Damien,
As far as your question 2/ is concerned, my guess is that the time
step in question did not converge. When components do not converge
after a certain number of iterations, TRNSYS stops iterating and
makes the "end of time step" call, then goes on to the next time
step. In earlier versions of TRNSYS, this was referred to as the
"post convergence" call but really that is poorly named since that
call is made whether or not convergence was reached.
Check to make sure that there is some thermal capacitance in your
flow loop and that your time step is not too big. If you have
simplified the loop by omitting the piping or if you are using too
long a time step convergence of the controls becomes very
challenging.
Kind regards,
David
On 5/7/2013 06:27, Damien Casetta
wrote:
Hi,
Thanks Ciarán for your help. However, the .lst
file doesn't say much more about the errors.
1/ The unit number (24) is not written on the input file.
Plus, the associated type changes (and is not in the current
simulation in most cases) each time I get this error. Let's
forget about this then.
2/ The second error ("a negative flow rate was encountered")
has retained my attention (first of all because it stops the
simulation) and I would be glad if I could draw your attention
on this issue. Please find attached the TRNSYS model and refer
to it for unit and type numbers. As you can see I have traced
the critical components to better understand the error. Here
is what happens :
- During post-convergence call, mass balance is
not achieved through the first tee piece (Type 11, Unit 55).
Input flow rates are 339,8 kg/hr and 0 kg/hr whereas output
flow rate is 339,6 kg/hr (equal to iteration 0 and 1 of the
current time step and to the converged value of the previous
time step). Right after this, in the lst file, a fatal error
is detected (no unit specified), as attached in my previous
message. Does it occur at iteration 0 of the next time step?
Why is it post-convergence call (current time step) if a
simple mass balance is not checked?
Feel free to ask if you need more info about the project,
Thanks a lot for helping me on this,
Have a nice day,
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Thermal Energy Systems Specialists, LLC
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