Heat exchanger and method for manufacturing the same

Abstract

An embodiment of the present application relates to a heat exchanger. The heat exchanger may be an evaporator or a condenser. The heat exchanger may include a plurality of structures extending from a substrate, with adjacent structures spaced apart by at least a first distance. The heat exchanger may further include at least one cover plate disposed on an end of the plurality of structures such that the at least one cover plate is spaced apart from the end of the plurality of structures by a second distance, the second distance being less than the first distance. The at least one cover plate is brazed to the plurality of structures by a brazing material provided between the end of the plurality of structures and the at least one cover plate. The brazing material is provided in a discontinuous configuration such that gaps are provided between portions of the brazing material such that a brazing joint is formed from the brazing material flowing into the gap between the at least one cover plate and the end of the plurality of structures.

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE Some embodiments relate to heat exchangers and methods of manufacturing heat exchangers used for two-phase cooling systems. [Background technology]

[0002] Heat exchangers, such as evaporators and condensers, are configured to enable heat transfer within a cooling system, the overall efficiency of which depends on the efficiency of the heat transfer that occurs in the heat exchangers. Summary of the Invention

[0003] In accordance with various (but not necessarily all) embodiments of the present application, a heat exchanger is provided, the heat exchanger including a plurality of structures extending from a substrate, adjacent structures spaced apart by at least a first distance, and at least one cover plate disposed at an end of the plurality of structures such that the end of the plurality of structures is spaced apart by a second distance less than the first distance, the at least one cover plate being brazed to the plurality of structures by a brazable material disposed between the ends of the plurality of structures and the at least one cover plate, the brazing material being disposed in a discontinuous configuration such that gaps are provided between portions of the brazing material, such that a brazed joint is formed from the brazing material flowing into the gaps between the at least one cover plate and the ends of the plurality of structures.

[0004] The braze material may be provided at a thickness less than the first distance.

[0005] The first distance and the second distance may be selected such that Laplace pressure causes the braze material to flow into gaps between ends of the structures and the at least one cover plate.

[0006] The structures may extend substantially perpendicularly from the substrate.

[0007] The plurality of structures may be disposed at equal intervals on the substrate.

[0008] The structures may be spaced closer together at an edge of the substrate than at a centre of the substrate.

[0009] The substrate may have a larger surface area than the heat source to which the heat exchanger is thermally coupled.

[0010] The heat exchanger may include a stiffener including a plurality of protrusions configured to extend between the plurality of structures to limit flexing of the plurality of structures.

[0011] At least some of the structures may extend through the at least one cover plate, and further coupling means may be arranged at ends of the structures that extend through the at least one cover plate.

[0012] The plurality of structures may include fins.

[0013] The heat exchanger may include an evaporator or a condenser.

[0014] In accordance with various (but not necessarily all) embodiments of the present application, a method for manufacturing a heat exchanger is provided, the method including: providing a plurality of structures extending from a substrate, the plurality of structures being spaced apart by at least a first distance; providing a braze material overlying at least a portion of the plurality of structures, the braze material being provided in a discontinuous configuration such that gaps are provided between portions of the braze material; providing at least one cover plate disposed on ends of the plurality of structures such that the cover plate is spaced apart from the ends of the plurality of structures by a second distance less than the first distance; and heating the braze material such that the braze material flows into the gap between the at least one cover plate and the ends of the plurality of structures.

[0015] The braze material may be provided at a thickness less than the first distance.

[0016] The first distance and the second distance may be selected such that Laplace pressure causes the braze material to flow into gaps between ends of the plurality of structures and the at least one cover plate.

[0017] In accordance with various (not necessarily all) embodiments of the present application, a heat exchanger can be provided that includes a substrate, a plurality of structures extending from the substrate, and at least one stiffener including a plurality of protrusions configured to extend between the plurality of structures to reduce bending of the plurality of structures.

[0018] The heat exchanger may include a cover plate having the at least one stiffener disposed as part of the cover plate.

[0019] The substrate may be connected to first ends of the plurality of structures and the at least one stiffener may be connected to second ends of the plurality of structures.

[0020] Sides of the plurality of protrusions of the stiffener may be brazed to sides of the plurality of structures.

[0021] The protrusions of the stiffener may be bonded to all of the plurality of structures.

[0022] The protrusions of the stiffener may be coupled to portions of the plurality of structures.

[0023] In accordance with various (but not necessarily all) embodiments of the present application, a heat exchanger can be provided that includes a substrate and a number of structures extending from the substrate and is configured to provide a larger flow path for a working fluid to flow toward a center of the substrate than toward an edge of the substrate.

[0024] The structures may be spaced closer together at an edge of the substrate than at a centre of the substrate.

[0025] The heat exchanger may include an inlet portion having a greater flow path width at a center of the substrate than at an edge of the substrate.

[0026] The substrate may have a larger surface area than the heat source to which the heat exchanger is thermally coupled.

[0027] In accordance with various (not necessarily all) embodiments of the present application, a heat exchanger may be provided that includes a substrate, a plurality of structures extending from the substrate, and a cover plate, at least some of the plurality of structures extending through the cover plate, and the coupling means is provided at an end of the structures extending through the cover plate.

