US20100025024A1

US20100025024A1 - Heat exchanger and method

Info

Publication number: US20100025024A1
Application number: US12/521,892
Authority: US
Inventors: Steven P. Meshenky; Dan R. Raduenz
Original assignee: Modine Manufacturing Co
Current assignee: Modine Manufacturing Co
Priority date: 2007-01-23
Filing date: 2008-01-23
Publication date: 2010-02-04
Also published as: BRPI0807410A2; DE112008000114T5; WO2008091918A1; CN101589286A; CN101589286B

Abstract

A heat exchanger including a first flow path for a first working fluid, a second flow path for a second working fluid, a tube at least partially defining one of the first and second flow paths, and a corrugated insert secured to the tube and positioned along the first flow path. A structural deficit is provided at a location on the insert such that structural failures occur at the location in preference to other locations on the insert.

Description

RELATED APPLICATIONS

This application claims priority to U.S. provisional application Ser. No. 60/881,919 filed Jan. 23, 2007.

FIELD OF THE INVENTION

The present invention relates to heat exchangers and, more particularly, to an exhaust gas recirculation cooler, a method of assembling the same, and a method of operating the same.

SUMMARY

In some embodiments, the present invention provides a heat exchanger defining a flow path for a first working fluid and a flow path for a second working fluid, a tube at least partially defining one of the first and second flow paths, and a corrugated insert secured to the tube and positioned along the flow path of the first working fluid. In some embodiments, a structural deficit is provided at a location on the insert so that failures occur at that location.
The present invention also provides a heat exchanger having a header and a tube secured to the header. A corrugated insert can be secured to a surface of the tube and can include a groove formed along at least a portion of a length of the insert and spaced apart from the surface of the tube to which the insert is secured. In some embodiments, the corrugated insert can be secured between two opposing surfaces of the tube and the groove can be formed midway along a height of the insert.
In some embodiments, the present invention provides a heat exchanger having a tube and an insert supported by the tube. The insert can have a corrugated shape with a peak and an adjacent valley and a groove extending along a longitudinal dimension of the insert between the peak and the valley such that structural failures occur at a preferred location between the peak and the valley.
The present invention also provides a method of assembling a heat exchanger including providing a heat exchanger tube and positioning an insert in the tube. The method can also include the steps of connecting the insert to a surface of the tube and forming a structural deficiency along at least a portion of a length of the insert at a maximum distance from a point of connection between the insert and the surface of the tube so that failures occur along the structural deficiency.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a heat exchanger according to some embodiments of the present invention.

FIG. 2 is a partially cut-away view of a portion of the heat exchanger shown in FIG. 1.

FIG. 3 is a perspective view of a portion of a tube of the heat exchanger shown in FIG. 1.

FIG. 4 is an exploded view of a portion of a tube and an insert of the heat exchanger shown in FIG. 1.

FIG. 5 is an end view of a portion of a tube and an insert of the heat exchanger shown in FIG. 1.

FIG. 6 is an exploded view of a tube and an insert of a heat exchanger according to another embodiment of the present invention.

FIG. 7 is an end view of a portion of a tube and an insert of the heat exchanger shown in FIG. 6.

