Patent ID: 8091615

Claim:
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.