Problem with spatially integrated quantity

[DRAKE JONES]

Dear all, 

             I am trying to find the what is the MASS FRACTION of my Soot yield over a volume by 

&DEVC XB=2.03456,13.7625,2.03475,4.51475,3.7,3.972,SPATIAL_STATISTIC=’VOLUME INTEGRAL', QUANTITY='MASS FRACTION', SPEC_ID='SOOT',ID='MF_SOOT'/

 But I am receiving a warning like this

WARNING: Problem with units compatibility of SPATIAL_STATISITIC VOLUME INTEGRAL with the QUANTITY MASS FRACTION

                But the input file is running. The above warning  means that the device file do not record the mass fraction of the soot over a volume. Then where is the quantity been recorded (instead of the device coordinate( XYZ), a volume is given (please refer to the line above))?.  Basically, I need the total amount of soot produced by my fuel when it burns (due to SOOT_YIELD mentioned on the REAC line). How can the Soot's mass fraction can be recorded over a volume over a period of time?. TIA

[dr_jfloyd]

The warning is just indicating that you doing a volume integral of a quantity that is not per volume and is meant to prompt you to think if you are using the correct quantity. In this case, the units of mass fraction are kg/kg. When you integrate that over volume, you will get (kg m3)/kg. Compare with density where the units are kg/m3 and the integral over volume gives you kg. FDS will still output the DEVC as you specified it. If you want to verify the amount of soot produced by the fire, you could turn on the mass file output. This will output the total mass of all species in the domain. Dividing the soot mass by the mass of fuel burned will give the soot yield. Note if you have any openings or leakage, this will only be correct until you start loosing combustion products through openings or leakage.

[DRAKE JONES]

       I have a model which has glass windows which break at particular temperature. I have a SOOT_YIELD of 0.191 kg/kg for PU foam mentioned in the REAC line. The visibility at the eye level of a person when measured after 10 secs is 0.6 m which is  very very low than what is expected (may be because of the high SOOT_YIELD). Is there any way of determining the visibility at a point over a time manually (just to convince myself that very low visibility is because of the high SOOT-YIELD) ? . I did refer to 21.10.4 of user guide but could not get much. I did rise this query hoping that I could relate soot yield with visibility.

       Is 0.191 kg/kg soot yield is high for furniture made of  Polyurethane foam?. This is the average of all the values of SOOT_YIELD I referred to in the literature. Can lower soot yield value rather than 0.191 kg/kg can cause a change in HRR?