Patent Publication Number: US-9841228-B2

Title: System and method for liquefying a fluid and storing the liquefied fluid

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a Continuation of U.S. patent application Ser. No. 13/498,403, filed Mar. 27, 2012, which claims the priority benefit under 35 U.S.C. §371 of international patent application no. PCT/IB2010/053888, filed Aug. 30, 2010, which claims the priority benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/246,558 filed on Sep. 29, 2009, the contents of which are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to the liquefaction of a fluid, and to storage of the liquefied fluid. In particular, the invention relates to systems that provide for liquefaction and storage in a unified and integrated manner. 
     2. Description of the Related Art 
     Systems configured to liquefy fluids such as oxygen, nitrogen, and/or other fluids by reducing the temperature and increasing the pressure of the fluid being liquefied are known. Similarly, systems configured to store liquefied fluids are known. However, these systems are generally configured as separate solutions to separate problems. Consequently, conventional apparatus that have been configured to separately liquefy and store fluids rely on a transfer of fluid from a liquefaction system to a storage system that is inefficient, and is prone to malfunction and failure. Further, implementation of separate systems for liquefaction and storage may inhibit the portability, affordability, and/or usability of such conventional solutions. 
     SUMMARY OF THE INVENTION 
     One aspect of this invention relates to a system configured to liquefy a fluid, and to store the liquefied fluid. In one embodiment, the system comprises a housing, a heat exchange assembly, and a fluid storage assembly. The housing is configured to substantially seal the interior of the housing from atmosphere. The heat exchange assembly is disposed within the housing. The heat exchange assembly comprises a fluid conduit that passes from inside the housing to outside the housing, and is configured to receive a flow of fluid in its gaseous state from a fluid flow generator located outside the housing. The heat exchange assembly is configured to liquefy the flow of fluid received into the heat exchange assembly via the fluid conduit. The fluid storage assembly is disposed within the housing. The fluid storage assembly is in fluid communication with the heat exchange assembly, and is configured to store fluid that has been liquefied by the heat exchange assembly. 
     Another aspect of the invention relates to a method of liquefying a fluid, and storing the liquefied fluid. In one embodiment, the method comprises substantially sealing a cavity from atmosphere; receiving a flow of fluid in a gaseous state into the cavity from outside the cavity through a fluid conduit, wherein the flow of fluid is received into the cavity in a gaseous state; liquefying the flow of fluid received into the cavity via the fluid conduit; directing the liquefied fluid into a reservoir disposed within the cavity; and storing the liquefied fluid within the reservoir. 
     Yet another aspect of the invention relates to a system configured to liquefy a fluid, and to store the liquefied fluid. In one embodiment, the system comprises means for substantially sealing a cavity from atmosphere; means for receiving a flow of fluid in a gaseous state into the cavity from outside the cavity, wherein the flow of fluid is received into the cavity by the means for receiving in a gaseous state; means for liquefying the flow of fluid received into the cavity, wherein the means for liquefying the flow of fluid is disposed within the cavity; and means storing the liquefied fluid within the cavity. 
