Different boundary condition in CSV file compared to input in FDS code

[elangsz]

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

[drjfloyd]

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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[elangsz]

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 — Reply to this email directly, view it on GitHub <#13295>, or unsubscribe https://github.com/notifications/unsubscribe-auth/ADBUZ4LJZRXYAD5663T7GUDZQLGNBAVCNFSM6AAAAABMFQEY4GVHI2DSMVQWIX3LMV43ASLTON2WKOZSGQ2TINZQHE2DCOI . You are receiving this because you are subscribed to this thread.Message ID: @.>

ive edited the issue by attaching the FDS file along with the CSV file, thankyou for the reminder

[drjfloyd]

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.

[drjfloyd]

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.

[elangsz]

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.

Ah i see, thankyou very much! i have a couple of questions, if i may

1. "use the solid phase quantity NORMAL VELOCITY and integrate it over the area of the vent." how can i do this in FDS?
2. "As noted use XYZ instead of XB when you have a point device", so this will measure a temperature at a certain "point" correct? because i thought by useing DEVC XB i can get the average temperature of the inlet/outlet of a surface. turns out i was mistaken

[drjfloyd]

Please read the User's Guide. It answers both of your questions.

[elangsz]

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!