PROBLEM TO BE SOLVED: To provide a triple-tube type heat exchanger securing high heat exchange efficiency while constituting an inner tube and a leakage detecting tube to be multi-lobate tubes with crest portions and trough portions repeatedly arranged in the circumferential direction.;SOLUTION: A triple-tube type heat exchanger (1) includes an inner tube (2) constituted by a multi-lobate tube of which tube wall has a corrugated shape with crest portions (2b) and trough portions (2a) repeatedly arranged in the circumferential direction, a leakage detecting tube (3) constituted by a multi-lobate tube in the almost same shape as the inner tube (2) and externally fitted to the inner tube (2) to be arranged near an outer peripheral surface of the inner tube (2), and an outer tube (4) storing the inner tube (2) and the leakage detecting tube (3) in an inside thereof, and is constituted to enable heat exchange between fluid flowing in an inside (5) of the inner tube (2) and fluid flowing in a gap (6) between the leakage detecting tube (3) and the outer tube (4), and a cross-sectional shape in a section perpendicular to an axial center of the multi-lobate tubes of the inner tube (2) and the leakage detecting tube (3) has straight portions (2c and 3c) connecting crest portions (2b and 3b) and trough portions (2a and 3a), and the inner tube (2) and the leakage detecting tube (3) are in close contact with each other at least in the straight portions (2c and 3c).;COPYRIGHT: (C)2015,JPO&INPIT
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