PURPOSE: To improve heat transfer performance and obtain a heat transfer tube, high in absorbing capacity, by a method wherein the pitch as well as the height of fins are set so that the tip end of at least one fin of neighboring fins and one point on the surface of the heat transfer tube come into contact with a circular arc.
CONSTITUTION: A fin 5 is formed spirally on the surface of a heat transfer tube 4 and an approximate circular arc, contacting with the fin 5 at three points, i.e., the tip end of the fin, the surface of the heat transfer tube 4 and the tip end of the other fin neighboring the fin 5, is described. Liquid film 7 adheres to the fin 5 and the bent part 5a of the same and becomes thinner while the circular arc, described by the liquid film 7, exceeds a semicircle whereby a contacting area between gas and liquid is increased. On the other hand, the reduction of the heat transfer area of the fin is small compared with the fin, on which bending work is not applied. According to this method, the thermal resistance of the liquid film upon heat exchanging is reduced. On the other hand, when there is mass transfer in the liquid film except heat, the rate of penetration of mass diffusion is increased. Further, the tip end of the fin is to come into contact with the circular arc whereby the contacting surface area between gas and liquid is increased without reducing the heat transfer area of the fin.
NISHIGUCHI AKIRA
OUCHI TOMIHISA
SAKAGUCHI HARUICHIRO
HAYASHI MASAKATSU
