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Good evening,

I am simulating a car fire in a parking lot.

Considering the following parameters.

HRR = 4,800 Kw,

For the "Reaction" section, I have considered that polyurethane is being burned.

&REAC ID='POLYURETHANE', FYI='NFPA Babrauskas', FUEL='REAC_FUEL', C=6.3, H=7.1, O=2.1, N=1.0, SOOT_YIELD=0.1, RADIATIVE_FRACTION=0.35/

According to what I have studied, the heat of combustion can be calculated with the spreadsheet Combustion Calculator = https://files.thunderheadeng.com/support/files/Combustion_Calculator_v5-0.zip.

Then by copying the values of the products and by-products of the chemical equation into the spreadsheet Combustion Calculator,
I get a heat of combustion of 19,024 Kj/Kg which can be seen in the attached images.

But the problem is that I understand that the heat of combustion for a burning car must be between 24,000 to 26,000 Kj/Kg.
Does this mean that the polyurethane burner I chose in Pyrosim does not meet the heat of combustion I need?

Can someone provide me the correct chemical equation to produce the amount of heat of combustion as indicated in the standards (between 24 to 26Mj/Kg ?? ).

I hope your comments can help me.

Best regards.

Carlos P.

I would like to invite you to join the new Pathfinder forum. This forum is part of our new help portal, which includes solution articles, options to create support tickets and get help with licensing.

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Eric Benson
Thunderhead Engineering

I would like to invite you to join the new PyroSim forum. This forum is part of our new help portal, which includes solution articles, options to create support tickets and get help with licensing.

View the new PyroSim forum:
https://help.thunderheadeng.com/support/discussions/67000047161

Current posts will not be migrated. However, this forum will stay available as a resource for reference. All posting permissions will be disabled on 24 February.

You may join the new forum here:
https://help.thunderheadeng.com/support/signup

There are a number of benefits to creating a new account. In addition to posting questions, you may also submit bugs and feature requests. If a post requires additional support, you will receive additional help through a support ticket.

We look forward to seeing you at our new forum home:
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Eric Benson
Thunderhead Engineering

Hi Jordan,

Yes with the devices you suggested I found a (small) temperature rise. But I haven't simulated that long.
But it works now! Thanks for your help!

Strange, I was able to get it to work. I have attached an fds script you can try out and see. The two surface temperature devices show the transfer of heat.

Are both sides of the obstruction the same layered material?

untitled.fds
Generated by PyroSim - Version 2022.3.1208
6-Feb-2023 4:17:31 PM

&HEAD CHID='untitled'/
&TIME T_END=1000.0/
&DUMP DT_SL3D=0.25/

&MESH ID='Mesh01', IJK=10,10,10, XB=0.0,2.0,0.0,2.0,0.0,2.0/


&REAC ID='FDS6 PROPANE',
      FYI='FDS6 Predefined',
      FUEL='PROPANE'/

&DEVC ID='Front Surface Temp', QUANTITY='WALL TEMPERATURE', XYZ=1.0,1.0,1.0, IOR=3/
&DEVC ID='Rear Surface Temp', QUANTITY='WALL TEMPERATURE', XYZ=1.0,1.0,0.8, IOR=-3/

&MATL ID='STEEL',
      FYI='Drysdale, Intro to Fire Dynamics - ATF NIST Multi-Floor Validation',
      SPECIFIC_HEAT=0.46,
      CONDUCTIVITY=45.8,
      DENSITY=7850.0,
      EMISSIVITY=0.95/

&SURF ID='Steel',
      RGB=146,202,166,
      MATL_ID(1,1)='STEEL',
      MATL_MASS_FRACTION(1,1)=1.0,
      THICKNESS(1)=0.2/
&SURF ID='Burner',
      COLOR='RED',
      HRRPUA=1000.0,
      TMP_FRONT=300.0/

