cone calorimeter test (3D, very simplified)

[Βασίλης Καπόγιαννης]

 I want to simulate a cone calorimeter test but first I have to make a much simpler model that runs ( ie: the wood speciment cathes fire from the hot steel above it).

 I believe that I have done something wrong in the code attached ( TEST2.fds) . The simulation runs but it stops at 6.43s and doesn't seem to catch fire. 

     {      WARNING: Minimum density,    0.122 kg/m3, clipped in Mesh 1

             Time Step:    328, Simulation Time:      6.43 s

              ERROR: Numerical Instability - FDS stopped (CHID: TeSt2)                 

      }

What am I missing?

[dr_jfloyd]

You haven't defined any gas phase reactions so there can't be any fire even if the wood pyrolyzed.

You haven't redefined the background species of AIR. So your initial gas will be 77 % AIR plus 23 % oxygen. 

You have a sealed 0.064 m^3 domain that you are removing 0.024 m^3 of gas from.  Look at the pressure in your hrr.csv file.

[Βασίλης Καπόγιαννης]

[Βασίλης Καπόγιαννης]

I made some changes, but it finds an error at the reaction.

[Kevin McGrattan]

There is a table in the back of the FDS User's Guide that lists all the parameters for the REAC line. It appears that you are using parameters that are not on the list.

[Βασίλης Καπόγιαννης]

I made sure that I use the proper parameters but it stil fids an error in the reac line. I also made some more changes that might make (a bit) more sence from a chemical point of view. Is it because I should have made the gases lumped species or is it something else?

[dr_jfloyd]

SOOT_YIELD is only for simple chemistry. If you are explicitly defining the NUs, you cannot use this.

There is no SPEC_ID input in Table 22.27.  

When you get an error message like: 

ERROR: Problem with REAC 1

This means you have an invalid variable in the 1st REAC line in your input file. You should then carefully compare your inputs to the table of inputs for that namelist. Sometimes errors can be hard to catch. A simple method to locate the error is to set T_END=0 so FDS only reads the input and on the line with the problem move the / to half of the inputs.  For example change

&REAC ID='wood_gas_fire',
      FUEL='wood gas',
          SOOT_YIELD=0.01,
          SPEC_ID='wood gas','AIR','PRODUCTS',
          NU=-0.82,-0.9247,1,
          HEAT_OF_COMBUSTION=5700/

to this

&REAC ID='wood_gas_fire',
      FUEL='wood gas',
          SOOT_YIELD=0.01,/
          SPEC_ID='wood gas','AIR','PRODUCTS',
          NU=-0.82,-0.9247,1,
          HEAT_OF_COMBUSTION=5700/

Then run again. If you don't get the message ERROR: Problem with REAC 1, you know the inputs up to the / are good. If you do get the error you know the bad input is somewhere before the /.  Note you may get another error message since moving the / may mean FDS cannot properly process the input, but that would mean FDS at least successfully ready the line. In you case moving the slash as shown an error message other than ERROR: Problem with REAC 1. So you would then move the / to the midpoint of the second half of the input (i.e., after SPEC_ID or NU) and run again. Keep doing this until you figure out the input causing the problem. Yes this may take a couple of minutes, but it will almost certainly be faster than the time it takes to write a post and wait for a a response.

[Βασίλης Καπόγιαννης]

Hi again (after a long long time).

I have made some corections but it seems that there is something that I can't understand with FDS. 

What am I doing wrong?

