Patent Application
20200132399
The invention relates to a heat exchanger, and more specifically to a stiffening element configured for increasing a bending stiffness of a header tank of the heat exchanger.
Heat exchangers typically include a centralized plurality of heat exchanger tubes or passageways connected at each respective end thereof to one of an inlet tank and an outlet tank. The plurality of heat exchanger tubes forms a heat exchanger core of the heat exchanger for transferring heat energy between two different heat exchanging fluids. The inlet tank and the outlet tank each typically include a surface that acts as a header having tube openings for receiving end portions of the heat exchanger tubes therein. The header of each of the tanks is then coupled to a casing of the tanks that aids in distributing or collecting a fluid flowing through the heat exchanger tubes.
It is not uncommon for slight temperature variations to exist at different regions within the heat exchanger core as a result of the form and configuration of various components of the heat exchanger such as the tanks, the headers, and the heat exchanger tubes. For example, a first set of the heat exchanger tubes may generally be an elevated temperature when compared to a second set of the heat exchanger tubes. This may occur when there is an unequal distribution of a fluid to an interior of the heat exchanger tubes forming the first and second sets. These variations in temperature can result in the first and second sets of the heat exchanger tubes experiencing different degrees of thermal expansion in the longitudinal direction of each of the tubes. Because each of the tubes is coupled to each of the tanks at the opposing ends thereof, the difference in thermal expansion between the different sets of the tubes can lead to a bending moment forming in one or both of the opposing headers as different regions of the opposing headers are separated to varying degrees with respect to the longitudinal direction of the tubes.
The presence of a bending moment within one of the headers can lead to a bending or flexing of the header. This bending or flexing can lead to an increased stress at a junction of one of the tubes and a corresponding one of the headers. The increased stress can potentially lead to failure at this junction, thereby presenting the possibility of leakage of one of the heat exchanging fluids from the heat exchanger tube.
It would therefore be desirable to produce a heat exchanger having header tanks that resist a bending or flexing thereof in reaction to variations of thermal expansion within a heat exchanger core of the heat exchanger.
Compatible and attuned with the present invention, a stiffening element for a heat exchanger that reinforces a header of the heat exchanger for minimizing a flexing or bending of the header has been surprisingly discovered.
In an embodiment of the invention, a header tank for a heat exchanger comprises a casing having a hollow interior and a header assembly coupled to the casing. The header assembly comprises a header having a plurality of tube openings formed therein and a stiffening element coupled to the header. The stiffening element includes a stiffening wall extending from a first longitudinal side of the header to an opposing second longitudinal side of the header.
In another embodiment of the invention, a heat exchanger comprises a first header tank including a first casing having a hollow interior and a first header assembly coupled to the first casing. The first header assembly comprises a first header having a plurality of first tube openings formed therein and a first stiffening element coupled to the first header. The first stiffening element includes a first stiffening wall extending from a first longitudinal side of the first header to an opposing second longitudinal side of the first header. A second header tank is arranged opposite the first header tank. A plurality of heat exchanger tubes extends longitudinally between the first header tank and the second header tank with one of the heat exchanger tubes received in each of the first tube openings formed in the first header of the first header tank.
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.
The heat exchanger 10 includes a first header tank 12, an oppositely arranged second header tank 14, and a heat exchanger core 16 extending between the first header tank 12 and the second header tank 14. The heat exchanger core 16 is formed by a plurality of spaced apart and parallel heat exchanger tubes 20. The heat exchanger tubes 20 may be any form of heat exchanger tubes, including extruded tubes or folded flat tubes, as non-limiting examples. The heat exchanger core 16 may further include surface area increasing features 18, such as corrugated fins, disposed between adjacent ones of the heat exchanger tubes 20 in order to increase a heat exchange capacity of the heat exchanger 10.
