A single-phase coolant for immersion cooling thermal management, preparation method and application

Abstract

The present invention belongs to the field of immersion liquid cooling technology, and in particular relates to a single-phase coolant for immersion cooling thermal management, a preparation method, and a corresponding single-phase immersion cooling system. A single-phase coolant having a kinematic viscosity of less than 10 mm at 100°C. 2 / s, the main component of the single-phase coolant is one or more mixed liquid polyolefins; characterized in that the liquid polyolefin includes at least one low-viscosity liquid polyolefin, the low-viscosity liquid polyolefin is a metallocene polyolefin or a conventional polyolefin, prepared by a metallocene-based or non-metallocene catalyst system, and the kinematic viscosity of the low-viscosity liquid polyolefin is less than 10 mm at 100°C 2 By using such liquid polyolefin as the main component of the immersion single-phase coolant, an immersion single-phase coolant with high thermal conductivity and high specific heat capacity can be obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of immersion liquid cooling, and in particular relates to a single-phase coolant for immersion cooling thermal management, a preparation method and a corresponding single-phase immersion cooling system. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] With the increasing performance and integration of computing devices, and particularly with the advancement of the internet and 5G technologies, the rapid development of data centers across various industries has placed higher demands on the cooling of high-heat-density electronic devices. Heat transfer typically occurs through convection, conduction, and radiation, with radiation being the least efficient. Traditional cooling methods used in data center computer systems, such as water cooling and air cooling, suffer from high energy consumption and struggle to meet the cooling needs of emerging high-heat-density electronic devices. According to statistics, approximately 40% of data center energy consumption comes from air cooling equipment, and data center carbon emissions are greater than those of the aviation industry. Therefore, traditional cooling methods are unable to meet the cooling needs of emerging high-heat-density electronic devices in data centers, necessitating the urgent need to find new cooling methods that can reduce energy consumption and carbon emissions associated with data center cooling.

[0004] Compared to the thermal conductivity of air, the thermal conductivity of liquid is much greater. Heat can be quickly removed by liquid conduction, so using liquid cooling instead of air cooling can save costs, reduce energy consumption and carbon emissions. Liquid cooling technology can be divided into two categories: direct and indirect, depending on whether the heat source is in contact with the liquid. In common direct liquid cooling systems, computing equipment or electronic devices that need to dissipate heat are immersed in liquid and dissipate heat through direct contact with the coolant, so it is also called immersion liquid cooling, and the liquid that serves as the heat transfer medium is also called "coolant."

[0005] Among them, the advantages of immersion liquid cooling technology are mainly reflected in:

[0006] 1) Higher energy utilization rate. Immersion liquid cooling uses coolant as a heat transfer medium. Liquid has higher thermal conductivity and specific heat capacity, so it can conduct heat faster and absorb heat more effectively.

[0007] 2) Higher power density: Immersion liquid cooling can significantly increase server density per unit space in data centers, better supporting high-density computing. Traditional data centers use air cooling systems, which typically cool racks with a power density of 10kW-15kW. Immersion liquid cooling can increase the power density of a single rack to 100kW or even over 200kW, thus meeting the heat dissipation requirements of high-density computing scenarios.

[0008] 3) Higher equipment reliability. Immersion liquid cooling ensures that heat-generating equipment always operates at an optimal temperature. The immersion environment effectively prevents the adverse effects of water vapor, dust, and other pollutants on the equipment. Furthermore, since fans are no longer required in servers and computer rooms, noise and vibration issues are effectively addressed.

[0009] 4) Higher space utilization. The excellent heat dissipation performance of immersion liquid cooling allows servers to be arranged closely without spacing. At the same time, no fans are required, and there is no need for air conditioning and refrigeration units in the computer room. There is no need to install cold and hot aisle enclosure facilities, and no raised floors are required. Therefore, immersion liquid cooling has higher space utilization than traditional cooling solutions.

[0010] 5) More water-efficient. Traditional air cooling technology typically requires a large amount of water for evaporative cooling. Immersion liquid cooling technology can operate at a coolant temperature of 45°C while still achieving effective natural cooling, thereby reducing the need for active heat removal equipment and thus saving more water.

[0011] Given these advantages, immersion liquid cooling technology has become a current research hotspot. Immersion liquid cooling involves directly immersing the computing equipment or electronic components that require heat dissipation in a coolant, allowing the coolant to absorb the heat generated by the equipment. Depending on whether the coolant undergoes a phase change during the heat dissipation cycle, it can be categorized as single-phase or two-phase immersion liquid cooling.

[0012] Two-phase immersion liquid cooling involves immersing electronic devices in a closed tank filled with a two-phase coolant with a boiling point lower than the operating temperature. When the computing device or electronic device requiring heat dissipation heats up to the boiling point of the two-phase coolant, the coolant turns into a vapor, minus the heat. The vapor then condenses on a lid or coil condenser placed above the coolant and settles back into the coolant, continuously circulating the coolant to cool the computing device or electronic device.

[0013] Compared with two-phase immersion liquid cooling where the coolant absorbs heat and undergoes phase change, single-phase immersion coolant can achieve heat dissipation for computing equipment or electronic devices without phase change. At the same time, the corresponding equipment structure is simpler and does not require condensers or other devices.

[0014] The advantages of single-phase immersion liquid cooling over two-phase immersion liquid cooling are reflected in two aspects. First, the coolant is relatively cheaper, and the corresponding cooling equipment structure is simpler and easier to maintain, which helps to reduce overall costs. Second, the coolant has no phase change, so there is no need to worry about the health risks of coolant evaporation and overflow leading to inhalation by people.

[0015] At present, the most widely used coolants such as liquid ammonia and ethylene glycol cannot be used for immersion cooling due to their toxicity. The coolants commonly used for single-phase immersion liquid cooling are fluorinated liquids. The chemical structures of fluorinated liquids include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HFCs), (per)fluorinated polyethers (PFPEs), etc. Commercial products such as Solvay's Heat Transfer Fluid, and 3M's Fluorinert TM Fluorinated coolants such as FC-40, FC-70, FC-72, and FC-770 offer advantages in terms of inertness, stability, and excellent cooling and heat dissipation. However, these coolants also have significant drawbacks. Fluorocarbons are potent greenhouse gases, contributing to global warming, and are difficult to biodegrade, making them difficult to achieve environmental sustainability and climate friendliness. Fluorocarbons also have a significantly higher density than hydrocarbons, resulting in a greater weight per volume. When used in computing equipment such as data centers, this significantly increases the load on the floor, requiring higher circulating power from the equipment's fluid pumps.

[0016] To address the global warming issue caused by fluorinated coolants, 3M's US 5713211, Dupont's US 20070187639, and Solvay's WO 2007099055 and WO 2010034698 have proposed fluorinated ethers with lower GWP (global warming potential). However, these fluorinated ethers still have the disadvantages of high density, high toxicity, and difficulty in environmentally friendly disposal and biodegradation. Summary of the Invention

[0017] The inventors have discovered that existing single-phase immersion coolants typically use chlorofluorocarbons, hydrochlorofluorocarbons, (per)fluorinated polyethers, and the like. While these have good heat dissipation performance, they also suffer from drawbacks such as high toxicity, a tendency to contribute to the greenhouse effect, and difficulty in environmentally friendly disposal. To overcome these drawbacks, the present invention proposes an environmentally friendly single-phase coolant with enhanced performance, free of halogens such as fluorine and sulfur, non-toxic and non-corrosive, low density, low greenhouse effect, and readily biodegradable, as well as a single-phase immersion cooling system compatible with this coolant.

[0018] The present invention provides a single-phase coolant with a synthetic hydrocarbon as its primary component. Typically, the synthetic hydrocarbon is a liquid polyolefin, such as conventional poly-alpha-olefin (PAO) or metallocene poly-alpha-olefin (mPAO). By using such a liquid polyolefin as the primary component of an immersion single-phase coolant, an immersion single-phase coolant with high thermal conductivity and high specific heat capacity can be obtained. Liquid polyolefins of different viscosities can also be mixed to further improve the heat transfer and dielectric properties of the single-phase coolant. The mixed high- and low-viscosity liquid polyolefin coolant exhibits excellent heat transfer under various flow regimes, including laminar, transitional, and turbulent, as well as under conditions of direct heat exchange in cooling tanks and indirect heat exchange within pipes. Furthermore, the liquid polyolefin coolant contains no halogens such as fluorine or sulfur, is non-toxic and non-corrosive, and has no impact on global warming, offering the advantages of sustainable environmental protection and climate friendliness. Its lower density reduces equipment weight, making it suitable for long-term immersion cooling of equipment such as data centers, IT equipment, and semiconductor devices.