     These and other objects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. In one embodiment of the invention, the structural components illustrated herein are drawn in proportion. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not a limitation of the invention. In addition, it should be appreciated that structural features shown or described in any one embodiment herein can be used in other embodiments as well. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. As used in the specification and in the claims, the singular form of “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 2  illustrates a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 3  illustrates a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 4  illustrates a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 5  illustrates a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 6  illustrates a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 7  illustrates a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 8  illustrates a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 9  illustrates a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 10  illustrates a seal implemented within a Dewar system to seal an interface assembly from a storage assembly, according to one or more embodiments of the invention; 
         FIG. 11  illustrates a heat exchange assembly and an interface assembly in a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, according to one or more embodiments of the invention; 
         FIG. 12  illustrates a an interface assembly in a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, according to one or more embodiments of the invention; 
         FIG. 13  illustrates a heat exchange assembly formed integrally or securely with a lid of a housing that houses a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 14  illustrates a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 15  illustrates a an interface assembly in a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, according to one or more embodiments of the invention; 
         FIG. 16  illustrates a cold head from a heat exchange assembly configured to liquefy a fluid, in accordance with one or more embodiments of the invention; 
         FIG. 17  illustrates a heat exchange assembly formed integrally or securely with a lid of a housing that houses a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 18  illustrates a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 19  illustrates a heat exchange assembly and an interface assembly in a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, according to one or more embodiments of the invention; 
         FIG. 20  illustrates a seal between an interface assembly and a heat exchange assembly in a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 21  illustrates a heat exchange assembly formed integrally or securely with a lid of a housing that houses a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 22  illustrates a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; 
         FIG. 23  illustrates a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, in accordance with one or more embodiments of the invention; and 
         FIG. 24  illustrates an interface assembly in a Dewar system configured to liquefy a flow of fluid, and to store the liquefied fluid, according to one or more embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       FIGS. 1 and 2  illustrate a Dewar system  10  configured to liquefy a flow of fluid, and to store the liquefied fluid. The Dewar system  10  is disposed within a single, portable housing  12 . Disposing the components of Dewar system  10  within the single housing  12  enables liquefied fluid to be transferred between a heat exchange assembly  14  configured to liquefy fluid and a storage assembly  16  configured to store liquefied fluid in an enhanced manner. For example, by virtue of enclosing heat exchange assembly  14  and storage assembly  16  within housing  12 , the fluid is transferred between heat exchange assembly  14  and storage assembly  16  without implementing a conduit or line that must be individually insulated against ambient atmosphere. As another example, the enclosure of heat exchange assembly  14  and storage assembly  16  within housing  12  may enhance the portability and/or usability of Dewar system  10 . In one embodiment, the flow of fluid liquefied and stored by Dewar system  10  is oxygen (e.g., purified oxygen), nitrogen, and/or some other fluid. 
     Housing  12  is configured to substantially seal the interior of housing  12  from atmosphere. As such, the interior of housing  12  forms a cavity  18  that is substantially sealed from ambient atmosphere. This provides some isolation from ambient atmosphere for components of Dewar system  10  that are disposed within cavity  18  of housing  12 . To enhance this isolation, housing  12  may be formed from an insulating material. By way of non-limiting example, housing  12  may be formed from stainless steel, and/or other materials. To further insulate heat exchange assembly  14  and storage assembly  16  from atmosphere, in one embodiment, housing  12  may be evacuated between housing  12  and the portions of cavity  18  within which heat exchange assembly  14  and/or storage assembly  16  are disposed. The created vacuum may provide an enhanced layer of insulation and/or protection for heat exchange assembly  14  and/or storage assembly  16 . In addition to providing insulation, housing  12  also provides structural protection for components disposed therein. As such, housing  12  is rigid to resist breakage caused by drops, collisions, and/or other forces experienced by Dewar system  10 . Additionally, insulation wrap (not shown) may be used to coat the interior of housing  12  and/or component contained therein as an added one or more layers radiation barrier. 
     In one embodiment, housing  12  is formed from a first piece  20  and a second piece  22 . First piece  20  forms cavity  18  of housing  12  such that cavity  18  has an opening formed by a rim  24 . Second piece  22  is a lid, that is selectably coupled to first piece  20  at rim  24  of cavity  18  to substantially seal cavity  18  from atmosphere. The selectable coupling between first piece  20  and second piece  22  may be accomplished via releasable fasteners  26  (e.g., bolts and nuts), as shown in  FIGS. 1 and 2 . In other embodiments, alternative mechanisms for selectably coupling first piece  20  with second piece  22  may be implemented. For example, first piece  20  may be selectably coupled with second piece  22  via releasable catches and/or latches, a threaded fit, a friction fit, a press fit, a snap fit, a detent mechanism, and/or other mechanisms for selectably coupling components. Although in the embodiment illustrated in  FIGS. 1 and 2  first piece  20  and second piece  22  can be completely decoupled from each other, this is not intended to be limiting. Instead, first piece  20  and second piece  22  may be coupled with each other in a non-removable manner at one or more locations. For example, first piece  20  and second piece  22  may be coupled at one or more locations via hinge such that first piece  20  can be second piece  22  partially decoupled and pivoted away from each other to expose cavity  18  of housing  12  to atmosphere. In one embodiment, first piece  20  and second piece  22  are coupled in a non-removable manner (e.g., welded). 