DETAILED DESCRIPTION

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.
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.
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.
FIGS. 1-5 illustrate a heat exchanger 10 according to some embodiments of the present invention. In some embodiments, including the illustrated embodiment of FIGS. 1-5, the heat exchanger 10 can operate as an exhaust gas recirculation cooler (EGRC) and can be operated with the exhaust system of a vehicle. In other embodiments, the heat exchanger 10 can be used in other (e.g., non-vehicular) applications, such as, for example, in electronics cooling, industrial equipment, building heating and air-conditioning, and the like. In addition, it should be appreciated that the heat exchanger 10 of the present invention can take many forms, utilize a wide range of materials, and can be incorporated into various other systems.
During operation and as explained in greater detail below, the heat exchanger 10 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). In addition, while reference is made herein to transferring heat energy between two working fluids, in some embodiments of the present invention, the heat exchanger 10 can operate to transfer heat energy between three or more fluids. Alternatively or in addition, the heat exchanger 10 can operate as a recuperator and can transfer heat energy from a high temperature location of a heating circuit to a low temperature location of the same heating circuit. In some such embodiments, the heat exchanger 10 can transfer heat energy from a working fluid traveling through a first portion of the heat transfer circuit to the same working fluid traveling through a second portion of the heat transfer circuit.
As shown in FIG. 1, the heat exchanger 10 can include a first header 18 and a second header 20 positioned at respective first and second ends 22, 24 of a stack of heat exchanger tubes 26. In the illustrated embodiment of FIGS. 1-5, the first header 18 includes a first collecting tank 30 and the second header 20 includes a second collecting tank 32. In other embodiments, the heat exchanger 10 can include a single header 18 located at one of the first and second ends 22, 24 or at another location on the heat exchanger 10.
As shown in FIGS. 1-5, each of the tubes 26 can be secured to the first and second headers 18, 20 such that a first working fluid flowing through the heat exchanger 10 is maintained separate from a second working fluid flowing through the heat exchanger 10. More specifically, the heat exchanger 10 defines a first flow path (represented by arrows 34 in FIG. 1) for the first working fluid and a second flow path (represented by arrows 36 in FIG. 1) for a second working fluid, and the first and second flow paths 34, 36 are separated such that the first working fluid is prevented from entering the second flow path 36 and such that the second working fluid is prevented from entering the first flow path 34.
In some embodiments, such as the illustrated embodiment of FIGS. 1-5, the tubes 26 are secured to the first and second headers 18, 20 such that the first working fluid enters the heat exchanger 10 through a first inlet aperture 40 in the first header 18, travels through the heat exchanger 10 along the first flow path 34, and is prevented from entering the second flow path 36. In these embodiments, the tubes 26 can be secured to the first and second headers 18, 20 such that the second working fluid enters the heat exchanger 10 through a second inlet aperture 42 in the second header 20, travels through the heat exchanger 10 along the second flow path 36, and is prevented from entering the first flow path 34.
In some such embodiments, the first flow path 34 extends through the first inlet aperture 40 in the first header 18, through the tubes 26, and out of the heat exchanger 10 through a first outlet aperture 44 in the second header 20, and the second flow path 36 extends through the second inlet aperture 42, around and between the tubes 26 (e.g., along outer surfaces 45 of the tubes 26), and out of the heat exchanger 10 through a second outlet aperture 46 in the first header 18.
In other embodiments, the tubes 26 can have other orientations and configurations and the first and second flow paths 34, 36 can be maintained separate by dividers, inserts, partitions, and the like. In still other embodiments, the first flow path 34 can extend through some of the tubes 26 while the second flow path 36 can extend through other tubes 26.