[0019] In order to achieve the above technical objectives, the technical solutions adopted by the present invention are as follows:

[0020] In the first aspect, the present invention provides a single-phase coolant having a kinematic viscosity of less than 10 mm at 100°C. 2 / s, the main component of the single-phase coolant is one or more mixed liquid polyolefins; the liquid polyolefin includes at least one low-viscosity liquid polyolefin, and the kinematic viscosity of the low-viscosity liquid polyolefin is less than 10mm at 100°C. 2 / s. Preferably, the kinematic viscosity of the low-viscosity liquid polyolefin is 0.5-5.0 mm at 100°C. 2 / s; further preferably, 0.5-3.5mm 2 / s; further preferably, 0.5-2.5mm 2 / s.

[0021] Furthermore, the kinematic viscosity of the low viscosity liquid polyolefin is 2.0-10.0 mm at 40°C. 2 / s; preferably, 2.0-9.0mm 2 / s; further preferably, 2.0-6.0 mm 2 / s.

[0022] The liquid polyolefin accounts for at least 98% of the mass fraction of the entire single-phase coolant. Preferably, the liquid polyolefin accounts for 99-100% of the mass fraction of the entire single-phase coolant.

[0023] The low-viscosity liquid polyolefin is a metallocene polyolefin or a conventional polyolefin. The liquid polyolefin prepared by using a metallocene-based catalyst system is called a metallocene polyolefin, and the liquid polyolefin prepared by using a traditional non-metallocene-based catalyst (e.g., Lewis acid, supported Ziegler-Natta catalyst, etc.) is called a conventional polyolefin.

[0024] Furthermore, the liquid polyolefin is obtained by polymerizing ethylene, propylene, or a substituted olefin having a carbon number of 4 to 20 (C4-C20) using a metallocene or non-metallocene catalyst to obtain an unsaturated metallocene polyolefin. The unsaturated polyolefin is separated and then hydrogenated to obtain a final low-viscosity liquid polyolefin. The unseparated polyolefin is a high-viscosity liquid polyolefin. Methods for separating the unsaturated polyolefin include distillation and other separation methods commonly used in the art.

[0025] The substituted olefin includes one or a mixture of α-olefin, vinylidene olefin, disubstituted vinylidene olefin, trisubstituted vinylidene olefin.

[0026] The structures of the α-olefin (I), vinylidene olefin (II), disubstituted vinylidene olefin (III, IV) and trisubstituted vinylidene olefin (V) are shown below. The R1 includes a linear or branched alkane with a carbon number of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, and the sum of the carbon numbers of R2 and R3 is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18. , 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 straight chain or branched alkanes, R2, R3 and R4 include straight chain or branched alkanes whose sum of carbon numbers is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, wherein the carbon numbers of R1, R2, R3 and R4 may be the same or different.

[0027] Preferably, the raw material for preparing the liquid polyolefin is C5-C13 α-olefin, and further preferably, the raw material for preparing the liquid polyolefin is C5-C13 linear α-olefin.

[0028]

[0029] Low-viscosity liquid polyolefins have better heat transfer performance than hydrocarbon base oils with similar carbon numbers and kinematic viscosities. The single-phase coolant with low-viscosity liquid polyolefins as the main component applied to the single-phase immersion cooling system of the present invention can obtain a higher convective heat transfer coefficient under different fluid flow states and heat exchange conditions, indicating that low-viscosity liquid polyolefins are more suitable for immersion cooling of heat dissipation devices than conventional hydrocarbon base oils.

[0030] The inventors also found that adding high-viscosity liquid polyolefin as the main component of the single-phase coolant to the above-mentioned low-viscosity liquid polyolefin can also improve the heat transfer effect and dielectric properties of the coolant. The kinematic viscosity of the low-viscosity liquid polyolefin is less than 10 mm at 100°C. 2 / s, 2.0-10.0mm at 40℃ 2 / s, the kinematic viscosity of the high-viscosity liquid polyolefin is 10-1000mm at 100°C 2 / s, the viscosity index is not less than 150, preferably, the kinematic viscosity of the high viscosity liquid polyolefin is 10-100mm at 100°C 2 / s.

[0031] Furthermore, the high-viscosity liquid polyolefin is a metallocene polyolefin or a non-metallocene polyolefin. Preferably, the high-viscosity liquid polyolefin is a metallocene polyolefin. Further preferably, the high-viscosity liquid polyolefin is a highly isotactic comb-structured metallocene polyolefin.

[0032] Generally speaking, conventional polyolefins polymerized using traditional non-metallocene catalysts are atactic, with the side chains of the polyolefin molecules arranged randomly on the main chain with no fixed pattern. However, the use of C2-symmetric bridged metallocene catalysts or C1-symmetric bridged metallocene catalysts with large steric groups on one side can produce highly isotactic comb-structured metallocene polyolefins, where the side chains of the polyolefin molecules are arranged unilaterally on the main chain like a comb. Prior art has disclosed the special properties of such highly isotactic comb-structured polymers, such as superior mechanical properties, heat resistance, and solvent tolerance, and they have higher practical application value than random polymers. Through testing and simulation calculations, the present invention has found that the single-phase coolant prepared by adding the comb-structured metallocene polyolefin described above to a low-viscosity liquid polyolefin has a higher thermal conductivity and Mo value. When applied to a single-phase immersion cooling system, it exhibits a higher convective heat transfer coefficient under different flow conditions and under conditions of direct heat exchange in the cooling tank or indirect heat exchange in the tube.

[0033] The kinematic viscosity of liquid polyolefins varies depending on their molecular weight and degree of polymerization. During the preparation of liquid polyolefins, a series of liquid polyolefin products with different molecular weights and viscosities can usually be obtained simultaneously. High-viscosity liquid polyolefins are usually used as lubricating oils. The present invention uses them as additives with reduced usage, which can significantly improve the heat transfer effect and dielectric properties of the coolant. Specifically, after adding high-viscosity liquid polyolefins, the thermal conductivity, volume resistivity, and breakdown voltage of the coolant are all improved to varying degrees. The combination of high- and low-viscosity liquid polyolefins can also effectively utilize polyolefin products of different viscosities.

[0034] The high-viscosity liquid polyolefin accounts for 1.0-10.0% of the mass fraction of the entire single-phase coolant. Preferably, the high-viscosity liquid polyolefin accounts for 1.0-5.0% of the mass fraction of the entire single-phase coolant. Further preferably, the high-viscosity liquid polyolefin accounts for 1.7-4.0% of the mass fraction of the entire single-phase coolant.

[0035] Furthermore, functional additives may be added to the above-mentioned single-phase coolant according to actual needs, wherein the mass fraction of the functional additives is 0-2%, including but not limited to antioxidants and defoaming agents.

[0036] Wherein, the antioxidant is a sulfur-free phenolic antioxidant, specifically including: 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butylphenol, 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-bis(2,6-di-tert-butylphenol), 4,4'-bis(2-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2, Any one or more combinations of 2'-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-butylenebis(3-methyl-6-tert-butylphenol), 4,4'-isopropylidenebis(2,6-di-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'-methylenebis(4-methyl-6-nonylphenol), 2,2'-isobutylidenebis(4,6-dimethylphenol) or 2,6-bis(2'-hydroxy-3'-tert-butyl-5'-methylbenzyl)-4-methylphenol;

[0037] The defoaming agent includes any one or more combinations of polyether defoaming agents, silicone defoaming agents and polyether-modified silicone defoaming agents.

[0038] Preferably, the antioxidant is 0.1-1.0% and the defoaming agent is 0.1-1.0% by mass; more preferably, the antioxidant is 0.2-0.8% and the defoaming agent is 0.2-0.8%;

[0039] Preferably, the single-phase coolant is composed of 98-99.8% low-viscosity liquid polyolefin, 0.1-1.0% antioxidant, and 0.1-1.0% defoaming agent. More preferably, the single-phase coolant is composed of 98.5-99.6% low-viscosity liquid polyolefin, 0.2-0.8% antioxidant, and 0.2-0.8% defoaming agent.

