FIELD OF THE INVENTION
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The present invention relates to a heat exchanger and a method of manufacturing a heat exchanger.
SUMMARY
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Tube and insert type exhaust gas recirculation ("EGR") coolers are commonly subjected to high tube stresses caused by extreme thermal gradients, repeated transient events, and/or rigid tube to header joints. Moreover, future EGR coolers will be required to handle increased thermally induced stresses.
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Current heat exchanger designs also fail to provide for tube expansion caused by non-uniform thermal loading and non-uniform flow distributions. This condition can be more severe in heat exchangers having cores with two or more rows of tubes. In these constructions, a number of different failures, such as, for example, cracked headers, can be caused by non-uniform thermal loading and/or non-uniform flow distributions.
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Among other things, the present invention can remove the guesswork from EGR cooler design by allowing each tube in a heat exchanger to expand freely and independently of the other tubes, thereby making load sharing between adjacent tubes a non-issue and relieving tube stress caused by flexing of adjacent tubes and/or flexing of the heat exchanger casing. The present invention can also or alternatively provide a header of a heat exchanger having significantly reduced loading, thereby enabling the use of two-row heat exchanger cores without causing header cracking.
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In some embodiments, the present invention provides an elastic region including a beaded elastic sleeve positioned between a header and each tube in a heat exchanger core. The elastic sleeve can allow each tube to expand independently of the other tubes, thereby maintaining stresses below critical levels.
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The present invention also provides a method of hydro-forming a series of beaded expansion joints from an elongated tube. A number of individual sleeves can then be cut from the tube.
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The present invention also provides an elastic sleeve, which can establish a header-to-header length of a heat exchanger. In this manner, the elastic sleeve can assist with core assembly. Alternatively or in addition, beads located along the elastic sleeve can provide positive stops for the header to assist with core assembly.
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In some embodiments, the present invention provides a method of assembling a heat exchanger using current fabricating processes. In some embodiments, at least portions of the heat exchanger of the present invention can be compatible with other components of existing heat exchanger designs, such as, for example, existing housing and header components.
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The present invention also provides an expansion bead or bellows formed integrally with a heat exchanger tube. In some embodiments, the bead or bellows can be formed adjacent to a tube end. In other embodiments, the bead or bellows can be strategically placed along the tube length.
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In some embodiments, the present invention provides a heat exchanger tube including a series of expansion regions, which can act together as a spring. The expansion regions can include expansion beads, which can act as baffles to direct fluid flow through the heat exchanger. These expansion beads can eliminate the need for additional parts. In some embodiments, the beads can be used to assist with heat exchanger core assembly because the beads can act as positive stops for the header.
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The present invention also provides a heat exchanger including a header, a number of tubes extending outwardly from the header, and an elastic sleeve supported between the header and one of the tubes to allow movement of the tube relative to the header in a direction substantially parallel to a length of the tube defined between a first end of the tube adjacent to the header and a second end of the tube spaced away from the header. Together, the tube, the header, and the elastic sleeve can at least partially define a flow path for a working fluid.
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In some embodiments, the present invention provides a heat exchanger including a header and a number of tubes extending outwardly from the header. Each of the tubes can be independently moveable relative to the header in a direction substantially parallel to a length of one of tubes defined between a first end of the tube adjacent to the header and a second end of the tube spaced away from the header. The tubes can be sealed to the header such that together the header and the tubes define a flow path for a working fluid.
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In some embodiments, the present invention provides a heat exchanger including a header and a tube extending outwardly from the header. Together with the header, the tube can define a flow path for a working fluid. The tube can have a first end secured to the header, a second end spaced from the header, and a number of elastic regions spaced along a length of the tube between the first end and the second end.
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The present invention also provides a method of assembling a heat exchanger including a header and a number of outwardly extending tubes. The method can include the acts of forming an elastic sleeve and securing the elastic sleeve between the header and one of the tubes such that the tube is moveable independently relative to the header and another of the tubes in a direction substantially parallel to a length of the other tube and such that together the header, the elastic sleeve, and the tube define a flow path for a working fluid.
