Abstract: 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.

Abstract: Apparatus and method for forming fins on a tube surface. The apparatus comprises a plurality of roller assemblies and each roller assembly includes first and second spaced apart sets of discs. The first set of discs have progressively increasing outside diameters in a forward direction. The second set of discs includes a first subset of discs having outside diameters generally equal to the outside diameter of the forwardmost disc in the first set, and a second subset of discs having progressively increasing outside diameters in the forward direction, with the outside diameter of the forwardmost disc in the second subset generally equal to the outside diameter of the forwardmost disc in the first set.

Abstract: A method of making a new high performance heat transfer tube for use in an evaporator of a refrigeration system is disclosed. According to this novel method, a grooved mandrel is placed inside an unformed tube and a tool arbor having a tool gang thereon is rolled over the external surface of the tube. The unformed tube is pressed against the mandrel to form at least one internal rib on the interior of the tube. Simultaneously, at least one external fin convolution is formed on the exterior of the tube. The external fin convolution has depressed sections above the internal rib where the tube is forced into the grooves of the mandrel to form the rib. A smooth roller-like disc on the tool arbor is rolled over the external surface of the tube after the initial formation of the external fin and internal rib. The resulting heat transfer tube has an exterior with a subsurface channel consisting of interconnected cavities and subsurface passages.