[0040] Preferably, the single-phase coolant is composed of 85-98% low-viscosity liquid polyolefin, 1.0-10.0% high-viscosity liquid polyolefin, 0.1-1.0% antioxidant, and 0.1-1.0% defoaming agent in terms of mass percentage;

[0041] More preferably, the single-phase coolant is composed of 95-98% low-viscosity liquid polyolefin and 95-98% high-viscosity liquid polyolefin.

[0042] 1.7-4.0%, antioxidant 0.2-0.8%, defoaming agent 0.2-0.8%.

[0043] In a second aspect, the method for preparing the single-phase coolant comprises: taking liquid polyolefin, adding an antioxidant, stirring until clear and transparent, then adding a defoaming agent to the obtained clear and transparent solution, and stirring until the mixture is uniform to obtain a single-phase coolant for immersion cooling.

[0044] In some embodiments, the preparation method further comprises uniformly mixing the high-viscosity liquid polyolefin and the low-viscosity liquid polyolefin and then adding an antioxidant and a defoaming agent.

[0045] In a third aspect, the present invention provides a single-phase immersion cooling system using the above-mentioned single-phase coolant, the single-phase immersion cooling system comprising:

[0046] An immersion cooling tank, which may be open or closed, is provided with the above-mentioned single-phase coolant, and at least one heat sink is placed in the immersion cooling tank;

[0047] The circulation pipeline connects the immersion cooling tank, the pump and the heat exchanger. After the coolant cools the heat dissipation device in the immersion cooling tank, it flows back to the pump and the heat exchanger through the circulation pipeline. The coolant cooled by the heat exchanger is transported to the immersion cooling tank through the circulation pipeline.

[0048] A pump is provided in the circulation pipeline and is used to provide power for the flow of the coolant in the circulation pipeline;

[0049] A single-phase coolant storage tank is connected to the pump through a valve and is used to store the coolant;

[0050] A controller, electrically connected to the pump, for detecting the coolant temperature and controlling the coolant flow rate;

[0051] The heat exchanger is arranged at any position between the immersion cooling tank and the pump, and has a built-in second cooling medium for indirectly cooling the single-phase coolant in the circulation pipeline.

[0052] Preferably, the heat dissipation device is an electronic device, a computing component or an electrical unit, including but not limited to a semiconductor die, a semiconductor package, a central processing unit, a motherboard, a server, a display card or a memory.

[0053] Preferably, the second cooling medium is water, more preferably cold water at 0-10°C.

[0054] The single-phase immersion cooling system immerses the heat sink in the single-phase coolant described above, so that the high-temperature heat energy generated by the heat sink during operation can be directly absorbed by the coolant, thereby ensuring that the heat sink can maintain an appropriate operating temperature to achieve the expected working efficiency and service life of the device.

[0055] The single-phase coolant in this cooling system undergoes no phase change, requiring less sealing and operator protection, and simplifying the cooling process. Furthermore, the single-phase coolant used is entirely hydrocarbon, which has a lower density than fluorocarbon coolants, reducing the overall weight of the cooling system. The system also lacks spray or jet devices, resulting in quieter operation.

[0056] In a fourth aspect, the present invention provides a cooling method using the above-mentioned single-phase immersion cooling system, comprising: using the above-mentioned single-phase immersion cooling system to cool one or more heat dissipation devices, immersing at least a portion or all of the heat dissipation devices in a single-phase coolant for cooling, the single-phase coolant that absorbs heat in the immersion cooling tank flows to the heat exchanger through a circulation pipeline, exchanges heat with the second cooling medium in the heat exchanger, and then flows back to the immersion cooling tank through the circulation pipeline after cooling.

[0057] Preferably, the temperature of the single-phase coolant in the cooling tank is controlled at 25-55°C.

[0058] In a fifth aspect, the present invention also provides an application of the above-mentioned single-phase coolant and / or the above-mentioned single-phase immersion cooling system in thermal management of processes such as data centers, IT equipment, chip manufacturing, semiconductor manufacturing and packaging testing, and liquid crystal display manufacturing.

[0059] Preferably, IT equipment refers to any single computer board or array of single computer boards that uses a microprocessor CPU, GPU, SSD and DDR memory to perform computing work, including but not limited to a single computer, a supercomputer, cloud computing, a computer gaming device, a computer server cluster, an Internet server, a 5G base station, a cryptocurrency mining farm, etc.

[0060] The beneficial effects of the present invention are:

[0061] (1) Compared with the prior art, the present invention uses low-viscosity liquid polyolefin as the main component of the single-phase coolant for immersion cooling. This type of liquid polyolefin does not contain fluorine or other halogens, is non-toxic, and has no impact on global warming, thereby achieving sustainable environmental protection and climate friendliness. Compared with high-density fluorocarbon coolants, it has a lower density, which can reduce the total weight of the cooling system. Compared with hydrocarbon base oils with similar carbon numbers and kinematic viscosities, low-viscosity liquid polyolefin has higher thermal conductivity, Mo value, and heat transfer performance, especially for indirect heat exchange in pipelines.

[0062] (2) The present invention also proposes to use high viscosity liquid polyolefin (kinematic viscosity at 100 ° C is 10-1000mm 2 / s) and low viscosity liquid polyolefin (100℃ kinematic viscosity less than 10mm 2 Mixing a coolant with a metallocene polyolefin (MPO) ( / s) can improve the coolant's thermal conductivity, volume resistivity, and breakdown voltage. This means that adding a small amount of high-viscosity liquid polyolefin to the coolant can simultaneously enhance both its heat transfer and dielectric properties. Single-phase coolants containing comb-shaped metallocene polyolefins exhibit the best heat transfer performance, particularly under varying flow regimes such as laminar, transitional, and turbulent, as well as under direct heat exchange in cooling tanks and indirect heat exchange within pipes. Application to single-phase immersion cooling systems can better ensure that the coolant and heat dissipation components maintain appropriate operating temperatures.

[0063] (3) The main component of the coolant proposed by the present invention, liquid polyolefin, is sulfur-free and has a low acid value. There are no active groups such as ester bonds in the polyolefin molecules. There is no need to worry about the corrosion of the heat dissipation device caused by acidification due to ester bond hydrolysis during use, especially pitting corrosion at locations such as welding points, and the increase in the resistivity of the coolant itself after the ester bond is hydrolyzed into carboxylic acid, which may lead to a short circuit of the integrated circuit system in the heat dissipation device. Therefore, this type of liquid polyolefin without active groups has better dielectric properties and stability, can be in direct contact with the heat dissipation device for a long time without corrosion, has better compatibility with metal parts, and does not require additional anti-corrosion agents to be added to the coolant. At the same time, the liquid polyolefin does not undergo phase change during the cooling process, and the requirements for the sealing of the cooling system and the protection of the operator are lower. The cooling system can be set to an open type, and the corresponding cooling method is simpler. Due to the excellent heat transfer effect of the coolant itself, there is no need to set a spray or jet device in the cooling system, and the operating noise is lower.

[0064] (4) The kinematic viscosity of the single-phase coolant proposed in the present invention is 10-1000 mm at 100°C. 2 / s high viscosity liquid polyolefin and kinematic viscosity less than 10mm at 100℃ 2 / s low-viscosity liquid polyolefins can be produced on a large scale. The raw materials of such liquid polyolefins are sufficient. By compounding liquid polyolefins with different viscosities, the low-viscosity liquid polyolefin components can be fully utilized. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 Schematic diagram of the single-phase immersion cooling system proposed in this invention

[0066] The symbols in the above drawings represent: 1-housing, 2-circulation pipeline, 3-immersion cooling tank, 4-heat exchanger, 5-pump, 6-heat dissipation device, 7-single-phase coolant, 8-second cooling medium, 9-valve, 10-single-phase coolant storage tank, 11-controller.

[0067] Figure 2 ApaSyn is a high viscosity liquid polyolefin TM 40(a) and PAO 40(b) 13 C-NMR spectrum, where the arrows indicate peaks with chemical shifts of 34.5 to 36.5. DETAILED DESCRIPTION

[0068] In order to make the purpose, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples. It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by those of ordinary skill in the art to which this application belongs.