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Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
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- Fig. 1 is a partially broken, perspective view of a heat exchanger according to some embodiments of the present invention.
- Fig. 2 is an exploded perspective view of the heat exchanger shown in Fig. 1.
- Fig. 3 is a top view of the heat exchanger shown in Fig. 1.
- Fig. 4 is a side view of an elongated elastic sleeve for a heat exchanger manufactured according to some embodiments of the present invention.
- Fig. 5 is a perspective view of the elongated sleeve shown in Fig. 4.
- Fig. 6 is a broken, perspective view of a heat exchanger including tubes having elastic regions according to some embodiments of the present invention.
- Fig. 7 is a cross-sectional view of the heat exchanger shown in Fig. 6.
- Fig. 8 is another cross-sectional view of a portion of the heat exchanger shown in Fig. 6.
- Fig. 9 is a perspective view of a tube and an elastic sleeve of the heat exchanger shown in Fig. 6.
- Fig. 10 is a broken, perspective view of a heat exchanger according to some embodiments of the present invention.
- Fig. 11 is an enlarged cross-sectional view of a portion of the heat exchanger shown in Fig. 10.
- Fig. 12 is a perspective view of a heat exchanger having a valve and elastic regions according to some embodiments of the present invention.
- Fig. 13 is a partially broken view of the heat exchanger shown in Fig. 12 and showing the valve in an opened position.
- Fig. 14 is a partially broken view of the heat exchanger shown in Fig. 12 and showing the valve in a closed position.
- Fig. 15 is a partially broken, perspective view of a heat exchanger according to some embodiments of the present invention.
- Fig. 16 is a cross-sectional view of a portion of the heat exchanger shown in Fig. 15.
DETAILED DESCRIPTION
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Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
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Unless specified or limited otherwise, the terms "mounted," "connected," "supported," and "coupled" and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, "connected" and "coupled" are not restricted to physical or mechanical connections or couplings.
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Also, it is to be understood that phraseology and terminology used herein with reference to device or element orientation (such as, for example, terms like "central," "upper," "lower," "front," "rear," and the like) are only used to simplify description of the present invention, and do not alone indicate or imply that the device or element referred to must have a particular orientation. In addition, terms such as "first" and "second" are used herein for purposes of description and are not intended to indicate or imply relative importance or significance.
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Figs. 1-3 illustrate a heat exchanger 8 according to some embodiments of the present invention. In some embodiments, including the illustrated embodiment of Figs. 1-3, the heat exchanger 8 can operate as an exhaust gas recirculation ("EGR") heat exchanger and can be operated with the exhaust system of a motor vehicle. In other embodiments, the heat exchanger 8 can be used in other (e.g., non-vehicular) applications. In addition, it should be appreciated that the heat exchanger 8 of the present invention can take many forms, utilize a wide range of materials, and can be incorporated into various other systems.
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During operation and as explained in greater detail below, the heat exchanger 8 can transfer heat energy from a high temperature first working fluid (e.g., exhaust gas, water, engine coolant, CO2, an organic refrigerant, R12, R245fa, air, and the like) to a lower temperature second working fluid (e.g., exhaust gas, water, engine coolant, CO2, an organic refrigerant, R12, R245fa, air, and the like).
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The heat exchanger 8 can include one or more headers 18 positioned at one or both ends of a stack of heat exchanger tubes 11. The stack of tubes 11 can at least partially define a heat exchanger core 10. In the illustrated embodiment of Figs. 1-3, the heat exchanger core 10 includes three tubes 11, each of which has a substantially oval cross-sectional shape. In other embodiments, the heat exchanger core 10 can include one, two, four, five, six, or more tubes 11, each of which can have a triangular, circular, square or other polygonal, or irregular cross-sectional shape.
