Heat-transferring double pipe, inner pipe for heat-transferring double pipe, and manufacturing method thereof
An inner pipe ( 2 ) is designed for a heat-transferring double pipe that exchanges heat between a fluid that flows through the interior of the inner pipe and a fluid that flows between the inner pipe and an outer pipe ( 10 ) that surrounds the inner pipe. The inner pipe has a first region ( 21 ) and a second region ( 22 ), which have transverse cross-sectional shapes that differ. The first region has a plurality of first protruding parts ( 211 ) that protrude outward and form a first recess-protrusion shape in which locations of the first protruding parts are offset helically in a longitudinal direction. The second region has a plurality of second protruding parts ( 221 ) that protrude outward and form a second recess-protrusion shape, in which locations of the second protruding parts are offset helically in the longitudinal direction. The number of second protruding parts is greater than the number of first protruding parts.
1. A heat-transferring double pipe for exchanging heat between a first fluid that flows through the interior of an inner pipe, which has been disposed in the interior of an outer pipe such that the outer pipe surrounds the inner pipe, and a second fluid that flows between the inner pipe and the outer pipe,
wherein:
the inner pipe has a first region and a second region respectively defined in different longitudinal portions of the inner pipe along a longitudinal direction of the inner pipe, which have cross-sectional shapes that differ;
the first region has a plurality of first protruding parts that protrude outward and form a first recess-protrusion shape in which locations of the first protruding parts are offset helically in a longitudinal direction of the inner pipe;
the second region has a plurality of second protruding parts that protrude outward and form a second recess-protrusion shape, in which locations of the second protruding parts are offset helically
in the longitudinal direction;
the number of second protruding parts is greater than the number of first protruding parts;
the heat-transferring double pipe comprises a first portion that is bent, and a second portion having a straight shape;
the first portion at least partially spans the first region; and
the second portion spans the second region.
2. The heat-transferring double pipe according to claim 1 , wherein the inner pipe further has a third region having a cross-sectional shape that is a circular smooth-pipe shape along at least a portion of the inner pipe in the longitudinal direction thereof.
3. The heat-transferring double pipe according to claim 1 , wherein the number of first protruding parts is 2-10.
4. The heat-transferring double pipe according to claim 1 , wherein the number of first protruding parts is half the number of second protruding parts or less.
5. The heat-transferring double pipe according to claim 1 , wherein the cross-sectional shape of the outer pipe is a circular smooth-pipe shape.
6. A method of manufacturing the heat-transferring double pipe according to claim 1 , comprising:
providing an inner-pipe pipe stock having a circular cross-sectional shape;
providing an inner-pipe shaping apparatus, which comprises a plurality of pressing disks disposed spaced apart in a circumferential direction and opposing an outer-circumferential surface of the inner-pipe pipe stock, wherein: the pressing disks each have a disk shape and a pressing surface on an outer circumference of the pressing disk; the pressing disks are rotatable while the inner-pipe pipe stock is moving in an axial direction in a state in which at least one of the pressing surfaces is pressed against the outer-circumferential surface of the inner-pipe pipe stock; and a plane of rotation, which includes the rotational locus of the center location in the width direction of the pressing surfaces, is disposed, viewed from a direction that is parallel to the plane of rotation, in a diagonal direction that is tilted from an axial center line of the inner-pipe pipe stock;
in a state in which the pressing surface of the at least one of the pressing disks is pressed against the outer-circumferential surface of the inner-pipe pipe stock, advancing the inner-pipe pipe stock in the axial direction relative to the pressing disks while causing the at least one of the pressing disks to deform the cross-sectional shape of the inner-pipe pipe stock to form the first recess-protrusion shape; and
thereafter, changing an amount of pressing of the at least one of the pressing disks against the outer-circumferential surface of the inner-pipe pipe stock to form the second recess-protrusion shape while continuing to advance the inner-pipe pipe stock in the axial direction relative to the pressing disks.
7. The heat-transferring double pipe according to claim 2 , wherein the number of first protruding parts is 2-10.
8. The heat-transferring double pipe according to claim 7 , wherein the number of first protruding parts is half the number of second protruding parts or less.
9. The heat-transferring double pipe according to claim 8 , wherein the outer pipe has a circular smooth-pipe shape in transverse cross-section.
10. A heat-transferring double pipe for use in exchanging heat between a first fluid that flows through the interior of an inner pipe and a second fluid that flows between the inner pipe and an outer pipe that surrounds the inner pipe,
wherein:
the inner pipe has a first region and a second region respectively defined along separate sections extending in a longitudinal direction of the inner pipe in parallel to an axial center line of the inner pipe,
the first region has a first transverse cross-sectional shape that differs from a second transverse cross-sectional shape of the second region;
the first region has a first number of first protrusions that protrude radially outward and extend helically relative to the axial center line of the inner pipe and in parallel to each other;
the second region has a second number of second protrusions that protrude radially outward and extend helically relative to the axial center line of the inner pipe and in parallel to each other;
the second number is greater than the first number;
the inner pipe and outer pipe are curved in a first segment that is within the first region of the inner pipe, and
the inner pipe and outer pipe are straight along a second segment that spans the second region of the inner pipe.
11. The heat-transferring double pipe according to claim 10 , wherein:
the first number is between 2-10; and
the first number is half or less of the second number.
12. The heat-transferring double pipe according to claim 11 , wherein the first and second protrusions each extend at a tilt angle of 10°-70° relative to the axial center line of the inner pipe.
13. The heat-transferring double pipe according to claim 12 , wherein the first and second protrusions have the same tilt angle relative to the axial center line of the inner pipe.
14. The heat-transferring double pipe according to claim 13 , wherein the first and second protrusions contact the outer pipe along one or more longitudinal portions of the heat-transferring double pipe.
15. The heat-transferring double pipe according to claim 10 , wherein the first number is between 2-10.
16. The heat-transferring double pipe according to claim 10 , wherein the first number is half or less of the second number.
17. The heat-transferring double pipe according to claim 10 , wherein the first and second protrusions each extend at a tilt angle of 10°-70° relative to the axial center line of the inner pipe.
18. The heat-transferring double pipe according to claim 10 , wherein the first and second protrusions have the same tilt angle relative to the axial center line of the inner pipe.
19. The heat-transferring double pipe according to claim 10 , wherein the first and second protrusions contact the outer pipe along one or more longitudinal portions of the heat-transferring double pipe.
20. The heat-transferring double pipe according to claim 10 , wherein the outer pipe has a circular smooth-pipe shape in transverse cross-section at least along the second segment.