Patent Publication Number: US-9417011-B2

Title: Heat exchanger with self-aligning fittings

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/763,747 filed Feb. 12, 2013, the contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a heat exchanger with fittings which self-align when inserted into a rigid manifold. 
     BACKGROUND 
     Most conventional heat exchangers use fluid connecting fittings that interface with the vehicle transmission, engine, power steering etc. via tube or hose type fluid conduits. These conduits are relatively flexible, and can accommodate a certain degree of misalignment or variation in the heat exchanger fittings. 
     Recently, there is a trend to provide fluid connections that require the heat exchanger to interface directly with a rigid manifold. Such rigid manifolds use machining to create fitting receptacles or “sockets” to receive the heat exchanger fittings. But today&#39;s machining technology can achieve dimensional tolerances with much greater precision than brazed heat exchanger product assemblies, as the latter involve significant stack up tolerance variation. This can create a conflict in dimensional control needed to achieve a manufacturable heat exchanger assembly, and a reliable seal. 
     There is a need to provide a more manufacturable heat exchanger with fittings which self-align during insertion into a rigid manifold. 
     SUMMARY 
     According to an embodiment, there is provided a heat exchanger, comprising: an inlet opening provided with an inlet fitting; an outlet opening provided with an outlet fitting, wherein the inlet and outlet fittings are hollow and have open ends, and wherein the fittings face in the same direction and are spaced apart from one another; wherein each of the fittings have a cylindrical base portion and a cylindrical top portion, wherein each of the fittings is provided with a circumferential groove extending about its entire circumference, and a resilient sealing element is received in the groove; wherein the base portion of each of the fittings has a flat, annular sealing surface which is sealed to a surface of the heat exchanger in an area surrounding the inlet opening or the outlet opening. 
     According to an embodiment, the base portion of each of the fittings has a radially outwardly extending planar base flange, and the flat, annular sealing surface comprises a bottom surface of the planar base flange, wherein said surface of the heat exchanger is flat. 
     According to an embodiment, said surface of the heat exchanger comprises an outer surface of a plate comprised of an aluminum brazing sheet, wherein the inlet and outlet fittings are formed of aluminum or an aluminum alloy, and wherein the inlet and outlet fittings are both sealed to the outer surface of said plate by brazing. 
     According to an embodiment, the cylindrical base portion has a larger diameter than the cylindrical top portion, and the circumferential groove and the resilient sealing element may be provided in the top portion or in the base portion. 
     According to an embodiment, the circumferential groove and the resilient sealing element are provided in the base portion, and each of the fittings further comprises a sloped surface which forms a transition between the base portion and the top portion of the fitting, such that the base portion extends to a bottom edge of the sloped surface. The circumferential groove of the base portion of each said fitting may be located approximately midway between the ends, and each of the fittings may have a top end with a radially inwardly extending sloped surface. 
     According to an embodiment, the top portion has a larger diameter than the cylindrical base portion, and wherein the circumferential groove and the resilient sealing element are provided in the top portion. 
     According to an embodiment, each of the fittings has a top end with a radially inwardly extending sloped surface located between the resilient member and the top end, and wherein the top end of the fitting has a smaller diameter than an outside diameter of resilient member. 
     According to an embodiment, the groove has a rectangular cross-section and the sealing member comprises a sealing gland having a rectangular profile on its inner radial face, and having a spherical profile on its outer radial face. 
     According to an embodiment, the top portion of the fitting has a truncated spherical cross-section having a radius which is less than a radius of the spherical profile on the outer radial face of the sealing gland. 
     According to an embodiment, there is provided, in combination, a heat exchanger and a rigid manifold, wherein the heat exchanger has an inlet opening provided with an inlet fitting and an outlet opening provided with an outlet fitting, wherein the inlet and outlet fittings face in the same direction and are spaced apart from one another; wherein the rigid manifold comprises an inlet socket in which the inlet fitting is received, and an outlet socket in which the outlet fitting is received, the inlet and outlet sockets being spaced apart from one another; each of the fittings having a cylindrical base portion proximate to the inlet or outlet opening with which it is associated, and a cylindrical top portion distal therefrom, the base portion having a larger diameter than the top portion, wherein the base portion is provided with a circumferential groove extending about its entire circumference, and a resilient sealing element is received in the groove; each of the sockets having a cylindrical base portion proximate to an open mouth of the socket, and a cylindrical top portion distal therefrom, wherein the top portion of the socket receives the top portion of one of the fittings, and the base portion of the socket receives the base portion of the same fitting, and wherein an inner cylindrical surface of the base portion of the socket provides a sealing surface against which the resilient sealing member is received with a fluid-tight seal. 
     According to an embodiment, the sealing surface of each of the sockets has an inner diameter which is equal to or greater than a maximum outside diameter of the top portion of the fitting with which it is associated, plus a maximum diametrical position tolerance of a top end of the fitting. 
