# US 12,111,117 B2 · Double pipe for heat exchanger > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,111,117 B2 - Document ID: US12111117B2 - Status: Granted - Kind: B2 - Application number: 17/757,109 - Filed: 2020-12-08 - Published: 2023-01-05 - Granted: 2024-10-08 - Earliest claimed: 2019-12-13 - Assignees: Uacj Corporation - Applicants: UACJ Corporation - Inventors: Shiro Katahira; Tetsuro Hata; Takuro Nakamura - Web page: https://patentgrep.com/patent/US12111117B2 ## CPC - F28D 7/106: {consisting of two coaxial conduits or modules of two coaxial conduits} - F28F 1/426: {the outside portions and the inside portions forming parts of complementary shape, e.g. concave and convex} - F16L 9/18: Double-walled pipes; Multi-channel pipes or pipe assemblies - F28F 1/06: crimped or corrugated in cross-section - F28F 1/08: Tubular elements crimped or corrugated in longitudinal section - F28F 2210/06: having walls comprising obliquely extending corrugations, e.g. in the form of threads - F28D: HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT (fluid heaters having heat generating means and heat transferring means F24H; furnaces F27; details of heat-exchange apparatus of general) - F28F: DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION (water and air traps, air venting F16) - F16L: PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL ## Abstract A double pipe for a heat exchanger includes an inner pipe disposed in an outer pipe. In a straight-pipe portion of the double pipe, the inner pipe has a plurality of protruding parts extending in a helically offset manner along a longitudinal direction, an inner-circumferential surface of the outer pipe directly contacts the protruding parts, and outer-side channels are partitioned at a plurality of locations in a circumferential direction of the double pipe. The protruding parts are curved to protrude radially outward. In a cross section of the straight-pipe portion orthogonal to the longitudinal direction, the inner-circumferential surface of the outer pipe is circular, and an average value of D/L values of all the outer-side channels is 0.09-0.20, wherein D is defined as a maximum depth of each of the outer-side channels and L is defined as an arc length of each of the outer-side channels in the circumferential direction. ## Claims ### Claim 1 A double pipe for a heat exchanger having a double-pipe structure, in which an inner pipe is disposed in an interior of an outer pipe, to effect heat exchange between a fluid that flows in an interior of the inner pipe and a fluid that flows between the inner pipe and the outer pipe, wherein: in a straight-pipe part of the double pipe, the inner pipe comprises a plurality of protruding parts extending in a longitudinal direction and curved to protrude toward an outer-circumference side and a plurality of helical recessed parts respectively provided between the protruding parts and curved so as to protrude toward an inner-circumference side; the protruding parts are helically offset in the longitudinal direction; the helical recessed parts are helically offset in the longitudinal direction; boundary parts are respectively formed in an angular shape between the protruding parts and the helical recessed parts; in a cross section of the straight-pipe part orthogonal to the longitudinal direction, an inner-circumferential surface of the outer pipe is circular; in the straight-pipe part, the inner-circumferential surface of the outer pipe contacts the protruding parts of the inner pipe, and outer-side channels, which are partitioned at a plurality of locations in a circumferential direction of the double pipe, are formed between the outer pipe and the inner pipe; and in the cross section of the straight-pipe part orthogonal to the longitudinal direction, D is defined as a maximum depth of each of the outer-side channels in millimeters, L is defined as an arc length of each of the outer-side channels in the circumferential direction in millimeters, and an average value of D/L values of all the outer-side channels is greater than 0.09 and less than 0.20. ### Claim 2 (depends on 1) The double pipe according to claim 1, wherein the outer pipe contacts the protruding parts owing to the outer pipe being swaged toward the inner pipe. ### Claim 3 (depends on 1) The double pipe according to claim 1, wherein, in the cross section of the straight-pipe part orthogonal to the longitudinal direction, a total of the arc lengths (L) of the outer-side channels has a length of 60% or more of a circumferential length (C) of a virtual circumscribed circle of the inner pipe. ### Claim 4 (depends on 1) The double pipe according to claim 1, wherein, in the straight-pipe part, the