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<p>Behzad,</p>
<p> You have caught the most common error (too long a time step)
and I must admit that I am not sure why reducing the timestep so
far did not make the simulation start converging again. The reason
that reducing the time step helps is that if you have pumps (or
fans) that are pushing a greater volume of fluid around a loop in
one time step than the devices that have thermal capacitance can
hold then the problem can become numerically unstable. Devices
that have thermal capacitance are storage tanks, pipes, and the
building (if there is one). <br>
</p>
<p> I think you'll need to use the TRACE tool (the icon with the
foot prints in the toolbar on the left of the simulation studio).
Activate TRACE on the components that are being flagged as not
converging in the error/warning log. What TRACE does is to write
the values of all the parameters, inputs, and outputs for each of
the activated components to the *.lst file at every iteration. By
looking at the outputs and inputs from one iteration to the next,
you can tell specifically which one(s) are causing problems.
Unfortunately TRACE writes a lot of information to the *.lst file
and it can be a bit hard to find what you are looking for.
However, it is a handy tool in cases like this. <br>
</p>
<p>kind regards,</p>
<p> David</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 12/10/2018 08:17, up201700037 via
TRNSYS-users wrote:<br>
</div>
<blockquote type="cite"
cite="mid:5b184da2aac582485aa82b0837368c83@fe.up.pt">Dear Users,
<br>
<br>
I am simulating a building which is cooled or heated by heat
generated by sollar collectors and stored in Stratified tank
type4. The simulation goes well with 6oo liters volume of the
tank. Then i decided to reduced the size of the tank to reach an
optimum volume. I tried for the cases of 500 to 100 liters and got
the results but when reducing the volume to 50 liters the
simulation diverges because of many warnings stating that many
types in the simulation did not converge at this time step(30s).
Therefore, i decided to decrease the timestep. I repeated the
simulation even for the least time stem defined in trnsys but it
did not converge. I also tried to change the relaxation factor but
didnt work. I read that some people suggest that if i increase the
convergence criteria or the limit number for warnings in the
control cards, it will converge but it is not solving the problem.
Actually it seems like cheating. Please help me to solve the
problem.
<br>
<br>
Best regards,
<br>
Behzad shahzamanian sichani
<br>
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<br>
<br>
</blockquote>
<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
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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