Patent Application
20160018167
The invention relates to a heat exchanger, and more specifically to a heat exchanger including a flat tube having a reinforcing structure formed therein.
Heat exchangers having folded flat tubes are well known in the art. Such heat exchangers typically include a plurality of the folded flat tubes spaced apart and arranged in parallel and extending between an inlet header and an outlet header. The inlet header receives a first fluid and distributes the first fluid flow amongst a plurality of flow paths formed in the flat tubes. The first fluid exchanges heat energy with a second fluid flowing through the spaces between adjacent ones of the flat tubes. The first fluid then enters the outlet header before exiting the heat exchanger.
One common construction of a folded flat tube includes folding a sheet of aluminum into a tubular structure and brazing or welding the resulting seam. This construction results in a flat tube having a width extending from one folded portion to an opposite folded portion that is substantially larger than a height of the flat tube, causing the flat tube to be susceptible to deformation in a central region thereof due to internal pressures experienced within the flat tube.
The current trend in modern heat exchanger tube construction focuses on reinforcing this central region by adding one or more folds within the central region of each of the flat tubes. A sheet of aluminum forming the flat tube is folded in a manner that causes each of the folded portions to abut an inner surface of the flat tube along a length thereof, causing the hollow interior of the flat tubes to be divided into numerous flow paths while also reinforcing the flat tube along selected regions. However, the folded flat tube construction presents an additional problem as the addition of independent flow channels may result in significant differences in temperature and flow characteristics between each of the flow channels. These differences can result in a shear stress being formed between the flow channels which can in turn result in the generation of a significant bending moment within the tube. Such bending moments can cause a reduction in the durability of the tubes during thermal cycle testing and may also lead to premature cracking and leakage.
It would therefore be desirable to produce a tube for use in a heat exchanger having a reinforced central region and fluid communication channels formed between adjacent flow paths formed within the tube.
Compatible and attuned with the present invention, a tube having a reinforcing structure and a fluid communication channel formed between adjacent flow paths formed therein has surprisingly been discovered.
In one embodiment of the invention, a tube for use in a heat exchanger comprises a first portion spaced apart from a second portion and at least one reinforcing structure extending between the first portion and the second portion to divide the tube into a first flow channel and a second flow channel. Each of the at least one reinforcing structures has a non-circular cross-sectional shape. A first fluid communication channel providing fluid communication between the first flow channel and the second flow channel is at least one of formed through the at least one reinforcing structure and fanned between two adjacent ones of the reinforcing structures.
In another embodiment of the invention, a heat exchanger comprises an inlet header, an outlet header, and a tube fluidly coupling the inlet header to the outlet header. The tube includes a first portion spaced apart from a second portion. A plurality of first projections extend from an interior surface of the first portion and a plurality of second projections extend from an interior surface of the second portion and each of the first projections is coupled to a corresponding one of the second projections to form a plurality of reinforcing structures within the tube. Each of the reinforcing structures has a non-circular cross-sectional shape.
In another embodiment of the invention, a tube for use in a heat exchanger comprises a reinforcing structure extending along a length of the tube, wherein the reinforcing structure is formed by bending two opposing edges of a sheet forming the tube to contact each other at a substantially planar portion of the sheet formed intermediate the opposing edges. An aperture is formed adjacent each of the opposing edges and the reinforcing structure divides a flow of fluid through the tube into a first flow channel and a second flow channel. The apertures formed adjacent the opposing edges are aligned to form a fluid communication channel fluidly coupling the first flow channel to the second flow channel.
The above, as well as other objects and advantages of the invention, will become readily apparent to those skilled in the art from reading the following detailed description of a preferred embodiment of the invention when considered in the light of the accompanying drawings:
The following detailed description and appended drawings describe and illustrate various embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. In respect of the methods disclosed, the steps presented are exemplary in nature, and thus, the order of the steps is not necessary or critical.
Each of the tubes 40 includes a hollow interior 42 extending from an open first end 43 thereof to an open second end 45 thereof. The open first end 43 of each of the tubes 40 acts as a fluid inlet 44 and the open second end 45 of each of the tubes 40 acts as a fluid outlet 46. The fluid inlet 44 fluidly couples the hollow interior 42 of each of the tubes 40 to a hollow interior 22 of the inlet header 20 and the fluid outlet 46 fluidly couples the hollow interior 42 of each of the tubes 40 to a hollow interior 32 of the outlet header 30.
