[TRNSYS-users] WG: Re: Simulation of false ceiling: influence on inertia

Wed Oct 19 00:45:31 PDT 2011

Marion,

Could you explain what kind of heat or mass transfer exist  by Virtual surface:

1.       Radiation?

2.       Convection?

3.       Mass transfer?

4.       Neither? – virtual surface is perfect insulator

If 1-3  :  how values of these magnitude are calculated?

Regards

------------------------------------------------

Karol Bandurski MSc.

 <http://www.ee.put.poznan.pl/> Institute of Environmental Engineering

Poznan University of Technology

 <http://www.ee.put.poznan.pl/> www.ee.put.poznan.pl

www.put.poznan.pl <http://www.put.poznan.pl/> 

From: Marion Hiller [mailto:hiller at transsolar.com] 
Sent: Wednesday, October 19, 2011 9:00 AM
To: trnsys-users
Subject: [TRNSYS-users] WG: Re: Simulation of false ceiling: influence on inertia

David and Joke, 

the coupling airflows between two airnodes belonging two different zones are defined by adjacent surfaces (walls/windows). 

Coupling airflows between two airnodes of the same thermal zone can be defined in the regime. A new button coupling becomes active. 

Concerning the false ceiling problem of Joke, do you use the detailed radiation modes? 

I assume not because you do have a shading and the distribution isn’t that important anymore, right? 

If you use standard radiation mode I suggest that your airnode “false ceiling” doesn’t cover the whole 

Ceiling area, but only 70 %. The remaining separating vertical surface between the airnode false ceiling and room 

could be defined as a resistance wall with a high conductivity. 

Virtual surfaces are defined in Trnsys3D, but they don’t exist in the thermal model. Thus no heat transfer through the virtual surface 

can be calculated. Virtual surfaces are defined for creating closed volumes for airnodes such that the volume calculation of the airnode 

is performed correctly. 

Best, 

Marion 

Dipl.-Ing. Marion Hiller 
TRANSSOLAR: KlimaEngineering - Technologien für energieeffizientes Bauen und Nutzerkomfort in Gebäude 
Munich - New York - Stuttgart + 49.711.67976.0 

Transsolar Energietechnik GmbH, Curiestrasse 2, 70563 Stuttgart 
Amtsgericht Stuttgart - HRB 23347, Steuernummer 99073/00911, USt-IdNr.: DE152272639 

Geschäftsführer: Dipl.Ing. Matthias Schuler, Dipl.Ing. Thomas Auer, Dipl.Phys. Stefan Holst, Prof. Dipl.-Ing. Bleicher  

  _____  

Von: David BRADLEY [mailto:d.bradley at tess-inc.com] 
Gesendet: Dienstag, 18. Oktober 2011 19:28
An: Joke De Beuckelaer
Cc: TRNSYS-users
Betreff: Re: [TRNSYS-users] Simulation of false ceiling: influence on inertia 

Joke,
 This came up yesterday as well (how to make a coupling air flow across a virtual surface) and I unfortunately don't know the answer. I am looking into it and will let you know what I learn.
Best,
 David

On 10/18/2011 11:23, Joke De Beuckelaer wrote: 

David, 

Thanks for the answer. But the problem is that it isn't a 100% false ceiling but about 70%. 

So what do I do with the "air - air contact" between the two zones. 

Does Trnsys takes this into account when I model it with a virtual surface in google sketchup or do the airnodes then have to belong to the same thermal zone? 

Greetings, 

Joke 

  _____  

Van: David BRADLEY [d.bradley at tess-inc.com]
Verzonden: maandag 17 oktober 2011 18:38
Aan: Joke De Beuckelaer
CC: TRNSYS-users
Onderwerp: Re: [TRNSYS-users] Simulation of false ceiling: influence on inertia 

Joke,
 I like to simulate this situation as two thermal zones; the conditioned zone below and the plenum zone above. Because the suspended ceiling basically has no mass to it, I simulate it as a wall made up of a single purely resistive (ie massless) layer.
best,
 David

On 10/14/2011 03:44, Joke De Beuckelaer wrote: 

Dear all, 

Can anyone help me what’s the best way to simulate a suspended false ceiling? 

The goal is to simulate a class room where the comfort is assured by using night ventilation. However for acoustic reasons we need a false ceiling. 

I want to know the percentage of suspended false ceiling is possible in order to have still enough inertia from the concrete ceiling. 

Is the best way just to define two different types of ceiling (1. A concrete ceiling and 2.a false ceiling (concrete + air layer + false ceiling)) or has anyone another idea? 

Is it possible to draw for example some obstructions in Google sketch up and then to define 3 air nodes in trnsys. One air node above the suspended false ceiling; one air node in the middle of the room and one air node representing the opening window? 

Will it take into account the less availability of the inertia of the concrete ceiling? 

Hoping for an answer, 

Joke De Beuckelaer 

project engineer mep 

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David BRADLEY
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Madison, WI  53703 USA

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

http://www.tess-inc.com
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 ALWAYS LOOKING FOR GREAT PEOPLE      

****DISCLAIMER****
This communication is confidential and for the sole useof the addressee. If you are not the intended recipient,
please immediately notify the sender by e-mail at the address shown and then delete it from your system 
without copying, disclosing or forwarding its contents. Thank you. 

-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley at tess-inc.com

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