| 摘要 |
PROBLEM TO BE SOLVED: To provide a heating tube having grooved inner surface excellent in evaporation performance and condensation performance. SOLUTION: The heating tube having grooved inner surface is arranged alternately, on the inner surface thereof, with a grooved region 1 having width W1 and a grooved region 2 having width N2 and a linear groove region 3 having width W3 extends in the axial direction of the tube. W1 is set wider than W2. In the grooved regions 1, 2, groove protrusions 4 and groove recesses 5 are formed at same pitch P in the circumferential direction of the tube. A group of grooves is formed spirally in the grooved region 1 at a torsional angleθ1 with respect to the axial direction of the tube whereas a group of grooves is formed reverse spirally in the grooved region 2 at a torsional angleθ2 different from 91 with respect to the axial direction of the tube.
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