Patent ID: 7490658

Claim:
An internally grooved heat transfer tube for a high-pressure refrigerant which is used for a cross fin tube type heat exchanger using a high-pressure refrigerant and which is formed of copper or a copper alloy, the heat transfer tube including: a multiplicity of grooves formed in an inner surface thereof so as to extend in a circumferential direction of the tube or extend with a predetermined lead angle with respect to an axis of the tube; and internal fins having a predetermined height and each formed between adjacent two of the multiplicity of grooves, characterized in that: t/D ranges from not smaller than 0.060 to not greater than 0.146 and d 2 /A ranges from not smaller than 0.75 to not greater than 1.5 where an outside diameter of the tube is represented as D(mm), a groove bottom thickness which is a wall thickness of the tube at a portion thereof corresponding to each groove is represented as t (mm), a depth of each groove is represented as d (mm), and a cross sectional area of each groove taken in a cross sectional plane perpendicular to the axis of the tube is represented as A (mm 2 ); and N/Di ranges from not smaller than 8 to not greater than 24 where a number of the multiplicity of grooves is represented as N and a maximum inside diameter of the tube which corresponds to an inside diameter of the tube formed by connecting bottoms of the multiplicity grooves is represented as Di.