Re: [TRNSYS-users] Modelisation of atrium with TRNSYS 3D

[hotline <hotline@Transsolar.com>]

Dear Noe,

the stratification will be not calculated automatically. You should define a coupling in between the airnodes. There is no universal formula here. Coupling depends on various factors:

• Temperature differences between the air nodes -> Is there invasion?
  
• Mechanical ventilation -> where is the air inlet and outlet?
  
• Natural ventilation -> where are the openings?

For each case you need to define a control strategy and a mass balance. For natural and mechanical ventilation you should define the way of airflow. Trnsys is not checking the air mass balance when using coupling.

For example: if the air inlet is at the bottem and outlet at top, the fresh air with Tambient and mflow_mech is entering into Airnode 1 and gets completly mixed. From there mflow_mech goes with Tairnode1 to Airnode 2 and gets completly mixed. Finally the airflow reaches Airnode 3 with Tairnode2 and gets completly mixed.

For atirums we recommend to use detailed radiation mode for direct and longwave radiation. For this you need 3D-Geometry mode.

best,

Christoph

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Von: TRNSYS-users <trnsys-users-bounces@lists.onebuilding.org> im Auftrag von Noé STEMART (INSA) via TRNSYS-users <trnsys-users@lists.onebuilding.org>
Gesendet: Mittwoch, 15. Januar 2020 23:32
An: trnsys-users@lists.onebuilding.org <trnsys-users@lists.onebuilding.org>
Cc: Noé STEMART (INSA) <noe.stemart@insa-strasbourg.fr>
Betreff: [TRNSYS-users] Modelisation of atrium with TRNSYS 3D

 

Dear Trnsys users,

I am trying to modelise thermal stratification with TRNBuild (type 56), in high volumes (like an atrium for example). To simulate this phenomena, I'm using the plugin TRNSYS 3D on sketchup to modelize a stack of zones (transformed in TRNBuild on a stack of airnodes) by assigning "VirtualSurface" to the surface between the 2 zones. This one is delated when the 3D construction is imported in TRNBuild. A simple example I’m using is a building with two levels of 5 meters each, without windows.

I would like to know how to study stratification in TRNSYS 18.

Will stratification be calculated automatically ?
Or do I have to put an air coupling between airnodes (which input with which equation ?) ?
Or do I change something in "Radiation modes of thermal zone" or "Geometry modes" in TRNBuild ?

Regarding radiation, will having 3 or more airnodes in the zone be problematic ?

Thanks a lot for your help,
Best regards

Noé



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