Narrow fraction mineral base oil single-phase immersed cooling liquid and preparation method thereof

Abstract

The invention belongs to the technical field of data center cooling, and discloses a narrow fraction mineral base oil single-phase immersed cooling liquid and a preparation method thereof in order to solve the problem of poor stability of the cooling liquid, and the preparation method comprises the following steps: preparing a dispersant; the preparation method comprises the following steps: adding an antioxidant and nano heat-conducting particles into narrow fraction mineral base oil, and stirring to obtain a product a; heating narrow fraction mineral base oil, adding a dispersing agent and an anti-rust agent, and stirring to obtain a product b; and finally mixing and stirring the product a and the product b. The cooling liquid provided by the invention takes the narrow fraction mineral base oil as a matrix, solves the problems of poor heat dissipation, weak oxidation resistance and low flash point of the traditional mineral oil through the synergistic effect of all the components, has low viscosity, high flash point, excellent electrical insulation and thermal conductivity, good compatibility and low volatilization rate, is suitable for immersed cooling systems such as a large computing power data center, and has wide application prospects. The high-efficiency heat dissipation and safe operation requirements of high-heat-density equipment can be met, the preparation process is simple, the cost is low, and the industrial application value is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of data center cooling, in particular to a narrow-cut mineral base oil single-phase immersion cooling liquid and a preparation method thereof. BACKGROUND

[0002] With the innovative development of artificial intelligence, cloud computing, big data and blockchain technologies, the 5G communication era characterized by high speed, low latency and large connection has also begun. As information infrastructure, data center servers and communication equipment bear more and more computing load, and the requirement for computing efficiency is also higher and higher. In order to cope with the challenge of computing load and computing efficiency, data center servers and communication equipment are constantly improving their processing capacity and integration, which leads to the increasing of power density and heat density. This not only brings huge energy consumption problems, but also puts forward higher requirements for refrigeration technology.

[0003] The key to solving the high heat density problem of data center servers and communication equipment by refrigeration technology lies in the cooling liquid. Immersion liquid cooling technology is divided into single-phase immersion liquid cooling and two-phase immersion liquid cooling according to whether the cooling liquid undergoes phase change. Among them, two-phase immersion liquid cooling mainly relies on the latent heat of evaporation of the cooling liquid, and through the boiling and condensation process, the heat transfer efficiency of the cooling liquid is exponentially improved. In single-phase immersion liquid cooling, the liquid phase directly contacts for heat exchange. At present, in the data center server industry, the design structure and application scene of immersion cooling servers are different, and there is no unified technical specification and standard for immersion cooling liquid.

[0004] The mainstream cooling liquid has two development directions, namely carbon hydrogen and organic silicon cooling liquid and carbon fluoride cooling liquid. Among them, fluorinated liquid has higher cost, large product density, large equipment bearing capacity, relatively higher energy consumption, and potential risk of destroying ozone layer, so the demand for replacement is increasing; carbon hydrogen and organic silicon cooling liquid is commonly known as oil cooling liquid in the industry, which is clear and transparent at room temperature, viscous, generally lower in density than water, not easy to volatilize, non-corrosive to metal, lower toxicity and much lower price than fluorinated liquid. Including natural mineral oil, synthetic oil (PAO, CTL, GTL), synthetic ester and silicone oil. Silicone oil is mainly synthesized by man, and high flash point products can be designed by modification, but the higher the flash point, the higher the viscosity, and the lower the risk of flammability, which leads to flow and heat dissipation difficulties. The use of synthetic ester cooling liquid has limitations. In the system containing water, hydrolysis may occur, resulting in the production of acidic substances, affecting the performance and stability of the cooling liquid, causing corrosion to the equipment, and being incompatible with some materials, some metals, plastics or rubber materials, which may cause chemical reaction, corrosion, swelling or hardening, etc., leading to sealing failure or leakage, thereby increasing the risk of equipment failure. Synthetic oil has higher requirements for synthesis process, additive compatibility and production conditions, and the production cost is high. Natural mineral oil has relatively low price, so it is favored by the market. The technical bottleneck of mineral type insulation cooling liquid at present is:

[0005] (1) Poor heat dissipation capacity. Compared with silicone oil and fluorinated liquid cooling liquid, the heat transfer effect of mineral type insulation cooling liquid is the worst.

[0006] (2) Poor oxidation resistance. The base oil of mineral type insulation cooling liquid is refined from petroleum, and the decomposition and oxidation of hydrocarbon molecules are difficult to avoid in use, which causes acidification and pollution, affects the properties of the cooling liquid, and even causes corrosion of the cooled liquid device.

