Manifold system, apparatus and method for thermal management of hardware components

Abstract

Relates to systems, devices, and methods for providing cooling to hardware components, and more particularly, to manifold systems, devices, and methods for thermal management of hardware within computer server racks and associated equipment within a computer data center.

Description

Cross - reference to related applications

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 344,291, filed May 20, 2022, which is hereby incorporated by reference in its entirety.

Technical Field

[0002] The present invention relates to systems, devices, and methods for providing cooling to hardware components, and more particularly, to manifold systems, devices, and methods for thermal management of thermosiphon hardware within computer server racks and associated equipment within a computer data center.

Background Art

[0003] Due to the rapid shift towards digitization across virtually all industries, there is an urgent need to develop next - generation information and communication technologies (ICT) to cope with the ever - increasing transmission, integration, storage, and processing of data. Due to the higher power consumption of new - generation hardware components such as CPUs and GPUs, conventional air - cooled thermal management solutions are widely expected to face significant challenges. Specifically, air - cooling technology is likely to reach the physical limits of power consumption in common hardware form factors, and the resulting decrease in their energy efficiency is an increasing concern for operators.

[0004] Most data centers and communication facilities are designed and still operate using air - cooling technology, and their energy consumption for cooling hardware equipment is, on average, about 40% of the total energy consumption.

[0005] As the awareness of social responsibility to address climate change increases, there is a global consensus on actions to improve energy efficiency and reduce carbon emissions across all industries. Therefore, the development of new high-efficiency cooling technologies that meet these requirements and can be widely adopted is extremely important. Two-phase cooling technology, for example, provides excellent key evaluation criteria such as heat density, efficiency, and reliability, and represents a viable long-term solution for the hardware high-density and thermal performance required by next-generation telecommunications and computing platforms. The present invention details a flow distribution architecture for ensuring the optimal operation of two-phase cooling technology, which overcomes flow instability and flow imbalance and maximizes IT hardware availability.

[0006] FIG. 1 shows a schematic diagram of a basic prior art of a two-phase cooling system comprising main components: an evaporator, a two-phase flow conduit (riser), a condenser, and a single-phase flow conduit (downcomer). The heat removed from the heat source is represented by the arrow labeled H1, and the heat dissipated to the secondary coolant is represented by the arrow labeled G1. Such a cooling system can drive the flow circulation by being actively pumped or by utilizing passive mechanisms such as gravity / buoyancy and / or capillary action.

[0007] In a passive implementation that utilizes gravity, the liquid refrigerant enters the evaporator, boils, and removes heat from the electronic device. The resulting two-phase mixture is induced upward by the riser to the condenser by the generation of buoyancy determined by the relative difference in fluid density in the downcomer and riser. Here, the two-phase mixture is returned, or mostly returned, to air, a single-phase liquid, or the liquid in the two-phase liquid-cooled condenser, and dissipates heat to the facility side. The liquid refrigerant is then induced downward by gravity towards the evaporator to start the loop again.

[0008] In the case of this system, the driving force is proportional to the overall height of the system and proportional to the density difference between the liquid refrigerant in the downcomer and the two-phase mixture in the riser. To have a passive flow circulation, the driving force (also called the gravity pressure gain) needs to be higher than the total pressure drop in the loop (considering the evaporator, riser, and condenser).

[0009] For proper operation, such a system must be designed so that the evaporator is located below the condenser and thus must be implemented vertically. For an active two-phase cooling system where the driving force is provided by a pump static head instead of being represented by the gravity pressure gain, the same components can be used. In this implementation form, the cooling system can be implemented in both horizontal and vertical orientations.

[0010] Figure 2 shows the prior art concept of two-phase cooling technology for next-generation server racks. The schematic diagram of Figure 2 assumes that the servers are vertically oriented inside the rack.

[0011] See Non-Patent Document 1, Non-Patent Document 2, and Non-Patent Document 3.

[0012] Patent Document 1 by Chu et al., which is incorporated by reference, discloses a thermosyphon cooling system having an overhead air-cooled condenser attached to a heat-generating component and a vertical evaporator. Each evaporator is adapted to a dedicated air-cooled condenser. Sizing of the liquid line and vapor line, as well as the taper design of the flow distribution header inside the evaporator structure, are described.

[0013] Patent Document 2 by Khrustalev et al., which is incorporated by reference, discloses a loop-type thermosyphon cooling system for electronic devices where a single condenser is connected to multiple evaporators. Throughout the system, multiple condensers are deployed, each being fluidly coupled to multiple evaporators at substantially the same height. A wick structure is implemented in the evaporator section to utilize capillary force.

[0014] Lamaison et al. disclosed a cascaded thermosyphon cooling loop in which a plurality of rack scale risers and downcomers are fluidly coupled to a single overhead rack scale condenser and thermally coupled to a plurality of evaporators located inside a vertical server form factor vertically distributed within a rack architecture. See Non-Patent Document 4.

[0015] Patent Document 3 by Farschchian et al., which is incorporated by reference, discloses a passive two-phase implementation for cooling a data center. This can be seen as a variation of the technique using a common rack level thermosyphon having two thermal bus lines (riser and downcomer) for connection to a single overhead air or liquid cooled condenser for horizontally arranged heat generating components.

[0016] Patent Document 3 by Farschchian et al. also discloses an implementation form in which heat generating components are vertically oriented and mechanically connected to a plurality of risers supplied from a common downcomer supplied from a common condenser. It also discloses the use of a fluid shut-off device between a fluid header and an evaporator assembly incorporating an orifice for measuring the flow to the evaporator. This orifice is described as being fixed or adjustable based on the dynamically changing amount of heat dissipated from one or more heat generating components.