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

&HEAD CHID='TeSt2',TITLE='tEsT2'/                                        

&MESH IJK=    20    ,    20    ,    20        XB=    -0.20    ,    0.20    ,    -0.20    ,    0.20    ,    -0.20    ,    0.20    /

&TIME T_END=1920/    


&SURF ID='ventilation' , VOLUME_FLOW=0.024    /
&VENT XB=    -0.2    ,    0.2    ,    -0.2    ,    0.2    ,    0.2    ,    0.2        ,SURF_ID='ventilation' , COLOR=    'SKY BLUE'/
&VENT MB= 'XMAX','XMIN','YMAX','YMIN','ZMIN', SURF_ID='OPEN' /

&SURF ID='heat cone'    
      MATL_ID='STAINLESS STEEL'    
      THICKNESS=0.006    
      COLOR='RED'    /
       
&SURF ID='steel'    
      MATL_ID='STAINLESS STEEL'    
      INTERNAL_HEAT_SOURCE=0    
      THICKNESS=0.006    
      COLOR='SILVER'    /
               
&SURF ID='----Speciment-----'    
      MATL_ID= 'WOOD'    
      THICKNESS=0.05    
      COLOR='BROWN'    
      BURN_AWAY = .TRUE. /

&MATL ID='WOOD'
      EMISSIVITY=0.9    
      DENSITY=570.0    
      CONDUCTIVITY=0.2    
      SPECIFIC_HEAT=2.3    
      N_REACTIONS=1    
      A(1)=1.89E+10    
      E(1)=1.51E+05    
      N_S(1)=1.0
      MATL_ID(1,1)='CHAR'    
      NU_MATL(1,1)=0.18    
      SPEC_ID(1:4,1)='OXYGEN','WATER VAPOR','CARBON DIOXIDE','wood_gas',
      NU_SPEC(1:4,1)=0, 0, 0, 0.82    
      HEAT_OF_REACTION(1)=430.0    
      HEAT_OF_COMBUSTION(4,1)=14500.0    /
                               
&MATL ID='STAINLESS STEEL'                
      EMISSIVITY=0.9                
      DENSITY=8000                
      SPECIFIC_HEAT=0.5                
      CONDUCTIVITY=16.2    /            
                   
&MATL ID='CHAR'                
      DENSITY=200                
      CONDUCTIVITY=1                
      SPECIFIC_HEAT=1.6
     
&OBST XB=    -0.175    ,    0.175    ,    -0.175    ,    0.175    ,    0.06    ,    0.08    , INTERNAL_HEAT_SOURCE=  600.0 , HT3D = TRUE , SURF_ID='heat cone'    / Heater
&OBST XB=    -0.05    ,    0.05    ,    -0.05    ,    0.05    ,    -0.07995    ,    -0.03    , SURF_ID= '----Speciment-----'    / Speciment

&SPEC ID='OXYGEN',/1st
&SPEC ID='WATER VAPOR'/2nd
&SPEC ID='CARBON DIOXIDE'/3rd
&SPEC ID='NITROGEN'/4th
&SPEC ID='CARBON MONOXIDE'/5th
&SPEC ID='HYDROGEN'/6th
&SPEC ID='METHANE'/7th

&SPEC ID='AIR' , BACKGROUND=.TRUE. , SPEC_ID(1)='NITROGEN',MASS_FRACTION(1)=0.76374,
                                     SPEC_ID(2)='OXYGEN',MASS_FRACTION(2)=0.23054,
                                     SPEC_ID(3)='WATER VAPOR',MASS_FRACTION(3)=0.00626,
                                     SPEC_ID(4)='CARBON DIOXIDE',MASS_FRACTION(4)=0.00046  / 8th
                                     
&SPEC ID='wood_gas',
      SPEC_ID(1)='NITROGEN',VOLUME_FRACTION(1)=0.509,
      SPEC_ID(2)='CARBON MONOXIDE',VOLUME_FRACTION(2)=0.27,
      SPEC_ID(3)='HYDROGEN',VOLUME_FRACTION(3)=0.14,
      SPEC_ID(4)='CARBON DIOXIDE',VOLUME_FRACTION(4)=0.045,
      SPEC_ID(5)='METHANE',VOLUME_FRACTION(5)=0.03,
      SPEC_ID(6)='OXYGEN',VOLUME_FRACTION(6)=0.006  /9th

