Patent Publication Number: US-2019186851-A1

Title: Heat exchanger with a glass body

Description:
RELATED APPLICATIONS AND CLAIM OF PRIORITY 
     This application is a continuation of U.S. patent application Ser. No. 16/019,200 filed on Jun. 26, 2018, which is a continuation of U.S. patent application Ser. No. 12/888,306 filed on Sep. 22, 2010 (now U.S. Pat. No. 10,041,747). 
    
    
     BACKGROUND 
     This disclosure relates generally to heat exchangers. More particularly, this disclosure relates to improved structures and geometries for glass heat exchangers, which are more efficient in gas heat exchange. 
     Heat exchangers are devices that facilitate the transfer of heat between mediums. Such devices are found in a large number of applications, ranging from air-conditioning units, to engines, and so on. In some heat exchangers, efficiency is determined by the effectiveness of the heat exchanger in thermally isolating opposing sides of the heat exchanger such that a gas or other working fluid flowing therebetween transfers heat to the heat exchanger between a hot end and a cold end of the heat exchanger. One particular application of a heat exchanger where such an efficient heat gradient is of particular importance is in a cryogenic cooler (“cryocooler”), which may utilize the cold end to effectively cool various components, such as electronics, superconducting magnets, optical systems, or so on. 
     The primary use of the heat exchanger in systems such as cryocoolers may be to pre-cool the working gas as it is transferred from the hot end to the cold end of the machine. Such heat exchangers may be characterized by how the gas flows through the exchanger and the surrounding system. For example, many closed cycle, linear cryocooler systems utilize the Stirling cycle, wherein a working gas cyclically flows in opposing directions through the heat exchanger. Such systems are typically referred to as regenerative heat exchangers, or regenerators. In other systems, a working gas steadily flows through the heat exchanger, utilizing processes such as the Joule-Thompson effect to create the cold end. The heat exchangers of these steady flow systems are typically referred to as recuperative heat exchangers, or recuperators. 
     The effectiveness of heat exchangers may be dependent upon various factors, such as heat transfer effectiveness, pressure drop, heat capacity, and parasitic conduction of heat. In regenerative systems, the gas is compressed at the hot end of the regenerator, and will be allowed to expand after it reaches the cold end. The structure of the heat exchanger itself may prevent the transfer of significant amounts of heat to the cold end as it flows. In regenerative systems, the oscillating rate of gas flow is typically of a high frequency. Therefore, the rate of heat transfer from the working gas to the regenerator should be rapid to ensure a desirable amount of pre-cooling of the gas through the heat exchanger. 
     Minimizing pressure drop across the heat exchanger is also desirable in increasing cooler efficiency, however this is typically at odds with maximizing the rate of heat transfer because obtaining maximum heat transfer effectiveness is generally through maximizing the mount of solid surface area over or around which the gas flows, which may create flow friction for the gas, and thus increase the pressure drop. In many heat exchangers, the cross-sectional flow area and parameters of porosity for the heat exchanger are varied to balance minimal pressure drop and maximum heat transfer. 
     The heat capacity of the heat exchanger must be such that the exchanger may absorb heat from the working gas without experiencing an intrinsic temperature increase which may reduce system efficiency. An interplay between the specific heat of the heat exchanger materials and the specific heat of the working gas exists, and may be particularly troublesome when cryogenic temperatures are sought to be achieved at the cold end of the exchanger. As one example, the specific heat of helium (a common working gas) is relatively high at cryogenic temperatures, while the specific heat of common heat exchanger materials is lower at cryogenic temperatures than at room temperature. This may call for an increased volume or mass for the heat exchanger. 
     The material selection for the heat exchanger is also important in preventing parasitic conduction of heat, for example along the axis of the heat exchanger. Where a large temperature gradient occurs along the length of the heat exchanger, it is very desirable that the exchanger have low thermal conductivity along its length, as high conductivity may result in heat being conducted from the hot end to the cold end. This conducted heat is a parasitic reduction of efficiency, because it must be carried as part of the refrigeration that is produced by the cycle. 