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As shown in Figs. 1-3, each of the tubes 11 can be secured to the header(s) 18 such that the first working fluid flowing through the heat exchanger core 10 is maintained separate from the second working fluid flowing through the heat exchanger core 10. More specifically, the heat exchanger core 10 defines a first flow path for the first working fluid and a second flow path for a second working fluid, and the first and second flow paths are separated such that the first working fluid is prevented from entering the second flow path and such that the second working fluid is prevented from entering the first flow path.
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In some embodiments, such as the illustrated embodiment of Figs. 1-3, the tubes 11 are secured to the header(s) 18 such that the first working fluid enters the tubes 11 through apertures 16 in the header 18 and travels through the tubes 11 along the first flow path. In these embodiments, the tubes 11 can be secured to the header(s) 18 such that the second working fluid is prevented from entering the first flow path.
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Elastic regions 13 including elastic sleeves 15 can be positioned between ends of the tubes 11 and the header(s) 18. In the illustrated embodiment of Figs. 1-3, the elastic sleeves 15 include corrugated surfaces defining expansion beads 14 extending around the elastic sleeves 15 between the ends of the elastic sleeves 15. As shown in Figs. 1-3, the elastic sleeves 15 can all be located at one end of the heat exchanger core 10 (e.g., at an inlet end or an outlet end). In other embodiments, elastic sleeves 15 can be located at both ends (i.e., at inlet and outlet ends) of the heat exchanger core 10, or alternatively, adjacent tubes 11 can include elastic sleeves 15 located at alternating ends of the heat exchanger core 10.
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Ends of the elastic sleeves 15 can be at least partially received in the apertures 16 in the header(s) 18. As shown in Figs. 1-3, the elastic sleeves 15 can include engagement portions 17, which extend through the apertures 16 between opposite sides of the header(s) 18 and engage outwardly extending collars 19 located on opposite sides of the header(s) 18. In other embodiments, the engagement portions 17 of the sleeves 15 can extend through less than the entire width of the header(s) 18. In still other embodiments, outwardly extending collars 19 of the header(s) 18 can be received in openings defined by the engagement portions 17 of the elastic sleeves 15. In yet other embodiments, the engagement portions 17 of the elastic sleeves 15 and the header(s) 18 can include mating protrusions and recesses to form a labyrinth seal between the header(s) 18 and the engagement portions 17 of the elastic sleeves 15.
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As shown in Figs. 1-3, the elastic sleeves 15 can also or alternatively include engagement portions 21, which are engageable with ends of the tubes 11. In the illustrated embodiment of Figs. 1-3, outwardly extending engagement portions 21 of the elastic sleeves 15 are fitted around exterior perimeters of the ends of the tubes 11 to at least partially form a seal between the tubes 11 and the elastic sleeves 15. In other embodiments, the engagement portions 21 can be received in the ends of the tubes 11. In still other embodiments, the engagement portions 21 of the elastic sleeves 15 and the tube ends can include mating protrusions and recesses to form a labyrinth seal between the tube ends and the engagement portions 21 of the elastic sleeves 15. The sleeves 15 can be secured to the header(s) 18 before the tubes 11 are secured to the sleeves 15. In other embodiments, the sleeves 15 can be secured to the tubes 15 before the sleeves 15 are secured to the header 18.
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In some embodiments, the first ends of the sleeves 15 are brazed, welded, and/or soldered to the walls of the header 18 defining the apertures 16 and the second ends of the sleeves 15 are brazed, welded, and/or soldered to tube 11 ends. In some such embodiments, braze alloy can be added to the intersection of each of the tubes 11 and the sleeves 15 and/or the intersection of each of the elastic sleeves 15 and the header(s) 18. While reference is made herein to brazed, welded, and/or soldered connections, in other embodiments, other connectors and connecting methods including, but not limited to, interference fits, cohesive and adhesive bonding materials, friction fits, and the like can also or alternatively be used to secure the sleeves 15 to the header(s) 18 and the tubes 11.