[0028] According to various (but not necessarily all) embodiments of the present application, a two-phase cooling system may be provided that includes one or more heat exchangers as described herein. [Brief description of the drawings]

[0029] Some embodiments will now be described with reference to the accompanying drawings. [Figure 1] FIG. 1 is a schematic diagram illustrating a passive two-phase cooling system according to an embodiment. [Figure 2A] FIG. 2 is a schematic diagram showing a part of an evaporator according to an embodiment. [Figure 2B] FIG. 2 is a schematic diagram showing a part of an evaporator according to an embodiment. [Figure 3A] FIG. 2 is a schematic diagram showing a manufactured evaporator according to an embodiment. [Figure 3B] FIG. 2 is a schematic diagram showing a manufactured evaporator according to an embodiment. [Figure 4] FIG. 2 is a schematic diagram showing a method according to an embodiment. [Figure 5A] FIG. 2 is a schematic diagram showing an alternative configuration of the structure of the brazing material according to the embodiment. [Figure 5B] FIG. 2 is a schematic diagram showing an alternative configuration of the structure of the brazing material according to the embodiment. [Figure 5C]FIG. 2 is a schematic diagram showing an alternative configuration of the structure of the brazing material according to the embodiment. [Figure 5D] FIG. 2 is a schematic diagram showing an alternative configuration of the structure of the brazing material according to the embodiment. [Figure 6] FIG. 2 is a schematic diagram showing a manufactured evaporator according to an embodiment. [Figure 7A] FIG. 2 is a schematic diagram showing an evaporator according to an embodiment. [Figure 7B] FIG. 2 is a schematic diagram showing an evaporator according to an embodiment. [Figure 8] FIG. 2 is a schematic diagram showing an evaporator according to an embodiment. [Figure 9] FIG. 1 is a schematic diagram of a passive two-phase cooling system according to an embodiment and a schematic diagram showing the main components. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] FIG. 1 is a schematic diagram illustrating a two-phase cooling system 101 including heat exchangers such as an evaporator 103 and a condenser 105 according to an embodiment of the present application.

[0031] In the embodiment of Figure 1, the two-phase cooling system 101 comprises a passive two-phase cooling system that is driven by gravity rather than a pump and requires an external work input to drive the flow. In the embodiment of Figure 1, the passive two-phase cooling system 101 comprises a thermosiphon loop. The heat exchanger may be located in other types of two-phase cooling systems, such as a heat pipe or a vapor chest.

[0032] 1 includes an evaporator 103, a condenser 105, a downcomer 107, and an upcomer 109. A working fluid 113 is provided within the thermosiphon loop. When the thermosiphon loop is in use, the working fluid 113 circulates through the components of the thermosiphon loop.

[0033] The evaporator 103 is located at the bottom of the thermosiphon loop such that the working fluid flows through the downcomer 107 into the evaporator 103 by the force of gravity as shown by arrow 115. The height and inner diameter of the downcomer 107 can be selected such that the static end of the fluid in the downcomer 107 causes the fluid to flow through the evaporator 103, the riser 109, and the condenser 105. The working fluid 113 is typically in a liquid phase 117 when in the downcomer 107. In particular, the volume of the downcomer 107 filled with the working fluid 113 in liquid phase 117 depends on the operating conditions and geometry of the thermosiphon.

[0034] The evaporator 103 includes any means for transferring heat from a heat source 111 to the working fluid 113. The evaporator 103 is thermally coupled to the heat source 111. A thermal interface material may be used to enable the evaporator 103 to be thermally coupled to the heat source 111. The heat source 111 may include electronic equipment that generates unwanted heat during operation. The electronic equipment may be servers, routers, network switches, storage equipment, or any other suitable type of equipment. In some examples, these heat sources may include a data center, a communications equipment room, or a plurality of electronic equipment that may provide a network, a communications room, a computer room, a network room, or any other suitable arrangement.

[0035] In other embodiments, the heat source 111 can be an intermediate fluid, and thus heat is exchanged between two working fluids (intermediate fluid and working fluid 113). In these embodiments, the evaporator 103 is a heat exchanger with a metal wall separating the two streams. The wall may be made of ceramic or other materials.

[0036] Heat is transferred from the heat source 111 to the working fluid 113 in the evaporator 103, as indicated by arrows 119. This heat transfer causes evaporation of a portion of the working fluid 113 in the evaporator 103, converting the working fluid 113 from a liquid phase 117 to a mixture of liquid and vapor phases. In particular, the evaporator 103 converts a portion of the working fluid 113 into a vapor phase 121 while allowing a portion to remain in the liquid phase 117, resulting in a two-phase mixture exiting the evaporator 103 with a determined vapor dryness fraction. The two-phase mixture may include droplets of vapor entrained in a liquid or other flow state, depending on the thermosiphon loop design, heat load, heat removal conditions, charge rate, and other suitable parameters.

[0037] The evaporator 103 is coupled to the riser 109 such that the working fluid discharged from the evaporator 103 flows into the riser 109. As indicated by arrow 123, the working fluid comprises a two-phase mixture in which the vapor phase 121 is less dense than the liquid phase 117. Passive flow in the thermosiphon loop is driven by the density difference between the liquid phase of the working fluid 113 in the downcomer 107 and the two-phase mixture of the working fluid 113 in the riser 109.

[0038] The evaporator 103 may include structures that allow for efficient heat transfer from the evaporator 103 to the working fluid 113. For example, the evaporator 103 may include a wick structure, a microchannel, an array of fins, a serpentine arrangement of macro / microchannels, or any suitable combination of these features. Figures 2, 3, and 6-8 show examples of the evaporator 103 that include such structures.

[0039] The condenser 105 is provided at the top of the thermosiphon loop. The condenser 105 is positioned above the evaporator 103 such that the working fluid 113 flows (by gravity 115) downward from the condenser 105 to the evaporator 103 and upward from the evaporator 103 to the condenser 105.

[0040] The condenser 105 is coupled to a riser 109 such that the working fluid 113 in the two-phase mixture (vapor phase 121 and liquid phase 117) flows from the riser 109 into the condenser 105. The condenser 105 may include any means for cooling the working fluid 113. For example, the condenser 105 may be air-cooled or liquid-cooled. A liquid-cooled condenser 105 may include a tube-in-tube configuration, a shell-and-tube configuration, a plate heat exchanger, or any other suitable configuration or arrangement. An air-cooled condenser 105 may include a louvered fin flat tube heat exchanger, a tube-and-fin heat exchanger, or any other suitable type of heat exchanger configuration or arrangement.