     According to an embodiment, each of the fittings further comprises a sloped surface which forms a transition between the base portion and the top portion of the fitting; wherein each of the sockets further comprises a sloped surface which forms a transition between the base portion and the top portion of the socket; and wherein the sloped surface of each fitting engages the sloped surface of the socket with which it is associated with the fitting completely inserted in the socket. 
     According to an embodiment, each of the fittings has a top end distal from the base, and wherein a distance from the top end of the fitting to the resilient member is greater than a distance from the open mouth of the socket to the bottom end of the top portion of the socket. 
     According to an embodiment, each of the fittings has a top end with a radially inwardly extending sloped surface, and wherein a distance between a bottom end of the sloped surface and the resilient member is greater than a distance from the open mouth of the socket to the bottom end of the top portion of the socket. 
     According to an embodiment, there is provided, in combination, a heat exchanger and a rigid manifold, wherein the heat exchanger has an inlet opening provided with an inlet fitting and an outlet opening provided with an outlet fitting, wherein the inlet and outlet fittings face in the same direction and are spaced apart from one another; wherein the rigid manifold comprises an inlet socket in which the inlet fitting is received, and an outlet socket in which the outlet fitting is received; each of the fittings having a cylindrical base portion proximate to the inlet or outlet opening with which it is associated, and a cylindrical top portion distal therefrom, the top portion having a larger diameter than the base portion, wherein the top portion is provided with a circumferential groove extending about its entire circumference, and a resilient sealing element is received in the groove; each of the sockets having an outwardly sloped base portion proximate to an open mouth of the socket, and a cylindrical top portion distal therefrom, wherein the top portion of the socket receives the top portion of one of the fittings, and the base portion of the socket receives the base portion of the same fitting, and wherein an inner cylindrical surface of the base portion of the socket provides a sealing surface against which the resilient sealing member is received with a fluid-tight seal; and wherein each of the fittings has a top end with a radially inwardly extending sloped surface located between the resilient member and the top end, and wherein the top end of the fitting has a smaller diameter than an outside diameter of resilient member. 
     According to an embodiment, the groove has a rectangular cross-section and the sealing member comprises a sealing gland having a rectangular profile on its inner radial face, and having a spherical profile on its outer radial face. 
     According to an embodiment, the top portion of the fitting has a truncated spherical cross-section having a radius which is less than a radius of the spherical profile on the outer radial face of the sealing gland. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  is a cross-sectional view of a heat exchanger and rigid manifold according to a first embodiment of the invention; 
         FIG. 2  is a side elevation view of a fitting of the heat exchanger of  FIG. 1 ; 
         FIG. 3  is an cross sectional view of the fitting of  FIG. 2  along a central longitudinal axis of the fitting; 
         FIG. 4  is an enlarged cross-sectional view showing a socket of the rigid manifold in isolation; 
         FIGS. 5, 5   a ,  6  and  7  are cross-sectional side views showing the insertion of a fitting of the heat exchanger of  FIG. 1  into a socket of the rigid manifold of  FIG. 1 ; 
         FIG. 8  is a cross-sectional side view showing a fitting of a heat exchanger and a socket of a rigid manifold according to a second embodiment of the invention, prior to insertion of the fitting into the socket; 
         FIG. 8 a    is a cross-sectional side view showing the fitting and the socket of  FIG. 8 , with the fitting partly inserted into the socket; 
         FIG. 9  is a cross-sectional side view showing the fitting and the socket of  FIG. 8 , with the fitting inserted into the socket; 
         FIGS. 10-14  are cross-sectional side views showing the insertion of a fitting of a heat exchanger into the socket of a rigid manifold, according to a third embodiment of the invention; 
         FIG. 15  is a cross-sectional side view showing a fitting according to a variant of the third embodiment of the invention; and 
         FIG. 16  is a cross-sectional side view showing a fitting according to another variant of the third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A heat exchanger  10  according to a first embodiment of the invention is described below with reference to  FIGS. 1 to 7 . 
     Heat exchanger  10  is shown alongside a rigid manifold  12 . The heat exchanger  10  has a pair of fittings, namely an inlet fitting  14  and an outlet fitting  16 , which are to be inserted into sockets  18  and  20  of manifold  12 . 
     Heat exchanger  10  is shown as comprising a pair of heat exchanger plates, namely a top plate  22  and a bottom plate  24 . The plates  22 ,  24  are sealed together at their peripheral edges, for example by brazing, and enclose a fluid flow passage  26  for flow of a fluid such as a liquid engine coolant from the inlet fitting  14  to the outlet fitting  16 , in the direction of the arrows shown in  FIG. 1 . Although flow passage  26  is described herein as a coolant flow passage for a liquid engine coolant, this is not necessarily the case. The heat exchanger plates  22 ,  24  and fittings  14 ,  16  may be comprised of aluminum or aluminum alloys, and may be joined together by brazing. The manifold  12  may also be comprised of aluminum or an aluminum alloy. 