[0017] Patent Document 4 by Samadiani et al., which is incorporated by reference, proposes a two-phase system for server level cooling. The cooling system is a low height thermosyphon having a liquid cooled condenser arranged at the back of the server. This invention describes the active control of a mechanical actuator for adjusting the liquid level in the evaporator as a function of the power loss of the hardware components.

[0018] Lamaison et al. introduced a new compact thermosyphon design for 2-U servers. The evaporator is used to cool two heat-generating components such as a CPU or GPU, and there is a common condenser located towards the rear of the rack that is cooled by cold water.

[0019] See Non-Patent Document 5.

[0020] Lamaison et al.'s system is stated to be compatible with hot-swappable servers, although no mechanism is presented. In the primary downcomer (the outlet of the condenser), the authors incorporated a liquid accumulator to optimize the thermosyphon thermal-hydraulic performance over a wide range of heat loads and heat rejection temperatures. The entire design including the evaporator, condenser, riser, and downcomer is made of copper. The evaporator and condenser can be designed with microscale structures, such as microchannels, to improve the condensation and boiling heat transfer characteristics.

[0021] Nadjahi et al. presented experimental results regarding a thermosyphon cooling rack equipped with blade (vertical) servers. Air from the white space (indoor test chamber) is drawn into the rack using fans to cool the blade server components, and a portion of the heat is removed from the air flow by two standard evaporator coils that connect to a remote condenser located outside the white space. The servers were simulated by dummy heat sources. From a thermal perspective, Nadjahi et al.'s implementation is similar to a typical rear-door cooling implementation that is horizontally deployed above / below the server array within the rack, instead of an air-cooled heat exchanger located at the rear of the rack. Thus, the thermal performance is limited.

[0022] See Non-Patent Document 6.

[0023] Gao's Patent Document 5, which is incorporated by reference, mainly describes technologies for cooling high-power data centers, focusing on multifunctional heat exchangers. Those servers can incorporate air cooling, liquid cooling, or hybrid cooling by means of a manifold located at the rack level. The liquid flowing within the manifold does not come into direct contact with the secondary coolant. This patent introduces the concept of a multifunctional heat exchanger incorporating a fan for cooling the hot air coming from the servers, and an indoor-level pump system is required for this implementation form. The core of this invention is the design of a multifunctional heat exchanger that can simultaneously manage liquid cooling and air cooling from high-power racks.

[0024] Both Patent Document 6 by Shedd et al. and Patent Document 7 by Shedd et al., which are incorporated by reference, present extensive inventions that disclose a pumped two-phase cooling system for server and other hardware layouts, including quick couplings and flexible tubes for hot-swap compatibility. Regarding rack cooling, a common manifold at the room level distributes the coolant from a central pump station to the rows of racks. Guidelines for evaporator orifice design are provided, and Patent Document 7 by Shedd et al. discloses the design of an evaporator having redundant flow paths.

[0025] Patent Document 8 by Alvarado et al., which is incorporated by reference, discloses a low-momentum-loss manifold design for two-phase spray cooling of racks that employs an angled transition between a manifold header and a manifold port to minimize flow-direction change losses. The angled branch ports are monolithically defined within the manifold to introduce an angular offset of the ports from the hardware components to be cooled.

[0026] The prior art does not disclose ways to address many practical issues for implementing fluid distribution in passive / active two-phase cooling solutions. These issues include, at least: Effectively transporting heat from hardware components to a system-level heat exchanger. Achieve a high availability level for an ICT system by providing redundancy in the distribution path. Reduce the impact of imbalance of the working fluid due to the presence of static pressure fluctuations in a vertically deployed two-phase cooling system. A sensor for monitoring the soundness of a two-phase cooling system. Thermal control of loop operation.

Prior Art Documents

Patent Documents

[0027]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Non-Patent Documents

[0028]

Non-Patent Document 1

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0029] The main object of the present invention is to provide a system, apparatus, and method for providing cooling to hardware components, and more specifically, to provide a manifold system, apparatus, and method for thermal management of hardware related to a wide range of ICT industries.

[0030] A second object of the present invention is to provide a system, apparatus, and method for providing cooling to hardware components that effectively transports heat from the hardware components to a system-level heat exchanger.

[0031] A third object of the present invention is to provide a system, apparatus, and method for providing cooling to hardware components that can mitigate the effects of operating fluid imbalance.

[0032] A fourth object of the present invention is to provide a system, apparatus, and method for providing cooling to hardware components that can minimize frictional pressure drop within the system while avoiding flow imbalance.

[0033] A fifth object of the present invention is to provide a system, apparatus, and method for providing cooling to hardware components, sensing for example to monitor coolant loss, and controlling loop operations such as fluid distribution in those hardware components.

[0034] A sixth object of the present invention is to provide a system, apparatus, and method for providing cooling to hardware components to provide modular redundancy in the distribution path.

Means for Solving the Problems

[0035] A preferred embodiment of a fluid flow manifold system for cooling a plurality of pluggable subsystems selected from at least a server, a network line card, a server thread, a server blade, an optical pluggable module, and other hardware devices that require thermal management in the ICT (Information and Communication Technology) industry includes the following: An overhead condenser that exchanges heat outside the system at a flow line connection to an accumulator that manages the fluid within the rack; A manifold unit fluidly connected to the accumulator and the condenser, An riser tube flow conduit and a riser tube port that convey a two-phase fluid from the pluggable subsystem to the condenser, A downcomer flow conduit and a downcomer port that convey a single-phase fluid to the pluggable subsystem including the manifold unit; and An inclined branch joint connector, wherein the manifold system distributes the fluid flow resulting from a high-pressure source to a plurality of manifold units that supply a plurality of evaporators within a plurality of pluggable subsystems within the system, and the pluggable subsystems are cooled in parallel.

