SF_7
Function SF_7 provides the shape factor ([m] or [ft]) for conduction between the internal and external surfaces of a square tube.
Inputs:
a = outer edge ([m] or [ft])
b = inner edge ([m] or [ft])
L = length of beam ([m] or [ft])
Example: SF = SF_7(b, a, L)
Reference: Incropera, F. & DeWitt, D. (2002). Fundamentals of heat and mass transfer, 5th ed. Hoboken, New Jersey: John Wiley & Sons. p. 193-194.