A two-phase liquid cooling system based on nanoparticle deposition boiling enhancement mechanism

Abstract

The present invention relates to a two-phase liquid cooling system based on the nanoparticle deposition boiling enhancement mechanism, comprising: an external cooling unit, an immersion cooling cabinet, a cooling water distribution unit, a nanofluid distribution unit, and a coolant distribution unit; the immersion cooling cabinet, nanofluid distribution unit, and coolant distribution unit are all located within a cabinet area; and the data center computer room comprises multiple cabinets connected in parallel. Compared with existing technologies, the present invention improves boiling capacity while reducing improvement costs through a simple and inexpensive nanoparticle self-assembly method. It also creates a non-uniform wettability surface based on its own boiling mechanism, effectively improving the energy utilization efficiency of the two-phase liquid cooling system. By controlling the strength of nanoparticle deposition through differences in thermally conductive materials, it selectively enhances the boiling surface, effectively improving the pool boiling effect, and thus improving the efficiency of the cooling system.

Description

Technical Field

[0001] The present invention relates to the technical field of data center cooling, and in particular to a two-phase liquid cooling system based on a nanoparticle deposition boiling enhancement mechanism. Background Art

[0002] According to the International Energy Agency (IEA)'s "Electricity Report 2024," with the advent of the big data era and the rapid development of AI technology, global data center electricity demand is expected to rise from 460 TWh in 2022 to 620-1050 TWh in 2026. According to the IEA's "Electricity Report 2024," my country's data center electricity consumption will exceed 400 billion kWh in 2025, accounting for approximately 4% of national electricity consumption, with data center cooling systems accounting for over 35% of total power consumption. Data center cooling methods are primarily divided into air cooling and liquid cooling. Air cooling and single-phase liquid cooling (primarily using single-phase cold plate cooling) are the most common and mature. However, with the advent of the big data era, chip-side loads and heat flux densities have been increasing annually since 2001. Conventional air cooling systems are no longer able to meet the heat dissipation requirements of high-power, high-heat-flux chips. New, high-efficiency liquid cooling technologies suitable for high-power electronic devices are gradually replacing air cooling and are now widely used in the international market. Immersion cooling has seen steady growth in data center cooling in recent years due to its efficient heat transfer and stable, safe cooling mode. However, due to the limited space available for data center cabinets and chips compared to outdoor cooling units (such as cooling towers and compression chillers), high-power cabinets and chips require maximizing instantaneous heat transfer within this limited space. Therefore, two-phase liquid cooling technology, involving a phase change working fluid, offers greater potential for application.

[0003] In summary, choosing an energy-efficient and efficient cooling system and appropriate cooling system optimization methods can improve the cooling capacity of data centers and reduce energy consumption, which is of great significance.

[0004] In the current research on two-phase immersion cooling, there are two very important evaluation parameters, namely critical heat flux (CHF) and heat transfer coefficient (HTC). At present, the research on the pool boiling enhancement mechanism usually requires relatively complex modification and preparation of the heat source surface, such as laser etching, vapor deposition, spraying, sintering, CNC machine processing, etc., to change the parameters such as wettability, roughness, capillary core pulling ability of the boiling surface, affect the bubble nucleation rate, detachment diameter and liquid phase replenishment ability, etc., thereby effectively enhancing CHF and HTC. However, these methods are costly and the preparation process is relatively complicated, and are not suitable for large-scale production. Therefore, it is crucial to choose a suitable and low-cost pool boiling enhancement method to improve the two-phase cooling system of data center cooling. Among them, the specific problems of two-phase immersion cooling in data centers are: (1) The placement of servers in two-phase immersion liquid cooling in data centers is relatively complex, usually involving multiple angles, but most of the current intellectual property rights for the pool boiling mechanism only analyze the bubble rising mechanism of horizontal heat sources. (2) In data center cabinets, due to the angle sensitivity of the two-phase immersion cooling system, the horizontal placement of the server is not conducive to the detachment and rise of bubbles. If a special guide structure is used for guidance, the system complexity will increase. (3) The vertical placement of the server is conducive to the detachment and rise of bubbles, but from the perspective of the pool boiling mechanism, compared with the horizontal heat source, the vertical heat source has a more concentrated gas phase and the gas and liquid phases are easier to separate, but under the influence of gravity, the liquid phase is difficult to replenish. (4) The vertical heat source itself has a boiling gradient. There are currently few existing technologies for enhancing pool boiling that are suitable for vertical heat sources. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of high cost and low energy efficiency in the above-mentioned existing technologies and to provide a two-phase liquid cooling system based on the nanoparticle deposition boiling enhancement mechanism, which can improve the boiling ability while reducing the improvement cost through simple and low-cost nanoparticle self-assembly; prepare non-uniform wettability surface according to its own boiling mechanism, and effectively improve the energy utilization efficiency of the two-phase liquid cooling system; control the strength of nanoparticle deposition through differences in thermal conductive materials, thereby selectively strengthening the boiling surface, effectively improving the pool boiling effect, and thus improving the efficiency of the cooling system.

