| 摘要 |
A heat transfer tube (10) for use in a heat exchanger where heat is transferred between a fluid flowing through the tube and a fluid flowing around the exterior of the tube and where the fluid external to the tube boils during the heat exchange process. The tube has at least one fin convolution (20) extending helically around its external surface (13). A pattern of notches (30) extends at an oblique angle ( alpha ) across the fin convolution at intervals about the circumference of the tube. There is a spike (22) between each pair of adjacent notches. The distal tip (23) is flattened . The maximum width (Wt) of the spike is greater than the width (Wr) of the proximal portion of the fin convolution and is of a width sufficient to overlap with the distal tips of spikes in adjacent fin convolutions, thus forming reentrant cavities between the adjacent fin convolutions and under the overlapping tips. The fin convolution, notches and spikes are formed in the tube by rolling the wall of the tube between a mandrel and, first, a gang of finning disks (63), then second, a notching wheel (66) and, third, a smooth wheel (67). Because, during the manufacture of the tube, of the interaction of the rotating and advancing tube, the notching wheel and the smooth wheel, the angle ( beta ) of inclination of the axis of the tip of the spike is oblique with respect to the notch angle <IMAGE> |
