WO2007126504A1

WO2007126504A1 - Heat exchanger tube with a compressed return bend, a serpentine heat exchanger tube with compressed return bends and heat exchanger implementing the same

Info

Publication number: WO2007126504A1
Application number: PCT/US2007/004914
Authority: WO
Inventors: Thomas William Bugler; George Robert Shriver; Richard Preston Merrill
Original assignee: Evapco, Inc.
Priority date: 2006-03-31
Filing date: 2007-02-28
Publication date: 2007-11-08
Also published as: US20070227713A1

Abstract

A heat exchanger tube includes a tube body forming a hollow passageway and having a U-shaped tube section defining a return bend, a pair of straight tube sections and a pair of transition sections. Respective ones of the straight tube sections are connected to the return section with respective ones of the transition sections disposed therebetween. The straight tube sections extend generally parallel to one another. Each straight tube section has a straight tube cross-sectional width and the return bend has a return bend cross-sectional width that is smaller than the straight tube cross-sectional width. Multiple heat exchanger tubes can be connected together to form a serpentine heat exchanger tube. Multiple serpentine heat exchanger tubes or multiple heat exchanger tubes can be assembled together to form a heat exchanger apparatus.

Description

HEAT EXCHANGER TUBE WITH A COMPRESSED RETURN BEND, A

SERPENTINE HEAT EXCHANGER TUBE WITH COMPRESSED RETURN BENDS

AND HEAT EXCHANGER IMPLEMENTING THE SAME

FIELD OF THE INVENTION _Λ

[0001] The present invention relates to heat exchanger tubes. More particularly, the present invention is directed to a heat exchanger tube with a compressed return bend, a serpentine heat exchanger tube with compressed return bends and a heat exchanger fabricated from heat exchanger tubes with compressed return bends.

BACKGROUND OF THE INVENTION

[0002] In the past, manufacturers in the heat exchanger industry have been known to densely pack heat exchanger tubes in heat exchangers in order to achieve greater heat exchange efficiency while simultaneously maintaining or reducing the size of the heat exchanger. For example, in Figures 1-3B, depressions 100 in a form of indentations, hollows, grooves, notches or dimples are formed in designated depression areas DA in the return bends 102a of the heat exchanger tubes 102. This particular densely-packed heat exchanger tube arrangement is more specifically described in U.S. Patent No. 6,820,685.

[0003] In Figures 3A and 3B, four heat exchanger tubes 102 constitute a portion of a heat exchanger. These four heat exchanger tubes 102 are stacked in a staggered planar arrangement and the adjacent return bends 102a overlap one another by an amount of overlap OL shown in Figure 3B. As best shown in Figure 3B and with reference to Figure 2, a cross-sectional circular part of one return bend 102a nests in the depression 100 of the adjacent return bend 102a to achieve the overlapping effect. By virtue of this overlapping effect, a heat exchanger assembled with heat exchanger tubes 102 having return bends 102a with depressions 100 formed thereinto can be considered a densely packed heat exchanger. [0004] However, there are drawbacks for a densely packed heat exchanger that uses return bends with depressions formed therein. First, as shown in Figure 2, the depression results in a protuberance 104 that projects into the hollow passageway of the heat exchanger tube 102. Such protuberances, particularly in consideration of the numerous heat exchanger tubes that constitute a heat exchanger, can interfere with the heat exchanger fluid flowing therethrough. At a minimum, the protuberance 104 partially obstructs the flow of the heat exchanger fluid through the return bend and, at the apex of the protuberance 104, the cross-sectional area CSA of the hollow passage way is significantly reduced as shown in Figure 2. Precision is required to accurately form the depressions repeatedly at the same depression area to numerous heat exchanger tubes. Also, precision in assembly is required in order to properly arrange the heat exchanger tubes so that the cross-sectional circular parts of the return bend nests within the depressions. Without the cross-sectional circular parts nesting properly within the depressions, a densely packed heat exchanger becomes larger in size than originally planned.

[0005] It would be beneficial to provide heat exchanger tubes with return bends that do not include depressions yet can be assembled to form a densely packed heat exchanger. It would also be beneficial to provide heat exchanger tubes with return bends that do not include depressions yet can be assembled to form a densely packed heat exchanger without consideration of precision assembly. The present invention provides these benefits.

OBJECTS AND SUMMARY OF THE INVENTION

[0006] It is an object of the invention to provide a heat exchanger tube with a return bend that does not include any depressions and can be assembled with similar heat exchanger tubes to form a densely packed heat exchanger.

