[TRNSYS-users] Convergence problem for the internal regulation

[Jean Marais]

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>:

> 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
>
> _______________________________________________
> TRNSYS-users mailing listTRNSYS-users at lists.onebuilding.orghttp://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org
>
> --
> ***************************
> David BRADLEY
> Principal
> Thermal Energy Systems Specialists, LLC
> 3 North Pinckney Street - suite 202
> Madison, WI  53703 USA
>
> P:+1.608.274.2577d.bradley at tess-inc.com
> http://www.tess-inc.comhttp://www.trnsys.com
>
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