[0069] Example 1

[0070] First, 495g of liquid polyolefin was placed in a blending tank. Then, 2.5g of 2,6-di-tert-butylphenol was added to the liquid polyolefin and stirred for 15 minutes until the mixture became clear. 2.5g of a polyether-modified silicone defoamer was added and stirred for 10 minutes until the mixture was uniform. The liquid in the blending tank was filtered to obtain a single-phase coolant. The liquid polyolefin was a C6 α-olefin trimer produced using a metallocene catalyst system and hydrogenation saturation, and was sourced from Yapei Technology Co., Ltd.

[0071] Example 2

[0072] First, 496g of liquid polyolefin was placed in a blending tank. Then, 2.0g of 2,6-di-tert-butylphenol was added to the liquid polyolefin and stirred for 15 minutes until the mixture became clear. 2.0g of a silicone defoamer was added and stirred for 10 minutes until the mixture was uniform. The liquid in the blending tank was filtered to obtain a single-phase coolant. The liquid polyolefin was a C6 α-olefin tetramer produced using a metallocene catalyst system and hydrogenation saturation, and was sourced from Yapei Technology Co., Ltd.

[0073] Example 3

[0074] First, 495g of liquid polyolefin was placed in a blending tank. Then, 2.5g of 2,6-di-tert-butylphenol was added to the liquid polyolefin and stirred for 15 minutes until the mixture became clear. 2.5g of a polyether-modified silicone defoamer was added and stirred for 10 minutes until the mixture was uniform. The liquid in the blending tank was filtered to obtain a single-phase coolant. The liquid polyolefin was a C8 α-olefin dimer produced using a metallocene catalyst system and hydrogenation saturation, and was sourced from Yapei Technology Co., Ltd.

[0075] Example 4

[0076] First, 495g of liquid polyolefin was placed in a blending tank. Then, 2.5g of 2,6-di-tert-butylphenol was added to the liquid polyolefin and stirred for 15 minutes until the mixture became clear. 2.5g of a polyether-modified silicone defoamer was added and stirred for 10 minutes until the mixture was uniform. The liquid in the blending tank was filtered to obtain a single-phase coolant. The liquid polyolefin was a C8 α-olefin trimer produced using a metallocene catalyst system and hydrogenation saturation, and was sourced from Yapei Technology Co., Ltd.

[0077] Example 5

[0078] First, 496g of liquid polyolefin was placed in a blending tank. Then, 2.0g of 2,6-di-tert-butylphenol was added to the liquid polyolefin and stirred for 15 minutes until the mixture became clear. 2.0g of a polyether-modified silicone defoamer was added and stirred for 10 minutes until the mixture was uniform. The liquid in the blending tank was filtered to obtain a single-phase coolant. The liquid polyolefin was a C10 α-olefin dimer produced using a metallocene catalyst system and hydrogenation saturation, and was sourced from Yapei Technology Co., Ltd.

[0079] Example 6

[0080] First, 495g of liquid polyolefin was placed in a blending tank. Then, 2.5g of 2,6-di-tert-butylphenol was added to the liquid polyolefin and stirred for 15 minutes until the mixture became clear. 2.5g of a silicone defoamer was added and stirred for 10 minutes until the mixture was uniform. The liquid in the blending tank was filtered to obtain a single-phase coolant. The liquid polyolefin was a C12 α-olefin dimer produced using a metallocene catalyst system and hydrogenation saturation, and was sourced from Yapei Technology Co., Ltd.

[0081] Example 7

[0082] First, 495g of liquid polyolefin was placed in a blending tank, and then 2.5g of 2,6-di-tert-butylphenol was added to the liquid polyolefin, stirred for 15 minutes until it became clear, 2.5g of silicone defoamer was added, and stirred for 10 minutes until the mixture was uniform. The liquid in the blending tank was filtered to obtain a single-phase coolant. The liquid polyolefin is a C10 alpha olefin oligomer prepared based on a conventional catalyst system and hydrogenation saturation. PAO 2 from Chevron Phillips Chemical Company.

[0083] Example 8

[0084] First, 495g of liquid polyolefin was placed in a blending tank, and then 2.5g of 2,6-di-tert-butylphenol was added to the liquid polyolefin, stirred for 15 minutes until it became clear, 2.5g of silicone defoamer was added, and stirred for 10 minutes until the mixture was uniform. The liquid in the blending tank was filtered to obtain a single-phase coolant. The liquid polyolefin is a C12 alpha olefin oligomer prepared based on a conventional catalyst system and hydrogenation saturation. PAO 2.5 from Chevron Phillips Chemical Company.

[0085] Example 9

[0086] First, 475g of the liquid polyolefin used in Example 1 was placed in a blending tank, and then 20g of high viscosity liquid polyolefin ApaSyn was added. TM 40 (kinematic viscosity at 100°C is 40 mm 2 / s, 314mm at 40℃ 2 / s, viscosity index 181) was added to a blending tank and stirred for 20 minutes. After that, 3.0g of 2,6-di-tert-butylphenol was added and stirred for 15 minutes until clear and transparent. 2.0g of a silicone defoamer was added and stirred for 10 minutes until uniformly mixed. The liquid in the blending tank was filtered to obtain a single-phase coolant. The high-viscosity liquid polyolefin is a comb-type C10 alpha olefin prepared using a metallocene catalyst system and is sourced from Yapei Technology Co., Ltd.

[0087] Example 10

[0088] The low viscosity liquid polyolefin was changed to 475g of the liquid polyolefin used in Example 3 and loaded into the blending tank. The remaining components and the prepared The process is the same as in Example 9 .

[0089] Example 11

[0090] The low viscosity liquid polyolefin was changed to 475g of the liquid polyolefin used in Example 5 and loaded into the blending tank. The remaining components and the prepared The process is the same as in Example 9 .

[0091] Example 12

[0092] The low viscosity liquid polyolefin was changed to 475 g of the liquid polyolefin used in Example 7 and loaded into the blending tank. The remaining components and the prepared The process is the same as in Example 9 .

[0093] Example 13

[0094] First, 487g of the liquid polyolefin used in Example 1 was placed in a blending tank, and then 8.5g of high viscosity liquid polyolefin ApaSyn was added. TM 300 (kinematic viscosity at 100°C is 300 mm 2 / s, 2000mm at 40℃ 2 / s, viscosity index 304) was added to a blending tank and stirred for 20 minutes. After that, 2.5g of 2,6-di-tert-butylphenol was added and stirred for 15 minutes until clear and transparent. 2.0g of a silicone defoamer was added and stirred for 10 minutes until uniformly mixed. The liquid in the blending tank was filtered to obtain a single-phase coolant. The high-viscosity liquid polyolefin is a comb-type C10 alpha olefin prepared using a metallocene catalyst system and is sourced from Yapei Technology Co., Ltd.

[0095] Example 14

[0096] The low viscosity liquid polyolefin was changed to 475g of the liquid polyolefin used in Example 3 and loaded into the blending tank. The remaining components and the prepared The process is the same as that of Example 13. .

[0097] Example 15

[0098] The low viscosity liquid polyolefin was changed to 475g of the liquid polyolefin used in Example 5 and loaded into the blending tank. The remaining components and the prepared The process is the same as that of Example 13. .

[0099] Example 16

[0100] The low viscosity liquid polyolefin was changed to 475 g of the liquid polyolefin used in Example 7 and loaded into the blending tank. The remaining components and the prepared The process is the same as that of Example 13. .

[0101] Example 17

[0102] First, 475g of the liquid polyolefin used in Example 1 was placed in a blending tank, and then 20g of high viscosity liquid polyolefin was added. PAO 40 (kinematic viscosity at 100°C is 40 mm 2 / s, 385mm at 40℃ 2 / s, viscosity index 154) was added to a blending tank and stirred for 20 minutes. After that, 3.0g of 2,6-di-tert-butylphenol was added and stirred for 15 minutes until clear and transparent. 2.0g of a silicone defoamer was added and stirred for 10 minutes until uniformly mixed. The liquid in the blending tank was filtered to obtain a single-phase coolant. The high-viscosity liquid polyolefin is a random polyalphaolefin (PAO) prepared from a C10 alpha olefin using a conventional catalyst system and is sourced from Lu'an Chemical Group Co., Ltd.