     One type of conventional heat exchanger typically contains a large number of woven-wire screens (i.e. on the order of 1000 screens in some embodiments) that are packed together into a volume. The working gas flows through the screens of the volume, so that the screens, which are typically formed from stainless steel, absorb the heat from the gas. The screen material may be similar to that of typical filter screens, with hundreds of wires per inch of material and wire diameters on the scale of a thousandth of an inch. The wires are generally drawn from stainless steel stock, a material that exhibits acceptable heat capacity and thermal conductivity. 
     There are limitations to stacked screen heat exchangers, however. For example, the heat capacity of the stainless material drops to unacceptably low levels at low cryogenic temperatures (i.e. below 30K). Additionally, construction limitations on the screens permit only a relatively small range of regenerator porosities, the ratio of regenerator open volume to overall regenerator volume (typically 60-75%). Similarly, the pore size between rows of wire is limited. Restrictions on achievable porosity and pore size limit the ability of a cryocooler designer to effectively optimize the relationship between pressure drop, heat transfer effectiveness and heat capacity. As an example, at very low temperatures, such as those encountered in the 2 nd  stage of a multi-stage cryocooler, the ideal screen regenerator might have a porosity significantly lower than 60% such that the solid volume (and hence heat capacity) is increased in order to combat the reduction in specific heat of the stainless steel at such low temperatures. However, porosities significantly below 60% are difficult to obtain using stainless steel screen technology. 
     Another type of conventional heat exchangers contains packed sphere beds. The working glass flows through the spaces between the spheres of the exchanger, transferring heat into the spheres as it moves through the heat exchanger. The sphere bed heat exchangers have an advantage of being able to utilize materials that may not easily be formed into woven screens, such as lead or rare-earth metals, that may exhibit high specific heats at low cryogenic temperatures. Sphere bed heat exchangers also have an additional benefit of permitting a lower porosity for the heat exchanger (i.e. below 40% for some embodiments), which can be achieved due to the inherent geometry of the sphere pack. The lower porosity allows more solid material, and thus greater heat capacity, while maintaining an acceptable tolerance of pressure drop for many applications. In some cryocoolers utilizing packed spheres, temperatures as low as 11K at the cold end have been achieved. Despite this success, sphere beds are less effective at higher temperatures, where heat capacity is less of a concern than pressure drop. 
     A more recent development in heat exchanger technology has been the use of glass as the heat exchanging element. Glass manufacturing processes include etching, grinding, or machining, which may permit, among other things, greater degrees of shaping and control of the porosity of the heat exchanger. The present manufacturing of heat exchangers typically involves etching or scoring panes of glass, which are then bonded together to form heat exchange elements. Among other things, the bonding process, or the presence of the bond between the glass layers, may reduce the effectiveness of the glass in exchanging heat with the gas flowing through the etched layers. In other cases, heat exchangers may be formed by a plurality of perforated glass plates, having slots etched in each layer, separated by spacers. 
     What is needed is, among other things, improvements over known heat exchanger geometries and structures, which permit a more effective heat transfer without resulting in an excessive pressure drop. 
     SUMMARY 
     According to an embodiment, a heat exchanger may comprise a glass body having a first flat face and a second flat face on opposing ends. The first flat face and the second flat face may define a longitudinal axis therebetween. The heat exchanger may further have a plurality of holes in the glass body. The holes may be elongated along the longitudinal axis by extending from said first flat face to said second flat face. The plurality of holes may be configured to receive and direct a gas therethrough to exchange heat between the gas and the glass body. 
     Other aspects and embodiments will become apparent from the following detailed description, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features of embodiments of this disclosure are shown in the drawings, in which like reference numerals designate like elements. 
         FIG. 1  shows a perspective view of an embodiment of a heat exchanger of the present disclosure, having an annular configuration. 
