1. Field of the Invention
The subject invention relates generally to a heat exchanger and method of fabricating the same, and, more specifically to a heat exchanger of the type including a plurality of refrigerant tubes extending between an inlet header and an outlet for transferring refrigerant from the inlet header to the outlet header.
2. Description of the Prior Art
Due to their high performance, automotive style brazed heat exchangers are being developed for residential air conditioning and heat pump applications. Automotive heat exchangers typically utilize a pair of headers with refrigerant tubes defining fluid passages to interconnect the headers. Residential heat exchangers are typically larger than automotive heat exchangers and generally require headers that are two to five times longer than the typical automotive heat exchangers. In such heat exchangers, uniform refrigerant distribution is necessary for optimal performance. To improve refrigerant distribution, refrigerant conduits can be disposed in the headers. An example of such a heat exchanger is disclosed in U.S. Pat. No. 1,684,083 to S. C. Bloom.
The Bloom patent discloses a first header being at least in part generally cylindrical in cross-section to define a first cavity extending along a first header axis between a pair of first header end portions. A second header defining a second cavity extends along a second header axis between a pair of second header end portions. A plurality of refrigerant tubes each defining a fluid passage extends transversely to the header axes between the headers. The fluid passages of the refrigerant tubes are in fluid communication with the cavities for transferring refrigerant from one of the headers to the other of the headers. A refrigerant conduit having a conduit cross-section being circular is disposed in each of the cavities extending axially along the header axes parallel to the headers. The refrigerant conduits include a plurality of orifices in fluid communication with the corresponding cavities for transferring refrigerant between the refrigerant conduits and the corresponding cavities. One of the headers is an inlet header for receiving liquid refrigerant and the other of the headers is an outlet header for outputting refrigerant vapor. The refrigerant conduit disposed in the inlet header insures a uniform and even distribution of the refrigerant throughout the inlet header while the refrigerant conduit disposed in the outlet header insures only dry gas is withdrawn from the outlet header via the refrigerant conduit by a pump.
A heat exchanger as disclosed by the Bloom patent is typically made by puncturing a generally cylindrical first header defining a first cavity and a generally cylindrical second header defining a second cavity in predetermined spaced intervals axially along each header to define a plurality of header slots spaced axially along each header. A plurality of orifices is produced in a generally cylindrical refrigerant conduit, and the refrigerant conduit is inserted into the first cavity of the first header. The first and second headers are then placed in a stacker headering station fixture, and the headers are pressed onto a plurality of refrigerant tubes each defining a fluid passage to fluidly communicate the cavities of the headers. The refrigerant tubes typically extend through the header slots and into the cavities of the headers.
Inserting a refrigerant conduit into a header without damaging the refrigerant tubes or the refrigerant conduit is often difficult in a residential heat exchanger because of the increased length. To alleviate this problem, heat exchangers including a refrigerant conduit disposed in a header and engaging an interior surface of the header have been produced as an alternative to the coaxial refrigerant conduit. Such heat exchangers provide efficient installation of a refrigerant conduit in a header by spacing the refrigerant conduit from the refrigerant tubes extending into the cavities. However, while such heat exchanger assemblies generally enhance the manufacturability of tube-in-tube heat exchanger assemblies, they generally are not compatible with traditional heat exchanger components and systems. There remains the need for a tube-in-tube heat exchanger assembly providing for efficient installation and which is also compatible with traditional heat exchanger components and systems.
The present invention provides such a heat exchanger assembly improved by the refrigerant conduit including a conduit body portion and at least one conduit end portion interconnected by a conduit transition portion with the conduit body portion being offset from the conduit end portion in the first cavity for spacing the conduit body portion from the refrigerant tubes and for positioning the conduit end portion centrally in the first cavity along the first header end portion.
The invention also provides an improved method of fabricating a heat exchanger including a refrigerant conduit having a conduit body portion and an offset conduit end portion interconnected by a conduit transition portion by offsetting the conduit end portion of the refrigerant conduit from the conduit body portion of the refrigerant conduit before inserting the refrigerant conduit into the first cavity.
Accordingly, the present invention provides efficient installation of a refrigerant conduit in a header and provides a heat exchanger which is also compatible with traditional heat exchanger components and systems. The conduit body portion of the refrigerant conduit is spaced from the refrigerant tubes for efficient installation and the conduit end portion is positioned centrally in the first cavity along the first header end portion to provide a central orifice for the refrigerant in accordance with traditional heat exchanger assemblies.
Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, a heat exchanger assembly 20 for dissipating heat is shown generally.