[0041] The condenser 105 is thermally coupled to a coolant 125. A thermal interface material may be used to enable the condenser 105 to be thermally coupled to the coolant 125. In other embodiments, the coolant 125 may be directly integrated into the condenser 105 with a wall interface separating the flow of working fluid 113 from the flow of the coolant 125. The wall interface may include a highly conductive metal or metal alloy, such as copper, aluminum, brass, or any other suitable metal. In some embodiments, the wall interface may include a highly conductive ceramic, such as aluminum nitride (AlN), or a polymer, such as a filled polymer composite.

[0042] The condenser 105 allows for heat transfer from the working fluid 113 to the coolant 125, as indicated by arrow 127. This heat transfer causes the working fluid 113 to at least partially condense and return to the liquid phase 117. The working fluid 113 at the outlet of the condenser 105 may be in the liquid phase 117 or a two-phase mixture (vapor phase 121 and liquid phase 117).

[0043] The condenser 105 is coupled to the downcomer 107 such that the working fluid 113 flows by gravity down the downcomer 107 and back to the inlet of the evaporator 103 .

[0044] 2A and 2B show a portion of a heat exchanger 200 that can be used in the two-phase cooling system 101 of FIG. 1 or any other suitable type of cooling system. The heat exchanger 200 can be the evaporator 103 or the condenser 105, or any other suitable type of heat exchanger. The heat exchanger 200 can be a macro-scale or micro-scale two-phase heat exchanger. The heat exchanger 200 can be a single-phase or two-phase heat exchanger 200, or any other suitable type of heat exchanger 200.

[0045] The exemplary heat exchanger 200 includes a substrate 201, a plurality of structures 203, and at least one cover plate 205. To achieve a more robust design, the heat exchanger 200 includes a mechanical bond between the top of the structure 203 and the cover plate 205. The components of the heat exchanger 200 are not shown to scale in FIGS. 2A and 2B. FIG. 2A shows the heat exchanger 200 before the brazing material 207 melts, and FIG. 2B shows the heat exchanger 200 after the brazing material 207 melts. FIGS. 2A and 2B show only a portion of the heat exchanger 200, and therefore only two structures 203. It should be understood that the plurality of structures 203 are configured to provide multiple flow paths for a working fluid through the heat exchanger 200.

[0046] The substrate 201 includes a flat or substantially flat surface. The substrate 201 may include a thermally conductive material. When the heat exchanger 200 is used as the evaporator 103, the substrate 201 may be thermally coupled to a heat source to enable heat transfer from the heat source to a working fluid in the evaporator 103.

[0047] The plurality of structures 203 extend from a surface of the substrate 201. The structures 203 may be obtained by machining, brazing, extrusion, additive manufacturing, or any other suitable manufacturing technique or combination of manufacturing techniques. At least a portion of the structures 203 define a flow path for a working fluid through the heat exchanger 200. In other embodiments, the heat exchanger 200 may include a plurality of different types of the structures 203, such as fins, plates, or any other suitable structures.

[0048] In the embodiment of Figures 2A and 2B, the structures 203 include elongated structures that extend vertically or substantially vertically from the substrate 201. In the embodiment of Figures 2A and 2B, the structures 203 have a rectangular cross-section. Other shapes for the structures 203 are provided by other embodiments of the present application.

[0049] In the embodiment of FIGS. 2A and 2B, two adjacent structures 203 are separated by a first distance w. The first distance determines the channel width between the structures 203. In some embodiments, the heat exchanger 200 may be configured such that the structures 203 are spaced at equal intervals across the substrate 201. In such an embodiment, different channels between different adjacent structures 203 have the same width. In other embodiments, the heat exchanger 200 may be configured such that the structures 203 are spaced at equal intervals across the substrate 201. For example, the structures 203 may be spaced closer together in regions of the substrate 201 that are closer to a heat source. This allows for larger flow paths and more fluid flow in areas of the heat exchanger 200 that experience higher thermal loads. For example, the structures 203 may be spaced closer together at the edge of the substrate 201 than at the center of the substrate 201.

[0050] In some embodiments, the footprint of the substrate 201 may be larger than the area of ​​the heat source to improve heat spreading. In such embodiments, the evaporator 103 having non-uniform flow channel widths may be advantageous to provide uniform or substantially uniform flow distribution in all flow channels of the evaporator 103, thereby improving thermal performance.

[0051] The structure 203 may comprise any suitable thermally conductive material. The structure 203 may comprise the same material as the substrate 201 and the cover plate 205. In other embodiments, the substrate 201 and the structure 203 may comprise a different material than that used for the cover plate 205.

[0052] The cover plate 205 is disposed to cover the ends of the structures 203. The cover plate 205 is provided at the opposite end of the structures 203 with respect to the substrate 201 to form a closed volume for circulation of the working fluid 113.

[0053] The cover plate 205 includes a flat or substantially flat surface. In the embodiment of Figures 2A and 2B, only a portion of the cover plate 205 is shown. It should be understood that the cover plate 205 may cover all of the plurality of structures 203 or other structures.

[0054] The cover plate 205 is brazed to the structures 203 by the brazing material 207. The brazing material 207 is provided between the ends of the structures 203 and the cover plate 205. The brazing material 207 may include any suitable material that can be melted and hardened to form a rigid connection between the ends of the structures 203 and the cover plate 205. In some embodiments, the heat exchanger 200 can be further strengthened by brazing four outer surfaces of the cover plate 205 to the top of the substrate 201.

[0055] 2A shows the heat exchanger 200 before the brazing material 207 melts and before a rigid connection is formed. The cover plate 205 is spaced a second distance d from the ends of the structures 203. The second distance d is less than the first distance w that determines the gap between adjacent structures 203.

