Differential element or ring on disk 1 to coaxial parallel disk 2
FDiff_8(r_1, r_2, a) provides the view factor from a differential element or ring on disk (1) to a coaxial and parallel disk (2).
Inputs:
r_1 is the radius of the differential ring [m or ft]
r_2 is the radius of the disk [m or ft]
a is the distance between the planes of the differential ring and the disk.[m or ft]
Example:
$UnitSystem SI K Pa J deg
"The following program uses integration to calculate the view factor between two parallel coaxial disks. This view factor could be found more directly using F3D_3, but use of the differential view factor allows the radiation heat transfer to be calculated even if temperature varies with radial position on one of the disks. "
r_1=0.5 [m]
r_2=1 [m]
a=2 [m]
F=FDiff_8(r,r_2,a) "differential view factor"
F_12=integral(F*2*pi*r,r,0,r_1)/(pi*r_1^2) "integration of differential view factor"
F_12`=F3D_3(r_1,r_2,a) "disk to disk view factor relation"
{Solution: F_12 = F_12` = 0.1922}
Reference: Howell, http://www.me.utexas.edu/~howell/sectionb/B-22.html