HRR decay

[ShehabGamrah]

I would like to ask within FDS as we are capable to specify the ramp up time of a fire using HRR, how can we specify the decay time as in this curve. Also with regards to the temperature boundary condition of a burner surface. It is normally set at 300C by default. Does changing it affect temperature within the simulation.

[drjfloyd]

Please read the User's Guide. It discusses how to define a time dependent heat release rate for a fire.

In terms of temperature the default surface thermal condition in FDS is not 300. Pyrosim may set this temperature, but that is not an FDS default, it is a decision made by Thunderhead Engineering. A thought experiment. If you ran two cases with the surface temperature set to absolute zero (0 K) and 5000 K, would you expect to see any differences?

[ShehabGamrah]

Thanks for your answer. regarding the temperature if I use a high-intensity fires like a 30 MW polyurethane fire, would the burner temperature boundary condition drastically alter the overall temperature results, as the high HRR will quickly dominate the local heat transfer?

[mcgratta]

I doubt it, but you can easily test this.