[0036] The high-pressure source can be formed from gravity or a pump.

[0037] The manifold unit is fluidly connected to the accumulator and the condenser via an inclined branch joint to balance the flow distribution by gravity on the downcomer side of the manifold system.

[0038] The manifold system further includes a minimum length between the condenser refrigerant inlet and the inclined branch joint on the riser tube side to reduce the pressure drop when the two-phase flow returns to the condenser.

[0039] The manifold system can further include: a redundant port having an isolation valve on an inclined branch joint connected to the downcomer and riser flow conduits within the manifold unit to facilitate replacement of the manifold unit during system operation.

[0040] The manifold system can further include: a flow line connection between two or more downcomer lines at the lowest height of the system to balance the liquid levels in the downcomers; and a server bypass flow line having a restricted flow CSA (cross-sectional area) between the downcomer and the riser at the lowest height of the system.

[0041] The manifold system can further include: a gradual change in the flow tube CSA (cross-sectional area) along the length of each manifold riser and downcomer.

[0042] The manifold system can further include: a material selectively removed between the riser manifold and the downcomer manifold to achieve controlled heat transfer between the riser manifold and the downcomer manifold while maintaining the structural integrity of the manifold system.

[0043] The manifold system can further include: a flow restrictor inserted into the downcomer flow conduit and the downcomer port of the manifold unit to manage the excess static pressure generated within the downcomer.

[0044] The manifold system can further include: a smooth flow transition incorporated into the manifold unit to induce passive fluid flow at the entrance to the downcomer port and minimize pressure drop at the entrance to the riser port while maintaining alignment of the riser and downcomer ports for the pluggable subsystem.

[0045] The manifold system can further include: offset riser and downcomer flow conduits for optimizing the space occupied by the manifold unit with ports of substantially different sizes, further managing the space, and minimizing pressure drop.

[0046] Another embodiment of the manifold system for cooling a plurality of pluggable subsystems within the system can include: modular manifold unit components that provide flexibility for defining different flow geometry parameters based on the designed distribution of heat sources and the overall size of the system to be cooled.

[0047] The manifold system can further include: a bypass downcomer flow conduit to assist in the effective distribution of the coolant.

[0048] The manifold system can further include: a coolant sensor module installed at selected locations on the manifold system to detect leaks and provide continuous real-time anomaly detection.

[0049] The coolant sensor module can be selected from at least one of the following: an infrared-based sensor, an electrochemistry-based sensor, a MEMS (Micro-Electro-Mechanical System)-based sensor, and a photodiode-based sensor.

[0050] The manifold system can further include: temperature probes strategically placed around the system for overall leak detection of the coolant based on abnormal temperature fluctuations, selected from at least one of the following: thermocouples, thermistors, RTDs (Resistance Temperature Devices), and diodes, and strategically placed around the system at locations at risk of mechanical failure and thus the most likely refrigerant leak locations.

[0051] The manifold system can further include: a resistive heating element on the manifold riser pipe for providing an accurate amount of heat to the cooling loop during startup control and during system operation.

[0052] The resistive heating element can provide local or distributed heat input to the cooling loop.

[0053] The manifold system can further include: an insulating layer on the outer surface of the manifold unit.

[0054] Embodiments of a fluid flow manifold system for cooling a plurality of pluggable subsystems that require thermal management of servers within a computer center can include: An overhead condenser that exchanges heat external to the system at a flow line connection to an accumulator that manages fluid within the rack; A manifold unit fluidly connected to the accumulator and the condenser, An upflow conduit and an upflow port that convey a two-phase fluid from the pluggable subsystem to the condenser, A downflow conduit and a downflow port that convey a single-phase fluid to the pluggable subsystem including the manifold unit; and An inclined branch junction connector, wherein the manifold system distributes fluid flow resulting from a high-pressure source to a plurality of manifold units that supply a plurality of evaporators within a plurality of pluggable subsystems within the system, and the pluggable subsystems are cooled in parallel.

[0055] Further objects and advantages of the present invention will become apparent from the following detailed description of the presently preferred embodiments, which are schematically shown in the accompanying drawings.

[0056] The drawings show, by way of example and not limitation, one or more implementations in accordance with the concepts. In the drawings, like reference numerals refer to the same or similar elements.

Brief Description of the Drawings

[0057]

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Figure 8B

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Figure 9B

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Figure 13

[0058] Before detailing the disclosed embodiments of the present invention, it should be understood that since the present invention is capable of other embodiments, it is not limited to the details of the specific configurations shown in its application. Also, the terms used in this specification are for the purpose of explanation and not for limitation.

[0059] In the above summary and detailed description of the preferred embodiments and the accompanying drawings, specific features of the present invention (including method steps) are referred to. It should be understood that the disclosure of the present invention herein does not include all possible combinations of such specific features. For example, when a specific feature is disclosed in the context of a particular aspect or embodiment of the present invention, that feature may also be used, to the extent possible, in combination with, and / or in the context of, other particular aspects and embodiments of the present invention and in the context of the present invention as a whole.

[0060] In this section, some embodiments of the present invention are described in more detail with reference to the accompanying drawings in which the preferred embodiments of the present invention are shown. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will convey the scope of the present invention to those skilled in the art. Like numbers refer to like elements throughout, and prime notation is used to indicate like elements in alternative embodiments.