Alternatively or in addition, dividers 38 can be positioned in the first and/or second headers 18, 20 to separate or at least partially separate the first and second flow paths 34, 36. In some embodiments, such as the illustrated embodiment of FIGS. 1-5, the dividers 38 can be contoured to closely engage the interior of the first and/or second headers 18, 20 and to prevent the first and/or second working fluids from leaking between the interior walls of the first and/or second headers 18, 20 and the outer perimeter of the dividers 38.
As shown in FIG. 2, the dividers 38 can have apertures 39 sized to receive one or more of the tubes 26. In embodiments such as the illustrated embodiment of FIGS. 1-5 having dividers 38 supported in the first and/or second headers 18, 20, the first working fluid flowing along the first flow path 34 can enter the tubes 26 through apertures 39 formed in the dividers 38. In these embodiments, the dividers 38 prevent the second working fluid from entering the tubes 26. In these embodiments, the dividers 38 can also direct the second working fluid from the second inlet aperture 42 between adjacent tubes 26 and can prevent the second working fluid from flowing into the tubes 26. The dividers 38 can also prevent the first working fluid from flowing between the tubes 26.
In the illustrated embodiment of FIGS. 1-5, the heat exchanger 10 is configured as a cross-flow heat exchanger such that the first flow path 34 or a portion of the first flow path 34 is opposite to or counter to the second flow path 36 or a portion of the second flow path 36. In other embodiments, the heat exchanger 10 can have other configurations and arrangements, such as, for example, a parallel-flow or a counter-flow configuration.
In the illustrated embodiment of FIGS. 1-5, the heat exchanger 10 is configured as a single-pass heat exchanger with the first working fluid traveling along the first flow path 34 through at least one of a number of tubes 26 and with the second working fluid traveling along the second flow path 36 between adjacent tubes 26. In other embodiments, the heat exchanger 10 can be configured as a multi-pass heat exchanger with the first working fluid traveling in a first pass through one or more of the tubes 26 and then traveling in a second pass through one or more different tubes 26 in a direction opposite to the flow direction of the first working fluid in the first pass. In these embodiments, the second working fluid can travel along the second flow path 36 between adjacent tubes 26.
In yet other embodiments, the heat exchanger 10 can be configured as a multi-pass heat exchanger with the second working fluid traveling in a first pass between a first pair of adjacent tubes 26 and then traveling in a second pass between another pair of adjacent tubes 26 in a direction opposite to the flow direction of the second working fluid in the first pass. In these embodiments, the first working fluid can travel along the first flow path 34 through at least one of the tubes 26.
In the illustrated embodiment of FIGS. 1-5, the heat exchanger 10 includes seven tubes 26, each of which has a substantially rectangular cross-sectional shape. In other embodiments, the heat exchanger 10 can include one, two, three, four, five, six, eight, or more tubes 26, each of which can have a triangular, circular, square or other polygonal, oval, or irregular cross-sectional shape.
As shown in FIG. 2, the tubes 26 are assembled together in a stacking direction 50. In some embodiments, such as the illustrated embodiment of FIGS. 1-5, reinforcing plates 52 can be added to the stack of tubes 26 to at least partially enclose the tubes 26. In some such embodiments, reinforcing plates 52 can be positioned adjacent to the top and bottom of the stack of tubes 26. Alternatively or in addition, a housing can be provided around at least some of the tubes 26. In embodiments having reinforcing plates 52 and/or a housing, the reinforcing plates 52 and/or the housing can protect the tubes 26 from the mechanical effects of temperature fluctuations.
As mentioned above, in some embodiments, the second flow path 36 or a portion of the second flow path 36 can extend across the outer surface 45 of one or more of the tubes 26. In some such embodiments, a housing can be provided around the tubes 26 to prevent the second fluid from leaking out of the heat exchanger 10 between adjacent tubes 26. Alternatively or in addition, ribs 56 can be formed along the outer surfaces 45 of the tubes 26 to at least partially define channels 58.
