[TRNSYS-users] Trnsys 16 and 17 comparison - very different energies!
d.bradley at tess-inc.com
Tue Apr 30 09:36:28 PDT 2013
We did indeed change the behavior of Type11 with Trnsys17 back to
what it had been long ago. The issue at hand is that when there is no
flow through the diverter, what should the output values be set to
(specifically the outlet temperatures)? Some claim that the output value
should be set to the input value when there is no flow. Others would
prefer the last calculated value of the output to be held until flow
starts. This causes issues if controls are based on the outlet
conditions of the diverters. There is not really a correct answer; it is
just a matter of the assumption that you wish to make when writing the
model. Our reasoning was that the temperature of the diverter should go
to the inlet temperature so that there is not a temperature difference
across the diverter under no-flow.
If you are seeing a dramatic change in energy between the two
versions, that is an indication that your controls are not operating the
same between the two. Usually, systems that exhibit this behavior are
systems that are low on thermal capacitance (i.e. there aren't enough
pipes modeled in the various hydronics). Low- or no-capacitance hydronic
loops react unrealistically quickly to control decisions and can become
unstable. I would be curious to know whether you see the same energy
differences between the v16 and v17 simulation if you add piping to your
On 4/30/2013 10:48, Marco Noro wrote:
> Dear Trnsys-users,
> I have opened a .tpf project that I had built and run in Trnsys 16
> with the new release Trnsys 17.
> With my great surprise, the energy balances (it is a solar cooling
> plant) of the same project with the two Trnsys releases are very very
> I realized that the mass flows are different, and in particular I
> think that type 11 behaves in a different way in trnsys 16 and 17.
> The problem is that in my project a have a lot of diverter, mixer,
> ecc., so: how can I solve this problem? That is, the same project
> should behave in the same way!
> I add that the problem could be also (or) in type 2 behaviour in the
> two trnsys releases...
> Thank you for your cooperation!
> Best regards
> Marco Noro
> Marco Noro, PhD
> Assistant Professor in Applied Physics
> /Department of Management and Engineering (DTG) - University of Padova/
> /stradella San Nicola, 3 - 36100 Vicenza (VI) - Italy/
> /tel. +390444 998704 - fax +390444 998884/
> /e-mail /marco.noro at unipd.it <mailto:marco.noro at unipd.it>__
> _noro at gest.unipd.it <mailto:noro at gest.unipd.it>_
> /PEC/ _marco.noro-7002 at postacertificata.gov.it
> <mailto:marco.noro-7002 at postacertificata.gov.it>_
> /web /_http://sites.google.com/site/marconoro03/_
> /skype /nereo3
> TRNSYS-users mailing list
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Thermal Energy Systems Specialists, LLC
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d.bradley at tess-inc.com
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