[0061] Other technical advantages will become readily apparent to those skilled in the art after considering the following drawings and description.

[0062] Exemplary embodiments are shown in the drawings and described below, but it should first be understood that the principles of the present disclosure may be implemented using any number of techniques, whether currently known or not. The present disclosure should in no way be limited to the exemplary implementations and techniques shown in the drawings and described below.

[0063] Unless otherwise specified, the articles shown in the drawings are not necessarily drawn to scale.

[0064] Refer to the following list of abbreviations and their definitions. CPU Central Processing Unit CRAC Computer Room Air Conditioner CSA Cross - Sectional Area GPU Graphics Processing Unit ICT Information and Communication Technology PDU Power Distribution Unit PDCU Power Distribution and Collection Unit TSL Thermosyphon Loop CSA Cross - Sectional Area MEMS Micro - Electro - Mechanical System RTD Resistance Temperature Device.

[0065] The IT envelope refers to any volume that encloses an electronic or optoelectronic device.

[0066] The disclosure of the present invention summarizes a list of features of an invention that enables the commercialization of an effective manifold for active and passive two - phase cooling systems.

[0067] FIG. 3 shows a schematic diagram of an exemplary two-phase system 300 implementation for cooling heat-generating components. The system is configured to distribute coolant to a plurality of manifold units 307, which is advantageous for a particular ICT architecture composed of pluggable subsystems 311 such as servers, power distribution, blades, threads, etc., that do not span the entire width of a rack or chassis and are required to be easily usable. Each manifold unit 307 is composed of one or more downcomer flow paths and one or more riser flow paths to enhance flow distribution, as shown below, and can be placed above or around a hardware component, such as the mechanical housing of a server rack.

[0068] The number of manifold units, risers, and downcomers, collectively, can be optimized based on the number of pluggable subsystems being cooled in parallel within a rack, chassis, cabinet, and any other mechanical housing used in the ICT industry, including servers, network line cards, threads, blades, optical pluggable modules, and any other hardware devices used in the ICT industry. Further, the system is redundantly configured such that the manifold units 307 can be replaced during system operation, thus facilitating high availability of ICT components. The features described herein mitigate issues related to maintaining system availability and balancing flow distribution for effective hardware cooling.

[0069] The working fluid in such a system can be an ASHRAE-certified refrigerant or other suitable coolant having properties suitable for two-phase heat transfer. The system-level heat exchanger unit 301 is cooled by the supplied fluid 302 and returned to the facility at a higher enthalpy (303). The condensed working fluid, i.e., the liquid, flows out of the heat exchanger from the downcomer port 304 and into the reservoir 305, i.e., the liquid accumulator. The liquid accumulator can manage the system fluid inventory under dynamic power conditions and can be placed on the downcomer line below the condenser or as an extension of the condenser outlet header. The accumulator manages the fluid inventory in the rack to ensure the presence of liquid in the downcomer of the manifold, maintain the design static head for loop operation, and avoid condenser flooding at high heat loads.

[0070] The liquid exits the liquid accumulator and enters a downcomer branch junction 306 that can be arranged vertically, horizontally, or at an intermediate angle. The outlet ports of the branch junction, e.g., a Y-shaped tee, are configured such that the inlet flow and the outlet flow are substantially parallel and balance the flow distribution under the action of gravity. The branch junction can have two or more outlet ports depending on the number of vertical manifold units 307 connected within the system. At the end of each outlet port on the branch junction, there is an isolation valve 308, e.g., a self-sealing quick coupler half. Another isolation valve 309, e.g., the self-sealing quick coupler mate of 308, is attached to a manifold unit downcomer whip 310 that conveys the liquid to the downcomer of the manifold unit 307, which can be rigid, semi-rigid, or flexible.

[0071] The liquid cooling flow is distributed from the manifold unit 307 to a number of vertically distributed pluggable subsystems 311 that can include, for example, 19” or 23” servers, network line cards, server rails, server blades, optical pluggable modules, or any other hardware device requiring thermal management used in the ICT (Information and Communication Technology) industry.

[0072] The two-phase cooling loop 314 may be composed of flexible, semi-flexible, or rigid tubes, or a combination of flexible, semi-flexible, and rigid tubes, and is connected to one or more heat exchangers, i.e., evaporators, and may be directly attached on or inside the pluggable subsystem 311 to facilitate heat removal. It is connected to the manifold unit 307 via one or more pairs of appropriately sized isolation valves, e.g., self-sealing quick couplings sized according to the designed coolant mass flow rate, when the flow is single-phase or two-phase, and facilitates the removal of the pluggable subsystem 313 for use or due to a failure of the pluggable subsystem cooling loop while the entire system is operating.

[0073] Provide supplementary air cooling to cool low-power hardware components at the pluggable subsystem level not addressed by the two-phase cooling loop, and this heat can be discharged directly to an additional air-cooled heat exchanger or to the facility housing the system.

[0074] The single-phase or two-phase flow from the pluggable subsystem to the manifold unit 307 flows into the riser of the manifold unit 307. The manifold unit riser whip 315, which can be rigid, semi-rigid, or flexible, conveys the two-phase flow to the inlet of the riser branch junction 316, which has a similar design but not necessarily the same size as the downcomer branch junction 306, via an isolation valve, e.g., a self-sealing quick coupling pair.