&SPEC ID='PRODUCTS',
      SPEC_ID(1)='NITROGEN',VOLUME_FRACTION(1)=0.5248185704,
      SPEC_ID(2)='CARBON DIOXIDE',VOLUME_FRACTION(2)=0.3390426019,
      SPEC_ID(3)='WATER VAPOR',VOLUME_FRACTION(3)=0.1361388272  /10th

&REAC ID='wood_gas_fire',
      FUEL='wood_gas',
      SPEC_ID_NU='wood_gas','AIR','PRODUCTS',
      NU=-0.82,-0.9246985339,1,
      HEAT_OF_COMBUSTION=5700,
      CHECK_ATOM_BALANCE=.FALSE./

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

And the result is

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

 Starting FDS ...

 MPI Process      0 started on DESKTOP-TurboX

 Reading FDS input file ...


ERROR: Problem with REAC 1. Fuel species wood_gas not found. (CHID: TeSt2)

ERROR: FDS was improperly set-up - FDS stopped (CHID: TeSt2)

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

[Jonathan Hodges]

What version of FDS are you using? When I run this case on FDS 6.7.9 the software correctly finds the wood_gas species but errors due to a mass imbalance:

ERROR: Problem with REAC 1. Mass of products,   39.117, does not equal mass of reactants,  57.170

[Kevin McGrattan]

I get this error

ERROR: Problem with REAC 1. Mass of products,   39.117, does not equal mass of reactants,  57.170 (CHID: TeSt2)

which means something is wrong with the reaction stoichiometry.

[Βασίλης Καπόγιαννης]

I have updated to FDS6.7.9 but it still doesn't find the fuel

-------------------------------------------------------------------------------------------------------------------------------

C:\Users\basil\Desktop\διπλωματικη\3>fds TEST2.fds

 Starting FDS ...

 MPI Process      0 started on DESKTOP-TurboX

 Reading FDS input file ...


ERROR: Problem with REAC 1. Fuel species wood_gas not found. (CHID: TeSt2)

ERROR: FDS was improperly set-up - FDS stopped (CHID: TeSt2)

C:\Users\basil\Desktop\διπλωματικη\3>helpfds
FDS revision       : FDS6.7.9-0-gec52dee42-release
MPI library version: Intel(R) MPI Library 2021.6 for Windows* OS

[Kevin McGrattan]

[Βασίλης Καπόγιαννης]

On Tuesday, 15 November 2022 at 16:24:29 UTC+2 Kevin wrote:

[Βασίλης Καπόγιαννης]

It seems to be the same version, but why it doesn't find the fuel?

[Kevin McGrattan]

Forgetting to add a / at the end of a record might cause problems with some operating systems and not with others

[Βασίλης Καπόγιαννης]

Ok, now it gives the error that you mentioned with the stoichiometry.

I made some changes to correct that, and now it finds a problem in the second VENT line that previously was ok

              

                  ERROR: Problem with VENT number 2, line number 10 (MPI Process: 0, CHID: TeSt2)

[Kevin McGrattan]

It might have been previously ignored. This ERROR statement simply means that at least one parameter on the line is not spelled correctly or is not currently valid. Check the VENT table at the end of the FDS User's Guide.

[Βασίλης Καπόγιαννης]

I have managed to make it run without a problem by separating the VENT line to 5 different ones.

In the current model the reaction products are specific.

Is there a way to not specify them in a reaction line (or specify the gases but not the stoichiometry of the reaction)  and afterwards to take readings of the produsced CO2, N2 and water vapors ?

[Βασίλης Καπόγιαννης]

It just finished running. In the hrr file the heat released is constantly 0. If i understand it correctly, the wood speciment hasn't caught fire. What have I done wrong again?

[dr_jfloyd]

The wood has to get hot before it is going to pyrolyze. You have no method of heating up the wood in your input file.

[Βασίλης Καπόγιαννης]

I tried to put INTERNAL_HEAT_SOURCE=100 in the &SURF ID='heat cone' and let it run. 