Referring now to
As shown in
The exterior surface 54 of the second major portion 12 of the tube 40 also includes an array of the dimples 60 formed therein. Each of the dimples 60 formed in the second major portion 12 is aligned with a corresponding dimple 60 formed in the first major portion 11. For instance, when the first major portion 11 is viewed from above as shown in
Referring again to
The coupling surface 64 of each of the projections 55 formed in the first major portion 11 of the tube 40 abuts and is coupled to a coupling surface 64 formed in a corresponding projection 55 formed in the second major portion 12 of the tube 40. Due to the manner in which the dimples 60 formed in the first major portion 11 are substantially aligned with the dimples 60 formed in the second major portion 12, the coupling surfaces 64 of the corresponding projections 55 may also be substantially aligned. The coupling surfaces 64 may be coupled to each other by any method known in the art such as brazing, welding, or bonding, as non-limiting examples. The coupling may be performed about an entirety of a perimeter of each of the coupling surfaces 64 to create a fluid tight seal between the corresponding projections 55.
The coupling of the corresponding projections 55 extending from each of the first major portion 11 and the second major portion 12 creates a plurality of reinforcing structures 68 extending therebetween. Each of the reinforcing structures 68 may have a substantially hour-glass appearance due to the presence of the sloped portions 63, but it should be understood that the reinforcing structures 68 may have any shape without departing from the scope of the current invention. Because of the elongated elliptical shape of each of the dimples 60, each of the reinforcing structures 68 will have an elliptical cross-section as each of the reinforcing structures 68 extend between the first major portion 11 and the second major portion 12. The elongated elliptical cross-sectional shape of the reinforcing structures 68 advantageously allows for a fluid flowing through each of the tubes 40 to be divided to each side of each of the reinforcing structures 68 without undergoing a substantial pressure drop due to the shape and curvature of the leading edge of each of the reinforcing structures 68 being somewhat pointed and oriented in a direction extending along a longitudinal axis of each of the tubes 40.
The reinforcing structures 68 substantially divide a flow of a fluid through the tube 40 into a first flow channel 71 formed to one side of the reinforcing structures 68 and adjacent the first side portion 13 and a second flow channel 72 formed to the other side of the reinforcing structures 68 and adjacent the second side portion 14. However, as best shown in
Referring now to
Referring back to
The reinforcing structure 68 formed closest to the first end 43 of the tube 40, and hence the fluid inlet 44 thereof, may be formed at a distance of at least zero to six times the height H of the tube 40 from the first end 43 thereof. The spacing of the first reinforcing structure 68 from the fluid inlet 44 of the tube 40 facilitates a more even fluid flow into the tube 40 adjacent the fluid inlet 44. The reinforcing structure 68 formed closest to the first end 43 of the tube 40 may also be spaced at a distance of at least zero to five times the height H of the tube 40 from the interface of the tube 40 and the opening 21 formed in the inlet header 20 to facilitate a strengthening of the tube 40 and to minimize an occurrence of overstressing along the centerline A of the tube 40 due to internal pressures and thermal loads experienced within the tube 40. Similarly, the reinforcing structure 68 formed closest to the second end 45 of the tube 40, and hence the fluid outlet 46 thereof, may also be spaced at a distance of at least zero to five times the height H of the tube 40 from the interface of the tube 40 and the opening 31 formed in the outlet header 30.
In use, a first fluid enters the inlet header 20 and is distributed to each of the tubes 40 via the fluid inlet 44 formed at the first end 43 thereof. The first fluid flows through the hollow interior 42 of each of the tubes 40 before encountering the reinforcing structures 68 formed therein. Upon encountering the reinforcing structures 68, a first portion of the flow of the first fluid flows through the first flow channel 71 to one side of the reinforcing structure 68 and a second portion of the flow of the first fluid flows through the second flow channel 72 to a second side of the reinforcing structure 68. The first fluid flow encountering each of the reinforcing structures 68 also increases a turbulence of the first fluid flow, thereby increasing the capacity for the first fluid to exchange heat with a second fluid flowing around an exterior of each of the tubes 40.