[0075] The riser branch joint 316 is arranged as close as practically possible to a condenser inlet port 317 whose size and shape are configured to minimize the pressure loss of the converging two-phase flow coming from one or more manifold units 307. The downcomer branch joint and the riser branch joint can be provided with at least one additional redundant port having an isolation valve 318 with respect to the designed number of the deployed manifold units 307. This feature facilitates, for example, adding additional manifold units to the system, or upgrading the capacity or replacing a manifold unit in response to the failure of an operating manifold unit.

[0076] The operation of the two-phase cooling system is further improved by a feature that fluidly connects two or more manifold units at the height of the bottom of the manifold units. This can be achieved, for example, by connecting a pipe 319 at the bottom of the manifold unit downcomer to the downcomer of another manifold unit via an isolation valve 320, such as a self-sealing quick coupling.

[0077] In the case of an implementation form of a system including two or more manifold units, a plurality of isolation valve bodies can be provided on a multi-directional tee.

[0078] This configuration has several advantages. It reduces the unbalanced distribution of the working fluid to the downcomer by driving a rebalancing flow using the liquid head difference between the downcomer branches. This situation can occur, for example, during system shutdown followed by startup or system charging, or due to the removal of one or more pluggable subsystems, or due to the time-varying operating heat load supplied from the heating element to the cooling system.

[0079] Furthermore, this feature added to the redundant ports on the riser / downcomer branch joint helps to manage the fluid inventory split between the manifold units, enabling the replacement of a manifold unit while the overall system is operating, either during an upgrade of the manifold unit or due to a failure of the manifold unit.

[0080] Furthermore, the manifold unit, accumulator, capacitor, and branch joint can be provided with access ports 321 to allow for evacuation, charging, conducting pressure tests, and general access to different parts of the overall system during operation or for use. Variations of the manifold unit can include the position of the manifold unit above and around the server / rack chassis.

[0081] Design and implementation of the manifold unit and support system components Here, an explanation is provided of the manifold unit features that can be implemented to facilitate good flow distribution in a two-phase flow system under the action of gravity, and additional system features that provide sensing and thermal control of the overall two-phase cooling system. The general design approach is represented in FIG. 4, which shows that the characteristic flow dimensions of the manifold unit gradually decrease as the distance from the capacitor increases in the presence of the gravitational field represented by vector 401. The theoretical requirements for such a design result from the presence of a static pressure gradient occurring along the manifold unit in the presence of gravity, due to the liquid flow on the downcomer and the lower density two-phase flow on the riser that must be managed to properly distribute the flow to the pluggable subsystem 311. Embodiments are described in the following drawings / drawing captions.

[0082] Figure 5 shows a schematic cross-sectional view of an exemplary manifold unit 500 having a downcomer liquid flow 501 and a riser flow 502, where the characteristic flow dimensions within the manifold unit decrease with decreasing height to manage the change in static pressure of the liquid column in the downcomer and the decrease in flow rate in the riser. The size of the downcomer is smaller compared to the riser because the friction pressure drop gradients between single-phase and two-phase flows are different. The continuous or stepwise change in flow dimension 503 at two, three, four or more steps along the length of the downcomer flow conduit of the manifold unit optimizes the trade-off between the momentum and friction of the flow to improve the distribution of the flow to vertically distributed ports (not shown). The continuous or stepwise change in flow dimension 504 at two, three, four or more steps along the length of the riser flow conduit of the manifold unit optimizes the flow velocity. The size of the riser is maximized to minimize the pressure drop, but is limited considering the need to keep the two-phase flow velocity appropriately high to avoid phase separation of the liquid and vapor in the gravitational field 505.

[0083] The adiabatic air gap feature 506 located between the riser and the downcomer near the upper part of the manifold unit manages the sensible heat and the change in subcooling of the downcomer liquid flow related to the static pressure of the liquid column in the downcomer.

[0084] Figure 6 shows a schematic cross-sectional view of a manifold unit 600 having a flow configured with respect to gravity as in Figure 5, showing a progressive decrease in the size of the downcomer port 601 that manages the flow distribution due to the increase in the static head of the liquid in the downcomer. The size of the riser port is kept substantially the same to minimize the larger pressure drop associated with two-phase flow.

[0085] Figure 7 shows a schematic cross-sectional view of a manifold unit 700 having a flow configured with respect to gravity as in Figure 5, showing a restriction 701 disposed within the downcomer flow conduit of the manifold unit that manages the flow distribution due to the increase in the static head of the liquid in the downcomer. These restrictions can be, for example, simple orifices, venturis or pressure differential operated flow limiters.

[0086] FIG. 8A shows a schematic cross-sectional view of a manifold unit 800 having a flow configured with respect to gravity as in FIG. 5, a primary downcomer 801 (the riser is not shown), a bypass downcomer 802, and a fluid connection between the primary downcomer and the bypass downcomer along manifold unit 803 and at the bottom of manifold unit 804 to allow flow from the bypass downcomer to the primary downcomer and to facilitate improved flow distribution to downcomer port 808. The liquid coolant may have the same or substantially different cross-sectional flow dimensions via a branch joint 805, such as a Y-shaped tee, configured such that the inlet flow and the outlet flow are substantially parallel to maintain a balance of flow distribution under the action of gravity.

[0087] The downcomer port inlet 806 can be rounded or structured in a manner that reduces rotational losses as the flow moves into a port configured perpendicular to the manifold unit downcomer flow, and facilitates alignment between the manifold unit 307 and the pluggable subsystem 311 when deployed within the two-phase cooling system 300. This feature can also be implemented in the ports of the riser of the manifold unit to reduce pressure loss. The additional restrictor 807 can be integrated into each port of the primary downcomer of the manifold unit having pressure drop characteristics suitable for managing flow distribution due to liquid static head variations along the downcomer, and can also be included in the primary downcomer flow conduit and the bypass downcomer flow conduit. These restrictors can be, for example, simple orifices, venturis or pressure differential actuated flow limiters.

