Patent ID: 8231837

Claim:
A thermal cracking tube for thermally cracking a hydrocarbon fluid material passing through the tube from one end thereof toward the other end, the tube comprising: an inner surface; and a plurality of rows of projections extending circumferentially along the inner surface of the tube orthogonal to or as inclined with respect to the axis of tube, each of the projection rows including a plurality of projections provided on the tube inner surface, wherein the thermal cracking tube satisfying following conditions: 0.2≦ S/ 10 πD≦ 0.7, 0.02≦ h/D≦ 0.05, and 0.04≦ L/πD ≦0.5, wherein D is the inside diameter in mm of the tube, 10πD is an interior area in mm 2 of the tube having the inside diameter D over a unit longitudinal length of 10 mm, h is the height in mm of projection A arbitrarily chosen from the plurality of projections included in a first projection row α, L is the length in mm of circular arc of the projection A in a direction orthogonal to the tube axis, and S is the area in mm 2 of a region R surrounded by the projection A, lines L 1 and L 2 extending respectively from circumferentially opposite ends of the projection A in parallel to the tube axis, and a second projection row β adjacent to and downstream from the projection row α.