         FIG. 2A  shows a top view of the embodiment of  FIG. 1 , illustrating in an enlargement in  FIG. 2B  that the heat exchanger contains a plurality of holes therein. 
         FIG. 3A  shows a cross sectional view of a portion of the embodiment of  FIG. 1 , showing in an enlargement in  FIG. 3B  that the holes of  FIGS. 2A-B  extend along the length of the heat exchanger. 
         FIG. 4  shows a perspective view of an embodiment of a heat exchanger contained within a housing. 
         FIG. 5  shows a top view of the embodiment of  FIG. 4 , illustrating how the heat exchanger is isolated along an outer edge. 
         FIG. 6  shows a cutaway view of an embodiment similar to that of  FIG. 4 , showing a plurality of heat exchangers stacked within the housing. 
         FIG. 7  shows a cutaway view of an alternative embodiment to that of  FIG. 4 , wherein the heat exchangers are spaced within the housing. 
         FIG. 8  shows an alternative cutaway view to that of  FIG. 7 , wherein the spaced heat exchangers are separated by spacers within the housing. 
         FIG. 9  shows the heat exchanger configured to receive at least a portion of a cryogenic cooler. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an embodiment of heat exchanger  10  of the present disclosure, configured to exchange heat with a gas flowing therethrough. Heat exchanger  10  may be configured to be utilized in any suitable application, including but not limited to a cryocooler or a heat-engine. In the illustrated embodiment, heat exchanger  10  contains glass body  20  having first flat face  40  and second flat face  50 . Glass body  20  may be of any appropriate construction or configuration, and formed from any appropriate configuration of glass. In an embodiment, the glass of glass body  20  may be selected for heat transfer properties, or ease of creation, for example. In various embodiments, glass body  20  may comprise glass made from borosilicate, lead oxide, or soda-lime glass. These glass compositions are not limiting, and in other embodiments glass body  20  may comprise other formulations of glass. 
     Glass body  20  may be of any appropriate shape. In the illustrated embodiment, glass body  20  has a generally annular cross sectional configuration around central aperture  30 . In other embodiments, glass body  20  may lack central aperture  30 , and may be of a circular or elliptical cross sectional configuration, such that glass body  20  approximates a cylinder. In further embodiments, glass body  20  may be of any other appropriate geometric shape, including having a triangular, rectangular, pentagon, hexagon, U shaped, or any other multi-sided cross section (forming a geometric prism or other polyhedron). In various embodiments central aperture  30  may be formed in or around these alternative shapes. Furthermore, central aperture  30  may be of any shape or configuration, including defining a space having any cross section, including those described above for glass body  20 . 
     Central aperture  30  may be configured for any suitable purpose. For example where heat exchanger  10  is configured to be used in a cryocooler, central aperture  30  may be configured to couple with a portion of the cryocooler. In an embodiment, the cryocooler may comprise a portion extending therefrom, such as a pulse tube, which may be received by central aperture  30  to connect heat exchanger  10  into the cryocooler. In other embodiments, central aperture  30  may be configured to receive other elements. For example, in embodiments in which heat exchanger  10  is being used in a heat engine, central aperture  30  may be configured to receive a moving piston for the heat engine. 
     First flat face  40  and second flat face  50  are spaced on opposing ends of glass body  20 . In the illustrated embodiment, first flat face  40  and second flat face  50  are configured in approximately parallel planes. As shown, first flat face  40  and second flat face  50  are depicted as equivalent to any given cross section of glass body  20 , because of this uniformity. In other embodiments, first flat face  40  and second flat face  50  may be intentionally angled with respect to one another, or with respect to other portions of glass body  20 .  FIG. 1  also shows longitudinal axis A defined by a line intersecting first flat face  40  and second flat face  50  approximately along a direction of elongation of glass body  20 . In an embodiment, the direction of elongation may be characterized by the direction of exterior sides  60  (and interior sides  65 , shown in  FIG. 2A , if aperture  30  is present) of glass body  20 , connecting first flat face  40  to second flat face  50 . 
