Strip element dA_1 to plane parallel rectangle
FDiff_2(a, b, c) returns the view factor value from a strip element to a rectangle in a plane that is parallel to it.
Inputs:
a = width of the rectangle [m or ft]
b = length of the rectange [m or ft]
c = parallel spacing distance between the rectangle and the strip element [m or ft]
Example:
"This example determines the view factor between a rectangle of dimensions a x b and a differentially wide strip parallel and below the rectangle. The calculation is done in two ways: 1) by integrating the FDiff_1 for 0<x<b and 2) direct calculation using FDiff_2. The results are identical but the option of integrating allows temperature of other properties to vary with position."
a=1 [m]
b=2 [m]
c=0.5 [m]
F_strip=integral(FDiff_1(a, x, c),x,0,b) "integrate for 0<x<b"
F=FDiff_2(a, b, c)
{Solution: F_strip=F=0.3622}
Reference: Siegel and Howell, Thermal Thermal radiation heat transfer, 4th edition, p.842.