HEATING TUBE HAVING GROOVED INNER SURFACE

摘要

PROBLEM TO BE SOLVED: To enhance heat exchange efficiency by preventing generation of a boundary layer in the vicinity of the bottom face of a spiral groove thereby preventing thermal insulating action being provided by the boundary layer. SOLUTION: A large number of spiral fins 2 and spiral grooves 4 having a spiral axis matching the axis of a metal pipe 1 are formed alternately on the inner circumferential surface of the metal pipe 1. Furthermore, a plurality of longitudinal fins 6 are formed while dividing the spiral fins 2 to extend in the angular direction of 5 deg. or less with respect to the pipe axis. Longitudinal grooves 8 dividing the longitudinal fins 6 and the spiral fins 2 are formed on the opposite sides of each longitudinal fin 6.