[0056] In this case, the brazing material also has a thickness d equal to the spacing between the ends of the structures 203 and the cover plate 205. The thickness of the brazing material is therefore also smaller than the spacing between adjacent structures 203.

[0057] The brazing material 207 may be provided in a discontinuous configuration. Instead of being provided in a continuous sheet, the brazing material 207 is discontinuous such that there are gaps provided between portions of the brazing material 207. For example, the brazing material 207 may be provided as a network of lines or intersecting lines, or in any other suitable configuration. In the embodiment shown in FIG. 2A, the discontinuities extend into the page.

[0058] 2B shows the heat exchanger 200 after the braze material 207 has melted and formed a rigid joint between the end of the structure 203 and the cover plate 205. As the braze material 207 melts, it flows between the end of the structure 203 and the cover plate 205, and the heat exchanger 200 cools again and a rigid joint is formed from the solidified braze material 207.

[0059] In some embodiments of the present application, the discontinuous configuration of the braze material 207 allows the molten braze material 207 to flow into the gaps between the cover plate 205 and the edges of the plurality of structures 203. The braze material 207 flows horizontally across the edges of the plurality of structures 203, rather than flowing downward into channels between adjacent structures 203. In the example shown in Figures 2A and 2B, the molten braze material 207 flows into the page to form a braze joint, as shown in Figure 2B.

[0060] In some embodiments of the present application, the braze material 207 flows horizontally across the ends of the structures 203, rather than flowing downwards into the channels between the adjacent structures 203. This means that the volume of the channels for the flow of the working fluid 113 is maintained and not reduced by unnecessary braze material 207 flowing into the channels. This is beneficial for the efficient functioning of the heat exchanger 200.

[0061] The spacing d between the end of the structure 203 and the cover plate 205 and the width w of the flow path between the adjacent flow paths may be selected to control the Laplace pressure. The Laplace pressure causes the brazing material 207 to flow horizontally into the gap between the end of the structures 203 and at least one of the cover plates 205, rather than flowing downward into the flow paths between the adjacent structures 203. The brazing material 207 may wick through the gap between the end of the structure 203 and the cover plate 205. The width w of the flow path is greater than the spacing d between the end of the structure 203 and the cover plate and the corresponding thickness of the unmelted brazing material 207. The Laplace pressure is inversely proportional to the thickness of the brazing material 207, so that when the brazing material 207 melts, a greater pressure difference is created horizontally than downward, causing the brazing material 207 to flow horizontally.

[0062] 3A-3B show an example of a manufactured heat exchanger 200. In this example, the heat exchanger 200 is the evaporator 103, and the plurality of structures 203 includes the plurality of evaporator fins 305. Other types of heat exchangers 200 including other types of structures 203 may be manufactured using similar processes in the variations of the present application.

[0063] Figure 3A shows the braze material 207 applied to the ends of the evaporator fins 305. Figure 3B shows a cross section of a portion of the evaporator 103 before the braze material 207 melts.

[0064] Figure 3A shows the substrate 201 and a number of evaporator fins 305 extending from the substrate 201. Figure 3A does not show the cover plate 205.

[0065] 3A, the substrate 201 is a square or substantially square plate. In some embodiments of the present application, substrates 201 of other shapes may be used.

[0066] The evaporator fins 305 extend vertically or substantially vertically from the substrate 201. In the embodiment of FIG. 3A, each of the evaporator fins 305 comprises a thin plate. The thickness of the plate is several orders of magnitude less than the longest length of the plate (along the flow direction). The plates of the evaporator fins 305 are arranged in a parallel or substantially parallel arrangement across the surface of the substrate 201. Other dimensions and shapes of the plates of the evaporator fins 305 that define flow paths may be used depending on the application and operating conditions.

[0067] Adjacent evaporator fins 305 are spaced apart from each other by a first distance w. In the embodiment of Figure 3A, the evaporator fins 305 are uniformly spaced across the surface of the substrate 201 such that each of the evaporator fins 305 is spaced apart from an adjacent evaporator fin 305 by the same first distance w. This forms a plurality of parallel, or substantially parallel, channels across the surface of the substrate 201, the channels having a width w.

[0068] The brazing material 207 is provided on the ends of the evaporator fins 305. In the embodiment of Fig. 3A, the brazing material 207 is provided in a number of traces 301. The traces 301 extend across the ends of the evaporator fins 305. In the embodiment of Fig. 3A, the traces 301 extend in a direction perpendicular or substantially perpendicular to the direction of the flow channels formed by the evaporator fins 305.

[0069] The traces 301 of the brazing material 207 are arranged in a discontinuous configuration such that there are gaps between the traces 301. The gaps on top of the evaporator fins 305 provide space for the brazing material 207 to flow when it melts, ensuring effective bonding between the evaporator fins 305 and the cover plate 205. In the embodiment shown in Figure 3A, the traces 301 of the brazing material 207 are arranged at equal intervals on the ends of the evaporator fins 305. In other embodiments of the present application, other arrangements of the traces 301 may be used.

[0070] The traces 301 of the brazing material 207 have a thickness d that is less than the width between adjacent evaporator fins 305 .

[0071] 3B shows a cross section of a portion of the evaporator 103 before the brazing material 207 melts. FIG 3B shows one end of the evaporator fin 305 and the wiring 301 of the brazing material 207 provided between the end of the evaporator fin 305 and the cover plate 205.

[0072] The cover plate 205 is disposed on the traces 301 of the brazing material 207. Due to the thickness of the traces 301 of the brazing material 207, the cover plate 205 is spaced a distance d from the edge of the evaporator fins 305. In the embodiment shown in Figure 3B, the traces 301 have a circular or substantially circular cross section. In other embodiments of the present application, traces of other shapes may be used.

