WO2025072408A1

WO2025072408A1 - Server with hybrid thermal management system

Info

Publication number: WO2025072408A1
Application number: PCT/US2024/048519
Authority: WO
Inventors: Arindom Joardar; Richard Lord; Tikhon Suresh Pichai
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2023-09-29
Filing date: 2024-09-26
Publication date: 2025-04-03
Anticipated expiration: 2026-03-29

Abstract

A cooling system for cooling an assembly including at least one heat-generating electronic device mounted to a printed circuit board includes a source of a first cooling fluid and a spray nozzle fluidly coupled to the source of the first cooling fluid. An outlet of the spray nozzle is oriented to spray the first cooling fluid onto a surface of the at least one heat¬ generating electronic device.

Description

SERVER WITH HYBRID THERMAL MANAGEMENT SYSTEM

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Application No. 63/586523, filed on September 29, 2023, which is incorporated herein by reference in its entirety.

BACKGROUND

[0001] Exemplary embodiments pertain to the art of thermal management, and more particularly, relate to thermal management of a server within a data center.

[0002] A “data center” refers to the physical location of one or more servers. A data center and the servers housed within a data center typically consume a significant amount of electrical power. Existing servers are designed to be cooled at least partially by a flow of air. Such servers usually include one or more printed circuit boards having a plurality of operable heat-generating devices mounted thereto. The printed circuit boards are commonly housed in an enclosure having vents configured to direct external air from the data center into, through and out of the enclosure. The air absorbs heat dissipated by the components and after being exhausting from the enclosure, mixes with the ambient air. An air conditioner is then used to cool the heated air of the data center and to recirculate it, repeating the cooling process.

[0003] Higher performance server components typically dissipate more power. However, the amount of heat that conventional cooling system can remove from a server is in part limited by the extent of the air conditioning available from the data center. In general, a lower air temperature in a data center allows each server component cooled by an air flow to dissipate a higher power, and thus allows each server to operate at a correspondingly higher level of performance.

BRIEF DESCRIPTION

[0004] According to an embodiment, a cooling system for cooling an assembly including at least one heat-generating electronic device mounted to a printed circuit board includes a source of a first cooling fluid and a spray nozzle fluidly coupled to the source of the first cooling fluid. An outlet of the spray nozzle is oriented to spray the first cooling fluid onto a surface of the at least one heat-generating electronic device.

[0005] In addition to one or more of the features described herein, or as an alternative, further embodiments may include the at least one heat-generating electronic device is a peripheral heat-generating device. [0006] In addition to one or more of the features described herein, or as an alternative, further embodiments may include the source of the first cooling fluid is fluidly coupled to the printed circuit board.

[0007] In addition to one or more of the features described herein, or as an alternative, further embodiments may include the source of the first cooling fluid is a reservoir positioned underneath the printed circuit board.

[0008] In addition to one or more of the features described herein, or as an alternative, further embodiments may include at least one fluid movement device for moving a vapor portion of the first cooling fluid relative to the assembly and a secondary component located downstream from the at least one heat-generating electronic device relative to a flow of the vapor portion of the first cooling fluid.

[0009] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the secondary component is a heat exchanger. The flow of the vapor portion of the first cooling fluid is arranged in a heat transfer relationship at the secondary component.

[0010] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the at least one heat-generating electronic device includes a plurality of heat-generating electronic devices and the heat exchanger is located upstream from the plurality of heat- generating electronic devices.

[0011] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the at least one heat-generating electronic device includes a plurality of heat-generating electronic devices and the heat exchanger is located downstream from the plurality of heat-generating electronic devices.

[0012] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the at least one heat-generating electronic device includes a plurality of heat-generating electronic devices. The spray nozzle is associated with one of the plurality of heat-generating electronic devices and the heat exchanger is associated with another of the plurality of heat-generating electronic devices.

[0013] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the plurality of heat-generating electronic devices includes at least one main heat-generating electronic device and at least one peripheral heatgenerating electronic device. The spray nozzle is associated with the at least one peripheral heat-generating electronic device and the heat exchanger is associated with the at least one main heat-generating electronic device. [0014] According to an embodiment, a method of cooling an assembly including at least one heat-generating electronic device includes spraying a first cooling fluid via a spray nozzle onto a surface of at least one heat-generating electronic device to cool the at least one heat-generating electronic device and collecting a liquid portion of the first cooling fluid within a reservoir, the reservoir being fluidly coupled to the spray nozzle.

[0015] In addition to one or more of the features described herein, or as an alternative, further embodiments may include moving a vapor portion of the first cooling fluid within the assembly via a fluid movement device.

[0016] In addition to one or more of the features described herein, or as an alternative, further embodiments moving a vapor portion of the first cooling fluid may include entraining the vapor portion of the first cooling fluid within a second cooling fluid.

[0017] In addition to one or more of the features described herein, or as an alternative, further embodiments may include condensing the vapor portion of the first cooling fluid into a condensed first cooling fluid at a secondary component.