     Although the structure of heat exchanger  10  is shown as comprising a single pair of plates  22 ,  24 , it will be appreciated that the structure of heat exchanger  10 , aside from the structure and location of fittings  14 ,  16 , is relatively unimportant to the present invention, and is therefore variable. For example, heat exchanger  10  may comprise a stack of tubes or plates which are either self-enclosed or enclosed within a housing, and which do not necessarily have the appearance of plates  22 ,  24  of  FIG. 1 . Also, where the heat exchanger  10  includes multiple flow passages  26 , they may alternate with flow passages for one or more other fluids. Furthermore, where the fluid flowing through flow passage  26  is a coolant, the top and/or bottom plate  22 ,  24  of heat exchanger may be in direct contact with a fluid and/or a solid object which requires cooling. 
     A pair of openings  28 ,  30  is formed in the top plate  22  of heat exchanger  10 . Opening  28  is an inlet opening which receives the inlet fitting  14  and opening  30  is an outlet opening which receives the outlet fitting  16 . The fittings  14 ,  16  are sealingly connected to top plate  22 , for example by brazing. In this embodiment, the openings  28 ,  30  are circular, although it will be appreciated that the shape of the openings depends on the shape of the fittings. 
     The fittings  14  and  16  are shown as being identical. Therefore, only the inlet fitting  14  will be described in detail below and the elements of fittings  14 ,  16  are identified with the same reference numerals. Except where otherwise indicated, the following description of inlet fitting  14  also applies to outlet fitting  16 . 
     Fitting  14  has a base portion  32  through which fitting  14  is attached to the top plate  22 , and a top portion  34  at the other end of fitting  14 . The base portion  32  has a larger diameter than the top portion  34 . An alignment axis A extends through fitting  14  and socket  18  and defines an axial direction. The central longitudinal axis C of the fitting  14  is also shown in the drawings. The alignment axis A and the central longitudinal axis C of the fitting  14  and socket  18  are co-linear when the fitting  14  and socket are in perfect alignment with one another, as shown in  FIG. 1 . 
     The fitting  14  has a sidewall  36  which extends axially throughout the height of fitting  14 , and which defines a hollow interior  38  of fitting  14 . The sidewall  36  and interior  38  are shown as being generally cylindrical, and the ends of fitting  14  are open to permit fluid flow through hollow interior  38 , into or out of the heat exchanger flow passage  26 . 
     The base portion  32  of fitting  14  has a flat, annular sealing surface  41  which sits on top of top plate  22  and which is sealed to the outer surface of top plate  22  in an area surrounding the inlet opening  28 , for example by brazing. In the embodiment shown in the drawings, the base portion  32  of fitting  14  has a planar base flange  40  extending radially outwardly from the base portion  32 , with the annular sealing surface  41  comprising the bottom surface of the flange  40 . However, it will be appreciated that the outwardly extending flange  40  may not be necessary in all embodiments, depending at least partly on the outer diameter of the base portion  32 . The base flange  40  may also help to maintain the vertical orientation of fitting  14  during brazing, i.e. such that the center line of the fitting remains substantially parallel to axis A. 
     Located radially inwardly of sealing surface  41  is an annular ridge  42 , separated from the sealing surface  41  by an axially extending shoulder  44 . The shoulder  44  is provided at the inner peripheral edge of the annular sealing surface  41  and has an outer diameter which is slightly less than the diameter of the opening  28 , and therefore sits inside the opening  28  with the shoulder  44  facing an edge of the opening  28 , and may be sealed to the edge of opening  28  by brazing. 
     The base portion  32  of fitting  14  extends from the base flange  40  to a point  54  on the outer surface  46  of sidewall  36  which is the bottom edge of a sloped surface  56  (also referred to herein as “side chamfer  56 ”) of fitting  14 . The side chamfer  56  forms a transition between the larger diameter base portion  32  and the smaller diameter top portion  34  of fitting  14 . 
     Within the base portion  32 , the outer surface  46  of sidewall  36  is provided with a groove  48 . In the illustrated embodiment, the groove  48  is located approximately midway between the top and bottom ends of fitting  14 , and is closer to point  54  than to the base flange  40 . The groove  48  extends around the entire circumference of sidewall  36  and extends radially inwardly from the outer surface  46 . The groove  48  has a height (measured axially) and a depth (measured radially) sufficient to accommodate a resilient sealing member such as O-ring  50 . With the exception of the base flange  40  and groove  48 , the base portion  32  has a substantially constant diameter. 