       FIG. 2A  shows a top view of glass body  20 , in particular looking at first flat face  40  along longitudinal axis A. As seen in the area of enlargement highlighted in  FIG. 2B , glass body  20  is not solid, however contains a plurality of holes  70  formed in the glass. Holes  70  may be of any cross sectional shape, including but not limited to circular (or elliptical), rectangular, pentagon, hexagon, U-shape or any other geometric shape. Additionally, holes  70  may be of any appropriate size, including but not limited to having a size on the order of 5-100 μm across a side on first flat face  40  and/or second flat face  50 . The spacing between holes  70  may also be of any appropriate size, including but not limited to being on the order of 10-20 μm across between adjacent holes  70 . The size, number, and spacing of holes  70  in glass body  20  all affect the porosity of glass body  20 , which in turn affects rate of heat transfer between the gas and glass body  20 . 
       FIG. 3A  illustrates a cross section of glass body  20  along section line III (seen in  FIG. 2A ). As seen in the enlargement of  FIG. 3B , holes  70  extend through glass body  20  from first flat face  40  to second flat face  50 . Also as shown, the holes are all roughly parallel to each other, spaced from longitudinal axis A. The length of the holes  70  extending through glass body  20  also contribute to the porosity of glass body  20 . In an embodiment, the porosity of glass body  20  may comprise the ratio of the volume of holes  70 , as compared to the total volume of glass body  20  which includes the volume of holes  70 . The volume of glass body  20  excludes the volume of central aperture  30 , if present. In various embodiments, the porosity of glass body  20  may be less than 60%, including in some embodiments, a porosity of less than 45%. Such reduced porosity may result in glass body  20  having a higher heat capacity, due to the increased solid volume in glass body  20 . Such higher heat capacity may be useful in low temperature applications, because the specific heat of materials in heat exchanger  10 , such as glass bodies  20 , decreases at low temperatures, and can be made up for by increasing the solid volume (by lowering the porosity). In some embodiments, variation in the cross sectional size of holes  70  through glass body  20  may vary by less than 2% along the length of holes  70  extending through glass body  20 . In various embodiments, the length of side  60  and holes  70  therein may range from approximately 75 μm to 350 mm. The choice of porosity for glass body  20  affects, among other things, the pressure drop between first flat face  40  and second flat face  50 , and may be optimized based on factors such as the flow rate and pressure of a gas flowing through holes  70 . 
     The formation of glass bodies  20  with holes  70  may be by any suitable process. In an embodiment, holes  70  may be formed from drawn-glass flow tubes. In some embodiments, holes  70  may be etched from glass body  20  by exposure to a chemical rinse. In an embodiment, fibers of etchable core glass surrounded by non etchable cladding glass are stacked into hexagonal close-pack multifiber, which may be drawn to fuse the fibers together. In an embodiment, the hexagonal close-pack multifibers may then be stacked into a large array, and fused under pressure, which may reduce or eliminate interstitial voids. In an embodiment, the etchable core glass of each individual fiber may support the channels. In an embodiment, the fused body may be cut and ground into a blank for glass body  20 , from which glass bodies  20  may be cut. In an embodiment glass body  20  may be subsequently placed in an etching solution to remove the soluble components, leaving voids that are holes  70 . 