[0018] In addition to one or more of the features described herein, or as an alternative, further embodiments the secondary component is a heat exchanger and condensing the vapor portion of the first cooling fluid may include arranging the second cooling fluid and the vapor portion of the first cooling fluid in a heat transfer relationship with a third cooling fluid at the heat exchanger.

[0019] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the at least one heat-generating electronic device includes a plurality of heat-generating electronic devices and the heat exchanger is located upstream from the plurality of heat- generating electronic devices.

[0020] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the at least one heat-generating electronic device includes a plurality of heat-generating electronic devices and the heat exchanger is located downstream from the plurality of heat-generating electronic devices.

[0021] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the at least one heat-generating electronic device includes a plurality of heat-generating electronic devices. The spray nozzle is associated with one of the plurality of heat-generating electronic devices and the heat exchanger is associated with another of the plurality of heat-generating electronic devices.

[0022] In addition to one or more of the features described herein, or as an alternative, further embodiments may include that the plurality of heat-generating electronic devices includes at least one main heat-generating electronic device and at least one peripheral heatgenerating electronic device. The spray nozzle is associated with the at least one peripheral heat-generating electronic device and the heat exchanger is associated with the at least one main heat-generating electronic device.

[0023] In addition to one or more of the features described herein, or as an alternative, further embodiments may include collecting the condensed first cooling fluid at the secondary component.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike:

[0025] FIG. 1 is a front view of a data center rack having a plurality of servers mounted therein;

[0026] FIG. 2 is a perspective view of a server according to an embodiment;

[0027] FIG. 3A is a top view of a server according to an embodiment;

[0028] FIG. 3B is a cross-sectional side view of the server of FIG. 3A according to an embodiment;

[0029] FIG. 4 is a side view of a spray nozzle of a cooling system according to an embodiment;

[0030] FIG. 5 is a schematic diagram of a cooling system of a server according to an embodiment;

[0031] FIG. 6 is a cross-sectional view of a heat removal device of a cooling system suitable for use with the server according to an embodiment;

[0032] FIG. 7 is a cross-sectional view of a heat spreader having an integral fluid circuit according to an embodiment;

[0033] FIG. 8 is a schematic diagram of a portion of a circuit of the second cooling fluid of a cooling system according to an embodiment;

[0034] FIG. 9 is a schematic diagram of a circuit of the primary cooling fluid of a cooling system according to an embodiment; and

[0035] FIG. 10 is a plan view of a secondary component of the cooling system operable to condense a vapor first cooling fluid according to an embodiment. DETAILED DESCRIPTION

[0036] A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.

[0037] With reference now to FIG. 1, an example of a data center 20 is illustrated. As shown, the data center 20 includes a cabinet 22 having at least one, and in some embodiments, a plurality of slots (not shown) formed therein. One or more server rack sub-assemblies, also referred to herein as servers 30 may be permanently or removably mountable within the cabinet 22, such as within the one or more slots formed therein. The plurality of slots, and therefore the at least one server 30 receivable therein, may have a generally vertical orientation (shown), or alternatively, may have a horizontal orientation. In some embodiments, the data center 20 may include a combination of both horizontally oriented and vertically oriented slots. Further, although only a single cabinet 22 is illustrated in the FIG., it should be appreciated that the data center 20 may include several cabinets 22. In embodiments including a plurality of cabinets 22, the plurality of cabinets 22 may be arranged at the same location within a building, or alternatively, one or more of the cabinets 22 may be arranged at a different location within a single building or within multiple buildings.

[0038] With reference now to FIGS. 2 and 3A, an example of a server 30 receivable within a slot of the cabinet 22 is illustrated. As shown, the server 30 may include a frame or chassis 32 having at least one printed circuit board 34 mounted to the frame. Although only a single printed circuit board 34 is illustrated in the FIG., it should be understood that in some embodiments, a plurality of printed circuit boards may be mounted to the chassis 32. The chassis 32 is designed to be insertable, for example slidably insertable, into a slot of a server rack and allow for connection to power cables, data cables, and/or other connecting cables provided at or by the cabinet 22.

[0039] The chassis 32 may include a plurality of walls 36, 38, 39, and 40 oriented at an angle to the printed circuit board 34 and that extend about all or at least a portion of a periphery of the printed circuit board 34. In an embodiment, the chassis 32 includes at least one flat, generally planar panel connected to one or more of the peripheral walls 36, 38, 40 of the chassis 32. The at least one flat panel 42 may be arranged at either a first side or a second side of the printed circuit board 34. When the server 30 is in a horizontal orientation as shown, such a flat panel 42 may be vertically offset from the printed circuit board 34, either above or underneath the printed circuit board. In some embodiments, best shown in FIG. 3B, a flat panel 42 may be arranged both above and below the printed circuit board. In an embodiment, the chassis 32 in combination with the flat panels 42 form a sealed, air-tight container surrounding the server 30. However, embodiments where a separate jacket or container is positioned about the server 30 to form an air-tight assembly are also contemplated herein. Additionally, embodiments involving air exchanges with ambient are also within the scope wherein ambient air is drawn into the server which extracts heat from the heat generating components and is then discharged out with or without thermal management.

