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

[Karol Bandurski]

Dear Marion, David, Christoph

 

Thank you very much for your help!

 

It seems to me that Marion tip is important: internal, solar and longwave
heat gains could imply the results which was strange for us (temperature on
outside surface of TABS higher then air temperature in zone and water
temperature).

 

If we found something new then we will write!

 

Regards,
Karol

 

From: Marion Hiller [mailto:Hiller at Transsolar.com] 
Sent: Thursday, January 25, 2018 2:56 PM
To: TRNSYS users mailing list at OneBuilding.org
Subject: Re: [TRNSYS-users] Active layer/boundary condition - strange
results

 

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>; 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 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
Cc: Karol Bandurski <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?

 

2.	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

 <http://www.put.poznan.pl/~karol.bandurski>
www.put.poznan.pl/~karol.bandurski

 

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