| 摘要 |
PROBLEM TO BE SOLVED: To provide a heat exchanger with high heat exchange efficiency, having a small and inexpensive leakage detection structure. SOLUTION: The heat exchanger 1X has a housed shape wherein a bent tube part formed by winding a triplex tube 1 in consideration of housing into a casing of a water heater or the like. The triplex tube 1 comprises an inner tube 2 passing water through an interior, a middle tube 3 covering an outer circumference of the inner tube 2 and closely contacting the inner tube 2, and an outer tube 4 installed to cover an outer circumference of the middle tube 3 and passing carbon dioxide through an annular part between it and the middle tube 3. By providing fins 5 substantially in parallel with a tube axial direction in only a bending outer side of an inner tube inner wall 2a in the bent tube part, a bending outer side becomes larger than an bending inner side in an inner surface area of the inner tube 2, namely, a heat transfer area of water while suppressing flow resistance increase of the water. Since a flow velocity is faster in the bending side than the bending inner side in the bent tube part, a heat exchange amount is further increased in the bending outer side, and heat exchange amount increase per unit length can be carried out. By using the triplex tube, the leakage detection structure can be provided more inexpensively than applying a grooved tube or the like. COPYRIGHT: (C)2006,JPO&NCIPI
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