     The top portion  34  extends from the top end of fitting  14  to a point  58  on the outer surface  46  of sidewall  36  which is the top edge of side chamfer  56 . The top portion  34  has a substantially constant diameter with the exception of an inwardly extending top chamfer  60  at the nose to ease insertion of the fitting  14  into socket  18 . 
     The sockets  18 ,  20  of the rigid manifold  12  may be formed by machining. For convenience, socket  18  is referred to herein as the inlet socket because it receives the inlet fitting  14  and socket  20  is referred to as the outlet socket because it receives the outlet fitting  16 . The sockets  18 ,  20  are in flow communication with a circulation system for a fluid, such as a liquid coolant, through respective manifold flow passages  62 ,  64 . 
     The sockets  18  and  20  are shown as being identical. Therefore, only the inlet socket  18  will be described in detail below and the elements of sockets  18 , are identified with the same reference numerals. Except where otherwise indicated, the following description of inlet socket  14  also applies to outlet socket  20 . 
     The socket  18  has a base portion  66  defining an open mouth of socket  18 . The base portion  66  has a cylindrical sealing surface  67  with a substantially constant diameter which is greater than the diameter of the base portion  32  of fitting  14 , such that a fluid-tight seal is formed with the base portion  32  of fitting  14 . A bottom chamfer  74  is provided at the bottom of base portion  66 , extending from the bottom edge of sealing surface  67  of base portion  66  to the open mouth of socket  18 , and providing the mouth with a diameter slightly greater than that of the remainder of the base portion  66 . 
     The socket  18  also has a top portion  68  with a diameter smaller than the diameter of the base portion  66 , through which the socket  18  is connected to the manifold flow passage  62 . The top of socket  18  may be provided with a top chamfer  70  which forms a transition between socket  18  and manifold flow passage  62 . With the exception of top chamfer  70 , the diameter of the top portion  68  is substantially constant and is greater than the diameter of the top portion  34  of fitting  14 , to enable the top portion  34  of fitting  14  to be received inside the top portion  68  of socket  18 . 
     A side chamfer  72  forms a transition between the larger diameter base portion  66  and the smaller diameter top portion  68  of socket  18 . 
     As mentioned above, the brazed construction of heat exchanger  10  involves significant stack-up tolerance variation. The stack-up tolerance variation is the sum of a number of individual variations in the manufacture, assembly and brazing of the heat exchanger components. For example, there are small variations in the size of openings  28 ,  30 ; the locations of openings  28 ,  30  on top plate  22  and relative to each other; the size and concentricity of the braze assembly shoulder  44 ; and the deviation of the fitting&#39;s central axis from vertical. In addition to the stack-up tolerances in the heat exchanger  10 , there are relative tolerances due to thermal expansion and manifold hole machining. As a result, the location of the base of each fitting  14 ,  16  may deviate by more than about 0.5 mm from the nominal centreline defined along axis A, and the top end of each fitting  14 ,  16  may be angled by as much as 1.5-2 degrees from vertical (i.e. relative to axis A), meaning that the position of the top end of fitting may deviate by up to about 1 mm from vertical (axis A). 
     During insertion of fitting  14  into socket  18  the fitting  14  should become substantially centered in socket  18  so that the O-ring  50  seals with surface  67  within compression ranges recommended by the O-ring manufacturer. At the same time, contact between the O-ring  50  and any surfaces surrounding the bottom edge or open mouth of socket  18  should be avoided. These surfaces include the bottom chamfer  74  of socket  18 , and the top and bottom edges of bottom chamfer  74 . Contact with the bottom edge of socket  18  could damage the O-ring  50  and/or cause it to be ejected from the groove  48 , which can compromise the seal. In addition, there should be no sliding metal-to-metal contact between the fitting  14  with the sealing surface  67  of socket  18 . This sealing surface  67  may be smoothly machined and could be damaged by contact with the metal portions of fitting  14 , which may also compromise the fitting to socket seal. 
     As further discussed below, the fittings  14 ,  16  and sockets  18 ,  20  are formed to permit insertion, centering and reliable sealing of the fittings  14 ,  16  within sockets  18 ,  20 , while avoiding damage to the O-ring  50  and sealing surface  67 . Reference is now made to  FIGS. 5, 5   a ,  6  and  7 , which show the insertion of fitting  14  into socket  18 , with maximum socket and fitting misalignment.  FIGS. 5 to 7  show misalignment between the alignment axis A and the central axis C of fitting  14 , both radially and axially. For clarity and ease of illustration, this misalignment is somewhat exaggerated. Also, it will be appreciated that there may be some radial misalignment of socket  18 , but this may be negligible relative to the misalignment of fitting  14  and is therefore not shown. 
       FIG. 5  illustrates the commencement of insertion of misaligned fitting  14  into socket  18 . As shown, the first contact between fitting  14  and socket  18  may be between the top chamfer  60  of fitting  14  and the bottom chamfer  74  of socket  18 . Contact between these two surfaces as the fitting  14  is inserted will cause the misaligned fitting  14  to be guided into the base portion  66  of socket  18  as it is being centered and tilted toward vertical (axis A). 