     As noted above, the plurality of holes  70  may be configured to receive and direct a gas therethrough, so as to exchange heat between the gas and glass body  20 . In essence, glass body  20  of heat exchanger  10  may act as a gas-solid heat exchanger. In various embodiments, the size, shape, and number of holes  70  in glass body  20  may be selected to tune the porosity of glass body  20 , to affect the flow of gas through heat exchanger  10 . For example, holes  70  may be sized and shaped to optimize surface area against which the gas may contact to transfer heat to glass body  20 . As the gas flows along the plurality of holes  70  from first flat face  40  to second flat face  50 , or vice versa, hot gas may transfer that heat to glass body  20 , while cool gas may receive heat from glass body  20 . Additionally, having a straight channel from first flat face  40  to second flat face  50  may reduce collisions of gas molecules, resulting in a reduced pressure drop between first flat face  40  and second flat face  50 . In an embodiment, the size of holes  70  across first flat face  40  and/or second flat face  50  may be selected based on the amount of gas flowing through heat exchanger  10 . In an embodiment, a higher capacity system may have a greater mass of gas flowing therethrough, so a larger width of holes  70  may reduce the gas velocity. In an embodiment, the width of holes  70  may be optimized based on the operating point, type, and/or cooling capacity of the system containing heat exchanger  10 . 
     The material selection for glass body  20  may ensure thermal isolation between portions of glass body  20  closer to first flat face  40  and portions of glass body  20  closer to flat face  40 . In an embodiment, each glass body  20  may be configured to thermally isolate first flat face  40  and second flat face  50  at a temperature differential of approximately 10-50K. In other embodiments, wherein glass body  20  is longer, a greater temperature differential may be achieved. In an embodiment, each of plurality of holes  70  of glass body  20  may be substantially the same size across first flat face  40  and/or second flat face  50 , so as to increase consistency of gas flow through glass body  20 , thus reducing or preventing differential or preferential flow. As noted above, in an embodiment, heat exchanger  10  may be assembled into a system, such as a cryocooler or a heat engine. In such embodiments, flat face  40  and second flat face  50  of heat exchanger  10  may be aligned along the flow path of a gas that flows through heat exchanger  10  that is used in the system. 
     In some embodiments of heat exchanger  10 , such as those shown in the perspective and top views of  FIGS. 4 and 5 , glass body  20  may be at least partially contained within exterior housing  80 . Exterior housing  80  may be of any construction or configuration, including but not limited to metal, plastic, non-porous glass, rubber, or any other material. In an embodiment, exterior housing  80  may comprise a sleeve for glass body  20 . In an embodiment, exterior housing  80  may be of sufficient thickness to withstand the pressure of gas flowing through glass body  20 . In an embodiment, exterior housing  80  may comprise or contribute to the formation of a pressure vessel around glass body  20 . In an embodiment, exterior housing  80  may be configured to surround exterior sides  60  of glass body  20 , so as to limit exposure to glass body  20  to first flat face  40  and second flat face  50 . 
     In an embodiment, glass body  20  may have portions of holes  70  surrounding exterior sides  60 . Such portions of holes  70  may result from cutting and/or shaping glass body  70  from glass that already has holes  70  formed therein. In an embodiment, exterior housing  80  may permit gas to flow between the exterior sides  60  of glass body  20  and interior sides  90  of exterior housing  80 , in particular through partially formed holes  70 . As noted above, however, having same sized holes  70  is preferred in glass body  20  to prevent differential flow, so partially formed holes  70  at the exterior sides  60  of glass body  20  may be undesired. In an embodiment, an area around first flat face  40  and/or second flat face  50  of glass body  20  may be covered by caps to prevent gas flow through partially formed holes  70 . In an embodiment, glass body  20  may be secured into exterior housing  80  so as to seal partially formed holes  70 . In an embodiment, glass body  20  may be secured by glue or epoxy into exterior housing  80 , which may fill in partially formed holes  70 . 
