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Different boundary condition in CSV file compared to input in FDS code #13295
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Please attach your fds input file as the actual file and not screenshots.
Change the extension from fds to txt and you can attach it to a comment.
…On Wed, Aug 7, 2024, 22:00 elangsz ***@***.***> wrote:
Hello
I came from the last two issues posted before, the object of simulation is
still the same which is simulating the airflow distribution inside an
electrical panel that contains a soft starter that emits heat, along with 3
exhaust fan to circulate air so the the panel doesn't overheat. Ive noticed
that there are difference in flowrate values in the CSV files compared to
the FDS input code. Are there any reason for this? ill post the screenshots
along with the FDS code file + CSV file. As you can see, the inlet and
outlet flowrate are different in the CSV file whereas its supposed to be
the same, and also the exhaust discharge temperature reaches 140 C where in
the simulation its maksimum air temperature is about 45 C
*SMV results*
image.png (view on web)
<https://github.com/user-attachments/assets/13ffbfa8-ed2f-416d-af48-28f9bc26e666>
*FDS screenshots*
image.png (view on web)
<https://github.com/user-attachments/assets/fc772814-ecd2-46b2-9ea7-a95a2963d7b2>
image.png (view on web)
<https://github.com/user-attachments/assets/90bd2f55-73b1-43c9-abb5-21622d0b204e>
image.png (view on web)
<https://github.com/user-attachments/assets/ae303a88-3412-457c-8c6a-546e7dd34c6a>
image.png (view on web)
<https://github.com/user-attachments/assets/eb6b65fb-9943-46df-aae5-3ca01f3639bd>
*CSV screenshots*
image.png (view on web)
<https://github.com/user-attachments/assets/4f153ba2-2e2f-4186-92a1-166a032acdd8>
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ive edited the issue by attaching the FDS file along with the CSV file, thankyou for the reminder |
VOLUME FLOW is a gas phase device. It will actually be measuring the flow in the first row of grid cells above your soft starter outlet which is on an OBST inside the enclosure. All the other outlet flows are located on the walls of the enclosure. There isn't any real potential for entrainment to happen within that first grid cell for the other outlets as all the cells around those outlets vents are also solid walls. For the soft starter outlet, air can be entrained from below into the the outer ring of grid cells for the outlet. For getting the flow that is only normal to wall at the wall use the solid phase quantity NORMAL VELOCITY and integrate it over the area of the vent. TEMPERATURE is a point measurement as are most output quantities except for things like VOLUME FLOW or when using POINTS. Unless you are using a SPATIAL_STATISTIC or the device actually needs an XB, you should use XYZ. If I add devices using XYZ instead of XB, then the temperatures are also correct. I have a feeling that the value you see is because your XB is spanning meshes but we should still be returning something sensible. Will have to look into what is going on. |
As noted use XYZ instead of XB when you have a point device. The 140 was 4 x 35 (your TMPA) as the XB spanned four meshes causing FDS to aggregate the value of the device over each mesh. The commit will prevent this in future releases by setting XYZ to the center of XB when a DEVC has POINTS=1 and no SPATIAL_STATISTIC. |
Ah i see, thankyou very much! i have a couple of questions, if i may
|
Please read the User's Guide. It answers both of your questions. |
Sorry for the late reply, ok ill make sure to read the user guide again and check the references you mentioned. Thankyou very much! |
Hello
I came from the last two issues posted before, the object of simulation is still the same which is simulating the airflow distribution inside an electrical panel that contains a soft starter that emits heat, along with 3 exhaust fan to circulate air so the the panel doesn't overheat. Ive noticed that there are difference in flowrate values in the CSV files compared to the FDS input code. Are there any reason for this? ill post the screenshots along with the FDS code file + CSV file. As you can see, the inlet and outlet flowrate are different in the CSV file whereas its supposed to be the same, and also the exhaust discharge temperature reaches 140 C where in the simulation its maksimum air temperature is about 45 C
FDS File
LCP_4.zip
CSV File
LCP_4_devc (3).csv
SMV results
FDS screenshots
CSV screenshots
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