The heat exchanger assembly 20 comprises a first header 22, generally indicated, having an interior surface 24 and being generally circular in cross-section. The first header 22 extends along a first header axis A1 between a pair of first header end portions 26 to define a first cavity 28. A second header 30 is generally indicated and generally circular in cross-section. The second header 30 extends along a second header axis A2 between a pair of second header end portions 32 to define a second cavity 34. As shown in
Hereinafter, an exemplary embodiment of the heat exchanger assembly 20 is described wherein the first header 22 is an outlet header 22 and the second header 30 is an inlet header 30. However, it is to be understood that in additional embodiments of the heat exchanger assembly 20 the first header 22 is an inlet header and the second header 30 is an outlet header. In the exemplary embodiment, the outlet header 22 further defines the first cavity 28 as an outlet cavity 28 extending along an outlet header axis A1 between a pair of outlet header end portions 26 and the inlet header 30 further defines the second cavity 34 as an inlet cavity 34 extending along an inlet header axis A2 between a pair of inlet header end portions 32. In the exemplary embodiment, the inlet header 30 is for receiving a refrigerant for liquid-to-vapor transformation and the outlet header 22 is for collecting refrigerant vapor.
Each header includes a lanced surface 36 being flat and extending parallel to the corresponding header axis A1, A2 between the corresponding header end portions 26, 32. As shown in
A plurality of refrigerant tubes 42, each having a pair of refrigerant tube ends 44, extends in a spaced and parallel relationship and transversely to the header axes A1, A2 between the headers 22, 30. Each of the refrigerant tubes 42 generally has a rectangular cross-section and defines a fluid passage 46 extending between the refrigerant tube ends 44. In additional embodiments of the assembly 20, the refrigerant tubes 42 have an oval cross-section or a circular cross-section. Each fluid passage 46 is in fluid communication with the cavities 28, 34 for transferring refrigerant from the inlet cavity 34 to the outlet cavity 28. As shown in
In an embodiment of the assembly 20, as shown in
The plurality of cooling fins 52 are disposed between adjacent refrigerant tubes 42 and between each core reinforcement 50 and the next adjacent of the refrigerant tubes 42, as shown in
A refrigerant conduit 54 is generally indicated and preferably has a generally uniform cross-section. In the exemplary embodiment, the refrigerant conduit 54 is disposed in the outlet cavity 28 and extends along the outlet header axis A1. In such an exemplary embodiment, the refrigerant conduit 54 is a collector conduit 54. However, it is to be understood that in additional embodiments, the refrigerant conduit 54 is disposed in the inlet header 30 defining the refrigerant conduit 54 as a distributor conduit. In further embodiments, a refrigerant conduit 54 is disposed in each header 22, 30 as shown in
The collector conduit 54 includes a plurality of orifices 56 in fluid communication with the outlet cavity 28 for transferring the refrigerant vapor from the outlet cavity 28 to the collector conduit 54 to flow the refrigerant vapor along the collector conduit 54. In additional embodiments of the assembly 20 wherein the assembly 20 includes a distributor conduit disposed in the inlet header 30, the distributor conduit includes a plurality of orifices 56 in fluid communication with the inlet cavity 34 for transferring refrigerant from the distributor conduit to the inlet cavity 34.
As shown in
Each of a pair of first end caps 62 is generally indicated and is engaged and hermetically sealed to one of the outlet header end portions 26. At least one of the first end caps 62 defines a first aperture 64 for receiving the collector conduit 54. In the exemplary embodiment, the first end caps 62 are outlet end caps 62 and the first aperture 64 is an outlet aperture 64. The outlet aperture 64 is generally hermetically sealed about the collector conduit 54 as shown in
In an embodiment of the assembly 20, as shown in
In an embodiment of the assembly 20 wherein one of the outlet end caps 62 does not define an outlet aperture 64, the collector conduit 54 is engaged and hermetically sealed to the outlet end cap 62 for sealing the collector conduit 54 about the outlet end cap 62. In such an embodiment, the outlet end cap 62 can include an indentation or a projection or another form of indication for locating the collector conduit 54. In such an embodiment, the outlet end cap 62 can also include a support structure for contacting and supporting the collector conduit 54. In an alternative embodiment of the assembly 20 wherein one of the outlet end caps 62 does not define an outlet aperture 64, the collector conduit 54 is engaged and hermetically sealed about the interior surface 24 of the outlet header 22 instead of being engaged and hermetically sealed to the outlet end cap 62. In another alternative embodiment of such an assembly 20 wherein one of the outlet end caps 62 does not define an outlet aperture 64, the collector conduit 54 is engaged and hermetically sealed with a forming operation instead of being engaged and hermetically sealed to the outlet end cap 62. In another alternative embodiment of such an assembly 20 wherein one of the outlet end caps 62 does not define an outlet aperture 64, as shown in
Each of a pair of second end caps 74 is engaged and hermetically sealed to one of the inlet header end portions 32 with at least one of the second end caps 74 defining a second aperture 76 in fluid communication with the inlet cavity 34. In the exemplary embodiment, the second end caps 74 are inlet end caps 74 and the second aperture 76 is an inlet aperture 76 for receiving the refrigerant. While various configurations of the outlet end caps 62 are described above, it is to be understood that various embodiments of the assembly 20 include the inlet end caps 74 having such configurations. However, it is also to be understood that the inlet and outlet end caps 74, 62 are not limited to the configurations as described above. Any of the various shapes and types of end caps commonly known in the art can be used in conjunction with the assembly 20.