     In an alternative embodiment shown in  FIG. 6 , a cutaway view of heat exchanger  10 ′ is depicted with exterior housing  80  shown in outline form. As illustrated, a plurality of glass bodies  20 ,  20 ′, and  20 ″ (collectively  20 ) are assembled within exterior housing  80 . Also as shown, glass bodies  20  are assembled such that first flat face  40  or second flat face  50  for adjacent glass bodies  20  are arranged face to face within exterior housing  80 . In an embodiment having n glass bodies  20 , the plurality of glass bodies  20  in heat exchanger  10 ′ may be configured such that the first flat face  40  of a first glass body  20  in heat exchanger  10 ′ and the second flat face  50   n  of a last glass body  20   n  in heat exchanger  10  are thermally isolated with a temperature differential of approximately 80-270K. In other embodiments, such as where each glass body  20  is longer, or more glass bodies  20  are stacked together, the temperature delta may be greater. In other embodiments, such as where each glass body  20  is shorter, or fewer glass bodies  20  are stacked together, the temperature delta may be less. 
     In an embodiment, exterior housing  80  may be configured such that gas flowing through each of glass bodies  20  does not leak out between adjacent glass bodies  20 . In some embodiments, stacks of glass bodies  20  may be utilized to overcome limits in formation of holes  70  in each glass body  20 . For example, in some embodiments in which holes  70  are etched into each glass body  20  by a chemical bath, the etchant may be unable to traverse glass body  20  if glass body  20  is greater than a certain length. In some cases, holes  70  may then not be consistently etched from first flat face  40  to second flat face  50 , leaving holes  70  that are partially or completely blocked off within glass body  20 . 
     In some embodiments, holes  70  in adjacent glass bodies  20  may be aligned such that gas flowing through hole  70  in a first one of glass bodies  20  may substantially or completely enter an associated hole  70 ′ in a second one of glass bodies  20 ′. Such alignment may be accomplished by any suitable mechanism, including but not limited to laser-based alignment. Due to variability in manufacturing of glass bodies  20 , however, such alignment may be difficult, or unnecessary. In some embodiments, holes  70  in one glass body  20  may generally at least partially overlap two or more associated holes  70 ′ of an adjacent glass body  20 ′, such that, for example, gas traverses through the first hole  70 , before splitting into two or more holes  70 ′ of the adjacent glass body  20 ′. In an embodiment, holes  70  may be configured such that random orientation of glass bodies  20  may permit sufficient movement of gas between adjacent glass bodies  20  with minimal pressure drop. For example, in an embodiment, the arrangement of holes  70  in a glass body  20  may be such that the size of the holes  70  are larger than the connecting portions of glass body  20 , permitting ease of gas flow transitions between glass bodies  20 . As the number of transitions in the heat exchanger  10 ′ is smaller than those between the stacked metal screens of conventional heat exchangers, friction from gas flow may still be reduced as compared to conventional exchangers by this improved configuration. 
     In  FIG. 7 , another embodiment is shown as heat exchanger  10 ″, wherein each of the plurality of glass bodies  20  are spaced from one another in the external housing  80 . In an embodiment, such a spacing may be desirable to permit the gas flowing through glass bodies  20  to redistribute after passing through each glass body  20 . In an embodiment, the size of plurality of holes  70  may vary across different glass bodies  20 . For example, the plurality of holes  70  in one glass body  20  may be smaller across associated flat faces  40  and  50  of that glass body  20  as compared to the plurality of holes  70 ′ in another glass body  20 ′ across associated flat faces  40 ′ and  50 ′ of the other glass body  20 ′. In an embodiment, the porosity of glass body  20  associated with a hot end of heat exchanger  10  may be larger than the porosity of glass body  20  associated with a cold end of heat exchanger  10 . In an embodiment, each glass body  20  may be held in spaced relation in external housing  80  by being epoxied or otherwise held by the exterior sides  60  of each glass body  20 . 
       FIG. 8  illustrates another embodiment as heat exchanger  10 ″′, wherein spacers  100  are positioned between glass bodies  20  to separate glass bodies  20  within exterior housing  80 . In various embodiments, spacers  100  may be any suitable material, including but not limited to metal, glass, plastic, rubber or so on. In an embodiment, spacers  100  may be configured to receive and transmit the gas flowing through glass bodies  20 . In an embodiment, spacers  100  may comprise sufficient openings for gas from a previous glass body  20  to redistribute before entering a subsequent glass body  20 ′. In an embodiment, spacers  100  may be positioned at the exterior sides of each glass body  20 . In an embodiment, spacers  100  may cap partially formed holes  70  located where exterior sides  60  meet interior sides  90  of exterior housing  80 . 