[0088] FIG. 8B shows a schematic cross-sectional view of the manifold of FIG. 8A, showing possible arrangements of the riser 809, the primary downcomer 801, and the bypass downcomer 802 with respect to the downcomer port and the riser port that respectively distribute flow to and from the pluggable subsystem 311.

[0089] Figure 9A shows the configuration 900 of a cooling system manifold unit 901 (shown as sectional schematic view B-B' in Figure 9B), showing the riser pipe 902 and downcomer pipe 903 arranged in an offset manner that minimizes the width of the manifold unit when attached to the rail 904, and facilitating the placement of additional coolant or power distribution components or cable management 905 while still facilitating the flow from 906 and 907 to the pluggable subsystem 908 via the downcomer pipe 909 and the riser pipe port 910.

[0090] Figure 9B shows a sectional schematic view of the manifold unit 901 (view A-A' of Figure 9A), showing the vertically offset riser pipe 910 and downcomer pipe 909 ports of unequal size to facilitate the compact width of the manifold unit 901 for the exemplary deployment shown in 900.

[0091] Modular manifold As shown in the sectional schematic view in Figure 10, the mounting form of the manifold unit can be further optimized by adopting a modular design 1000. This provides the flexibility to mix and fit two or more manifold unit sections, for example, three manifold unit sections 1001, 1002, 1003 having different riser pipes 1004 and downcomer pipes 1005, based on the design distribution of the heat source and the total size of the system to be cooled.

[0092] The modular manifold can implement a compact mechanical joint between sections that can be fixed with a clamp placed on 1006 or recessed into 1007. The manifold unit sections are aligned with guide pins and / or mechanical fasteners 1008 incorporated into the clamp plate to hold the manifold unit sections together and are reinforced with high-strength pins 1009 across the joints. An O-ring seal or gasket seal or any suitable sealing method can be placed at the joints to fluidly isolate the riser pipe sections and downcomer pipe sections from each other and from the surrounding environment.

[0093] Refrigerant Leak Detection Minor refrigerant leaks over long time scales can be a significant burden for maintaining the system in an optimal state, while major leaks can lead to catastrophic accidents (i.e., as the liquid level in the system drops, the refrigerant dries out in the evaporator due to large temperature fluctuations of the hardware components over time). To detect minor vapor leaks, vapor sensor modules such as infrared-based, electrochemistry-based, MEMS-based, or photodiode-based sensors can be installed at strategic locations around the manifold for real-time continuous anomaly detection.

[0094] For overall leak detection, low-cost temperature probes (e.g., thermocouples, thermistors, RTDs, etc.) can be strategically placed around the system where there is a potential risk of mechanical failure and thus the highest likelihood of being a refrigerant leak point. In the case of an overall refrigerant leak, the rapid temperature drop due to the evaporative cooling effect of the latent heat during refrigerant evaporation can be used as an alternative means to quickly identify the accident and respond by safely turning off the IT equipment.

[0095] FIG. 11 shows a schematic diagram of a temperature sensor-based leak detection network arranged above and around a manifold unit using a probe 1101 located at potential leak points within the system, such as at the downcomer and riser ports 1102 and at the joints between manifold unit sections within the modular manifold unit arrangement 1103.

[0096] Manifold Starter / Control Heater A resistive heating element (localized or distributed) placed on the manifold unit riser can provide an accurate amount of heat to the two-phase loop during system operation and during the system startup procedure (FIG. 12).

[0097] The power supply to the heater is controlled by an external control unit using, for example, a solid-state relay that is packaged within the control unit and powered by AC or DC power delivered, for example, from a rack PDU. At startup, the heat input to the riser tube starts a stable recirculation of the two-phase refrigerant mixture within the thermosiphon loop while avoiding an uncontrolled heat source and an unstable flow pattern that is not controlled in the presence of, for example, a pluggable subsystem.

[0098] When the control system detects a robust two-phase flow and the server is operating, the heater automatically turns off, improving the energy efficiency of the system. A specific embodiment of the implementation form is shown in FIG. 12. This feature also enables loop maintenance by carefully controlling the loop flow rate to operate an optimal degassing cycle via an automatic air vent before the entire IT system enters operation.

[0099] FIG. 12 shows a schematic diagram of a specific implementation form of the present invention in which the control heater is attached to the bottom of the manifold riser tube below the height of the lowermost server working fluid connection.

[0100] FIG. 13 shows a schematic diagram of a specific implementation form of the present invention in which the control heater is attached to the bottom of the manifold riser tube below the height of the lowermost server working fluid connection. The use of a local air gap between the heated riser tube portion and the downcomer and insulation around the manifold can maximize the amount of heat transferred to the riser tube.

[0101] The term "about" / "approximately" can be + / - 10% of the referenced amount. Further, preferred amounts and ranges can include amounts and ranges referenced without the prefix "about".

[0102] Certain advantages are listed above, but various embodiments may include some, none, or all of the listed advantages.

[0103] Without departing from the scope of the present disclosure, modifications, additions, or omissions may be made to the systems, apparatuses, and methods described herein. For example, the components of the systems and apparatuses may be integrated or separated. Further, the operations of the systems and apparatuses disclosed herein may be performed by more, fewer, or other components, and the methods described may include more, fewer, or other steps. Further, the steps may be performed in any suitable order. As used herein, "each" refers to each member of a set or each member of a subset of a set.