     To prevent metal-to-metal contact between the top portion  34  of fitting  14  and the sealing surface  67  of socket  18 , the inner diameter of base portion  66  is large enough such that there will be some clearance between the top portion  34  of fitting  14  and the sealing surface  67 . Therefore, the inner diameter of base portion  66 , and the inner diameter of sealing surface  67 , may be equal to or greater than the maximum outside diameter of the top portion  34  of fitting  14 , plus the maximum diametrical position tolerance of the top end of fitting  14 . This will ensure that the top portion  34  will enter the socket  18  without contacting the bottom chamfer  74  or, as shown in  FIG. 5 , there may be sliding contact between the top chamfer  60  of fitting  14  and the bottom chamfer  74  of socket  18  as the fitting  14  enters the socket  18 . In both of these conditions, contact between the fitting  14  and the sealing surface  67  will be avoided. 
     As shown in  FIG. 5 a   , continued insertion of the fitting  14  into socket  18  may result in the top chamfer  60  of fitting  14  contacting the side chamfer  72  of socket  18 , which separates the base portion  66  and top portion  68  of socket  18 .  FIG. 5 a    also shows that continued insertion of the fitting  14  into socket  18  may result in the side chamfer  56  of fitting  14  contacting the bottom chamfer  74  of socket  18 . In particular, as the top end of fitting  14  begins entering the smaller diameter top portion  68  of socket  18 , the sliding contact between chamfers  60  and  72  causes the top portion  34  of fitting  14  to be guided toward the top portion  68  of socket  18  as it is further being centered and tilted toward axis A. 
     The centering of fitting  14  continues as it is inserted, until the top chamfer  60  of fitting  14  slides upwardly past side chamfer  72  of socket  18  and the top portion  34  of fitting  14  begins to enter the top portion  68  of socket  18 , as shown in  FIG. 6 . As also shown in  FIG. 6 , the larger diameter base portion  32  enters the bottom portion  66  of socket  18 . At this point, the fitting  14  has been substantially centered and tilted toward axis A, and it can be seen from  FIG. 6  that there is a gap between the outer surface of the base portion  34  of fitting  14  and the sealing surface  67  of socket  18 . Thus, metal-to-metal contact between the sealing surface  67  and the outer surface of the base portion  32  of fitting  14  is avoided during insertion of the fitting  14 . 
       FIG. 6  shows the partially inserted configuration where the O-ring  50  is located just outside the socket  18 , in order to illustrate the manner in which the relative configurations of fitting  14  and socket  18  help to at least partially prevent damage to the O-ring. In this regard, it can be seen from  FIG. 6  that contact between the O-ring  50  and the socket  18  is avoided until after the bottom edge of top chamfer  60  of fitting  14  enters the top portion  68  of socket  18 . This ensures that the fitting  14  will be substantially centered and tilted toward axis A, thereby ensuring that the O-ring  50  will be substantially concentrically aligned with socket  18 . Therefore, as insertion of fitting  14  into socket  18  continues, contact between the O-ring  50  and the mouth of socket  18  (i.e. the bottom edge of bottom chamfer  74 ) will be avoided, and this will prevent O-ring  50  from being damaged and/or dislodged from groove  48  as it passes through the mouth of socket  18 . 
     In order to prevent damage to the O-ring  50  as discussed above, it can be seen from  FIG. 5  that the distance D 1  from the bottom edge of top chamfer  60  to the top of O-ring  50  and/or groove  48  is greater than a distance D 2  between the top edge of side chamfer  72  and the top edge of bottom chamfer  74  and/or the mouth of socket  18 . This ensures that the O-ring  50  does not enter the socket  18  until the top portion  34  of fitting  14  is guided into the top portion  68  of socket  18 , and until the base portion  32  of fitting  14  is guided into the bottom portion of  66  of socket  18 , as shown in  FIG. 6 . 
     As insertion of fitting  14  continues, the groove  48  and O-ring  50  enter the base portion  66  of socket  18 , with the O-ring  50  undergoing even compression and sliding upwardly along sealing surface  67 , without any metal-to-metal contact between the fitting  18  and the sealing surface  67  of socket  18 . Insertion continues until the side chamfer  56  of fitting  14  contacts the side chamfer  72  of socket  18  and the groove  48  and O-ring  50  are completely received inside the base portion  66  of socket  18 , at which point insertion is complete. The fully inserted configuration is shown in  FIG. 7 , from which it can be seen that the O-ring  50  is compressed between the fitting  14  and the sealing surface  67  of socket  18 , and without any metal-to-metal contact between the fitting  14  and the sealing surface  67 . In order to ensure proper sealing, the distance D 3  from the bottom edge of side chamfer  72  to the top edge of bottom chamfer  74  of socket  18  (i.e. the height of sealing surface  67 ) is greater than the distance D 4  from the bottom edge of side chamfer  56  to the bottom of groove  48  and/or O-ring  50  of the fitting, as shown in  FIG. 6 . This ensures that the O-ring  50  is located against the sealing surface  67 , and is spaced above the upper edge of bottom chamfer  74 . 