[0073] As the braze material 207 melts, Laplace pressure causes the braze material to flow horizontally between the cover plate 205 and the ends of the evaporator fins 305, as shown by arrows 303 in Figure 3B. This flow direction helps to create a strong braze joint and prevents excess braze material from flowing into the flow passages formed by the evaporator fins 305.

[0074] 4 shows an example of a method that can be used to manufacture a heat exchanger 200 according to some embodiments of the present application. The heat exchanger 200 can be a macro-scale or micro-scale two-phase heat exchanger. The heat exchanger 200 can be used for a two-phase cooling system 101. The heat exchanger 200 can be the evaporator 103 or the condenser 105, or any other suitable type of heat exchanger 200.

[0075] At block 401, the method includes providing a plurality of structures 203 extending from a substrate 201, the structures 203 being spaced apart by at least a first distance w. The structures 203 may include any means for defining a flow path for the working fluid 113 through the heat exchanger 200. In some embodiments, the plurality of structures 203 may include a plurality of evaporator fins 305 as shown in FIG. 3A or may be any other suitable type or configuration of structures 203.

[0076] At block 403, the method includes providing a braze material 207 overlying at least a portion of the structures 203. The braze material 207 may be provided in a discontinuous configuration such that gaps are provided between portions of the braze material 207. The braze material 207 may be provided in multiple wires 301 as shown in FIG. 3A or in other suitable configurations. The braze material 207 is provided with a thickness d that is less than the first distance w between adjacent structures 203.

[0077] At block 405, the method includes providing at least one cover plate 205 over the ends of the plurality of structures 203. The at least one cover plate 205 is also provided over the brazing material 207 such that the brazing material 207 is located between the ends of the structures 203 and the cover plate 205. The cover plate is spaced a second distance d from the ends of the plurality of structures 203, the second distance being less than the first distance w.

[0078] At block 407, the method further includes heating the braze material 207. The braze material 207 is heated to a temperature above its melting point such that the molten braze material 207 flows into gaps between the cover plate 205 and the ends of the plurality of structures 203.

[0079] The distance w between the adjacent structures 203 and the thickness d of the brazing material 207 are selected such that when the brazing material 207 melts, Laplace pressure causes the brazing material 207 to flow into gaps between the ends of the structures 203 and the at least one cover plate 205. This prevents the brazing material 207 from flowing into the channels formed by the structures 203. This is advantageous in maximizing or substantially maximizing the effective heat transfer area and reducing the total pressure drop within the heat exchanger 200.

[0080] In the above embodiment, the brazing material 207 is provided with a thickness d that is less than the first distance w between the adjacent structures 203. In other embodiments, the brazing material 207 may be provided with a thickness d that is initially greater than the first distance w between the adjacent structures 203. In such embodiments, as the brazing material 207 is heated, the initial Laplace pressure will cause the molten brazing material 207 to initially flow into the gaps between the adjacent structures 203. However, once the brazing material 207 has flowed to a point where its thickness is less than the first distance w between the adjacent structures 203, the Laplace pressure will direct the flow of the brazing material 207 into the gaps between the ends of the structures 203 and the cover plate 205. Flow into the gaps between the adjacent structures 203 is stopped and reversed to maximize or substantially maximize the effective heat transfer area and reduce the total pressure drop within the heat exchanger 200. In such a case, the Laplace pressure difference between the meniscus in the gap between adjacent structures 203 and the edges of the structures 203 and the cover plate 205 drives the flow of the braze material 207 .

[0081] 5A-5D show variations of brazing material 207 that may be used in embodiments of the present application. In these embodiments, the brazing material 207 is provided in a discontinuous configuration rather than a continuous sheet. The discontinuous configuration ensures that there are gaps between portions of the brazing material 207. These gaps provide spacing between the cover plate 205 and the edge of the structure 203 into which molten brazing material 207 can flow.

[0082] The thickness of the brazing material 207 may be selected such that the Laplace pressure of the brazing material 207 causes the brazing material 207 to flow horizontally across the edge of the structure 203. The area covered by the brazing material 207 and the discontinuous configuration used for the brazing material 207 may be selected to provide a sufficient volume of the brazing material 207 such that a reliable and rigid joint is formed.

[0083] In the embodiment of Figure 5A, the brazing material 207 is provided in the plurality of wires 301. The plurality of wires 301 may have a circular or substantially circular cross-section. The plurality of wires 301 may extend perpendicular to the channel formed by the plurality of structures 203. In the embodiment of Figure 5A, the wires 301 are uniformly spaced across the top of the structures 203. The number and spacing of the wires 301 may be selected to control the amount of the brazing material 207 used.

[0084] In the embodiment of Figure 5B, the brazing material 207 is provided in a plurality of dots 501. The dots 501 are provided in an interconnect network 503. The interconnect network 503 has gaps 505 between the dots 501 into which the molten brazing material 207 can flow. The number and size of the dots 501 may be selected to control the amount of brazing material 207 used.

[0085] The brazing material 207 shown in Figure 5C is also provided in the interconnect network 503. In this embodiment, the interconnect network 503 includes a plurality of circular gaps 505. The circular gaps 505 provide spacing into which the molten brazing material 207 can flow. Other shapes for the gaps 505 may be used in other embodiments of the present application. The number of the gaps 505 and the size of the gaps 505 may be selected to control the amount of brazing material 207 used.

[0086] 5D shows another embodiment of an interconnection network 503 of brazing material 207. In this embodiment, the interconnection network 503 may be formed from a plurality of crossed wires 301. In this embodiment, the interconnection network 503 provides a plurality of rectangular gaps 505 for the molten brazing material 207 to flow into. The number of the wires 301 in the interconnection network 503 may be selected to control the amount of brazing material 207 used.

