INTERNALLY GROOVED HEAT EXCHANGER PIPE AND METAL BAR WORKING ROLL FOR INTERNALLY GROOVED HEAT EXCHANGER PIPES

摘要

An internally grooved heat exchanger pipe wherein the inner surface is divided into a plurality of regions (W1, W2) continuous in the direction of the axis of the pipe, (L), and the adjoining regions (W1, W2) are formed with a number of fins (10, 11) that differ in at least one of such factors as the lead angles ( theta , theta ') with respect to the direction of the axis of the pipe, (L), fin top angles ( alpha , alpha ') and fin pitches (p, p'), the boundary line (a) between adjoining regions (W1, W2) being sinuous in the direction of the axis of the pipe, (L). A metal bar working roll wherein a plurality of roll pieces (2a, 2b) having a number of grooves (20, 21) formed in the outer peripheral surface are combined such that they are axially stacked, the contact surface (c) between adjoining roll pieces (2a, 2b) being an inclined surface.