Heat transfer tube having grooved inner surface

A heat transfer tube having a grooved inner surface, comprising:

• a metallic tube having a plurality of fins, which are inclined with respect to the axial direction of said metallic tube, formed on an inner circumferential surface thereof;
• wherein the orientation of an inclination angle of said fins with respect to the axial direction is reversed every designated interval in said axial direction and wherein each of said fins has a continuous zigzag shape along a circumferential direction of the inner surface of said metallic tube.

A heat transfer tube having a grooved inner surface, comprising:

• a metallic tube having a plurality of fins, which are inclined with respect to the axial direction of said metallic tube, formed on an inner circumferential surface thereof;
• wherein the orientation of an inclination angle of said fins with respect to the axial direction is reversed every designated interval in said axial direction and wherein each of said fins is divided into a plurality of portions along a circumferential direction on the inner surface of said metallic tube, and fins which are adjacent in a circumferential direction have opposite angles with respect to said axial direction.

A heat transfer tube having a grooved inner surface, comprising:

• a metallic tube having a plurality of fins, which are inclined with respect to the axial direction of said metallic tube, formed on an inner circumferential surface thereof;
• wherein the orientation of an inclination angle of said fins with respect to the axial direction is reversed every designated interval in said axial direction and wherein each of said fins is divided into a plurality of portions along a circumferential direction on the inner surface of said metallic tube, and fins which are adjacent in a circumferential direction have mutually equal angles with respect to said axial direction.