[0087] 4-5D, the substrate 201 has a substantially square shape. Other shapes may be used in other embodiments. In some embodiments, the substrate 201 may have a larger surface area than the heat source to which the substrate 201 and the evaporator 103 are thermally coupled. This may be beneficial in distributing heat across the substrate 201 and provide better thermal performance.

[0088] In some embodiments, the heat exchanger 200 may include additional components not shown in Figures 2-5D. In some embodiments, the heat exchanger 200 may include a stiffener configured to limit bending of the structures 203. The stiffener may include a number of protrusions extending between the structures 203 to hold the structures 203 in place.

[0089] In some embodiments, the heat exchanger 200 may be configured such that at least a portion of the structure 203 extends through the cover plate 205. This may provide a larger surface for the brazing between the structure 203 and the cover plate 205. An additional connection means may be provided at the end of the structure 203 that extends through the cover plate 205. The additional connection means may provide other connections of the structure 203 to the cover plate 205 in addition to the brazing connection. This may provide a more rigid heat exchanger 200, allowing the heat exchanger 200 to withstand high internal operating pressures.

[0090] FIG. 6 shows an example of a heat exchanger 200 including a reinforcement 601 being manufactured. In this example, the heat exchanger 200 is an evaporator 103 having a plurality of structures 203. The reinforcement 601 is configured to strengthen the heat exchanger 200 and reduce deformation of the heat exchanger 200 during use. The reinforcement 601 may be provided in a heat exchanger 200 as shown in FIGS. 2-5D and 7A-8, or in any other suitable type of heat exchanger 200.

[0091] The heat exchanger 200 shown in FIG. 6 includes a substrate 201 and a number of structures 203 as described above.

[0092] The reinforcing structure 601 may be provided as part of the cover plate 205 or as an additional component between an end of the structures 203 and the cover plate 205. In the embodiment shown in Figure 6, the substrate 201 is connected to a first end of the structures 203 and the reinforcing structure 601 is connected to a second end of the structures 203.

[0093] The reinforcing structure 601 includes a number of protrusions 603 extending between the structures 203 to hold the structures 203 in place. The protrusions 603 may be configured to pierce the ends of the structures 203 in place. The protrusions 603 have a length that is much shorter than the structures 203 so that they do not protrude too far into the channels formed by adjacent structures 203. This is advantageous in maintaining the size of the flow passages to allow sufficient working fluid 113 to flow through the passages when the heat exchanger 200 is in use.

[0094] In the embodiment of FIG. 6, the protrusions 603 of the reinforcing structure 601 are formed in an interlocking configuration with the ends of the structures 203. The protrusions 603 are sized and shaped to fit snugly into the gaps between the ends of the structures 203. The protrusions 603 grip the sides of the structures 203 to hold the structures 203 in place. In some embodiments, the protrusions 603 of the reinforcing structure 601 may be brazed to the sides of the structures 203. This is advantageous in preventing movement of the structures 203 relative to the reinforcing structure 601, thus avoiding deformation of the heat exchanger 200.

[0095] 6, all of the structures 203 are coupled to the protrusions 603 of the reinforcement 601. In other embodiments, the protrusions 603 of the reinforcement structure 601 may be coupled to a portion of the structures 203. If the protrusions 603 are coupled to only a portion of the structures 203, the portions may be selected to reduce deformation of the heat exchanger 200. For example, the structures 203 at the center of the heat exchanger 200 are the ones most likely to deform during use, and therefore the protrusions 603 may be configured to be coupled to the structures 203 at the center of the heat exchanger 200.

[0096] 6, the stiffener 601 is provided as a single component that is coupled to all of the structure 203. Different arrangements for the stiffener 601 are provided in other embodiments. For example, multiple different stiffeners 601 may be coupled to different portions of the structure 203.

[0097] 7A and 7B show examples of various shapes that may be used for the heat exchanger 200. FIGS. 7A and 7B show a fabricated heat exchanger 200. In these examples, the heat exchanger 200 is an evaporator 103 having a plurality of structures 203. The heat exchanger 200 may be fabricated using any of the methods described above. These heat exchangers 200 are configured to provide uniform, or substantially uniform, flow of working fluid 113 throughout the heat exchanger 200 to improve thermal performance. The features shown in FIGS. 7A and 7B may be provided in combination with other features of the heat exchanger 200 of any of FIGS. 2-6 or 8.

[0098] In the embodiment of Figures 7A and 7B, the heat exchanger 200 includes the substrate 201 and a number of structures 203 extending from the substrate 201. A cover plate 205 is provided on the structures 203. In the embodiment of Figures 7A and 7B, the heat exchanger 200 is configured to provide a larger flow path for the working fluid 113 to flow towards the center of the substrate 201 than towards the edge of the substrate 201. This is advantageous in providing a uniform flow distribution of the working fluid.

[0099] The substrate 201 is thermally coupled to a heat source 701. A thermal interface material may be provided between the heat source 701 and the substrate 201 for thermal coupling. In the embodiment of Figures 7A and 7B, the substrate 201 is larger than the heat source 701. Making the substrate 201 larger is advantageous for improving heat diffusion, increasing the effective heat transfer area, and reducing the thermal resistance of the heat exchanger 200.

[0100] 7A and 7B, the heat source 701 is located at the center of the substrate 201. The flow channels defined by the structures 203 have different widths to provide a uniform or substantially uniform flow distribution throughout the heat exchanger 200. The flow channels closer to the heat source 701 have a larger size than the flow channels further away. The width of the flow channels used may be designed to achieve a uniform or substantially uniform flow distribution while maintaining the mechanical integrity of the heat exchanger 200.

