Abstract:
A tubular heat exchanger preferably of a multi-pass design, has a cylindrical shell with open ends that are releasable covered and sealed by preferably two end caps. Located removably in the shell and axially between the end caps is a core having a plurality of outer tubes and preferably a plurality of inner tubes with each one of the inner tubes extending through a respective one of the outer tubes. A plurality of perforated plates disposed in the shell are sealed releasably to respective ends of the inner and outer tubes thereby forming a plurality of liquid tight chambers for the flow of a plurality of segregated mediums and the transfer of heat therebetween.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a tubular heat exchanger, and more particularly to a multi-pass, tubular, heat exchanger with a servicable core for marine applications. 
       BACKGROUND OF THE INVENTION 
       [0002]    Tubular heat exchangers are known to flow two fluid mediums of different temperatures to transfer heat from one fluid to the other. Such heat exchangers generally have an outer shell that houses a central core having a plurality of tubes for transferring heat. The first ends of the tubes are supported by a perforated first plate sealed continuously to an inward face of the shell. The opposite second ends of the tubes are supported by a perforated second plate also sealed continuously to the inward face of the shell, thus defining a mid chamber between the plates for the flow of a first fluid medium. An inlet chamber for the flow of a second fluid is defined by the first plate and a first end of the shell, and an outlet chamber is defined by the second plate and an opposite second end of the shell. The second fluid flows from the inlet chamber, through the tubes and into the outlet chamber. 
         [0003]    The first fluid flowing through the mid chamber generally envelopes the tubes for heat transfer through the tube walls and to the second fluid flowing through the tubes. For efficient heat transfer, the tubes are typically made of copper or a copper alloy. To maintain fluid segregation, each end of each tube must be reliably sealed to the respective first and second plates. Traditionally, this seal is created by an expensive brazing procedure between the copper tubes and the plates. Because of this brazing, the first and second plates must also be of a copper alloy. 
         [0004]    During operation of the heat exchanger, thermal expansion and contraction is known to cause stress cracks between various brazed seals causing a loss of seal integrity. Moreover, known assembly methods limit the ability to feasibly manufacture a multi-pass, tubular, heat exchanger having multiple inlet and outlet chambers, thus the ability to control cooling or heating rates as a function of multiple fluid temperatures is limited. Yet further, known brazing techniques limit or prevent cost effective maintenance and replacement of individual parts of the heat exchanger core. Such ability is particularly needed where fluids tend to be corrosive, or in marine applications that use seawater as a coolant that is not only corrosive but may encourage marine growth and sediment build-up inside the heat exchanger. 
       SUMMARY OF THE INVENTION 
       [0005]    A tubular heat exchanger preferably of a multi-pass design, has a substantially cylindrical shell with open ends that are releasable covered and sealed by end caps. Located removably in the shell and axially between the end caps is a core having a plurality of outer tubes and preferably a plurality of inner tubes with each one of the inner tubes extending through a respective one of the outer tubes. A plurality of perforated plates located in the shell are sealed releasably to respective ends of the inner and outer tubes thereby forming a plurality of liquid tight chambers for the flow of a plurality of segregated mediums and the transfer of heat therebetween. 
         [0006]    Preferably, end portions of the plurality of outer and inner tubes are supported by and sealed releasably to the respective plates. The end portions project through bores in the plates and may be sealed to the plates by at least one circumferentially continuous gasket located in a counter bore of each one of the bores for radial compression between the plate and the end portion of the tube. Each one of the plates has a peripheral circumferential surface facing radially outward that preferably defines a continuous groove for seating a circumferentially continuous gasket that compresses radially between the continuous surface and an inward circumferential face of the shell. 