As shown in FIG. 1, the heat exchanger 10 can include connectors 54 for supporting the heat exchanger 10 and/or for securing the heat exchanger 10 to an external structure. In some embodiments, such as the illustrated embodiment, connectors 54 can be provided on the collecting tanks 22, 23. As shown in FIG. 1, the second inlet aperture 42 and/or the second outlet aperture 46 can be positioned along the connectors 54. As also shown in FIG. 1, a sealing groove or sealing rim 55 can be formed around the second inlet aperture 42 and/or the second outlet aperture 46 so that the heat exchanger 10 can be directly fastened to an external structure and so that the second working fluid does not leak out of the heat exchanger 10 around the second inlet aperture 42 and/or the second outlet aperture 46.
In embodiments, such as the illustrated embodiment of FIGS. 1-5, having outwardly extending ribs 56, the ribs 56 of each tube 26 can be secured to an adjacent tube 26. In some such embodiments, the ribs 56 of one tube 26 can be soldered, brazed, or welded to an adjacent tube 26. In other embodiments, adjacent tubes 26 can be secured together with inter-engaging fasteners, other conventional fasteners, adhesive or cohesive bonding material, by an interference fit, etc.
Additional elevations, recesses, or deformations 60 can also or alternatively be provided on the outer surfaces 45 of the tubes 26 to provide structural support to the heat exchanger 10, prevent the deformation or crushing of one or more tubes 26, maintain a desired spacing between adjacent tubes 26, improve heat exchange between the first and second working fluids, and/or generate turbulence along one or both of the first and second flow paths 34, 36.
In some embodiments, the heat exchanger 10 can include inserts 66 to improve heat transfer between the first and second working fluids as the first and second working fluids travel along the first and second flow paths 34, 36, respectively. As shown in FIGS. 1-5, the inserts 66 can be positioned in the tubes 26. Alternatively or in addition, inserts 66 can be positioned between adjacent tubes 26. In other embodiments, inserts 66 can be integrally formed with the tubes 26 and can extend outwardly from the outer surfaces 45 of the tubes 26.
In the illustrated embodiment of FIGS. 1-5, an insert 66 is supported in each of the tubes 26, and extends along the entire length or substantially the entire length of each of the tubes 26 between opposite ends 68 of the tubes 26. In other embodiments, an insert 26 can be supported in only one or less than all of the tubes 26, and the insert(s) 66 can extend substantially the entire length of the tube(s) 26 between opposite ends 68 of the tube(s) 26, or alternatively, the insert 66 can extend through the tube(s) 26 along substantially less than the entire length of the tube(s) 26. In still other embodiments, two or more inserts 66 can be supported by or in each tube 26.
In some embodiments, the inserts 66 can be secured to the tubes 26. In some such embodiments, the inserts 66 are soldered, brazed, or welded to the tubes 26. In other embodiments, the inserts 26 can be connected to the tubes 26 in another manner, such as, for example, by an interference fit, adhesive or cohesive bonding material, fasteners, etc.
In some embodiments, such as the illustrated embodiment of FIGS. 1-5, the ends 68 of the tubes 26 can be press-fit into one or both of the first and second headers 18, 20. In some such embodiments, the ends 68 of the tubes 26 and the inserts 66 supported in the tubes 26 or between the tubes 26 can be at least partially deformed when the tubes 26 and/or the inserts 66 are press-fit into the first and/or second headers 18, 20. In some such embodiments, the tubes 26 and/or the inserts 66 are pinched and maintained in compression to secure the tubes 26 and/or the inserts 66 in a desired orientation and to prevent leaking.
In the illustrated embodiment of FIGS. 1-5, the inserts 66 are formed from folded sheets of metal. In other embodiments, the inserts 66 can be cast or molded in a desired shape and can be formed from other materials (e.g., aluminum, iron, and other metals, composite material, and the like). In still other embodiments, the inserts 66 can be cut or machined to shape in any manner, can be extruded or pressed, can be manufactured in any combination of such operations, and the like.
As shown in FIGS. 2, 4, and 5, the inserts 66 can be corrugated and can have a series of alternating peaks 72 and valleys 74. As also shown in FIGS. 2, 4, and 5, the peaks 72 and valleys 74 can engage respective upper and lower interior sides of a tube 26, and flanks 76 can extend (e.g., in a generally vertical direction in the illustrated embodiment of FIGS. 2, 4, and 5) between adjacent peaks 72 and valleys 74.