[0007] It is another object of the invention to provide heat exchanger tubes with return bends that do not include any depressions and can be assembled together to form a densely packed heat exchanger without any consideration to precisely arranging the heat exchanger tubes relative to one another.

[0008] It is yet another object of the invention to provide a densely packed heat exchanger using heat exchanger tubes that, upon assembly into the densely packed heat exchanger, do not overlap one another.

[0009] A still further object of the invention is to provide a heat exchanger tube with a return bend that can be assembled into a densely packed heat exchanger without significantly reducing the cross-sectional area of the hollow passageway of the return bend. [0010] Accordingly, a heat exchanger tube of the first embodiment of the present invention, a serpentine heat exchanger tube of the second embodiment of the present invention and a heat exchanger apparatus of the third embodiment of the present invention are hereinafter described.

[0011] The heat exchanger tube of one exemplary embodiment of the present invention includes a tube body forming a hollow passageway and having a U-shaped tube section defining a return bend, a pair of straight tube sections and a pair of transition sections. Respective ones of the straight tube sections are connected to the return section with respective ones of the transition sections disposed therebetween. The straight tube sections extend generally parallel to one another. Each straight tube section has a straight tube cross-sectional width and the return bend has a return bend cross-sectional width that is smaller than the straight tube cross-sectional width.

[0012] The serpentine heat exchanger tube of another exemplary embodiment of the present invention includes a serpentine tube body disposed in plane, forming a hollow passageway and having a plurality of straight tube sections arranged generally parallel with one another, a plurality of return bends and a plurality of transition sections. A respective one of the plurality of transition sections interconnects respective ones of the plurality of straight tube sections and the return bends to form a serpentine configuration. Each straight tube section has a generally uniform straight tube section cross-sectional configuration and a straight tube cross- sectional width and each return bend has a generally uniform return bend cross- sectional configuration and a return bend cross-sectional width that is smaller than the straight tube cross-sectional width.

[0013] The heat exchanger apparatus of yet another exemplary embodiment of the present invention 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 serpentine tube bodies. Each serpentine tube body is disposed in a respective plane, forms a hollow passageway and has a plurality of straight tube sections arranged generally parallel with one another, a plurality of return bends and a plurality of transition sections. A respective one of the plurality of transition sections interconnects respective ones the plurality of straight tube sections and the return bends to form a serpentine configuration. Each straight tube section has a generally uniform straight tube section cross-sectional configuration and a straight tube cross-sectional width. Each return bend has a generally uniform return bend cross-sectional configuration and a return bend cross-sectional width that is smaller than the straight tube cross-sectional width.

[0014] 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 drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a perspective view of a conventional heat exchanger tube that has depressions formed into its return bend.

[0016] Figure 2 is a cross-sectional view along one depression_of the conventional heat exchanger tube in Figure 1.

[0017] Figure 3 A is a partial perspective view of a conventional heat exchanger apparatus.

[0018] Figure 3B is a cross-sectional view of the conventional heat exchanger apparatus taken along lines 3B-3B-3B in Figure 3A.

[0019] Figure 4 is a perspective view of a heat exchanger tube of a first exemplary embodiment of the present invention.

[0020] Figure 5 is a side elevational view of the heat exchanger tube in Figure 4.

[0021] Figure 6 is a top planar view of the heat exchanger tube in Figure 4.

[0022] Figure 7 is a front elevational view of the heat exchanger tube in Figure 4.

[0023] Figure 8 is a cross sectional view of the heat exchanger tube taken along line that 8-8 in Figure 5.

[0024] Figure 9 is a cross sectional view of the heat exchanger tube taken along line that 9-9 in Figure 5.

[0025] Figure 10 is a perspective view of a conventional heat exchanger tube having a continuous circular cross-section.

[0026] Figure 11 is a cross sectional view of the conventional heat exchanger tube taken along line 11-11 in Figure 10.

[0027] Figure 12 is a cross sectional view of the conventional heat exchanger tube taken along line 12-12 in Figure 10. [0028] Figure 13 is a perspective view of the conventional heat exchanger tube in

Figure 10 disposed between a pair of pressing members.

[0029] Figure 14 is a front elevational view of the conventional heat exchanger tube and pressing members shown in Figure 13 with forces F1 and F2 being applied to the pressing members.

[0030] Figure 15 is a top planar view of the conventional heat exchanger tube and pressing members shown in Figure 13 with forces F1 and F2 being applied to the pressing members.

