[TRNSYS-users] Convergence problem for the internal regulation

[Hugo GEOFFROY]

Hello Jean,

Thank you for this solution.
Actually, we have numerous windows in the model.
It could be a good option to help the model convergence.

Kind regards,

Hugo

De : TRNSYS-users <trnsys-users-bounces at lists.onebuilding.org> De la part de Jean Marais via TRNSYS-users
Envoyé : vendredi 8 janvier 2021 09:47
À : TRNSYS users mailing list at OneBuilding.org <trnsys-users at lists.onebuilding.org>
Cc : Jean Marais <jeannieboef at gmail.com>
Objet : Re: [TRNSYS-users] Convergence problem for the internal regulation

You could also try staggering the window opening events so that they don't all open at once, but slightly delayed from one another.

Am Do., 7. Jan. 2021 um 22:36 Uhr schrieb David BRADLEY via TRNSYS-users <trnsys-users at lists.onebuilding.org<mailto:trnsys-users at lists.onebuilding.org>>:

Hugo,

  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.

kind regards,

 David


On 01/07/2021 09:05, Hugo GEOFFROY via TRNSYS-users wrote:
Hello,

We need to modelize a few stories building in a cosimulation TRNSYS/CONTAM.
The thermal part is handled by TRNSYS with a Type 56 and the aeraulic part by CONTAM with a Type 98.

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"

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.

--------------------------------------------------------
*** Notice at time        :       130.000000
    Generated by Unit     :    56
    Generated by Type     :    56
    Message               :  TIME =     130.000  More than 6 iterations for internal regulation HEATING/COOLING


*** Warning at time       :       130.000000
    Generated by Unit     :    56
    Generated by Type     :    56
    Message               :  TIME =     130.000  CONVERGENCE NOT ATTAINED USING INTERNAL REGULATION FOR HEATING/COOLING
-------------------------------------------------------

This fault appears while the *.dck maximal iteration is fixed to 500.

Has somebody already encountered this problem in Simulation studio ?
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?

Thank you


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