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Author Topic: Setting pool fire and thermal radiation calculation parameters  (Read 5058 times)


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Hello everybody.
May I ask you some kind help to specify an Hexane burning fire.

I specified the proper variables for Hexane under "Reactions".
Then I specified the proper mass burning rate in "Surfaces".

1) Shall Pyrosim take the relevant values (heat of combustion, stoichiometry etc...) from the filled in "Reactions" (where I put values for Hexane)?
2) Shall I have to specify anything in "Particle Injection"?
3) Is that correct that radiation is calculated by means of "thermal elements" and is there any connection with the field "Particle Injection?
4) What is the meaning of "Assumed Radiative Source Temperature" in the "Simulation Parameters"?

I thank you in advance.



Charlie Thornton

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Re: Setting pool fire and thermal radiation calculation parameters
« Reply #1 on: June 28, 2010, 08:36:24 am »

For the most part, I don''t understand enough about FDS to answer your questions.  If you want to go beyond the pre-specified HRR style of fires, you may want to read the following:

FDS Users Guide, 8: Fire and Thermal Boundary Conditions
FDS Users Guide, 11: Combustion and Radiation

Then, to understand how the heat moves around in the model, you may want to read:

FDS Technical Ref, 3: Governing Equations

After you''ve read all that, you''ll be an expert.  As for your questions:

1. By creating a reaction and setting that reaction as the "current reaction" you are setting the REAC record for the input file.  My understanding is that this record controls the gas-phase reaction used throughout the simulation.

2. No.  You can inject three kinds of particles: tracer, water, and fuel.  None of these are required for any particular kind of simulation, except maybe sprinklers which inject their own water particles.  However, you can probably use them to do cool things, like blow fuel across a burner.

3. I don''t know about the thermal elements, but I''m pretty sure "particles" of the sort that you can control via the input file are not required by the radiation calculation.

4. "Assumed Radiative Source Temperature" maps to the FDS input "RADTMP" in the RADI record.  From the FDS Users Guide: "RADTMP is the assumed radiative source temperature. It is used in the computation of the mean scattering and absorption cross sections of water droplets. The default is 900 C."  Ultimately, I don''t know what this means.  I''m guessing that if you are not using water droplets, it does not matter.