| 摘要 |
PROBLEM TO BE SOLVED: To provide a double tube heat exchanger capable of preventing heat radiating fins from being damaged because of thermal fatigue. SOLUTION: In this double tube heat exchanger (EGR cooler) equipped with an internal pipe, an external pipe and heat radiating fins 16 housed inside the internal pipe, the internal and external pipes are formed into a double tube structure, a V-shaped groove 17a and a reverse V-shaped grooves 17b are formed over the respective apexes of a V-shaped surface 16a and a reverse V-shaped surface 16b along the longer directions of the V-shaped and reverse V-shaped surfaces 16a and 16b. The depth of the grooves 17a and 17b is so set as to be shallow linearly and gradually as they go to the EGR gas outfloe side end part B from the EGR gas inflow side end part A in each heat radiating fin 16. For this reason, the occurrence of cracking in the grooves 17a and 17b thereby permits each heat radiating fin 16 to be deformed because of thermal expansion, so that each heat radiating fin 16 can be prevented from being damaged by thermal fatigue.
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