[TRNSYS-users] convergence problems because of high ventilation heat flux

[David BRADLEY]

Karol,

  I would suggest sending the project and the files needed to run it to 
your distributor. It may be that we need to dig inside the code a bit to 
find out exactly what is not converging.

kind regards,

  David


On 08/17/2022 03:28, karol.bandurski--- via TRNSYS-users wrote:
>
> Dear David and Arian,
>
> Thank you for your quick response.
>
>  1. Unfortunately changing time step doesn’t help (we change form 1h
>     to 5 min).
>  2. We also try switch off internal calculation of convection
>     coefficient on ceiling but it not help, moreover it is not
>     solution for us as we simulate TABS. However we will switch off
>     internal calculation of convection coefficient for windows and
>     external walls.
>
> Do you have any other idea?
>
> Do you think that some settings in Control Cards could help (change in 
> numerical approach)?
>
> Best,
> Karol
>
> *From:*David BRADLEY <>
> *Sent:* Tuesday, August 16, 2022 8:38 PM
> *To:* TRNSYS users mailing list at OneBuilding.org 
> <trnsys-users at lists.onebuilding.org>
> *Cc:* karol.bandurski at put.poznan.pl
> *Subject:* Re: [TRNSYS-users] convergence problems because of high 
> ventilation heat flux
>
> Karol,
>
>  Check your assumption about the way that the inside heat transfer 
> coefficients are being calculated on the zone surfaces. If you have 
> allowed the convection coefficients to be internally calculated then 
> you can end up with convergence problems inside 56, particularly on 
> inside window surfaces and even more particularly if the glass has a 
> high u-value.
>
> kind regards,
>
>  David
>
> On 08/16/2022 09:50, karol.bandurski--- via TRNSYS-users wrote:
>
>     Dear Experts.
>
>     We get convergence problem in Type 56. According to our
>     investigation source of error is sudden increase of ventilation
>     flow in our schedule and ventilation air temperature about 3 K
>     lower then room air temperature.
>
>     We would like to keep this control schedule and the same time
>     avoid convergence problem.
>
>     So far we have increase indoor air heat capacity in zones (five
>     times), it help a bit.
>
>     Do you  have any other ideas what we could do?
>
>     Should we change something in Control Cards?
>
>     Best,
>
>     Karol
>
>     ---------------------------------------------------------------------------
>
>     Karol BANDURSKI Ph.D, Assistant Professor
>
>     Faculty of Environmental and Energy Engineering
>
>     Division of Heating, Air Conditioning and Air Protection
>
>     Poznan University of Technology
>
>     https://www.researchgate.net/profile/Karol_Bandurski
>     <https://www.researchgate.net/profile/Karol_Bandurski>
>
>     ***
>
>     dr inż. Karol BANDURSKI, Adiunkt
>
>     Wydział Inżynierii Środowiska i Energetyki
>
>     Zakład Ogrzewnictwa, Klimatyzacji i Ochrony Powietrza
>
>     Politechnika Poznańska
>
>
>
>     _______________________________________________
>
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>
>     TRNSYS-users at lists.onebuilding.org
>
>     http://lists.onebuilding.org/listinfo.cgi/trnsys-users-onebuilding.org
>
> -- 
> ***************************
> David BRADLEY
> Principal
> Thermal Energy System Specialists, LLC
> 3 North Pinckney Street - suite 202
> Madison, WI  53703 USA
> P:+1.608.274.2577
> d.bradley at tess-inc.com
> http://www.tess-inc.com
> http://www.trnsys.com
>
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> TRNSYS-users at lists.onebuilding.org
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-- 
***************************
David BRADLEY
Principal
Thermal Energy System Specialists, LLC
3 North Pinckney Street - suite 202
Madison, WI  53703 USA

P:+1.608.274.2577
d.bradley at tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com
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