Small sphere to a large sphere
Function F3D_22(r_1,r_2,s) returns the view factor between a smaller sphere to a larger sphere.
Inputs:
r_1 = radius of the smaller sphere [m or ft]
r_2 = radius of the larger sphere [m or ft]
s = center-to-center distance between the spheres[m or ft]
Example:
$UnitSystem SI K Pa J deg
r_1=0.1 [m]
r_2=0.2 [m]
s=0.5[m]
F = F3D_22(r_1,r_2,s)
{Solution: F=0.04174}
Note that s must be greater than r_1+r_2.