[TRNSYS-users] Detailed radiation model

[hotline]

Dear Lukasz,

Exactly for longwave radiation, multiple airnodes and inside userdefined emissivities of surface can only be handled by the detailed model.
If you want to calculate the MRT you need to use detailed mode for longwave radiation. But as you said, your simulation is now running without any error, so why not using detailed model? Unfortunately there is no other option.

Best,
Christoph

Von: TRNSYS-users [mailto:trnsys-users-bounces at lists.onebuilding.org] Im Auftrag von Lukasz Watly via TRNSYS-users
Gesendet: Montag, 2. Juli 2018 19:01
An: TRNSYS users mailing list at OneBuilding.org <trnsys-users at lists.onebuilding.org>
Cc: Łukasz Wątły <lukaszwatly92 at gmail.com>
Betreff: Re: [TRNSYS-users] Detailed radiation model

Dear Christoph,

Thank you very much for your reply. Finally, I have checked the surfaces and I can perform the simulations without any error.

However, I would also like to ask how I could obtain the mean radiant temperature of the 3 airnodes in the model I described in the previous email. In the manual (chapter 5.2.4.12 Radiation Modes) it is written that the longwave radiation distribution is available only for thermal zones, not airnodes - this might justify the reason why I got the same values for different airnodes.

Thus, do you know if there is the way to overcome this problem?

I would be grateful for any hints.

Kind regards,
Lukasz

2018-07-02 10:40 GMT+02:00 hotline via TRNSYS-users <trnsys-users at lists.onebuilding.org<mailto:trnsys-users at lists.onebuilding.org>>:
Dear Lukasz,

As the error says, is your building geometry not closed or not convex (Manual 5-Multizone, 5.2.7.12. Zone Radiation Modes). This problem can’t be caused by your virtual surfaces.
Please make sure that your building is convex and closed!
[cid:image001.jpg at 01D412EE.CC4B9990]

Best,
Christoph

Von: TRNSYS-users [mailto:trnsys-users-bounces at lists.onebuilding.org<mailto:trnsys-users-bounces at lists.onebuilding.org>] Im Auftrag von Lukasz Watly via TRNSYS-users
Gesendet: Freitag, 29. Juni 2018 09:42
An: TRNSYS users mailing list at OneBuilding.org <trnsys-users at lists.onebuilding.org<mailto:trnsys-users at lists.onebuilding.org>>
Cc: Łukasz Wątły <lukaszwatly92 at gmail.com<mailto:lukaszwatly92 at gmail.com>>
Betreff: [TRNSYS-users] Detailed radiation model

Dear All,

I have desgined in SketchUP a single thermal zone with 3 airnodes placed on different heights (10, 60, 110 cm). I used a Virtual Surface option to model the surfaces which, after exporting them to TRNBuild, could dissapear.

In my simulation of the zone, I would like to obtain three values of Tairnode, Toperative and mean radiant temperature for each airnode. Unfortunately, when I perform simulation in TRNSYS, all three values of mean radiant temperatures are the same. This I did with the radiation model set to standard.

When I am trying to use the detailed radiation model, I got two error informations:

- ==== zone GROUND_FLOOR_10... ... ERROR in summing view factors of surface 4. Please check geometry!!!.

- Error while creating VFM file.
+++ Note: Zones have to be convex and closed volumes.
          Surfaces must have an outwarding normal.

This causes the situation that I am unable to open the .vfm file in TRNSYS and cannot get the mean radiant temperature values.

I assume that the problem is caused by the fact that my model might not be a closed volume, due to the virtual surfaces I have created in SketchUP. So my question is, is there another way to get the MRT values for each airnodes separetely?

The view factor of surface 4 is set to 0.5 automatically, as it is one of the vertical walls.

Thank you in advance for your help.

Kind regards,
Lukasz Watly


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