     As noted above, heat exchanger  10  may be utilized in any number of applications, including but not limited to a cryocooler or a heat-engine. The direction of flow for the gas through heat exchanger  10  may change depending on the specific application. For example, some cryocoolers may make use of a liner closed-cycle configuration, such as the Stirling cycle in which gas oscillates back and forth through heat exchanger  10 . As another example, some heat engines utilize the Stirling cycle, heating the gas on one side of heat exchanger  10  and cooling the gas on the other, such that movement from the expansion and contraction of gas therethrough generates electrical or mechanical energy which may be harnessed. 
     In embodiments wherein the working gas oscillates through heat exchanger  10 , heat exchanger  10  may be characterized as a regenerator. In an embodiment, this oscillation may be at a rate of approximately 20-100 Hz. In an embodiment, as gas flows from a hot end of the cryocooler through heat exchanger  10  to a cold end of the cryocooler, the gas may give up heat to glass bodies  20  in heat exchanger  10 . As the flow reverses to flow from the cold end to the hot end, the gas may absorb heat back from glass bodies  20 . Because of this cyclic pattern, the net energy gain in heat exchanger  10  over any cycle when in this configuration may be approximately zero. 
     In other embodiments, the working gas may be configured to flow in one direction through glass bodies  20  of heat exchanger  10 . In such steady flow embodiments, which may operate by any number of mechanisms, including but not limited to the Joule-Thompson effect. As an example, gas may flow through heat exchanger  10 , and be cooled as it flows through holes  70  of glass bodies  20 , which act as the valve for the throttling process. In other embodiments, the length of glass bodies  20  may merely be configured to act as a solid-gas heat exchanger, such that as the gas flows through holes  70 , heat transfers to glass bodies  20 , and radiates outward from glass bodies  20  to the ambient environment. In an embodiment heat exchanger  10  configured to operate in a steady-flow embodiment may be characterized as a recuperator. 
     Regardless of the presence of a reversal of the direction of gas flow, in various embodiments as the gas flows axially through the plurality of holes  70 , the gas may cool from first flat face  40  to second flat face  50 . In an embodiment, the number of glass bodies  20  in heat exchanger  10  may be selected based on the amount of cooling and thermal separation required between the hot end and the cold end of heat exchanger  10 . In an embodiment, a set of approximately 5 to 10 of glass bodies  20  may be assembled into heat exchanger  10 . In an embodiment, heat exchanger  10  may be configured to thermally isolate the hot end and the cold end to prevent the parasitic conduction of heat from the hot end to the cold end. In an embodiment, the temperature differential between the hot end and the cold end of heat exchanger  10  may be approximately 200K. For example, the temperature may be approximately 100K at the cold end of heat exchanger  10  and approximately 300K at the hot end of heat exchanger  10 , to achieve cryogenic cooling in an approximately room temperature environment. In some embodiments, such as where the system utilizing heat exchanger  10  operates in cryogenic temperatures, the cold end of heat exchanger  10  may be any cryogenic temperature (i.e. typically below 125K). In an embodiment, to achieve low cryogenic temperatures, glass bodies  20  may be configured to have a lower porosity (such as by tuning the size and number of holes  70 ) to achieve a lower pressure drop. 
       FIG. 9  shows the heat exchanger  10  configured to receive at least a portion of a cryogenic cooler. 
     While certain embodiments have been shown and described, it is evident that variations and modifications are possible that are within the spirit and scope of the inventive concepts as represented by the following claims. The disclosed embodiments have been provided solely to illustrate the principles of the inventive concepts and should not be considered limiting in any way.