         [0007]    Objects, features and advantages of the present invention include a heat exchanger capable of operating with a wide and versatile range of heat transfer profiles and that has a removable core for maintenance and easy replacement of individual tubes and other components. Other advantages include the omission of expensive manufacturing processes such as brazing, the ability to use non-corrosive, light weight and relatively inexpensive components such as plastic, a relatively simple and robust design and a long and useful life. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0008]    These and other objects, features and advantages of this invention will be apparent from the following detailed description, appended claims, and accompanying drawings in which: 
           [0009]      FIG. 1  is a perspective view of a tubular heat exchanger embodying the present invention and illustrated in a marine engine application; 
           [0010]      FIG. 2  is a side view of the tubular heat exchanger; 
           [0011]      FIG. 3  an end view of the tubular heat exchanger; 
           [0012]      FIG. 4  is a perspective cross section of the tubular heat exchanger with components removed to show internal detail and generally taken along line  4 - 4  of  FIG. 3 ; 
           [0013]      FIG. 5  is a perspective cross section of the tubular heat exchanger with components removed to show internal detail and generally taken along line  5 - 5  of  FIG. 3 ; 
           [0014]      FIG. 6  is a perspective view of the tubular heat exchanger with a cylindrical shell removed to show internal detail; 
           [0015]      FIG. 7  is a perspective view of a core of the tubular heat exchanger; 
           [0016]      FIG. 8  is an enlarged partial and perspective cross section of the tubular heat exchanger with the same internal components removed and taken from circle  8  of  FIG. 4 ; 
           [0017]      FIG. 9  is an enlarged partial and perspective cross section of the tubular heat exchanger taken from circle  9  of  FIG. 8 , but without any internal components removed; 
           [0018]      FIG. 10  is an enlarged partial and perspective cross section of the tubular heat exchanger taken from circle  10  of  FIG. 8 ; 
           [0019]      FIG. 11  is a cross section of an end cap of the heat exchanger; 
           [0020]      FIG. 12  is an exploded perspective view of a perforated outward plate of the core of the heat exchanger; 
           [0021]      FIG. 13  is a partial cross section of the outward plates; and 
           [0022]      FIG. 14  is a partial cross section of a perforated inward plate of the core of the heat exchanger and similar in perspective to  FIG. 13 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    Although the following text sets forth a detailed description of numerous different embodiments of the invention, it should be understood that the legal scope of the invention is defined by the words of the claims set forth at the end of this patent. The detailed description is to be construed as exemplary only, and does not describe every possible embodiment of the invention because such would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims defining the invention. 
         [0024]    It should also be understood that, unless a term is expressly defined in this patent using the sentence “As used herein, the term ‘______’ is hereby defined to mean . . . ” or a similar sentence, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to in this patent in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term be limited, by implication or otherwise, to that single meaning. Finally, unless a claim element is defined by reciting the word “means” and a function without the recital of any structure, it is not intended that the scope of any claim element be interpreted based on the application of 35 U.S.C. § 112, sixth paragraph. 
         [0025]    Referring now to  FIG. 1  of the drawings, a tubular heat exchanger or cooler  20  embodying the present invention is illustrated as part of a preferred marine combustion engine assembly  22 . The assembly  22  has a combustion engine  24 , preferably two water cooled exhaust manifolds  26 , a coolant pump  28 , and an oil pump (not shown) preferably housed within an oil pan  30  of the engine  24 . The heat exchanger  20  generally interacts with an open liquid coolant loop  32  that preferably flows lake or sea water, a closed coolant loop  34  that preferably flows a rust inhibiting coolant such as glycol for cooling the engine, and a closed oil loop  36  that removes heat and lubricates the engine  24 . The heat exchanger  20  preferably functions to cool the engine oil via the engine glycol, and the engine glycol is cooled by the lake or seawater flowing through the open loop  32 . 
         [0026]    Preferably, a coolant pump  40  positioned in an inlet leg  38  of the open loop  32  flows coolant/water from an open body of seawater to the heat exchanger  20 . The pump  40  may be mechanically powered by the operating engine  24 , but preferably is operated by a variable speed electric motor and a control system (not shown) that senses various parameters such as oil temperature and glycol temperature and thereby adjusts the speed of pump  40  to optimize engine performance. An outlet leg  42  of the open loop  32  preferably tees-off to flow heated seawater through respective exhaust manifolds  26 , known in the marine industry, before being expelled back into the open sea. 