[0103] Example 18

[0104] The low viscosity liquid polyolefin was changed to 475g of the liquid polyolefin used in Example 3 and loaded into the blending tank. The remaining components and the prepared The process is the same as Example 17 .

[0105] Example 19

[0106] The low viscosity liquid polyolefin was changed to 475g of the liquid polyolefin used in Example 5 and loaded into the blending tank. The remaining components and the prepared The process is the same as Example 17 .

[0107] Example 20

[0108] The low viscosity liquid polyolefin was changed to 475 g of the liquid polyolefin used in Example 7 and loaded into the blending tank. The remaining components and the prepared The process is the same as Example 17 .

[0109] Comparative Example 1

[0110] First, 495g of Shell GTL base oil GS250 was added to a blending tank. Then, 3.0g of 2,6-di-tert-butylphenol was added to the liquid polyolefin and stirred for 15 minutes until the mixture became clear. 2.0g of a polyether-modified silicone defoamer was added and stirred for 10 minutes until the mixture was uniform. The liquid in the blending tank was filtered to obtain a single-phase coolant. Shell GTL base oil GS250 is a natural gas-to-liquid (GTL) product from Shell.

[0111] Comparative Example 2

[0112] First, add 495g of base oil 2 is put into a blending tank, then 3.0g of 2,6-di-tert-butylphenol is added to the liquid polyolefin, stirred for 15 minutes until it becomes clear, 2.0g of polyether-modified silicone defoamer is added, stirred for 10 minutes until the mixture is uniform, and the liquid in the blending tank is filtered to obtain a single-phase coolant. 2 for Base oil series products come from Lu'an Chemical Group Co., Ltd.

[0113] Comparative Example 3

[0114] The low viscosity liquid polyolefin was replaced with the base oil GS250 used in Comparative Example 1, 475 g was loaded into the blending tank, and the remaining components and preparation The process is the same as Example 9 .

[0115] Comparative Example 4

[0116] The low viscosity liquid polyolefin was replaced with the base oil GS250 used in Comparative Example 1, 475 g was loaded into the blending tank, and the remaining components and preparation The process is the same as Example 13 .

[0117] Comparative Example 5

[0118] The low viscosity liquid polyolefin was replaced with the base oil GS250 used in Comparative Example 1, 475 g was loaded into the blending tank, and the remaining components and preparation The process is the same as Example 17 .

[0119] Related test methods:

[0120] Kinematic viscosity: The kinematic viscosity of the coolant is tested at 100°C and 40°C using the ASTM D 445 standard;

[0121] Pour point: The pour point of the coolant is tested using the ASTM D 97 standard;

[0122] Thermal conductivity: Coolant was tested at 40°C using ASTM D 2717-2009, Standard Test Method for Thermal Conductivity of Liquids.

[0123] Specific heat capacity: The coolant was tested using DSC at 40°C;

[0124] Density: The density of the coolant at 40°C is tested using the ASTM D 1298-1999 method;

[0125] Flash point: The flash point of the coolant is tested using the Cleveland open cup method of ASTM D 92;

[0126] Copper corrosion: ASTM D 130 method was used to test the coolant at 50°C.

[0127] Volume resistivity: The coolant is tested at 25°C using the ASTM D 257 method.

[0128] Breakdown voltage: The coolant is tested using the disk electrode method of ASTM D 877.

[0129] 13 C-NMR: Use 13 C-NMR Detection of High Viscosity Liquid Polyolefin ApaSyn TM 40 and PAO 40, which characterizes the three-dimensional structure of polyolefin molecules, the sample is dissolved in CDCl3, and the standard substance is tetramethylsilane. 13 C-NMR instrument manufacturer: Bruker, Germany, model: AVANCE III HD 400.

[0130] Use low viscosity liquid polyolefin (100℃ kinematic viscosity less than 10mm 2 The test results of Examples 1-8 and Comparative Examples 1 and 2 using 4% dHg (2% dHg) as the coolant are shown in Table 1:

[0131] Table 1

[0132]

[0133] Among them, the flash point represents the safety of the coolant in use. The higher the flash point, the less likely it is to burn and catch fire. Therefore, the safer it is in use and it can be used at higher temperatures. As shown in Table 1, the liquid polyolefins of Examples 1-8 and the hydrocarbon base oils of Comparative Examples 1 and 2 all have a flash point of at least 137°C. Therefore, the resulting coolants are suitable for cooling equipment used at high temperatures and will not cause combustion or fire due to excessive temperatures of the cooling equipment.

[0134] The pour point refers to the lowest temperature at which a coolant can flow after being cooled. A low pour point indicates that the coolant is easy to flow and pour at low temperatures. The liquid polyolefins of Examples 1-8 and the hydrocarbon base oils of Comparative Examples 1 and 2 all have extremely low pour points below -40°C. This shows that such coolants can be conveniently stored, transported, and used at low temperatures. In particular, for applications in semiconductor manufacturing and packaging testing, liquid polyolefin coolants can maintain fluidity even under extremely low temperature conditions of -40°C, thereby playing a cooling and heat dissipation role.

[0135] Among them, the volume resistivity and breakdown voltage represent the insulation properties of the coolant. Higher volume resistivity and breakdown voltage indicate better dielectric strength and stronger insulation performance of the single-phase coolant. The liquid polyolefins of Examples 1-8 and the hydrocarbon base oils of Comparative Examples 1 and 2 all have relatively high volume resistivity and breakdown voltage. Therefore, when IT products such as servers are immersed in the coolant obtained by the present invention, the servers will not be damaged or cause equipment failure.

[0136] With respect to copper sheet corrosion, the coolants of Examples 1-8 and Comparative Examples 1 and 2 showed little difference. This indicates that liquid polyolefins, like hydrocarbon base oils, are non-corrosive to copper sheets and will not cause corrosion or damage to equipment immersed in the coolant for a long time during use. Furthermore, polyolefin coolants do not place high demands on the supporting cooling system, and there is no need for special anti-corrosion treatment of the cooling tank and circulation pipeline.

[0137] The kinematic viscosity at 100°C and 40°C is related to the carbon number of the liquid polyolefin itself. The basic rule is that the higher the carbon number of the polyolefin, the higher the kinematic viscosity. The saturated C8 α-olefin dimer of Example 3 has the lowest carbon number and the lowest kinematic viscosity. The kinematic viscosity increases with the carbon number of the polyolefin molecule. Examples 2, 4, and 6, respectively, have the highest carbon number and kinematic viscosity. The saturated C6 α-olefin tetramer of Example 2, the saturated C8 α-olefin trimer of Example 4, and the saturated C12 α-olefin dimer of Example 6 have the highest relative carbon number and kinematic viscosity. The kinematic viscosity of the saturated C6 α-olefin tetramer of Example 2 is higher than that of Examples 6 and 4.

[0138] In addition, with Shell GTL, Compared with hydrocarbon base oils such as 2, liquid polyolefins have higher thermal conductivity when the carbon number and 40°C kinematic viscosity are close, such as the saturated C10 α olefin dimer of Example 5 and the GTL GS250 base oil of Comparative Example 1, the saturated C8 α olefin trimer of Example 4 and the GTL GS250 base oil of Comparative Example 2. 2. Base oil. It can be concluded that when parameters such as carbon number and kinematic viscosity are the same or similar, liquid polyolefins prepared by polymerization of α-olefins have better potential for use as heat transfer fluids than conventional hydrocarbon base oils.

[0139] In the above low viscosity liquid polyolefin (100℃ kinematic viscosity less than 10mm 2 / s) is added to the high viscosity liquid polyolefin (100℃ kinematic viscosity is 10-1000mm 2 / s), wherein Examples 9-16 and Comparative Examples 3-4 used comb-type polyalphaolefins prepared based on a metallocene catalyst system, and Examples 17-20 and Comparative Example 5 used random polyalphaolefins prepared based on a conventional catalyst system. Comb-type polyalphaolefin ApaSyn TM 40 and random polyalphaolefin PAO 40 13 C-NMR spectrum Figure 2 As shown, referring to the method of Kim, I.; Zhou, JM.; Chung, HJ Polym Sci A: Polymer Chemistry 2000, 38: 1687-1697, by 13 C-NMR (solvent: CDCl3) detected the peak at the chemical shift (34.5-36.5) of the first carbon atom of the side chain connected to the main chain of the polyalphaolefin molecule, and found that ApaSyn TM 40 has a single peak within this range, PAO 40 has two peaks in this range, so it can be considered that ApaSyn TM 40 In many of the molecules, the first carbon atoms of the side chains connected to the main chain are in only one chemical environment. There are a large number of isotactic sequence segments in the molecule, which can be considered as ApaSyn TM 40 has a highly isotactic comb structure, and The first carbon atom of the side chain connected to the main chain in the PAO 40 molecule is in two different chemical environments, and the molecule is mostly a random sequence segment. PAO 40 is a random polyalphaolefin.