After 25 hours it finished, but there wasn't any different result.

What would be the corect way to simulate the electric heater?

Could I use EXTERNAL_FLUX in line &SURF ID='----Speciment-----' ,following the example in 11.6.1 of the guide, or is it simplifying too much the problem?

[Kevin McGrattan]

Your input was probably ignored. INTERNAL_HEAT_SOURCE needs to be added to a SURF line that has a THICKNESS and MATL_ID. By itself, it has no meaning.

[Βασίλης Καπόγιαννης]

It was written like this

&SURF ID='heat cone'    
      INTERNAL_HEAT_SOURCE=100

      MATL_ID='STAINLESS STEEL'    
      THICKNESS=0.006    
      COLOR='RED'    / 

[dr_jfloyd]

If you are going to be using a tool like FDS, it is good to get in the habit of assessing what kind of result you expect from your inputs. Simple hand calcs can often indicate if inputs are correct or not.

Your heater OBST is 12.25 cm x 12.25 cm x 0.6 cm. 

100 kW/m3 * 0.000735 m3 = 0.0735 kW

The heat flux from the surface needed to reject this heat at steady-state is

0.0735 kW / 0.245 m2 = 0.3 kW/m2

To get a net heat flux from the surface of 0.3 kW/mw only takes a surface temperature of ~50 C.

[Βασίλης Καπόγιαννης]

The heater OBST is 0.35m x 0.35m x 0.02m so 0.00245m^3

Also where does the 0.000735 volume come from?

[dr_jfloyd]

THICKNESS = 0.006 this defines the thickness for heat transfer not the XB.

[Βασίλης Καπόγιαννης]

Oh my bad. 

They should be the same (6mm). So with the appropriate changes the heater is

&OBST XB=    -0.175    ,    0.175    ,    -0.175    ,    0.175    ,    0.06    ,    0.066     , HT3D = TRUE , SURF_ID='heat cone'    / Heater

If Iunderstand it correctly, to get the equivalent of internal heat source of100kW/m3 , I need 0.1kW/m2 heat flux?

(0.1kW/m2    ~20C room temperature, obviously this amount seems too low for this purpose)

[Βασίλης Καπόγιαννης]

oh, and the HEAT_FLUX=... should be in the &SURF ID='----Speciment-----' line ?

[dr_jfloyd]

For 1D heat transfer, XB and THICKNESS do not have to agree, see Chapter 11 in the User's Guide. OBST XB defines the solid in term of which grid cells and grid cell faces to block for gas and radiation transport. SURF THICKNESS defines the solid for heat transfer. 

Ultimately you are looking to have a hot surface radiate heat to your sample. There are multiple ways you could do this:

- You could set a large enough internal heat source

- You could set a fixed surface temperature

- You could set a fixed surface heat flux

For each approach you would have to determine the correct value of the input to get the desired heat flux at the sample. 

[Βασίλης Καπόγιαννης]

I am trying the fixed temperature method (600 C for start) and I added two temperature sensors, one in the heater and one in the speciment.

I let it run for some time and check the devc file. 

The sensors have a steady ambient temperature of 20 C.

Is the TMP_INNER wrong or does it need something else;

(I have also tried with TMP_FRONT, for longer time, with the same results)

[dr_jfloyd]

Please review the User's Guide section on measuring a solid phase quantity (21.2.2)

[Βασίλης Καπόγιαννης]

So something like this?

&DEVC XB= 0.0 , 0.0 , 0.0 , 0.0 , -0.07995    ,    -0.03
      POINTS= 6
      TIME_HISTORY=.TRUE.
      QUANTITY='TEMPERATURE'
      ID='surface_temperature'/
&DEVC XB=    -0.175    ,    0.175    ,    -0.175    ,    0.175    ,    0.06    ,    0.08     ,
      POINTS=4
      TIME_HISTORY=.TRUE.
      QUANTITY='TEMPERATURE'
      ID='heater_temperature'/

I have added also two slcf lines to see the gas phase temperature. While it seems to warm up, the devc results of the speciment are still 20 C

[Randy McDermott]

Search the user guide for "Solid Phase Quantity at a Single Point".  First, the QUANTITY you want is 'WALL TEMPERATURE', and you also need an IOR.