[0031 ] Figure 16 is a top planar view of the heat exchanger tube of the first embodiment of the present invention as shown in Figure 4 after its return bend has been compressed by the forces F1 and F2.

[0032] Figure 17 is an alternative cross sectional configuration in a form of an oval with a pair of opposing flat side walls of either the return bend or the straight tube sections of the heat exchanger tube of the first embodiment of the present invention.

[0033] Figure 18 is an alternative cross sectional configuration in a form of an oval of either the return bend or the straight tube sections of the heat exchanger tube of the first embodiment of the present invention.

[0034] Figure 19 is an alternative cross sectional configuration in a form of an ellipse of either the return bend or the straight tube sections of the heat exchanger tube of the first embodiment of the present invention.

[0035] Figure 20 is a perspective view of a serpentine tube of a second embodiment of the present invention.

[0036] Figure 21 is a perspective view of a heat exchanger apparatus of a third embodiment of the present invention.

[0037] Figure 22 is a partial perspective view of the heat exchanger apparatus in

Figure 21.

[0038] Figure 23 is a cross-sectional view of the heat exchanger apparatus taken along lines 23-23 in Figure 22.

[0039] Figure 24 is a cross-sectional view of the heat exchanger apparatus taken along lines 24-24 in Figure 22. perspective view of a heat exchanger tube of a first exemplary embodiment of the present invention. [0040] Figure 25 is a side elevational view of two crossing, staggered, juxtaposed return bends of the heat exchanger tube in Figure 21 contacting one another at location X.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0041] 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.

[0042] A first exemplary embodiment of a heat exchanger tube 10 of the present invention is hereinafter described with reference to Figures 4-9. As best shown in Figures 4-7, the heat exchanger tube 10, hereinafter referred to as tube 10, of the present invention includes a tube body 12. One of ordinary skill in the art would appreciate that the tube 10 might be used in other applications other than in heat exchanger apparatuses. The tube body 12 forms a hollow passageway 14 and has a U-shaped tube section defining a return bend 16, a pair of straight tube sections 18 and a pair of transition sections 20. Respective ones of the straight tube sections 18 are connected to the return bend 16 section with respective ones of the transition sections 20 disposed therebetween. The straight tube sections 18 extend generally parallel to one another at shown in Figure 5. The term "generally parallel" means that the opposing straight tube sections 18, 18, relative to the return bend 16, might perfectly parallel one another, might taper slightly towards each other or might diverge slightly away from each other as is commonly known in the heat exchanger industry.

[0043] As shown in Figure 8, each straight tube section 18 has a straight tube cross-sectional width Wsts and, at shown in Figure 9, the return bend 16 has a return bend cross-sectional width Wrb. The return bend cross-sectional width Wrb is smaller than the straight tube cross-sectional width Wsts. Preferably, a width ratio of the straight tube cross-sectional width Wsts to the return bend cross-sectional width Wrb is in a range of approximately 1.2 and 1.3. However, it is theorized by the inventors that the width ratio of the straight tube cross-sectional width Wsts to the return bend cross-sectional width Wrb might be in a range of approximately 1.1 and 1.6. With reference to Figure 8, each straight tube section has a straight tube cross- sectional height Hsts and, with reference to Figure 9, the return bend has a return bend cross-sectional height Hrb. The return bend cross-sectional height Hrb, as reflected in Figure 9, is larger than the straight tube cross-sectional height Hsts. However, one of ordinary skill in the art would appreciate that there are conventional tube bending techniques capable of controlling the return bend cross-sectional height Hrb. Therefore, it is possible that the return bend cross-sectional height Hrb might be equal to or even smaller than the straight tube cross-sectional height Hsts. [0044] As shown in Figures 4-8, the straight tube sections 18, 18 have a generally uniform straight tube section cross-sectional configuration. As the shown in Figures 4, 7 and 8, the straight tube section cross-sectional configuration is circularly-shaped. As shown in Figures 4-7 and 9, the return bend 16 is a generally uniform in its return bend cross-sectiona! configuration at least substantially along its entirety and is absent of any depressions. For this embodiment, the return bend cross-sectional configuration is generally elliptically-shaped as best shown in Figure 9. Note that the return bend 16 includes opposing parallel sidewalls 22.