[0101] In the embodiment of Figure 7A, different channel sizes are achieved by varying the spacing between the structures 203. There is greater spacing between adjacent structures 203 at the center of the substrate 201 than at the edge of the substrate 201. The structures 203 are spaced closer together at the edge of the substrate 201 than at the center of the substrate 201. This results in a channel with a larger width at the center of the substrate 201 and a channel with a smaller width at the edge of the substrate 201.

[0102] 7B, different channel sizes are achieved by providing an inlet portion 703 with a larger channel width at the center of the substrate 201 compared to the edge of the substrate 201. The inlet portion 703 may be machined directly in the cover plate 205.

[0103] In this embodiment, the inlet portion 703 defines the inlet of the heat exchanger 200. The inlet portion 703 shown in FIG. 7B has two different lengths. A first length is provided towards the center of the substrate 201 and a second length is provided at the edge of the substrate 201. Because the first length is shorter than the second length, the inlet is larger at the center of the substrate 201 than at the edge. It should be understood that other configurations of the inlet portion 703 may be used in other embodiments of the present application.

[0104] In both of the embodiments shown in Figures 7A and 7B, the heat exchanger 200 is provided in two parts. In these embodiments, the cover plate 205 comprises a central portion 705 that divides the heat exchanger 200 into different parts.

[0105] The cover plate 205 may be bonded to the substrate 201 and the structure 203 by a brazed joint 707. In the embodiment shown in Figures 7A and 7B, the brazed joint 707 may be formed along the edge of the structure 203 at the edge of the substrate 201. The brazed joint 707 is also formed between a central portion 705 of the cover plate 205 and the structure 203 adjacent to the central portion 705. Such an arrangement of the brazed joint 707 is advantageous for providing a better bond between the substrate 201 and the cover plate 205, and for reducing deformation of the heat exchanger 200 during use.

[0106] Figure 8 shows another embodiment of a heat exchanger 200. In this embodiment, the heat exchanger 200 is an evaporator 103 having a plurality of structures 203. The features shown in Figure 8 may be provided in combination with other features of the heat exchanger 200 of any of Figures 2 to 7B.

[0107] The heat exchanger 200 includes the substrate 201, a number of structures 203 extending from the substrate 201, and a cover plate 205. At least a portion of the number of structures 203 extend through the cover plate 205. The substrate 201 is thermally coupled to a heat source 701. The cover plate 205 is joined to the substrate 201 and the structures 203 by a braze joint 707.

[0108] A coupling means 801 is provided at the end of the structure 203 that extends through the cover plate 205. The coupling means 801 may include the braze material or any other suitable means.

[0109] The connecting means 801 may provide additional strength in addition to the brazed joint 707 between the cover plate 205 and the structure 203 and / or the substrate 201. The additional connecting means 801 may avoid deformation of the heat exchanger 200 during use.

[0110] 9 illustrates the manufacture of an exemplary two-phase cooling system 101 including the evaporator 103 and the condenser 105. The evaporator 103 and the condenser 105 are heat exchangers 200 shown in any of Figures 2-8 or may include any combination of the features shown in Figures 2-8.

[0111] The evaporator 103 may be placed in an additional frame before being installed in a system such as a server for use. The additional frame may be a rigid frame made of plastic or any other suitable material. The rigid frame may prevent people from directly touching the evaporator 103 to prevent the evaporator 103 from being damaged. The additional frame may also act as a thermal insulator to avoid unwanted airflow affecting the evaporator 103.

[0112] The evaporator 103 and the condenser 105 may be vacuum brazed to form the two-phase cooling system 101. Vacuum brazing the evaporator 103 mechanically bonds the cover plate 205 to the substrate 201 and the evaporator fins 305. Vacuum brazing the condenser 105 mechanically bonds the two cover plates 205 to the substrate 201 or other suitable components. The substrate 201 of the condenser 105 may be comprised of a double fin plate or other suitable type of plate.

[0113] The evaporator 103 and the condenser 105 are connected to the riser 109 and downcomer 107 via a junction 901, as shown by the arrows. The junction 901 forms a closed loop of the two-phase cooling system 101. The junction 901 may have the same inlet diameter as the downcomer 107 and the riser 109. This is advantageous to avoid pressure drops within the two-phase cooling system 101 and to maximize or substantially maximize passive flow circulation.

[0114] The various components of the two-phase cooling system 101 may be connected to each other by any suitable means. In the embodiment of Figure 9, the evaporator 103 and the condenser 105 are connected to the riser pipe 109 and the downcomer pipe 107 by laser spot welding the inner periphery of the joint 901.

[0115] 9, the two-phase cooling system 101 further includes a fill port 903. The fill port 903 is capable of providing working fluid 113 to the two-phase cooling system 101. The fill port 903 is provided in the downcomer 107. In this embodiment, the fill port 903 is provided at the top of the downcomer 107 close to the condenser 105.

[0116] The term "comprises" as used herein is intended to have an inclusive rather than an exclusive meaning, i.e., any reference to X containing Y indicates that X may contain only one Y or may contain two or more Ys.

[0117] According to this specification, various embodiments may be referenced. A description of a feature or function with respect to an embodiment indicates that the feature or function is present in that embodiment. The term "embodiment," "for example," "may," or "may" used herein, whether or not explicitly stated, indicates that such feature or function is present in at least the described embodiment, whether or not stated in the embodiment, and may, but need not, be present in some or all of the other embodiments. Thus, the term "embodiment," "for example," "may," or "may" used herein indicates a particular embodiment in a class of embodiments. The properties of an embodiment may be properties that belong only to that embodiment, properties of that class, or properties of a subclass of that class (including some, but not all, of the embodiments). Thus, a feature described with reference to one embodiment and not described with reference to another embodiment is implicitly indicated to the extent possible, but not necessarily to be used in other embodiments as part of a working combination.

[0118] Although the embodiments of the present application have been described in detail as in the above paragraphs, the present application is not limited to the above embodiments. It should be understood that any modifications, equivalent replacements, improvements, etc. made under the concept and principles of the present application are within the scope of protection of the present application.