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[Βασίλης Καπόγιαννης]

Thanks, I initialy though they weren't suitable.

I changed them  to

&OBST XB=    -0.175    ,    0.175    ,    -0.175    ,    0.175    ,    0.06    ,    0.08     , , SURF_ID='heat cone'    /  

&OBST XB=    -0.05    ,    0.05    ,    -0.05    ,    0.05    ,    -0.07995    ,    -0.03    , SURF_ID= '----Speciment-----'    / Speciment

&DEVC XYZ=0,0,0.062
      QUANTITY='WALL TEMPERATURE'
      IOR=-3
      ID='heater_temp'/
&DEVC XYZ= 0.0 , 0.0 , -0.032
      QUANTITY='WALL TEMPERATURE'
      IOR=3
      ID='surf_temp' /

and now I get a more realistic reading.

[Βασίλης Καπόγιαννης]

Is there a way to increase the mesh density (of the whole domain) and the running time won't be huge?

Already at 20x20x20  5mm cubic cells  it takes  24hr.

[Βασίλης Καπόγιαννης]

*2cm cells (not 5mm)

The desired cell dimensions are actually 6x6x6mm

[Βασίλης Καπόγιαννης]

It seems (devc file) that the heater's temperature is continually decreasing. It starts at 600C and after half an hour is close to 190C . How can I make sure that it's temperature remains steady ? 

Also the wood speciment doesn't catch fire. Is it just from the low temperature ( it goes up to 260C) or is it something else? 

[dr_jfloyd]

TMP_INNER does not set a fixed temperature. This is the definition of TMP_INNER from the User's Guide:

11.3.4 Initial and Back Side Temperature

By default, the initial temperature of the solid material is set to ambient (TMPA on the MISC line). Use TMP_INNER on the SURF line to specify a different initial temperature of the solid.

Determine what surface temperature is needed given an A and E for a MATL is something you can determine for yourself.  Run a virtual TGA test for your material (search the User's Guide Table of Contents for TGA) and look to see at what temperature you start seeing a significant mass loss.

[Βασίλης Καπόγιαννης]

 So how do I make it be at 600C constantly?

[dr_jfloyd]

Chapter 11
Fire and Thermal Boundary Conditions

[Βασίλης Καπόγιαννης]

Ok, I run the TGA analysis ( with the heater now at a constant 600C) and the mass starts to decrease rapidly around 300C. 

In the "normal" run the speciment reaches that temperature in 84 seconds and continues rising but with a steady pace as before. 

Shouldn't the rate be higher if it was lit?

[dr_jfloyd]

The only DEVC you have for the solid is the surface temperature.

Is the sample pyrolyzing? 

Is there combustion in the gas phase? If so, what is the HRR over time? Where is the HRR occurring with respect to the sample?

What is the heat flux to the sample? If there is combustion does this increase once there is HRR?

[Βασίλης Καπόγιαννης]

From the hrr file I can see that wood_gas is generated, so the pyrolysis is working, but it doesn't ignite, since all the other gases have 0 MLR. Only the air seems to be reduced at a constant rate wich i think is due to the vent at the ceiling

[dr_jfloyd]

 There isn't a gas phase calculation in the TGA. This just takes the MATL reaction and specific heat and runs a virtual heating test where the sample temperature is forced to increase at TGA_HEATING_RATE.  If you ran a TGA calculation, you won't see an HRR in the hrr file as there is no gas phase calculation.  

If you have looked at the TGA data and it seems to be reasonable in terms of the temperature range over which the wood pyrolyzes, then you need to remove the TGA inputs before running again with TMP_FRONT=600.

