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<p>Hugo,</p>
<p> This kind of problem is not uncommon, especially when doing
combined airflow/thermal simulations. I have not run into the
problem of convergence problems inside of Type56, which is a
little surprising. I thought that I had gotten all of the possible
TRNSYS errors at least once! The solution I usually use is to
implement a short time step (1 minute perhaps) and then to put a
delay component (like Type661 or Type150) between Type56's output
temperatures and Type98's inputs. It is a bit of a cheat but I
think with a short timestep it is realistic enough. We assume that
air entering a Type56 zone immediately mixes thermally with the
zone air and that thermostats react immediately. When you add the
automatic heating/cooling that Type56 can do you are further
assuming that the mechanical systems can react instantaneously and
provide exactly the right amount of heating and cooling. I don't
think it is unreasonable to introduce back a small time delay in
order to get the whole thing to converge.</p>
<p>kind regards,</p>
<p> David</p>
<p> <br>
</p>
<div class="moz-cite-prefix">On 01/07/2021 09:05, Hugo GEOFFROY via
TRNSYS-users wrote:<br>
</div>
<blockquote type="cite"
cite="mid:MR2P264MB0420CF201066DCC1800447D2D8AF0@MR2P264MB0420.FRAP264.PROD.OUTLOOK.COM">
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<p class="MsoNormal"><span lang="EN-US">Hello, <o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">We need to modelize a
few stories building in a cosimulation TRNSYS/CONTAM.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The thermal part is
handled by TRNSYS with a Type 56 and the aeraulic part by
CONTAM with a Type 98.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The model works but
encounters several convergence problems as noticed in the
*.lst file. The model includes daily windows openings that
coincide with the convergence problem occurrences.
Furthermore, most of the rooms are heated with an ideal
system of which power is limited to 100 W.m-2. The setpoint
temperature is fixed thanks to a schedule in the "Heating
type manager"<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Removing this heating
resolves the convergence problem, but these convergence
faults cannot be fixed by reducing the time step, modifying
the number of iterations, or convergence tolerance of
Simulation Studio. The following error message shows that
the faults are not directly generated in the "simulation
studio" calculation but by Type 56 and are indeed a
consequence of the heating of the building Type 56 model.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:black;mso-fareast-language:FR"
lang="EN-US">--------------------------------------------------------<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:black;mso-fareast-language:FR"
lang="EN-US">*** Notice at time : 130.000000<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:black;mso-fareast-language:FR"
lang="EN-US"> Generated by Unit : 56<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:black;mso-fareast-language:FR"
lang="EN-US"> Generated by Type : 56<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:black;mso-fareast-language:FR"
lang="EN-US"> Message : TIME = 130.000
More than 6 iterations for internal regulation
HEATING/COOLING<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:black;mso-fareast-language:FR"
lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:black;mso-fareast-language:FR"
lang="EN-US"> <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:black;mso-fareast-language:FR"
lang="EN-US">*** Warning at time : 130.000000<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:black;mso-fareast-language:FR"
lang="EN-US"> Generated by Unit : 56<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:black;mso-fareast-language:FR"
lang="EN-US"> Generated by Type : 56<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:black;mso-fareast-language:FR"
lang="EN-US"> Message : TIME = 130.000
CONVERGENCE NOT ATTAINED USING INTERNAL REGULATION FOR
HEATING/COOLING<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:black;mso-fareast-language:FR"
lang="EN-US">-------------------------------------------------------<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">This fault appears while
the *.dck maximal iteration is fixed to 500.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Has somebody already
encountered this problem in Simulation studio ?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Is it possible and if
yes, how the numerical parameters (tolerance of convergence,
number of iterations, …) of Type56 can be modified? Do you
have any idea for another solution to solve this problem?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal">Thank you<o:p></o:p></p>
</div>
<br>
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<pre class="moz-signature" cols="72">--
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
3 North Pinckney Street - suite 202
Madison, WI 53703 USA
P:+1.608.274.2577
<a class="moz-txt-link-abbreviated" href="mailto:d.bradley@tess-inc.com">d.bradley@tess-inc.com</a>
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