Dear Marion,
Thank you for your expert feedback, I have corrected my sketch (enclosed), could you write me if now it is ok?
Kind regards,
Karol
From: Marion Hiller [mailto:Hiller@Transsolar.com]
Sent: Monday, May 3, 2021 9:13 AM
To: TRNSYS users mailing list at OneBuilding.org <trnsys-users@lists.onebuilding.org>
Cc: David BRADLEY <d.bradley@tess-inc.com>; Karol BANDURSKI <karol.bandurski@put.poznan.pl>
Subject: AW: [TRNSYS-users] VirtualSurface
Karol,
General information on virtual surfaces:
- The reason for adding a virtual surface is that the volume of an airnode has to be closed with respect to geometry such that the volume of the airnode can be calculated.
- A virtual surface is not part of the thermal model of Type 56
-> no heat transfer, no interaction with shortwave and longwave radiation
- Solar radiation is distribution to all surfaces of all airnodes of thermal zone
(Note: virtual surfaces aren’t considered as they are not part of the thermal model)
- longwave radiation is distributed to and exchanged with
a) all surfaces of an airnode if the longwave radiation mode = standard
b) all surfaces of all airnodes of thermal zone if the longwave radiation mode = detailed
(Note: virtual surfaces aren’t considered as they are not part of the thermal model)
Thus, your sketch lacks the distinction regarding the longwave radiation mode.
The sketch on the right for one zone with two airnodes is correct for longwave radiation mode = detailed only.
Best,
Marion
Dipl.-Ing. Marion Hiller
+49 711 679 76 32 | hiller@transsolar.com
Transsolar
Stuttgart | Munich | Paris | New York
Transsolar Energietechnik GmbH | Curiestrasse 2 | 70563 Stuttgart | Germany
CEO: Matthias Schuler, Thomas Auer, Stefan Holst, Dieter Schnelle
Registered at Amtsgericht Stuttgart HRB 23347 | USt-IdNr.: DE 152272639
Karol,
I think your picture is correct.
The process for setting it up can be a little confusing. My understanding of how to set up the second case is to draw both Zone1 and Zone2 separated by a VirtualSurface in Trnsys3d. I assume there is some way of doing the same in TRNLizard but I'm afraid I'm not familiar with that tool. Once you import the *.idf file into TRNBuild, the virtual surface will disappear. You then add Zone2 to Zone1 so that they become two airnodes of a single zone. To do this, you open the zone/airnode that you're going to move and you click on the button in the upper left corner that looks like a u-shaped arrow.
Since the virtual surface that separates the two airnode has disappeared you no longer have an adjacent surface through which to define the air flow coupling. Instead, you click on the "coupling" button in the airnode window (upper right) and define the coupling there.
best,
David
On 04/30/2021 08:01, Karol BANDURSKI via TRNSYS-users wrote:
Dear Expert,
I have tackled this topic a few times but I am still not sure if I understand the idea of Virtual Surface.
Could you write me if enclosed sketch properly describe heat exchange in the zone in the context of Virtual surface?
Kind regards,
Karol
--------------------------------------------------------------------
Karol BANDURSKI Ph.D.
Faculty of Environmental and Energy Engineering
Division of Heating, Air Conditioning and Air Protection
Poznan University of Technology
www.put.poznan.pl/~karol. bandurski
https://www.researchgate.net/profile/Karol_Bandurski
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