[0006] The present invention provides a two-phase liquid cooling system based on the nanoparticle deposition boiling enhancement mechanism, comprising: an external cooling unit, an immersion cooling cabinet, a cooling water distribution unit, a nanofluid distribution unit, and a coolant distribution unit; the immersion cooling cabinet, the nanofluid distribution unit, and the coolant distribution unit are all arranged in a cabinet area; the data center computer room is a multi-cabinet parallel connection;

[0007] The system includes two operating modes: the nanoparticle self-deposition boiling enhancement stage before cooling and the actual cooling stage. In the boiling enhancement stage, the nanofluid distribution pipeline sends the nanofluid in the nanofluid distribution unit into the immersion cooling cabinet. In this stage, although the cooling capacity of the nanofluid is slightly weaker than that of low-boiling-point coolants (such as electronic fluorine liquid), it can still provide a certain cooling capacity. At this time, the servers in the immersion cooling cabinet are operating normally. When the servers generate heat, the nanofluid reaches the saturation point and begins to boil. At this time, the high thermal conductivity nanoparticles in the nanofluid will naturally deposit on the boiling surface. The deposition of nanoparticles on the boiling surface will increase the nucleation points of bubbles and enhance the thermal conductivity of the hot surface. The bubble detachment diameter is reduced and the bubble detachment frequency is increased, thereby enhancing the pool boiling efficiency, that is, the cooling efficiency of the immersion cooling system. The rising bubbles bring heat to the heat exchanger on the top of the immersion cooling cabinet. The cooling water distribution unit sends low-temperature cooling water to the top heat exchanger through the cooling water supply pipeline. The bubbles condense at the top heat exchanger and bring heat to the cooling water. The cooling water then flows into the side wall heat exchanger (the purpose of the side wall heat exchanger here is to facilitate cooling water integration and also to take away a small amount of heat from the side wall of the immersion cooling cabinet). Finally, it is sent to the cooling water distribution unit through the cooling water return pipeline. The cooling water distribution unit brings heat to the external cooling unit through the cooling water heat exchange pipeline. The external cooling unit cools the return water and then sends it back to the cooling water distribution unit to complete the cycle.

[0008] However, during the boiling enhancement stage, the cooling capacity of the nanofluid is lower than that of the traditional boiling coolant, and as the nanoparticles are deposited on the surface of the heat source for a long time, the bubble nucleation holes will be blocked, and an excessively thick layer of nanoparticles will increase the thermal resistance of the hot surface, worsening heat transfer. Therefore, after determining the optimal deposition time and deposition concentration and other parameters through appropriate experiments. When the actual deposition reaches this parameter, the nanofluid needs to be extracted and replaced with a conventional coolant. At this time, the nanoparticles deposited on the surface of the heat source can still enhance the pool boiling capacity. In the actual cooling stage, after the actual deposition of the nanoparticles reaches the set parameters, the nanofluid is extracted and replaced with a conventional coolant. At this time, the nanoparticles deposited on the surface of the heat source can still enhance the pool boiling capacity. The coolant distribution unit sends the low-boiling-point coolant into the immersion cooling cabinet through the coolant distribution pipeline. The specific cooling process is similar to the enhancement stage. The enhanced hot surface generates heat, causing the coolant in the immersion cooling cabinet to boil. The rising bubbles bring heat to the heat exchanger on the top of the immersion cooling cabinet. The cooling water distribution unit sends low-temperature cooling water to the top heat exchanger through the cooling water supply pipeline. The bubbles condense at the top heat exchanger and bring heat to the cooling water. The cooling water then flows into the side wall heat exchanger and is finally sent to the cooling water distribution unit through the cooling water return pipeline. The cooling water distribution unit brings heat to the external cooling unit through the cooling water heat exchange pipeline. The external cooling unit cools the return water and then sends it back to the cooling water distribution unit to complete the cycle.

[0009] Because nanoparticles are more likely to deposit on the boiling heat source surface, even under the boiling disturbance of the coolant, the nanoparticles on the enhanced wall surface may resuspend. However, most of the resuspended nanoparticles will redeposit on the heat source surface due to boiling, while a small portion will disperse in the coolant and the walls of the immersion cooling cabinet. Therefore, a single nanoparticle deposition enhancement usually ensures a long-term enhancement effect. The situation in which the increase of nanoparticle impurities in the coolant due to frequent enhancement is less likely to occur and affect the physical properties of the working fluid.

[0010] Furthermore, the heat source of the system is the heat generated by the computing process of the server. Multiple servers are integrated and immersed in the immersion cooling cabinet. The heat generated by the server is taken away through the side wall heat exchanger, and the final heat load is consumed by the external cooling unit.

[0011] Furthermore, the immersion cooling cabinet is provided with: servers, chips; the two-phase liquid cooling unit includes: a condenser, a heat exchanger, a cooling water distribution unit, a nanofluid distribution unit and a coolant distribution unit;

[0012] During the boiling enhancement stage, the coolant in the immersion cooling cabinet is drained by the coolant return pipe, the nanofluid supply pipe is opened, and the nanofluid is supplied. When the liquid level immerses the server to a certain height, the supply is stopped and the nanofluid supply pipe is closed. At this time, the server starts to work and generate heat. After the temperature reaches the saturation temperature of the nanofluid, it begins to boil, and the nanoparticles in the nanofluid are deposited on the boiling surface. At this time, the heat flux density of the chip is large and the boiling intensity is also large, so the nanoparticles tend to deposit on the chip surface, improving its heat dissipation capacity. Bubbles are generated through the boiling process, and the bubbles rise and take away the heat, and bring the heat to the condenser through the condensation process. The heat exchanger continuously introduces cooling water into the condenser to take away the condensation heat. Through the condenser heat exchange pipe and the boiling working medium, weak cooling in the boiling enhancement stage is achieved.

