PURPOSE: To increase heat transfer amount by a method wherein the flow path of the heat transfer tube is provided with a rectangular section or a similar section thereto and the sectional shape of the tube is rotated sequentially in the axial direction to facilitate to disturb the flow in the tube.
CONSTITUTION: The inner surface 1A and the outer surface 1B of the heat transfer tube 1 repeat periodically recess and protuberance in the axial direction Z of the tube and the section of the inner surface of the tube is rectangular shape in any position while the section of the tube is rotated sequentially in the axial direction Z of the tube. The change of a distance (l) between the axial center O and a point D on the inner wall of the pipe in the axial direction Z is smooth and the flow in the tube repeats acceleration and deceleration in the flow direction along the wall of the tube and disturbance in the flow is increased while circumferential and radial flows are induced in the tube, therefore, rotating flow is readily generated. Accordingly, the heat transfer performance may be improved and pressure loss may be reduced.
FUJIE KUNIO
TORII TAKUJI
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