What is the effective area of a tube?

Question

a tube has inner diameter & outer diameter , what would be the effective area of this tube

Answer 1

Sounds like a heat transfer question. If so it depends on how the tube is being used.

For a single pipe exposed to heat transfer to air, the outer diameter is used to determine the surface area. For shell and tube exchangers they have charts for making the determination based on the tube configuration and baffling.

Answer 2

The area is equal to the sum of the outer surface, the inner surface, and twice the base which is ring-shaped.
A cross-section would have an area (pi*Do^2)/4 -(pi*Di^2)/4 =(pi/4)(Do^2-Di^2)
where Do and Di are the outer and inner diameters, repectively.

If you want to know the total surface area of the tube, then we need to know its length.The area of the outer surface will be
piDoL and the inner surface area will be piDiL where L is the length of the tube.

The total surface are is then piL(Di+Do) +pi/2(Do^2-Di^2)