[0045] In Figure 7, each straight tube section 18 has a straight tube cross-sectional area CAsts. The straight tube cross-sectional area CAsts of the straight tube sections 18, 18 are at least substantially equal relative to each other. In Figure 9, the return bend 16 has a return bend cross-sectional area CArb. With reference to Figures 8 and 9, the return bend cross-sectional area CArb and the straight tube cross-sectional area CAsts are at least substantially equal to each other. By way of example only and not by way of limitation, it was empirically determined that the return bend cross-sectional area CArb was approximately 3¹/2% smaller that the straight tube cross-sectional area CAst when using a one-inch tube having a 1.05- inch outer diameter that was formed into a generally elliptical ly-shaped cross- sectional return bend having a 1%-inch height and a 0.85-inch width. [0046] By way of example only and not by way of limitation, a method for fabricating the tube 10 of the present invention is described with reference to Figures 10-16. A tube 10a in figure 10 has a constant circular cross-sectional configuration both along the straight tube sections 18a, 18a and along the return bend 16a as shown in Figures 11 and 12. In Figures 13-15, return bend 16a of the tube 10a is placed between a pair of pressing members 24. Forces F1 and F2 of approximately equal magnitude are applied to respective ones on the pressing members 24. The magnitude of the forces F1 and F2 are sufficient to compress the return bend 16a to form the tube 10 of the present invention described above. Since a circular tube is merely compressed at its return bend, a skilled artisans would appreciate that the return bend cross-sectional area CArb and the straight tube cross-sectional areas CAsts are at least substantially equal to each other. Also, it would be appreciated that since a single bent tube is compressed at the return bend 16, then the straight tube cross-sectional areas CAsts are at least substantially equal to each other. [0047] Compressing the return bend 16a to form the tube 10 of the present invention forms the transition sections 20. As best shown in Figures 5 and 6, each transition section includes an opposing pair of first walls 26 tapering inwardly from the straight tube section 18 towards the return bend 16 (Figure 6) and an opposing pair of second walls 28 tapering inwardly from the return bend 16 towards the straight tube section 18. Individual ones of the opposing pairs of first and second walls 26 and 28 respectively are integrally connected in an alternating manner as shown in Figures 5-7.

[0048] A skilled artisan would comprehend that the tube 10 of the present invention might have other cross-sectional configurations of the straight tube sections and the return bend. By way of example only and not by way of limitation, the return bend cross-sectional configuration and/or the straight tube sections cross- sectional configurations can be generally oval-shaped as shown Figure 17 with opposing parallel sidewalls 22a, oval-shaped as shown in Figure 18 or elliptically- shaped as shown in Figure 19 although other cross-sectional configurations might be used.

[0049] A serpentine tube 210 of a second exemplary embodiment of the present invention is illustrated in Figure 20. The serpentine tube 210 includes a serpentine tube body 212 disposed in plane P and forms the hollow passageway 14. The serpentine tube body 212 has a plurality of straight tube sections 18 arranged generally parallel with one another, a plurality of return bends 16 in a compressed form and a plurality of transition sections 20. A respective one of the plurality of transition sections 20 interconnects respective ones of the plurality of straight tube sections 18 and the return bends 16 to form a serpentine configuration in Figure 20. Each straight tube section 18 has a generally uniform straight tube section cross- sectional configuration and a straight tube cross-sectional width as discussed above. Each return bend 16 has a generally uniform return bend cross-sectional configuration and a return bend cross-sectional width as discussed above. The return bend cross-sectional width is smaller than the straight tube cross-sectional width as discussed above. Also, as discussed above, each straight tube section 18 has a straight tube cross-sectional height and each return bend 16 has a return bend cross-sectional height that is larger than the straight tube cross-sectional height. [0050] A heat exchanger apparatus 310 of a third exemplary embodiment of the present invention is illustrated in Figures 21-25. In Figure 21 , the heat exchanger apparatus 310 includes an inlet header 312, an inlet connection 314 connected to the inlet header 312, an outlet header 316, an outlet connection 318 connected to the outlet header 316 and a plurality of adjacent serpentine tube bodies 212, the details of which being discussed above. Respective ones of the plurality of adjacent serpentine tube bodies 212 are connected to and between and in fluid communication with the inlet header 312 and the outlet header 316. As best shown in Figures 21-25, the plurality of adjacent serpentine tube bodies 212 are staggered in an alternating fashion with each serpentine tube body 212 being disposed in a selected one. of a plurality of parallel planes P1 through Pn (Figure 21) in a juxtaposed manner. Staggered juxtaposed ones of the return bends 16 as illustrated in Figures 23 and 25 contact one another at a location X in Figure 25 where the staggered juxtaposed ones of the return bends 16 cross one another. [0051] According to the present invention, the heat exchanger tube includes a compressed return bend without any depressions. A plurality of such heat exchanger tubes can be assembled to form a densely packed heat exchanger without consideration to precisely arranging the heat exchanger tubes relative to one another. Without depressions, the compressed return bends do not overlap one another as in the prior art. Further, a heat exchanger tube with a compressed return bend and without depressions does not substantially reduce the cross-sectional area of the hollow passageway of the return bend as does those heat exchanger tubes with depressions.