&OBST ID='Obstruction', XB=0.0,2.0,0.0,2.0,0.8,1.0, SURF_ID='Steel'/

&VENT ID='Mesh Vent: Mesh01 [XMAX]', SURF_ID='OPEN', XB=2.0,2.0,0.0,2.0,0.0,2.0/
&VENT ID='Mesh Vent: Mesh01 [XMIN]', SURF_ID='OPEN', XB=0.0,0.0,0.0,2.0,0.0,2.0/
&VENT ID='Mesh Vent: Mesh01 [YMAX]', SURF_ID='OPEN', XB=0.0,2.0,2.0,2.0,0.0,2.0/
&VENT ID='Mesh Vent: Mesh01 [YMIN]', SURF_ID='OPEN', XB=0.0,2.0,0.0,0.0,0.0,2.0/
&VENT ID='Mesh Vent: Mesh01 [ZMIN]', SURF_ID='OPEN', XB=0.0,2.0,0.0,2.0,0.0,0.0/
&VENT ID='Vent', SURF_ID='Burner', XB=0.0,2.0,0.0,2.0,2.0,2.0/

&SLCF QUANTITY='TEMPERATURE', ID='Slice', PBX=1.0/


&TAIL /

Dear Jordan,

Thanks a lot for your reply!

I have simulated the backwall as exposed, as described in the tutorial.
But this had not change the results. But I wasn't able to set the initial internal temperature the same as in the tutorial, as in the screenshot attached.

The wall is 1 cell in width (the wall is 20 mm, and my grid is 20 x 20 x 20 mm).

Hi,
You must use the EXPOSED backing boundary condition for the layered surface. I believe it must also be 1 or 0 cells thick.
As seen in the attached figure.

Also look at this link, it will describe a little more about conduction in fds.
https://support.thunderheadeng.com/tutorials/pyrosim/heat-conduction/#:~:text=FDS%20assumes%20one%2Ddimensional%20heat,heat%20flows%20through%20the%20obstruction.

I have found there are some quirks when using conduction in FDS. I would consult the user guide for details.

Good afternoon,

My name is Paul Hoondert, and for a dissertation research in Fire Safety Engineering I am modelling facade test setups.

I have modelled a propane burner, where the temperature raises to around 1000 degrees.

The burner is placed in front of a back wall. I see on the temperature slice no temperature rise behind the wall, as shown in the figure.
The wall is modelled as a 20 mm wall of the material steel.

How is it possible that their is no temperature rise behind the wall?

I suppose I have the wrong settings for the wall. I have modelled the wall as layered.

! hope you could help me.

Kind Regards,

Paul Hoondert

Goodmorning guys,
I'm Alberico Guerrieri, I'm a student of Energy engineering.
I'm working with PyroSim for my thesis.

I have an issue and I hope that you could help me !

I'm trying to simulate a fire spread.
I had started from the source:
1) Add reaction -> Simple chemistry model -> I've inserted all the data related to a generic hydrocarbon.
2) Burner surface -> HRR per m^2
Till now everything have worked properly: SV (smokeview) displayed coerently the combustion process.

After I tried to define the other objects that should burn also with a delayed time:
3) Define a new material -> New material  -> Assumption that these objects are rappresented by a liquid fuel (same hydrocarbon of step 1) -> I put all the data related to this liquid, thermal properties and pyrolisis ones.
4) Define a new surface -> New surface -> Layered surface (correct ?) -> Material layers, here I put the material defined in point 3) with a certain thickness (I don't get which dimension I should consider along x,y,z of the 3D object ?)->Reaction, I specified that everything is governed by the material properties and allow obstruction to burn away.

What do you think ?
Is the procedure correct ?

Kind regards,
Alberico Guerrieri
 

Hello,
i defended my PhD on the study of the extinguishing efficiency of sprinklers.  One of the studies was to determine the density of water coverage in a 5x5 meter chamber by placing 100 0.5x0.5x0.01 meter boxes under the sprinkler and measuring the water in them. Can this study be modeled in FDS and specifically measure the water distribution under the sprinkler.