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Author Topic: Setting Radiative Loss Fraction in PyroSim 2015.4.1214  (Read 4307 times)

A Trofimovs

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Setting Radiative Loss Fraction in PyroSim 2015.4.1214
« on: January 05, 2016, 03:41:22 am »

Hi everyone,

I have recently updated the PyroSim to the latest version and have noticed that you cannot any longer set Radiative Loss Fraction parameter in the FDS -> Simulation Parameters.  Is there any way to set up a Radiative Loss Fraction different from the default 0.35 in the newer PyroSim version?


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Re: Setting Radiative Loss Fraction in PyroSim 2015.4.1214
« Reply #1 on: January 05, 2016, 01:33:04 pm »

In FDS 6.3.0 the the RADIATIVE_FRACTION was moved to the REAC line.

In PyroSim, you can specify RADIATIVE_FRACTION on the Byproducts tab of the Edit Reactions dialog (see attached image). Here is the NIST description from the release (

"The default radiative fraction in FDS has been 0.35; that is, the fire is assumed to radiate 35% of its energy. Most users simply accept this value because the literature does not provide an extensive database of these values. Radiative fraction is not an intrinsic property of a fuel; it varies with the size and environment of the fire. However, some fuels, like methane (natural gas), are known to radiate approximately 20%; and some fuels, like heptane and heavier hydrocarbons, radiate approximately 40%. Starting with FDS 6.3.0, certain select fuels like METHANE and HEPTANE will have default values of RADIATIVE_FRACTION other than 35%. METHANE and the alcohols will be 20%; heavier hydrocarbons 40%. Fuels for which we have no traceable reference will remain at 35%. Also, RADIATIVE_FRACTION is now set on the REAC line, not the RADI line. Old input files will be stopped with an ERROR to emphasize the change."