| 摘要 |
PROBLEM TO BE SOLVED: To provide a heat exchanger including a first coolant passage and a second coolant passage formed on a long shape main body part, for exchanging heat of a fluid flowing in the first coolant passage and a fluid flowing in the second coolant passage through the main body part, capable of greatly improving heat exchange efficiency as compared with a conventional device. SOLUTION: The heat exchanger includes the first coolant passage 15 of a circular shape in cross section formed in a center of the long shape main body part 11, and a plurality of second coolant passages 17 formed on an outer side of the first coolant passage 15 of the main body part 11, and is characterized by that a center side surface 17b of the second coolant passage 17 is a circular surface around a center O of the first coolant passage 15.
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