         [0027]    Referring to  FIGS. 1-4 , the heat exchanger  20  has a substantially cylindrical shell  46  extending longitudinally along a centerline  47  and between opposite ends  48 ,  50  where respective inlet and outlet nozzles  52 ,  54  are generally located for the flow of engine oil or lubricant delivered by the oil pump of the engine  24 . Preferably, the ends  48 ,  50  of the shell  46  are circular openings and the nozzles  52 ,  54  are a unitary part of respective end caps  56 ,  58  that releasably seal to the cylindrical shell  46 . Inlet and outlet ports  60 ,  62  are in the shell  46  and may be defined by radially outward projecting nipples  64 ,  66  of the shell  46  for coolant flow of the closed loop  34 . Preferably, the nipples  64 ,  66  are spaced axially inward from adjacent respective ends  48 ,  50 . Inlet and outlet orifices  68 ,  70  are in the shell  46  and may be defined by radially outward projecting nipples  72 ,  74  of the shell  46  for the coolant (seawater) flow of the open loop  32 . Preferably, the nipples  72 ,  74  are spaced axially inward from adjacent respective nipples  64 ,  66  of the shell  46 . With the centerline  47  being substantially horizontal, all of the nipples  64 ,  66 ,  72 ,  74  preferably project upward to prevent air from being trapped inside the heat exchanger  20 . Each nipple  64 ,  66 ,  72 ,  74  preferable has a circumferentially continuous barb  76  projecting radially outward for snugly and sealably fitting to resiliently flexible hoses (not shown) of respective loops  32 ,  34 . 
         [0028]    Referring to  FIGS. 4-7 , a core  78  of the heat exchanger  20  fits sealably inside the shell  46  and is easily removable for cleaning, maintenance and/or replacement of internal components. This ability to inspect and maintain the core  60  is particularly advantageous in marine applications where the flow of salt water tends to be corrosive for some materials and the likelihood of marine growth and other deposits that reduce cooling efficiency is relatively high (e.g. barnacles). The removable core  78  of the heat exchanger  20  has a pair of perforated outward plates  80 ,  82  located axially inward from respective end caps  56 ,  58 , a pair of perforated inward plates  84 ,  86  spaced axially inward from respective outward plates  80 ,  82  and a plurality of perforated diverter plates  88  spaced axially away from one-another and spaced axially inward from the inward plates  84 ,  86 . 
         [0029]    The heat exchanger  20  has inlet and outlet chambers  90 ,  92  defined axially between respective end caps  56 ,  58  and respective outward plates  80 ,  82  for the flow of oil, inlet and outlet chambers  94 ,  96  defined axially between respective outward plates  80 ,  82  and respective inward plates  84 ,  86  for the flow of glycol, and a mid chamber  98  defined axially between the inward plates  84 ,  86  for the flow of seawater that is generally diverted by the diverter plates  88  located in the mid chamber  98 . The chambers  94 ,  96 ,  98  are also defined radially by an inward face  100  of the shell  46 . The ports  60 ,  62  communicate directly with respective inlet and outlet chambers  90 ,  92 , and the orifices  68 ,  70  both communicate with the mid chamber  98 , but adjacent to respective inward plates  84 ,  86  with the diverter plates  88  positioned axially between the orifices  68 ,  70 . 
         [0030]    Referring to  FIGS. 6-10 , the core  78  of the heat exchanger  20  has a plurality of outer tubes  102  for the flow of coolant or glycol of the closed loop  34 . Each tube  102  is substantially parallel to the centerline  47  and has a mid portion  104  that extends through the mid chamber  98 . As best shown in  FIG. 9 , each tube  102  has opposite, distal, end portions  106  that project through respective inward plates  84 ,  86  and partially into respective inlet and outlet chambers  94 ,  96 . Preferably, the mid portion  104  of each tube  102  has a diameter that is greater than a diameter of the end portions  106 . This difference in diameters forms an annular stop  108  that faces and may abut respective inward plates  84 ,  86  for maintaining a predetermined distance between the plates  84 ,  86 . 