[0013] Furthermore, during the actual cooling stage, the nanofluid return pipeline is opened to extract the nanofluid in the immersion cooling cabinet, and then the nanofluid return pipeline is closed, the coolant supply pipeline is opened, and the coolant in the coolant distribution unit is sent into the immersion cooling cabinet. When the coolant immerses the server to a certain height, the pipeline is closed; at this time, the server starts to work and generate heat, and after the temperature reaches the saturation temperature of the coolant, it begins to boil; bubbles are generated through the boiling process, and the bubbles rise and take away the heat, and bring the heat to the condenser through the condensation process. The heat exchanger continuously introduces cooling water into the condenser to take away the condensation heat, thereby achieving enhanced cooling in the actual boiling stage.

[0014] Furthermore, the core idea for improving boiling heat transfer on the chip surface of vertical servers is to counteract the downward force of gravity while ensuring easy separation of the gas and liquid phases, thereby increasing the liquid phase replenishment capacity at the boiling surface. A layer of thermally conductive material is etched onto the chip surface to enhance heat transfer while also preventing direct contact between the chip and the working fluid, which could cause short circuits.

[0015] Furthermore, after etching the thermal conductive material on the chip surface, microgrooves are prepared on the surface of the thermal conductive material by laser etching, physical / chemical vapor deposition, etc., to enhance the capillary wicking ability of the surface of the thermal conductive material, thereby enhancing the liquid phase wetting ability and liquid replenishment ability of the boiling surface.

[0016] The chip itself has a certain boiling gradient. This is because the near-wall rise of the bubbles at the lower end of the chip will bring heat to the upper end of the chip, and there is a heat superposition process, that is, there is a strong boiling zone at the upper end of the chip and a weak boiling zone at the lower end. During the deposition of nanoparticles, nanoparticles tend to be deposited in the strong boiling zone. The more nanoparticles are deposited, the more bubble nucleation holes are formed. Therefore, the frequency of bubble detachment at the upper end of the chip can be significantly improved, and heat can be taken away faster. This also corresponds to the phenomenon that there are more bubbles in the strong boiling zone and it is more difficult for them to detach. The air film at the upper end is more difficult to form, which delays CHF. In the weak boiling zone at the lower end, since there are relatively few nanoparticles deposited, the liquid phase is easier to replenish. The liquid phase replenished from the lower end, under the action of the microgrooves, quickly infiltrates into the upper end surface, replenishes the upper end, and once again enhances CHF. HTC can also be enhanced due to the deposition of nanoparticles. Therefore, the heat dissipation capacity of the chip is enhanced.

[0017] Furthermore, because the thermally conductive material is in close contact with the chip surface and has a much higher thermal conductivity than the nanofluid, heat first accumulates on the thermally conductive material wall before being transferred to the nanofluid. Consequently, the wall heat is higher than the nanofluid in the microchannels. At this point, nanoparticles in the cold nanofluid preferentially deposit on the hot wall surface. This improves the wettability of the wall, and the working fluid is more inclined to "climb" the wall, thereby enhancing the capillary wicking ability of the boiling surface.

[0018] Furthermore, hydrophobic nanoparticles that have not been hydrophilically modified have a higher affinity with the gas phase, that is, during the bubble generation process, they tend to gather in a circle on the surface of the bubble rather than near the thermal conductive material. Since the server is arranged vertically at this moment, the influence of gravity may cause the nanoparticles to not fall vertically when the bubble rises and settles downward, but to produce a certain offset, which inevitably causes uneven deposition shape and deposition density; hydrophilic nanoparticles that have been hydrophilically modified tend to gather near the liquid microlayer due to the presence of a thin liquid microlayer underneath when the bubble is generated, and their deposition path becomes shorter. Therefore, compared with hydrophobic nanoparticles, the deposition of hydrophilic nanoparticles on the thermal conductive material is more regular and stable.

[0019] Applying the nanoparticle self-deposition method to the two-phase liquid cooling system of the data center can effectively enhance the surface wettability through the deposition of nanoparticles in the nanofluid on the boiling surface without changing the server layout in the cabinet, thereby improving the system's boiling heat transfer capacity, enhancing cooling efficiency, and greatly reducing system improvement costs.

[0020] The system's vertical nanoparticle deposition pattern can adaptively deposit nanoparticles according to the different boiling intensities in the height direction of the vertical server layout, forming a gradient wettability surface. It focuses on enhancing the wettability and roughness on the upper end of the server, thereby enhancing the capillary core extraction ability and bubble nucleation points. The lower end of the server serves as a liquid phase replenishment path to replenish the heat source surface, thereby enhancing the gas-liquid phase separation ability. The gradient wettability surface can also enhance the capillary core extraction ability in the height direction and enhance the liquid phase infiltration ability of the chip surface. The vertical deposition pattern can enhance the gas-liquid phase separation ability while improving the liquid phase replenishment and infiltration ability, thereby effectively improving HTC and CHF, and thus improving the efficiency of the cooling system.

[0021] For the vertical server layout, it is proposed to adhere micro-groove thermal conductive material to the chip surface to enhance the liquid phase's ability to infiltrate the thermal conductive material, thereby enhancing the fluid replenishment capacity and improving CHF. Nanoparticle self-deposition is combined with the micro-groove modified surface. Due to the boiling deposition mechanism of nanoparticles, they are more easily deposited on the micro-groove wall, further enhancing the capillary wicking and liquid infiltration capabilities, which is more suitable for the boiling heat exchange of vertical servers.