     Heat exchange assembly  14  is configured to receive a flow of fluid in a gaseous state, and to liquefy the received flow of fluid. Heat exchange assembly  14  receives the flow of fluid from a source of fluid (not shown) that is external to housing  12 . The source of fluid may include, for example, a fluid flow generator (e.g., a pressure swing adsorption generator), a storage canister, a wall gas connection, and/or other sources of fluid. 
     Heat exchange assembly  14  is configured to liquefy the flow of fluid by lowering the temperature of the fluid. This may include supercooling the fluid down to temperatures of about 100° K. or less at 1 atmosphere. As is discussed below, in one embodiment, heat exchange assembly  14  operates by circulation of compressor cooled refrigerant. However, this is not intended to be limiting, and other types of heat exchange system may be disposed (in whole or in part) within housing  12  to liquefy the flow of fluid. For example, some other type of super-cooled fluid could be circulated within heat exchange assembly  14  rather than compressor cooled refrigerant (e.g., liquid nitrogen). 
     Storage assembly  16  is configured to store fluid that has been liquefied by heat exchange assembly  14 . In one embodiment, storage assembly  16  includes a storage reservoir  28 . Storage reservoir  28  is in fluid communication with heat exchange assembly  14  such that fluid that has been liquefied by heat exchange assembly  14  is directed into storage reservoir  28 . The liquefied fluid is then held within storage reservoir  28  until it is needed. As the liquefied fluid is stored within storage reservoir  28 , the temperature within storage reservoir  28  may rise to the point where some of the fluid begins to boil off back into the gaseous state. At least some of this boiled off fluid may be vented from housing  12  to maintain the pressure within storage reservoir  28  at a manageable level. 
     In one embodiment, housing  12  is formed as a cylinder. This embodiment of housing  12  has a top  30  formed by second piece  22 , and a bottom  32  formed by first piece  20 . When housing  12  is seated on bottom  32  in the embodiment shown in  FIGS. 1 and 2 , heat exchange assembly  14  and storage assembly  16  are disposed within housing  12  in a vertical configuration with heat exchange assembly  14  positioned above storage assembly  16 . 
     In one embodiment, storage assembly  16  is formed integrally or securely with first piece  20 . As used herein, the formation of storage assembly  16  integrally or securely with first piece  20  refers to a construction of storage assembly  16  and first piece  20  such that these two components are not intended to be separated during regular usage and/or maintenance. While separation of storage assembly  16  and first piece  20  may be achieved, reference to the secure and/or integral attachment between these components reflects the relative strength and permanence of this attachment during typical usage. 
     In one embodiment, heat exchange assembly  14  is formed integrally or securely with second piece  22 . As used herein, the formation of heat exchange assembly  14  integrally or securely with second piece  22  refers to a construction of heat exchange assembly  14  and second piece  22  such that these two components are not intended to be separated during regular usage and/or maintenance. While separation of heat exchange assembly  14  and second piece  22  may be achieved, reference to the secure and/or integral attachment between these components reflects the relative strength and permanence of this attachment during typical usage. 
     By virtue of the integral and secure formations of storage assembly  16  with first piece  20  and of heat exchange assembly  14  with second piece  22  in the embodiment illustrated in  FIGS. 1 and 2 , decoupling first piece  20  and second piece  22 , and removing second piece  22  from first piece  20  results in heat exchange assembly  14  being withdrawn from cavity  18  of housing  12 . However, this decoupling leaves storage assembly  16  within cavity  18 . As such, an interface assembly  34  that places heat exchange assembly  14  in fluid communication with storage assembly  16  enables heat exchange assembly  14  to be selectably released from fluid communication storage assembly  16  when second piece  22  of housing  12  is decoupled from first piece  20  of housing  12 . 
       FIGS. 3 and 4  illustrate one or more embodiments of Dewar system  10  in which when housing  12  is seated on bottom  32 , heat exchange assembly  14  and storage assembly  16  are located side by side within housing  12  (rather than one on top of the other). In the one or more embodiments depicted in  FIGS. 3 and 4 , second piece  22  of housing  12  is disposed over heat exchange assembly  14  so that heat exchange assembly  14  can be formed integrally and securely with heat exchange assembly  14 . 