[0052] 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.

Claims

What is claimed is:

1. A tube, comprising: a tube body forming a hollow passageway and having a U-shaped tube section defining a return bend, a pair of straight tube sections and a pair of transition sections, respective ones of the straight tube sections connected to the return bend with respective ones of the transition sections disposed therebetween, the straight tube sections extending generally parallel to one another, each straight tube section having a straight tube cross-sectional width, the return bend having a return bend cross-sectional width being smaller than the straight tube cross-sectional width.

2. A tube according to claim 1 , wherein a width ratio of the straight tube cross-sectional width to the return bend cross-sectional width is in a range of approximately 1.2 and 1.3.

3. A tube according to claim 1 , wherein a width ratio of the straight tube cross-sectional width to the return bend cross-sectional width is in a range of approximately 1.1 and 1.6.

4. A tube according to claim 1 , wherein the straight tube sections have a generally uniform straight tube section cross-sectional configuration.

5. A tube according to claim 4, wherein the straight tube section cross- sectional configuration is circularly-shaped or elliptically-shaped.

6. A tube according to claim 1 , wherein at least a substantial entirety of the return bend has a generally uniform return bend cross-sectional configuration.

7. A tube according to claim 6, wherein the return bend cross-sectional configuration is generally one of oval-shaped with opposing parallel sidewalls, oval- shaped, elliptically-shaped and elliptically-shaped with opposing parallel sidewalls.

8. A tube according to claim 1 , wherein each transition section includes an opposing pair of first walls tapering inwardly from the straight tube section towards the return bend and an opposing pair of second walls tapering inwardly from the return bend towards the straight tube section, individual ones of the opposing pairs of first and second walls integrally connected in an alternating manner.

9. A tube according to claim 1 , wherein the return bend has a return bend cross-sectional area and each straight tube section has a straight tube cross- sectional area being at least substantially equal to relative to each other and at least substantially equal to the return bend cross-sectional area.

10. A serpentine tube, comprising: a serpentine tube body disposed in plane, forming a hollow passageway and having a plurality of straight tube sections arranged generally parallel with one another, a plurality of return bends and a plurality of transition sections, a respective one of the plurality of transition sections interconnecting respective ones of the plurality of straight tube sections and the return bends to form a serpentine configuration, each straight tube section having a generally uniform straight tube section cross-sectional configuration and a straight tube cross-sectional width, each return bend having a generally uniform return bend cross-sectional configuration and a return bend cross-sectional width being smaller than the straight tube cross- sectional width.

11. A serpentine tube according to claim 10, wherein a width ratio of the straight tube cross-sectional width to the return bend cross-sectional width is in a range of approximately 1.2 and 1.3.

12. A serpentine tube according to claim 10, wherein a width ratio of the straight tube cross-sectional width to the return bend cross-sectional width is in a range of approximately 1.1 and 1.6.

13. A heat exchanger apparatus, 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 adjacent serpentine tube bodies staggered in an alternating fashion, respective ones of the plurality of adjacent serpentine tube bodies connected to and between and in fluid communication with the inlet header and the outlet header, each serpentine tube body disposed in a selected one of a plurality of parallel planes in a juxtaposed manner, forming a hollow passageway and having a plurality of straight tube sections arranged generally parallel with one another, a plurality of return bends and a plurality of transition sections, a respective one of the plurality of transition sections interconnecting respective ones the plurality of straight tube sections and the return bends to form a serpentine configuration, each straight tube section having a generally uniform straight tube section cross-sectional configuration and a straight tube cross-sectional width, each return bend having a generally uniform return bend cross-sectional configuration and a return bend cross- sectional width being smaller than the straight tube cross-sectional width, staggered juxtaposed ones of the return bends contacting one another at a location where the staggered juxtaposed ones of the return bends cross one another.

14. A heat exchanger according to claim 13, wherein a width ratio of the straight tube cross-sectional width to the return bend cross-sectional width is in a range of approximately 1.2 and 1.3.

15. A heat exchanger according to claim 13, wherein a width ratio of the straight tube cross-sectional width to the return bend cross-sectional width is in a range of approximately 1.1 and 1.6.