Radiation problem

[harshn]

Hi Everyone,

I am trying to do radiation heating analysis on a slab. I have tried many things but I am getting following erro while writing down Radiation Matrix.

"Error: No element for form factor matrix"

I also pasting the code that I am executing...

/PREP7
/TITLE,
/UNITS,SI
/SHOW,
/View,1,-1,1,1

ET,1,SOLID69

MP,DENS,1,2400

MP,KXX,1,0.8 ! Conductivity in XX W/m K
MP,KYY,1,0.8 ! Conductivity in YY W/m K
MP,KZZ,1,0.8 ! Conductivity in ZZ W/m K
MP,C,1,1046.7 ! Specific heat value, 0.25 Cal/gm = 1.0467 J/gm = 1046.7

J/kg

! Define parameters for model generation

b_h = 48*2.5/100
b_w = 18*2.5/100
f_h = 09*2.5/100
f_w = 144*2.5/100
length = 10
b_off = 27*2.5/100

!

K,1,0,b_h,0
K,2,b_off + b_W + 2*b_off + b_w + b_off,b_h,0
K,3,0,b_h + f_h,0
K,4,b_off + b_W + 2*b_off + b_w + b_off,b_h + f_h,0


K,5,0,b_h,length
K,6,b_off + b_W + 2*b_off + b_w + b_off,b_h,length
K,7,0,b_h + f_h,length
K,8,b_off + b_W + 2*b_off + b_w + b_off,b_h + f_h,length

V,1,2,4,3,5,6,8,7

MSHAPE,0,3D
VMESH,ALL

ET,2,SURF152
MAT,2

NSEL,S,LOC,Y,b_h+f_h
ESEL,ALL
TYPE,2
ESURF

!N,1000,b_off+b_W/2,2*b_h,length/2
!SPACE,1000

FINISH

/AUX12
ESEL,S,TYPE,,2
NSLE,S,ALL,
GEOM,0
EMIS,2,0.92
STEF,5.67E-8

VTYPE,0
WRITE,rmatrix

 

[DonTonino]

There are some corrections to make to your code:

1) the surface element you should use for radiation analysis is SHELL57 (as recommended by the manual), not SURF152. By the manual it seems that SURF152 can be used too, but not as easily in the AIX12 (read the SURF152 manual entry for more details)

2) the space node must be defined as per your current code, it is not (the lines are commented by the '!')

3) once you enter the AIX12, the commands you have listed are all correct aside from the fact that you have NOT reselected the space node (by issuing the NSEL,S,ALL you select all and only the nodes attached to the surface elements)

These corrections done, it should work properly.