Abstract: A method of forming tubing with integral fins oriented parallel to its length, and to a heat exchanger tube produced by such a method. The invention involves extruding a tube so that the tube has at least one internal longitudinal passage, an external surface having a cross-sectional shape in a plane transverse to the extrusion direction, and at least one integral fin parallel to the extrusion direction and extending in a direction away from the external surface of the tube. The tube may be one of a plurality of tubes assembled in parallel to a pair of manifolds, and such tubes are preferably oriented so that their integral fins are substantially parallel, with the fin(s) of a given tube extending toward an adjacent one of the tubes.

Abstract: A refrigeration system that is capable of using carbon dioxide as a refrigerant and makes use of an evaporator that operates as a thermosyphon insensitive to orientation. The refrigeration system includes a condenser adapted to be wrapped around and physically contact a heat sink for conducting heat from a refrigerant within the condenser to the heat sink, a first line connected to the condenser through which the refrigerant is discharged from the condenser after being condensed to a liquid state, an evaporator coupled to the first fluid line and adapted for physical contact with a body so as to draw heat from the body to vaporize the refrigerant within the evaporator, and a second fluid line connected to the evaporator and through which the refrigerant is discharged from the evaporator after being vaporized and then delivered to the condenser. At least the evaporator is formed to have a multiport tube comprising a plurality of parallel passages with hydraulic diameters of less than 0.