[0022] For vertical server configurations, a hydrophilic nanoparticle deposition method is proposed. Hydrophilic nanoparticles accumulate on the hot wall surface during boiling, while hydrophobic nanoparticles gather around bubbles. Because the direction of gravity differs from horizontal deposition, hydrophilic nanoparticle deposition is more regular and more accurately targeted, making it ideal for vertical server configurations.

[0023] The difference in surface boiling intensity caused by the difference in thermal conductivity of different materials is used to cause differences in the deposition of nanoparticles, thereby selectively enhancing the hydrophilicity and hydrophobicity of the boiling surface and thus enhancing the pool boiling effect.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) It can improve boiling capacity and reduce improvement costs through simple and low-cost nanoparticle self-assembly.

[0026] (2) It can prepare heterogeneous wettability surfaces based on its own boiling mechanism, effectively improving the energy utilization efficiency of the two-phase liquid cooling system;

[0027] (3) The strength of nanoparticle deposition can be controlled by differences in thermal conductive materials, thereby selectively enhancing the boiling surface, effectively improving the pool boiling effect, and thus improving the efficiency of the cooling system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of a two-phase liquid cooling system based on the boiling enhancement mechanism of nanoparticle deposition;

[0029] Figure 2 Schematic diagram of a two-phase liquid cooling unit based on the nanoparticle deposition boiling enhancement mechanism;

[0030] Figure 3 Schematic diagram of the boiling enhancement mechanism of inhomogeneous surface with nanoparticle deposition;

[0031] Figure 4 Schematic diagram of the nanoparticle deposition mechanism in the microgroove structure;

[0032] Figure 5 Schematic diagram of the deposition mechanism of hydrophilic and hydrophobic nanoparticles;

[0033] Figure 6 Schematic diagram of an example of hydrophilic modification of nanoparticles (hydroxyl-modified multi-walled carbon nanotubes);

[0034] Figure 7 Schematic diagram of the boiling enhancement mechanism of amphiphilic nano-enhanced surface;

[0035] Figure 8 Schematic diagram of a nanoparticle deposition-enhanced two-phase liquid cooling unit for a horizontal server arrangement;

[0036] Figure 9 for Figure 8 Schematic illustration of the nanoparticle deposition mechanism.

[0037] Figure 1: Immersion cooling cabinet; 2. Sidewall heat exchanger; 3. Cooling water distribution unit; 4. Nanofluid distribution unit; 5. Coolant distribution unit; 6. External cooling unit; 7. Cooling water supply line; 8. Condenser heat exchange line; 9. Cooling water return line; 10. Cabinet area; 11. Data center room; 12. Coolant distribution line; 13. Nanofluid distribution line; 14. Cooling water heat exchange line; 15. Server; 16. Chip; 17. Boiling fluid; 18. Condenser; 19. Heat exchanger; 20. Nanofluid supply line; 21. Nanofluid return line; 22. Coolant supply line; 23. Coolant return line; 24. Bubbles; 25. Boiling process; 26. Condensation process; 27. Conductor Thermal materials; 28. Microchannels; 29. ​​Heat superposition process; 30. Nanoparticles; 31. Nanoparticle deposition process; 32. Strong boiling zone; 33. Weak boiling zone; 34. Nanofluids; 30. Nanoparticles; 35. Hot wall; 36. Cold nanofluids; 37. Hydrophobic nanoparticles; 38. Hydrophilic nanoparticles; 39. Liquid microlayer; 40. Multi-walled carbon nanotubes; 41. Na2ZnO2-modified multi-walled carbon nanotubes; 42. Multi-walled carbon nanotubes after hydrolysis reaction; 43. Hydroxyl-modified multi-walled carbon nanotubes; 44. High thermal conductivity materials; 45. Low thermal conductivity materials; 46. Gas phase; 47. Liquid phase; 48. Strong particle deposition; 49. Weak particle deposition; 50. Boiling process; 51. Condensation process; 52. Nanoparticle deposition process. DETAILED DESCRIPTION

[0038] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Component models, material names, connection structures, control methods, algorithms, and other features not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0039] Example 1

[0040] This embodiment provides a two-phase liquid cooling system based on the nanoparticle deposition boiling enhancement mechanism. Figure 1 、 2 As shown, it includes: an external cooling unit 6, an immersion cooling cabinet 1, a cooling water distribution unit 3, a nanofluid distribution unit 4 and a coolant distribution unit 5; the immersion cooling cabinet 1, the nanofluid distribution unit 4 and the coolant distribution unit 5 are all arranged in a cabinet area 10; the data center room 11 is a multi-cabinet parallel connection;

[0041] The system includes two operating modes: a pre-cooling stage during which nanoparticles 30 self-deposit and enhance boiling, and an actual cooling stage. During the enhanced boiling stage, the nanofluid distribution pipeline 13 delivers the nanofluid 34 from the nanofluid distribution unit 4 into the immersion cooling cabinet 1. During this stage, while the cooling capacity of the nanofluid 34 is slightly weaker than that of a low-boiling-point coolant (such as electronic fluoride liquid), it still provides a certain cooling capacity. During this stage, the servers in the immersion cooling cabinet 1 are operating normally. When the servers 15 generate heat, the nanofluid 34 reaches saturation and begins to boil. At this point, the highly thermally conductive nanoparticles 30 in the nanofluid 34 naturally deposit on the boiling surface. The deposition of nanoparticles 30 on the boiling surface increases the nucleation sites for bubbles and enhances the thermal conductivity of the hot surface. This reduces the bubble detachment diameter and increases the frequency of bubble detachment, enhancing the pool boiling efficiency, and therefore the cooling efficiency of the immersion cooling system. The rising bubbles bring heat to the heat exchanger 19 on the top of the immersion cooling cabinet 1. The cooling water distribution unit 3 sends the low-temperature cooling water to the top heat exchanger 19 through the cooling water supply pipe 7. The bubbles condense at the top heat exchanger 19, bringing heat to the cooling water. The cooling water then flows into the side wall heat exchanger 2 (the purpose of the side wall heat exchanger 2 here is to facilitate cooling water integration, and it can also take away a small amount of heat from the side wall of the immersion cooling cabinet 1). Finally, it is sent to the cooling water distribution unit 3 through the cooling water return pipe 9. The cooling water distribution unit 3 brings heat to the external cooling unit 6 through the cooling water heat exchange pipe 14. The external cooling unit 6 cools the return water and then sends it back to the cooling water distribution unit 3 to complete the cycle.