The fluid communication channels 80 formed between adjacent ones of the reinforcing structures 68 allow the flow of the first fluid in the first flow channel 71 to communicate with and mix with the flow of the first fluid in the second flow channel 72. As a result, the first fluid is prevented from developing a substantial temperature gradient between adjacent regions of the hollow interior 42 of each of the tubes 40, minimizing an occurrence of localized thermal stresses within each of the tubes 40. Additionally, the presence of the reinforcing structures 68 may provide for improved mixing, turbulence, and vortex flow of the first fluid as the first fluid encounters the reinforcing structures 68 to improve the heat exchange characteristics of the first fluid. The resulting flow of the first fluid exchanges heat energy through the walls of each of the tubes 40 with a flow of the second fluid flowing between adjacent ones of the tubes 40. The first fluid then exits each of the tubes 40 where the first fluid recombines in the outlet header 30 before exiting the heat exchanger 10.
As described hereinabove, the size, shape, and arrangement of the dimples 60 and hence the reinforcing structures 68 is selected to provide for desirable flow characteristics within the hollow interior 42 of each of the tubes 40. For example, referring to
The reinforcing structures 68 also prevent an occurrence of outward bowing of each of the tubes 40 along or adjacent the centerline A thereof due to internal pressures formed within each of the tubes 40. Accordingly, the reinforcing structures 68 may beneficially be formed adjacent or overlapping the centerline A of each of the tubes 40. As described hereinabove, the coupling of corresponding projections 55 is performed about a perimeter of each of the abutting coupling surfaces 64 to form a single one of the reinforcing structures 68. A combined length of the perimeters of all of the mating coupling surfaces 64 formed in a single tube 40 may accordingly be chosen to be greater than a length of each of the tubes 40 measured from the first end 43 thereof to the second end thereof 45. The combined length of the coupled perimeters being greater than the length of each of the tubes 40 allows for the tube 40 having the reinforcing structures 68 to provide for greater strength than a traditional elongated tube having a single seam extending along a length thereof. Furthermore, a number, orientation, and geometry of the reinforcing structures 68 may be selected to impart desirable heat exchange and flow characteristics to the first fluid while preventing an excessive pressure drop within the first fluid as it flows along a length of each of the tubes 40.
Each of the tubes 40 may be formed from a sheet of any suitable material having suitable strength and thermal conductivity to withstand any internal pressures within each of the tubes 40 and to efficiently conduct heat energy between the first fluid flowing within each of the tubes 40 and the second fluid flowing around each of the tubes 40. Additionally, the material may be selected to ensure that each of the tubes 40 may be easily coupled to each of the inlet header 20 and the outlet header 30 by a suitable coupling means, such as brazing. The sheet of material may for instance have an aluminium base that is clad with an aluminium-based braze alloy on both sides.
The sheet may begin as a substantially planar sheet before being formed into each of the first major portion 11, the second major portion 12, the first side portion 13, and the second side portion 14 when bent into the shape shown in
If brazing is used, the brazing may be applied to a portion or an entirety of the perimeter of the contacting coupling surfaces 64 forming each respective reinforcing structure 68. The brazing may be performed within the hollow interior 42 of each of the tubes 40 at the junction of each of the contacting projections 55. The hollow interior 42 of each of the tubes 40 may be accessed via one of the open first end 43 and the open second end 45 of each of the tubes 40. The use of interior brazing advantageously militates against an occurrence of leaking adjacent any of the reinforcing structures 68 because the braze alloy clad on the sheet forming each of the tubes 40 is drawn between two of the solid projections 55 instead of being applied at a seam separating an interior of the tube 40 from an exterior thereof. Accordingly, there is no risk of a fluid leaking into or out of the tube 40 if any of the surfaces brazed together within the hollow interior 42 of one of the tubes 40 become separated or otherwise fail.
