1D heat transfert across a symetric material

[omaritani608]

Hello ,

I have a sandwich wall with material A, material B, material A. The material A on one side is exposed to a constant temperature, and material A on the other side is under ambient conditions. I want to measure after a certain time the temperature at the unexposed face of the temperature throughout the solid. How do i define this exactly in FDS? Like should i for example define one symetric surface as follows:

&SURF ID='Material',
COLOR='BLUE',
MATL_ID(1,1)='MATERIAL A,
MATL_ID(2,1)='MATERIAL B',
MATL_ID(3,1)='MATERIAL A',

  MATL_MASS_FRACTION(1,1)=1.0,
  MATL_MASS_FRACTION(2,1)=1.0,
        MATL_MASS_FRACTION(3,1)=1.0,
  THICKNESS(1:3)=0.02,0.003,0.02,
  BACKING='EXPOSED',
  TMP_GAS_FRONT=500
  EXTERNAL_FLUX=20,
  	  STRETCH_FACTOR(1:3)=1

  HEAT_TRANSFER_COEFFICIENT=25
  HEAT_TRANSFER_COEFFICIENT_BACK=5/
  
  and apply this surface to both faces of my obstacle as follows:

&OBST ID='Material_to_test', XB=1.2,1.8,0.4,0.5,1.2,1.8, PERMIT_HOLE=.FALSE. SURF_ID6='ADIABATIC','ADIABATIC','Material','Material','ADIABATIC','ADIABATIC'/
&DEVC ID='UnExposedWallTemp', QUANTITY='WALL TEMPERATURE', SPATIAL_STATISTIC='MEAN', XB=1.2,1.8,0.5,0.5,1.2,1.8, IOR=2/

I guess this will give me a problem with the backing condition forcing me to define two surfaces instead? I also thought that i could just define this material on one face, put the other face as adiabatic, and then measure the temperature for a depth of 0.043 ( approximated to 0.05) using the inside wall temperature as follows, thus giving me the temperature at the other side of the materials:

&OBST ID='Material_to_test', XB=1.2,1.8,0.4,0.5,1.2,1.8, PERMIT_HOLE=.FALSE. SURF_ID6='ADIABATIC','ADIABATIC','Material','ADIABATIC','ADIABATIC','ADIABATIC'/
&DEVC ID='UnExposedWallTemp', QUANTITY='INSIDE WALL TEMPERATURE',DEPTH=0.05, SPATIAL_STATISTIC='MEAN', XB=1.2,1.8,0.5,0.5,1.2,1.8, IOR=-2/

I'm leaning towards the second option but i am not quite sure... Any ideas or guidance is greatly appreciated

[rmcdermo]

See section 8.3.5 Walls with Different Materials Front and Back of the user guide.