         [0031]    The core  78  has a plurality of inner tubes  110  for flow of oil of the closed loop  36 . Each inner tube  110  extends through a respective outer tube  102  and through the mid chamber  98  and through the inward chambers  94 ,  96 . Each tube  110  has opposite, distal, end portions  112  that project through respective outward plates  80 ,  82  and partially into respective inlet and outlet chambers  90 ,  92 . Together, the outer and inner tubes  102 ,  110  define a channel  114  that has an annular cross section for the flow of coolant or glycol, and alone the inner tube  110  defines a channel  115  that has a round cross section preferably for the flow of oil. 
         [0032]    Referring to  FIGS. 8 ,  10  and  11 , the end caps  56 ,  58  are preferably identical for reducing the required number of parts and reducing manufacturing costs. Each cap is preferably made of heat resistant, injection molded plastic. The respective nozzles  52 ,  54  are contoured to accept a fitting  116  for attachment to the oil loop  36 . Preferably, the fitting  116  is of a threaded, metallic or brass, quick connect or compression variety. Each cap  56 ,  58  also has a circumferentially continuous collar  118  having an annular surface  119  that faces the respective outward plates  80 ,  82 , a circumferential inner surface  120  that generally radially defines the inlet and outlet chambers  90 ,  92 , and a circumferential outer surface  122  that faces and preferably is in contact with the inner face  100  of the shell  46 . The outer surface  122  defines a circumferentially continuous groove  124  in the collar  116  for seating a resiliently compressible gasket or o-ring  126  for providing a liquid tight seal radially between the end caps  56 ,  58  and the shell  46 . 
         [0033]    Referring to  FIGS. 10 ,  12  and  13 , the outward plates  80 ,  82  are preferably identical for reducing the required number of parts and reducing manufacturing costs. Each outward plate  80 ,  82  is preferably made of injection molded plastic, and when assembled, is orientated substantially perpendicular to centerline  47 . Each plate  80 ,  82  has an outer and an opposite inner face  128 ,  130 . The outer face  128  defines in-part the chambers  90 ,  92  and the inner face  130  defines in-part the chambers  94 ,  96 . Preferably, the periphery of the outer face  128  of the outward plates  80 ,  82  is in contact with the annular surface  119  of the collar  118  of respective end caps  56 ,  58  for axial spacing with respect to centerline  47 . Similar to the end caps  56 ,  58 , the outward plates  80 ,  82  each have a circular edge or peripheral surface  132  that faces radial outward and toward the inner face  100  of the shell  46 . The peripheral surface  132  defines a circumferentially continuous groove  134  for seating a resiliently compressible gasket or o-ring  136 . The o-ring  136  provides a liquid tight seal radially between the outward plates  80 ,  82  and the shell  46 . 
         [0034]    The two end portions  112  of each one of the inner tubes  110  extends through a bore  138  in the respective outward plates  80 ,  82 . Each bore  138  communicates through both the outer and inner faces  128 ,  130  of the plates  80 ,  82 , and has a counter bore  140  that communicates through the inner face  128  only. The diameter of the bore  138  at the outer face  128  is substantially equal to or slightly greater than the diameter of the end portions  112  of the inner tube  110 . The counter bore  140  generally seats two resiliently flexible o-rings  142 ,  144 , a rigid spacer ring  146  and a retainer  148 . The first o-ring  142  is located at the bottom of the counter bore  140 . The spacer ring  146  is located axially between the two o-rings  142 ,  144 , and the retainer  148  is located axially between the o-ring  144  and inner face  130  and press fitted to the plates  80 ,  82 . Both the spacer ring  146  and the retainer  148  are preferably made of plastic. 
         [0035]    Referring to  FIGS. 9 and 14 , the inward plates  84 ,  86  are preferably identical for reducing the required number of parts and reducing manufacturing costs. Each inward plate  84 ,  86  is preferably made of injection molded plastic, and when assembled, is orientated substantially perpendicular to centerline  47 . Each plate  84 ,  86  has an outer and an opposite inner face  150 ,  152 . The outer face  150  defines in-part the chambers  94 ,  96  and the inner faces  152  axially define the mid chambers  98 . Similar to the end caps  56 ,  58 , the inward plates  84 ,  86  each have a circular edge or peripheral surface  154  that faces radial outward and toward the inner face  100  of the shell  46 . The peripheral surface  154  defines a circumferentially continuous groove  156  for seating a resiliently compressible gasket or o-ring  158 . The o-ring  158  provides a liquid tight seal radially between the inward plates  84 ,  86  and the shell  46 . 
