Patent Publication Number: US-11656036-B2

Title: Heat exchanger and associated tube sheet

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 62/818,426 which was filed on Mar. 14, 2019 and is incorporated herein by reference. 
    
    
     BACKGROUND 
     Heat exchangers generally include many tubes that extend through a body portion to transfer heat from the fluid traveling inside the tubes and the fluid located inside the body portion. Due to the size of some heat exchangers, it is necessary to support the tubes inside the body portion to prevent or reduce movement of the plurality of tubes during operation. One way of supporting the tubes extending through the heat exchanger is with a tube sheet. Tube sheet includes a plurality of holes that accept a corresponding one of the tubes. To allow the tubes to be installed within the tube sheet, the holes in the tube sheet are larger than the tubes and a mechanical fastener or swaging process is used to secure the tubes to the tube sheet to support the tubes. 
     SUMMARY 
     In one exemplary embodiment, a heat exchanger includes a body portion and a pair of end plates at least partially forming an enclosure with the body portion. A plurality of tubes extend through at least one of the body portion and the pair of end plates. At least one tube sheet includes a plurality of openings with a corresponding one of the plurality of tubes located in one of the plurality of openings. The tube sheet is made of a material which expands in the presence of refrigerant. 
     In a further embodiment of the above, the heat exchanger is a non-baffled heat exchanger. 
     In a further embodiment of any of the above, the tube sheet is formed of a single unitary piece of material. 
     In a further embodiment of any of the above, the at least one tube sheet includes refrigerant expanding material extending uninterrupted between adjacent openings of the plurality of openings. 
     In a further embodiment of any of the above, the tube sheet at least partially follows an inner contour of the body portion. 
     In a further embodiment of any of the above, the tube sheet extends between 20% and 90% of a diameter of the body portion. 
     In a further embodiment of any of the above, the tube sheet at least partially follows an inner contour of the body portion. 
     In a further embodiment of any of the above, the body portion includes a first refrigerant port and a second refrigerant port. At least one tube sheet includes a plurality of tube sheets. 
     In a further embodiment of any of the above, a support structure supports the tube sheet. 
     In a further embodiment of any of the above, the support structure includes a plurality of rods forming a matrix. 
     In a further embodiment of any of the above, at least one tube sheet is formed from a plurality of geometric shaped members. Each of the plurality of geometric shaped members includes one of the plurality of openings. Each of the plurality of geometric shaped members are made of a single unitary piece of material. 
     In a further embodiment of any of the above, the plurality of tubes include heat transfer enhancing features on an exterior surface that engage the at least one tube sheet. 
     In another exemplary embodiment, a method of operating a heat exchanger comprising the step of supporting a plurality of tubes that extend through a corresponding one of a plurality of opening in a tube sheet. The tube sheet is placed in contact with a refrigerant. The tube sheet expands in response to contact with the refrigerant entering the heat exchanger and contacts the plurality of tubes. 
     In a further embodiment of any of the above, the plurality of tubes include heat transfer enhancing features on an exterior surface that engage the tube sheet. 
     In a further embodiment of any of the above, the plurality of tubes sheets are made of a single unitary piece of refrigerant expanding material. 
     In a further embodiment of any of the above, the tube sheet extends between 20% and 90% of a diameter of a body portion of the heat exchanger. 
     In a further embodiment of any of the above, the tube sheet includes a plurality of geometric shapes assembled together to form the tube sheet. 
     In a further embodiment of any of the above, a support structure supports the tube sheet. 
     In a further embodiment of any of the above, vibrations and movement of the plurality of tubes are reduced with the tube sheet in contact with the refrigerant. 
     In a further embodiment of any of the above, the heat exchanger is a non-baffled heat exchanger. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates an example heat exchanger. 
         FIG.  2    illustrates a sectional view of the heat exchanger taken along line  2 - 2  of  FIG.  1    showing a tube sheet. 
         FIG.  3    illustrates an enlarged view of a portion of  FIG.  2   . 
         FIG.  4    illustrates the sectional view of  FIG.  2    with refrigerant in the heat exchanger. 
         FIG.  5    illustrates an enlarged view of a portion of  FIG.  4   . 
         FIG.  6    illustrates a sectional view taken along line  6 - 6  of  FIG.  2    showing multiple tube sheets. 
         FIG.  7    illustrates another example tube sheet. 
         FIG.  8    illustrates yet another example tube sheet. 
         FIG.  9    illustrates an example locking mechanism for assembling individual body portions. 
         FIG.  10    illustrates an enlarged view of another example opening in the tube sheet. 