[0042] However, during the boiling enhancement stage, since the cooling capacity of the nanofluid 34 is lower than that of the traditional boiling coolant, and as the nanoparticles 30 are deposited on the surface of the heat source for a long time, the bubble nucleation holes will be blocked, and an overly thick layer of nanoparticles 30 will also increase the thermal resistance of the hot surface, worsening heat transfer. Therefore, after determining the optimal deposition time and deposition concentration and other parameters through appropriate experiments. When the actual deposition reaches this parameter, the nanofluid 34 needs to be extracted and replaced with a conventional coolant. At this time, the nanoparticles 30 deposited on the surface of the heat source can still have an enhanced effect on the pool boiling capacity. In the actual cooling stage, after the actual deposition of the nanoparticles 30 reaches the set parameters, the nanofluid 34 is extracted and replaced with a conventional coolant. At this time, the nanoparticles 30 deposited on the surface of the heat source can still have an enhanced effect on the pool boiling capacity; the coolant distribution unit 5 sends the low-boiling-point coolant into the immersion cooling cabinet 1 through the coolant distribution pipeline 12. The specific cooling process is similar to the enhancement stage. The enhanced hot surface generates heat, causing the coolant in the immersion cooling cabinet 1 to boil. The rising bubbles bring heat to the heat exchanger 19 on the top of the immersion cooling cabinet 1. The cooling water distribution unit 3 sends low-temperature cooling water to the top heat exchanger 19 through the cooling water supply pipe 7. The bubbles condense at the top heat exchanger 19, bringing heat to the cooling water. The cooling water then flows into the side wall heat exchanger 2 and is finally sent to the cooling water distribution unit 3 through the cooling water return pipe 9. The cooling water distribution unit 3 brings heat to the external cooling unit 6 through the cooling water heat exchange pipe 14. The external cooling unit 6 cools the return water and then sends it back to the cooling water distribution unit 3 to complete the cycle.

[0043] Since nanoparticles 30 are more likely to deposit on the boiling heat source surface, even under the boiling disturbance of the coolant, the nanoparticles 30 on the reinforced wall surface may re-suspend. However, most of the re-suspended nanoparticles 30 will be redeposited on the heat source surface due to the boiling, while a small portion will be dispersed in the coolant and on the walls of the immersion cooling cabinet 1. Therefore, a single deposition enhancement of nanoparticles 30 generally ensures a long-term enhancement effect. Frequent enhancements, which may cause an increase in nanoparticle 30 impurities in the coolant and affect the physical properties of the working fluid, are less likely to occur.

[0044] In a specific embodiment, the heat source of the system is the heat generated by the computing process of the server 15. Multiple servers 15 are integrated and immersed in the immersion cooling cabinet 1. The heat generated by the server 15 is taken away by the side wall heat exchanger 2, and the final heat load is consumed by the external cooling unit 6.

[0045] In a specific embodiment, the immersion cooling cabinet 1 is provided with: a server 15, a chip 16; a two-phase liquid cooling unit includes: a condenser 18, a heat exchanger 19, a cooling water distribution unit 3, a nanofluid distribution unit 4 and a coolant distribution unit 5;

[0046] During the boiling enhancement stage, the coolant in the immersion cooling cabinet 1 is drained by the coolant return line 23, the nanofluid supply line 20 is opened, and the nanofluid 34 is supplied. When the liquid level submerges the server 15 to a certain height, the supply is stopped and the nanofluid supply line 20 is closed. At this time, the server 15 starts to work and generates heat. After the temperature reaches the saturation temperature of the nanofluid 34, it begins to boil, and the nanoparticles in the nanofluid 34 are deposited on the boiling surface. At this time, the heat flux density of the chip 16 is large and the boiling intensity is also large. Therefore, the nanoparticles are more inclined to deposit on the surface of the chip 16, improving its heat dissipation capacity. Bubbles 24 are generated through the boiling process 25, and the bubbles 24 rise and take away heat, and bring the heat to the condenser 18 through the condensation process 26. The heat exchanger 19 continuously introduces cooling water into the condenser 18 to take away the condensation heat. Through the condenser heat exchange line 8 and the boiling working medium 17, weak cooling in the boiling enhancement stage is achieved.

[0047] In a specific embodiment, during the actual cooling stage, the nanofluid return line 21 is opened to extract the nanofluid 34 in the immersion cooling cabinet 1, and then the nanofluid return line 21 is closed, the coolant supply line 22 is opened, and the coolant in the coolant distribution unit 5 is sent into the immersion cooling cabinet 1. When the coolant immerses the server 15 to a certain height, the line is closed; at this time, the server 15 starts to work and generates heat, and after the temperature reaches the coolant saturation temperature, it begins to boil; bubbles 24 are generated through the boiling process 25, and the bubbles 24 rise and take away heat, and bring the heat to the condenser 18 through the condensation process 26. The heat exchanger 19 continuously introduces cooling water into the condenser 18 to take away the condensation heat, thereby achieving enhanced cooling in the actual boiling stage.

