Hi Array ,nthank you for your help! I figured out that in Ansys 2019R2 there were only Top na Bottom options in GUI for Perfect enclosure. I've just installed 2020 and saw than in this version, Both option is also available.nnMaybe it will be helpful for somebody: In 2019 I used APDL commands to enforce radiation on both shell faces (for perfect enclosure)ncmsel,s,Selection_Surface1 !Named selection on body named Selection_Surface1nSFE,all,1,RDSF,1,0.6  !Face 1 of SHELL 131, emissivity 0.6nSFE,all,1,RDSF,2,1   !Face 1 of SHELL 131, enclosure 1nSFE,all,2,RDSF,1,0.6  !Face 2 of SHELL 131, emissivity 0.6nSFE,all,2,RDSF,2,1   !Face 2 of SHELL 131, enclosure 1nnsel,allnallselnrsurf