[0140] The test results of Examples 9-20 and Comparative Examples 3-5 obtained are shown in Table 2:

[0141] Table 2

[0142]

[0143] From the data in Table 2, it can be seen that high viscosity liquid polyolefin (100°C kinematic viscosity of 10-1000 mm 2 / s), the thermal conductivity of the coolant can be increased without significantly increasing the kinematic viscosity, which remains at 3-7 mm at 40 °C. 2 / s, the coolant maintains high fluidity, facilitating heat dissipation for equipment and components. Furthermore, the addition of high-viscosity liquid polyolefin can increase the coolant's flash point and pour point, facilitating safe use. However, the coolant's fluidity decreases at extremely low temperatures. The test results for Examples 9-20 and Comparative Examples 3-5 show a maximum pour point of -39°C, sufficient for storage and transportation at temperatures above -35°C. Furthermore, the addition of high-viscosity liquid polyolefin can increase the coolant's volume resistivity and breakdown voltage, resulting in higher dielectric strength and insulation properties. Regarding copper corrosion, the test results for Examples 9-20 and Comparative Examples 3-5 closely match those of the previous test using low-viscosity liquid polyolefin alone.

[0144] In order to further compare the heat transfer effects between the above-mentioned different single-phase coolants, the Mouromtseff number at 40°C (usually the operating temperature of such single-phase coolants is around 40°C) is calculated to measure the heat transfer effects of different temperature-controlled liquids at this temperature. The Mouromtseff number at a certain temperature is expressed by formula (1):

[0145]

[0146] In formula (1), Mo is the Mouromtseff number, ρ is the fluid density, κ is the thermal conductivity, C p is the specific heat capacity, μ is the kinematic viscosity of the fluid, and a, b, d, and e are empirical values ​​that vary depending on the laminar or turbulent flow state of the fluid. In laminar flow, a = 1, b = 1, d = 1, and e = 1; in turbulent flow, a = 0.8, b = 0.67, d = 0.33, and e = 0.47. A comparison of these data is shown in Table 3. The relative Mo values ​​of the coolant in laminar and turbulent conditions were calculated using the saturated C10 α-olefin dimer of Example 5 as a benchmark. The relative Mo values ​​of the different examples and comparative examples were then compared.

[0147] Table 3

[0148]

[0149]

[0150] As shown in Table 3, in Examples 1-8 and Comparative Examples 1 and 2 using low-viscosity liquid polyolefins alone, Examples 1, 3, 5, and 7 with lower kinematic viscosities have more outstanding heat transfer effects in laminar and turbulent states. When liquid polyolefins with similar kinematic viscosities are compared with hydrocarbon base oils, such as Example 5 and Comparative Example 1, and Example 4 and Comparative Example 2, it can be found that the heat transfer effects of liquid polyolefins are significantly better than those of hydrocarbon base oils in both laminar and turbulent states. This indicates that compared with hydrocarbon base oils with similar kinematic viscosities, low-viscosity liquid polyolefins (kinematic viscosity less than 10 mm at 100°C) have better heat transfer effects. 2 / s) is more advantageous to use as a coolant.

[0151] Adding high viscosity liquid polyolefin to coolant in Examples 1, 3, 5, 7 and Comparative Example 1 can improve the heat transfer effect in turbulent state, which is reflected in the more obvious improvement of Mo value in turbulent state. TM The Mo values ​​of Examples 9-12 and Comparative Example 3 of 40 were significantly improved, indicating that the addition of comb-type polyalphaolefin ApaSyn TM 40 can improve the heat transfer effect of the coolant, and adding ApaSyn TM300 and The Mo value of PAO 40 high viscosity liquid polyolefin coolant decreases to varying degrees under laminar flow conditions. This is due to the addition of ApaSyn TM 300 and When high-viscosity liquid polyolefins such as PAO 40 are added, the kinematic viscosity of the coolant itself increases more significantly. The increase in kinematic viscosity leads to a decrease in the heat transfer effect of the coolant itself. By increasing the Reynolds number Re of the coolant, turbulence occurs in the coolant during the flow process, thereby enhancing heat transfer and reducing the adverse effects of the increase in the kinematic viscosity of the coolant itself.

[0152] Through the calculation of the Mo values ​​of the coolants prepared in different embodiments under laminar and turbulent conditions in Table 3, the heat transfer effects of the coolants prepared in all embodiments and comparative examples can be judged as a whole. Figure 1 During the use of the immersion cooling system (shown in FIG), the coolant in the immersion cooling tank directly contacts the heat sink to exchange heat, causing itself to heat up. If the coolant itself is not cooled, the temperature difference between the coolant and the heat sink will decrease, the cooling effect will be significantly reduced, and it will be difficult to stably maintain the working temperature of the heat sink. Therefore, a heat exchanger for cooling the coolant itself is provided in the circulation pipe. The coolant flows through the pipe wall and indirectly exchanges heat with the second cooling medium in the heat exchanger to cool it down, thereby ensuring the cooling effect of the heat sink in the cooling tank. It can be seen from this that the single-phase coolant in the immersion cooling system of the present invention needs to undergo two heat exchanges. First, it is in direct contact with the heat sink in the cooling tank for heat exchange. Second, the coolant flows through the heat exchanger from the pipe, and the second cooling medium in the heat exchanger performs non-contact indirect heat exchange with the coolant. Therefore, it is necessary to evaluate the heat transfer effects of the coolants prepared in different embodiments and comparative examples in different heat exchange scenarios.

[0153] Calculation of the convective heat transfer coefficient when the coolant passes across the cylinder perpendicular to the tube axis, used to simulate Figure 1 A scene showing coolant flowing from the side of a cylindrical heat sink in a cooling tank.

[0154] Assume that the coolant flows through a cylinder with an outer diameter of 250 mm at a flow rate (v) of 0.5 m / s (laminar flow) and 5.0 m / s (turbulent flow) at 40°C, where the characteristic length L is 250 mm. First, calculate the dimensionless Reynolds number, Prandtl number, and Nusselt number, and then obtain the convective heat transfer coefficient h, where the unit of h is W / (m 2 K), which is defined as when the temperature difference between the heat transfer interfaces is 1K, 1m 2The amount of heat that can be transferred per second by the wall area, h, directly reflects the convective heat transfer capacity of different single-phase coolants to the heat sink in direct contact with them or the second cooling medium in indirect contact with them. The higher h is, the stronger the convective heat transfer capacity of the single-phase coolant to the heat sink or the second cooling medium.

[0155] Dynamic viscosity: η = ρμ;

[0156] Reynolds number, Prandtl number, and Nusselt number:

[0157]

[0158]

[0159]

[0160] Among them, when the coolant flow rate is 0.5m / s at 40℃, the calculated Reynolds number is 10<Re L ≤1.5*10 5 , indicating that the coolant flow boundary layer is laminar flow, Reynolds number 4000≤Re L ≤40000, from the table, we know that C = 0.193, n = 0.618, and the corresponding convective heat transfer coefficient h is calculated by the following formula:

[0161]

[0162] Among them, when the coolant flow rate is 5.0m / s at 40℃, the calculated Reynolds number Re L >1.5*10 5 , indicating that the flow boundary layer of the coolant is turbulent flow, Reynolds number 40000≤Re L ≤4*10 5 , we can see from the table that C = 0.0266, n = 0.805, and the corresponding convective heat transfer coefficient h is calculated by the following formula:

[0163]

[0164] Calculation of the convective heat transfer coefficient when the coolant sweeps across the cylinder parallel to the tube axis, used to simulate Figure 1 A scene in which coolant in a cooling tank flows from a circular cross-section through a cylindrical heat sink.

