Is it possible to make a supply terminal become a pressure release opening ?

[maria-justo-alonso]

Hello,

I need help defining a vent behavior in my FDS model. I have a case where the ventilation is controlled by a smoke detector. When the temperature detected by the smoke detector exceeds 68°C, I would like the fan supplying a constant airflow rate to stop, and the vent opening should behave as if it is a leak.

I attempted the following approach, but when the temperature exceeds 68°C, the ventilation stops entirely, and there is no output flow:

Smoke Detector Device for Turning Off Ventilation at 68°C

&DEVC ID='temp_68', XYZ=1.835, 2.345, 2.4, QUANTITY='TEMPERATURE', SETPOINT=68., INITIAL_STATE=.TRUE. /

Supply Vent controlled by smoke detector

&VENT XB=0,0,1.5,2.3,0.2,0.6, SURF_ID='supply', DEVC_ID='temp_68', ID='supply_vent' /
&SURF ID='supply', VOLUME_FLOW=0.625, COLOR='BLACK' /

Then I tried the following:

Supply Vent

&VENT XB=0,0,1.5,2.3,0.2,0.6, SURF_ID='supply_active', DEVC_ID='temp_68' /
&SURF ID='supply_active', VOLUME_FLOW=0.625, COLOR='BLACK' /

Leakage Simulation (Static Vents for Pressure Relief)

&VENT XB=0,0,1.5,2.3,0.2,0.6, SURF_ID='supply_leak', ID='supply_leak_vent' /
&SURF ID='supply_leak', VOLUME_FLOW=0.01, COLOR='GRAY' /

In this case, I am encountering an issue where the second vent is ignored due to overlap in the mesh.

Is there a way to make the fan stop and transition the vent into a "leak" mode without causing this overlap issue? Any help or suggestions would be greatly appreciated.

Thank you!

[drjfloyd]

You could place the leakage vent just to the side of the fan vent. At 0.01 m3/s, a slight "error" in the physical location is unlikely to have a huge impact on results.

Instead of controlling the VENT, you could use a RAMP for the VOLUME_FLOW flow on SURF. Instead of time for the independent RAMP value (T), have it be the logical status of the temperature device. (See the User's Guide for discussions on more complex control behaviors).