U-shaped heat exchanger tube with a concavity formed into its return bend
A heat exchanger tube includes a tube body that forms a hollow passageway and has a U-shaped tube section defining a return bend and a pair of straight tube sections. Respective ones of the straight tube sections are connected to the U-shaped section at respective connection locations and extend generally parallel to one another to define an internal space disposed between and among the U-shaped tube section and the straight tube sections connected to the U-shaped tube section. The U-shaped tube section has a concavity formed thereinto with the concavity defining a portion of the internal space. A heat exchanger serpentine tube includes a plurality of straight tube sections arranged in a plurality of generally parallel rows and disposed in a common plane and a plurality of U-shaped tube sections connected to the plurality of straight tube sections to form a serpentine configuration.
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The present invention relates to a U-shaped heat exchanger tube. More particularly, the present invention is directed to a U-shaped heat exchanger tube with a concavity formed into a return bend of the U-shaped heat exchanger tube.
BACKGROUND OF THE INVENTIONCommonly known in the art in the fabrication of the heat exchangers, straight tubes are bent in an approximate range of bend angles of 170° and 190° so as to form a unitary construction of two straight tube sections integrally connected with a return bend formed at a selected bend angle. A skilled artisan would appreciate that if the straight tube is bent precisely 180°, the two straight tube sections would extend parallel to one another while if the straight tube is bent at a selected bend angle anywhere in the approximate range other than 180°, the straight tube sections would extend generally parallel with one another. For simplicity, the term “generally parallel” shall refer to the relationship of the two straight tube sections after the straight tube is bent at any selected angle in the approximate range of 170° and 190° including the precise bend angle of 180°.
Depending upon the metal material used for the fabrication of the heat exchanger tubes, difficulty may arise. For instance, it is difficult to bend straight stainless steel tubes into U-shaped heat exchanger tubes particularly when a relatively tight return bend is desired. Bending, for example, a straight stainless steel tube to yield a relatively tight return bend often results in wrinkling of the tube perpendicularly to the inner radius IR of the bend 4 as illustrated in
A conventional method for bending tubes for heat exchangers is described in U.S. Pat. No. 5,142,895 to Schuchert.
The pressure die 12 and the clamp die 10 have respective linear tube grooves 30 and 32 that may preferably be elliptically shaped and adapted for receiving the tube 20. Initially, the pressure die 12 and the clamp die 10 are aligned side-by-side with tube grooves 30 and 32 linearly aligned and are spaced from an axis defined by tube groove 18 and the grip section 24. The plastic follower 16 having an arcuate surface generally conforming to the outer diameter of the tube 20 being bent is mounted behind the bend die 8 opposite the pressure die 12. A mandrel rod 34 with the plastic plug mandrel 14 on the end extends forwardly with the bend die 8 and the plastic follower 16 on one side and the pressure die 12 and the clamp die 10 on the opposite side. The drive mechanisms for the bend die 8, the pressure die 12, the clamp die 10, the mandrel rod 34, and the plastic follower 16 are not described in detail because they are conventional and an explanation of them is not necessary for understanding the invention.
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It would be beneficial to provide a heat exchanger tube with a tight return bend, particularly one that is fabricated from a material difficult to bend, that is wrinkle free. It would also be advantageous to provide a heat exchanger tube with a tight return bend that results in a reduced pressure loss of the heat exchange fluid as the heat exchange fluid flows therethrough. The present invention provides such benefits and advantages.
OBJECTS AND SUMMARY OF THE INVENTIONAn object of the present invention is to provide a heat exchanger tube having a U-shaped tube section defining a return bend and a pair of straight tube sections with the U-shaped tube section having a concavity formed thereinto.
It is another object of the invention to provide a heat exchanger tube with a tight return bend that is wrinkle free.
Yet another object to the invention is to provide a heat exchanger tube with a tight return bend with a concavity formed into the tight return bend that results in a reduced pressure loss of the heat exchange fluid as the heat exchange fluid flows therethrough.
It is yet another object of the invention to provide a wrinkle-free heat exchanger tube with a tight return bend and with a concavity formed thereinto that is fabricated from a material difficult to bend.
Accordingly, a heat exchanger tube and a heat exchanger serpentine tube of the present invention are hereinafter described.
According to one exemplary embodiment of the present invention, a heat exchanger tube includes a tube body that forms a hollow passageway and has a U-shaped tube section defining a return bend and a pair of straight tube sections. Respective ones of the straight tube sections are connected to the U-shaped section at respective connection locations and extend generally parallel to one another to define an internal space disposed between and among the U-shaped tube section and the straight tube sections connected to the U-shaped tube section. The U-shaped tube section has a concavity formed thereinto with the concavity defining a portion of the internal space.
According to another exemplary embodiment of the present invention, a heat exchanger serpentine tube includes a plurality of straight tube sections and a plurality of U-shaped tube sections. The plurality of straight tube sections are arranged in a plurality of generally parallel rows and disposed in a common plane. The plurality of U-shaped tube sections are connected to the plurality of straight tube sections in a manner such that a respective one of the U-shaped tube sections defining a return bend connects sequential ones of the plurality of straight tube sections to form a serpentine configuration. Sequential ones of straight tube sections connected to a respective one of the U-shaped sections define an internal space disposed between and among the respective U-shaped tube section and the sequential ones of the straight tube sections. Each one of the U-shaped tube sections has a concavity formed thereinto with the concavity defining a portion of the internal space.
