Patent Publication Number: US-2023160640-A1

Title: Heat shrink assembly heat exchangers

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates to heat exchangers, and more particularly to heat exchangers for aerospace applications and the like. 
     2. Description of Related Art 
     Heat exchangers are costly to assembly because the fluids cannot cross-leak. Any manufacturing defect can present problems with cross-leaking, so assemblies must be carefully checked over before use. The conventional techniques have been considered satisfactory for their intended purpose. However, there is an ever present need for improved systems and methods for assembling heat exchangers. This disclosure provides a solution for this need. 
     SUMMARY 
     A heat exchanger assembly includes a first member defining fluid passages therein for a first heat exchanger fluid. A second member defines fluid passages therein for a second heat exchanger fluid. The second member is engaged to the first member with an interference fit. 
     The fluid passages of first member can be sealed against the second member by the interference fit. The fluid passages of the second member can be sealed against the first member by the interference fit. 
     The first and second members can be cylindrical, wherein the second member is engaged inside the first member. The fluid passages of the first and second members can be helical. The first member can define a first circumferential groove in an inner surface thereof at a first axial end thereof. The first member can defines a second circumferential groove in an inner surface thereof at a second axial end thereof opposite the first axial end. The first circumferential groove can be in fluid communication with the second circumferential groove through the fluid passages of the first member. 
     An inlet header and an outlet header can be included, wherein the inlet header is in fluid communication with the first circumferential groove to supply fluid to the fluid passages of the first member, and wherein the outlet header is in fluid communication with the second circumferential groove to provide an outlet for fluid from the fluid passages of the first member. Each fluid passage of the second member can include a respective inlet at a first axial end of the second member, and a respective outlet at a second axial end of the second member opposite the first axial end of the second member. 
     The first and second members can be a first heat exchanger pair. Additional heat exchanger pairs can be nested within the first heat exchanger pair. An outer cylindrical shell can be engaged to the first member with an interference fit. An inner cylindrical shell can be engaged inside an innermost member of the additional heat exchanger pairs with an interference fit. The additional heat exchanger pairs can be nested within the first heat exchanger pair form a circular duct housed within an outer shell. 
     At an end of the first and second members, the first and second members can be sealed by a weld joint, a braze joint, and/or an O-ring. The fluid passages of at least one of the first and second members can be sealed by the interference fit, and at least partially by a braze joint. 
     A method of assembling a heat exchanger includes thermally resizing at least one of a first heat exchanger member and a second heat exchanger member and assembling the second heat exchanger member to the first heat exchanger member. The method includes thermally equalizing the first and second heat exchanger members to engage the second heat exchanger member to the first heat exchanger member with an interference fit. 
     Thermally resizing can include heating the first heat exchanger member. Thermally resizing can include cooling the second heat exchanger member. The first heat exchanger member can be cylindrical, the second heat exchanger member can be cylindrical, and assembling the second heat exchanger member to the first heat exchanger member can include placing the second heat exchanger member within the first heat exchanger member. 
     These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
         FIG.  1    is an exploded cross-sectional side elevation view of an embodiment of a heat exchanger assembly constructed in accordance with the present disclosure, showing the first and second members prior to assembly; 
         FIG.  2    is a series of cross-sectional side elevation views, showing the same members as  FIG.  1    at left, in the middle showing the second member being inserted into the first member, and at right showing the second member engaged with an interference fit to the first member; 
         FIG.  3    is a cross-sectional perspective view of the assembly of  FIG.  1   , showing the first and second members with additional pairs of members nested within them; 
         FIG.  4    is a cross-sectional side elevation view of another configuration of the nested pairs of heat exchanger members of  FIG.  3   , showing the fluid passages on the radially outboard surfaces of the first and second members; and 
         FIG.  5    is a cross-sectional perspective view of another configuration of the assembly of  FIG.  3   , showing nested heat exchanger pairs without an inner shell. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an embodiment of a heat exchanger assembly in accordance with the disclosure is shown in  FIG.  1    and is designated generally by reference character  100 . Other embodiments of systems in accordance with the disclosure, or aspects thereof, are provided in  FIGS.  2 - 5   , as will be described. The systems and methods described herein can be used to facilitate assembly and quality control of heat exchanger assemblies using thermal resizing and interference fits. 
     The heat exchanger assembly  100  includes a first member  102  defining fluid passages  104  therein for a first heat exchanger fluid, e.g. a colder fluid in heat exchange. A second member  106  defines fluid passages  108  therein for a second heat exchanger fluid, e.g. a hotter fluid in heat exchange. The first and second members  102 ,  106  are cylindrical, and as will be discussed further below, the second member  106  engages inside the first member  102 . The fluid passages  104 ,  108  are helical, and are defined on radially inward facing surfaces of the members  102 ,  106 . 
     The first member  102  defines a first circumferential groove  110  in an inner surface thereof at a first axial end thereof relative to axis A. The first member  102  also defines a second circumferential groove  112  in the inner surface thereof at a second axial end thereof opposite the first axial end. The first circumferential groove  110  is in fluid communication with the second circumferential groove  112  through the fluid passages  104  of the first member  102 . Each fluid passage of the second member  106  includes a respective inlet  114  at a first axial end of the second member  106 , and a respective outlet  116  at a second axial end of the second member  106  opposite the first axial end of the second member, relative to axis A. 