[0104] To assist any reader of the patent office and any patent issued on this application in interpreting the claims appended hereto, Applicant notes that, unless the terms "means for" or "step for" are expressly used in a particular claim, neither the appended claims nor any elements of the appended claims are intended to be construed under 35 U.S.C. 112(f).

[0105] Although the invention has been described, disclosed, illustrated, and shown in various terms of certain embodiments or modifications which are actually contemplated, it is not intended, nor should it be construed, to be so limited thereby, and other modifications or embodiments as may be suggested by the teachings herein are particularly reserved especially if they are within the breadth and scope of the claims appended hereto.

Claims

1. A fluid flow manifold system for cooling multiple pluggable subsystems selected from at least servers, network line cards, server threads, server blades, optical pluggable modules, and other hardware equipment used in the ICT (Information and Communication Technology) industry that requires thermal management, An overhead capacitor that exchanges external heat from the aforementioned system at the flowline connection to the accumulator that manages the fluid within the rack; A manifold unit that is fluidly connected to the accumulator and the capacitor, A riser flow conduit and riser port for transporting a two-phase fluid from the pluggable subsystem to the condenser. Downstream flow conduit and downstream port for transporting single-phase fluid to the pluggable subsystem Manifold unit including; Inclined branch joint connector; Flow line connections between two or more descender pipe lines at the lowest height of the system to balance the liquid level of the descender pipe; and Server bypass flowline having a limited flow CSA (cross-sectional area) between the descending and ascending pipes at the lowest height of the system. Equipped with, The manifold system distributes the fluid flow originating from a high-pressure source to a plurality of manifold units that supply a plurality of evaporators in the plurality of pluggable subsystems within the system, the pluggable subsystems are cooled in parallel, and the high-pressure source is formed from gravity or a pump. A manifold system characterized by the following features.

2. The manifold system according to claim 1, characterized in that the manifold unit is fluidly connected to the accumulator and the condenser via the inclined branch joint to balance the flow distribution by gravity on the downpipe side of the manifold system.

3. The manifold system according to claim 2, further characterized in that it includes a minimum length between the condenser refrigerant inlet and the inclined branch joint on the riser pipe side to reduce the pressure drop when the two-phase flow returns to the condenser.

4. A redundant port having an isolation valve on an inclined branch joint connected to the downpipe and the uppipe flow conduit within the manifold unit, in order to facilitate the replacement of the manifold unit while the system is operating. The manifold system according to claim 2, further comprising:

5. Gradual change in flow tube CSA (cross-sectional area) along the length of each manifold riser and faller. The manifold system according to claim 4, further comprising:

6. A fluid flow manifold system for cooling a plurality of pluggable subsystems selected from at least servers, network line cards, server threads, server blades, optical pluggable modules, and other hardware equipment used in the ICT (Information and Communication Technology) industry that requires thermal management, An overhead capacitor that exchanges external heat from the aforementioned system at the flowline connection to the accumulator that manages the fluid within the rack; A manifold unit that is fluidly connected to the accumulator and the capacitor, A riser flow conduit and riser port for transporting a two-phase fluid from the pluggable subsystem to the condenser. Downstream flow conduit and downstream port for transporting single-phase fluid to the pluggable subsystem Manifold unit including; Inclined branch joint connector; and To achieve controlled heat transfer between the riser manifold and the descender manifold while maintaining the structural integrity of the manifold system, material is selectively removed between the riser manifold and the descender manifold. Equipped with, The manifold system distributes the fluid flow originating from a high-pressure source to a plurality of manifold units that supply a plurality of evaporators in the plurality of pluggable subsystems within the system, the pluggable subsystems are cooled in parallel, and the high-pressure source is formed from gravity or a pump. A manifold system characterized by the following features.

7. A fluid flow manifold system for cooling a plurality of pluggable subsystems selected from at least servers, network line cards, server threads, server blades, optical pluggable modules, and other hardware equipment used in the ICT (Information and Communication Technology) industry that requires thermal management, An overhead capacitor that exchanges external heat from the aforementioned system at the flowline connection to the accumulator that manages the fluid within the rack; A manifold unit that is fluidly connected to the accumulator and the capacitor, A riser flow conduit and riser port for transporting a two-phase fluid from the pluggable subsystem to the condenser. Downstream flow conduit and downstream port for transporting single-phase fluid to the pluggable subsystem Manifold unit including; Inclined branch joint connector; and Flow limiters inserted into the manifold unit's downpipe flow conduit and downpipe port to manage the excess static pressure generated in the downpipe. Equipped with, The manifold system distributes the fluid flow originating from a high-pressure source to a plurality of manifold units that supply a plurality of evaporators in the plurality of pluggable subsystems within the system, the pluggable subsystems are cooled in parallel, and the high-pressure source is formed from gravity or a pump. A manifold system characterized by the following features.

8. A fluid flow manifold system for cooling a plurality of pluggable subsystems selected from at least servers, network line cards, server threads, server blades, optical pluggable modules, and other hardware equipment used in the ICT (Information and Communication Technology) industry that requires thermal management, An overhead capacitor that exchanges external heat from the aforementioned system at the flowline connection to the accumulator that manages the fluid within the rack; A manifold unit that is fluidly connected to the accumulator and the capacitor, A riser flow conduit and riser port for transporting a two-phase fluid from the pluggable subsystem to the condenser. Downstream flow conduit and downstream port for transporting single-phase fluid to the pluggable subsystem Manifold unit including; Inclined branch joint connector; and A smooth flow transition section incorporated into the manifold unit to guide passive fluid flow at the inlet to the descending pipe port and minimize pressure drop at the inlet to the ascending pipe port, while maintaining the alignment of the ascending and descending pipe ports with respect to the pluggable subsystem. Equipped with, The manifold system distributes the fluid flow originating from a high-pressure source to a plurality of manifold units that supply a plurality of evaporators in the plurality of pluggable subsystems within the system, the pluggable subsystems are cooled in parallel, and the high-pressure source is formed from gravity or a pump. A manifold system characterized by the following features.