Once the reinforcing structures 68 have been formed by coupling the projections 55, each of the tubes 40 is completed by forming the one of the first side portion 13 and the second side portion 14 that was not formed when the sheet was bent about the line of symmetry and then coupling the remaining edges of the sheet to each other. The forming of the remaining side portion 13, 14 may include bending at least one of the first major portion 11 and the second major portion 12 of the tube 40 toward the other. Accordingly, a remaining seam of each of the tubes 40 may be formed adjacent the one of the side portions 13, 14 not formed when the projections 55 are initially aligned with each other. The one of the side portions 13, 14 having the seam formed adjacent thereto may have a substantially arcuate shape due to a single bend being formed or may include two or more bends, as desired. The sheet may be coupled to itself along the remaining seam by any known means in the art including welding or brazing, as non-limiting examples. It should be understood that the seam formed along the length of each of the tubes 40 is not required to be formed adjacent one of the side portions 13, 14, and may be formed anywhere about a circumference of each of the tubes 40, as desired, so long as the reinforcing structures 68 are able to be formed in a suitable manner. Furthermore, the first side portion 13 is shown in
The symmetric arrays of the dimples 60 formed in the sheet may be formed by any known method including stamping, for example. As described hereinabove, it may be beneficial to space the closest reinforcing structure 68 at a specified distance from the ends 43, 45 of each of the tubes 40. Accordingly, in some embodiments, it may be necessary to remove the dimples 60 from selected portions of the sheet by means of any suitable method such as an ironing process, to ensure that each of the resulting tubes 40 is devoid of the dimples 60 adjacent the ends 43, 45 thereof.
The tubes 40 have been described as having only a single row of the reinforcing structures 68 formed along a centerline A of each of the tubes 40. However, it should be understood that multiple rows of the reinforcing structures 68 may be formed by including additional rows of the dimples 60 that are positioned symmetrically about the line of symmetry in the sheets forming each of the tubes 40. Accordingly, the resulting hollow interior 42 of each of the tubes 40 may include flow channels in addition to the first and second flow channels 71, 72 as well as additional fluid communication channels 80 formed therebetween for providing fluid communication between all regions of the hollow interior 42 of each of the tubes 40.
The first planar portion 111 and the second planar portion 112 meet at a centerline B of the tube 140 equally spaced from each of the first side portion 115 and the second side portion 116. The first planar portion 111 of the tube 140 transitions into a first central portion 121 extending between the first planar portion 111 and the third planar portion 113 of the tube 140. The second planar portion 112 of the tube 140 transitions into a second central portion 122 extending between the second planar portion 112 and the third planar portion 113 of the tube 140. Portions of the first central portion 121 and the second central portion 122 facing each other may substantially abut each other as the first central portion 121 and the second central portion 122 extend to the third planar portion 113 of the tube 140, wherein the first central portion 121 may then bend outward toward the first side portion 115 and the second central portion 122 may then bend outward toward the second side portion 116. Alternatively, the first central portion 121 and the second central portion 122 may include folds of 180 degrees (not shown) formed adjacent the third planar portion 113 to double up each of the central portions 121, 122 for additional strength of the tube 140 along the centerline B. The first central portion 121 and the second central portion 122 combine to form a central reinforcing structure 168 extending along a length of the tube 140.
The first central portion 121 and the second central portion 122 may be coupled to each other using any known coupling method, such as welding or brazing, as non-limiting examples. The coupling means may be applied to the tube 140 along a centerline B where the first planar portion 111 meets the second planar portion 112. The coupling means may also be applied at a junction of the first central portion 121 and the second central portion 122 with the third planar portion 113. If brazing is used, the sheet of material forming each of the tubes 140 may be clad on one or both sides with a braze alloy. The sheet of material may have a base of aluminium and be clad with an aluminium based braze alloy, for example.
The sheet of material forming the B-shaped tube 140 may include two opposing edges, each having at least one slot 150 formed therein, wherein each of the slots 150 is arranged to meet and be aligned with a corresponding slot 150 adjacent the third planar portion 113 when the sheet is formed into the B-shape illustrated in
In use, the first fluid enters each of the tubes 140 and is immediately divided into a first fluid stream in the first flow channel 171 and a second fluid stream in the second flow channel 172 as the first fluid encounters the reinforcing structure 168. The first fluid stream and the second fluid stream are then allowed to recombine when they encounter each of the fluid communication channels 180 formed by the slots 150. This mixing of the first and second fluid streams militates against the formation of substantial temperature gradients between different regions within each of the tubes 140 and especially between the first flow channel 171 and the second flow channel 172. The reinforcing structure 168 also reinforces the central portion of each of the tubes 140 to prevent an outward bowing due to internal pressures within each of the tubes 140.
From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions.