     In the view of Dewar system  10  shown in  FIG. 4 , a fluid outlet  36  provides selective fluid communication between storage assembly  16  and the exterior of housing  12 . Fluid outlet  36  enables fluid stored within storage assembly  16  to be released from storage reservoir  28  for pressure maintenance within storage reservoir  28  and/or for use. Fluid outlet  36  includes an outlet conduit  38  and an outlet valve  40 . Outlet conduit  38  conveys fluid from within storage reservoir  28  to the exterior of housing  12 . Outlet valve  40  is configured to selectably seal the outlet conduit  38  such that the fluid from storage reservoir  28  can be released from storage reservoir  28  in a controllable manner. In one embodiment, rather than outlet valve  40 , fluid outlet  36  may include an interface (e.g., a threaded component, a component with a detent mechanism, etc.) that enables interface assembly  34  to be securely interfaced with a valve assembly that controls the release of fluid from storage reservoir  28 . Fluid outlet  36  may be configured to release fluid from storage reservoir  28  in the gaseous state (e.g., for pressure maintenance) and/or in the liquid state (e.g., for use). 
       FIGS. 5 and 6  illustrate one or more embodiments of Dewar system  10 . In the embodiments illustrated in  FIGS. 5 and 6 , second piece  22  is not formed as a substantially flat lid that is selectably coupled to rim  24  of first piece  20 . Instead, second piece  22  itself forms a portion of cavity  18  of housing  12 . As can be seen in  FIGS. 5 and 6 , heat exchange assembly  14  is nested inside of the portion of cavity  18  formed by second piece  22 , while storage assembly  16  is nested inside of the portion of cavity  18  formed by first piece  20 . 
     In one embodiment, a gasket  42  is disposed between first piece  20  and second piece  22 . One or more openings  44  are formed in gasket  42 . Through the one or more openings  44 , the components of Dewar system  10  housed within housing  12  communicate with the exterior of housing  12 . For example, fluid from a fluid source may be communicated to heat exchange assembly  14  through an opening  44 , fluid stored within storage reservoir  28  may be communicated to the exterior of the housing through an opening  44 , and/or other components of Dewar system  10  within housing  12  may be communicated with the exterior of housing  12  through the one or more openings  44 . 
       FIGS. 7 and 8  illustrate one or more embodiments of Dewar system  10 . In the embodiments illustrated in  FIGS. 7 and 8 , storage assembly  16  is disposed within heat exchange assembly  14 . In the depiction of Dewar system  10  shown in  FIGS. 7 and 8 , storage assembly  16  is shown as being positioned entirely within heat exchange assembly  14 . This is not intended to be limiting. In one embodiment, heat exchange assembly  14  only partially surrounds storage assembly  16 . 
       FIGS. 9-13  illustrate one or more embodiments of Dewar system  10  in which heat exchange assembly  14  is positioned on top of storage assembly  16  in the manner shown in  FIGS. 1 and 2 . Turning specifically to  FIG. 9 , heat exchange assembly  14  is shown as being encased by a heat exchange housing  46  disposed within housing  12 . Housing  46  houses heat exchange assembly  14  within cavity  18 . Housing  46  provides another layer of insulation between heat exchange assembly  14  and ambient atmosphere, and creates a pocket of gas (or of vacuum) between housing  12  and housing  46  that further insulates heat exchange assembly  14 . 
     In one embodiment, heat exchange assembly  14  includes a refrigerant conduit  48 . Refrigerant conduit  48  passes through housing  12  (e.g., at second piece  22 ) to communicate heat exchange assembly  14  with the exterior of housing  12 . Refrigerant conduit  48  is configured to receive and circulate a flow of cooled refrigerant. The flow of cooled refrigerant may be received, for example, from a compressor (not shown) that cools the refrigerant, and is located outside of housing  12 . Upon passing through the length of refrigerant conduit  48 , the refrigerant may be conveyed out of housing  12  by refrigerant conduit  48  (e.g., back to the compressor for further cooling and re-circulation). In one embodiment, refrigerant conduit  48  may be arranged in a coil, or some other labyrinthine configuration designed to minimize the volume of heat exchange assembly  14  as a whole while increasing the length of refrigerant conduit  48  included therein. 