In some embodiments, such as the illustrated embodiment of FIGS. 6 and 7 (described in detail below), the flanks 76 can extend in a generally linear direction between opposite interior sides (e.g., between upper and lower opposing sides in the illustrated embodiment of FIGS. 6 and 7) of the tubes 26. In other embodiments, such as the illustrated embodiment of FIGS. 1-5, the flanks 76 can extend in a non-linear direction between the opposite interior sides (e.g., between upper and lower sides in the illustrated embodiment of FIGS. 1-5) of the tubes 26. In the illustrated embodiments, the peaks 72 and valleys 74 extend along a longitudinal dimension of the insert 66 and the tube 26. In other embodiments, the insert 66 may be in contact with only one side of the tube 26.
As shown in FIGS. 2, 4, and 5, in some such embodiments, the flanks 76 can have a generally wavy cross-sectional shape. In other embodiments, the inserts 66 can have other shapes and configurations. For example, in some embodiments, the inserts 66 can have pointed, squared, or irregularly shaped peaks 72 and/or valleys 74. In other embodiments, the inserts 66 can have a saw-toothed or sinusoidal profile.
In embodiments, such as the illustrated embodiment of FIGS. 1-5, having a wavy cross-sectional shape, the inserts 66 operate as springs to absorb or at least partially absorb vibrations and/or to absorb expansions and contractions of the inserts 66 caused by fluctuating inlet temperatures of the first and/or second working fluids. In some such embodiments, the elasticity of the wavy inserts 66 prevents and/or reduces cracking and breaking of the inserts 66. Alternatively or in addition, the elasticity of the wavy inserts 66 prevents and/or reduces cracking and breaking of connections (e.g., solder points, braze points, weld points, etc.) between the peaks 72 and valleys 74 of the inserts 66 and the interior sides of the tubes 26. In some embodiments, the wavy cross-section of the insert 66 may extend only a portion of a length L of the insert 66. For example, the wavy cross-section may be provided at the ends of the insert 66 where the tube 26 is connected to a header 18, 20, or alternatively where the tube 26 and/or insert 66 experiences the most thermal and mechanical stress.
As shown in FIGS. 2, 4, and 5, at least one structural deficiency 78 can be formed along at least one of the flanks 76 of an insert 66. In some embodiments, the structural deficiency 78 can include a groove extending along the entire length L or substantially the entire length L of a flank 76 between opposite ends 80 of the insert 66. In other embodiments, the groove 78 can extend along less than the entire length L of the flank 76 (e.g., a groove 78 can be staggered along the length L of a flank 76). In some embodiments, the structural deficiency 78 may extend only a portion of a length L of the insert 66. For example, a groove 78 may be provided at the ends of the insert 66 where the tube 26 is connected to a header 18, 20, or where the tube 26 and or insert 66 experiences the most thermal and mechanical stress. In some embodiments, a groove 78 or other structural deficiency 78, can be formed in opposing sides of the insert 66 to further weaken the insert at a particular location on the flank 76.
Structural deficiencies 78 can take various forms and shapes, and can be provided on the inserts 66 in various manners including scoring, stamping, etching, and the like. In some embodiments, groove 78 has a cross-section that is V-shaped, U-shaped, rectangular, or irregular. Structural deficiencies 78 can be formed in the insert 66 prior to or after folding or cutting of the insert 66.
In embodiments, such as the illustrated embodiment of FIGS. 1-5, having grooves 78, failures and/or cracking of the inserts 66 caused by expansion and contraction of the inserts 66 will occur along the grooves 78 where the inserts 66 are weakest. In these embodiments, the grooves 78 are positioned at locations on the inserts 66 where cracks and/or failures are anticipated to cause the least damage to the structural integrity of the inserts 66 and/or where cracks or failures are anticipated to have a minimal affect on the heat transfer characteristics of the heat exchanger 10.
As shown in FIGS. 2, 4, and 5, the grooves 78 can be located midway along the height H of the flanks 76 so that the grooves 78 are spaced a maximum distance from the peaks 72, valleys 74, and corresponding connection points of the inserts 66. Thus, structural failures (i.e., cracking, buckling, etc. of the insert 66) will be spaced a maximum distance from the connection points (e.g., solder points, braze points, weld points, etc.) between the peaks 72 and valleys 74 of the inserts 66 and the interior sides of the tubes 26. This enables the insert 66 to provide sufficient structural support to the tube 26 and simultaneously maximize the heat transfer between the first and second fluids despite a structural failure of the insert 66 as is described in more detail below.
