HRRPUA and design fire size

[Joshua Klyber]

I am part of an FDS modeling team for Code Unlimited. We are modeling a fire with a polyurethane couch as a fuel source in a fuel limited atrium. We have selected a peak HRR based upon NIST values, however we have been getting a variety of conflicting opinions regarding HRRPUA and design file size.

A selection of the various recommendations:

     A single cell of the mesh

     Limit the HRRPUA to 960 kW/meter squared

     Use the full size of the couch (approximately 14 sq. ft.)

     100 sq. ft. (Pulled from 2008, Jan/Feb issue of NFPA Journal which erroneously cites the number from Principles of Smoke Management as a suggestion, rather than an example)

     A HRRPUA of 220 kW/meter squared for polyurethane foam (from Selecting Design Fires by Staffansson in 2010)

Where do I find a source for appropriate and substantiated values for this model?

Thanks in advance,

Joshua Klyber 

[dr_jfloyd]

Why would your team think having the fuel be emitted by a single grid cell would be at all appropriate for an LES code?   What kind of resolution do you think you would have for either the flame or the plume entrainment if this was done?  This does not suggest a good awareness of how CFD models operate.

Are you comfortable with your determination that the HRR from a single sofa burned by NIST (probably some years ago) is representative of the hazard in your atrium (especially since the atrium will be around for years)?

That being said, how does a sofa burn in the real world?  How could you specify inputs that would at least roughly approximate that behavior?

I was not familiar with your firm, being curious I checked out your webpage:

Using Fire Dynamic Simulator (FDS), a respected CFD program created by the Department of Energy, ....

From the FDS webpage:

FDS and Smokeview are free and open-source software tools provided by the National Institute of Standards and Technology (NIST) of the United States Department of Commerce