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The elastic sleeves 15 of the elastic regions 13 reduce the tube 11 and header 18 stresses by absorbing non-uniform loading caused by thermal expansion of the tubes 11, which may or may not be uniform between the different tubes 11 or across a single tube 11. The elastic sleeves 15 of the elastic regions 13 can also or alternatively absorb and/or compensate for bending stresses experienced by each of the tubes 11. For example, in some embodiments, the elasticity provided by the elastic sleeves 15 of the elastic regions 13 allows each tube 11 to move independently relative to a header 18 and in a direction substantially parallel to a length L of each tube 11 to accommodate non-uniform loading caused by thermal expansion of the tubes 11. In some embodiments, elasticity provided by the elastic sleeves 15 of the elastic regions 13 can also or alternatively allow each of the tubes 11 to move independently relative to a header 18 and in a direction substantially normal to the length L of each tube 11 so that, for example, a top side of each tube 11 is moved more closely to the header 18 than a bottom side of the tube 11. Alternatively or in addition, the heat exchanger core 10 or a substantial portion of the core 10 (e.g., two or more tubes 11) can move together relative to a header 18 in a direction substantially parallel to a length L of one of the tubes 11 and/or in a direction substantially normal to the length L of one of the tubes 11 so that, for example, a top side of the core 10 is moved more closely to the header 18 than a bottom side of the core 10.
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Alternatively or in addition, the elastic sleeves 15 of the elastic regions 13 can simplify assembly of the heat exchanger 8 by allowing tubes 11 of different lengths to be assembled together in a single heat exchanger core 10. In some embodiments, portions of the elastic sleeves 15, such as, for example, the expansion beads 14, can act as an assembly stop to simplify and/or improve assembly of the heat exchanger core 10.
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With reference to Figs. 4 and 5, in some embodiments, the sleeves 15 can be formed by hydro-forming a length of elongated tube 23. In these embodiments, the formed tube 23 can be cut at predetermined locations 22 to form individual sleeves 15 from the tube 23.
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In other embodiments, two-piece sleeves 15 can be formed from substantially flat stock that is stamped, rolled, or shaped in another manner to form a first sleeve part (e.g., a first half) of a sleeve 15. A second sleeve part (e.g., a second half) of the sleeve 15 can also or alternatively be stamped, rolled, or otherwise shaped from the substantially flat stock. The two sleeve parts can then be mated together and brazed, welded, or soldered together to provide a single sleeve 15.
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In some such embodiments, the first and second sleeve parts can be formed as mirror images of one another. In other embodiments, the first and second sleeve parts can have different relative sizes, shapes and configurations such that one sleeve part can be at least partially nested inside the other sleeve part. In still other embodiments, the sleeves 15 can be formed from three or more sleeve parts, which can be similarly or differently sized. In yet other embodiments, an elastic region 13 can include two or more elastic sleeves 15, each of which can include one, two, or three sleeve parts. While reference is made herein to brazed, welded, and/or soldered connections, in other embodiments, other connectors and connecting methods including, but not limited to, interference fits, cohesive and adhesive bonding materials, friction fits, and the like can also or alternatively be used to secure the sleeves pieces together.
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Figs. 6-9 illustrate an alternate embodiment of a heat exchanger 108 according to the present invention. The heat exchanger 108 shown in Figs. 6-9 is similar in many ways to the illustrated embodiments of Figs. 1-5 described above. Accordingly, with the exception of mutually inconsistent features and elements between the embodiment of Figs. 6-9 and the embodiments of Figs. 1-5, reference is hereby made to the description above accompanying the embodiments of Figs. 1-5 for a more complete description of the features and elements (and the alternatives to the features and elements) of the embodiment of Figs. 6-9. Features and elements in the embodiment of Figs. 6-9 corresponding to features and elements in the embodiments of Figs. 1-5 are numbered in the 100 series.