L0040 J At least one heat-generating electronic device 50 may be mounted or electrically connected to the printed circuit board 34. Examples of a heat-generating electronic device 50 include but are not limited to a processor such as a central processing unit and/or graphics processing unit, a memory, a hard drive, and a power supply module. A server 30 may also include one or more components that are not mounted to or are not electrically connected to the printed circuit board 34. In embodiments where the server 30 includes two or more of the same type of component, such as central processing units for example, the components may be aligned along an axis extending between the lateral sides 36, 38 of the chassis 32, may be aligned along an axis extending between the front and back of the chassis 32, or may be offset from one another in one or more directions. It should be appreciated that any heat-generating electronic device 50 may be located at any position within the chassis 32 or about the circuit board 34.

[0041] In an embodiment, one or more fluid movement devices 52 are mounted to the printed circuit board 34 and are operable to move a flow of a fluid, such as air over the heatgenerating electronic devices 50. In the illustrated, non-limiting embodiment, the at least one fluid movement device is a fan 52 arranged near a first end 54 of the printed circuit board 34 such that when the server 30 is installed within the cabinet 22 the at least one fan 52 is positioned closer to the front of the cabinet 22 than the heat-generating electronic devices 50. However, embodiments where one or more fluid movement devices 52 are arranged at another suitable location, such as near a second end 56 of the printed circuit board 34 or of the chassis 32 associated with the rear of the cabinet 22 for example, are also within the scope of the disclosure. It should be appreciated that a server 30 having any suitable configuration, including servers having a full width or a half width or sled configuration are within the scope of the disclosure.

[0042] In an embodiment, the fluid moved by the at least one fluid movement devices 52 is configured to make a single pass over the heat-generating electronic devices 50. For example, cool air may be drawn into a fan 52 from a location adjacent to the front of the chassis 32 and after removing heat from the heat-generating electronic devices 50, may be exhausted at the back of the chassis 32. It should be appreciated that the air exhausted from the back of the cabinet 22 may be the same temperature as the surrounding environment, warmer than the surrounding environment, or even cooler than the surrounding environment. In other embodiments, such as where the chassis 32 includes at least one flat panel 42 for example, the fluid may be configured to continuously circulate within the server 30. For example, as best shown in FIG. 3B, a fluid movement device 52 may push the flow of fluid across the heatgenerating electronic devices 50 arranged at a first surface 58 of the printed circuit board 34. Upon reaching the second end 56 of the printed circuit board 34, the fluid may turn through one or more openings and make a second pass along the second, opposite surface 60 of the printed circuit board 34. Upon reaching the first end 54 of the printed circuit board 34, the fluid may turn again, and be drawn back into an inlet of the at least one fluid movement device 52.

[0043] The server 30 may include a cooling system 100 for removing heat from one or more of the heat-generating electronic devices 50. The cooling system 100 is operable to cool at least one heat-generating electronic device 50 using a first cooling fluid C 1. In the illustrated, non-limiting embodiment, the at least one heat-generating electronic device 50 cooled by the first cooling fluid Cl may be considered a peripheral heat-generating device 62.

[0044] As used herein, the term “peripheral heat-generating device” is intended to describe a heat-generating component that is a not a microchip. A microchip typically defines a package of several integrated circuits arranged on a semiconductor material. Examples of microchips include but are not limited to central processing units (CPUs) and graphics processing units (GPUs). A microchip may be considered a main heat-generating device 64 and is distinguishable from a peripheral heat-generating device 62. In an embodiment, a peripheral heat-generating device generates less heat than a main heat-generating device. For example, a peripheral heat- generating device may be configured to generate less than 25% of the heat of the server, and in some embodiments less than 20%, less than 19%, less than 18%, less than 17%, less than 16%, less than 15%, less than 14%, less than 13%, less than 12%, less than 11%, or less than 10%. However, it should be appreciated that any of the components of the server 30 may be designed as the at least one peripheral heat-generating electronic device 62 directly cooled by the first cooling fluid Cl and any of the components of the server 30 may be designed as a main heat-generating electronic device 64.

[0045] With reference to FIGS. 4 and 5, in an embodiment, the cooling system 100 includes at least one spray nozzle 102 associated with one or more peripheral heat-generating electronic devices 62. Although a single spray nozzle 102 is illustrated as being oriented to direct a spray of a first cooling fluid Cl onto a single peripheral heat-generating electronic device 62, embodiments where a plurality of spray nozzles 102 are associated with a single peripheral heat-generating electronic device 62 are also contemplated herein. Similarly, embodiments where a single spray nozzle 102 is positioned to spray a first cooling fluid Cl onto a surface of multiple peripheral heat-generating electronic devices 62 are also within the scope of the disclosure. The first cooling fluid Cl output from the one or more spray nozzles 102 onto an adjacent surface of one or more peripheral heat-generating electronic devices 62 may be a dielectric fluid, refrigerant, water, or another suitable fluid. It should be appreciated that although the first cooling fluid Cl is illustrated and described herein as being sprayed in a manner that suitably controls the direction of the spray of first cooling fluid Cl, in other embodiments, the first cooling fluid Cl may be dispersed as droplets without any directional control. In such embodiments, the first cooling fluid expelled from a nozzle 102 may be configured to travel in a plurality of directions. In such embodiments, the spray or droplets of first cooling fluid Cl may be used to target areas that are difficult to reach directly.

