PURPOSE: To enhance heat transfer performance in a tube, to prevent collapse of a groove due to an extension of the tube when fins are mounted on an outside of the tube, and to limit a decrease in the heat transfer performance to a minimum limit by specifying-the shape of the groove of a small-diameter heat transfer tube for a heat exchanger.
CONSTITUTION: In a small-diameter heat transfer tube 1 having 3-6mm of an outer diameter, a groove 3 spiral or continuous in an axial direction is formed on an inner surface of the tube, the depth H of the groove 3 is formed 0.15 < H < 0.25m, the width W1 of the bottom is formed 0.10≤W1≤0.20mm, and a ratio t/D of the thickness (t) of the bottom to the outer diameter D of the tube is formed 0.025≤t/D≤0.075.
HASHIZUME TOSHIAKI
KAWAGUCHI HIROSHI