As best shown in
The first casing 30 may include a plurality of longitudinally spaced crimp structures 40 having a substantially semi-cylindrical shape. Each of the crimp structures 40 may be an integrally formed structure projecting from one of the foot segments 33, 34 and a corresponding one of the wall segments 35, 36. Each of the crimp structures 40 may include a substantially semi-circular cross-sectional shape for allowing a corresponding structure to be bent or deformed to match the semi-circular shape of each of the crimp structures 40. The first casing 30 may further include a plurality of spaced apart ribs 42 formed on an outer surface thereof with each of the ribs 42 extending from one of the crimp structures 40 disposed on the first foot segment 33 to an opposing one of the crimp structures 40 disposed on the second foot segment 34. The ribs 42 may be added to the first casing 30 in order to re-inforce the first casing 30 against deformation due to thermal expansion when receiving the first fluid at an elevated pressure therein and other stresses applied to the casing 30.
The first casing 30 includes a first fluid port 44 providing fluid communication between the hollow interior of the first casing 30 and the remainder of a fluid system conveying the first fluid therethrough. The first fluid port 44 may form an inlet or an outlet of the first casing 30 depending on a direction of flow of the first fluid through the heat exchanger 10, and especially in cases where the heat exchanger 10 is configured to be passable bi-directionally to accommodate multiple different modes of operation of the associated fluid system. The first fluid port 44 is shown as a cylindrical conduit intersecting the first casing 30 at a central region thereof with respect to a longitudinal direction of the first casing 30. However, it should be understood that the first fluid port 44 may be disposed at any location on the first casing 30, at any orientation relative to the first casing 30, and can have any shape without departing from the scope of the present invention, including being disposed at or adjacent either of the two longitudinal ends of the first casing 30.
The first casing 30 may be formed from a polymeric material such as a rigid plastic material suitable for withstanding the internal pressure of the first fluid when passing through the first casing 30. The first casing 30 may accordingly be formed in a suitable molding operation, as one non-limiting example. However, it is understood other materials can be used as desired without departing from the scope of the invention.
The first casing 30 may have structure differing from that disclosed herein without departing from the scope of the present invention. More specifically, the first casing 30 may have any suitable structure so long as the first casing 30 defines a hollow interior for passing the first fluid while also including a foot 32 or other structure defining a perimeter of a header opening 31 having a closed shape such as a rectangular, rounded rectangular, or elliptical perimeter shape, as non-limiting examples.
The first header assembly 50 is formed by a first header 52 rigidly and securely coupled to a first stiffening element 70. The first stiffening element 70 is configured to resist a bending of a portion of the first header 52 away from a plane generally defined by the first header 52 when the first header 52 is not subjected to the forces and internal pressures present during operation of the heat exchanger 10. More specifically, the first stiffening element 70 resists a bending of the first header 52 about an axis arranged from one longitudinal side to an opposing longitudinal side of the first header 52, such as may be present when differing degrees of thermal expansion occur between different sets of the heat exchanger tubes 20 forming the heat exchanger core 16 of the heat exchanger 10, as explained in greater detail hereinafter.
The first header 52 of the first header assembly 50 is illustrated in isolation in
The first header 52 further includes a coupling structure in the form of a peripheral rim 58 surrounding the first header wall 54 and defining a perimeter of the first header 52. The peripheral rim 58 may be formed to project both away from a plane of the first header wall 54 and radially outwardly in a manner forming a substantially concave surface 59 having an arcuate cross-sectional shape and extending around the perimeter of the first header 52. In other embodiments, the peripheral rim 58 may be devoid of an outwardly flared portion to cause the peripheral rim 58 to extend primarily in a direction perpendicular to the plane of the first header wall 54. For example, a dashed line 4 illustrated in
The peripheral rim 58 of the first header 52 may further include a pair of first coupling tabs 62 at each longitudinal end of the first header 52. Each of the first coupling tabs 62 is formed by a deformable projecting portion of the first header 52 configured for mating with a corresponding coupling structure of the first stiffening element 70, as explained in greater detail hereinafter.
The first header 52 may be formed from a metallic material such as aluminum. The aluminum may be formed to have a thickness providing a desired degree of compliancy to the first header 52, and specifically the first header wall 54, as desired. The first header 52 may be formed of other suitable materials having the desired strength and compliancy without necessarily departing from the scope of the present invention. The first header 52 may be at least partially coated with a suitable brazing material for initiating a brazing operation, as desired.