number of the protruding parts provided on the inner pipe is four or more and six or fewer. ### Claim 5 (depends on 1) The double pipe according to claim 1, wherein, in the straight-pipe part, a spiral angle of each of the protruding parts is 20° or more and 60° or less. ### Claim 6 (depends on 1) The double pipe according to claim 1, wherein, in the cross section of the straight-pipe part orthogonal to the longitudinal direction, a total of the arc lengths (L) of the outer-side channels has a length of 90% or less of a circumferential length (C) of a virtual circumscribed circle of the inner pipe. ### Claim 7 (depends on 1) The double pipe according to claim 1, wherein, in the cross section of the straight-pipe part orthogonal to the longitudinal direction, a total of channel cross-sectional areas of the outer-side channels is 5% or more and 30% or less of a channel cross-sectional area of the inner pipe. ### Claim 8 (depends on 2) The double pipe according to claim 2, wherein, in the cross section of the straight-pipe part orthogonal to the longitudinal direction, a total length of the arc lengths (L) of the outer-side channels is 60% or more of circumferential length (C) of a virtual circumscribed circle of the inner pipe. ### Claim 9 (depends on 8) The double pipe according to claim 8, wherein, in the straight-pipe part, four to six of the protruding parts are provided on the inner pipe. ### Claim 10 (depends on 9) The double pipe according to claim 9, wherein, in the straight-pipe part, a spiral angle of each of the protruding parts is 20°-60°. ### Claim 11 (depends on 10) The double pipe according to claim 10, wherein, in the cross section of the straight-pipe part orthogonal to the longitudinal direction, the total length of the arc lengths (L) of the outer-side channels is 90% or less of the circumferential length (C) of the virtual circumscribed circle of the inner pipe. ### Claim 12 (depends on 11) The double pipe according to claim 11, wherein, in the cross section of the straight-pipe part orthogonal to the longitudinal direction, a total of channel cross-sectional areas of the outer-side channels is 5%-30% of a channel cross-sectional area of the inner pipe. ### Claim 13 A double pipe for a heat exchanger, comprising: a double-pipe structure having an inner pipe disposed in an interior of an outer pipe, the double-pipe structure being configured to effect heat exchange between a fluid that flows in an interior of the inner pipe and a fluid that flows in outer-side channels defined between the inner pipe and the outer pipe, wherein: in a straight-pipe portion of the double pipe, the inner pipe comprises a plurality of protruding parts extending in a helically offset manner along a longitudinal direction and a plurality of helical recessed parts respectively provided between the protruding parts, an inner-circumferential surface of the outer pipe directly contacts the protruding parts, and the outer-side channels are partitioned at a plurality of locations in a circumferential direction of the double pipe; the protruding parts are curved to protrude radially outward; the helical recessed parts are curved so as to protrude radially inward; boundary parts are respectively formed in an angular shape between the protruding parts and the helical recessed parts; and in a cross section of the straight-pipe portion orthogonal to the longitudinal direction, the inner-circumferential surface of the outer pipe is circular, and an average value of D/L values of all the outer-side channels is greater than 0.09 and less than 0.20, wherein D is defined as a maximum depth of each of the outer-side channels and L is defined as an arc length of each of the outer-side channels in the circumferential direction. ### Claim 14 (depends on 13) The double pipe according to claim 13, wherein, in the cross section of the straight-pipe portion orthogonal to the longitudinal direction, a total length of the arc lengths (L) of the outer-side channels is 60%-90% of circumferential length (C) of a virtual circumscribed circle of the inner pipe. ### Claim 15 (depends on 14) The double pipe according to claim 14, wherein, in the straight-pipe portion, four to six of the protruding parts are provided on the inner pipe. ### Claim 16 (depends on 15) The double pipe according to claim 15, wherein, in the straight-pipe portion, a spiral angle of each of the protruding parts is 20°-60°. ### Claim 17 (depends on 16) The double pipe according to claim 16, wherein, in the cross section of the straight-pipe portion orthogonal to the longitudinal direction, a total of channel cross-sectional areas of the outer-side channels is 5%-30% of a channel cross-sectional area of the inner pipe.