The end result of choosing the most advantageous
combination of all factors is the most economical value for A, the
effective tube surface area. This area gives an answer to the
question: “How big a unit must we provide in order to meet our
requirement?”
The effective tube area is that portion within the
shell exposed to the shell side fluid.
It is common practice to figure the area in square
feet using the outside diameter of the tubing instead of an inside or
mean diameter. This is merely for convenience, because the area per
foot of a given O.D. tube is the same for all wall thickness.