     The angles of chamfers  56 ,  60 ,  70 ,  72  and  74  described above are in the range of about 30-60 degrees from the vertical (axial) direction, and it will be appreciated that the angles of side chamfer  56  and top chamfer  60  of fitting  14  are about the same as the angles of side chamfer  72  and top chamfer  70  of socket  18 , respectively. 
     A second embodiment of the invention is now described below with reference to  FIGS. 8, 8   a  and  9 . 
     The second embodiment of the invention provides a fitting  200  which may be an inlet or outlet fitting and which may form part of a heat exchanger including two such fittings  200  spaced apart from one another, and which may be otherwise similar or identical to heat exchanger  10  described above. The second embodiment also provides a socket  202  which may be an inlet or outlet socket and which may form part of a rigid manifold including two such sockets  202  spaced apart from one another, and which may be otherwise similar or identical to manifold  12  described above. As in the embodiment described above, the misalignment between fitting  200  and socket  202  is exaggerated, for clarity and ease of illustration.  FIG. 8  shows the misalignment of the central longitudinal axis C of fitting  200  relative to the alignment axis A before the fitting  200  is inserted into the socket  202 . 
     The fitting  200  and socket  202  of the second embodiment are similar in structure to the fittings  14 ,  16  and the sockets  18 ,  20  of the first embodiment described above. Therefore, like elements of fitting  200  and socket  202  are identified in the drawings using like reference numerals and, unless otherwise noted below, the descriptions of the elements of fittings  14 ,  16  and sockets  18 ,  20  apply equally to fitting  200  and socket  202 . 
     Fitting  200  has a base portion  32  at one end and a top portion  34  at its opposite end. The base portion  32  has a larger diameter than the top portion  34 . Fitting  200  also has a sidewall  36  which defines a hollow interior  38 . The sidewall  36  and interior  38  are generally cylindrical, and the ends of fitting  200  are open. The base portion  32  has a planar base flange  40  at its bottom end, the base flange  40  having a flat, annular bottom sealing surface  41  which sits on top of top plate  22 , as well as an annular ridge  42  and an axially extending shoulder  44 . 
     The outer surface  46  of sidewall  36  of fitting  200  has a side chamfer  56  which forms a transition between the larger diameter base portion  32  and the smaller diameter top portion  34  of fitting  200 . 
     The main difference between fitting  200  and fittings  14 ,  16  is that the sealing element of fitting  200  is provided in the top portion  34  of fitting  200 , proximate to the top end of the fitting  200 . Therefore, the outer surface  46  of sidewall  36  is provided with a circumferential groove  48  located in top portion  34 , the groove  48  accommodating a resilient sealing member such as O-ring  50 . 
     Socket  202  has a base portion  66  defining an open mouth, with a bottom chamfer  74  at the bottom of base portion  66 . Socket  202  also has a top portion  68  with a smaller diameter than the base portion  66 , through which the socket  202  is connected to manifold flow passage  62 . A side chamfer  72  forms a transition between the larger diameter base portion  66  and the smaller diameter top portion  68  of socket  202 . Socket  202  is substantially identical in appearance and structure to the sockets  18 ,  20  described above. However, due to the location of the resilient sealing member on the top portion  34  of fitting  200 , the cylindrical sealing surface  67  of socket  202  is necessarily located in the top portion  68  of socket  202 . The sealing surface  67  has a substantially constant diameter which is greater than the diameter of the top portion  34  of fitting  200 , such that a fluid-tight seal is formed with the resilient sealing element located in the top portion  34  of fitting  200 . 
     As in the first embodiment, the inner diameter of base portion  66  of socket  202 , may be equal to or greater than the maximum outside diameter of the top portion  34  of fitting  200 , plus the maximum diametrical position tolerance of the top end of fitting  200 . Thus, the inner diameter of base portion  66  is large enough such that the top portion  34  of the fitting  200  will enter the base portion  66  of socket  202  such that the O-ring will not be damaged by contact with the surfaces and edges surrounding the mouth of socket  202 . Depending on the degree of misalignment, the top portion  34  of fitting  200  may directly enter the top portion  68  of socket  202  or may be guided into the top portion  68  by sliding contact of the top chamfer  60  upwardly along the side chamfer  72  of socket  202 , as shown in  FIG. 8 a   . Also, as shown in  FIG. 8 a   , the base portion  32  of fitting  200  may be guided into the bottom portion  66  of socket  202  by sliding contact of the side chamfer  56  of fitting  200  upwardly along the bottom chamfer  74  of socket  202 . Thus, insertion and centering of fitting  200  in socket  202  is similar to that described above with reference to the first embodiment, except for the location of the seal. 