[0007] (3) Low flash point. The low viscosity of mineral type insulation cooling liquid improves the heat transfer efficiency, but also brings the defect of low flash point. At present, the contradiction between viscosity and flash point needs to be solved, and reducing viscosity and improving flash point is a great challenge. SUMMARY

[0008] The immersion cooling liquid composition provided by the present application can overcome the above technical bottlenecks. The composition has low viscosity and high flash point base oil, and the product has excellent lubricity and low temperature flowability; the composition has ultra-low kinematic viscosity (2.0-6.0mm 2The fluid medium of the narrow fraction mineral base oil one-phase immersion cooling liquid has the advantages of high heat transfer capacity of the cooling liquid, high oxidation stability of the composition, long service life of the cooling liquid, excellent thermal and electrical properties (including high dielectric strength, low dielectric loss, etc.), high safety (high flash point), low volatility, and good compatibility. The preparation method is simple, the cost is low, the influence of international raw material fluctuation cost and supply is small, and the technical requirements of the new generation of large computing power data center, large model, edge computing, power battery and distributed energy storage and other immersion cooling management systems can be met.

[0009] To achieve the above-mentioned purpose, the following technical solutions are adopted in the present application:

[0010] A narrow fraction mineral base oil one-phase immersion cooling liquid, based on the total mass of the cooling liquid, includes the following mass percentages of raw materials: antioxidant 0.5%-3.0%, anti-rust agent 0.5%-3%, nano heat-conducting microparticle 1.0%-5%, dispersing agent 1.0%-5%, and the rest is narrow fraction mineral base oil.

[0011] Further, the narrow fraction mineral base oil is obtained by vacuum distillation of a 100℃ viscosity of 2mm 2 / s type III base oil, cutting and recovering 10%-90% of the fraction oil, removing less than 10% of the fraction oil with low flash point and more than 90% of the fraction oil with high viscosity and high flash point, and retaining the fraction oil with a 40℃ viscosity of 5.0mm 2 / s-7mm 2 / s and a flash point of more than 155℃.

[0012] Further, the antioxidant is a hindered thio-phenol antioxidant.

[0013] Further, the anti-rust agent is sodium petroleum sulfonate.

[0014] Further, the nano heat-conducting microparticle is one or more of boron nitride, silicon nitride, and aluminum nitride.

[0015] Further, the dispersing agent is a copolymer generated by copolymerization of methacrylate and N-vinyl pyrrolidone, and the methacrylate includes monomer ester group 1 and monomer ester group 2.

[0016] Further, the monomer ester group 1 is one or more of octyl methacrylate, isooctyl methacrylate, decyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, isotridecyl methacrylate, or myristyl methacrylate, and the monomer ester group 2 is one or more of hexadecyl methacrylate, octadecyl methacrylate, eicosyl methacrylate, docosyl methacrylate, or tetracosyl methacrylate.

[0017] Further, the molar ratio of the N-vinylpyrrolidone, monomer ester group 1, monomer ester group 2 is 1: (1-10): (0.5-8).

[0018] A preparation method of a narrow-cut mineral base oil single-phase immersion cooling liquid, comprising the following steps:

[0019] (1) uniformly mix N-vinylpyrrolidone, methacrylate monomer, molecular chain transfer agent and initiator, and drop into narrow-cut mineral base oil, and copolymerize at 60-160℃ for 3-10h, and after the reaction is completed, perform vacuum filtration, alcohol washing and vacuum drying to obtain a dispersant;

[0020] (2) add antioxidants and nano heat-conducting microparticles to narrow-cut mineral base oil according to the formula proportion, continuously stir, the stirring temperature is 60-70℃, and the stirring time is 1-2h to obtain product a;

[0021] (3) add narrow-cut mineral base oil to a blending kettle, start stirring, heat to 70-80℃ and keep the temperature, add the dispersant and rust inhibitor, continue to stir and react, the stirring speed is 200-300r / min, and the stirring time is 1-2h to obtain product b;

[0022] (4) finally, add product a to product b, continuously stir and react, the stirring temperature is 55-60℃, and the stirring time is 1-2h, and the immersion cooling liquid composition is obtained.

[0023] Further, the copolymerization reaction in step (1) comprises a molecular chain transfer agent and an initiator, wherein the molecular chain transfer agent is an alpha-methylstyrene dimer, and the addition amount is 0.5%-6% of the total amount of N-vinylpyrrolidone and methacrylate monomer; the initiator is one or more of t-butyl peroxybenzoate, azobis cyanovalerate, azobis isobutylene, dibenzoyl peroxide and azobis isoheptyl cyanide, and the addition amount is 0.5%-6% of the total amount of N-vinylpyrrolidone and methacrylate monomer.