[0165] Assuming that the above coolant flows through a cylinder with a length of 1000 mm at a flow rate (v) of 0.5 m / s (laminar flow) and 5.0 m / s (turbulent flow) at 40°C, where the characteristic length L is 1000 mm, calculate the dimensionless Reynolds number, Prandtl number, and Nusselt number according to the above formula.

[0166] Among them, when the coolant flow rate is 0.5m / s at 40℃, the calculated Reynolds number Re L ≤5.0*10 5 , indicating that the coolant flow boundary layer is laminar flow. From the table, we know that C = 0.332, n = 0.5, and the convective heat transfer coefficient h is calculated by the following formula:

[0167]

[0168] When the coolant flow rate is 5.0m / s at 40℃, the calculated Reynolds number Re L >5.0*10 5 , indicating that the coolant flow boundary layer is turbulent flow. From the table, we know that C = 0.0296, n = 0.8, and the convective heat transfer coefficient h is calculated by the following formula:

[0169]

[0170] Calculation of the convective heat transfer coefficient of coolant in a circular pipe for simulation Figure 1 The coolant passes through the heat exchange process between the heat exchanger and the second cooling medium in the circulation pipeline.

[0171] Assume that the coolant flows through a heat exchange tube with an inner diameter (d) of 50 mm and a length (L) of 3 m at a flow rate (v) of 0.5 m / s (transitional flow) and 5.0 m / s (turbulent flow) at 40°C. Calculate the dimensionless Reynolds number and Prandtl number using the following formulas:

[0172] Reynolds number and Prandtl number:

[0173]

[0174]

[0175] Among them, when the coolant flow rate is 0.5m / s at 40℃, the calculated Reynolds number is 2300≤Re f ≤10000, which is the transition state between laminar flow and turbulent flow, and also meets the following conditions: Prandtl number 0.5≤Pr≤2000, and the Gnielinski formula is used to calculate the Darcyl drag coefficient f and the convection heat transfer coefficient h in the tube. 管内 :

[0176] f=(1.82lgRe f -1.64) -2 ;

[0177]

[0178] Among them, when the coolant flow rate is 5.0m / s at 40℃, the calculated Reynolds number Ref >10000, which is a typical vigorous turbulent state in the tube. At the same time, the following conditions are met: Prandtl number 0.6≤Pr≤160, L / d≥10, and the dimensionless Nusselt number is calculated using the Dittus-Boelter formula:

[0179]

[0180] The coolant flows through the circular pipe and is cooled by itself, n = 0.3, from which the convection heat transfer coefficient h in the pipe is calculated. 管内 :

[0181]

[0182] According to the above method, the convective heat transfer coefficient h of the coolant prepared in Comparative Examples 1, 3, 4, 5 and Examples 1, 3, 5, 7, 9-20 at 40 ° C with a flow rate of 0.5 m / s and 5.0 m / s passing through the heat sink (cylinder) from different directions for direct cooling is calculated. 横掠 and h 纵掠 At the same time, calculate the convection heat transfer coefficient h when the coolant flows through the heat exchanger at a flow rate of 0.5m / s and 5.0m / s at 40℃. 管内 , and the results are listed in Table 4.

[0183] Table 4

[0184]

[0185]

[0186] As shown in Table 4, the convective heat transfer coefficients of Examples 1, 3, 5, 7 and Comparative Example 1 using low-viscosity liquid polyolefins alone are compared. It is found that in the turbulent process, including the cooling liquid sweeping across and longitudinally across the cylinder and the transition state and turbulence in the tube, the convective heat transfer coefficient of Example 3, which has the lowest kinematic viscosity at 40°C, of ​​the saturated C8 α-olefin dimer is relatively the highest, which is consistent with the results of the heat transfer effect evaluation calculated by the Mo number in Table 3. However, in the laminar flow process of the cooling liquid sweeping across and longitudinally across the cylinder, the convective heat transfer coefficients of Examples 7 and 5, which have higher thermal conductivity at 40°C, are higher than those of Comparative Example 1. The resulting convective heat transfer coefficient is relatively high, a finding not previously observed in heat transfer evaluations calculated through Mo number calculations. This indicates that, in a technical solution using only low-viscosity liquid polyolefins, saturated α-olefin oligomers of varying carbon numbers, kinematic viscosities, and thermal conductivities each have their own advantages during immersion cooling. Saturated α-olefin oligomers with low carbon numbers, low kinematic viscosities, and low thermal conductivity exhibit higher heat transfer capabilities within pipelines and under turbulent flow conditions, while saturated α-olefin oligomers with high carbon numbers, high kinematic viscosities, and high thermal conductivity exhibit higher heat transfer capabilities under laminar flow conditions. Furthermore, a comparison of Example 5 with Comparative Example 1 demonstrates that liquid polyolefins exhibit significant heat transfer capabilities compared to hydrocarbon base oils of similar kinematic viscosity under all flow conditions.

[0187] On the basis of Examples 1, 3, 5, 7 and Comparative Example 1, high viscosity liquid polyolefin (100°C kinematic viscosity of 10-1000 mm 2 / s) were used to prepare Examples 9-20 and Comparative Examples 3-5. By comparing the convective heat transfer coefficients under different conditions, it was found that after adding high-viscosity liquid polyolefin, the convective heat transfer coefficients of the coolant in the laminar and turbulent states were increased to varying degrees, especially in Examples 9-12 and Comparative Example 3, when the comb-shaped polyalphaolefin ApaSyn was added. TM After 40, the convective heat transfer coefficient of the coolant increases more. For the process of cooling the coolant through the heat exchanger in the pipeline, only the comb-shaped polyalphaolefin ApaSyn is added in Examples 9-12 and Comparative Example 3. TM After 40, the convection heat transfer coefficient of the coolant in the tube is improved compared to before adding ApaSyn TM 300 and The convection heat transfer coefficient of the PAO 40 coolant in the tube remains the same or decreases to varying degrees, which indicates that the coolant without high viscosity liquid polyolefin and the coolant with comb-structured polyalphaolefin ApaSyn TM The heat transfer effect of 40% coolant in the circulation pipe of the immersion cooling system is generally higher than that of the coolant with ApaSyn TM 300 and PAO 40 coolant, in which comb-structured polyalphaolefin ApaSyn is added TM40 coolant has better heat transfer effect than low viscosity liquid polyolefin coolant used alone.

[0188] Therefore, as a more preferred technical solution, a high-viscosity polyalphaolefin (ApaSyn) with a comb-shaped structure is added to the low-viscosity liquid polyolefin. TM 40 In the single-phase immersion cooling system, there are two different application scenarios and different flow states of single-phase coolant (laminar flow, transitional state, turbulent flow) with excellent heat transfer effects. The two application scenarios refer to: the single-phase coolant is in direct contact with the heat sink in the cooling tank to take away the heat of the heat sink itself, and the coolant itself heats up; the single-phase coolant passes through the heat exchanger in the pipeline to perform non-contact heat exchange with the second cooling medium, and the coolant itself cools down.

[0189] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for parts thereof. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention. Although the above describes the specific implementation methods of the present invention, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that, based on the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present invention.

Claims

1. A single-phase coolant having a kinematic viscosity of less than 10 mm at 100°C 2 / s, the main component of the single-phase coolant is a mixture of various liquid polyolefins; it is characterized by: The liquid polyolefin comprises at least one low-viscosity liquid polyolefin, which is a metallocene polyolefin or a conventional polyolefin, and is prepared by a metallocene-based or non-metallocene-based catalyst system, and the kinematic viscosity of the low-viscosity liquid polyolefin is less than 10 mm at 100°C. 2 / s; The single-phase coolant also includes a high-viscosity liquid polyolefin, wherein the high-viscosity liquid polyolefin is a highly isotactic comb-structured metallocene polyolefin; the kinematic viscosity of the high-viscosity liquid polyolefin is 10-1000 mm at 100°C. 2 / s, and the viscosity index is not less than 150; the high-viscosity liquid polyolefin accounts for 1.0-10.0% of the mass fraction of the entire single-phase coolant.

2. The single-phase coolant according to claim 1, characterized in that The kinematic viscosity of low viscosity liquid polyolefin is 0.5-5.0 mm at 100°C 2 / s.

