PIPE HAVING GROOVED INNER SURFACE WITH EXCELLENT EXTRUDABILITY

[OBJECT] PROVIDED IS AN OPTIMUM FIN (102) SHAPE WITH BETTER EXTRUDABILITY AND HEAT-TRANSFER EFFICIENCY THAN THOSE OF A CONVENTIONAL ALUMINUM-ALLOY-MADE PIPE HAVING A STRAIGHT GROOVE ON ITS INNER SURFACE. [SOLUTION] DISCLOSED IS A PIPE (100) HAVING A GROOVED INNER SURFACE, THE PIPE INCLUDING AN INNER SURFACE HAVING A PLURALITY OF ELONGATED FINS (102) POSITIONED PARALLEL TO THE LONGITUDINAL DIRECTION OF THE PIPE, WHEREIN SHAPES AND POSITIONS OF THE FINS (102) IN A CROSS SECTION PERPENDICULAR TO THE LONGITUDINAL DIRECTION OF THE PIPE (100) ARE SUBSTANTIALLY UNIFORM IN THE CIRCUMFERENTIAL DIRECTION OF THE PIPE (100); AND A RATIO OF THE LENGTH F (MM) OF AN INNER PERIPHERAL EDGE TO THE AREA A (MM²) OF A GROOVE SPACE IN THE CROSS SECTION IS WITHIN 10 ≤ F/A ≤ 15, THE GROOVE SPACE BEING ENCLOSED BY THE INNER PERIPHERAL EDGE AND A CIRCLE WHICH CONTACTS THE TOPS OF THE FINS (102). [SELECTED