9. A fluid flow manifold system for cooling a plurality of pluggable subsystems selected from at least servers, network line cards, server threads, server blades, optical pluggable modules, and other hardware equipment used in the ICT (Information and Communication Technology) industry that requires thermal management, An overhead capacitor that exchanges external heat from the aforementioned system at the flowline connection to the accumulator that manages the fluid within the rack; A manifold unit that is fluidly connected to the accumulator and the capacitor, A riser flow conduit and riser port for transporting a two-phase fluid from the pluggable subsystem to the condenser. Downstream flow conduit and downstream port for transporting single-phase fluid to the pluggable subsystem Manifold unit including; Inclined branch joint connector; and Offset riser and fallr flow conduits to optimize the space occupied by the manifold unit with ports of substantially different sizes, further managing space and minimizing pressure drop. Equipped with, The manifold system distributes the fluid flow originating from a high-pressure source to a plurality of manifold units that supply a plurality of evaporators in the plurality of pluggable subsystems within the system, the pluggable subsystems are cooled in parallel, and the high-pressure source is formed from gravity or a pump. A manifold system characterized by the following features.

10. A fluid flow manifold system for cooling a plurality of pluggable subsystems selected from at least servers, network line cards, server threads, server blades, optical pluggable modules, and other hardware equipment used in the ICT (Information and Communication Technology) industry that requires thermal management, An overhead capacitor that exchanges external heat from the aforementioned system at the flowline connection to the accumulator that manages the fluid within the rack; A manifold unit that is fluidly connected to the accumulator and the capacitor, A riser flow conduit and riser port for transporting a two-phase fluid from the pluggable subsystem to the condenser. Downstream flow conduit and downstream port for transporting single-phase fluid to the pluggable subsystem Manifold unit including; Inclined branch joint connector; and Bypass descender flow conduit assists in the effective distribution of coolant. Equipped with, The manifold system distributes the fluid flow originating from a high-pressure source to a plurality of manifold units that supply a plurality of evaporators in the plurality of pluggable subsystems within the system, the pluggable subsystems are cooled in parallel, and the high-pressure source is formed from gravity or a pump. A manifold system characterized by the following features.

11. Coolant sensor module installed at a selected location on the manifold system to detect leaks and provide real-time continuous anomaly detection. The manifold system according to claim 1, further comprising:

12. The manifold system according to claim 11, characterized in that the coolant sensor module is selected from at least one of an infrared-based sensor, an electrochemical-based sensor, a MEMS (micro-electromechanical system)-based sensor, and a photodiode-based sensor.

13. A fluid flow manifold system for cooling a plurality of pluggable subsystems selected from at least servers, network line cards, server threads, server blades, optical pluggable modules, and other hardware equipment used in the ICT (Information and Communication Technology) industry that requires thermal management, An overhead capacitor that exchanges external heat from the aforementioned system at the flowline connection to the accumulator that manages the fluid within the rack; A manifold unit that is fluidly connected to the accumulator and the capacitor, A riser flow conduit and riser port for transporting a two-phase fluid from the pluggable subsystem to the condenser. Downstream flow conduit and downstream port for transporting single-phase fluid to the pluggable subsystem Manifold unit including; Inclined branch joint connector; and Temperature probes strategically placed around the system for detecting overall coolant leakage based on abnormal temperature fluctuations. Equipped with, The manifold system distributes the fluid flow originating from a high-pressure source to a plurality of manifold units that supply a plurality of evaporators in the plurality of pluggable subsystems within the system, the pluggable subsystems are cooled in parallel, and the high-pressure source is formed from gravity or a pump. The temperature probe is selected from at least one of a thermocouple, thermistor, RTD (resistance temperature device), and diode, and is strategically positioned around the system at locations where there is a risk of mechanical failure, and therefore at the most likely locations of refrigerant leakage. A manifold system characterized by the following features.

14. A fluid flow manifold system for cooling a plurality of pluggable subsystems selected from at least servers, network line cards, server threads, server blades, optical pluggable modules, and other hardware equipment used in the ICT (Information and Communication Technology) industry that requires thermal management, An overhead capacitor that exchanges external heat from the aforementioned system at the flowline connection to the accumulator that manages the fluid within the rack; A manifold unit that is fluidly connected to the accumulator and the capacitor, A riser flow conduit and riser port for transporting a two-phase fluid from the pluggable subsystem to the condenser. Downstream flow conduit and downstream port for transporting single-phase fluid to the pluggable subsystem Manifold unit including; Inclined branch joint connector; and Resistive heating element on the manifold riser to provide a precise amount of heat to the cooling loop during startup control and system operation. Equipped with, The manifold system distributes the fluid flow originating from a high-pressure source to a plurality of manifold units that supply a plurality of evaporators in the plurality of pluggable subsystems within the system, the pluggable subsystems are cooled in parallel, and the high-pressure source is formed from gravity or a pump. A manifold system characterized by the following features.

15. The manifold system according to claim 14, characterized in that the resistive heating element provides localized or dispersed heat input to the cooling loop.

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