To provide a heat transfer pipe for a flow-down liquid film type evaporator that has a high evaporation performance of the liquid film of a refrigerant and has improved evaporation heat transfer performance.
A heat transfer pipe 1 is provided with a rib 5 that is formed in a projection shape on the inner surface of the pipe and is extended spirally with an appropriate interval, a recessed part 2 that is formed on the outer surface of the pipe and is extended spirally with an appropriate interval, and a plurality of independent projections 6 that are formed on the outer surface of the pipe and are arranged spirally. With the projections 6, the upper surface is recessed so that a part 7 that matches the rib 5 on the inner surface of the pipe is lower than a part 8 that matches the region between ribs. Also, the recessed part 2 on the outer surface of the pipe and the rib 5 on the inner surface of the pipe are formed at mutually matching positions. The projections 6 are in a quadrangular pyramid shape with a height ranging from 0.20 to 0.40 mm and an area ratio A between upper and lower surfaces is 0.25≤A≤0.40. Also, a pitch P of a recessed part 8 on the upper surface of the projections 6 is 5.75≤P≤6.75 mm when viewed from a pipe axis orthogonal section and an angle θ formed by the pipe axis direction of the rib 5 is 40°θ≤44°.
SANYO ELECTRIC CO LTD