.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: navy;" lang="EN-GB"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: navy;">Good luck <o:p></o:p></span></font></p>
<p class="MsoNormal"><font color="navy" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: navy;"><o:p> </o:p></span></font></p>
<div>
<p class="MsoNormal"><font color="navy" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: navy;">Mariëlle <o:p></o:p></span></font></p>
<p class="MsoNormal"><font face="Times New Roman" size="3"><span
style="font-size: 12pt;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><b><font face="Tahoma" size="2"><span
style="font-size: 10pt; font-family: Tahoma; font-weight: bold;">Van:</span></font></b><font
face="Tahoma" size="2"><span
style="font-size: 10pt; font-family: Tahoma;">
<a class="moz-txt-link-abbreviated" href="mailto:frodriguezpc@labein.es">frodriguezpc@labein.es</a> [<a class="moz-txt-link-freetext" href="mailto:frodriguezpc@labein.es">mailto:frodriguezpc@labein.es</a>] <br>
<b><span style="font-weight: bold;">Verzonden:</span></b> maandag 27
september
2010 9:42<br>
<b><span style="font-weight: bold;">Aan:</span></b> Mariëlle
Nuchelmans<br>
<b><span style="font-weight: bold;">CC:</span></b> <st1:personname
w:st="on"><a class="moz-txt-link-abbreviated" href="mailto:trnsys-users@cae.wisc.edu">trnsys-users@cae.wisc.edu</a></st1:personname><br>
<b><span style="font-weight: bold;">Onderwerp:</span></b> RE:
[TRNSYS-users]
digging into trnflow convergence problems</span></font><o:p></o:p></p>
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<p class="MsoNormal"><font face="Times New Roman" size="3"><span
style="font-size: 12pt;"><o:p> </o:p></span></font></p>
<p class="MsoNormal" style="margin-bottom: 12pt;"><font
face="Times New Roman" size="3"><span style="font-size: 12pt;"><br>
</span></font><font face="sans-serif" size="2"><span
style="font-size: 10pt; font-family: sans-serif;">It crashes even at
n=7 timestep... I am pretty sure it
has to do with this temparature thing. A check to my lst file shows
this clear
pattern with lack of convergence in al the external temperature peaks,
so I
turned off cooling and the result is I get convergence thanks to
interior
temperatures going above exterior at most of the previous conflict
timesteps...
still there are a couple times of year where I still get higher ext.
temps, and
convergence problems show</span></font> <br>
<br>
<font face="sans-serif" size="2"><span
style="font-size: 10pt; font-family: sans-serif;">Francisco
Rodríguez Pérez-Curiel<br>
<br>
TECNALIA-Construcción<br>
Parque Tecnológico, Edificio 700. E-48160 Derio (Bizkaia) (SPAIN)<br>
Tel. +34 94 607 33 00, Fax. +34 94 607 33 49<br>
<a class="moz-txt-link-abbreviated" href="mailto:francisco.rodriguez@tecnalia.com">francisco.rodriguez@tecnalia.com</a>,<br>
<a class="moz-txt-link-abbreviated" href="http://www.tecnalia.com">www.tecnalia.com</a><br>
<br>
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<o:p></o:p></p>
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<p class="MsoNormal"><b><font face="sans-serif" size="1"><span
style="font-size: 7.5pt; font-family: sans-serif; font-weight: bold;">Mariëlle
Nuchelmans <a class="moz-txt-link-rfc2396E" href="mailto:M.Nuchelmans@chri.nl"><M.Nuchelmans@chri.nl></a></span></font></b><font
face="sans-serif" size="1"><span
style="font-size: 7.5pt; font-family: sans-serif;"> </span></font><o:p></o:p></p>
<p><font face="sans-serif" size="1"><span
style="font-size: 7.5pt; font-family: sans-serif;">27/09/2010 09:18</span></font>
<o:p></o:p></p>
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<td style="padding: 0.75pt; width: 59%;" valign="top"
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<p class="MsoNormal" style="text-align: right;"
align="right"><font face="sans-serif" size="1"><span
style="font-size: 7.5pt; font-family: sans-serif;">Para</span></font><o:p></o:p></p>
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<td style="padding: 0.75pt;" valign="top">
<p class="MsoNormal"><font face="sans-serif" size="1"><span
style="font-size: 7.5pt; font-family: sans-serif;"><a class="moz-txt-link-rfc2396E" href="mailto:frodriguezpc@labein.es">"frodriguezpc@labein.es"</a>
<a class="moz-txt-link-rfc2396E" href="mailto:frodriguezpc@labein.es"><frodriguezpc@labein.es></a></span></font> <o:p></o:p></p>
</td>
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<p class="MsoNormal" style="text-align: right;"
align="right"><font face="sans-serif" size="1"><span
style="font-size: 7.5pt; font-family: sans-serif;">cc</span></font><o:p></o:p></p>
</td>
<td style="padding: 0.75pt;" valign="top">
<p class="MsoNormal"><font face="sans-serif" size="1"><span
style="font-size: 7.5pt; font-family: sans-serif;">"<st1:personname
w:st="on"><a class="moz-txt-link-abbreviated" href="mailto:trnsys-users@cae.wisc.edu">trnsys-users@cae.wisc.edu</a></st1:personname>" <<st1:personname
w:st="on"><a class="moz-txt-link-abbreviated" href="mailto:trnsys-users@cae.wisc.edu">trnsys-users@cae.wisc.edu</a></st1:personname>></span></font>
<o:p></o:p></p>
</td>
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<p class="MsoNormal" style="text-align: right;"
align="right"><font face="sans-serif" size="1"><span
style="font-size: 7.5pt; font-family: sans-serif;">Asunto</span></font><o:p></o:p></p>
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<td style="padding: 0.75pt;" valign="top">
<p class="MsoNormal"><font face="sans-serif" size="1"><span
style="font-size: 7.5pt; font-family: sans-serif;">RE: [TRNSYS-users]
digging into trnflow convergence problems</span></font><o:p></o:p></p>
</td>
</tr>
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<p class="MsoNormal"><font face="Times New Roman" size="3"><span
style="font-size: 12pt;"><o:p> </o:p></span></font></p>
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<p class="MsoNormal"><font face="Times New Roman" size="3"><span
style="font-size: 12pt;"><o:p> </o:p></span></font></p>
</td>
<td style="padding: 0.75pt;" valign="top">
<p class="MsoNormal"><font face="Times New Roman" size="3"><span
style="font-size: 12pt;"><o:p> </o:p></span></font></p>
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<p class="MsoNormal"><font face="Times New Roman" size="3"><span
style="font-size: 12pt;"><o:p></o:p></span></font></p>
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<p class="MsoNormal" style="margin-bottom: 12pt;"><font
face="Times New Roman" size="3"><span style="font-size: 12pt;"><br>
<br>
<br>
</span></font><font color="navy" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: navy;">You could
try even smaller time-steps, I’ve
models with timestep: 0,03125 (n=5), 0,015625 (n=6) and even 0.0078125
(n=7).
It just takes a while before it’s finished calculating.</span></font> <br>
<font color="navy" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font>
<br>
<font color="navy" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: navy;">Kind regards,</span></font>
<br>
<font color="navy" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: navy;"> </span></font>
<br>
<font color="navy" face="Arial" size="2"><span
style="font-size: 10pt; font-family: Arial; color: navy;">Mariëlle </span></font><br>
<br>
<br>
<o:p></o:p></p>
</div>
<pre wrap="">
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<pre class="moz-signature" cols="72">--
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
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P:+1.608.274.2577
F:+1.608.278.1475
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