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In the illustrated embodiment of Figs. 6-9, the heat exchanger 108 includes a heat exchanger core 110 having tubes 111 extending between headers 118. As shown in Figs. 6-9, elastic regions 113 can be integrally formed along the tubes 111. For example, in some embodiments, elastic regions 113 including elastic sleeves 115 can be integrally formed with the tubes 111 and can be spaced along the length of each of the tubes 111. In some embodiments, the elastic regions 113 can include expansion beads 114 and can be located adjacent to one or both of the ends of each tube 111 and adjacent to the header(s) 118. Alternatively or in addition, as shown in Figs. 6-9, elastic regions 113 including expansion beads 114 can be located along the length of the tubes 111 between the ends of the tubes 111.
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The elastic regions 113 reduce tube 111 and header 118 stresses by absorbing non-uniform loading caused by thermal expansion of the tubes 111, which may or may not be uniform between the different tubes 111 of the heat exchanger core 110. The elastic regions 113 can also or alternatively absorb and/or compensate for bending stresses experienced by each of the tubes 111. Alternatively or in addition, the elastic regions 113 can simplify assembly of the heat exchanger 108 by allowing tubes 111 of differently lengths to be assembled together in a single heat exchanger core 110. In some embodiments, portions of the elastic regions 113, such as, for example, the expansion beads 114, can act as an assembly stop to simplify and/or improve assembly of the heat exchanger core 110. Moreover, the elastic regions 113 of the present invention can be incorporated into existing heat exchanger designs without requiring changes to other components, such as, for example, to the heat exchanger housing 142 and/or with minimal changes to the assembly lines and equipment used for assembly.
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In some embodiments, at least some of the beads 114 can be formed by hydro-forming. Alternatively or in addition, at least some of the beads 114 can be formed by bulge-forming using elastomeric materials. In some such embodiments, rubber plugs and/or rigid (e.g., steel) dies can also or alternatively be used.
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In some embodiments, such as the illustrated embodiment of Figs. 6-9, the beads 114 can be formed along the tubes 111 by stretching, and, consequently thinning the tube walls. In some such embodiments, the thinned tube walls and/or the thinned portions of the tube walls are less rigid and are therefore more flexible than other portions of the tubes 11. In the illustrated embodiment of Figs. 6-9, the wall thickness of each of the tubes 111 is smaller in the elastic regions 113 than at other locations along the length L of each tube 111.
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With reference to Figs. 6-9, the beads 114 can also or alternatively operate as baffles to direct the flow (identified by arrows A in Fig. 6) of working fluid through the heat exchanger core 110, thereby at least partially eliminating the need for additional inserts or elements. In some embodiments, the beads 114 can also or alternatively cooperate with inwardly extending beads 140 formed along the outer housing 142 of the heat exchanger 108 to direct the flow A of working fluid through the heat exchanger core 108.
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In the illustrated embodiment, the beads 140 extend around only a portion of the perimeter of the outer housing 142, as best seen in Figs. 6 and 7. In addition, the beads 140 can be interrupted, (not shown) so that some of the coolant can by-pass at any point along the tube depth, thereby reducing the dead area normally associated with baffled type, cross flow heat exchangers.
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Figs. 10 and 11 illustrate an alternate embodiment of a heat exchanger 208 according to the present invention. The heat exchanger 208 shown in Figs. 10 and 11 is similar in many ways to the illustrated embodiments of Figs. 1-9 described above. Accordingly, with the exception of mutually inconsistent features and elements between the embodiment of Figs. 10 and 11 and the embodiments of Figs. 1-9, reference is hereby made to the description above accompanying the embodiments of Figs. 1-9 for a more complete description of the features and elements (and the alternatives to the features and elements) of the embodiment of Figs. 10 and 11. Features and elements in the embodiment of Figs. 10 and 11 corresponding to features and elements in the embodiments of Figs. 1-9 are numbered in the 200 series.
