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

[karol.bandurski at put.poznan.pl]

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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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 <mailto:d.bradley at tess-inc.com> 
 
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