Heat transfer pipe with grooved inner surface
View Patent ↗A heat transfer pipe 21 with grooved inner surface is provided with a pipe body 22 having a pipe axis line ◯ as a center axis line, a plurality of first fins 23 each having a fin height Hf, formed by providing a plurality of spiral grooves 200 at an inner surface of the pipe body 22 along the pipe axis line ◯ and at least a second fin 24 having a fin height hf, provided at a groove bottom of at least one of the spiral groove 200 . The fin height hf and a torsion angle α of the second fin 24 are determined respectively to satisfy the following conditions: Hf /15≦ hf≦Hf /3 and α=β, when P=W×di×sin β and P≧0.86 wherein a bottom width of the spiral groove 200 is W, a torsion angle of the spiral groove 200 is β, and an inner diameter of the pipe body 22 is di.
1. A heat transfer pipe with a grooved inner surface, comprising:
a pipe body having a pipe axis line as a center axis line;
a plurality of first fins, each of the first fins having a fin height Hf;
a plurality of spiral grooves, wherein each of the spiral grooves is provided by adjacent first fins at an inner surface of the pipe body along the pipe axis line; and
a second fin provided at a bottom of at least one of the spiral grooves;
wherein a fin height hf and a torsion angle α of the second fin are determined, respectively, to satisfy the following condition:
Hf/ 15 ≦hf≦Hf/ 3,
α=β
P=W×di × sin β and
P≧ 1.69, mm 2 and
wherein a bottom width of the spiral groove provided by the adjacent first fins is W, a torsion angle of a first fin is β, and an inner diameter of the pipe body is di.
2. The heat transfer pipe with the grooved inner surface according to claim 1 , wherein a number of the second fins is equal to a number of the first fins.
3. The heat transfer pipe with the grooved inner surface according to claim 1 , wherein a number of the second fins is less than a number of the first fins.
4. The heat transfer pipe with the grooved inner surface according to claim 1 , wherein a number of the second fins is more than a number of the first fins.
5. The heat transfer pipe with the grooved inner surface according to claim 1 , wherein an outer diameter do of the pipe body is equal to or more than 7.9 mm, and the torsion angle θ of the first fin is equal to or more than 25°.
6. The heat transfer pipe with the grooved inner surface according to claim 5 , wherein the height Hf of the first fin is 0.18 mm and the height hf of the second fin is 0.03 mm.