BACKGROUND OF THE INVENTION
This invention relates generally to heat exchangers and, more particularly, to a folded tube multiple bank heat exchange unit.
Heat exchangers have long been used as evaporators and condensers in heating, ventilation, air conditioning and refrigeration (HVACR) applications. Historically, these heat exchangers have been round tube and plate fin (RTPF) heat exchangers. However, all aluminum flattened tube serpentine fin heat exchangers are finding increasingly wider use in industry, including the HVACR industry, due to their compactness, thermal-hydraulic performance, structural rigidity, lower weight and reduced refrigerant charge, in comparison to conventional RTPF heat exchangers. Flattened tubes commonly used in HVACR applications typically have an interior subdivided into a plurality of parallel flow channels. Such flattened tubes are commonly referred to in the art as multi-channel tubes, mini-channel tubes or micro-channel tubes. Flattened tube serpentine fin heat exchangers may include a single tube bank of flattened tubes and two or multiple tube banks of flattened tubes.
Existing manufacturing techniques for flattened tubes involve an extrusion process. The extrusion process is costly and often requires specialty manufacturing equipment, often complicating the supply chain. Furthermore, the extrusion process is limited to certain class of aluminum alloys, due to manufacturing limitations and production cost, often detrimentally affecting corrosion durability of the flattened tube and the entire heat exchanger. There also exist techniques for forming a folded, single bank flattened tube from sheet material.
SUMMARY OF THE INVENTION
In an aspect, a multiple bank, flattened tube heat exchange unit includes a first tube bank including a flattened first tube segment extending longitudinally between a first manifold and a second manifold; and a second tube bank including a flattened second tube segment extending longitudinally between the first manifold and the second manifold, the second tube bank disposed behind the first tube bank; wherein an outer surface of the first tube segment and an outer surface of the second tube segment are formed from a single sheet of material.
In another aspect, a method of forming a multiple bank, flattened tube heat exchange unit includes obtaining a single sheet of material, the single sheet of material having a longitudinal axis; bending a first portion of the single sheet of material towards the longitudinal axis to define an outer surface of a first tube segment; and bending a second portion of the single sheet of material towards the longitudinal axis to define an outer surface of a second tube segment.
In another aspect, a method of forming a multiple bank, flattened tube heat exchange unit includes obtaining a single sheet of material, the single sheet of material having a longitudinal axis; and bending a first portion of the single sheet of material towards the longitudinal axis to define an outer surface of a first tube segment and define an outer surface of a second tube segment.
Other aspects, features, and techniques of embodiments of the invention will become more apparent from the following description taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
For further understanding of the disclosure, reference will be made to the following detailed description which is to be read in connection with the accompanying drawing, where:
FIG. 1 is a diagrammatic illustration of an exemplary embodiment of a multiple tube bank, flattened tube finned heat exchange unit;
FIG. 2 is a side elevation view, partly in section, illustrating an exemplary embodiment of a fin and a set of integral flattened tube segments of the heat exchange unit of FIG. 1;
FIG. 3 depicts a sheet of material for forming a first tube segment and a second tube segment in an exemplary embodiment;
FIGS. 4-6 depict forming a first tube segment and a second tube segment in an exemplary embodiment;
FIGS. 7-9 depict forming a first tube segment and a second tube segment in an exemplary embodiment;
FIGS. 10-11 depict an orientation of an edge of sheet material in exemplary embodiments;
FIGS. 12-14 depict forming a first tube segment and a second tube segment in an exemplary embodiment;
FIG. 15 is a flowchart of a process of forming a first tube segment and a second tube segment in an exemplary embodiment; and
FIG. 16 is a top down view of a heat exchange unit in an exemplary embodiment.
DETAILED DESCRIPTION
An exemplary embodiment of a multiple bank flattened tube finned heat exchange unit in accordance with the disclosure, generally designated 10, is depicted in perspective illustration in FIG. 1. As depicted therein, the multiple bank flattened tube finned heat exchange unit 10 includes a first tube bank 100 and a second tube bank 200 that is disposed behind the first tube bank 100, that is downstream with respect to air flow, A, through the heat exchanger. The first tube bank 100 may also be referred to herein as the front heat exchanger slab 100 and the second tube bank 200 may also be referred to herein as the rear heat exchanger slab 200.