[0046] The first cooling fluid Cl may be in a liquid state when expelled from the spray nozzle 102 onto a surface of at least one heat-generating electronic device 50, such as a peripheral heat-generating electronic device 62. As the cool first cooling fluid Cl contacts one or more hot surfaces of at least one peripheral heat-generating electronic device 62, heat is absorbed by the first cooling fluid Cl , thereby cooling the peripheral heat-generating electronic device 62. In some embodiments, the heated first cooling fluid Cl remains a liquid that generally puddles or accumulates on the surface of the peripheral heat-generating electronic device 62 and/or the surrounding printed circuit board 34. In such embodiments, the puddle of first cooling fluid Cl may be configured to drain to a reservoir 104 of first cooling fluid Cl. The one or more spray nozzles 102 may be fluidly coupled to the reservoir 104 via one or more conduits, illustrated at 108, such that the first cooling fluid Cl is recirculated within the cooling system 100. In an embodiment, as shown in FIG. 5, one or more opening or holes 106 may be formed in the printed circuit board 34 surrounding the peripheral heat-generating electronic device 62. The reservoir 104 may be positioned vertically underneath the holes 106 such that the first cooling fluid Cl drains directly there into. Alternatively, the reservoir 104 may be located at another location and the holes 106 and/or the puddle configured to form on or around the peripheral heat-generating electronic device 62 may be fluidly connected to the reservoir 104 via one or more conduits (not shown).

[0047] In other embodiments, the contact between the first cooling fluid Cl and one or more hot surfaces of at least one peripheral heat-generating electronic device 62 may cause at least a portion of the first cooling fluid Cl to vaporize. In such embodiments, the liquid portion of the first cooling fluid Cl, or the portion that does not vaporize, may collect on the surface of the peripheral heat-generating electronic device 62 and/or the surrounding printed circuit board 34 and may drain to a reservoir 104 as previously described. The vapor portion of the first cooling liquid Cl may be moved via the one or more fluid movement devices 52 relative to the server 30. For example, the vapor portion of the first cooling liquid Cl may become entrained within a second cooling fluid C2 circulating through the server 30 via the fluid movement devices 52. The vapor portion of the first cooling liquid Cl and the second cooling fluid C2 may be moved into contact with one or more secondary components, such as a heat sink or a heat exchanger; however, it should be appreciated that any suitable component may be operable as a secondary component.

[0048] In such embodiments where a portion of the first cooling liquid Cl is entrained within the second cooling fluid C2, the server 30 may be hermetically sealed or may at least have an air-tight enclosure to prevent the loss of the first cooling fluid Cl therefrom. The secondary component may be cool or cold such that the interaction between the vapor first cooling liquid Cl, such as entrained within the second cooling liquid C2, and the secondary component causes the vapor first cooling liquid C 1 to condense on a surface of the secondary component. The condensed first cooling liquid Cl may be configured to drain from the secondary component to the reservoir 104 to recirculate the first cooling fluid Cl within the cooling system 100.

[0049] With reference now to FIG. 6, in some embodiments, the cooling system 100 additionally includes one or more heat removal devices 120, such as a heat exchanger for example. In an embodiment, the heat removal device 120 is mounted in an axially overlapping relationship with and is thermally coupled to at least one heat-generating electronic device 50. The at least one heat removal device 120 may be mounted to one or more main heat-generating electronic devices 64. However, embodiments where a heat removal device 120 is mounted to a peripheral heat- generating electronic device 62 that does not have a spray nozzle 102 associated therewith, and/or is mounted at another location of the server 30, remote from the heat-generating electronic devices 50 are also within the scope of the disclosure.

[0050] With reference to the cross-sectional view of the heat removal device shown in FIG. 6, the heat exchanger 120 may be a microchannel heat exchanger having a plurality of substantially parallel microchannel heat exchanger tubes 122 extending between an inlet header 124 and an outlet header 126, each of the plurality of heat exchanger tubes 122 defining a plurality of fluid flow paths (not shown). However, examples of other types of heat exchangers that may be used, include, but are not limited to, microtube, double pipe, shell and tube, tube and fin, plate, plate and shell, adiabatic shell, plate fin, pillow plate, and fluid heat exchangers. The type of heat exchanger selected may depend at least in part based on the type of fluids being provided thereto.

[0051] The second cooling fluid C2 and a third cooling fluid C3 are arranged in a heat transfer relationship at the heat exchanger 120. In the non- limiting embodiment illustrated in FIG. 6, the heat exchanger 120 has a single pass configuration for both the second cooling fluid C2 and the third cooling fluid C3. However, in other embodiments, at least one of the second and third cooling fluids C2, C3 may make multiple passes through the heat exchanger 120. Further, the second and third cooling fluids C2, C3 may be arranged in any suitable flow configuration at the heat exchanger, such as a cross-flow, a parallel flow, a counter-flow, or any combination thereof.