In embodiments, such as the illustrated embodiment of FIGS. 1-5, in which grooves 78 are located along the flanks 76 of the inserts 66, any cracks or failures occur at or near a midpoint of the height H of the flanks 76 and at a maximum distance from the connection points (e.g., solder points, braze points, weld points, etc.) between the peaks 72 and valleys 74 of the inserts 66 and the interior sides of the tubes 26. In these embodiments, even after cracking or failure of the flanks 76, the height H of the flanks 76 is approximately equal to ½ of the original height H of the flanks 76 prior to cracking or failure of the flanks 76. Alternatively or in addition, even after cracking or failure of the flanks 76, the peaks 72 and valleys 74 of the inserts 66 remain connected to the interior sides (e.g., the upper and lower interior sides in the illustrated embodiment of FIGS. 1-5) of the tubes 26. In this manner, the inserts 66 remain connected to the tubes 26 and continue to provide a maximum structural support to the tubes 26, even after cracking or failure of the flanks 76.
More particularly, it has been found that for corrugated inserts 66, such as, for example, the inserts 66 of the illustrated embodiment of FIGS. 1-5, the stiffness of an insert 66 can be calculated using the equation 1/12*(insert thickness T)*(insert height H)³. Accordingly, in embodiments, such as the illustrated embodiment of FIGS. 1-5, in which cracking and failures occur at the grooves 78, which are spaced a maximum distance from the peaks 72 and valleys 74 of the inserts 66 and which are spaced a maximum distance from the connection points (e.g., solder points, braze points, weld points, etc.) between the peaks 72 and valleys 74, the height H of each of the flanks 76, even after cracking or failure, is maximized. In this manner, each of the flanks 76 can maintain a maximum possible stiffness, even after failure or cracking.
FIGS. 6 and 7 illustrate an alternate embodiment of a heat exchanger 210 according to the present invention. The heat exchanger 210 shown in FIGS. 6 and 7 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 and 7 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 and 7. Features and elements in the embodiment of FIGS. 6 and 7 corresponding to features and elements in the embodiments of FIGS. 1-5 are numbered in the 200 series.
In the illustrated embodiment of FIGS. 6 and 7, the tubes 226 of the heat exchanger 210 support inserts 266 having a series of alternating peaks 272 and valleys 274. As also shown in FIGS. 6 and 7, the peaks 272 and valleys 274 can engage respective upper and lower interior sides of a tube 226. Flanks 276 can extend in a generally vertical direction in the illustrated embodiment of FIGS. 6 and 7 between adjacent peaks 272 and valleys 274.
As shown in FIGS. 6 and 7, the flanks 276 can extend in a generally linear direction between upper and lower interior sides of the tubes 226 and can be substantially perpendicular to the upper and lower interior sides of the tubes 226. In other embodiments, the inserts 266 can have other shapes and configurations.
Grooves 278 can be formed along at least some of the flanks 276 of the inserts 266. The grooves 278 can take various forms and shapes, and can be provided on the inserts 266 in various manners including scoring, stamping, bending, and the like. As shown in FIGS. 6 and 7, the grooves 278 can be positioned at locations on the inserts 266 where cracks and/or failures are anticipated to cause the least damage to the structural integrity of the inserts 266 and/or where cracking or failures are anticipated to have a minimal affect on the heat transfer characteristics of the heat exchanger 210.
As shown in FIGS. 6 and 7, the grooves 278 can be located midway along the height H of the flanks 276 so that the grooves 278 are spaced a maximum distance from the peaks 272 and valleys 274 of the inserts 266 and so that the grooves 278 are spaced a maximum distance from the connection points (e.g., solder points, braze points, weld points, etc.) between the peaks 272 and valleys 274 of the inserts 266 and the interior sides of the tubes 226.
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 in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention.