     With reference now to  FIG.  2   , a method of assembling a heat exchanger includes thermally resizing at least one of the first heat exchanger member  102  and the second heat exchanger member  106  at stage  1  of  FIG.  2   . Thermally resizing includes heating the first heat exchanger member  102  to thermally expand it, and/or cooling the second heat exchanger member  106  to thermally contract it, e.g. using a cryogenic liquid bath or the like. With the members  102 ,  106  thermally resized, they can be assembled to together as indicated by stage 2 in  FIG.  2   , until the second member  106  is fully in place as show by stage 3 in  FIG.  2   . At this point, the members  102 ,  106  can be thermally equalized to engage the second heat exchanger member  106  to the first heat exchanger member  102  with an interference fit. 
     Although shapes other than cylindrical are contemplated, in the case of cylinders, the outer diameter of the second member  106  at a given temperature should be slightly larger than the inner diameter of the first member  102  at the given temperature to ensure the interference fit results after thermal equalization, with the second member  106  within the first member  102 . The result is an interference fit that seals the fluid passages  104  (labeled in  FIG.  1   ) of first member  102  against the inner surface of the second member  106 . If relatively cooler fluid in the first member  102  is exchanging heat with relatively warmer fluid in the second member  106 , the interference fit will be enhanced by operating the heat exchanger assembly  100 , as the thermal contraction/expansion caused by the fluids will tend to contract the first member  102  and expand the second member  106 . 
     With reference now to  FIG.  3   , the first and second members  102 ,  106  are a first heat exchanger pair  118 . Additional heat exchanger pairs  120  can be nested within the first heat exchanger pair  118 . The additional heat exchanger pairs  120  can be constructed and assembled in the same manner as the first heat exchange pair  118 . Each additional pair can be assembled into the assembly using thermal resizing, e.g. wherein each member is assembled in individually, or as pairs, or as sub-assemblies of pairs. An outer cylindrical shell  122  can be engaged to the first member  102  with an interference fit using thermal resizing. An inner cylindrical shell  124  can similarly be engaged inside an innermost member  102 ,  106  of the additional heat exchanger pairs  120  with an interference fit also using thermal resizing. 
     The additional heat exchanger pairs  120  can be nested within the first heat exchanger pair  118  form an annular heat exchanger duct housed between the inner and outer shells  124 ,  122 . The second heat exchange fluid can flow through the duct as indicated by the large arrows in  FIG.  3   , passing through the inlets  114 , passages  108 , and outlets  116  of the respective first members  106 , each of which are labeled in  FIG.  1   . The first heat exchange fluid can flow from the channels  110 , through the passages  104 , into the channels  112  of each of the respective first members  102 , each of which is labeled in  FIG.  1   . Fluid can be supplied to the channels  112  by an inlet header  126 , which connects into each of the inlet channels  110  labeled in  FIG.  1   . Fluid can egress from the outlet channels  112  labeled in  FIG.  1    through an outlet header  128 . While schematically shown external to the assembled members  102 ,  106 , the headers  126 ,  128  could also be made internal, e.g. with bores and/or piping to connect the channels respective  110 ,  112 . 
     With reference now to  FIG.  4   , it is contemplated that instead of having the passages  104 ,  108  defined in inner surfaces of their respective members  102 ,  106  as shown in  FIG.  1   , the fluid passages  104 ,  108  can be formed on the radially outward surfaces. In this case, the fluid passages of the second member  106  sealed against the first member by the interference fit. 
     With reference to  FIG.  5   , instead of having an inner shell  124  with an annular duct as show in  FIG.  3   , the additional heat exchanger pairs  120  can be nested within the first heat exchanger pair  118  form a full circular duct housed within an outer shell  122 . Those skilled in the art will readily appreciate that the scope of this disclosure provides for any suitable shape of heat exchanger assembly wherein the interference fit can be maintained in the assembly. 
     With reference again to  FIG.  4   , the ends of the members  102 ,  106  can be welded, brazed e.g., having a braze ring in place first, and/or an O-ring can be put in a groove so that the first fluid doesn’t leak out the ends into the second fluid. One such O-ring groove  103  is shown and labeled in  FIG.  4   , with an O-ring  105 , understanding that a braze ring would also look similar before braze operation where it then fills the joints between member  102 ,  106 . Any or all of the interfaces between the two members  102 ,  106  can be sealed in a similar manner, and it is also contemplated that the ends of members  102 ,  106  can be welded together outside faces, e.g. at any or all weld joint positions  107  labeled in  FIG.  4   , to seal that end leak path. The interference fit is intended to form a tight seal between adjacent passages (for example  104 ). It is also contemplated if needed in a given application, a thin layer of braze (e.g., paste or plating) can be applied between the two members  102 ,  106 . Then the whole assembly  100  can undergo a braze cycle. Examples of braze joint locations  109  where braze can be applied between layers of members  102 ,  106  are labeled in  FIG.  4   . 
     Systems and methods as disclosed herein provide potential benefits including providing lower cost heat exchangers than using traditional techniques. Systems and methods as disclosed herein provide the potential for reduction/elimination of chance of cross-leaks in heat exchangers. Additionally, sub-component testing can be used to reduce risk cross-leaks in final assemblies. 
     The methods and systems of the present disclosure, as described above and shown in the drawings, provide for facilitation of assembly and quality control in heat exchanger assemblies using thermal resizing and interference fits. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.