[0024] The present application has the following beneficial effects:

[0025] (1) The antioxidant is preferably a hindered thio-phenolic antioxidant. The antioxidant has an amine type and a shielded phenol type. For low temperature below 150℃, the phenol type antioxidant has the best effect. Compared with the amine type antioxidant, the phenol type antioxidant is more compatible with the base oil, does not produce precipitation, and has stronger activity at low temperature. Due to the deep processing technology, the natural sulfur component is missing in the narrow fraction mineral base oil. The narrow fraction mineral base oil has good sensitivity to sulfur-containing antioxidants. Therefore, the hindered thio-phenolic antioxidant is preferred. The hindered thio-phenolic antioxidant containing a thioether group antioxidant functional group can terminate the chain oxidation reaction of hydrocarbon molecules by the reaction of phenolic hydroxyl group and ROO·, and can decompose ROOH into ROH through the thioether group, thereby generating a self-synergistic antioxidant effect, so that the hindered thio-phenolic antioxidant has better antioxidant activity than the sulfur-free phenol type.

[0026] (2) The anti-rust agent is preferably sodium petroleum sulfonate. The sulfonic acid group provides excellent anti-rust performance. At the same time, as a surfactant, it is also an emulsifier, which can reduce the surface tension and dynamic contact angle of the cooling liquid, improve the wettability of the oil product, and form a stable emulsion system with the base oil. It can strengthen the heat transfer efficiency in the convection stage, improve the low-temperature cooling rate, and enhance the heat dissipation performance of the cooling liquid.

[0027] (3) The nano heat-conducting particles boron nitride, aluminum nitride, and silicon nitride increase the specific surface area and specific heat capacity, and the interaction and collision between particles and particles, particles and liquid, and particles and wall surface, enhance the turbulence intensity of the fluid, make the liquid cross-section temperature distribution flat, reduce the thickness of the laminar flow bottom layer, and enhance the heat capacity, thereby improving the thermal conductivity.

[0028] (4) The narrow fraction mineral base oil cuts and recovers the fraction oil in the range of 10% to 90%, removes the fraction oil below 10% with low flash point and the fraction oil above 90% with high viscosity and high flash point, removes the high viscosity and easily oxidized components with heteroatom-containing structures such as high aromatics, the remaining narrow fraction mineral base oil has further improved antioxidant performance, and the evaporation loss is also reduced. The low viscosity base oil is manufactured while achieving high flash point application, the low viscosity improves the heat dissipation performance of the cooling liquid, and the high flash point ensures the safety performance of the cooling.

[0029] (5) The dispersant is a copolymer of methacrylate and N-vinyl pyrrolidone, which is a high-molecular polymer with extremely strong amphiphilic properties. The polymer long molecular chain has both hydrophilic and hydrophobic groups, and the molecule structure makes it have low surface activity, adsorption to solid surfaces, and three-dimensional shielding ability formed by hydrophilic, so that the solid particles have excellent dispersion stability. The hydrogen bond complexing ability with other organic and inorganic compounds also makes it have condensation and solubilizing ability, can make the cooling liquid resist dust, oxides, and oil sludge to become clear and stable, and can maintain the integrity of the electrical signal. The dispersant belongs to an ester type, which can greatly improve the breakdown voltage of the immersed cooling liquid.

[0030] (6) The present application adds a self-developed dispersant (the dispersant is an ester polymer copolymerized by methacrylate and N-vinyl pyrrolidone), which is adsorbed with the nano heat-conducting microparticles, so as to improve the heat-conducting and heat-dissipating performance of the mineral oil; the high-polarity N-vinyl pyrrolidone can capture the nano heat-conducting microparticles, carry the nano heat-conducting microparticles to uniformly disperse in the mineral oil, and form a stable heat-conducting channel of nano heat-conducting microparticle-silicon chain-nano heat-conducting microparticle in the cooling liquid; the nano heat-conducting microparticles have excellent heat-conducting performance, and act as a driving force in the heat-conducting channel to accelerate the heat transfer, so that the cooling liquid has higher heat-conducting and heat-dissipating performance. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Figure is a test phenomenon diagram of the cooling liquid with the added nano heat-conducting microparticles of the present application example 4 at room temperature and standing for 240 days;

[0032] Figure 2 Figure is a test phenomenon diagram of the cooling liquid with the added nano heat-conducting microparticles of the present application example 5 at room temperature and standing for 240 days;

[0033] Figure 3 Figure is a test phenomenon diagram of the cooling liquid with the added nano heat-conducting microparticles of the present application comparative example 4 at room temperature and standing for 240 days. DETAILED DESCRIPTION

[0034] The present application will be described in detail below with specific examples. The following examples will help those skilled in the art to further understand the present application, but do not limit the present application in any way. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present application. These all belong to the protection scope of the present application.