As best shown in
The frame structure 72 is defined by a frame wall 74 formed into an arcuate cross-sectional shape extending around the periphery of the frame structure 72. The frame wall 74 may be substantially U-shaped in cross-section, for example. The U-shaped cross-sectional shape results in the frame wall 74 including a concave surface 75 and an oppositely arranged convex surface 76. The concave surface 75 of the frame wall 74 forms a trough configured to receive the foot 32 of the first casing 30 therein when coupling the first casing 30 to the first header assembly 50 while the convex surface 76 is configured to engage the peripheral rim 58 of the first header 52 about a perimeter thereof. As can be seen in
A laterally outward portion of the frame wall 74 extending along each longitudinal side of the frame structure 72 may form a crimp strip 77 for crimping the first header assembly 50 to the first casing 30. The crimp strip 77 may form an outwardly extending tab having a plurality of longitudinally spaced apertures 78 formed therein. The apertures 78 may be added to the crimp strip 77 for rendering the crimp strip 77 more compliant when deforming the crimp strip 77 toward the foot 32 during a crimping process. Each of the portions of the crimp strip 77 disposed intermediate an adjacent pair of the apertures 78 may be deformed to substantially correspond to the semi-circular shape of each of the crimp structures 40 of the first casing 30 when crimping the first header assembly 50 to the first casing 30. Concurrently, each of the portions of the crimp strip 77 aligned with one of the apertures 78 thereof may be inwardly deformed to contact one of the wall segments 35, 36 of the first casing 30, thereby creating a corrugated profile of the crimp strip 77 forming an interference pattern with respect to the foot 32 of the first casing 30, thereby preventing removal of the first stiffening element 70 from the first casing 30. The crimp strip 77 may include an outwardly flared portion 79 to facilitate entry of the foot 32 of the first casing 30 therein.
The frame structure 72 may further include a pair of first coupling clips 82 at each longitudinal end thereof. Each of the first coupling clips 82 may be formed as a deformable strip of material bent to form a wedge shape between two legs of the strip of material. The wedge shape of each of the first coupling clips 82 may be configured to receive a portion of each of the first coupling tabs 62 of the first header 52 therein to further couple the first header 52 to the frame structure 72, wherein each of the first coupling clips 82 may be further deformed to maintain a position of each of the first coupling tabs 62 when received therein.
The stiffening wall 84 extends from one longitudinal side of the frame structure 72 to an opposing longitudinal side of the frame structure 72 while also extending in a longitudinal direction of the first stiffening element 70 with the opposing ends of the stiffening wall 84 spaced from each of the opposing ends of the frame structure 72. As best shown in
More specifically, the stiffening wall 84 is shown in
The stiffening wall 84 further includes a plurality of flow openings 92 formed therein. The flow openings 92 may be formed in any of the first lateral portion 87, the second lateral portion 88, or the central portion 89 of the stiffening wall 84. Each of the flow openings 92 provides fluid communication between a first chamber 101 formed by the cooperation of the first casing 30 and the convex outer surface 86 of the stiffening wall 84 and a second chamber 102 formed by the cooperation of the stiffening wall 84 and the first header 52. The first chamber 101 is in direct fluid communication with the first fluid port 44 while the second chamber 102 is in direct fluid communication with each of the heat exchanger tubes 20 extending through the first header wall 54.
As shown in
The first stiffening element 70 is shown in
The first stiffening element 70 may be formed from a metallic material such as aluminum. If not formed from the same material as the first header 52, the first stiffening element 70 may instead be formed from a complimentary material configured for joining to the material forming the first header 52 during an aggressive joining method, such as brazing, welding, or soldering, as non-limiting examples. The first stiffening element 70 may accordingly be at least partially coated with a suitable brazing material for initiating a brazing operation, as desired.