[Βασίλης Καπόγιαννης]

This is the fds file I run after the tga analysis and the hrr file to which I refer to

[dr_jfloyd]

Wood is composed primarily of cellulose and lignin in a ratio of around 2:5:1 to 3:1. Both of those compounds of composed of C,H, and O. In wood nitrogen is about 1 % of the mass. This is your wood species:

&SPEC ID='wood_gas',
      SPEC_ID(1)='NITROGEN',VOLUME_FRACTION(1)=0.509,
      SPEC_ID(2)='CARBON MONOXIDE',VOLUME_FRACTION(2)=0.27,
      SPEC_ID(3)='HYDROGEN',VOLUME_FRACTION(3)=0.14,
      SPEC_ID(4)='CARBON DIOXIDE',VOLUME_FRACTION(4)=0.045,
      SPEC_ID(5)='METHANE',VOLUME_FRACTION(5)=0.03,
      SPEC_ID(6)='OXYGEN',VOLUME_FRACTION(6)=0.006  /9th

Over half the mass is a diluent (N2) which is making this mixture more or less non-combustible. Below is your REAC input. You have no soot being produced. You have set CHECK_ATOM_BALANCE=F. If I turn that off your case does not run. Your stoichiometry is unbalanced which means by forcing this reaction to be allowed you are introducing conservation errors:

&REAC ID='wood_gas_fire',
      FUEL='wood_gas',
      SPEC_ID_NU='wood_gas','AIR','PRODUCTS',
      NU=-0.561062447,-0.6326995392,1,
      HEAT_OF_COMBUSTION=5700,
      CHECK_ATOM_BALANCE=.FALSE./

Since your fuel species is composed solely of C,H,O, and N you could just use simple chemistry (see the User's Guide).

What is the heat flux to your sample? You aren't measuring it. Based on that heat flux and the many many papers in the literature on the burning rate of wood in cone calorimeters, what burning rate (kg/m2/s) do you expect to see and how do your results compare.

[Βασίλης Καπόγιαννης]

I had found online that wood gas consists approximately of 50.9% N2, 27% CO, 14% H2, 4.5% CO2, 3% CH4, 0.6% O2 by volume and based on this I tried to make it work in fds.

Can I just omit the species that actually compose the air (N2,CO2,O2) and get a pyrolysis that produces only CHAR, CO, H2, CH4 and WATER VAPOR ?

And then maybe have 4 REAC lines for the combustables?

[Βασίλης Καπόγιαννης]

or am I heading to the wrong direction?

[dr_jfloyd]

If your source was this: https://en.wikipedia.org/wiki/Wood_gas, then this is not what you are modeling. The "wood gas" here is the output of a piece of equipment that decomposes wood in an inerted environment. The high nitrogen levels are the result of the inerted atmosphere and not from the wood.

I suggest you get rid of all the SPEC except for wood_gas. On that SPEC define a FORMULA for wood_gas that is the approximate C_wH_xO_yN_z chemical formula for wood normalized to one carbon atom so you keep the molecular weight down. Then for you REAC input you can just do:

&REAC FUEL='wood_gas',CO_YIELD=x,SOOT_YIELD=y/ where x and y are your desired soot and CO yields.

[Βασίλης Καπόγιαννης]

Thanks, I will try that

[Βασίλης Καπόγιαννης]

I tried that and still no ignition. Have I forgot something or is there a change that Ishould have done?

[dr_jfloyd]

From  Dec 16, 2022, 12:09:40 PM:   " I suggest you get rid of all the SPEC except for wood_gas. "

Dec 16, 2022, 8:06:11 AM: From "What is the heat flux to your sample? You aren't measuring it. Based on that heat flux and the many many papers in the literature on the burning rate of wood in cone calorimeters, what burning rate (kg/m2/s) do you expect to see and how do your results compare."

