Quote Originally Posted by StAndrew View Post
Looking at the design, I doubt round tubes will ever outperform flat tubes in terms of surface area. However, after looking over this great link/PDF: http://www.wieland-thermalsolutions....ohrewat_08.pdf, I saw some round tubes with fins INSIDE. Im not sure how much this cost, however, this design could certainly rival flat tubes. However again, I dont think this alone will be able to surpass flat tubing to the point of obsolescence.
if you look at the pictures you can see that it is a hybrid of both flat tubes and round tubes.

you can see "normal" finned rad behind the tubes.