HEAT-EXCHANGER AND U-SHAPED PIPE FOR HEAT-EXCHANGER

PROBLEM TO BE SOLVED: To minimize incurring of the pressure loss of a heating medium flowing through a heat transfer pipe as the improvement effect of heat transfer coefficient by fins is ensured. SOLUTION: A heat-exchanger 1 comprises a number of plate-form fins 6 arranged in parallel with a constant distance therebetween; and a heat transfer tube 3 fixed at the plate-form fins 6 and in a serpentins shape on a whole. The heat transfer tube 3 comprises straight pipes 3B and 3D vertically extending through the plate-form fins 6; and bent pipe parts 3A and 3C to interconnect the ends of the straight pipe parts. Finless parts 2A and 2D having a specified length and other parts 2B and 2F with a fin than the finless parts are formed, in the order, from positions situated upper stream from the straight pipe parts 3B and 3D, and a number of fins 8 are formed in parallel to each other. Further, no fin is formed on the inner wall surfaces of the bent pipe parts 3A and 3C.