Another exemplary embodiment of the present invention is a heat exchanger that includes an inlet header, an inlet connection connected to the inlet header, an outlet header, an outlet connection connected to the outlet header and a plurality of heat exchanger serpentine tube bodies. The plurality of serpentine tube bodies interconnects the inlet and outlet headers.
These objects and other advantages of the present invention will be better appreciated in view of the detailed description of the exemplary embodiments of the present invention with reference to the accompanying drawing figures.
BRIEF DESCRIPTION OF THE DRAWINGS
Hereinafter, embodiments of the present invention will be described with reference to the attached drawings. The structural components common to those of the prior art and the structural components common to respective embodiments of the present invention will be represented by the same symbols and repeated description thereof will be omitted.
A first exemplary embodiment of a heat exchanger tube 50 of the present invention is hereinafter described with reference to
The straight tube sections 58a and 58b extend generally parallel to one another to define an internal space IS as best shown in
With reference to
As shown in
With reference to
It was expected, due to the smaller U-shaped tube cross-sectional area XAu relative to the straight tube cross-sectional area XAst, that the pressure loss of heat exchanger fluid flowing through the U-shaped tube section 56 would rise. However, an unexpected result occurred. As determined empirically, the pressure loss of the heat exchanger fluid flowing through the U-shaped tube section 56 actually reduced.
A second exemplary embodiment of a heat exchanger serpentine tube 80 of the present invention is illustrated in
Each U-shaped tube section 56 and sequential ones of the straight tube sections 56a, 56b, . . . 56n are integrally connected at respective connection locations as discussed above. Similarly, as discussed above, each concavity 60 extends continuously and radially along each one of the U-shaped tube sections 56 and terminates adjacent the sequential ones of the straight tube sections 56a and 56b, for example, at the respective connection locations.
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One of ordinary skill in the art would appreciate that the heat exchanger tube of the present invention might be constructed using various combinations of the cross-sectional configurations of the U-shaped tube section and the straight tube sections other than the ones discussed above. By way of example only and not by way of limitation, the straight tube sections might be configured as shown in
A sixth exemplary embodiment of the present invention is a method of forming a straight tube into a U-shaped tube. The method provides a cylindrically-shaped bend die 608 shown in
One of ordinary skill in the art would appreciate that the bend die 608, if split along line S-S shown in
In
In view of the above, the heat exchanger tube of the present invention with a U-shaped tube section defining a return bend having a concavity formed thereinto results in a reduced pressure loss of the heat exchange fluid as the heat exchange fluid flows therethrough. Further, the heat exchanger tube of the present invention is wrinkle-free even if the heat exchanger tube includes a tight return bend and the heat exchanger tube is fabricated from a material difficult to bend such as stainless steel. Additionally, the serpentine tube of the present invention can be fabricated without the use of a mandrel rod and a mandrel assembly.
The present invention, may, however, be embodied in various different forms and should not be construed as limited to the exemplary embodiments set forth herein; rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the present invention to those skilled in the art. For instance, as shown in
Claims
1. A tube, comprising:
- a tube body forming a hollow passageway and having a U-shaped tube section defining a return bend and a pair of straight tube sections with respective ones of the straight tube sections connected to the U-shaped section at respective connection locations and extending generally parallel to one another to define an internal space disposed between and among the U-shaped tube section and the straight tube sections connected to the U-shaped tube section, the U-shaped tube section having a concavity formed thereinto with the concavity defining a portion of the internal space.
2. A tube according to claim 1, wherein the concavity extends continuously along the U-shaped tube section and terminates adjacent respective ones of the connection locations.
3. A tube according to claim 2, wherein the concavity has a generally constant depth as the concavity extends continuously along the U-shaped tube section.
4. A tube according to claim 3, wherein the concavity has a generally tapering depth that lessens commencing from the constant depth as the concavity terminates adjacent the respective connection locations.
5. A tube according to claim 1, wherein the U-shaped tube section and the pair of straight tube sections are integrally constructed at the respective connection locations.
6. A tube according to claim 1, wherein respective ones of the straight tube sections as viewed in cross-section have one of circular cross-sections, flattened circular cross-sections, elliptical cross-sections and flattened elliptical cross-sections.
7. A tube according to claim 1, wherein the U-shaped tube section as viewed in cross-section is generally kidney-shaped.
8. A tube according to claim 1, wherein the U-shaped tube section includes a main piece connected to the concavity as viewed in cross-section to define a continuous loop, the concavity forming an apex projecting into the hollow passageway and the main piece having a first imaginary reference point disposed diametric to the apex, a second imaginary reference point and a third imaginary reference point and wherein a first axis as viewed in cross-section extends through the apex and the first imaginary reference point dividing the U-shaped tube section generally symmetrically in half-sections with the apex and the first imaginary reference point being disposed apart from one another at a distance therebetween to define a height and a second axis as viewed in cross-section perpendicularly intersecting the first axis extends through the second imaginary reference point disposed on one of the half-sections and the third imaginary reference point disposed on a remaining one of the half-sections, the second and third imaginary reference points being disposed apart from one another at a widest distance therebetween to define a width.