As shown in
The second header tank 14 may include substantially the same structure as the first header tank 12, including a second header assembly 150 formed by the cooperation of a second header 152 and a second stiffening element 170 and a second casing 130 forming a manifold for distributing or recombining the first fluid passed by the heat exchanger 10. The second casing 130 may include a second fluid port 144 forming an inlet or outlet into the second casing 130. As such, discussion of the specific structure of the second header tank 14 is omitted herein. Additionally, it should be understood that the heat exchanger 10 may be formed with only one of the header tanks 12, 14 thereof having the structure disclosed herein without necessarily departing from the scope of the present invention.
With reference to
First, the first header 52 may be received in the frame structure 72 of the first stiffening element 70 by placing the concave surface 59 of the peripheral rim 58 of the first header 52 in abutment with the convex surface 86 of the frame wall 74 of the first stiffening element 70. Once properly aligned, each of the first coupling tabs 62 of the first header 52 may be deformed into a corresponding one of the first coupling clips 82 to form a mechanical connection between the first header 52 and the first stiffening element 70. The second header 152 and the second stiffening element 170 of the second header tank 14 may also be mechanically joined to each other in similar fashion to that described with reference to the first header tank 12 to form a second header assembly 150 opposite the first header assembly 50.
The heat exchanger tubes 20 may be simultaneously arranged in parallel and spaced apart from each other to receive the surface area increasing features 18 between adjacent ones of the heat exchanger tubes 20. Once properly aligned into the form of the heat exchanger core 16, the end portions of each of the heat exchanger tubes 20 are received into each of the corresponding tube openings 55 of each of the first header 52 and the second header 152.
The assembly process next includes the steps of securely coupling the first header 52 to the first stiffening element 70 to form a fluid-tight first header assembly 50, securely coupling the second header 152 to the second stiffening element 170 to form a fluid-tight second header assembly 150, securely coupling the first header 52 to an end portion of each of the heat exchanger tubes 20, and securely coupling the second header 152 to an opposing end portion of each of the heat exchanger tubes 20. Each of the aforementioned coupling steps may occur simultaneously or in any desired order. The secure couplings may be formed by any suitable aggressive joining method, including soldering, brazing, or welding, as desired. As explained throughout, one particularly suitable manufacturing method may include simultaneously joining each of the aforementioned components using a single brazing process when each of the components are properly arranged to allow a corresponding brazing material to flow into each desired joint, thereby eliminating additional manufacturing steps to simplify construction of the resulting heat exchanger 10.
The secure coupling of the first header 52 to the first stiffening element 70 includes the first header 52 securely coupled to the frame structure 72 of the first stiffening element 70 about an entirety of a perimeter of the peripheral rim 58 to avoid any potential fluid leaks from the resulting first header assembly 50. The second header 152 is similarly joined to the second stiffening element 170 about a perimeter thereof to prevent any leaks from the resulting second header tank 14.
The resulting assembly including the first header assembly 50, the heat exchanger core 16, and the second header assembly 150 is then ready to be coupled to each of the first header tank 12 and the second header tank 14. With specific reference to the first header tank 12, the foot 32 of the first casing 30 is received into the concave surface 75 formed by the frame wall 74 about a perimeter of the first header assembly 50 with the peripheral seal 99 disposed therebetween. The crimp strip 77 projecting from the frame wall 74 is then deformed inwardly to extend at least partially over a shoulder 39 of the foot 32 to couple the frame structure 72 of the first stiffening element 70 to the first casing 30 while compressing the peripheral seal 99 between the foot 32 and the frame wall 74 to fluidly seal the joint formed between the first casing 30 and the first header assembly 50. The second header tank 14 is joined to the second header assembly 150 using the same process as disclosed above with reference to the first header tank 12.