     As can be seen from  FIG. 8 , the socket  202  has a dimension D 3  corresponding to D 3  of  FIG. 6 , the distance from the top of bottom chamfer  74  to the bottom of side chamfer  72 . In this embodiment, distance D 3  is greater than D 5 , which is the distance from the top of the side chamfer  56  to the top of groove  48  in fitting  200 . What this means is that the O-ring  50  of fitting  200  will be located at or below the side chamfer  72  of socket  202  as the base portion  32  of fitting  200  enters the bottom portion  66  of the socket  202 . The entry of the base portion  32  into bottom portion  66  helps to guide the top portion  34  of fitting  200  into the top portion  68  of socket  202 , while preventing damaging contact between the O-ring and the upper edge of side chamfer  72 , and while preventing metal-to-metal contact between the fitting  200  and the sealing surface  67  of the socket  202 . 
       FIG. 9  shows the fitting  200  fully inserted into and substantially aligned with the socket  202 , with the O-ring  48  sealed between fitting  200  and the sealing surface  67  of socket  202 . 
     A third embodiment of the invention is now described below with reference to  FIGS. 10 to 16 . 
     The third embodiment of the invention provides a fitting  100  which may be an inlet or outlet fitting and which may form part of a heat exchanger including two such fittings  100  spaced apart from one another, and which may be otherwise similar or identical to heat exchanger  10  described above. The drawings show only those portions of fitting  100  which are necessary for description of the third embodiment. Although not shown, it will be appreciated that the base of fitting  100  may be provided with a base flange, bottom sealing surface, ridge and shoulder similar or identical to base flange  40 , bottom sealing surface  41 , ridge  42  and shoulder  44  of fittings  14 ,  16  described above. 
     The third embodiment also provides a socket  102  which may be an inlet or outlet socket and which may form part of a rigid manifold including two such sockets  102  spaced apart from one another, and which may be otherwise similar or identical to manifold  12  described above. It will be appreciated that the drawings show only those portions of socket  102  which are necessary for description of the third embodiment, and the hollow interior of socket  102  will be in fluid flow communication with a manifold flow passage (not shown). 
     The fitting  100  has a base portion  104  through which fitting  100  is attached to the top plate of the heat exchanger, and a head  106  at the other end of fitting  100 . The base portion  104  has a smaller diameter than the head  106 . The fitting  100  has a sidewall  108  which defines a hollow interior  110  of fitting  100 . The sidewall  108  and interior  110  are shown as being generally cylindrical and the ends of fitting  100  are open to permit fluid flow through the hollow interior  110 . 
     The base portion  104  of fitting  100  is shown as being of substantially constant diameter. The head  106  of fitting  100  is shown as having the form of a truncated section of a sphere, being reduced in diameter at its lower edge  112  and at its upper edge  114 . The lower edge  112  forms a transition point between the head  106  and base portion  104 . The head  106  is of maximum diameter about midway between the lower edge and upper edge  112 ,  114 . At this point the head  106  is provided with a circumferential groove  116  which houses a resilient sealing element in the form of an O-ring  118 . The groove  116  divides the head  106  into an upper portion  107  extending from the top of groove  116  to the upper edge  114  of head  106 , and a lower portion  109  extending from the bottom of groove  116  to the lower edge  112  of head  106 . 
     The O-ring  118  is shown in  FIGS. 10-14  as having a spherical outer surface and a circular cross section. 
     The socket  102  has an upper portion  120  of substantially constant diameter, the upper portion  120  having an inner cylindrical sealing surface  124  which is greater than the maximum diameter of the head  106  of fitting  100 , such that a fluid-tight seal is formed with the head  106  of fitting  100 . The socket  102  also has a lower portion  122  which is curved or chamfered radially outwardly from the bottom edge  126  of upper portion  120  toward the open mouth  128  of socket  102 . 
     As part of a heat exchanger assembly, the fitting  100  may be radially and/or axially misaligned in substantially the same manner as fittings  14 ,  16  described above.  FIG. 10  shows a misaligned fitting  100  as it is being inserted into socket  102 , and before any contact is made between fitting  100  and socket  102 . It will be seen that the diameter of the mouth  128  of socket  102  is sufficiently large that the first contact will be between the curved side of head  106  above the O-ring  118  and the chamfer of the lower portion  122  of socket  102 . Thus, the diameter of mouth  128  is greater than the diameter of head  106  at its upper edge  114 , plus the maximum diametrical position tolerance of the head  106 . In the illustrated embodiment, the diametrical position tolerance of the head  106  is somewhat less than the maximum tolerance. 
