To provide a heating tube with grooved inner surface in which heat transfer performance is enhanced by accelerating generation and duration of turbulence.
Inner surface of a tube is sectioned, in the circumferential direction, into a plurality of regions W1-Wn continuous in the longitudinal direction within a specified range. One of adjacent regions W1, W2 is formed with a larger number of parallel fins 10 having a specified twist angle with respect to the tube axis and the other region is formed with a larger number of parallel fins 11 having a specified twist angle in the reverse direction with respect to the tube axis. Fin height is varied gradually along the fin length direction such that the part of minimum fin height Hmin of each fin 10, 11 in the adjacent regions W1, W2 is continuous to the part of maximum fin height Hmax. In the greater part of the boundary section in the longitudinal direction, fins 10, 11 in the adjacent regions have different height.
YAMAMOTO KOJI
NAKAMIZO KENJI
HASHIZUME TOSHIAKI
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