Heat transfer pipe

A heat transfer pipe comprising:

• (a) an axially hollow cylindrical heat transfer pipe body and
• (b) a plurality of circumferential fins integrally formed on the outer surface of said cylindrical heat transfer pipe body at a first regular circumferential pitch which leaves a circumferential space between said circumferential fins, each of said circumferential fins having a circumferential axis extending circumferentially around said cylindrical heat transfer pipe body;
• (c) the radially outer portion of each of said circumferential fins having at least one groove extending along the axial length of said circumferential fin to divide the radially outer portion of said circumferential fin into at least two parts separated by said at least one groove,
• (d) each of said circumferential fins also having a plurality of notches therein interrupting the axial length of said circumferential fins and dividing said circumferential fins into a number of parts,
• (e) a plurality of discrete beads being formed on the inner surface of said axially hollow cylindrical heat transfer pipe body along imaginary circumferential lines, said beads being formed at points directly radially underlying at least some of said circumferential fins,
• (f) the depth of said notches in the radial direction being greater than the depth of said at least one groove, whereby condensate on the exterior of said heat transfer pipe does not remain in said grooves but instead flows from said grooves into said notches and from there into the circumferential spaces between said circumferential fins,
• (g) the circumferential spaces between said circumferential fins being wider than the width of said notches, thereby increasing the effective thermal transfer area of the heat transfer pipe, and
• (h) the axial width of said circumferential spaces between said circumferential fins being wider than the width of said grooves, whereby said circumferential spaces are relatively open in the radially outward direction.