Modeling of fire suppression by fuel cooling

[pascualsegrellestoni]

Hello everyone,

Recently, a few questions have come up regarding the validity of using FDS for modeling fire suppression via automatic sprinklers.

While consulting relevant literature and the FDS Verification and Validation (V&V) documentation, it remains somewhat ambiguous whether simulating the liquid phase alone (droplet dynamics, transport, and thermal absorption) is sufficient to model suppression accurately, or if empirical parameters ,such as a specified pyrolysis reduction function, are strictly necessary to capture the reduction in Heat Release Rate (HRR).

For instance, publications such as the attached report (VTT Technology 54: Numerical simulations on the performance of water-based fire suppression systems by Jukka Vaari, Simo Hostikka, Topi Sikanen, and Antti Paajanen) indicate that direct physical modeling of the water phase may indeed be viable .

I would welcome any insights, practical experience, or recommendations from the community on this matter.

Best regards,

[drjfloyd]

The E_COEFFICIENT approach simplifies matters by removing the need to have detailed pyrolysis model for the burning object or detailed models of what happens when a drop hits a solid surface. One challenge here is determining what to use for the coefficient. It is not a one-size fits all number, and there is not a lot of available data. A second challenge is developing the inputs to prescribe or predict fire spread over your burning object(s) until the sprinklers operate and start to suppress the fire.

Predicting the decrease in pyrolysis rate by water cooling of a burning material is a more physics based approach. The challenges here are 1) FDS currently has fairly simple models for what happens once a drop hits a solid surface, and 2) being able to define a pyrolysis model or models for your burning object(s) that makes reasonable predictions of the burning rate. At the moment, I feel this would be putting you into more research than practical application.

[pascualsegrellestoni]

Thank you very much, Jason. Based on your comments, testing whether a sprinkler system or sprinkler layout can extinguish a fire using the complex pyrolysis model in FDS is still under development.

I am familiar with the E_COEFFICIENT parameter, but as you mentioned, finding reliable values for these coefficients can be extremely challenging.