| 摘要 |
PROBLEM TO BE SOLVED: To reduce the manufacturing cost by eliminating a joint of double pipes. SOLUTION: In this double pipe type heat exchanger comprising a spiral double heat transfer pipe of the double structure comprising an outer pipe 50 and an inner pipe 48, the individual double heat transfer pipe 53 is formed by combining the inner pipe 48 formed by welding a plurality of short heat transfer pipes 46 of small diameter into a long integrated pipe with the outer pipe 50 formed by welding a plurality of short heat transfer pipes 49 of large diameter into a long integrated pipe into a double pipe structure, and drawing the combined pipes by a die 52.
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