Deprecated: Function create_function() is deprecated in /var/www/wp-content/themes/twentytwenty/functions.php on line 1
Comparison of FED CO Results – FDS Devices & Pathfinder Agents – Jabir Jamal
Categories
Fire Engineering

Comparison of FED CO Results – FDS Devices & Pathfinder Agents

This blog compares the FED CO results generated using FDS devices with results generated using a Pathfinder agent.

FDS Model

Pyrosim Model

A simple FDS model contains a fire source and two openings. Devices are placed at 1.75 m above the floor level near the vertical opening to measure the CO concentration in the air.

Pyrosim Model Details

Geometry

  • Length = 10 m
  • Width = 10 m
  • Height = 3 m
  • Cell size = 0.5 m x 0.5 m x 0.25 m
  • Door opening = 1 m x 1.75 m (vertical opening at mesh boundary)
  • Ceiling opening = 1 m x 1 m (horizontal opening at ceiling level for make up air)

Reaction

  • Polyurethane – C6.3 H7.1 O2.1 N1.0
  • CO yield = 0.05
  • Soot yield = 0.1

Fire Surface

  • HRRPUA = 2000 kW/m²

CO Measuring Devices

  • Quantity – volume fraction
  • Location – XYZ = 0.50, 0.75, Z=1.75

Simulation time

  • Simulation time = 300

Output

  • Plot3D – Carbon Monoxide

Pathfinder Model

Agent characteristics

  • Height = 1.95 m (The measurement location for FED quantity sampling is 90% of occupant height; 1.95 x 0.9 = 1.755 m; FDS device height = 1.75 m)

Pathfinder Models

Pathfinder Model
Pathfinder Model 1
Pathfinder Model 2

Pathfinder Model 1 – The final exit is positioned at approximately 0.25 m away from the edge of the Pyrosim model.

Pyrosim Model 2 – The final exit is at the edge of the Pyrosim model.

Coupling of FDS results with Pathfinder

Pathfinder can use the PLOT3D data output from FDS to couple FDS and Pathfinder. For this exercise, I enabled the PLOT3D option in FDS to measure CO concentration in the air.

Step 1: Import FDS file

Import FDS file to generate rooms

Step 2: Import Smokeview file

Import Smokeview file to couple Pathfinder model with FDS Plot3D results

Importing Smokeview file

Pathfinder Simulation

The Pathfinder model opened the final exit door at time = 300 seconds using a delay feature to measure agent exposure to CO concentration. 300 seconds is the total duration of the FDS simulation. The door is opened at 300 seconds to allow the agent to exit the door.

The approximate location of the agent in Pathfinder models was:

  • Pathfinder model 1: x = 0.46 m, y = 0.74 m
  • Pathfinder model 2: x = 0.22 m, y = 0.74 m

Comparision of FDS Device and Pathfinder Agent Data

Pathfinder Model 1 and FDS Device 1

  • Pathfinder agent location: x = 0.46 m, y = 0.74 m, z = 1.755 m
  • FDS device location: x = 0.5 m, y = 0.75 m, z = 1.75 m

Pathfinder Model 2 and FDS Device 2

  • Pathfinder agent location: x = 0.22 m, y = 0.74 m, z = 1.755 m
  • FDS device location: x = 0.25 m, y = 0.75 m, z = 1.75 m

Conclusion

The results extracted from FDS and Pathfinder are almost identical. The differences in the results may be attributed to the variation in the agent location compared to the FDS device location.

Files

FDS and Pathfinder files are available on my Github page: https://github.com/jabirjamal/jabirjamal.com/tree/main/FE/FED_CO_Pathfinder

References

https://support.thunderheadeng.com/docs/pathfinder/2021-3/user-manual/#_importing_fds_output_data

https://support.thunderheadeng.com/docs/pathfinder/2021-3/technical-reference-manual/