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Dear Fernando,<br>
I have had some troubles with the stability of the Type60 heat
exchanger model too. I think that the algorithm for the natural
convection heat transfer coefficient on the outside of the exchanger
is at fault. One workaround would be to use Type534 from the TESS
Storage Tank library in place of Type60 if you have access to it.
You might also try changing the Type60 internal time step. Lastly,
check carefully over your tank and heat exchanger configuration to
make sure that they are correct. Putting a very big heat exchanger
into a small tank can cause the kind of instability in calculating
the heat exchanger UA.<br>
<br>
The answer to your question about freezing depends on the
component. Some components may deal with freezing phenomena while
others do not. None of the solar water heating components in the
standard TRNSYS library account for freezing of the working fluid.
Having done some research work on it, I can tell you that it is
enormously difficult to predict when freezing will become a problem
because it has almost everything to do with how the system is
installed, not how the system is designed. <br>
Best,<br>
David<br>
<br>
<br>
On 11/12/2010 09:59, Sancho,Fernando wrote:
<blockquote cite="mid:A9BC93E3-4A77-4AF7-BF14-0F6A60F370C6@mimectl"
type="cite">
<div><font color="#000000" face="Arial" size="2"> Dear
Trnsys-users,</font></div>
<div> </div>
<div><font face="Arial" size="2">Im using Type 60 as a Tank and
have a convergence problem with the solar heat exchanger just
when I use glycol in it. </font></div>
<div> </div>
<div><font face="Arial" size="2">error <strong>non convergences
for Hx 1. Final UAHx value =</strong> 345.adjfhadgfg</font></div>
<div> </div>
<div><font face="Arial" size="2">That is a reported problem in the
list, the solutions indicated were normally about "adding
pipes in the solar loops", to be sure that in a certain time
step a portion of fluid is not going in and out the pump or
similar problems. Or decresing the internal time steps of the
tank.</font></div>
<div><font face="Arial" size="2">I tried a wide rate of values for
both variables but it didn´t work. And that happens just not
always in the same time step, it depends on the limit of my
simulation, i find that strange as well. </font></div>
<div><font face="Arial" size="2">So i´m getting into the "physics
behind" during the weekend, but ...hat anyone any advice?</font></div>
<div> </div>
<div><font face="Arial" size="2">And, about the same situation ,
with water in der solar loop everything runs with no
problems...but can someone explains to me how deals TRNSYS
with a freezed fluid in the collector?</font></div>
<div> </div>
<div><font face="Arial" size="2">Thanks a lot!!! Enjoy the weekend</font></div>
<div><font face="Arial" size="2">(David, thank you, I added my
new type succesfully after testing)</font></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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