Heat exchanger with a glass body

Abstract

A heat exchanger comprises a glass body having a first flat face and a second flat face on opposing ends, and defining a longitudinal axis therebetween. A plurality of holes in the glass body are elongated along the longitudinal axis by extending from said first flat face to said second flat face. The plurality of holes are configured to receive and direct a gas therethrough, to exchange heat between the gas and the glass body.

Claims

1. An apparatus comprising: a glass body having a first flat face and a second flat face on opposing ends and defining a longitudinal axis between the opposing ends, the glass body including: a single, exterior, cylindrically-shaped surface continuously extending from the first flat face to the second flat face; an interior surface surrounding a central aperture, the central aperture extending longitudinally from the first flat face to the second flat face; and a plurality of holes surrounding the central aperture, the plurality of holes disposed within the glass body and extending longitudinally from the first flat face to the second flat face, wherein the holes are configured to receive and direct a gas through the holes to exchange heat between the gas and the glass body.

2. The apparatus of claim 1, further comprising a plurality of glass bodies, of which the glass body is one, arranged face to face.

3. The apparatus of claim 2, wherein at least a portion of the respective plurality of holes for any two adjacent glass bodies of the plurality of glass bodies are aligned.

4. The apparatus of claim 2, wherein each of the plurality of glass bodies is spaced apart from one another.

5. The apparatus of claim 4, further comprising one or more spacers configured to separate the plurality of glass bodies from each other, while permitting the gas to flow.

6. The apparatus of claim 2, wherein the plurality of glass bodies are configured to thermally isolate the first flat face of a first glass body and the second flat face of a last glass body at a temperature differential greater than 200K.

7. The apparatus of claim 1, wherein each hole has an opening of 5 m-100 m across at least one of the first flat face and the second flat face.

8. The apparatus of claim 1, wherein a ratio of volume of the plurality of holes to a volume of the glass body including the volume of the plurality of holes yields a porosity for the glass body of less than 60% so as to enable a higher heat capacity for the glass body.

9. The apparatus of claim 8, wherein the porosity for the glass body is less than 45%.

10. The apparatus of claim 1, wherein: the glass body has an annular cross-section around the central aperture; and the exterior and interior surfaces are solid surfaces that do not permit flow of the gas therebetween in a direction perpendicular to the longitudinal axis of the glass body.

11. The apparatus of claim 1, wherein the plurality of holes in the glass body includes more than two holes.

12. The apparatus of claim 1, wherein: a length of each hole is greater than a diameter of that hole; and an opening of each hole is circularly shaped.

13. The apparatus of claim 1, wherein the interior surface is a single cylindrically-shaped surface that continuously extends from the first flat face to the second flat face.

14. A heat exchanger for separating a hot end and a cold end of a cryogenic cooler, the heat exchanger comprising: a glass body having a first flat face and a second flat face on opposing ends and defining a longitudinal axis between the opposing ends, the glass body including: a single, exterior, cylindrically-shaped surface continuously extending from the first flat face to the second flat face; an interior surface surrounding a central aperture, the central aperture extending longitudinally from the first flat face to the second flat face; and a plurality of holes surrounding the central aperture, the plurality of holes disposed within the glass body and extending longitudinally from the first flat face to the second flat face, wherein at least a portion of the central aperture that is adjacent the first flat face is configured to receive at least a portion of the cryogenic cooler, wherein the holes are configured to receive and direct a gas through the holes to exchange heat between the gas and the glass body, and wherein the heat exchanger is configured so that the gas flows between the hot end and the cold end through the plurality of holes in the heat exchanger.

15. The heat exchanger of claim 14, wherein: the glass body has an annular cross-section around the central aperture; and the exterior and interior surfaces are solid surfaces that do not permit flow of the gas therebetween in a direction perpendicular to the longitudinal axis of the glass body.

16. The heat exchanger of claim 14, wherein the central aperture includes an opening on the first flat face, the opening configured to receive at least the portion of the cryogenic cooler.

17. The heat exchanger of claim 14, wherein the plurality of holes in the glass body includes more than two holes.

18. The heat exchanger of claim 14, wherein: a length of each hole is greater than a diameter of that hole; and an opening of each hole is circularly shaped.

19. The heat exchanger of claim 14, wherein the interior surface is a single cylindrically-shaped surface that continuously extends from the first flat face to the second flat face.

20. A heat exchanger for separating a hot end and a cold end of a cryogenic cooler, the heat exchanger comprising: a glass body having a first flat face and a second flat face on opposing ends and defining a longitudinal axis between the opposing ends, the glass body including: a single, exterior, cylindrically-shaped surface continuously extending from the first flat face to the second flat face; an interior surface surrounding a central aperture, the central aperture extending longitudinally from the first flat face to the second flat face, the interior surface being a single cylindrically-shaped surface that continuously extends from the first flat face to the second flat face; and a plurality of holes surrounding the central aperture, the plurality of holes disposed within the glass body and extending longitudinally from the first flat face to the second flat face, the plurality of holes in the glass body including more than two holes, a length of each hole being greater than a diameter of that hole, an opening of each hole being circularly shaped, wherein the glass body has an annular cross-section around the central aperture, wherein the central aperture includes an opening on the first flat face that is configured to receive at least a portion of the cryogenic cooler, wherein the holes are configured to receive and direct a gas through the holes to exchange heat between the gas and the glass body, wherein the exterior and interior surfaces are solid surfaces that do not permit flow of the gas therebetween in a direction perpendicular to the longitudinal axis of the glass body, and wherein the heat exchanger is configured so that the gas flows between the hot end and the cold end through the plurality of holes in the heat exchanger.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Various features of embodiments of this disclosure are shown in the drawings, in which like reference numerals designate like elements.

(2) FIG. 1 shows a perspective view of an embodiment of a heat exchanger of the present disclosure, having an annular configuration.

(3) 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.

(4) 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.

(5) FIG. 4 shows a perspective view of an embodiment of a heat exchanger contained within a housing.

(6) FIG. 5 shows a top view of the embodiment of FIG. 4, illustrating how the heat exchanger is isolated along an outer edge.

(7) 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.

(8) FIG. 7 shows a cutaway view of an alternative embodiment to that of FIG. 4, wherein the heat exchangers are spaced within the housing.

(9) FIG. 8 shows an alternative cutaway view to that of FIG. 7, wherein the spaced heat exchangers are separated by spacers within the housing.

(10) FIG. 9 shows the heat exchanger configured to receive at least a portion of a cryogenic cooler.

DETAILED DESCRIPTION

(11) 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.

(12) 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.

(13) 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.

(14) 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.

(15) 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 m 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 m 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.

(16) 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 m 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.

(17) 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.

(18) 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 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 an 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.

(19) 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.

(20) 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.

(21) 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.

(22) 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 50n of a last glass body 20n 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.

(23) 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.

(24) 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 are 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.

(25) 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.

(26) 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.

(27) 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.

(28) 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.

(29) 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.

(30) 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.

(31) FIG. 9 shows the heat exchanger 10 configured to receive at least a portion of a cryogenic cooler.

(32) 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.