[0052] When the heat exchanger is thermally coupled to a heat-generating electronic device 50, in some embodiments, the heat exchanger 120 is directly coupled to a surface of the at least one main heat-generating electronic device 64. However, in other embodiments, as shown in FIG. 6, the heat exchanger 120 is indirectly coupled to the at least one main heatgenerating electronic device 64. In server applications, the surface area of the main heatgenerating electronic devices (i.e., CPUs, GPUs, etc.,) available may very small. Because the amount of heat to be dissipated from a main heat-generating device 64 is typically very high, the surface area available to form an interface with a heat removal device 120 is in sufficient to meet the cooling demand of the heat-generating electronic device. Accordingly, in the illustrated, non-limiting embodiment, a heat spreader 130, such as formed from a conductive material like sheet metal for example, is affixed to the printed circuit board 34 adjacent to a main heat-generating electronic device 64. Although the heat spreader 130 is illustrated as axially overlapping both the at least one main heat-generating electronic device 64 and the printed circuit board 34, embodiments where the heat spreader is arranged at another location relative to the at least one main heat-generating electronic device 64 are also contemplated herein.

[0053] A thermal interface material 132 may be arranged between a surface 134 of the at least one main heat-generating electronic device 64 and an adjacent surface 136 of the heat spreader 130 to facilitate the transfer of heat from the at least one main heat-generating electronic device 64 to the heat spreader 130. The surface area of the surface 136 of the heat spreader facing the at least one main heat-generating electronic device 64 may be greater than, equal to, or in some embodiments, may even be smaller than the surface area of the surface 134 of the at least one main heat-generating electronic device 64. [0054] The heat exchanger 120 is thermally coupled to a second, opposite surface 138 of the heat spreader 130. In an embodiment, the second, opposite surface 138 of the heat spreader 130 is greater than the surface of the at least one main heat-generating electronic device 64 to facilitate the transfer of heat from the heat spreader 130 to a fluid within the heat exchanger 120, such as the third cooling fluid C3 for example. For example, the surface area of surface 134 of the heat spreader 130 may be at least 30% greater than that of the surface of the at least one main heat-generating electronic device 64, and in some embodiments, is at least 40%, 50%, 60%, 70%, 80%, 90%, 100%, or more than 100% greater than the surface 134 of the at least one main heat-generating electronic device 64. However, in other embodiments, the surface area of the second surface 138 of the heat spreader 130 may be the same or even smaller than the surface area of the at least one selected main heat-generating electronic device 64. In the illustrated, non-limiting embodiment, the inlet header 124 is positioned directly adjacent to the heat spreader 130 and may be thermally coupled thereto via a thermal interface material 140. The inlet header 124 of the heat exchanger 120 may be fluidly connected to a fluid inlet 142 and the outlet header 126 may be fluidly connected to a fluid outlet 144 to form a flow path of the third cooling fluid C3.

[0055] In operation, the third cooling fluid C3, such as a refrigerant for example, is provided from the fluid inlet 142 into the inlet header 124 of the heat exchanger 120. The third cooling fluid C3provided to the inlet header 124 may be a single phase, such as a cool or cold liquid for example, or alternatively, may be a two-phase mixture of liquid and vapor. Within the inlet header 124, at least a portion of the heat transferred to the first surface 136 of the heat spreader 130 from the at least one main heat-generating electronic device 64 is transferred from the second surface 138 of the heat spreader 130 to the third cooling fluid C3. The heat transferred to the third cooling fluid C3within the inlet header 124 causes the temperature of the third cooling fluid C3to increase, and in some embodiments, causes at least a portion of the third cooling fluid C3within the inlet header 124 to vaporize.

[0056] In an embodiment, a surface of the heat exchanger 120, such as a bottom surface 146 within the inlet header 124 for example, is optimized to facilitate boiling of the third cooling fluid C3within the inlet header 124. This optimization may include the formation of a specific microstructure at the surface. In an embodiment, this optimization is performed via application a coating or film 148 applied to the surface 146. Alternatively, this optimization may be performed via a machining process or another suitable manufacturing process.

[0057] As the third cooling fluid C3vaporizes, the gaseous third cooling fluid C3 having some liquid third cooling fluid C3 entrained therein flows through the plurality of heat exchange tubes 122 of the heat exchanger 120 toward the outlet header 126. The second cooling fluid C2 is configured to flow through the gaps 150 defined between adjacent heat exchanger tubes 122. In an embodiment, the second cooling fluid C2 is a flow of air moved (in a direction extending into the plane of the page) by the at least one fluid movement device 52 associated with the server 30. However, it should be understood that any fluid, including a liquid such as a dielectric fluid for example, may be used as thesecond cooling fluid C2.