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As shown in Figs. 10 and 11, the heat exchanger 208 can include elastic sleeves 215 located at opposite ends of each of the tubes 211. Each of the elastic sleeves 215 can include first and second members 252, 254, which can be secured together (e.g., brazed, welded, or soldered) to at least partially define an expansion joint at each end of each tube 211. In the illustrated embodiment of Figs. 10 and 11, the elastic sleeves 215 each can include a number of pairs of first and second members 252, 254 assembled together such that a protrusion or rib 256 extending outwardly from one first member 252 is received in a correspondingly shaped opening in an adjacent second member 254 to provide a seal between the adjacent pairs of first and second members 252, 254 and to allow relative movement between the pairs of first and second members 252, 254.
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Figs. 12-14 illustrate an alternate embodiment of a heat exchanger 308 according to the present invention. The heat exchanger 308 shown in Figs. 12-14 is similar in many ways to the illustrated embodiments of Figs. 1-11 described above. Accordingly, with the exception of mutually inconsistent features and elements between the embodiment of Figs. 12-14 and the embodiments of Figs. 1-11, reference is hereby made to the description above accompanying the embodiments of Figs. 1-11 for a more complete description of the features and elements (and the alternatives to the features and elements) of the embodiment of Figs. 12-14. Features and elements in the embodiment of Figs. 12-14 corresponding to features and elements in the embodiments of Figs. 1-11 are numbered in the 300 series.
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As shown in Figs. 12-14, the heat exchanger 308 can include a heat exchanger core 310 having tubes 311 extending between headers 318. At least one of the headers 318 can be secured to a tank 362 to at least partially enclose an interior space. Elastic regions 313 including elastic sleeves 315 can be positioned between the ends of the tubes 311 and the headers 318.
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The heat exchanger 308 can include a flow control or bypass valve 360. In the illustrated embodiment of Figs. 12-14, the valve 360 is positioned in one of the tanks 362 adjacent to a header 318 and includes a valve member 358. The valve member 358 is supported in the tank 362 for movement relative to ends of the tubes 311 and the header 318 between a closed position (shown in Fig. 14), in which the valve member 358 prevents flow to or substantially obstructs the flow of working fluid (e.g., exhaust gas) from the tank 362 to one or more tube ends, and an opened position (shown in Fig. 13), in which the valve member 358 is moved away from the tube ends such that flow between the tank 362 and the tube ends is substantially unobstructed. In some embodiments, the valve member 358 is moveable relative to the ends of the tubes 311 and the header 318 between a number of intermediate positions to further regulate and/or control the flow of working fluid into at least on of the tube ends.
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As shown in Figs. 12-14, when the valve member 358 is in the opened position, the valve member 358 is substantially parallel to a length L of the tubes 311, and when the valve member 358 is in the closed position, the valve member 358 is substantially perpendicular to the length L of the tubes 311. In embodiments in which the valve member 358 is moveable toward one or more intermediate positions, the valve member 358 can be oriented at an acute angle with respect to at least some of the tube ends.
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In some embodiments, the valve 360 can include an actuator 364, which extends outwardly from the tank 362 and is engageable by an operator. In these embodiments, an operator can grip the actuator 364 to move the valve member 358 between the opened and closed positions. In other embodiments, the valve 360 can be controlled remotely and can also or alternatively be controlled by an electronic controller.
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In embodiments having a valve 360, the mass flow rate of the working fluid traveling through the tubes 311 can be adjusted by moving the valve member 358 between the opened and closed positions. For example, when the valve member 358 is moved toward the closed position, working fluid is prevented from entering at least one of the tubes 311 and/or the flow of the working fluid to at least one of the tubes 311 is restricted. In this manner, the mass flow rate of working fluid traveling through the remaining tubes 311 can be increased. As best seen in Fig. 14, this can cause differential thermal expansion between tubes 311 that are receiving the working fluid and the tubes 311 that are not receiving the working fluid or are receiving a restricted flow of working fluid. In some such embodiments, the elastic sleeves 315 can expand and contract to accommodate the different thermal expansion rates between the tubes 311.
