To provide a method of easily manufacturing an internally-grooved pipe 1 of high cost performance, for enhancing stirring of fluid flowing inside by providing a lead angle of a spiral groove 2 formed on an inner face with a different angle at an optional part within the pipe total length, and improving cost performance of the internally-grooved pipe 1, in the internally-grooved pipe 1 used as a heat transfer pipe of a heat exchanger and like.
The spiral groove 2 is formed on an optional region of one continuous internally-groove pipe 1 by twisting the region at a prescribed angle by simple processing. Further an angle of the lead angle of the spiral groove 2 is made different from an angle of the lead angle of the other region by adjusting a twisting angle of the twisting processing, thus stirring action of the fluid flowing in the pipe 1 is enhanced, and a function of the internally-grooved pipe 1 is improved.
Hiroki Naito
Daisuke Nagano