The first tube bank 100 includes a first manifold 102, a second manifold 104 spaced apart from the first manifold 102, and a plurality of heat exchange tube segments 106, including at least a first and a second tube segment, extending longitudinally in spaced parallel relationship between and connecting the first manifold 102 and the second manifold 104 in fluid communication. The second tube bank 200 includes a first manifold 202, a second manifold 204 spaced apart from the first manifold 202, and a plurality of heat exchange tube segments 206, including at least a first and a second tube segment, extending longitudinally in spaced parallel relationship between and connecting the first manifold 202 and the second manifold 204 in fluid communication. Each set of manifolds 102, 202 and 104, 204 disposed at either side of the dual bank heat exchanger 10 may comprise separate paired manifolds, may comprise separate chambers within an integral one-piece folded manifold assembly or may comprise separate chambers within an integral fabricated (e.g. extruded, drawn, rolled and welded) manifold assembly. Each tube bank 100, 200 may further include “dummy” tubes (not shown) extending between its first and second manifolds typically at the top of the tube bank and at the bottom of the tube bank. These “dummy” tubes do not convey refrigerant flow, but add structural support to the tube bank and protect the uppermost and lowermost fins.
Referring now to FIG. 2, each of the heat exchange tube segments 106, 206 comprises a flattened heat exchange tube having a leading edge 108, 208, a trailing edge 110, 210, an upper surface 112, 212, and a lower surface 114, 214. The leading edge 108, 208 of each heat exchange tube segment 106, 206 is upstream of its respective trailing edge 110, 210 with respect to airflow through the heat exchange unit 10. In the embodiment depicted in FIG. 2, the respective leading and trailing portions of the flattened tube segments 106, 206 are rounded thereby providing blunt leading edges 108, 208 and trailing edges 110, 210. However, it is to be understood that the respective leading and trailing portions of the flattened tube segments 106, 206 may be formed in other configurations.
The interior flow passage of each of the heat exchange tube segments 106, 206 of the first and second tube banks 100, 200, respectively, may be divided by interior walls into a plurality of discrete flow channels 120, 220 that extend longitudinally the length of the tube segment from an inlet end of the tube segment to an outlet end of the tube segment and establish fluid communication between the respective headers of the first and the second tube banks 100, 200. In the embodiment of the multi-channel heat exchange tube segments 106, 206 depicted in FIG. 2, the heat exchange tube segments 206 of the second tube bank 200 have a greater width than the heat exchange tube segments 106 of the first tube bank 100. Also, the interior flow passages of the wider heat exchange tube segments 206 may be divided into a greater number of discrete flow channels 220 than the number of discrete flow channels 120 into which the interior flow passages of the heat exchange tube segments 106 are divided. The flow channels 120, 220 may have a circular cross-section, a rectangular cross-section or other non-circular cross-section.
The second tube bank 200, i.e. the rear heat exchanger slab, is disposed behind the first tube bank 100, i.e. the front heat exchanger slab, with respect to the airflow direction, with each heat exchange tube segment 106 directly aligned with a respective heat exchange tube segment 206 and with the leading edges 208 of the heat exchange tube segments 206 of the second tube bank 200 spaced from the trailing edges 110 of the heat exchange tube segments of the first tube bank 100 by a desired spacing, G.
In the embodiment depicted in FIG. 2, an elongated web 40 or a plurality of spaced web members 40 span the desired spacing, G, along at least of portion of the length of each aligned set of heat exchange tube segments 106, 206. For a further description of a dual bank, flattened tube finned heat exchanger unit wherein the heat exchange tubes 106 of the first tube bank 100 and the heat exchange tubes 206 of the second tube bank 200 are connected by an elongated web or a plurality of web members, reference is made to U.S. provisional application Ser. No. 61/593,979, filed Feb. 2, 2012, the entire disclosure of which is hereby incorporated herein by reference.