[0048] In this specific embodiment, the core strategy for enhancing boiling heat transfer on the chip surface of a vertical server is to counteract the downward force of gravity while ensuring easy separation of the gas and liquid phases, thereby increasing the liquid phase replenishment capacity of the boiling surface. A layer of thermally conductive material 27 is etched onto the surface of the chip 16 to enhance heat transfer while also preventing direct contact between the chip 16 and the working fluid, which could cause a short circuit.

[0049] In a specific embodiment, after the thermal conductive material 27 is etched on the surface of the chip 16, micro grooves 28 are prepared on the surface of the thermal conductive material 27 by laser etching, physical / chemical vapor deposition, etc., to enhance the capillary wicking ability of the surface of the thermal conductive material 27, thereby enhancing the liquid phase wetting ability and liquid replenishment ability of the boiling surface.

[0050] like Figure 3As shown, the chip 16 itself has a certain boiling gradient. This is because the near-wall rise of bubbles at the lower end of the chip 16 brings heat to the upper end of the chip 16, resulting in a heat superposition process 29. That is, there is a strong boiling zone 32 at the upper end of the chip 16 and a weak boiling zone 33 at the lower end. During the nanoparticle deposition process 31, the nanoparticles 30 tend to deposit in the strong boiling zone 32. The more nanoparticles 30 are deposited, the more bubble nucleation holes are formed. Therefore, the frequency of bubble detachment at the upper end of the chip 16 can be significantly increased, and heat can be carried away more quickly. This also corresponds to the phenomenon that the strong boiling zone 32 has more bubbles and is more difficult to detach, making it more difficult for the upper end air film to form, thereby delaying CHF. In the weak boiling zone 33 at the lower end, due to the relatively small amount of nanoparticles 30 deposited, the liquid phase is easier to replenish. The liquid phase replenished from the lower end, under the action of the microgrooves 28, quickly infiltrates the upper end surface, replenishing the upper end and further enhancing CHF. HTC can also be enhanced due to the deposition of nanoparticles 30. Therefore, the heat dissipation capability of the chip 16 is enhanced.

[0051] like Figure 4 As shown, in this embodiment, because the thermally conductive material 27 is in close contact with the chip surface and has a much higher thermal conductivity than the nanofluid 34, heat first accumulates on the wall of the thermally conductive material 27 and then transfers to the nanofluid 34. As a result, the wall heat is higher than the nanofluid 34 in the microchannel 28. At this time, the nanoparticles 30 in the cold nanofluid 36 are preferentially deposited on the hot wall 35. As a result, the wettability of the wall is improved, and the working fluid is more inclined to "climb" the wall, thereby improving the capillary wicking ability of the boiling surface.

[0052] like Figure 5 As shown, in a specific embodiment, the hydrophobic nanoparticles 37 that have not been hydrophilically modified have a higher affinity with the gas phase, that is, during the generation of the bubbles 24, they tend to gather in a circle on the surface of the bubbles 24 rather than near the thermal conductive material 5. Since the server is arranged vertically at this moment, the influence of gravity may cause the nanoparticles to not fall vertically while the bubbles rise and settle downward, but to produce a certain offset, which inevitably causes uneven deposition shape and deposition density; the hydrophilic nanoparticles 38 that have been hydrophilically modified tend to gather near the liquid microlayer 39 due to the presence of a thin liquid microlayer 39 below when the bubbles are generated, and their deposition distance becomes shorter. Therefore, compared with the hydrophobic nanoparticles 37, the deposition of the hydrophilic nanoparticles 38 on the thermal conductive material 27 is more regular and stable.

[0053] like Figure 6 As shown, in a specific embodiment, when the nanoparticles 30 are multi-walled carbon nanotubes 40, since they have a porous long chain structure, they can increase the nucleation holes of bubbles and heat transfer, thereby improving the pool boiling effect.

[0054] Under the action of Na2ZnO2, the multi-walled carbon nanotubes 40 generate Na2ZnO2-modified multi-walled carbon nanotubes 41, and undergo two-step hydrolysis reaction to form hydrolyzed multi-walled carbon nanotubes 42, and finally form hydroxyl-modified multi-walled carbon nanotubes 43.

[0055] Figure 7 This is a biphilic nano-enhanced surface boiling enhancement mechanism. A high thermal conductivity material 44 is coated on one end of the chip 16 surface, and a low thermal conductivity material 45 is coated on the other end. Because the boiling intensities of bubbles 24 on surfaces of different thermally conductive materials vary, the deposition strength of nanoparticles 30 also varies. More nanoparticles 30 are deposited on the high thermally conductive material 44, enhancing bubble detachment and allowing the gas phase 46 to rise more easily from this location. Fewer nanoparticles 30 are deposited on the low thermally conductive material 45, making it easier for the liquid phase 47 to replenish from this location. This gradient deposition of nanoparticles 30 by different thermally conductive materials enhances surface wettability differences by controlling the thermal conductivity of the materials, thereby strengthening the heat dissipation capacity of the vertical server and improving the cooling capacity of the two-phase immersion cooling system.

[0056] Figure 8 This is a two-phase liquid cooling unit based on nanoparticle deposition enhancement for horizontal server layouts. Since horizontal server layouts are still the norm in most data centers, this embodiment proposes a nanoparticle deposition optimization method for horizontal heat sources. An immersion cooling cabinet 1 houses servers 15 and chips 16. The two-phase liquid cooling unit includes a condenser 18, a heat exchanger 19, a cooling water distribution unit 3, a nanofluid distribution unit 4, and a coolant distribution unit 5.

[0057] In a horizontal server layout, server 15 needs to be shortened to prevent bubbles from accumulating on the backplane of server 15 and to enhance the gas phase's upward path. Therefore, server 15 is designed in two stages. During the boiling enhancement phase, the coolant in immersion cooling cabinet 1 is drained via coolant return line 23. Nanofluid supply line 20 is opened, and nanofluid 34 is supplied. When the liquid level submerges server 15 to a certain height, the supply is stopped, and nanofluid supply line 20 is closed. At this point, server 15 begins operating and generating heat. When the temperature reaches the saturation temperature of nanofluid 34, boiling begins. Nanoparticles in nanofluid 34 are deposited on the boiling surface. At this point, the heat flux density and boiling intensity of chip 16 are high, so nanoparticles are more likely to deposit on the chip 16 surface, improving its heat dissipation capacity. The boiling process 25 generates bubbles 24, which rise and remove heat. These bubbles 24 then carry heat to condenser 18 through condensation 26. Heat exchanger 19 continuously flows cooling water into condenser 18 to remove the condensation heat, achieving weak cooling during the boiling enhancement phase.

[0058] During the actual cooling phase, nanofluid return line 21 is opened to extract nanofluid 34 from immersion cooling cabinet 1. Nanofluid return line 21 is then closed, and coolant supply line 22 is opened, sending coolant from coolant distribution unit 5 into immersion cooling cabinet 1. Once the coolant has submerged servers 15 to a certain height, the line is closed. At this point, servers 15 begin operating and generating heat. Once the temperature reaches the coolant's saturation temperature, boiling begins. Bubbles 24 are generated by the boiling process 25, rising and removing heat. These bubbles are then transferred to condenser 18 through condensation 26. Heat exchanger 19 continuously pumps cooling water into condenser 18 to remove the condensation heat, achieving enhanced cooling during the actual boiling phase.

[0059] Figure 9 This is a nanoparticle deposition mechanism. A high-thermal-conductivity material 27 is coated on the surface of the chip 1. A microchannel structure based on a low-thermal-conductivity material 45 is deposited above the high-thermal-conductivity material 27 via physical / chemical deposition methods. The boiling gas and liquid phases, triggered by a horizontal heat source, mix more evenly, blocking the ascending path of the gas phase and the replenishing path of the liquid phase. By designing the surface of the differentially thermally conductive materials, the gas and liquid phases are separated. Heat preferentially accumulates in the higher-temperature high-thermal-conductivity material 27, where the gas phase 46 also rises. The low-thermal-conductivity material 45 replenishes the liquid phase 47, which is then transported to the high-thermal-conductivity area for liquid replenishment. The proposed nanoparticle deposition enhancement mechanism is that nanoparticles 30 also tend to deposit near the high-thermal-conductivity material 27, further enhancing its bubble nucleation and detachment capabilities. In areas with less low-thermal-conductivity material 45, due to the lower particle density, the enhanced wettability is greater than the enhanced bubble nucleation capability, thus enhancing liquid replenishment there. This improves the two-phase immersion cooling capabilities of horizontal server arrangements and enhances system cooling efficiency.

[0060] Components not described in detail in this embodiment are all existing components that can be purchased through public channels.

[0061] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A two-phase liquid cooling system based on nanoparticle deposition boiling enhancement mechanism, characterized in that: include: An external cooling unit (6), an immersion cooling cabinet (1), a cooling water distribution unit (3), a nanofluid distribution unit (4), and a coolant distribution unit (5); the immersion cooling cabinet (1), the nanofluid distribution unit (4), and the coolant distribution unit (5) are all arranged in a cabinet area (10); the data center room (11) is a multi-cabinet parallel connection; The system includes two operating modes: the self-deposition boiling enhancement stage of nanoparticles (30) before cooling and the actual cooling stage; in the boiling enhancement stage, the nanofluid distribution pipeline (13) sends the nanofluid (34) in the nanofluid distribution unit (4) into the immersion cooling cabinet (1), and when the server (15) generates heat, the nanofluid (34) reaches the saturation point and begins to boil, and the bubbles rise and bring heat to the heat exchanger (19) on the top of the immersion cooling cabinet (1), and the cooling water distribution unit (3) transfers the low temperature to the heat exchanger (19). The cooling water is fed into the top heat exchanger (19) through the cooling water supply pipe (7). The bubbles condense at the top heat exchanger (19), transferring heat to the cooling water. The cooling water then flows into the side wall heat exchanger (2) and is finally fed into the cooling water distribution unit (3) through the cooling water return pipe (9). The cooling water distribution unit (3) transfers heat to the external cooling unit (6) through the cooling water heat exchange pipe (14). The external cooling unit (6) cools the return water and then feeds it back into the cooling water distribution unit (3) to complete the cycle. In the actual cooling stage, after the actual deposition of the nanoparticles (30) reaches the set parameters, the nanofluid (34) is extracted and replaced with a conventional coolant. At this time, the nanoparticles (30) deposited on the surface of the heat source can still enhance the pool boiling capacity; the coolant distribution unit (5) sends the low-boiling-point coolant into the immersion cooling cabinet (1) through the coolant distribution pipeline (12). The enhanced hot surface generates heat, causing the coolant in the immersion cooling cabinet (1) to boil, and the rising bubbles bring heat to the heat exchanger ( 19), the cooling water distribution unit (3) sends the low-temperature cooling water to the top heat exchanger (19) through the cooling water supply pipe (7), and the bubbles condense at the top heat exchanger (19), bringing heat to the cooling water, and the cooling water then flows into the side wall heat exchanger (2), and finally sent to the cooling water distribution unit (3) through the cooling water return pipe (9). The cooling water distribution unit (3) brings heat to the external cooling unit (6) through the cooling water heat exchange pipe (14), and the external cooling unit (6) cools the return water and sends it back to the cooling water distribution unit (3) to complete the cycle; The immersion cooling cabinet (1) is provided with: a server (15) and a chip (16); after etching a heat-conducting material (27) on the surface of the chip (16), micro-grooves (28) are prepared on the surface of the heat-conducting material (27) to enhance the capillary wicking ability of the surface of the heat-conducting material (27) so as to enhance the liquid phase wetting ability and liquid replenishing ability of the boiling surface; The hydrophilic nanoparticles (38) that have been hydrophilically modified tend to gather near the liquid microlayer (39) due to the presence of a thin liquid microlayer (39) underneath when bubbles are generated, and their deposition distance becomes shorter. Therefore, compared with the hydrophobic nanoparticles (37), the deposition of the hydrophilic nanoparticles (38) on the thermal conductive material (27) is more regular and stable.

2. The two-phase liquid cooling system based on nanoparticle deposition boiling enhancement mechanism according to claim 1, characterized in that: The heat source of the system is the heat generated by the computing process of the server (15). Multiple servers (15) are integrated and immersed in the immersion cooling cabinet (1). The heat generated by the server (15) is taken away through the side wall heat exchanger (2), and the final heat load is consumed by the external cooling unit (6).

3. The two-phase liquid cooling system based on nanoparticle deposition boiling enhancement mechanism according to claim 1, characterized in that: The two-phase liquid cooling unit includes: a condenser (18), a heat exchanger (19), a cooling water distribution unit (3), a nanofluid distribution unit (4) and a coolant distribution unit (5); During the boiling enhancement stage, the coolant in the immersion cooling cabinet (1) is drained by the coolant return line (23), the nanofluid supply line (20) is opened, and the nanofluid (34) is supplied. When the liquid level submerges the server (15) to a certain height, the supply is stopped and the nanofluid supply line (20) is closed. At this time, the server (15) starts to work and generates heat. After the temperature reaches the saturation temperature of the nanofluid (34), it starts to boil, and the nanoparticles in the nanofluid (34) are deposited on the boiling surface. Bubbles (24) are generated through the boiling process (25), and the bubbles (24) rise and take away the heat, and bring the heat to the condenser (18) through the condensation process (26). The heat exchanger (19) continuously introduces cooling water into the condenser (18) to take away the condensation heat, thereby achieving weak cooling during the boiling enhancement stage.

4. The two-phase liquid cooling system based on nanoparticle deposition boiling enhancement mechanism according to claim 3, characterized in that: During the actual cooling stage, the nanofluid return line (21) is opened to extract the nanofluid (34) in the immersion cooling cabinet (1), and then the nanofluid return line (21) is closed, the coolant supply line (22) is opened, and the coolant in the coolant distribution unit (5) is sent into the immersion cooling cabinet (1). When the coolant immerses the server (15) to a certain height, the line is closed; at this time, the server (15) starts to work and generates heat, and after the temperature reaches the saturation temperature of the coolant, it starts to boil; bubbles (24) are generated through the boiling process (25), and the bubbles (24) rise and take away the heat, and bring the heat to the condenser (18) through the condensation process (26), and the heat exchanger (19) continuously introduces cooling water into the condenser (18) to take away the condensation heat, thereby achieving enhanced cooling in the actual boiling stage.

5. The two-phase liquid cooling system based on nanoparticle deposition boiling enhancement mechanism according to claim 3, characterized in that: A layer of heat-conducting material (27) is etched on the surface of the chip (16) to enhance heat exchange and prevent the chip (16) from directly contacting the working medium and causing a short circuit.

6. The two-phase liquid cooling system based on nanoparticle deposition boiling enhancement mechanism according to claim 1, characterized in that: Heat first accumulates on the wall of the heat-conducting material (27) and then transfers to the nanofluid (34). Therefore, the heat of the wall is higher than that of the nanofluid (34) in the microchannel (28). At this time, the nanoparticles (30) in the cold nanofluid (36) are preferentially deposited on the hot wall (35).

7. The two-phase liquid cooling system based on nanoparticle deposition boiling enhancement mechanism according to claim 1, characterized in that: When the nanoparticles (30) are multi-walled carbon nanotubes (40), since they have a porous long-chain structure, they can increase the nucleation holes of bubbles and heat transfer, thereby improving the pool boiling effect.

8. The two-phase liquid cooling system based on nanoparticle deposition boiling enhancement mechanism according to claim 7, characterized in that: The multi-walled carbon nanotubes (40) are subjected to the action of Na2ZnO2 to generate Na2ZnO2-modified multi-walled carbon nanotubes (41), which undergo a two-step hydrolysis reaction to form hydrolysis-reaction multi-walled carbon nanotubes (42), and finally form hydroxyl-modified multi-walled carbon nanotubes (43).

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