[0119] Features set out in the above description may be used in combinations other than those explicitly set out above.

[0120] Although functions have been described with reference to particular functions, those functions may be performed by other functions, whether or not described.

[0121] Although features have been described with reference to particular embodiments, those features may also be present in other embodiments, whether or not they are described.

[0122] The term "a" or "the" referred to in this application is intended to have an inclusive, not an exclusive, meaning that "X includes Y / the" refers to X including only one Y or two or more Y, unless the context clearly indicates otherwise. If an exclusive "a" or "the" is intended to be used, the context must clearly indicate this. In some cases, the inclusive meaning may be emphasized by using "at least one" or "one or more", but the absence of these terms should not be considered as an inference to an exclusive meaning.

[0123] A feature (or combination of features) in a claim refers to the feature or (combination of features) itself, as well as features capable of achieving substantially the same technical effect (equivalent features). Equivalent features include, for example, modified features that achieve substantially the same result in substantially the same way. Equivalent features include, for example, features that perform substantially the same function in substantially the same way to achieve substantially the same result.

[0124] In this specification, various embodiments may be referred to using adjectives or adjectival phrases to describe features of the embodiments. The description of a property with respect to an embodiment indicates that the property is present in some embodiments specifically as described, and in other embodiments substantially as described.

[0125] Although an effort has been made in the above specification to direct attention to what are believed to be the key features, applicants should understand that they may seek protection through the claims to protect any patentable feature or combination of features shown in the above drawings and / or drawings, whether or not emphasized. [Explanation of symbols]

[0126] 101 Two-phase cooling system 103 Evaporator 105 Condenser 105 Liquid-cooled condenser 107 Downcomer 109 Ascending Pipe 111 Heat source 113 Working Fluid 117 Liquid phase 121 Vapor Phase 125 Coolant 200 heat exchanger 200 Two-phase heat exchanger 201 Substrate 203 Structure 205 Lid plate 301 Wiring 301 Wire 305 Evaporator fin 401, 403, 405, 407 blocks 501 dots 503 Interconnection Network 505 Gap, circular gap 601 Reinforcement 601 Reinforcement structure 603 Protrusion 701 Heat source 703 Entrance 705 Central part 707 Joint 801 Coupling means 901 Joint 903 Filling port

Claims

1. A heat exchanger comprising: a plurality of structures extending from a substrate, adjacent structures defining flow paths for a working fluid through the heat exchanger, the structures being spaced apart at least a first distance; at least one cover plate disposed on an end of the plurality of structures so as to be spaced from the end of the plurality of structures by a second distance less than the first distance; the at least one cover plate is brazed to the plurality of structures by a braze material provided between the ends of the plurality of structures and the at least one cover plate, the braze material being provided in a discontinuous configuration such that gaps are provided between portions of the braze material such that braze joints are formed from the braze material flowing into the spaces between the at least one cover plate and the ends of the plurality of structures; and a reinforcement including a plurality of protrusions configured to extend between the plurality of structures to limit flexing of the plurality of structures. heat exchanger.

2. The braze material is provided at a thickness less than the first distance.

2. The heat exchanger of claim 1.

3. the first distance and the second distance are selected such that Laplace pressure causes the brazing material to flow into gaps between the ends of the plurality of structures and the at least one cover plate.

3. A heat exchanger according to claim 1 or 2.

4. the plurality of structures extend substantially perpendicularly from the substrate; 2. The heat exchanger of claim 1.

5. the structures are spaced closer together at an edge of the substrate than at a center of the substrate; 2. The heat exchanger of claim 1.

6. At least some of the structures extend through the at least one cover plate, and further coupling means are disposed on ends of the structures that extend through the at least one cover plate.

2. The heat exchanger of claim 1.

7. the plurality of structures includes fins; 2. The heat exchanger of claim 1.

8. The heat exchanger includes an evaporator or a condenser.

2. The heat exchanger of claim 1.

9. providing a plurality of structures extending from a substrate, the plurality of structures defining a flow path for a working fluid through the heat exchanger and spaced apart by at least a first distance; providing a braze material overlying at least a portion of the plurality of structures, the braze material being provided in a discontinuous configuration such that gaps are provided between portions of the braze material; providing at least one cover plate disposed on an end of the plurality of structures such that the cover plate is spaced a second distance from the end of the plurality of structures that is less than the first distance; providing a stiffener including a plurality of protrusions configured to extend between the plurality of structures to limit bending of the plurality of structures; and heating the brazing material such that the brazing material flows into gaps between the at least one cover plate and the ends of the plurality of structures. method.

10. The braze material is provided at a thickness less than the first distance.

10. The method of claim 9.

11. the first distance and the second distance are selected such that Laplace pressure causes the brazing material to flow into gaps between the ends of the plurality of structures and the at least one cover plate.

10. The method of claim 9.

12. A heat exchanger comprising: A substrate; a plurality of structures extending from the substrate that define a flow path for a working fluid through the heat exchanger; and at least one stiffener including a plurality of protrusions configured to extend between the plurality of structures to reduce flexing of the plurality of structures; heat exchanger.

13. The heat exchanger includes a cover plate having the at least one reinforcement member provided as part of the cover plate.

13. The heat exchanger of claim 12.

14. The substrate is configured to provide a larger flow path for the flow of working fluid toward the center of the substrate than toward the edge of the substrate, by providing a larger gap between adjacent structures at the center of the substrate than the gap between adjacent structures at the edge of the substrate, or by providing an inlet portion defining an inlet of the heat exchanger and setting a first length of the inlet portion provided at the center of the substrate to be shorter than a second length of the inlet portion provided at the edge of the substrate, 13. The heat exchanger of claim 12.

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