         [0036]    The two end portions  106  of each one of the outer tubes  102  extends through a bore  160  in the respective outward plates  84 ,  86 . Each bore  160  communicates through both the outer and inner faces  150 ,  152  of the plates  84 ,  86 , and has a counter bore  162  that communicates through the inner face  152 , but not the outer face  150 . The diameter of the bore  160  at the outer face  152  is substantially equal to or slightly greater than the diameter of the end portions  106  of the outer tube  102 . The counter bore  162  generally seats two resiliently flexible o-rings  164 ,  166 , a rigid spacer ring  168  and a retainer  170 . The first o-ring  164  is located at the bottom of the counter bore  162 . The spacer ring  168  is located axially between the two o-rings  164 ,  166 , and the retainer  170  is located axially between the o-ring  166  and inner face  152  and press fitted to the plates  84 ,  86 . Both the spacer ring  168  and the retainer  170  are preferably made of plastic. 
         [0037]    A spacer member or plurality of pins  174  of the core  78  extend axially between each one of the outward plates  80 ,  82  and the respective inward plates  84 ,  86  to maintain a predetermined axial distance with respect to centerline  47 . A plurality of blind bores  172  (see  FIGS. 8 and 9 ) in each one of the inward plates  84 ,  86  communicates through a peripheral portion of the outer face  150 . Each one of a plurality of pins  174  has a first end  176  press fitted into a respective one of the bores  172 . The pins  174  project axially outward to opposite distal ends  178  that contact or abut the inner face  130  of the outward plates  80 ,  82  for spacing the inward plates  84 ,  86  from the respective outward plates  80 ,  82  and thus maintaining a predetermined volume of the chambers  94 ,  96 . As illustrated, there are preferably six pins  174  spaced circumferentially away from one another with respect to centerline  47  and projecting axially outward from each inward plate  84 ,  86 . One skilled in the art, however, would now know that the pins could be made of any non-corrosive material having sufficient rigidity, or the pins and the inward plate could be molded as one unitary component. Moreover, the pins  174  could project from the outward plates  80 ,  82  as oppose to the inward plates  84 ,  86  and/or need not be pins at all but may take the form of any variety of shapes capable of spacing the plates away from one-another while not blocking coolant flow through the ports  60 ,  62 . 
         [0038]    Referring to  FIGS. 4-7 , the diverter plates  88  are perforated similarly to the inward plates  84 ,  86  for receipt of the outer tubes  102 . Unlike plates  84 ,  86 , the diverter plates are half circles or half of an otherwise circular disc having a curved edge that fits slideably against the inner face  100  and a straight edge that generally intersects the centerline  47 . As previously described, the diverter plates  88  are in the mid-chamber  98  and are axially spaced from one another. Because adjacent plates  88  are also opposed to one another, flow of the seawater through the mid chamber  98  is diverted for improved cooling efficiency. The plates  88  also contribute toward structural rigidity of the core  78  and the outer tubes  102 . 
         [0039]    Preferably, the o-rings  126 ,  136 ,  158 ,  142 ,  144 ,  164 ,  166  are made of a resiliently flexible, rubber-like, material that is heat resistant such as viton. The inner and outer tubes  110 ,  102  are preferably made of metal having a high heat transfer coefficient and that is resistant to corrosion and marine growth such as copper or cupronickel. Preferably and for structural strength, the shell  46  is also made of copper or cupronickel. Unlike traditional heat exchangers, galvanic reaction concerns between various metal components is alleviated because of the plastic and o-ring components of the present heat exchanger as previously described. Moreover, any concerns with stress cracking is also alleviated because of the absence of brazing the tubes. The o-rings of the heat exchanger  20  not only provide the sealing function of traditional brazing but also permit thermal expansion and contraction between components made of different materials. 