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Figs. 15 and 16 illustrate an alternate embodiment of a heat exchanger 408 according to the present invention. The heat exchanger 408 shown in Figs. 15 and 16 is similar in many ways to the illustrated embodiments of Figs. 1-14 described above. Accordingly, with the exception of mutually inconsistent features and elements between the embodiment of Figs. 15 and 16 and the embodiments of Figs. 1-14, reference is hereby made to the description above accompanying the embodiments of Figs. 1-14 for a more complete description of the features and elements (and the alternatives to the features and elements) of the embodiment of Figs. 15 and 16. Features and elements in the embodiment of Figs. 15 and 16 corresponding to features and elements in the embodiments of Figs. 1-14 are numbered in the 400 series.
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As shown in Figs. 15 and 16, the heat exchanger 408 can include a valve 460 having a valve member 458 supported in a tank 462 for movement between a closed position (shown in Figs. 15 and 16), in which the valve member 458 prevents flow to at least a portion of each of the tubes 411 or substantially obstructs the flow of working fluid from the tank 462 to one or more tube ends, and an opened position (not shown), in which the valve member 458 is moved away from the tube ends such that flow between the tank 462 and the tube ends is substantially unobstructed.
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In the illustrated embodiment of Figs. 15 and 16, the valve member 458 extends across substantially the entire tank 462 such that, when the valve member 458 is in the closed position, the valve member 458 prevents flow to at least a portion of each of the tubes 411 or substantially obstructs the flow of working fluid from the tank 462 to all of the tube ends. In other embodiments, the valve member 458 can extend through less than the entire tank 462 such that, when the valve member 458 is in the closed position, the valve member 458 prevents flow to at least a portion of less than all of the tubes 411 or substantially obstructs the flow of working fluid from the tank 462 to less than all of the tubes 411.
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As shown in Figs. 15 and 16, the valve member 458 can be sized such that, when the valve member 458 is in the closed position, the valve member 458 closes or obstructs approximately one-half of each of the tube ends. In other embodiments, the valve member 458 can have other sizes and configurations such that, when the valve member 458 is in the closed position, the valve member 458 closes or obstructs less than approximately one-half of each of the tube ends. In still other embodiments, the valve member 458 can be sized such that, when the valve member 458 is in the closed position, the valve member 458 closes or obstructs more than approximately one-half of each of the tube ends. In still other embodiments, the valve member 458 can have an irregularly shaped leading edge 466 (e.g., angled with respect to a trailing surface 468) such that, when the valve member 458 in the closed position, the valve member 458 closes or obstructs two or all of the tube ends differently.
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In embodiments, such as the illustrated embodiment of Figs. 15 and 16, in which the valve member 458 is moveable to a closed position in which the valve member closes or obstructs only portions of one or more of the tube ends, different portions of the tubes 411 can experience different thermal expansions. For example, as shown in Figs. 15 and 16, upper sides of the tubes 411 can experience different thermal expansions 411 than lower sides of the tubes 411. As also shown in Figs. 15 and 16, these different thermal expansions can be accommodated by the elastic sleeves 415 of the elastic regions 413 so as to prevent cracking of the tubes 411, the tank 462, and/or the header 418.
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In some embodiments, the heat exchanger 408 can include fins supported in one or more of the tubes 411 and extending between the tube ends or between approximate ends of the tubes 411. In these embodiments, undesirable fin cracking typical of some conventional heat exchangers can be eliminated and/or reduced because the fins are not constrained by the headers 418. Furthermore, the heat exchanger 408 of the present invention allows the fins to be retracted from the header 418 without causing a tube failure, as is common in some conventional heat exchangers, because the elastic sleeves 415 absorb some or all of the axial stresses applied to the tubes 411 and/or the fins. Alternatively or in addition, the fins can be located within the tubes 411 without being secured to one or both of the headers 418.
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The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes are possible.