         FIG.  11    illustrates the tube sheet of  FIG.  10    in an expanded state. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    illustrates an example heat exchanger  20 , such as an evaporator or a condenser, used in a refrigeration system or other device for transferring heat between multiple fluids. The heat exchanger  20  includes a body portion  22  enclosed by a pair of end plates  24 . A plurality of tubes  28  extend through the enclosure defined by the body portion  22  and the pair of end plates  24 . A water box  25  encloses the end plates  24  to provide fluid into or out of the plurality of tubes  28 . The plurality of tubes  28  are fluidly sealed with a corresponding one of the pair of end plates  24  to prevent fluid from leaving the heat exchanger  20  between the plurality of tubes  28  and the corresponding end plate  24  that the tubes  28  extend through. 
     Refrigerant enters the heat exchanger  20  through either a first port  26 A or a second port  26 B and exits the heat exchanger  20  through the other of the first port  26 A or the second port  26 B. In the illustrated example, the first and second ports  26 A,  26 B are located on opposite sides of the heat exchanger  20 . Although only a single first port  26 A and a single second port  26 B are shown in the illustrated example, there could be multiple first ports  26 A and second ports  26 B and the first ports  26 A and the second ports  26 B could be located in other portions of the heat exchanger  20 , such as the pair of ends plates  24 . 
       FIG.  2    illustrates a sectional view of the heat exchanger  20  taken along line  2 - 2  of  FIG.  1   . As shown in  FIG.  2   , the body portion  22  at least partially forms an internal cavity  30  with the end plates  24  (see  FIG.  1   ). In the illustrated example, the body portion  22  includes a circular cross section. However, the body portion  22  is not limited to having a circular cross-section and could form other cross-sectional shapes, such as squares, rectangles, or ovals. 
     The plurality of tubes  28  are at least partially supported by a tube sheet  32 . The tube sheet  32  includes an outer perimeter  32 A that at least partially follows an inner contour  22 A of the body portion  22 . The tube sheet  32  could be attached to the body portion  22  through a mechanical connection, such as a fastener or adhesive, or be friction fit against the inner contour  22 A to allow some movement of the tube sheet  32 . In the illustrated example, the tube sheet  32  extends between 60% and 70% of a diameter of the body portion  22  to provide a region of the internal cavity  30  that is unobstructed by the tube sheet  32 . In another example, the tube sheet  32  could extend anywhere from 20% up to 90% of the diameter of the body portion. Additionally, the tube sheet  32  could be located inward from opposing sides of inner contour  22 A of the body portion  22  such that there is an unobstructed region of the internal cavity  30  on opposite sides of the tube sheet  32 . 
     The tube sheet  32  can be made of an expandable material that is formed from a single unitary piece of material. The expandable material includes a material which will swell or expand in the presence of a working fluid, such as a refrigerant. For example, the expandable material expands in the presence of the working fluid by a process that includes at least one of adsorption of molecules of the working fluid onto the expandable material (e.g., onto the wettable surface) or diffusion of the working fluid into the expandable material. The expandable material can include a polymer material, for example, Nylon (e.g., Nylon 6,6), polytetrafluoroethylene (PTFE), polyimide, polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyamide-imide (PAI). The expandable material can optionally further include a filler material, for example, glass fiber, carbon fiber, basalt fiber, aramid fiber or the like. The expandable material can include 0 weight % (wt %) to 90 wt % filler material. The tube sheet  32  can be formed from a single piece of material through either casting the material in a die or machining a sheet of the material to the desired profile to accommodate the plurality of tubes  28  and the shape of the inner contour  22 A. The working fluid can include R744 (CO2), R410a, R1234zd, R290 (propane), R1224yd, R1123, R1234ze, or another similar working fluid. 
     In the illustrated example, the tube sheet  32  includes a plurality of openings  34  that each have a diameter D 1 . The diameter D 1  is larger than an outer diameter DT of each of the plurality of tubes  28  (see  FIG.  3   ). The difference in length between the diameter D 1  and the diameter DT creates a spacing between the plurality of tubes  28  and a corresponding one of the openings  34 . The spacing formed between the plurality of tubes  28  and the corresponding one of the openings  34  allows for the plurality of tubes  28  to easily pass through the tube sheet  32  during assembly of the heat exchanger  20 . 
       FIGS.  4  and  5    illustrate the tube sheet  32  in an expanded state when exposed to refrigerant. Refrigerant is introduced into the heat exchanger  20  through one of the first and second ports  26 A or  26 B and exits the heat exchanger  20  through the other of the first and second ports  26 A or  26 B. The refrigerant entering and exiting the heat exchanger  20  through the first and second ports  26 A,  26 B can be in at least one of a liquid state, a vapor state, or a two-phase state. 
     When the tube sheet  32  is in an expanded state, the diameter D 1  of the openings  34  decreases to close the spacing between the openings  34  and the outer diameter of the corresponding one of the plurality of tubes  28 . This brings the tube sheet  32  into at least partial contact with the plurality of tubes  28  to stabilize the plurality of tubes  28  to prevent damage resulting from vibrations or movement during operation of the heat exchanger  20 . The tube sheet  32  can also include passages  35  extending through a mid-portion of the tube sheet  32  or edge passages  37  at least partially defined by the tube sheet  32  and the body portion  22 . 