         [0040]    During assembly of the heat exchanger  20 , the o-rings  164 ,  166 , spacer ring  168  and retainer  170  are premounted in the counter bores  162  and the o-ring  158  is preferably preseated in the groove  152  of the inward plates  84 ,  86 . Similarly, the o-rings  142 ,  144 , spacer ring  146  and retainer  148  are premounted in the counter bores  140  and the o-ring  136  is preferably preseated in the groove  124  of the outward plates  80 ,  82 . The ends  176  of the spacer member or pins  176  may then be press fitted into respective blind bores  172  in the plates  84 ,  86 . 
         [0041]    The mid portion  104  of the outer tubes  102  are then inserted through and generally seated to the diverter plates  88 . The end portions  106  of the outer tubes  102  are then inserted through the bores  160  with the inner surfaces  152  of the plates  84 ,  86  opposing one-another. During this insertion, the o-rings  164 ,  166  resiliently compress about the end portions  106  for a liquid tight seal. This insertion preferably ceases when the annular stops  108  abut or come in near contact with the respective retainers  148 . 
         [0042]    The inner tubes  110  are then inserted through each respective one of the outer tubes  102  and the end portions  112  are of the inner tubes  110  are then inserted through the bores  138  with the inner surfaces  130  of the outward plates  80 ,  82  opposing one-another. During this insertion, the o-rings  142 ,  144  resiliently compress about the end portions  112  for a liquid tight seal. This insertion generally ceases when the distal ends  178  of the spacer pins  174  abut the inner surfaces  130  of the outward plates  80 ,  82 . 
         [0043]    With the core  78  preassembled, it may then be slid axially into the shell  46  from either of the openings defined by the ends  48 ,  50 . Preferably, the ends  48 ,  50  are flared radially outward for easy insertion of the core  78 . When the core  78  is axially moved into the shell  46 , the o-rings  136 ,  158  are first cleared by either of the open ends  48 ,  50  and then compress against the inner face  100  of the shell  46 . Because of the symmetrical design of the core  78 , rotationally indexing the core  78  with respect to the centerline  47  and with respect to the shell  46  is not required. With the core  78  axially centered in the shell  46 , the end caps  56 ,  58  with the preseated o-rings  126  are press fitted to the respective ends  48 ,  50 . Contact of the annular surface  119  of the end caps  56 ,  58  with the outer face  128  of the respective outward plates  80 ,  82  assures that the core  78  is properly centered. 
         [0044]    The angular position of the nozzles  52 ,  54  may then be independently adjusted by rotating the respective end caps  56 ,  58  about the centerline  47 . Once adjusted, a plurality of threaded fasteners  180  are inserted through holes in the ends  48 ,  50  of the shell  46  and threaded into the end caps  56 ,  58 . With the fasteners  180  engaged, the end caps  56 ,  58  are prevented from shifting axially. One skilled in the art, however, would now know that the end caps may releasably engage the shell  46  in a variety of ways. For instance, the caps  56 ,  58  may carry threads that threadably engage threads carried by the shell  46 , thus fasteners would not be required. In this embodiment, the o-rings  126  can be compressed axially as oppose the illustrated radial compression. In yet another modification, the caps may be clamped to the shell  46 . 
         [0045]    During disassembly of the heat exchanger  20  for inspection and maintenance reasons, both end caps  56 ,  58  may be removed. With both ends of the shell  46  open, the core  78  can be pushed at one end and pulled out from the other. This technique is particularly advantageous if sediment build-up has occurred within the heat exchanger  20  that may otherwise make pulling of the core  78 , from one end alone, difficult. 
         [0046]    While the forms of the invention herein disclosed constitute a presently preferred embodiment, many others are possible. For instance, although the heat exchanger is generally described as a cooler, it could also function as a heater. Moreover, the liquid coolants (e.g. glycol and seawater) and oil may be any other form of a flowable medium and is not limited to liquids alone. Yet further, although the embodiment described entails three flowing mediums, the same novel aspects can be applied to heat exchangers having two, four or more flowing mediums. It is not intended herein to mention all the possible equivalent forms or ramifications of the invention. It is understood that terms used herein are merely descriptive, rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention.