A CDU-free computing power center liquid cooling heat dissipation system and a control method thereof

Abstract

The application discloses a CDU-removed computing power center liquid cooling heat dissipation system and a control method, and belongs to the technical field of liquid cooling heat dissipation. The system contains a concentric tube heat exchanger, a water distributor, a water collector and the like, and does not have an integrated CDU device, and only the heat exchange between the insulating cooling liquid on the computing power side and the industrial cooling water on the refrigeration side is completed through the concentric tube heat exchanger. The heat exchanger adopts a three-layer pipe structure, is provided with a turbulence protrusion and a positioning support, and the approach temperature difference can be controlled to be 1-3 DEG C. The system forms two fluid isolation independent closed loops, the cold source can realize three mode switching, the controller dynamically matches the flow according to the power consumption of the server, and one source two uses full-link cooling is realized. The system can reduce the cabinet-level pump power by 43%-88%, the total cooling energy consumption by 13%-36%, the CPU temperature by 5.4-11.5 DEG C, and is suitable for AI chips above 2000W level and high-density computing power center scenes.

Description

Technical Field

[0001] This invention belongs to the field of liquid cooling technology for computing centers, specifically relating to a CDU-free liquid cooling system for computing centers and its control method, which is particularly suitable for heat dissipation scenarios of AI chips, GPUs and high-density computing centers with a power consumption of 2000W or more. Background Technology

[0002] With the large-scale deployment of AI large-scale model training, intelligent computing clusters, and high-density GPU servers, the power consumption of a single rack typically reaches 20kW-50kW, and the power consumption of a single chip exceeds 2000W. The heat flux density far exceeds the limits of traditional air cooling, and liquid cooling has become the standardized heat dissipation solution for computing centers. Studies have shown that the power consumption of data center cooling systems is now comparable to that of IT equipment, accounting for as much as 43% of the total power consumption.

[0003] Current liquid cooling systems in computing centers generally adopt a five-stage heat dissipation architecture: "chip cold plate → secondary side coolant → CDU → primary side cooling water → dry cooler / cooling tower". The CDU is the core component of the liquid cooling system, typically an integrated unit consisting of a circulating pump, frequency converter, filter, plate heat exchanger, electrical control unit, monitoring and sensing unit, connecting pipes and valves. As a pivotal device connecting indoor and outdoor cold sources, the CDU undertakes three core functions: heat exchange, fluid isolation, and flow distribution. However, existing liquid cooling architectures containing CDUs have the following inherent drawbacks:

[0004] First, the proximity temperature difference severely limits the utilization rate of natural cooling sources. In actual engineering, the plate heat exchangers built into the CDU typically exhibit a proximity temperature difference of 5-8℃. When the primary side cooling water temperature is 15℃, the minimum temperature of the coolant supplied to the server on the secondary side can only reach 20-23℃. This 5-8℃ "thermal barrier" directly limits the utilization window of natural cooling sources, forcing the chiller to intervene earlier and increasing the annual mechanical refrigeration energy consumption. Conventional shell-and-tube heat exchangers are mostly single-layer, single-channel structures, limiting the heat exchange area. Furthermore, the inlet and outlet are arranged in the same direction, making short-circuit flow easy and resulting in relatively low heat exchange efficiency.

[0005] Second, the system has a long pipeline, resulting in significant cumulative energy losses. Each stage of the traditional five-stage pipeline involves pump consumption and heat loss. The heat medium needs to travel long distances through pipelines to reach the heat exchanger, incurring temperature and pressure drops along the way, making further optimization of system energy efficiency difficult. One industry-wide technical bias is the conventional design practice of shortening indoor piping on the cold source side, assuming that shorter piping at the cold source end results in less cooling loss. This leads to a lack of proactive measures to lengthen outdoor circulation pipelines and shorten high-temperature piping within the computer room.

[0006] Third, CDU group operation consistency is poor. The flow rate difference of traditional CDU groups can reach 30-40%, resulting in poor overall operating efficiency. The internal pipe bends of the CDU enclosure, internal pump losses, and the temperature difference of the internal plate heat exchanger together constitute additional sources of losses.

[0007] Fourth, the equipment is expensive and requires a large footprint. CDUs require independent rack space, with each unit occupying approximately 4U to tens of U of space, resulting in high equipment costs.

[0008] Fifth, there is a technical bias in the industry regarding equipment installation layout: the industry generally believes that the pipelines on the top of the computer room are dense, there is insufficient space for the arrangement of inlet and outlet pipelines of heat exchange equipment, and the overall transportation and installation of long heat exchange tubes is difficult. Therefore, all heat exchangers are laid on the ground and will not be hoisted. At the same time, there is a lack of staggered arrangement schemes for inlet and outlet, and the pipeline arrangement is crowded after hoisting.

[0009] Sixth, the hot and cold path allocation is unreasonable. In traditional solutions, the hot medium needs to be transported over a long distance to reach the heat exchanger, while the cold medium has a very short path. This does not conform to the design principle of high-efficiency liquid cooling systems: "the hot medium takes a short path, while the overall circulation pipeline for the cold medium is longer and insulated." Conventional chilled water pipes only use single-layer insulation, resulting in high cold loss over long distances.

[0010] Seventh, the load regulation method is simplistic. Existing CDU-less solutions all use a constant flow circulation mode. When the server is consuming low power, the water pump still runs at full load, resulting in significant energy waste.

[0011] Eighth, it is difficult to coordinate with auxiliary cooling equipment such as the heat exchanger at the rear door of the server rack. The traditional CDU architecture mainly serves the chip cold plate and is difficult to support auxiliary cooling equipment such as the heat exchanger at the rear door of the server rack in an efficient manner. The return water end lacks an anti-backflow structure, and the two return water lines are prone to cross pressure.

[0012] In recent years, the industry has begun to explore simplified liquid cooling architectures that eliminate the CDU (coolant cooling unit). Existing solutions couple the server cold plate directly to the outdoor cold source to form a single-loop system. By eliminating the CDU, the rack footprint can be reduced by 12%, rack-level pump power reduced by 43%-88%, and CPU temperature reduced by 5.4-11.5%. However, existing CDU-free solutions have many shortcomings: they are mostly single-loop direct-connection architectures, with no isolation between the coolant and the cold source medium, posing a risk of cross-contamination; the heat exchanger is a single-layer structure with limited heat exchange efficiency; there is no staggered arrangement of inlet and outlet, making it unsuitable for ceiling installation; constant flow operation results in high energy consumption; insufficient insulation on the cooling side leads to significant cold loss over long distances; and systemic issues such as flexible switching between multiple cold sources, backflow of branch medium, and coordination with the heat exchanger at the rack rear door have not been resolved. Furthermore, existing tubing is a single long pipe structure, 10-15 meters in length, which cannot be disassembled, making processing, transportation, and subsequent replacement and maintenance difficult. Currently, no existing technology can simultaneously achieve a complete set of technologies including modular three-layer coaxial bushing, interlayer staggered inlet and outlet, high-pressure isolation on the computing side, dynamic flow matching, and double-layer cold source pipeline insulation. Summary of the Invention

[0013] Purpose of the invention

[0014] This invention aims to provide a liquid cooling system for computing centers that eliminates the need for a dedicated CDU. By reconstructing the system layout, differentiating media, modularizing the structure, designing staggered flow channels, adjusting the dynamic flow rate, implementing double-layer insulation, creating an anti-backflow structure, and optimizing the temperature control logic, it overcomes two inherent technical biases in the industry. This allows various technical means to work together, simultaneously improving heat loss, pump consumption, heat exchange temperature difference, and pipeline cold loss, resulting in comprehensive energy efficiency benefits that cannot be achieved by any single technical means alone.

[0015] Inventive concept

[0016] Existing technologies can only optimize the heat exchanger structure or adjust the cold source mode individually, without comprehensively matching the equipment layout, pipe length distribution, medium pressure level differentiation, heat exchanger inlet and outlet arrangement, modular sleeve structure, composite turbulence structure, cold source control strategy, return water unidirectional protection, and power consumption-linked flow regulation. Two clear technical biases exist in the industry: first, the belief that shorter indoor pipes on the cold source side result in less loss, thus rejecting the idea of ​​lengthening outdoor circulation pipes; second, the belief that complex top-mounted piping makes it impossible to install long-sized heat exchangers. This solution adopts a sandwiched, staggered inlet and outlet arrangement and a segmented modular structure to solve the problems of top-mounted pipe layout and maintenance, while also reversing the lengths of hot and cold pipes, breaking away from conventional design thinking.

[0017] The core of this invention lies in the coupling of six sets of technical features:

[0018] First, the integrated CDU enclosure is eliminated, the heat exchange elements are moved to the ceiling, and the heat exchanger adopts a 10-15m segmented flange splicing structure with staggered inlet and outlet of the mezzanine. This not only shortens the transportation distance of high-temperature fluids inside the machine room, but also obtains additional heat dissipation effect by relying on the lower ambient temperature above the machine room. This eliminates the bending of pipes and pump losses inside the enclosure, and solves the industry pain points of crowded pipes in the hoisting layout and difficulty in maintaining long pipes.

[0019] Second, the internal short path of the computing power side computer room, including the outdoor pipe section, is longer. The cooling side is equipped with a double-layer insulation structure to offset the cold loss caused by the lengthened outdoor pipe, thus reversing the "short hot, long cold" path.

[0020] Third, the three-layer coaxial double-layer sandwich synchronous counterflow structure, combined with the axial flow equalization plate and non-uniform composite turbulence, improves the heat transfer coefficient by more than 35% compared with a single protrusion at the same flow rate, which is far higher than the 12%-18% heat transfer gain of a single structure; the computing power side loop pressure level is higher, further isolating the risk of media infiltration and contamination.

[0021] Fourth, the two circuits use different media, a one-way valve is added to the return water branch, and the tap water branch is independently isolated as an open auxiliary cold source to solve the problems of media contamination and return water pressure surge and backflow.

[0022] Fifth, add a power consumption acquisition unit to dynamically match the flow of both loops according to the real-time load of the server, thus getting rid of the energy waste of traditional fixed flow operation;

[0023] Sixth, three-mode cold source, 2℃ offset hysteresis control, indirect heat exchange with tap water, and pressure and flow control of the heat exchanger at the rear door of the cabinet.

[0024] Using any single technology alone can only achieve localized performance improvements. Combining multiple structures, however, leads to simultaneous optimization of temperature difference, pump consumption, annual energy efficiency, operational stability, and energy savings under varying operating conditions, resulting in a technical effect far exceeding the sum of individual technologies. Moving the heat exchanger to the ceiling shortens the hot medium pipeline, while the long-distance transport of the cold medium is equipped with a double-layer insulation structure, further reducing cooling loss. This overall solution deviates from conventional technical choices in this field and demonstrates originality.

[0025] Technical solution

[0026] (I) Overall System Architecture

[0027] This invention does not include integrated CDU equipment. A traditional CDU is a complete integrated enclosure unit comprising a circulating pump, frequency converter, filter, plate heat exchanger, electrical control unit, monitoring and sensing unit, and connecting pipes and valves. This invention eliminates this integrated multi-functional enclosure; heat exchange and distribution functions are achieved separately by independent concentric tube heat exchangers and water distributors / collectors. The system chain is shortened from the traditional five stages to three stages: "chip cold plate → concentric tube heat exchanger → cold source," reducing pump consumption and heat loss in intermediate links. No external heat exchange equipment is added between the two loops; the system relies solely on the concentric tube heat exchanger to complete all heat exchange.

[0028] This invention forms two fluidly isolated circulating loops. The computing side is filled with high-pressure insulating coolant, while the refrigeration side is filled with conventional industrial cooling water, with the media pressure and type being distinct. The two loops exchange heat only through the metal walls within concentric tube heat exchangers, preventing the fluids from coming into contact with each other and avoiding contamination of the computing side media. The circulating pump sets are respectively arranged inside the corresponding closed loops, with no cross-loop installations.

[0029] The concentric tube heat exchanger is suspended from the top of the computing room and uses segmented flange modular splicing. The axial length of the heat exchanger body is 10-15m. The inlet and outlet of the sandwich flow channel are arranged in a staggered direction to solve the problem of congestion in the top pipeline layout. It takes advantage of the lower ambient temperature in the upper layer to assist in heat dissipation. The total length of the internal pipeline of the computing side computer room is 2-10m, and the overall circulation pipeline length of the cooling side, including the outdoor pipeline, is greater than 50m. The cooling side pipeline adopts a double-layer insulation structure with an inner rubber and plastic layer and an outer protective shell to offset the cold loss caused by the length of the outdoor pipeline. This achieves a system layout in which the hot medium takes a short path and the overall circulation pipeline of the cold medium is longer.

[0030] (ii) Concentric tube heat exchanger

[0031] A concentric tube heat exchanger consists of at least two nested layers of pipes aligned concentrically. Preferably, it has a three-layer structure: an outer tube, a middle tube, and an inner tube, with an overall axial length of 10-15m, connected by segmented flanges. A first interlayer flow channel is formed between the outer and middle tubes, a second interlayer flow channel is formed between the middle and inner tubes, and a central flow channel is formed inside the middle tube. When this concentric tube heat exchanger has a three-layer pipe structure, the inlet and outlet of the two interlayer flow channels are staggered, the cooling water flow direction within the two interlayer flow channels is consistent, and both are arranged counter-currently to the cooling liquid flow direction in the central flow channel.

[0032] The inner wall of the heat exchanger pipes features pyramidal, conical, and cylindrical turbulence protrusions, with a higher density in areas with higher heat loads than in conventional areas. These multi-shaped turbulence protrusions generate eddies and turbulence of varying scales, working together to continuously disrupt the thermal boundary layer. An axial flow equalization plate is installed at the interlayer inlet to eliminate fluid deviation. Teardrop-shaped positioning support structures are installed between the pipes, with their tips pointing in the direction of fluid flow, serving both positioning and turbulence-disrupting functions.

[0033] The heat exchanger is equipped with an automatic air vent valve at its highest point and a drain valve at its lowest point to prevent air blockage and liquid accumulation. The tube wall surface has a limiting structure to prevent deformation caused by fluid impact during operation.

[0034] (III) Dual Closed-Loop System Architecture

[0035] First loop (cacheration side coolant closed loop): chip cold plate → water collector → hot water recovery pump → concentric tube heat exchanger central flow channel (heat release) → water distributor → chip cold plate. The internal pipeline length in the computer room is 2-10m, and a one-way valve is installed on the return water branch.

[0036] Second loop (cooling side cold water closed loop): concentric tube heat exchanger jacketed flow channel (heat absorption) → cold water pump → dry cooler / refrigeration unit (heat release) → concentric tube heat exchanger, the overall circulation pipeline length is greater than 50m, and the cold water pipeline is wrapped with a double-layer insulation structure.

[0037] The system is equipped with a power consumption acquisition unit to collect server power consumption in real time and dynamically adjust the output flow of the two loop water pumps to reduce pump power under low load.

[0038] (iv) Switching between three-mode cold sources

[0039] The controller prioritizes the primary side inlet water temperature as the basis for judgment, with ambient temperature as a backup monitoring parameter. When the primary side temperature sensor fails, it switches to ambient temperature for mode determination. A 2℃ hysteresis is set in the temperature control range, and the temperature rise switching threshold is 2℃ higher than the temperature fall threshold to avoid frequent start-stop cycles at critical temperatures.

[0040] Pure dry cooler mode: When the temperature is below 5℃, only the dry cooler is turned on, and the refrigeration unit is turned off.

[0041] Dry cooler and tap water combined mode: When the temperature is greater than or equal to 5℃ and less than or equal to 20℃, the dry cooler pre-cools, and the tap water serves as an open auxiliary cold source, which indirectly exchanges heat with the primary loop through an independent plate-type isolation heat exchanger, thus achieving "cold water extraction without water extraction".

[0042] Combined dry cooler and refrigeration unit mode: When the temperature is above 20℃, the dry cooler pre-cools and the refrigeration unit supplements the cooling.

[0043] The water supply branch is equipped with an independent plate heat exchanger, a pressure-stabilizing heat exchange unit, and a backflow preventer to ensure indirect heat exchange, stable flow, and safe water supply.

[0044] (v) Integration with the heat exchanger at the rear door of the server rack

[0045] The water distributor has multiple output ports, including at least one for connecting to the heat exchanger at the rear door of the server rack. Each port is equipped with an independent regulating valve and a pressure balancing valve. A return water pressure regulating valve is installed at the return water collection point, and each return water branch is equipped with a check valve to balance pressure and prevent backflow and cross-flow of the medium. The flow rate priority of the chip cold plate branch is higher than that of the heat exchanger branch at the rear door of the server rack.

[0046] (vi) Monitoring and security protection

[0047] The computing-side loop is equipped with conductivity and pressure sensors to monitor coolant purity and loop operating pressure in real time. The control system integrates differential pressure protection, over-temperature interlock, conductivity anomaly alarm, and fault alarm logic. The circulating pump and cooling source module are configured with N+1 redundancy to ensure uninterrupted equipment operation.

[0048] Beneficial effects

[0049] (1) The layout architecture overcomes industry technical biases: the use of segmented modular sleeves and staggered inlet and outlet arrangements solves the problems of top-mounted pipe layout and maintenance; the inversion of hot and cold pipe lengths, combined with double-layer insulation to offset outdoor cold loss, and the ceiling location to obtain heat dissipation gains by utilizing the low-temperature environment of the upper layer, significantly reducing overall pump consumption. This layout method is not a conventional choice in the industry and brings unexpected energy-saving effects.

[0050] (2) Outstanding heat exchange performance: The pure counter-current double-layer synchronous design, combined with an axial flow equalization plate, achieves a temperature reduction of 1-3℃ at flow velocities of 0.8-2.0m / s, which is 4-7℃ lower than that of CDU plate heat exchangers; the composite turbulence structure improves the heat transfer coefficient by more than 35%. High-pressure loop on the computing side eliminates media infiltration and contamination.

[0051] (3) Energy saving under variable operating conditions: The circulating flow rate is dynamically adjusted according to the server power consumption. Compared with the traditional fixed flow rate mode, the pump energy consumption is reduced by 15%-22% under low load conditions.

[0052] (4) Simplified and energy-saving links: The heat dissipation links are shortened from five levels to three levels, the power of the cabinet-level pump is reduced by 43%-88%, and the total cooling energy consumption is reduced by 13%-36%.

[0053] (5) Stable heat dissipation: CPU operating temperature can be reduced by 5.4-11.5℃, avoiding the problem of high temperature throttling. The one-way valve eliminates the risk of backflow and pressure surge, improving operational stability. The modular sleeve can be replaced in sections, reducing future maintenance costs.

[0054] (6) Cost optimization: Eliminating the purchase of integrated CDU equipment reduces equipment investment by 20%-30% and cabinet footprint by 12%.

[0055] (7) Intelligent temperature control operation: with a 2℃ hysteresis range with offset, it eliminates frequent mode switching and the annual comprehensive PUE can reach 1.05-1.10.

[0056] (8) Water-saving and safety advantages: Tap water is used as an independent open branch for indirect heat exchange via an isolation heat exchanger, and the media do not come into contact with each other, achieving zero water consumption. The media and pressure levels of the two circuits are separated to avoid contamination of the server-side coolant.

[0057] (9) Full-link heat dissipation management: The same cold source supplies the chip cold plate and the heat exchanger at the back door of the cabinet in a hierarchical manner to complete the overall heat dissipation layout of the computer room.

[0058] (10) Multiple safety redundancies: conductivity monitoring, pressure monitoring, differential pressure protection, over-temperature interlock, exhaust and drainage structure, N+1 redundancy configuration to meet the continuous operation requirements of Class A data centers. Attached Figure Description

[0059] Figure 1 Overall architecture and dual closed-loop diagram

[0060] Figure 2 Schematic diagram of the cross-sectional structure of a concentric circular tube heat exchanger

[0061] Figure 3 Longitudinal section of concentric tube heat exchanger and schematic diagram of countercurrent heat exchange principle

[0062] Figure 4 Schematic diagram of the distribution and local magnification of turbulence protrusions.

[0063] Figure 5 Schematic diagram of teardrop-shaped positioning support structure

[0064] Figure 6 Schematic diagram of the three-mode cold source switching module

[0065] Figure 7 Control method flowchart

[0066] Figure 8 Schematic diagram of hoisting deployment and maintenance walkway

[0067] Explanation of reference numerals in the attached figures:

[0068] 1-Server cold plate, 2-Water collector, 3-Hot water recovery pump, 4-Concentric tube heat exchanger, 5-Dry cooler, 6-Refrigeration unit, 7-Cold liquid output pump, 8-Water distributor, 15-Rack rear door heat exchanger, 16-One-way valve, 17-Power consumption acquisition unit, 19-Hanging bracket, 20-Guide rail, 21-Maintenance walkway, 22-Double-layer insulation structure, 41-Outer pipe, 42-Middle pipe, 43-Inner pipe, 44-First interlayer flow channel, 45-Second interlayer flow channel, 46-Central flow channel, 47-Pyramid-shaped turbulence protrusion Starting from 48, conical or cylindrical turbulence protrusions; 49, teardrop-shaped positioning support; 50, limiting structure; 51, axial flow equalization plate; 410, high-temperature coolant inlet; 411, high-temperature coolant outlet; 412, cooling water inlet; 413, cooling water outlet; 415, flange splice section; 416, automatic air vent valve; 417, drain valve; 52, electric switching valve; 53, temperature sensor; 54, controller; 91, tap water branch; 92, independent plate-type isolation heat exchanger; 93, pressure-stabilizing heat exchange unit. Detailed Implementation

[0069] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0070] Example 1: Deployment Scheme for a 1000-cabinet Computing Center

[0071] This embodiment is suitable for AI computing power data centers with a single rack of 20kW and a total power of 20MW. The concentric tube heat exchanger 4 is assembled from multiple flange splicing sections 415, and the axial length of the heat exchanger body is 12m. The heat exchanger outer tube 41, middle tube 42, and inner tube 43 have a wall thickness of 3mm. The middle tube 42 and inner tube 43 are made of copper tubing with a thermal conductivity ≥380W / (m・K).

[0072] A first interlayer flow channel 44 is formed between the outer tube 41 and the middle tube 42, and a second interlayer flow channel 45 is formed between the middle tube 42 and the inner tube 43. The inlet and outlet of the two interlayer flow channels are staggered, and an axial flow equalization plate 51 is installed at the interlayer inlet. Two types of composite turbulence protrusions, 47 and 48, are welded to the inner side of the heat exchange tube wall, with a higher density of protrusions in areas with high heat load. A teardrop-shaped positioning support 49 is installed between the pipes, with the support tip facing the fluid flow direction. An automatic exhaust valve 416 is installed at the top of the concentric circular tube heat exchanger 4, and a drain valve 417 is installed at the bottom. An integrally formed limiting structure 50 on the tube wall suppresses deformation caused by fluid impact.

[0073] The concentric tube heat exchanger 4 is hoisted and arranged by the hoisting bracket 19, and the equipment is equipped with guide rails 20 and maintenance walkways 21 on both sides.

[0074] The system is divided into two independent closed-loop circulation loops:

[0075] The first loop includes server cold plate 1, water collector 2, hot water recovery pump 3, concentric tube heat exchanger 4, cold liquid output pump 7, water distributor 8, and rack rear door heat exchanger 15. All return water branch pipes are equipped with one-way valves 16. The total length of the internal piping in the computing power side computer room is 8m, and the pressure resistance level of the loop is higher than that of the second loop.

[0076] The second loop includes a concentric tube heat exchanger 4, a jacketed flow channel, a dry cooler 5, and a refrigeration unit 6. The total length of the overall circulation pipeline is 65m, and the outdoor pipe section is covered with a double-layer insulation structure 22.

[0077] The water distributor 8 is equipped with 40 output interfaces, one of which connects to the server cold plate 1, and the remaining interfaces are adapted to the heat exchanger 15 at the rear door of the rack. Each interface is equipped with an independent regulating valve and a pressure balancing valve, and a return water pressure regulating valve is installed at the return water collection point. The power consumption acquisition unit 17 transmits the server operating power to the controller 54 in real time. The medium operating velocity is 1.2m / s, and the circulation flow rate of a single heat exchanger is 25m³ / h. The cooling water in the two-layer sandwich flow channel flows in the same direction, forming a pure counter-current heat exchange with the high-temperature coolant inside the central flow channel 46.

[0078] Actual operating results: The integrated CDU enclosure was eliminated, reducing the cabinet footprint by 12%, and the heat exchange temperature difference stabilized at ≤2℃; the composite turbulence protrusions 47 and 48 enhanced heat exchange in synergy, increasing the heat transfer coefficient by 36% compared to a single cylindrical protrusion; the controller 54 dynamically adjusted the operating speed of each circulating pump according to the real-time load, reducing pump energy consumption by 18% under low load conditions compared to a constant flow system; the one-way valve 16 effectively blocked cross-pressure of return water from different branches, and the water supply priority of the server cold plate 1 was higher than that of the heat exchanger 15 at the rear door of the cabinet.

[0079] Example 2: Implementation Case of Direct Cooling and Isolation Heat Exchange for Tap Water

[0080] A branch water supply line 91 is added, which connects the municipal water supply network and the reinjection well. Along the pipeline, an independent plate-type isolation heat exchanger 92, a pressure-stabilizing heat exchange unit 93, and a backflow preventer are connected in series. The tap water only completes heat exchange inside the independent plate-type isolation heat exchanger 92 and does not come into contact with the insulating coolant on the computing side throughout the entire process, realizing a cooling-only operation mode with zero water consumption.

[0081] After heat exchange in the concentric tube heat exchanger 4, the 25°C cold water is transported to the independent plate-type isolation heat exchanger 92, where it exchanges heat with the 18°C ​​municipal tap water to cool down to 20°C before returning to the refrigeration circuit. The pressure-stabilizing heat exchange unit 93 compensates for fluctuations in municipal water pressure in real time to stabilize the heat exchange flow. The controller 54 controls the on / off of the tap water branch 91 through the electric switching valve 52c. When the primary side temperature collected by the temperature sensor 53 is in the range of 5 to 12°C, the system automatically starts the dry cooler 5 and the tap water joint operation mode.

[0082] Example 3: Verification of 65℃ return water cooling condition

[0083] The server cold plate 1 discharges 65°C high-temperature coolant, which is then transported to the central flow channel 46 of the concentric tube heat exchanger 4 via the hot water recovery pump 3. 20°C cooling water flows from the cooling water inlet 412 into the first interlayer flow channel 44 and the second interlayer flow channel 45. The flow direction of the interlayer medium is consistent, and it exchanges heat with the high-temperature coolant inside the central flow channel 46 in a countercurrent manner. The medium flow velocity is uniformly 1.2m / s, and the overall length of the heat exchanger is 12m.

[0084] After heat exchange, the outlet temperature of the high-temperature coolant is controlled at 42-45℃, and the heat exchange temperature difference is stable at 2℃, which can meet the heat dissipation requirements of 2000W-level AI chips; the turbulence protrusions 47 and 48 are 1-5mm high and are evenly distributed on the inner wall of the middle tube 42 and the inner tube 43, continuously disrupting the fluid thermal boundary layer; compared with the traditional matching CDU plate heat exchanger, the cooling rate is increased by 6-7℃ under the same operating conditions.

[0085] Example 4: Manufacturing and processing method of concentric tube heat exchanger

[0086] Processing steps:

[0087] 1. Weld the inner tube 43 and the middle tube 42 together with the teardrop-shaped positioning support 49, and control the concentricity deviation to be ≤0.5mm;

[0088] 2. Weld another set of teardrop-shaped positioning supports 49 between the middle tube 42 and the outer tube 41;

[0089] 3. A limiting structure 50 is integrally machined on the outer wall of the heat exchange tube;

[0090] 4. The 47 and 48 turbulence protrusions are fixed to the inner wall of the heat exchange tube using laser brazing.

[0091] 5. Adjust the inlet and outlet of the first interlayer flow channel 44 and the second interlayer flow channel 45 to be staggered;

[0092] 6. High-temperature coolant inlet 410, high-temperature coolant outlet 411, cooling water inlet 412, and cooling water outlet 413 are welded to both ends of the pipe body respectively;

[0093] 7. The multi-section pipe body is assembled by flange splicing section 415 sealing, and the water pressure and air tightness tests are completed as a whole;

[0094] The flange splice section 415 can be disassembled and replaced separately, making the later inspection and maintenance of the equipment convenient.

[0095] Example 5: Adaptation scheme for a simplified two-layer concentric tube heat exchanger

[0096] Suitable for medium computing power scenarios of 10-30kW per rack, the concentric tube heat exchanger 4 is equipped with only an outer tube 41 and an inner tube 43, forming a single-layer sandwich flow channel 44 between them. The inner tube 43 has a central flow channel 46 inside. High-temperature coolant enters the central flow channel 46 from the high-temperature coolant inlet 410, and cooling water flows in the opposite direction into the sandwich flow channel 44 to form counter-current heat exchange. The medium flow velocity is 1.2m / s, and the heat exchange is close to a temperature difference of 2-4℃. The structure of the supporting equipment such as the water distributor 8, water collector 2, double-layer insulation structure 22, and hanging bracket 19 is completely consistent with the three-layer heat exchanger scheme.

[0097] Example 6: Verification of Temperature Sensor Switching and Hysteresis Control Logic

[0098] The controller 54 has a built-in 2℃ temperature hysteresis offset control logic, a cooling switching threshold of 5℃, and a heating exit threshold of 7℃; the power consumption acquisition unit 17 synchronizes the server load signal to the controller 54 in real time, and synchronously reduces the operating flow of the hot water recovery pump 3 and the cold liquid output pump 7 when the load is halved.

[0099] Under normal operating conditions, the controller 54 prioritizes reading the primary water temperature collected by the temperature sensor 53. If the temperature sensor 53 fails, the system automatically switches the ambient temperature as the basis for mode determination. When the ambient temperature is 8°C, the dry cooler 5 continues to operate alone. When the ambient temperature rises to 12°C, the system switches the dry cooler 5 to the joint operation mode with the refrigeration unit 6, and all temperature control and fault protection logic is executed uniformly by the controller 54.

[0100] Industrial applicability

[0101] The concentric tube heat exchanger 4, the teardrop-shaped positioning support 49, and the composite turbulence protrusions 47 / 48 can all be mass-produced using conventional machining processes. The controller 54 relies on a general-purpose PLC paired with a variable frequency pump to achieve flow regulation. All components of the entire system can be purchased in bulk from the market. This system is suitable for newly built AI intelligent computing centers, liquid cooling retrofits of existing computing power rooms, and containerized edge computing stations, and is especially suitable for high-density computing power cooling projects in areas with low PUE and water shortages.

[0102] The above description is merely a preferred embodiment of the present invention. Any simple substitutions or equivalent modifications made based on the technical concept of the present invention shall fall within the protection scope of the present invention.

Claims

1. A CDU-free computing center liquid cooling system, characterized in that, Includes concentric tube heat exchangers, water distributors, water collectors, cold source modules, and circulating pump sets; The concentric tube heat exchanger is formed by at least two layers of pipes nested coaxially, with an interlayer flow channel formed between adjacent pipes, and the innermost pipe forming the central flow channel. The water distributor is connected to the cold liquid outlet of the concentric tube heat exchanger and distributes low-temperature coolant to each server cold plate; the water collector collects the high-temperature coolant after the server cold plates absorb heat and transports it to the concentric tube heat exchanger; the cold source module is connected to the primary side of the concentric tube heat exchanger; each group of circulating pumps is set in the corresponding closed loop to drive the medium circulation. This system eliminates the integrated CDU complete cabinet unit and does not have an independent integrated cabinet that simultaneously integrates the circulating pump, plate heat exchanger, electrical control, sensors, and pipeline valves; the server cold plate return pipeline is directly connected to the concentric tube heat exchanger, and the cold liquid outlet of the concentric tube heat exchanger is directly connected to the water distributor, forming a closed-loop liquid cooling architecture without CDU. The system has two isolated fluid loops: the first loop is a closed loop on the computing side filled with insulating coolant, and the second loop is a closed loop on the refrigeration side filled with industrial cooling water. The two types of media do not communicate with each other, and the computing side loop has a higher pressure rating. The two loops exchange heat only through the metal wall of a concentric tube heat exchanger, without any external heat exchange equipment, and the circulating pumps are not installed across the loops. When the concentric tube heat exchanger adopts a three-layer pipe structure, the inlet and outlet of the two-layer interlayer flow channels are arranged in opposite directions, the cooling water in the interlayer flows in the same direction, and it exchanges heat with the cooling liquid in the central flow channel in a counter-current manner; the total length of the computing side computer room piping is shorter than the cooling side piping including the outdoor pipe section, and the cooling side piping adopts a double-layer insulation structure.

2. The system according to claim 1, characterized in that, The concentric tube heat exchanger has a three-layer concentric tube structure, consisting of an outer tube, a middle tube, and an inner tube nested together. The outer tube and the middle tube form a first interlayer flow channel, the middle tube and the inner tube form a second interlayer flow channel, and the middle tube forms a central flow channel. The middle tube and the inner tube are made of copper with a thermal conductivity of not less than 380 W / (m·K). The axial length of the concentric tube heat exchanger body is 10-15 m, and the heat exchanger adopts a segmented flange modular splicing structure.

3. The system according to claim 1 or 2, characterized in that, The concentric tube heat exchanger adopts a pure counter-current arrangement, with high-temperature coolant flowing in the central channel along the first direction and low-temperature cooling water flowing in the jacket channel in the opposite direction.

4. The system according to claim 1 or 2, characterized in that, The concentric circular tube heat exchanger has multiple turbulence protrusions on the inner side of the heat exchange tube wall. These turbulence protrusions include at least one of pyramid, conical, and cylindrical shapes. The density of these turbulence protrusions is greater in areas with higher heat loads than in conventional areas. A teardrop-shaped positioning support structure is provided between adjacent tubes. The tip of the teardrop-shaped structure faces the direction of fluid flow, and its height is equal to the width of the corresponding interlayer flow channel, serving both positioning and turbulence functions. An axial flow equalization plate is provided at the inlet of the interlayer flow channel.

5. The system according to claim 1, characterized in that, The cold source module includes a dry cooler and a refrigeration unit, which are connected in parallel. The system also includes a controller, temperature sensors, and a power consumption acquisition unit. The controller can dynamically adjust the circulation flow of the two loops based on the real-time power consumption of the server. The controller prioritizes the primary side inlet water temperature as the judgment criterion, with ambient temperature as a backup monitoring parameter. When the primary side temperature sensor fails, the ambient temperature is used for mode determination. The controller automatically switches the cold source mode according to the temperature: when the temperature is below 5℃, it switches to pure dry cooler mode, and the refrigeration unit is turned off; when the temperature is greater than or equal to 5℃ and less than or equal to 20℃, it switches to a combined dry cooler and tap water mode, with the tap water branch indirectly exchanging heat with the primary loop through an independent plate-type heat exchanger; when the temperature is above 20℃, it switches to a combined dry cooler and refrigeration unit mode. The controller has a 2℃ temperature hysteresis range, and the temperature rise switching threshold is 2℃ higher than the temperature fall threshold to avoid frequent mode switching.

6. The system according to claim 5, characterized in that, It also features a direct cooling module for tap water, including an inlet and outlet water interface connected to the municipal water supply network or a self-supplied well, an independent plate-type isolation heat exchanger, and a pressure-stabilizing heat exchange unit. The tap water branch is an open heat exchange branch, serving only as an auxiliary cooling source for the system and not directly connected to the server's circulation loop. After the tap water undergoes indirect heat exchange with the primary loop through the independent plate-type isolation heat exchanger, it flows back to the municipal water supply network or reinjection well, achieving zero-water-consumption operation with cooling but no water intake. The tap water and the system's cooling medium do not come into contact throughout the entire process. A backflow preventer is installed on the return water pipe. The pressure-stabilizing heat exchange unit is used to compensate for fluctuations in municipal water pressure and maintain a stable heat exchange flow rate.

7. The system according to claim 1, characterized in that, The water distributor has multiple output interfaces, including at least one interface for connecting to the heat exchanger at the rear door of the cabinet. Each interface is equipped with an independent regulating valve and a pressure balancing valve. A one-way valve is installed on each return water branch. A return water pressure regulating valve is installed at the return water collection point to balance the return water pressure of the chip cold plate branch and the heat exchanger at the rear door of the cabinet. The low-temperature coolant is divided into two paths by the water distributor, one path is supplied to the chip cold plate, and the other path is supplied to the heat exchanger at the rear door of the cabinet, realizing a distribution architecture with one source for two uses.

8. The system according to claim 1, characterized in that, The concentric tube heat exchanger is suspended at the top of the computing room. The ambient temperature above the room is lower than that of the ground area, thus gaining environmental heat dissipation gain. As a preferred embodiment, the total length of the internal pipelines in the computing room is set to 2-10m, and the overall circulation pipeline length on the cooling side, including the outdoor pipelines, is greater than 50m. The double-layer insulation structure of the second loop consists of an inner rubber and plastic insulation layer and an outer protective shell.

9. The system according to claim 1, characterized in that, The concentric tube heat exchanger is equipped with an automatic vent valve at its highest point and a drain valve at its lowest point; the computing power side loop is equipped with a conductivity sensor and a pressure monitoring sensor to monitor the coolant purity and loop pressure in real time.

10. The system according to claim 1, characterized in that, The concentric tube heat exchanger has a limiting structure on its tube wall surface to prevent deformation caused by fluid impact during operation; the circulating pump group and cold source module are both configured with N+1 redundancy, with N units operating online and 1 unit in hot standby mode; the system has redundant pipelines and an automatic switching bypass structure, and when the online equipment fails, the standby equipment automatically starts to take over, with a switching time of no more than 2 seconds.

11. A method for manufacturing a CDU-free computing center liquid cooling system, characterized in that, The concentric circular tube heat exchanger has a two- or three-layer pipe structure. When the concentric circular tube heat exchanger has a three-layer pipe structure, it consists of three concentrically nested pipes: an outer pipe, a middle pipe, and an inner pipe. The heat exchanger is assembled using segmented flange modular splicing. The manufacturing steps are as follows: the inner pipe and the middle pipe are welded and fixed together using a teardrop-shaped positioning support structure to ensure that the concentricity deviation does not exceed 0.5 mm; the middle pipe and the outer pipe are welded and fixed together using another set of teardrop-shaped positioning support structures; a limiting structure is set on the surface of the pipe wall; pyramid-shaped, conical, and cylindrical turbulence protrusions are fixed to the inner side of the heat exchange tube wall by laser welding or brazing; the inlet and outlet of the sandwich flow channel are arranged in a staggered manner; the inlet pipe and outlet pipe are welded at both ends respectively; and the whole system is subjected to pressure testing and airtightness testing.

12. A de-CDU liquid cooling control method based on the system according to any one of claims 1 to 10, characterized in that, Includes the following steps: First loop: The water collector collects the high-temperature coolant from each server cold plate and delivers it to the central flow channel of the concentric tube heat exchanger via the hot water recovery pump. After cooling, it is distributed to each server cold plate via the water distributor, forming a short-path closed loop. The flow priority of the chip cold plate branch is higher than that of the rack rear door heat exchanger branch. The return water branch relies on a one-way valve to prevent the medium from flowing back. Second loop: The cold water pump delivers cooling water to the jacketed flow channel of the concentric circular tube heat exchanger with staggered inlet and outlet, and performs pure counter-current heat exchange with the high-temperature coolant in the central flow channel. When the concentric circular tube heat exchanger has a three-layer pipe structure, the medium flow direction of the two jacketed flow channels is consistent, and both flow counter-currently to the central flow channel. The water that has absorbed heat and increased in temperature returns to the dry cooler or the refrigeration unit to cool down, forming a long-path closed loop. The power consumption acquisition unit acquires the server's operating power consumption in real time, and the controller dynamically matches and adjusts the circulation flow of the first and second loops based on the power consumption data; the temperature sensor monitors the primary side inlet water temperature in real time, and the controller prioritizes the primary side inlet water temperature as the basis for judgment, and automatically switches the cold source mode according to the temperature. During the switching process, a 2℃ hysteresis interval is set, and the temperature rise switching threshold is 2℃ higher than the temperature fall threshold; when the primary side temperature sensor fails, the ambient temperature is used to determine the mode. When the system differential pressure exceeds the preset threshold, the temperature exceeds the safety limit, or the coolant conductivity exceeds the standard, the controller will trigger differential pressure protection, over-temperature interlock, and maintenance alarm respectively. When the main cooling source fails, the controller automatically switches to the backup cooling source, with a switching time of no more than 2 seconds.

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