9. A tube according to claim 8, wherein a ratio of the height to the width is in a range of approximately 0.6 and 0.9.
10. A tube according to claim 1, wherein at least one of the straight tube sections defines in cross-section a straight tube cross-sectional area of the hollow passageway and the U-shaped tube section defines in cross-section a U-shaped tube cross-sectional area of the hollow passageway, the U-shaped tube cross-sectional area being smaller than the straight tube cross-sectional area.
11. A tube according to claim 1, wherein the U-shaped tube cross-sectional area is smaller than the straight tube cross-sectional area by an amount in a range of approximately 10% and 30%.
12. A serpentine tube, comprising:
- a serpentine tube body having a plurality of straight tube sections and a plurality of U-shaped tube sections, the plurality of straight tube sections arranged in a plurality of generally parallel rows and disposed in a common plane, the plurality of U-shaped tube sections connected to the plurality of straight tube sections in a manner such that a respective one of the U-shaped tube sections defining a return bend connects sequential ones of the plurality of straight tube sections to form a serpentine configuration, each of the sequential ones of straight tube sections connected to a respective one of the U-shaped sections defines an internal space disposed between and among the respective U-shaped tube section and the sequential ones of the straight tube sections, each one of the U-shaped tube sections having a concavity formed thereinto with the concavity defining a portion of the internal space.
13. A serpentine tube according to claim 12, wherein each U-shaped tube section and sequential ones of the straight tube sections are connected at respective connection locations.
14. A serpentine tube according to claim 12, wherein the concavity extends continuously along each one of the U-shaped tube sections and terminates adjacent the sequential ones of the straight tube sections at the respective connection locations.
15. A serpentine tube according to claim 12, wherein each concavity has a generally constant depth as the concavity extends continuously along the U-shaped tube section.
16. A serpentine tube according to claim 15, wherein each concavity has a generally tapering depth that lessens commencing from the constant depth as the concavity terminates adjacent the respective connection locations.
17. A serpentine tube according to claim 12, wherein each one of the U-shaped sections as viewed in cross-section is generally kidney-shaped.
18. A serpentine tube according to claim 12, wherein each one of the straight tube sections defines in cross-section a straight tube cross-sectional area and each one of the U-shaped tubes define in cross-section a U-shaped tube cross-sectional area, respective ones of the U-shaped tube cross-sectional areas being smaller than respective ones of the straight tube cross-sectional areas.
19. A serpentine tube according to claim 18, wherein each of the U-shaped tube cross-sectional areas is smaller than each of the straight tube cross-sectional areas by an amount in a range of approximately 10% and 30%.
20. A heat exchanger, comprising:
- an inlet header;
- an inlet connection connected to the inlet header;
- an outlet header;
- an outlet connection connected to the outlet header; and
- a plurality of serpentine tube bodies, each serpentine tube body having a plurality of straight tube sections and a plurality of U-shaped tube sections, the plurality of straight tube sections arranged in a plurality of generally parallel rows and disposed in a common plane, the plurality of U-shaped tube sections connected to the plurality of straight tube sections in a manner such that a respective one of the U-shaped tube sections defining a return bend connects sequential ones of the plurality of straight tube sections to form a serpentine configuration, each of the sequential ones of straight tube sections connected to a respective one of the U-shaped sections defines an internal space disposed between and among the respective U-shaped tube section and the sequential ones of the straight tube sections, each one of the U-shaped tube sections having a concavity formed thereinto with the concavity defining a portion of the internal space, the plurality of serpentine tube bodies interconnecting the inlet and outlet headers.
21. A method of forming a straight tube into a U-shaped tube having a U-shaped section defining a return bend and a pair of straight tube sections with respective ones of the straight tube sections extending generally parallel to one another to define an internal space disposed between and among the U-shaped tube section and the straight tube sections connected to the U-shaped tube section with the U-shaped tube section having a concavity formed thereinto, the concavity defining a portion of the internal space, the method comprising the steps of:
- providing a cylindrically-shaped bend die having a pair of grooves extending into and circumferentially about an outer circumferential surface of the bend die with a protuberance configured as a ring and disposed between the pair of grooves and projecting outwardly relative to the pair of grooves; and
- bending the straight tube about the bend die at a selected angle in an approximate range of 170° and 190° in a manner to form the U-shaped tube having the U-shaped tube section defining the return bend and the pair of straight tube sections with the U-shaped tube section having the concavity formed thereinto with the concavity defining a portion of the internal space.
Type: Application
Filed: Mar 24, 2006
Publication Date: Sep 27, 2007
Applicant:
Inventors: Dennis Martin (East Berlin, PA), Davey Vadder (Westminster, MD)
Application Number: 11/387,786
International Classification: F28D 1/047 (20060101);