3. The single-phase coolant according to claim 1, characterized in that The kinematic viscosity of low viscosity liquid polyolefin is 0.5-3.5 mm at 100°C 2 / s.

4. The single-phase coolant according to claim 1, characterized in that The kinematic viscosity of low viscosity liquid polyolefin is 0.5-2.5 mm at 100°C 2 / s.

5. The single-phase coolant according to claim 1, characterized in that The kinematic viscosity of low viscosity liquid polyolefin is 2.0-10.0 mm at 40°C 2 / s.

6. The single-phase coolant according to claim 1, characterized in that The kinematic viscosity of low viscosity liquid polyolefin is 2.0-9.0 mm at 40°C 2 / s.

7. The single-phase coolant according to claim 1, characterized in that The kinematic viscosity of low viscosity liquid polyolefin is 2.0-6.0 mm at 40°C 2 / s.

8. The single-phase coolant according to claim 1, characterized in that The liquid polyolefin accounts for at least 98% by mass of the entire single-phase cooling liquid.

9. The single-phase coolant according to claim 1, characterized in that The liquid polyolefin accounts for 99-100% of the mass fraction of the entire single-phase coolant.

10. The single-phase coolant according to claim 1, characterized in that The low-viscosity liquid polyolefin is obtained by catalytic polymerization of ethylene, propylene or substituted olefins with a carbon number of C4-C20 using a metallocene or non-metallocene catalyst to obtain an unsaturated metallocene polyolefin. The unsaturated metallocene polyolefin is separated and then hydrogenated and saturated to obtain the final low-viscosity liquid polyolefin. The unseparated polyolefin is a high-viscosity liquid polyolefin.

11. The single-phase coolant according to claim 10, characterized in that The substituted olefin includes one or a mixture of alpha olefin, vinylidene olefin, disubstituted vinylidene olefin, trisubstituted vinylidene olefin.

12. The single-phase coolant according to claim 11, characterized in that The structures of the α-olefin (I), vinylidene olefin (II), disubstituted vinylidene olefin (III, IV) and trisubstituted vinylidene olefin (V) are shown below. Wherein, R1 includes a straight chain or branched alkane with a carbon number of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, R2 and R3 include a straight chain or branched alkane with a total carbon number of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, R2, R3 and R4 include a straight chain or branched alkane with a total carbon number of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, wherein the carbon numbers of R1, R2, R3 and R4 may be the same or different.

13. The single-phase coolant according to claim 11, characterized in that The raw material for preparing the liquid polyolefin is C5-C13 alpha olefin.

14. The single-phase coolant according to claim 11, characterized in that The raw material for preparing the liquid polyolefin is C5-C13 linear alpha olefin.

15. The single-phase coolant according to claim 1, characterized in that The kinematic viscosity of high viscosity liquid polyolefin is 10-100 mm at 100°C. 2 / s.

16. The single-phase coolant according to claim 1, characterized in that The high-viscosity liquid polyolefin accounts for 1.0-5.0% by mass of the entire single-phase coolant.

17. The single-phase coolant according to claim 1, characterized in that The high-viscosity liquid polyolefin accounts for 1.7-4.0% by mass of the entire single-phase coolant.

18. The single-phase coolant according to claim 1, characterized in that: The single-phase coolant also includes a functional additive, wherein the mass fraction of the functional additive is 0-2%, and includes an antioxidant and a defoaming agent.

19. The single-phase coolant according to claim 18, characterized in that: The antioxidant is a sulfur-free phenolic antioxidant, specifically including: 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butylphenol, 4,4'-methylenebis(2,6-di-tert-butylphenol), 4,4'-bis(2,6-di-tert-butylphenol), 4,4'-bis(2-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2 Any one or more combinations of '-methylenebis(4-ethyl-6-tert-butylphenol), 4,4'-butylenebis(3-methyl-6-tert-butylphenol), 4,4'-isopropylidenebis(2,6-di-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'-methylenebis(4-methyl-6-nonylphenol), 2,2'-isobutylidenebis(4,6-dimethylphenol) or 2,6-bis(2'-hydroxy-3'-tert-butyl-5'-methylbenzyl)-4-methylphenol.

20. The single-phase coolant according to claim 18, characterized in that: The defoaming agent includes any one or more combinations of polyether defoaming agents, silicone defoaming agents and polyether-modified silicone defoaming agents.

21. The single-phase coolant according to claim 18, characterized in that: In terms of mass percentage, the antioxidant is 0.1-1.0%, and the defoaming agent is 0.1-1.0%.

22. The single-phase coolant according to claim 18, characterized in that: In terms of mass percentage, the antioxidant is 0.2-0.8%, and the defoaming agent is 0.2-0.8%.

23. The single-phase coolant according to claim 18, characterized in that: The single-phase coolant is composed of 85-98% of low-viscosity liquid polyolefin, 1.0-10.0% of high-viscosity liquid polyolefin, 0.1-1.0% of antioxidant, and 0.1-1.0% of defoaming agent in terms of mass percentage.

24. The single-phase coolant according to claim 18, characterized in that: Calculated by mass percentage, the single-phase coolant is composed of 95-98% low-viscosity liquid polyolefin, 1.7-4.0% high-viscosity liquid polyolefin, 0.2-0.8% antioxidant, and 0.2-0.8% defoaming agent.

25. The method for preparing a single-phase coolant according to any one of claims 18 to 24, comprising: Liquid polyolefin is taken, an antioxidant is added, and the mixture is stirred until it becomes clear and transparent. A defoaming agent is then added to the obtained clear and transparent solution, and the mixture is stirred until the mixture is uniform to obtain a single-phase coolant for immersion cooling.

26. A single-phase immersion cooling system using the single-phase coolant according to any one of claims 1 to 24, the single-phase immersion cooling system comprising: An immersion cooling tank, which may be open or closed, is provided with the above-mentioned single-phase coolant, and at least one heat sink is placed in the immersion cooling tank; The circulation pipeline connects the immersion cooling tank, the pump and the heat exchanger. After the coolant cools the heat dissipation device in the immersion cooling tank, it flows back to the pump and the heat exchanger through the circulation pipeline. The coolant cooled by the heat exchanger is transported to the immersion cooling tank through the circulation pipeline. A pump is provided in the circulation pipeline and is used to provide power for the flow of the coolant in the circulation pipeline; A single-phase coolant storage tank is connected to the pump through a valve and is used to store the coolant; A controller, electrically connected to the pump, for detecting the coolant temperature and controlling the coolant flow rate; The heat exchanger is arranged at any position between the immersion cooling tank and the pump, and has a built-in second cooling medium for indirectly cooling the single-phase coolant in the circulation pipeline.

27. The single-phase immersion cooling system according to claim 26, characterized in that: The heat dissipation device is an electronic device, a computing component or an electrical unit, including a semiconductor die, a semiconductor package, a central processing unit, a motherboard, a server, a display card or a memory.

28. The single-phase immersion cooling system according to claim 26, characterized in that: The second cooling medium is water.

29. The single-phase immersion cooling system according to claim 26, characterized in that: The second cooling medium is cold water at 0-10°C.

30. A cooling method using the single-phase immersion cooling system according to any one of claims 26 to 29, comprising: The single-phase immersion cooling system is used to cool one or more heat sinks. At least a portion or all of the heat sink is immersed in a single-phase coolant for cooling. The single-phase coolant absorbs heat in the immersion cooling tank and flows through a circulation pipeline to a heat exchanger. After heat exchange with a second cooling medium in the heat exchanger, it is cooled and then flows back to the immersion cooling tank through a circulation pipeline. The temperature of the single-phase coolant in the cooling tank is controlled at 25-55°C.

31. Application of the single-phase coolant according to any one of claims 1 to 24 and / or the single-phase immersion cooling system according to any one of claims 26 to 29 in thermal management of data centers, IT equipment, chip manufacturing, semiconductor manufacturing and packaging testing, and liquid crystal display manufacturing processes.

32. The use according to claim 31, characterized in that IT equipment refers to any single computer board or array of single computer boards that uses a microprocessor CPU, GPU, SSD, and DDR memory to perform computing work, including a single computer, a supercomputer, a computer gaming device, a computer server farm, or an Internet server.

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