In an embodiment of the assembly 20, an encapsulant 78 is disposed about the collector conduit 54 extending through the outlet aperture 64 as shown in
The heat exchanger assembly 20 is distinguished by the refrigerant conduit 54 including a conduit body portion 80 and at least one conduit end portion 82 interconnected by a conduit transition portion 84 wherein the conduit body portion 80 is offset from the conduit end portion 82 in the outlet cavity 28 to space the conduit body portion 80 from the refrigerant tubes 42 and to provide a central outlet for the refrigerant vapor. The conduit body portion 80 is preferably engaged to the interior surface 24 of the cylindrical first header 22 and the conduit end portion 26, 82 is preferably coaxial with the outlet header axis A1. The offset between the axis the conduit body portion 80 extends along and the axis the conduit end portion 82 extends along is preferably the distance between the interior surface 24 of the outlet header 22 and the conduit end portion 26, 82. The conduit body portion 80 and the conduit transition portion 84 generally extend between the outlet header end portions 26 and the conduit end portion 82 is generally disposed in one of the outlet header end portions 26.
A method for fabricating a heat exchanger assembly 20 including a refrigerant conduit 54 having a conduit body portion 80 and an offset conduit end portion 82 interconnected by a conduit transition portion 84 comprises the steps of cutting a generally cylindrical tube having a generally uniform cross-section to define the refrigerant conduit 54. The refrigerant conduit 54 is generally cut from welded or folded tubing. The refrigerant conduit 54 is generally made of copper or aluminum. The higher strength of copper provides for a refrigerant conduit 54 of a thinner gauge. This in turn allows for a refrigerant conduit 54 having a smaller cross-sectional area for easier insertion into a first header 22.
A plurality of orifices 56 is produced in the refrigerant conduit 54. The orifices 56 are generally produced in the conduit body portion 80 of the refrigerant conduit 54 and are generally punched, drilled, or lanced, or any other method commonly known in the art.
The method includes the step of engaging one of a pair of first end caps 62 to one of a pair of first header end portions 26 of a first header 22 having an interior surface 24 and defining a first cavity 28 and extending along a first header axis A1 to seal the first header 22 about the corresponding first header end portion 26. The first end cap 62 can be an internal or external end cap. An internal first end cap 62 offers a higher burst strength relative to an external first end cap 62 due to a smaller area exposed to the internal refrigerant pressure. An internal first end cap 62 design is preferably generally symmetrical due to forming and space limitations. It is also generally preferable for an internal first end cap 62 and a refrigerant conduit 54 to both be made of copper. It is generally preferable for an external first end cap 62 to be made of aluminum in conjunction with a refrigerant conduit 54 made of either aluminum or copper. The higher coefficient of thermal expansion/contraction of aluminum causes the aluminum to shrink into either an aluminum or a copper refrigerant conduit 54 as the joint cools from the joining operation. Additionally, an external joint between a copper first end cap 62 and an aluminum first header 22 is difficult to shield from corrosion. Corrosion shielding of an aluminum first end cap 62 and copper refrigerant conduit 54 joint can be obtained with an encapsulant 78. However, a higher material gage is required for an aluminum external first end cap 62 relative to the material gage required for an internal first end cap 62 due to the increased pressure area and aluminum material. A dome shaped external first end cap 62 is generally preferred due to higher burst strength and reduced refrigerant conduit 54 and first end cap 62 deformation under pressure.
The first header 22 and a second header 30 defining a second cavity 34 are punctured in predetermined spaced intervals axially along each of the headers 22, 30 to define a plurality of header slots 40 spaced axially along each of the headers 22, 30. In the preferred embodiment, the headers 22, 30 are punctured with a lancing punch to define the header slots 40 to prevent the production of slugs, to provide easier bonding, and to add reinforcement. In additional embodiments, the headers 22, 30 can be drilled or punched to define the header slots 40.
The refrigerant conduit 54 is inserted into the first cavity 28 defined by the first header 22. The refrigerant conduit 54 is generally positioned with one end of the refrigerant conduit 54 abutting the first end cap 62 engaged to the first header end portion 26.
The method preferably includes the step of producing a plurality of support projections 58 spaced from one another and aligned in two rows on the first header 22 and extending into the first cavity 28 to contact the conduit body portion 80 of the refrigerant conduit 54 for positioning the refrigerant conduit 54. In alternative embodiments of the method, the support projections 58 are produced extending into the first cavity 28 and along the first header axis A1. In further embodiments of the assembly 20, the method includes the step of engaging a plurality of clips 60 to the refrigerant conduit 54 before inserting the refrigerant conduit 54 into the first cavity 28 in addition to, or in lieu of, the step of producing a plurality of support projections 58.
A first aperture 64 defined by the other of the pair of first end caps 62 is placed about the conduit end portion 82 of the refrigerant conduit 54. The other of the pair of first end caps 62 is engaged to the other of the pair of first header end portions 26 of the first header 22 to seal the first header 22 about the other of the first header end portions 26. The other of the pair of first end caps 62 can be an internal or external end cap. The method also includes the step of engaging the first aperture 64 of the other of the pair of first end caps 62 to the conduit end portion 82 to seal the other of the pair of first end caps 62 about the conduit end portion 82. In an alternate embodiment of the assembly 20, the other of the pair of first end caps 62 and the refrigerant conduit 54 are combined into a subassembly before inserting the refrigerant conduit 54 into the first cavity 28 defined by the first header 22. Generally, if the other of the pair of first end caps 62 and the refrigerant conduit 54 are composed of aluminum, it is preferable to assemble the other of the pair of first end caps 62 and the refrigerant conduit 54 before inserting the refrigerant conduit 54 into the first cavity 28 defined by the first header 22 so that all joints are formed in the brazing operation. In alternative embodiments of the assembly 20, wherein either the other of the pair of first end caps 62 or the refrigerant conduit 54 are composed of copper, the assembly 20 is preferably brazed before engaging the other of the pair of first end caps 62 and the refrigerant conduit 54. A subsequent joining operation must then be used to join the copper parts to the assembly.
In an embodiment of the method, an encapsulant 78 is disposed about the other of the pair of first end caps 62 and about the conduit end portion 82 for shielding the other of the pair of first end caps 62 and the conduit end portion 82 from corrosion.
The first header 22 and the second header 30 are placed in a stacker headering station fixture and a plurality of cooling fins 52 are interleaved between a plurality of refrigerant tubes 42 to define a fin matrix. The cooling fins 52 can be serpentine fins or any other cooling fins commonly known in the art. The method also preferably includes the step of disposing a pair of core reinforcements 50 outwards of the fin matrix to define a core assembly. The core reinforcements 50 protect the cooling fins 52 and provide structural support. The core assembly 20 is transferred to the stacker headering station and the headers 22, 30 are pressed onto the cooling fin 52 and refrigerant tube 42 matrix with the refrigerant tubes 42 preferably extending through the header slots 40 defined by the headers 22, 30.
The method includes the step of furnace brazing the headers 22, 30 and core assembly 20. The core reinforcements 50 and the refrigerant tubes 42 are brazed to the headers 22, 30 and the cooling fins 52 are brazed to the core reinforcements 50 and the refrigerant tubes 42. In various embodiments of the method of fabricating a heat exchanger assembly 20, the elements of the heat exchanger assembly 20 may consist of different materials depending upon the requirements of the heat exchanger assembly 20. For brazed joints, it is preferred to have an aluminum element over a copper element so that the aluminum will shrink into the copper as the joint cools due to its higher coefficient of thermal expansion. However, an aluminum to copper joint generally must be protected to provide corrosion shielding. This is best done in a controlled heat exchanger manufacturing process, as opposed to the variable environment associated with field installation. Alternatively, the typical brazing temperature of a copper to copper joint is significantly higher than the brazing temperature of a copper to aluminum joint. This protects a pre-brazed copper to copper sub-assembly joint during brazing of a copper to aluminum joint.
The method is distinguished by offsetting the conduit end portion 82 from the conduit body portion 80 before the inserting the refrigerant conduit 54 into the first cavity 28 step. The offset can be produced by forming the refrigerant conduit 54 or by any other method known in the art.
The method is further distinguished by the steps of positioning the conduit body portion 80 between the first header end portions 26 and in engagement with the interior surface 24 of the first header 22 and parallel to and offset from the first header axis A1 after said inserting the refrigerant conduit 54 into the first cavity 28 step for spacing the conduit body portion 80 from the refrigerant tubes 42 and positioning the conduit end portion 82 coaxially along the first header axis A1 in one of the first header end portions 26 after said inserting the refrigerant conduit 54 into the first cavity 28 step for providing a central opening for the refrigerant.
While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
This application claims the benefit of application Ser. No. 61/020,040 filed on Jan. 9, 2008.
Number | Date | Country | |
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61020040 | Jan 2008 | US |