High performance heat transfer tube

A high performance heat transfer tube for use in an evaporator of a refrigeration system is disclosed. The tube has at least one helically extending fin convolution on its external surface and at least one helically extending rib on its internal surface. The fin convolution has bent over tip portions which touch the adjacent convolution to form subsurface passages at those sections of the fin convolution which are not located above an internal rib. Depressed sections of the fin convolution located above an internal rib have bent over tip portions which do not touch the adjacent convolution to form cavities. The subsurface passages and cavities form a subsurface channel having fluid communication with the surroundings of the tube through the cavity openings.