       FIG. 11  shows the contact between the chamfer of lower portion  122  of socket  102  and the upper portion  107  of head  106 . As the head  106  slides over the surface of lower portion  122 , it can be seen that the head  106  of fitting  100  is guided inwardly and upwardly toward the sealing surface  124  as it is being centered and tilted toward vertical. As shown in  FIG. 11 , there is no contact between the O-ring  118  and the lower portion  122  of socket  102 . 
       FIG. 12  shows further insertion of fitting  100 , wherein the upper portion  107  of head  106  reaches the bottom edge  126  of the upper portion  120  of socket  102 , and the upper edge  114  of head  106  commences its entry into the upper portion  120  of socket  102 . At this point there is still no contact between the O-ring  118  and the lower portion  122  of socket  102 . 
       FIG. 13  shows the point at which the O-ring  118  first contacts the inner surface of socket  102 , in the vicinity of the bottom edge  126  of upper portion  120 . Beyond this point, the O-ring  118  slides along the sealing surface  124  as it continues to be inserted into socket  102 , as shown in  FIG. 14 . At this point, the fitting  100  may still be axially misaligned, however, the spherical contour and the height of the O-ring  118  allow it to maintain robust sealing contact with sealing surface  124 , even though it may remain misaligned relative to the vertical axis by as much as about 5 degrees. 
     In  FIGS. 10-14  the resilient sealing element of fitting  100  comprises an O-ring  118  having cross-section which is circular in an axial plane. In order to maintain robust contact between the sealing element and the sealing surface  124  of socket  102 , the O-ring of  FIGS. 10-14  may be replaced by a resilient sealing element in the form of a custom shaped resilient sealing ring  130 , also referred to herein as “gland  130 ”, as shown in  FIG. 15 . 
     The gland  130  has an outer sealing surface  132  which is rounded when viewed in cross-section in an axial plane as shown in  FIG. 15 . The rounding of sealing surface  132  allows the fitting  100  to rotate or roll over the surfaces of the socket  102  as the fitting  100  is inserted into socket  102 . In the illustrated embodiment, the outer sealing surface  132  has a truncated spherical shape in axial cross-section, and has a slightly larger radius than the remainder of the head  106 , so that the outer sealing surface  132  is proud of the upper portion  107  and the lower portion  109  of head  106 . 
     In the fitting  100  shown in  FIG. 15 , the groove  116  in head  106  has a rectangular cross-sectional shape in an axial plane, and the inner portion  134  of gland  130  similarly has a rectangular profile so that it fits snugly into groove  116 . 
     It can be seen that the gland  130  has a height (the axial distance between the top and bottom of groove  116  or inner portion  134 ) which may be greater than that of O-ring  118 . This provides the head  106  with a greater sealing surface  132  to ensure robust contact with the sealing surface  124  of socket  102 , and allows a seal to be maintained in the event that there is significant tilting of the fitting  100  relative to the vertical (axial) direction. For example, the height of gland  130  may be greater than 50% of the height of the head  106 , measured axially between the lower edge  112  and upper edge  114  of head  106 . 
     It will be appreciated that the head  106  of fitting  100  may be modified without departing from the invention, particularly where the resilient sealing element comprises gland  130 . For example, as shown in  FIG. 16 , the spherical profile of the lower portion  109  of head  106  may be eliminated because this portion of head  106  does not make contact with the interior surfaces of  102  during insertion of the fitting  100 . For example, as shown in  FIG. 16 , the lower portion  109  of head  106  may be provided with a vertical, cylindrical surface and may have the same diameter as the outer surface of base portion  104 , such that the lower portion  109  of  106  appears as a continuation of the base portion  104 . Alternatively, the lower portion  109  of head  106  may be chamfered instead of rounded, so long as the chamfer does not extend outwardly past the outer sealing surface  132  of gland  130 . 
     Similarly, the upper portion  107  of head  106  does not necessarily have a continuously rounded profile as shown in  FIGS. 10-15 , but may instead include a chamfer  136  extending downwardly and outwardly from the upper edge  114 , for example as shown in  FIG. 16 . The upper portion  107  of head  106  may also include a vertical portion  138  as shown in  FIG. 16 , extending from the base of chamfer  136  to the top of groove  116 . However, it will be appreciated that this vertical portion  138  may be eliminated if the chamfer  136  extends throughout the entire height of upper portion  107 , or if the area between the chamfer  136  and groove  116  maintains its rounded shape as in  FIGS. 10-15 . Regardless of its shape, however, no portion of upper portion  107  extends outwardly past the outer sealing surface  132  of gland  130 . 
     Although the invention has been described in connection with certain embodiments, it is not restricted thereto. Rather, the invention includes all embodiments which may fall within the scope of the following claims.