     Also, the expanding properties of the tube sheet  32  in response to exposure to refrigerant eliminates the need for additional mechanical attachment between the tube sheet  32  and the plurality of tubes  28 . By eliminating the need for additional mechanical attachment between tube sheet  32  and the plurality of tubes  28 , the amount of time required to manufacture the heat exchanger  20  is greatly reduced due to a number of mechanical attachments between the plurality of tubes  28  and the tube sheet  32  and the level of precision needed to make those attachments. 
     Also, by eliminating the need for mechanical attachments between the tube sheet  32  and the plurality of tubes  28 , such as swaging or using fasteners, the plurality of tubes  28  can include heat enhancing features  40  over the entire length of the tubes  28 . This increases the heat transfer between the refrigerant in the internal cavity  30  and the fluid passing through the tubes  28 . Also, as shown in  FIG.  5   , the tube sheet  32  has expanded such that the opening  34  contacts the tube  28  to provide support for the tube. 
       FIGS.  10  and  11    illustrate another example opening  34 A in the tube sheet  32 . The opening  34 A is irregular in shape and includes a plurality of projections. When the tube sheet  32  is placed in contact with refrigerant, the tube sheet  32  expands and contacts the tube  28  ( FIG.  11   ) to prevent the tube  28  from moving or vibration during operation of the heat exchanger  20 . The projections in the opening  34 A also allow refrigerant to pass between the tube  28  and the tube sheet  32 . 
       FIG.  6    illustrates a sectional view taken along line  6 - 6  of  FIG.  2   . As shown in  FIG.  6   , the tube sheets  32  only extend partially across a diameter of the internal cavity  30  to allow the flow of refrigerant through the heat exchanger  20 . In the illustrated example, there are three tube sheets  32  located in the internal cavity  30  and all three of the tube sheets  32  are all aligned along the same portion of the internal cavity  30  to allow movement of refrigerant as described above. In another example, the tube sheet  32  could be spaced from opposing sides of body portion  22  when the plurality of tubes  28  only extend through a middle portion of the internal cavity  30 . 
       FIG.  7    illustrates another example tube sheet  132  similar to the tube sheet  32  above except where described above or shown in the Figures. The tube sheet  132  includes openings  134  for accepting a corresponding one of the plurality of tubes  28  and reinforcement members  135  extending between the openings  134  in the tube sheet  132  forming a matrix. The reinforcement members  135  can be attached to an external surface of the tube sheet  132  to form a support structure or be located within the tube sheet  132  itself. The reinforcement members  135  can be metallic rods, such as steel or aluminum or the reinforcement members  135  can be fibrous. In the illustrated example, at least one of the reinforcement members  135  extends from a first perimeter location on the tube sheet  132  to a second perimeter location on the tube sheet  132  generally opposite the first perimeter location. 
       FIG.  8    illustrates yet another example tube sheet  232  similar to the tube sheet  32  above except where described above or shown in Figures. The tube sheet  32  is comprised of a plurality of body portions  235  each having a hexagonal shape and an opening  234  for accepting a corresponding one of the plurality of tubes  28 . As shown in  FIG.  8   , the hexagonal bodies fit together to form a tube sheet  232  that closely approximates the inner contour  22 A of the body portion  22 . The body portions  235  can fit together with a friction fit, an adhesive, or vibration welding technique. In the illustrated example, the body portions  235  are made of a single unitary piece of refrigerant expanding material. 
     The body portions  235  can easily be added or subtracted from the tube sheet  232  to customize the tube sheet  232  for a specific application. This reduces the amount of time needed to manufacture or machine additional tube sheets for low volume applications. Although the body portions  335  are shown as being hexagons in the illustrated example, other shapes are also contemplated such as triangles, pentagons, hexagons, squares, or rectangles. 
       FIG.  9    illustrates another example individual body portion  335  similar to the body portion  235  above except where described below or shown in the Figures. The body portion  335  can attach to an adjacent body portion  335  through the use of mounting legs  337  that are moveable within channels  339  in the body portion  335 . Because the mounting legs  337  are moveable and able to slide into the channels  339 , the mounting legs  337  can engage adjacent body portions  335  and lock the adjacent body portions  335  together to form a grid similar to the grid shown in  FIG.  8   . Although the body portions  335  are shown as being hexagons in the illustrated example, other shapes are also contemplated such as triangles, pentagons, hexagons, squares, or rectangles. 
     Although the different non-limiting embodiments are illustrated as having specific components, the embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments. 
     It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed and illustrated in these exemplary embodiments, other arrangements could also benefit from the teachings of this disclosure. 
     The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure. For these reasons, the following claim should be studied to determine the true scope and content of this disclosure.