Referring still to FIGS. 1 and 2, the flattened tube finned heat exchange unit 10 disclosed herein further includes a plurality of folded fins 320. Each folded fin 320 is formed of a single continuous strip of fin material tightly folded in a ribbon-like serpentine fashion thereby providing a plurality of closely spaced fins 322 that extend generally orthogonal to the flattened heat exchange tube segments 106, 206. Typically, the fin density of the closely spaced fins 322 of each continuous folded fin 320 may be about 16 to 25 fins per inch, but higher or lower fin densities may also be used. Heat exchange between the refrigerant flow, R, and air flow, A, occurs through the outside surfaces 112, 114 and 212, 214, respectively, of the heat exchange tube segments 106, 206, collectively forming the primary heat exchange surface, and also through the heat exchange surface of the fins 322 of the folded fin 320, which forms the secondary heat exchange surface.
In the depicted embodiment, the depth of each of the ribbon-like folded fin 320 extends at least from the leading edge 108 of the first tube bank 100 to the trailing edge of 210 of the second bank 200, and may overhang the leading edge 108 of the first tube bank 100 or/and trailing edge 210 of the second tube bank 200 as desired. Thus, when a folded fin 320 is installed between a set of adjacent multiple tube, flattened heat exchange tube assemblies in the array of tube assemblies of the assembled heat exchange unit 10, a first section 324 of each fin 322 is disposed within the first tube bank 100, a second section 326 of each fin 322 spans the spacing, G, between the trailing edge 110 of the first tube bank 100 and the leading edge 208 of the second tube bank 200, and a third section 328 of each fin 322 is disposed within the second tube bank 200. In an embodiment, each fin 322 of the folded fin 320 may be provided with louvers 330, 332 formed in the first and third sections, respectively, of each fin 322.
The multiple bank, flattened tube heat exchange unit 10 disclosed herein is depicted in a cross-counterflow arrangement wherein refrigerant (labeled “R”) from a refrigerant circuit (not shown) of a refrigerant vapor compression system (not shown) passes through the manifolds and heat exchange tube segments of the tube banks 100, 200, in a manner to be described in further detail hereinafter, in heat exchange relationship with a cooling media, most commonly ambient air, flowing through the airside of the heat exchanger 10 in the direction indicated by the arrow labeled “A” that passes over the outside surfaces of the heat exchange tube segments 106, 206 and the surfaces of the folded fins 320. The air flow first passes transversely across the upper and lower horizontal surfaces 112, 114 of the heat exchange tube segments 106 of the first tube bank, and then passes transversely across the upper and lower horizontal surfaces 212, 214 of the heat exchange tube segments 206 of the second tube bank 200. The refrigerant passes in cross-counterflow arrangement to the airflow, in that the refrigerant flow passes first through the second tube bank 200 and then through the first tube bank 100. The multiple tube bank, flattened tube finned heat exchange unit 10 having a cross-counterflow circuit arrangement yields superior heat exchange performance, as compared to the crossflow or cross-parallel flow circuit arrangements, as well as allows for flexibility to manage the refrigerant side pressure drop via implementation of tubes of various widths within the first tube bank 100 and the second tube bank 200.
A method of manufacturing heat exchange tube segments 106, 206 and at least one web 40 is described with reference to FIGS. 3-6. The manufacturing method includes folding a sheet of stock material to define tube segments 106, 206 and at least one web 40. FIG. 3 depicts a sheet 410 of stock material such as a metal (e.g., aluminum). Sheet 410 may be clad on both sides with a brazing alloy. The sheet 410 is stamped or punched to define a notch 412 along a lateral edge of the sheet 410. A notch 412 may be formed at each distal end, or lateral edge, of sheet 410. Notches 412 define how deep first tube segment 106 and second tube segment 206 can be inserted into manifolds 102, 104, 202 and 204. Slots 414 are also stamped or punched from sheet 410. Slots 414 promote water drainage (e.g., condensate drainage) and prevent thermal cross-conduction between first tube segments 106 and second tube segments 206. Slots 414 are formed in the interior of sheet 410, intermediate the distal ends of sheet 410. Notches 412 and slots 414 are formed along a central, longitudinal axis of sheet 410. The remaining material along longitudinal axis, C, are webs 40, that join the first tube segment 106 and second tube segment 206. It is understood that axis C need not be centrally located on sheet 410, in embodiments where tube segment 106 and tube segment 206 have different widths.
The first tube segment 106 and second tube segment 206 are formed, in an exemplary embodiment, as shown in FIGS. 4-6. Referring the FIG. 4, a first corrugated section 420 is formed along a first longitudinal edge of sheet 410. The first corrugated section 420 may be stamped, punched, or otherwise formed in sheet 410. First corrugated section 420 includes a series of peaks and troughs that eventually define flow channels 120 of first tube segment 106. The peaks and troughs are shown as square in FIG. 4, but it is understood that other cross-sections may be used in first corrugated section 420. A second corrugated section 422 is formed along a second longitudinal edge of sheet 410. The second corrugated section 422 may be stamped, punched, or otherwise formed in sheet 410. Second corrugated section 422 includes a series of peaks and troughs that eventually define flow channels 220 of second tube segment 206. The peaks and troughs are shown as square in FIG. 4, but it is understood that other cross-sections may be used in second corrugated section 422.
As shown in FIGS. 4 and 5, first corrugated section 420 is bent about 180 degrees along a longitudinal axis parallel to axis C, inwards towards axis C, to form a first bend 424 of first section 420. Similarly, second corrugated section 422 is bent about 180 degrees along a longitudinal axis parallel to axis C, inwards towards axis C to form a first bend 426 of second section 422. As shown in FIGS. 5 and 6, again the first corrugated section 420 is bent about 180 degrees along a longitudinal axis parallel to axis C, inwards towards axis C, to form a second bend 425 of first section 420. Similarly, second corrugated section 422 is bent about 180 degrees along a longitudinal axis parallel to axis C, inwards towards axis C, to form a second bend 427 of second section 422. The two bending steps form first tube segment 106 and second tube segment 206. The corrugated sections 420 and 422 define the flow channels 120 and 220, respectively, in first tube segment 106 and second tube segment 206. First bend 424 of first section 420 corresponds to trailing edge 110 of first tube segment 106. Second bend 425 of first section 420 corresponds to leading edge 108 of first tube segment 106. First bend 426 of second section 422 corresponds to leading edge 208 of second tube segment 206. Second bend 427 of second section 422 corresponds to trailing edge 210 of second tube segment 206. In FIGS. 4-6, the outer surface of the first tube segment 106, flow channels 120, the outer surface of the second tube segment 206, flow channels 220 and the at least one web 40 are formed from a single sheet 410.
The formed first tube segment 106 and second tube segment 206 are joined by at least one web 40. The first tube segment 106 and second tube segment 206 may then be brazed using known techniques, such as controlled atmosphere brazing. The brazing process seals the corrugated sections 420 and 422 to the adjacent sheet material to seal first tube segment 106 and second tube segment 206. In an alternative embodiment, a plurality of first tube segments 106 and second tube segments 206 are assembled to manifolds 102, 104, 202 and 204, along with folded fins 320. The entire assembly may then be brazed using known techniques, such as controlled atmosphere brazing.
An alternative method of manufacturing heat exchange tube segments 106, 206 and web 40 is described with reference to FIGS. 7-9. The manufacturing method includes folding the sheet 410 of stock material to define tube segments 106, 206 and at least one web 40. Prior to folding, as described above with reference to FIG. 3, one or more notches 412 and/or one or more slots 414 may be formed in sheet 410.
The first tube segment 106 and second tube segment 206 are formed as shown in FIGS. 7-9. Referring the FIG. 7, a first corrugated section 420 is formed along a first longitudinal axis of sheet 410, at an interior of sheet 410, proximate to a central axis, C. The first corrugated section 420 may be formed by a separate sheet of material placed on top of sheet 410. First corrugated section 420 includes a series of peaks and troughs that eventually define flow channels 120 of first tube segment 106. The peaks and troughs are shown as square in FIG. 7, but it is understood that other cross-sections may be used in first corrugated section 420. A second corrugated section 422 is formed along a second longitudinal axis of sheet 410, at an interior of sheet 410, proximate to a central axis, C, and on an opposite side of axis C as first corrugated section 420. The second corrugated section 422 may be formed by a separate sheet of material placed on top of sheet 410. Second corrugated section 422 includes a series of peaks and troughs that eventually define flow channels 220 of second tube segment 206. The peaks and troughs are shown as square in FIG. 7, but it is understood that other cross-sections may be used in second corrugated section 422.
As shown in FIGS. 7 and 8, a first section 411 of sheet 410 is bent about 180 degrees along a longitudinal axis parallel to axis C, inwards towards axis C to form a first bend 424 of first section 411. Similarly, second section 413 is bent about 180 degrees along a longitudinal axis parallel to axis C, inwards towards axis C to form a first bend 426 of second section 413. As shown in FIGS. 8 and 9, the first section 411 is bent along a longitudinal axis parallel to axis C, downwards towards axis C, to form a second bend 425 of first section 411. Similarly, second section 413 is bent along a longitudinal axis parallel to axis C, downwards towards axis C, to form a second bend 427 of second section 413. The two bending steps form first tube segment 106 and second tube segment 206. The corrugated sections 420 and 422 define the flow channels 120 and 220, respectively, in first tube segment 106 and second tube segment 206. First bend 424 of first section 411 corresponds to leading edge 108 of first tube segment 106. Second bend 425 of first section 420 corresponds to trailing edge 110 of first tube segment 106. First bend 426 of second section 413 corresponds to trailing edge 210 of second tube segment 206. Second bend 427 of second section 413 corresponds to leading edge 208 of second tube segment 206.
The outer surface of the first tube segment 106, the outer surface of the second tube segment 206, and the at least one web 40 are formed from a single sheet of stock material 410.
The formed first tube segment 106 and second tube segment 206 are joined by at least one web 40. The first tube segment 106 and second tube segment 206 may then be brazed using known techniques, such as controlled atmosphere brazing. The brazing process seals the corrugated sections 420 and 422 to the adjacent sheet material to seal first tube segment 106 and second tube segment 206. In an alternative embodiment, a plurality of first tube segments 106 and second tube segments 206 are assembled to manifolds 102, 104, 202 and 204, along with folded fins 320. The entire assembly may then be brazed using known techniques, such as controlled atmosphere brazing.
The folding directions of sheet 410 in FIGS. 4-9 are exemplary, and a number of differing folding orientations may be used in forming first tube segment 106 and second tube segment 206. For example, FIG. 10 is an enlarged view of second bend 425 from FIG. 9. As shown in FIG. 10, an edge 429 of sheet 410 defines the end of bend 425. Edge 429 may be bent inwardly towards the interior of tube segment 106. As shown in FIG. 11, edge 429 may be bent outwardly towards the web 40. This is just one example of alternative bend directions that may be used over several sections of first tube segment 106 and second tube segment 206. Further, localized features, such as nesting pockets, overlaps, and ribs can be incorporated into the design to promote brazing, structural strength, etc.
An alternative method of manufacturing heat exchange tube segments 106, 206 and web 40 is described with reference to FIGS. 12-14. The manufacturing method includes folding the sheet 410 of stock material to define tube segments 106, 206 and at least one web 40. Prior to folding, as described above with reference to FIG. 3, one or more notches 412 and/or one or more slots 414 may be formed in sheet 410 between locations of first corrugated section 420 and second corrugated section 422.
The first tube segment 106 and second tube segment 206 are formed as shown in FIGS. 12-14. Referring the FIG. 12, a first corrugated section 420 is formed along a first longitudinal axis of sheet 410. The first corrugated section 420 may be formed by stamping sheet 410 or may be a separate sheet of material placed on top of sheet 410. First corrugated section 420 includes a series of peaks and troughs that eventually define flow channels 120 of first tube segment 106. The peaks and troughs are shown as square in FIG. 12, but it is understood that other cross-sections may be used in first corrugated section 420.
A second corrugated section 422 is formed along a second longitudinal axis of sheet 41, on the same side of axis C as first corrugated section 420. The second corrugated section 422 may be formed by stamping sheet 410 or may be separate sheet of material placed on top of sheet 410. Second corrugated section 422 includes a series of peaks and troughs that eventually define flow channels 220 of second tube segment 206. The peaks and troughs are shown as square in FIG. 12, but it is understood that other cross-sections may be used in second corrugated section 422.
Also formed in sheet 410 is a rib 440, which may be formed by stamping sheet 410. Rib 440 is generally rectangular and is formed along a longitudinal axis parallel to longitudinal axis, C. Rib 440 has a width substantially corresponding to web 40. One or more notches 412 and one or more slots 414 may be formed in rib 440, to correspond notches and/or slots formed in web 40 between first corrugated section 420 and second corrugated section 422.
As shown in FIGS. 12 and 13, a first section 411 of sheet 410, including rib 440, is bent about 180 degrees along a longitudinal axis parallel to axis C, inwards towards axis C to form a first bend 424 of first section 411. This places rib 440 juxtaposed web 40 between first corrugated section 420 and second corrugated section 422. As shown in FIGS. 13 and 14, an edge of first section 411 is bent along a longitudinal axis parallel to axis C, towards axis C, to form a second bend 426 of first section 411. The bending steps form first tube segment 106 and second tube segment 206. The corrugated sections 420 and 422 define the flow channels 120 and 220, respectively, in first tube segment 106 and second tube segment 206. First bend 424 of first section 411 corresponds to trailing edge 210 of second tube segment 206. Second bend 426 of first section 411 corresponds to leading edge 108 of first tube segment 106. A first interior wall 425 of rib 440 corresponds to trailing edge 110 of first tube segment 106. A second interior wall 427 of rib 440 corresponds to leading edge 208 of second tube segment 206.
The outer surface of the first tube segment 106, the outer surface of the second tube segment 206, and the at least one web 40 are formed from a single sheet of stock material 410.
The formed first tube segment 106 and second tube segment 206 are joined by at least one web 40. The first tube segment 106 and second tube segment 206 may then be brazed using known techniques, such as controlled atmosphere brazing. The brazing process seals the corrugated sections 420 and 422 to the adjacent sheet material to seal first tube segment 106 and second tube segment 206. In an alternative embodiment, a plurality of first tube segments 106 and second tube segments 206 are assembled to manifolds 102, 104, 202 and 204, along with folded fins 320. The entire assembly may then be brazed using known techniques, such as controlled atmosphere brazing.
FIG. 15 is a flowchart of a process of forming a first tube segment and second tube segment in an exemplary embodiment. The process begins at 500 where sheet 410 is obtained. Sheet 410 may be a metal (e.g. aluminum) and may be clad on both sides with a brazing alloy. At 502, notches 412 may be formed at each end of sheet 410, about a longitudinal axis. Slots 414 may also be formed at 502 along the longitudinal axis.
At 504, the corrugated sections 420 and 422 are formed on sheet 410. This may entail stamping or punching the corrugated sections into sheet 410. Alternatively, as shown in FIGS. 7-9, this may entail using a second sheet of material having the corrugations formed therein. At 506, the outer sections of the sheet material are bent inwards towards the longitudinal axis to form the first tube segment 106 and second tube segment 206. At 508, brazing is performed. This may entail brazing just the first tube segment 106 and second tube segment 206. Alternatively, a plurality of first tube segments 106 and second tube segments 206 are assembled to manifolds 102, 104, 202 and 204, along with folded fins 320, and then brazing is performed.
Forming the tube segments 106, 206 and web 40 by folding sheet 410 eliminates the need for an extrusion process, allowing tube fabrication at the heat exchanger manufacturer site, reducing logistics complexity, improving reliability and providing noticeable cost savings. Additionally, the material system limitations imposed by the extrusion process can be avoided and heat exchanger corrosion durability significantly improved.
It is understood that various tube folding patterns can be employed and will not deviate from the scope and spirit of the invention. Furthermore, at least one of the tube segments 106, 206 may not have internal ports and may carry a separate fluid. In the latter case, the manifolds in the first tube bank 100 and in the second tube bank 200 are separated, while the tube banks have independent inlet pipes and outlet pipes. This is shown in FIG. 16, which is a top down view of heat exchange unit 10, where manifolds 102, 104 of first tube bank 100 are not in fluid communication with manifolds 202, 204 of tube bank 200. First tube bank 100 and second tube bank 200 have independent inlet pipes 142, 242 and outlet pipes 144, 244, respectively.
While the present invention has been particularly shown and described with reference to the exemplary embodiments as illustrated in the drawing, it will be recognized by those skilled in the art that various modifications may be made without departing from the spirit and scope of the invention. Therefore, it is intended that the present disclosure not be limited to the particular embodiment(s) disclosed as, but that the disclosure will include all embodiments falling within the scope of the appended claims.
Patent Application
20160054075