LOO58 J In the illustrated, non-limiting embodiment, a plurality of fins 152 is arranged within the gaps 150 defined between adjacent heat exchanger tubes; however, embodiments that do not include such fins are also contemplated herein. Within the plurality of passages 150 of the heat exchange tubes 122, heat from the second cooling fluid C2 is transferred to the third cooling fluid C3. The resulting cooled second cooling fluid C2 provided at an outlet of the heat exchanger 120 may be configured to flow over the peripheral heat-generating electronic devices 62 of the server 30 and/or any downstream main heat-generating electronic devices 64. Similarly, the now warmer third cooling fluid C3 is received from the plurality of heat exchange tubes 122 within the outlet header 126 is provided to the fluid outlet 144.

[0059] As best shown in FIG. 6, at least one valve V may be arranged at the first fluid inlet 142 and/or the first fluid outlet 144 to control the flow of the third cooling fluid C3 to and from the heat exchanger 120. In an embodiment, the position of the valve(s) V and therefore the flow through the heat exchanger 120, is actively managed based on a thermal load at the heat exchanger 120. The thermal load may be determined on information collected by one or more sensors, represented schematically at T. In the illustrated, non-limiting embodiment, a first sensor is operable to monitor the temperature of the heat spreader 130, and a second sensor is operable to monitor the temperature of the third cooling fluid C3 at the outlet header 126. The at least one sensor T may be operable to measure temperature directly or may be configured to monitor another parameter that correlates to or can be used to derive temperature therefrom.

[0060] In an embodiment, the heat spreader 130 of the heat removal device 120 is a cold plate having an internal fluid circuit. An example of an internal fluid circuit of the heat spreader 130 is illustrated in the cross-sectional view of the heat spreader shown in FIG. 7. As shown, the fluid circuit 200 includes a fluid inlet 202 and a fluid outlet 204 formed in the body of the heat spreader 130. The fluid inlet 202 and the fluid outlet 204 can be any shape, such as in the depth dimension (e.g., in the z-x plane of the attached figure), including the shape of a circle, oval, triangular, square, rectangular, or any simple polygonal shape or portion thereof. Also, in an embodiment, the fluid outlet 204 can have a much larger diameter compared to the fluid inlet 202, thereby helping to reduce the pressure drop for the cooling medium passing through the fluid outlet 204.

[0061] In an embodiment, the fluid circuit includes a single continuous flow path extending between the fluid inlet 202 and the fluid outlet 204. However, in other embodiments, the fluid circuit 200 includes a first or inlet manifold 206, a second or outlet manifold 208, and at least one fluid passage 210 connecting the first and second manifolds 206, 208. In an embodiment, the at least one fluid passage 210 includes a plurality of fluid passages 210. The fluid inlet 202 can be configured to connect a source of a fourth cooling medium C4 to the inlet manifold 206 using any suitable mechanical connection. The fourth cooling medium C4 may be the same as either the second cooling fluid C2 or the third cooling fluid C3 or may be distinct or different therefrom.

[0062] In an embodiment, one or more fluid passages 210 of the fluid circuit 200 may be positioned to perform localized cooling at the area of the heat spreader with the greatest heat flux, such as at the area of the heat spreader directly aligned with or in overlapping arrangement with a heat-generating electronic module. Accordingly, the at least one fluid passage 210 may be associated with a heat-generating electronic device 50. In embodiments where the heat spreader is associated with a plurality of heat-generating electronic modules, one or more fluid passages 210 may be associated with and configured to remove heat from a respective heatgenerating electronic module. More specifically, the at least one fluid passage 210 associated with a respective heat-generating electronic device 50 may be physically located within the heat spreader 130 in alignment with the heat-generating electronic device 50. Inclusion of a fluid circuit 200 within the heat spreader 130 may reduce the size of the heat removal device 120 of the cooling system 100.

[0063] With reference now to FIG. 8, an example of a circuit of the third cooling fluid C3 of the cooling system 100 is illustrated. In the illustrated, non-limiting embodiment, the circuit of the third cooling fluid C3 of the cooling system 100 is a closed loop and includes a pump 160 for moving the third cooling fluid C3 therethrough. A filter 162 may be located upstream from the at least one heat removal device 120 positioned to directly cool a corresponding main heat-generating device 64. Downstream from the one or more heat removal devices 120 is a cooling heat exchanger 164 configured to remove heat from the third cooling fluid C3. The circuit may additionally include a reservoir or accumulator 166 within which excess third cooling fluid C3 is stored. As shown, the circuit may include a plurality of valves, such as arranged directly upstream from the heat removal device (VC1), directly downstream from a heat exchanger (VC2), associated with a bypass conduit 170 for bypassing the cooling heat exchanger (VC3), and associated with another bypass conduit 172 for bypassing both the heat removal device and the cooling heat exchanger (VC4).

[0064] It can be appreciated that in some embodiments, the cooling system 100 may include a plurality of heat removal devices 120, each positioned to directly cool one or more respective heat-generating electronic devices 50, such as a plurality of respective main heatgenerating devices for example. In such embodiments, the third cooling fluid C3 may flow to the plurality of heat removal devices 120 in any suitable manner. For example, each of the plurality of heat exchangers 120 may be fluidly connected in parallel relative to a flow of the s third cooling fluid C3 between the first fluid inlet 142 and the first fluid outlet 144. In another embodiment, the plurality of heat removal devices 120 may be fluidly connected in series relative to a flow of the third cooling fluid C3 between the first fluid inlet 142 and the first fluid outlet 144. In yet another embodiment, the plurality of heat removal devices 120 may be fluidly connected in both parallel and series relative to a flow of the third cooling fluid C3 between the first fluid inlet 142 and the first fluid outlet 144.