     As can be seen in  FIG. 9 , in one embodiment, heat exchange assembly  14  includes a fluid conduit  50  disposed in thermal communication with heat exchange assembly  14 . In one embodiment, fluid conduit  50  is disposed next to and/or in contact with refrigerant conduit  48  such that refrigerant conduit  48  forms a heat sink along the length of fluid conduit  50 . Fluid conduit  50  passes through housing  12  (e.g., at second piece  22 ) to communicate with the exterior of housing  12 . The fluid conduit is configured to receive a flow of fluid in a gaseous state from a fluid source. The received flow of fluid is directed through fluid conduit  50 . As the flow of fluid passes through fluid conduit  50 , heat is removed from the fluid by refrigerant conduit  48 . This reduces the temperature of the flow of fluid to the point that the fluid is transformed from the gaseous state to a liquid state. The removal of heat from the fluid within fluid conduit  50  may reduce the temperature of the flow of fluid to a super-cooled level. 
     In one embodiment, heat exchange assembly  14  includes a cold head  52 . After directing the flow of fluid along the length of  48 , fluid conduit  50  may provide the flow of fluid into cold head  52 . Cold head  52  is configured to further reduce the temperature of the flow of fluid such that any fluid not liquefied within fluid conduit  50  is liquefied in cold head  52 . In one embodiment illustrated in  FIG. 9 , cold head  52  includes a secondary refrigerant conduit  54  and a condensing chamber  56 . 
     Secondary refrigerant conduit  54  is configured to receive cooled refrigerant (e.g., from refrigerant conduit  48 , from an external source, etc.), and to circulate the refrigerant. Secondary refrigerant conduit  54  is in thermal communication with cold head  52 . In one embodiment, secondary refrigerant conduit  54  is disposed around the outside of cold head  52  to provide a heat sink for cold head  52 . 
     Condensing chamber  56  is formed by the body of cold head  52 . The condensing chamber includes a fluid inlet  58  and a fluid outlet  60 . Fluid inlet  58  communicates with fluid conduit  50  to receive cooled and at least partially liquefied fluid therefrom. Fluid outlet  60  communicates with storage reservoir  28  to provide liquefied fluid thereto for storage. In one embodiment, one or more coalescing structures  62  are formed within condensing chamber  56 . Coalescing structures  62  are configured to form super-cooled surfaces on which fluid that has not yet been liquefied can be condensed. Coalescing structures  62  are cooled by the heat sink provided to cold head  52  by secondary refrigerant conduit  54 . In one embodiment, condensing chamber  56  is formed from a thermally conductive material, such as copper, aluminum, or other materials, that enhance the removal of heat from coalescing structures  62  by secondary refrigerant conduit  54 . 
     During operation, fluid that is at least partially liquefied is introduced into cold head  52  through fluid inlet  58 , and migrates toward fluid outlet  60 . As the fluid passes through condensing chamber  56  from fluid inlet  58  to fluid outlet  60 , fluid that has not been liquefied becomes condensed on coalescing structures  62 . Thus, fluid provided to storage reservoir  28  for storage and/or usage from cold head  52  is substantially completely liquefied. 
       FIG. 9  further illustrates a transfill tube  64 , and a fluid vent  66 . Transfill tube  64  is configured to communicate liquefied fluid in storage reservoir  28  with the exterior of housing  12  (e.g., for usage). Fluid vent  66  is configured to enable fluid stored within storage reservoir  28  to be vented. For example, elevated pressures within storage reservoir  28  caused by liquefied fluid stored in storage reservoir  28  boiling off can be regulated by selectively venting fluid in the gaseous state (after boil-off) from storage reservoir  28  through fluid vent  66 . 
     As can be seen in  FIG. 9 , in one embodiment, interface assembly  34  includes a reservoir neck  68  and a reservoir lid  70 . Reservoir neck  68  is provided at an opening in storage reservoir  28  of storage assembly  16  that faces toward heat exchange assembly  14 . Reservoir neck  68  has a generally cylindrical shape. When Dewar system  10  is assembled and operational, reservoir neck  68  is removably seated in an opening  72  formed in housing  46  at an end of reservoir neck  68  opposite from storage reservoir  28 . In one embodiment illustrated in  FIG. 9 , cold head  52  is configured to be disposed inside of reservoir neck  68  when Dewar system  10  is assembled and operational. 
