[TRNSYS-users] Active layer/boundary condition - strange results

[Marion Hiller]

Dear Karol,

Keep in mind that boundary identical means that the backside gets the same heat flux (absorbed solar + internal gains + longwave exchange from surfaces) as the front side of the surface!
In your email you mentioned temperatures only, but you did say anything about the heat fluxes.
I suspect that the heat flux causes the temperature increase.

Kind regards,

Marion

From: TRNSYS-users [mailto:trnsys-users-bounces at lists.onebuilding.org] On Behalf Of Karol BANDURSKI via TRNSYS-users
Sent: Donnerstag, 25. Januar 2018 12:30
To: hotline <hotline at Transsolar.com>; 'TRNSYS users mailing list at OneBuilding.org' <trnsys-users at lists.onebuilding.org>; trnsys-users at cae.wisc.edu
Cc: Karol BANDURSKI <karol.bandurski at put.poznan.pl>; katarzyna.palaszynska at put.poznan.pl
Subject: Re: [TRNSYS-users] Active layer/boundary condition - strange results

Dear Christoph,

Thank you for response!

But we need to be more clear:

When we set:

  *   boundary conditions = IDENTICAL
  *   AIR temperature in zone is about 24 C
  *   Temperature of inlet water (active layer) is about 18 C (and outlet almost 19 C)
  *   Convective heat transfer coefficient on back surface is set FLOOR

Then temperature on back surface is about 26 C. In other words Tso is higher than Tsi and water temperature, while there is no internal heat gains. Why?

Kind regards,
Karol


From: hotline [mailto:hotline at Transsolar.com]
Sent: Thursday, January 25, 2018 12:02 PM
To: TRNSYS users mailing list at OneBuilding.org <trnsys-users at lists.onebuilding.org<mailto:trnsys-users at lists.onebuilding.org>>; trnsys-users at cae.wisc.edu<mailto:trnsys-users at cae.wisc.edu>
Cc: Karol Bandurski <karol.bandurski at put.poznan.pl<mailto:karol.bandurski at put.poznan.pl>>; katarzyna.palaszynska at put.poznan.pl<mailto:katarzyna.palaszynska at put.poznan.pl>
Subject: Re: [TRNSYS-users] Active layer/boundary condition - strange results

Dear Karol and Katarzyna,

If boundary conditions = IDENTICAL, the surface temperatures of the active wall Tsi and Tso will only be identical, if:

  *   Wall construction is symmetrical
  *   Convective heat transfer coefficients (front and back) are the same

Best
Christoph Stetter

__________________________________________________________________________________________________

Christoph Stetter M.Eng.

Transsolar Energietechnik GmbH
Curiestraße 2
70563 Stuttgart
http://www.transsolar.com<http://www.transsolar.com/>
Transsolar: KlimaEngineering- Technologien für energieeffizientes Bauen und Nutzerkomfort in Gebäuden
Stuttgart - München - New York - Paris
Geschäftsführer :Diplom-Ingenieur Matthias Schuler, Diplom-Ingenieur Thomas Auer, Diplom-Physiker Stefan Holst, Diplom-Betriebswirt Dieter Schnelle
Eingetragen beim Amtsgericht Stuttgart HRB 23347,
Steuernummer: 99073/00911,USt-IdNr.: DE 152272639

Von: TRNSYS-users [mailto:trnsys-users-bounces at lists.onebuilding.org] Im Auftrag von Karol Bandurski via TRNSYS-users
Gesendet: Montag, 22. Januar 2018 12:44
An: trnsys-users at cae.wisc.edu<mailto:trnsys-users at cae.wisc.edu>
Cc: Karol Bandurski <karol.bandurski at put.poznan.pl<mailto:karol.bandurski at put.poznan.pl>>
Betreff: [TRNSYS-users] Active layer/boundary condition - strange results

Dear Users and Developers,

We would like to model active layer as component of TABS.
Now our model is one zone with active layer in ceiling. Adiabatic condition/IDENTICAL for all internal partition and set. We have one external wall.


  1.  We would like to keep neighborhood zones in the same AIR temperature. But when we set boundary condition to IDENTICAL over TABS, then outer surface of this partition has higher temperature then indoor air temperature and active layer water temperature... -Why?


  1.  The situation is better if we set convective heat transfer coefficient, on outer surface of TABS to 0.001. If we understand, it is mean direct contact between air and surface. So if there are adiabatic/identical condition: outer SURFACE temperature of TABS has the same temperature as AIR inside modelled zone. But our aim is to keep identical inside and outside AIR temperature, not SURFACE temperature... How we can do it?

Kind regards,
Karol
--------------------------------------------------------------------
Karol BANDURSKI M. Sc.
Faculty of Civil and Environemntal Engeneering
Division of Heating, Air Conditioning and Air Protection
Poznan University of Technology
https://www.researchgate.net/profile/Karol_Bandurski
www.put.poznan.pl/~karol.bandurski<http://www.put.poznan.pl/~karol.bandurski>

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