[0065] With reference now to FIG. 9, the at least one heat removal device 120 may alternatively or additionally include a secondary heat exchanger 180 mounted to the chassis 32 and/or the printed circuit board 34 and located remotely from both the main and peripheral heat-generating electronic devices 62, 64. In the illustrated, non-limiting embodiments, the secondary heat exchanger 180 is located, upstream from the at least one heat removal device 120 mounted in overlapping arrangement with at least one selected heat-generating electronic device 50 relative to a flow of the third cooling fluid C3, and in some embodiments relative to a flow of the second cooling fluid C2. For example, the secondary heat exchanger 180 may be mounted near a first end 54 of the printed circuit board 34, at a location between the at least one selected heat-generating electronic device 50 and the at least one fan 52. However, embodiments where the secondary heat exchanger 180 is arranged at another location are also contemplated herein.

[0066] The secondary heat exchanger 180 may be any suitable type of heat exchanger. In an embodiment, the secondary heat exchanger 180 is a microchannel heat exchanger having a plurality of substantially parallel microchannel heat exchanger tubes, each defining a plurality of fluid flow paths (not shown). However, examples of other types of heat exchangers that may be used, include, but are not limited to, microtube, double pipe, shell and tube, tube and fin, plate, plate and shell, adiabatic shell, plate fin, pillow plate, and fluid heat exchangers.

[0067] In the illustrated, non-limiting embodiments, the secondary heat exchanger 180 has an inlet 182 and an outlet 184 defining a flow path for the third cooling fluid C3 and another inlet 186 and another outlet 188 defining a flow path for the second cooling fluid C2. The third cooling fluid C3 and the second cooling fluid C2 may each make a single pass through the secondary heat exchanger 180. However, in other embodiments, at least one of the second cooling fluid C2 and the third cooling fluid C3 may make multiple passes through the secondary heat exchanger 180. Further, the second fluid C2 and the third cooling fluid C3 may be arranged in any suitable flow configuration at the heat exchanger, such as a cross-flow, a parallel flow, a counter-flow, or any combination thereof.

[0068] In an embodiment, the secondary heat exchanger 180 is configured as a cooling coil and the third cooling fluid C3 provided to secondary heat exchanger 180 is configured to absorb heat from the second cooling fluid C2. During operation, the at least one fan 52 provides a flow of the second cooling fluid C2, such as ambient air for example, to the secondary heat exchanger 180. Within the secondary heat exchanger 180, the cool or cold third cooling fluid C3 absorbs heat from the second cooling fluid C2. The third cooling fluid C3 at both the inlet 182 and the outlet 184 may be a single phase, such as a liquid for example, such that the third cooling fluid C3 provided to a downstream heat removal device 120, such as a heat exchanger, is a single phase and is at a temperature capable of absorbing heat from one or more selected heat-generating electronic devices 50. It should be appreciated that the second cooling fluid C2output from the outlet 188 of the secondary heat exchanger 180 may have passed over and therefore absorbed heat from one or more peripheral heat-generating electronic devices 62 prior to reaching a heat removal device 120.

[0069] In embodiments of the cooling system 100 that include a secondary heat exchanger 180 mounted upstream from the plurality of heat-generating electronic devices 50, cooling of the second cooling fluid C2need not be performed at the downstream heat removal devices 120. Accordingly, any heat removal devices 120 mounted in overlapping arrangement with a heat-generating electronic device 50 need not be heat exchangers. In such embodiments, the cooling of the selected heat-generating electronic devices 50 may be performed primarily by the flow of the third cooling fluid C3 through the heat removal device 120.

[0070] In embodiments where at least a portion of the first cooling fluid Cl is configured to vaporize upon contact with the peripheral heat-generating electronic device 62, one or more heat removal devices 120 as described herein may be operable as one or more secondary components used to condense a vapor first cooling fluid Cl as described above. For example, a heat exchanger 120, such as mounted to a main heat-generating electronic device 64 and/or the secondary heat exchanger 180 may be used to condense the vapor first cooling fluid Cl. [0071] With reference to FIG. 10, in embodiments where a portion of the first cooling fluid Cl vaporizes upon contact with a surface of a peripheral heat-generating device 62, the vapor first cooling fluid C 1 may become entrained with the flow of second cooling fluid C2 circulating through the server 30 via the fluid movement device 52. Accordingly, as the mixture of the vapor portion of the first cooling fluid Cl and the second cooling fluid C2 passes over or through a heat removal device, such as heat exchanger 120 or secondary heat exchanger 180 for example, the vapor first cooling fluid Cl is cooled, and therefore condenses on a surface of the fins and/or heat exchange tubes of the heat exchanger 120 or secondary heat exchanger 180. Accordingly, the second cooling fluid C2 provided at an outlet of the heat removal device has a reduced amount of first cooling fluid Cl entrained therein, and in some embodiments has substantially no first cooling fluid Cl mixed therewith. As noted above, the condensed first cooling fluid Cl at the heat exchanger 120 and/or secondary heat exchanger 180 may be collected and returned to a reservoir 104 for reuse within the cooling system 100.