[Βασίλης Καπόγιαννης]

The heat flux is measured through a BNDF line, wright? Where can I access this number other than smokeview? (Also I suppose I need the top surface averaged heat flux?)

Since the speciment is wood and the fuel is it's pyrolysis product, how can I measure the wood's burning rate ( and not of the wood_gas) ?

[dr_jfloyd]

In Table 21.4 in the User's Guide what file types does it say you can use to output the heat flux?

You have specified a HEAT_OF_COMBUSTION on both the MATL line and the REAC line. What does the User's Guide tell you is the relationship between those two inputs?

[Βασίλης Καπόγιαννης]

->Ok, so heat flux is tracked with 

   &DEVC XB=    -0.05    ,    0.05    ,    -0.05    ,    0.05    ,    -0.03    ,    -0.03
                 QUANTITY='NET HEAT FLUX'
                 IOR=3
                 ID='heat_flux_'/

->In 11.5.1 (pg.100) it says

     "For consistency, the HEAT_OF_COMBUSTION(i,j) can also be specified for each species, i, in each

      reaction, j. These values are used only if the corresponding heats of combustion for the gaseous species
     are greater than zero."

   Does that mean that since I have HEAT_OF_COMBUSTION=12210 in the REAC line it uses the HEAT_OF_COMBUSTION(4,1) in the MATL line?

[dr_jfloyd]

"When the heats of combustion differ, the mass flux of the surrogate FUEL in the gas phase is adjusted so that the correct heat release rate is attained. This is further discussed in the next section."

As an example, i your MATL is H_O_C=50000 but your REAC is H_O_C=25000, the pyrolysis model predicts some actual mass loss from the solid but for that mass loss to get the correct heat release rate, the amount of gas injected needs to be doubled. That is if the pyrolysis model predicted 0.01 kg/s, FDS would adjust that upwards in the gas to 0.02 kg/s (0.01 x 50000 / 25000).  The converse is also true. If you know the production rate of the gas (which is given in the HRR file), you can determine the mass loss rate of the solid.

[Βασίλης Καπόγιαννης]

Thanks. It realy wasn't clear to me that part of the guide

[Βασίλης Καπόγιαννης]

Also, just to be sure, does the image bellow, from the smokeview, depict a flame above the speciment?

[Βασίλης Καπόγιαννης]

?

[dr_jfloyd]

That orange depicts the heat release rate per unit volume shaded per the discussion in the Smokevew Technical Reference where the default value for the hrrpuv cutoff is 200 kW/m3. The orange may or may not represent a visibile flame in reality. You will need to make that judgement based on the actual heat release occuring in that volume.

[Βασίλης Καπόγιαννης]

So I can verify that with a DEVC line where XB=the aproximate volume that the orange appears?

(Sorry for the hiatus)

[Randy McDermott]

Yes, you could add a DEVC.  But this information is already in the _hrr.csv file.

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[Βασίλης Καπόγιαννης]

In the &MATL ID='WOOD' line there is 

      MATL_ID(1,1)='CHAR'
      NU_MATL(1,1)=0.18
      SPEC_ID(1:4,1)='OXYGEN','WATER VAPOR','CARBON DIOXIDE','wood_gas',
      NU_SPEC(1:4,1)=0, 0, 0, 0.82

Why in the hrr.csv file there are zero values to all of the MLRs for the O2,H2O,CO2 and wood_gas ?

[Kevin McGrattan]

The hrr file records the production rate of these gases at the boundary. Do you see anything coming from the boundary?

[Βασίλης Καπόγιαννης]

Oh, it seems I misunderstood that. 

So how do I keep track of the 'wood_gas' that it is produced from the pyrolysis (if there is any) 

and then how can I monitor the results of the REAC line?

[Βασίλης Καπόγιαννης]

is it from the mass.csv ?

[Kevin McGrattan]

Yes, if you request the _mass.csv file using MASS_FILE=T on the DUMP line.