     Reservoir lid  70  is configured to fill the opening in storage reservoir  28  by reservoir neck  68 , thereby enclosing storage reservoir  28 . In one embodiment, reservoir lid  70  seals storage reservoir  28 . For example,  FIG. 10  provides a magnified view of a seal  74  that is carried by reservoir lid  70 . Seal  74  includes an o-ring  76  and a spring backer  78  that retains o-ring  76  in place on reservoir lid  70 . When Dewar system  10  is assembled and operational, o-ring  76  contacts a lip  80  formed at the opening of storage reservoir  28  to seal storage reservoir  28 . 
       FIGS. 11 and 12  provide magnified views of heat exchange assembly  14  and interface assembly  34  together, and interface assembly  34  alone, respectively. As can be seen in these magnified views, in one embodiment, coalescing structures  62  formed within cold head  52  include a plurality of screen meshes  82  separated by spacers  84 . Screen meshes  82  and/or spacers  84  may be formed from thermally conductive materials, such as copper, aluminum, or other materials, to enhance the removal of heat from coalescing structures  62  by secondary refrigerant conduit  54  through thermal conduction. 
       FIG. 13  provides a view of at heat exchange assembly  14  integrally or securely formed with second piece  22 . Specifically, in the view shown in  FIG. 13 , decoupling second piece  22  from first piece  20  to open housing  12  has resulted in heat exchange assembly  14  being removed from housing  12 . As can be seen in  FIG. 13 , in addition to heat exchange assembly  14 , in one embodiment second piece  22  carries at least a portion of interface assembly  34  (e.g., lip  80 ). 
       FIGS. 14-17  illustrate one or more embodiments of Dewar system  10  in which heat exchange assembly  14  is positioned on top of storage assembly  16  in the manner shown in  FIGS. 1 and 2 . In the one or more embodiments illustrated in  FIGS. 14-17 , heat exchange assembly  14  does not include a secondary refrigerant conduit or condensing chamber. Instead, fluid expelled from fluid conduit  50  is provided into a chamber formed by reservoir neck  68 . As can be seen, for example, in the magnified view of  FIG. 15 , cold head  52  is also disposed in this chamber. 
     Cold head  52  is formed having a cross-section that tends to enhance the amount of surface area on cold head  52 . As fluid enters the chamber formed by reservoir neck  68  from fluid conduit  50 , fluid that is still in the gaseous state comes into contact with cold head  52 . This causes the fluid to condense, and then to flow down into storage reservoir  28  for storage. 
     As can be seen in  FIG. 15 , the chamber within reservoir neck  68  is formed in part by a lid  86 . Although lid  86  cooperates with reservoir neck  68  to form the chamber, lid  86  does not seal the chamber from heat exchange assembly  14 . Instead, fluid within storage reservoir  28  in the gaseous state may escape from storage reservoir  28  into heat exchange assembly  14  through and/or around lid  86 . For example, the engagement between lid  86  and reservoir neck  68  may not be sealed, and/or lid  86  may form a vent opening  88  shown in  FIG. 16 . Returning to  FIG. 14 , fluid that escapes from storage reservoir  28  in the gaseous state into heat exchange assembly  14  may be released from housing  12  (e.g., to atmosphere) through a fluid outlet  90 . 
       FIG. 17  provides a view of heat exchange assembly  14  and a portion of interface assembly  34  (e.g., lid  86 ) detached from the rest of Dewar system  10  by virtue of its integral and/or secure formation with second piece  22 . As can be seen in  FIG. 17 , in one embodiment illustrated in  FIGS. 14-17 , decoupling second piece  22  from first piece  20  enables heat exchange assembly  14  (complete with cold head  52 ) and lid  86  to be removed from cavity  18  of housing  12 . 