In use, the first fluid enters the first header tank 12 through the first fluid port 44 thereof. The first fluid then enters the first chamber 101 of the first header tank 12 formed on the convex side of the stiffening wall 84. The size, shape, and positioning of each of the flow opening 92 within the stiffening wall 84 determines a distribution of the first fluid when entering the second chamber 102, and hence a distribution of the first fluid to each of the heat exchanger tubes 20 in fluid communication with the second chamber 102 formed on the concave side of the stiffening wall 84. The first fluid is then able to traverse each of the heat exchanger tubes 20 before entering a corresponding second chamber (not shown) of the second header tank 14 disposed between the second header 152 and the second stiffening element 170. The first fluid is then able to flow from the second chamber and into a first chamber (not shown) disposed between the second stiffening element and a wall of the second casing 130 via a plurality of the openings formed in the second stiffening element. The first fluid then recombines within the second chamber before exiting the second casing 130 through the second fluid port 144 thereof.
The disclosed heat exchanger 10 advantageously prevents a failure of the first header 52 by preventing deformation of the first header 52 in response to an occurrence of unequal thermal expansion between different ones of the heat exchanger tubes 20 when traversed by the first fluid. More specifically, the addition of the first stiffening element 70 to the first header 52 when constructing the first header assembly 50 results in an area moment of inertia of the resulting first header assembly 50 that is greater than an area moment of inertia of the first header 52 in the absence of the first stiffening element 70. An area moment of inertia for a given cross-section describes a capacity for the given cross-section to resist bending with respect to a reference axis. The area moment of inertia for the given cross-section is increased when the area occupied by the cross-section in question is disposed at an increased distance from an associated reference axis. In the given circumstance, the reference axis may be an axis extending in the width or lateral direction of the first header 52 while arranged on a plane generally defined by the longitudinal direction and the width direction of the first header 52. The reference axis accordingly extends perpendicular to each of a longitudinal direction of each of the heat exchanger tubes 20 and the longitudinal direction of the first header 52.
The inclusion of a specified pattern of the flow openings 92 in the stiffening wall 84 also aids in preventing an incidence of unequal thermal expansion within the heat exchanger tubes 20 by distributing the first fluid to each of the heat exchanger tubes 20 in a prescribed manner. The flow openings 92 may be positioned to cause the first fluid to flow substantially evenly to each of the heat exchanger tubes 20 by controlling the flow area through each region of each of the header tanks 12, 14. Such a feature may be utilized to reduce an incidence of unequal flow rate of the first fluid or an unequal pressure drop of the first fluid when flowing through specific portions of each of the header tanks 12, 14.
The heat exchanger 10 having the first stiffening element 70 is further improved by allowing for the first header wall 54 of the first header 52 to be formed with a decreased thickness in comparison to the header of a similar heat exchanger devoid of the first stiffening element 70 due to the increased stiffness provided by the first stiffening element 70. The decreased thickness of the first header wall 54 allows for the first header wall 54 to be more compliant and flexible with respect to a localized area, which can aid in accommodating a deformation of the first header wall 54 or one of the heat exchanger tubes 20 at the localized area during operation of the heat exchanger 10. For example, one of the heat exchanger tubes 20 experiencing an elevated degree of thermal expansion in comparison to an adjacent one of the heat exchanger tubes 20 may allow for the first header wall 54 to deform slightly adjacent the corresponding tube opening 55 receiving the thermally elevated heat exchanger tube 20 to accommodate the deformation of the thermally elevated heat exchanger tube 20. However, the increased stiffness provided by the first stiffening element 70 prevents a major portion of the first header wall 54 from deviating from a plane generally defined by the first header wall 54, thereby preventing a failure at or adjacent the corresponding tube opening 55 despite the slight degree of localized deformation allowed by the compliancy of the first header wall 54 having the reduced thickness.
The stiffening wall 84 of the first stiffening element 70 is arranged to extend a desired distance from a plane generally defined by the width direction and the longitudinal direction of the first header wall 54 of the first header 52 in order to achieve a desired area moment of inertia of the stiffening wall 84 from the perspective of the cross-section of
The stiffening wall 84 is not limited to the substantially trapezoidal cross-sectional shape illustrated in
For example,
It should also be understood that the benefits of the disclosed first stiffening element 70 may also be utilized while substantially reversing the configuration of the first header 52 and the first stiffening element 70 with respect to a method of coupling the resulting header assembly to the first casing 30. For example,
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.
