Integral of Heat Release Rate

[Katharina Michaelis]

I got the values Qm = 377 MJ/m² as a mobile brand last. And the area is 6700m².

With the information that the integral of the Heat Release Rate is the mobile brand last, I solved

Int (HRR) dx = 377 MJ/m² * 6700 m². 

The time is from 0 till 1800s.

So 1800s * x kW = 2525900 MJ

1800 kWs = 1,8 MJ

So 1,8 MJ * x = 2525900 MJ

x = 1403277,778 which is the heat release rate in kW.

Is that correct?

[dr_jfloyd]

If your assumptions are that the fire is a constant heat release rate and that you have complete burnout in 1800 s, then the result is correct for those assumptions.  6700 m2 is not a small floor plan; in your exprerience do such structures typically achieve complete burnout in 1800 s, and do the fires instantly go from 0 kW to uniform burning over the entire floor area?  

[Katharina Michaelis]

Thank you very much, yes, this are our first assumptions. And is there any way I can calculate a Heat of combustion with that information? Or do I have to take one from a table? 

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[dr_jfloyd]

There are an inifinite combiniation of combustibles you coud stack in one place that would give you 377 MJ/m2, and each combination would have a different HoC. Fuel load does not tell you the HoC. The type of fuels present tells you the HoC.

[Katharina Michaelis]

Thank you - so you mean that it isn't a value you can calculate, but a value specific for a material which only depends on the type of material, but not on the amount of material? Is that correct? 

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[dr_jfloyd]

https://en.wikipedia.org/wiki/Heat_of_combustion

[dr_jfloyd]

For a while now there have been many questions in this forum plus further details in issue opened on the CFAST issue tracker. Combined these have appearance that you are trying to solve some real world fire protection problem without having any background in fire science. If this is not a classroom type problem, but for a real world application, then please keep in mind that any life safety decisions made based on the analysis you are doing will impact the lives and livelihoods of real people. Hopefully, you are working under the supervision of a knowledgeable professional who can correct mistakes.