       FIGS. 18-21  illustrate one or more embodiments of Dewar system  10  in which heat exchange assembly  14  is positioned on top of storage assembly  16  in the manner shown in  FIGS. 1 and 2 . In one embodiment illustrated in  FIGS. 18-21 , cold head  52  is not located within reservoir neck  68 , but instead is positioned within housing  46  with the rest of heat exchange assembly  14 . 
     As can be seen in particular in  FIGS. 19 and 20 , interface assembly  34  includes a lid  92  that seals reservoir neck  68  and storage reservoir  28  from housing  46 . As is shown in  FIG. 21 , when second piece  22  of housing  12  is decoupled from first piece  20  of housing  12 , lid  92  is removed from cavity  18  with heat exchange assembly  14 . 
       FIG. 22  illustrates one or more embodiments of Dewar system  10  in which heat exchange assembly  14  is positioned on top of storage assembly  16  in the manner shown in  FIGS. 1 and 2 . However, in one embodiment illustrated in  FIG. 22 , reservoir neck  68  extends all the way through housing  12  from storage reservoir  28  to the opening in cavity  18 , and is configured to engage second piece  22  of housing  12  when Dewar system  10  is fully assembled. As such, if the interior of housing  12  is pumped down to form a vacuum therein, the vacuum space surrounds storage reservoir  28  and reservoir neck  68 . 
     In one embodiment illustrated in  FIG. 22 , heat exchange assembly  14  is not housed by housing  46 , but instead is configured to surround at least a portion of reservoir neck  68  in the vacuum space inside of housing  12 . For example, refrigerant conduit  48 , and fluid conduit  50  may be coiled about reservoir neck  68  in the vacuum space formed within housing  12 . In some implementations, fluid conduit  50  may be wrapped around refrigerant conduit  48 . This may enhance the amount of heat that is removed from fluid within fluid conduit  50  by refrigerant flowing through refrigerant conduit  48 . 
     In one embodiment illustrated in  FIG. 22 , heat exchange assembly  14  is formed integrally and/or securely within second piece  22  of housing  12 . As such, if housing  12  is disassembled by removing second piece  22  from first piece  20 , heat exchange assembly  14  will be withdrawn from cavity  18 . However, this is not intended to be limiting, and in one embodiment, heat exchange assembly  14  is formed integrally or securely with first piece  20  of housing  12  such that if second piece  22  is removed from first piece  20 , heat exchange assembly  14  remains seated within cavity  18 . 
       FIGS. 23 and 24  illustrate one or more embodiments of Dewar system  10  in which heat exchange assembly  14  and storage assembly  16  are positioned side by side within housing  12  in the manner shown in  FIGS. 3 and 4 . In one embodiment, fluid is received into heat exchange assembly  14  by fluid conduit  50 , and heat is removed from the fluid within fluid conduit  50  in much the same manner as was described above with respect to  FIGS. 9-13 . The fluid is then dispensed into cold head  52 , which itself is disposed in housing  46  with the rest of heat exchange assembly  14 . 
     In one embodiment illustrated in  FIGS. 23 and 24 , upon being liquefied by heat exchange assembly  14 , fluid is provided to storage reservoir  28  from cold head  52  by interface assembly  34 . In this embodiment, interface assembly  34  includes a siphon conduit  94  that communicates cold head  52  with storage reservoir  28 . The siphon conduit  94  may be formed with a releasable two-piece construction such that heat exchange assembly  14  can be selectively decoupled from storage assembly  16  for removal from housing  12 . Or, siphon conduit  94  may be formed as a single, or at least substantially non-releasable, conduit that runs from an outlet of cold head  52  to an inlet of storage reservoir  28 . 
     As can be seen in particular in the magnified view of  FIG. 24 , between housing  46  and storage reservoir  28 , the thickness of the material forming siphon conduit  94  may be greater than the thickness of the material within heat exchange assembly  14 . This may insulate the flow path formed by siphon conduit  94 , and/or may enable siphon conduit  94  to maintain its structural integrity in an embodiment in which the interior of housing  12  is under vacuum. 
     Although the invention has been described in detail for the purpose of illustration based on what is currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims. For example, it is to be understood that the present invention contemplates that, to the extent possible, one or more features of any embodiment can be combined with one or more features of any other embodiment.