Claims

1. A heat exchanger comprising:

a first flow path for a first working fluid;

a second flow path for a second working fluid;

a corrugated insert positioned along the first flow path;

a structural deficit provided at a location on the insert such that structural failures occur at the location in preference to other locations on the insert; and

a tube at least partially defining one of the first and second flow paths, the insert being secured to the tube.

2. The heat exchanger of claim 1, wherein the structural deficit comprises a groove.

3. The heat exchanger of claim 1, wherein the structural deficit comprises a staggered groove.

4. The heat exchanger of claim 1, wherein the corrugated insert comprises a peak and an adjacent valley and wherein the structural deficit is positioned between the peak and the valley.

5. The heat exchanger of claim 4, wherein the peak and valley extend along a longitudinal dimension of the insert and the structural deficit extends along a portion of the longitudinal dimension of the insert in a direction substantially parallel to a fold of the insert.

6. The heat exchanger of claim 4, wherein the structural deficit is positioned substantially equidistantly between the peak and valley such that structural failures occur at a midpoint between the peak and valley.

7. The heat exchanger of claim 1, wherein the insert comprises adjacent folds such that the insert extends between opposing surfaces of the tube and is secured to the surfaces of the tube at the folds.

8. The heat exchanger of claim 7, wherein the structural deficit is located midway along a height of the insert between the opposing surfaces of the tube.

9. The heat exchanger of claim 7, wherein the structural deficit is spaced away from the folds of the insert.

10. The heat exchanger of claim 7, wherein the folds are secured to the surfaces of the tube by one of welded, soldered, and brazed connections.

11. A heat exchanger comprising:

a header;

a tube secured to the header; and

a corrugated insert secured to at least one surface of the tube, the insert having a groove formed along at least a portion of a length of the insert and spaced apart from the surface of the tube to which the insert is secured.

12. The heat exchanger of claim 11, wherein the insert defines adjacent legs, and wherein the groove is located along one of the legs.

13. The heat exchanger of claim 12, wherein at least a portion of one of the legs has a wavy cross-section.

14. The heat exchanger of claim 12, wherein the insert is secured between opposing surfaces of the tube, and wherein the groove is positioned along the insert such that the insert remains secured to the opposing surfaces after a structural failure.

15. The heat exchanger of claim 14, wherein the legs of the insert provide sufficient structural support for the opposing surfaces of the tube after a structural failure.

16. The heat exchanger of claim 12, wherein the corrugated insert comprises a peak and an adjacent valley and wherein the groove is positioned between the peak and the valley.

17. The heat exchanger of claim 12, wherein the corrugated insert comprises a peak and an adjacent valley, and wherein the groove is positioned substantially equidistantly between the peak and valley such that the structural failures occur at a midpoint between the peak and valley.

18. The heat exchanger of claim 12, wherein the groove has a cross-section that is substantially V-shaped.

19. A heat exchanger having a tube and an insert supported by the tube, the insert comprising:

a corrugation defining a peak and an adjacent valley;

a groove extending along a longitudinal dimension of the insert between the peak and the adjacent valley and providing a preferred location for structural failures.

20. The heat exchanger of claim 19, wherein the groove is positioned substantially equidistantly between the peak and the valley such that structural failures occur at a midpoint between the peak and the valley.

21. The heat exchanger of claim 19, wherein the groove is located at a maximum distance between the peak and the valley.

22. The heat exchanger of claim 19, wherein the insert is attached to opposing surfaces of the tube in at least one location along at least one of the peak and the valley.

23. The heat exchanger of claim 19, wherein the groove extends substantially along the entire longitudinal dimension of the insert.

24. The heat exchanger of claim 19, wherein the longitudinal dimension of the insert terminates in opposing ends of the insert, and wherein the groove extends from an end to a location along the longitudinal dimension of the insert.

25. The heat exchanger of claim 24, and further comprising a header into which an end of the tube extends, wherein the insert extends substantially the entire length of the tube and the groove extends to a location where the tube connects to the header.

26. The heat exchanger of claim 24, and further comprising a header into which an end of the tube extends, wherein the insert extends substantially the entire length of the tube and the groove extends beyond a location where the tube connects to the header.

27. A method of assembling a heat exchanger comprising the steps of:

providing a heat exchanger tube;

positioning an insert in the tube;

connecting the insert to a surface of the tube;

forming a structural deficiency along at least a portion of a length of the insert at a maximum distance from a point of connection between the insert and the surface of the tube so that failures occur along the structural deficiency.

28. The method of claim 27, wherein forming the structural deficiency includes forming a groove, and wherein the structural deficiency is formed having a cross-section that is one of substantially U-shaped, V-shaped, or rectangular.

29. The method of claim 27, wherein the structural deficiency is formed by one of scoring, stamping, and etching.

30. The method of claim 27, wherein the insert is connected to the surface of the tube by one of brazing, soldering, or welding.

31. The method of claim 27, and further comprising folding the insert to form alternating peaks and valleys.

32. The method of claim 31, wherein the structural deficiency is formed prior to the folding of the insert.

33. The method of claim 31, wherein the structural deficiency is formed after the folding of the insert.

34. The method of claim 31, wherein the peaks and valleys of the insert are connected to opposing surfaces of the tube.