[0072] A cooling system 100 as illustrated and described herein provides an easily scalable solution for cooling heat-generating components. Such a cooling solution can improve the sustainability and efficiency of the heat-generating components by rejecting the heat absorbed from the heat-generating component to a downstream heating application. In addition, the air conditioning load for cooling an area containing a data center is reduced. The cooling system 100 may have a reduced cost compared to existing single phase liquid cooling systems.

[0073] The term “about” is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.

[0074] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.

[0075] While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.

Claims

What is claimed is:

1. A cooling system for cooling an assembly including at least one heat-generating electronic device mounted to a printed circuit board, the cooling system comprising: a source of a first cooling fluid; and a spray nozzle fluidly coupled to the source of the first cooling fluid, wherein an outlet of the spray nozzle is oriented to spray the first cooling fluid onto a surface of the at least one heat-generating electronic device.

2. The cooling system of claim 1, wherein the at least one heat- generating electronic device is a peripheral heat-generating device.

3. The cooling system of claim lor claim 2, wherein the source of the first cooling fluid is fluidly coupled to the printed circuit board.

4. The cooling system of claim 3, wherein the source of the first cooling fluid is a reservoir positioned underneath the printed circuit board.

5. The cooling system of any of the preceding claims, further including: at least one fluid movement device for moving a vapor portion of the first cooling fluid relative to the assembly; and a secondary component located downstream from the at least one heatgenerating electronic device relative to a flow of the vapor portion of the first cooling fluid.

6. The cooling system of claim 5, wherein the secondary component is a heat exchanger, the flow of the vapor portion of the first cooling fluid being arranged in a heat transfer relationship at the secondary component.

7. The cooling system of claim 6, wherein the at least one heat-generating electronic device includes a plurality of heat-generating electronic devices and the heat exchanger is located upstream from the plurality of heat-generating electronic devices.

8. The cooling system of claim 6, wherein the at least one heat-generating electronic device includes a plurality of heat-generating electronic devices and the heat exchanger is located downstream from the plurality of heat-generating electronic devices.

9. The cooling system of claim 6, wherein the at least one heat-generating electronic device includes a plurality of heat- generating electronic devices, the spray nozzle being associated with one of the plurality of heat-generating electronic devices and the heat exchanger being associated with another of the plurality of heat-generating electronic devices.

10. The cooling system of claim 9, wherein the plurality of heat-generating electronic devices includes at least one main heat-generating electronic device and at least one peripheral heat-generating electronic device, the spray nozzle being associated with the at least one peripheral heat-generating electronic device and the heat exchanger being associated with the at least one main heat-generating electronic device.

11. A method of cooling an assembly including at least one heat-generating electronic device, the method comprising: spraying a first cooling fluid via a spray nozzle onto a surface of at least one heatgenerating electronic device to cool the at least one heat-generating electronic device; and collecting a liquid portion of the first cooling fluid within a reservoir, the reservoir being fluidly coupled to the spray nozzle.

12. The method of claim 11, further comprising moving a vapor portion of the first cooling fluid within the assembly via a fluid movement device.

13. The method of claim 12, wherein moving a vapor portion of the first cooling fluid further comprises entraining the vapor portion of the first cooling fluid within a second cooling fluid.

14. The method of claim 13, further comprising condensing the vapor portion of the first cooling fluid into a condensed first cooling fluid at a secondary component.

15. The method of claim 13, wherein the secondary component is a heat exchanger and condensing the vapor portion of the first cooling fluid further comprises arranging the second cooling fluid and the vapor portion of the first cooling fluid in a heat transfer relationship with a third cooling fluid at the heat exchanger.

16. The method of claim 15, wherein the at least one heat-generating electronic device includes a plurality of heat-generating electronic devices and the heat exchanger is located upstream from the plurality of heat-generating electronic devices.

17. The method of claim 15, wherein the at least one heat-generating electronic device includes a plurality of heat-generating electronic devices and the heat exchanger is located downstream from the plurality of heat-generating electronic devices.

18. The method of claim 15, wherein the at least one heat-generating electronic device includes a plurality of heat-generating electronic devices, the spray nozzle being associated with one of the plurality of heat-generating electronic devices and the heat exchanger being associated with another of the plurality of heat-generating electronic devices.

19. The method of claim 18, wherein the plurality of heat-generating electronic devices includes at least one main heat-generating electronic device and at least one peripheral heatgenerating electronic device, the spray nozzle being associated with the at least one peripheral heat-generating electronic device and the heat exchanger being associated with the at least one main heat-generating electronic device.

20. The method of claim any of the preceding claims, further comprising collecting the condensed first cooling fluid at the secondary component.