[0035] In the present application, a preparation method of a narrow-cut mineral base oil single-phase immersion cooling liquid, comprising the following steps:

[0036] (1) N-vinyl pyrrolidone, methacrylate monomer, molecular chain transfer agent and initiator are uniformly mixed and added dropwise into base oil, and copolymerization reaction is carried out at 60-160℃ for 3-10h; after the reaction is completed, the dispersant is prepared by reduced pressure filtration, alcohol washing and vacuum drying;

[0037] (2) The antioxidant and nano heat-conducting microparticles are added into the narrow-cut mineral base oil according to the formula proportion, and continuous stirring is carried out, the stirring temperature is 60-70℃, and the stirring time is 1-2h, to obtain product a;

[0038] (3) Add narrow-cut mineral base oil into the blending kettle, start stirring and heat to 70-80℃ and keep the temperature, add dispersant and anti-rust agent, continue stirring and reacting, stirring speed is 200-300r / min, stirring time is 1-2h, get product b;

[0039] (4) Finally, add product a into product b, continue stirring and reacting, stirring temperature is 55-60℃, stirring time is 1-2h, then get the immersion coolant composition.

[0040] The mechanism of each preparation step is as follows:

[0041] In the dispersant preparation step, N-vinyl pyrrolidone, methacrylate monomer, molecular chain transfer agent and initiator are mixed and then added dropwise into the base oil for copolymerization reaction. In this step, N-vinyl pyrrolidone contains a polar lactam group, monomer ester 1 group and monomer ester 2 group in the methacrylate monomer provide medium-short chain and lipophilic long chain structure respectively, the molecular weight is controlled by the molecular chain transfer agent α-methyl styrene dimer, and the initiator t-butyl peroxybenzoate initiates free radical polymerization. After reacting at 60-160℃ for 3-10h, a P(MAEs-co-NVP) copolymer with amphiphilic structure is formed. The polar groups on the molecular chain can form hydrogen bonds with the hydroxyl groups on the surface of the nano heat-conducting particles, and the non-polar long chain is compatible with the base oil, thereby laying a structural foundation for the subsequent stable dispersion of nano particles.

[0042] In the preparation of product a, the thio hindered phenol antioxidant and nano heat-conducting particles are added into the narrow-cut mineral base oil, and stirred at 60-70℃ for 1-2h. This temperature can promote the dissolution of the antioxidant in the base oil and avoid the agglomeration of the nano particles. The thio ether group and phenolic hydroxyl group of the thio hindered phenol antioxidant can synergistically terminate the oxidative chain reaction, and the nano heat-conducting particles provide core units for building a heat-conducting network by virtue of their high specific surface area and thermal conductivity under the action of stirring.

[0043] In the preparation of product b, the narrow-cut mineral base oil is heated to 70-80℃, and the dispersant and petroleum sodium sulfonate anti-rust agent are added, and stirred at 200-300r / min for 1-2h. This temperature range is conducive to the full dissolution of the dispersant and the exertion of its surface activity. The sulfonic acid group of the petroleum sodium sulfonate anti-rust agent not only provides anti-rust function, but also acts as a surfactant to reduce the surface tension of the system, and cooperates with the dispersant to improve the wettability of the base oil to the metal surface. The amphiphilic molecules of the dispersant form micellar structures in the base oil, preventing the aggregation of nano particles through steric hindrance and electrostatic repulsion, and their polar groups interact with the polar end of the anti-rust agent to enhance the stability of the emulsion system.

[0044] Finally, product a and product b are mixed and stirred at 55-60℃ for 1-2h, and this low-temperature stirring step avoids the destruction of the dispersion state of the nanoparticles at high temperature, promotes the full adsorption of the dispersant on the surface of the nanoparticles, and forms a stable ternary system of dispersant-nanoparticle-base oil. The synergistic effect of the hindered phenolic antioxidant and the polar groups in the dispersant further enhances the oxidation resistance of the system, and the nano-thermal-conducting particles guided by the dispersant construct a continuous thermal-conducting channel, combined with the low-viscosity characteristics of the narrow-fraction mineral base oil, to achieve the improvement of the heat dissipation performance.

[0045] The entire preparation process controls the temperature, time and stirring speed of each step to form a synergistic network of antioxidant, rust inhibitor, nano-thermal-conducting particles and dispersant in the narrow-fraction mineral base oil: the narrow-fraction mineral base oil provides a low-viscosity high-flash-point matrix, the hindered phenolic antioxidant inhibits oxidation, the sodium petroleum sulfonate ensures metal compatibility, the dispersant stabilizes the nanoparticles and constructs a thermal-conducting channel, and the nanoparticles improve the thermal conductivity. Through chemical action and physical structure synergy, a cooling liquid with excellent thermal performance, electrical insulation and safety is finally obtained. The selection of process parameters realizes the multiple optimization of dispersion stability, oxidation resistance and heat dissipation performance, and achieves technical effects that traditional mineral oil cooling liquids cannot achieve.

[0046] In order to make the present disclosure more complete, the following will be described by more specific examples.

[0047] I. Examples

[0048] Example 1:

[0049] Preparation steps:

[0050] (1) Dispersant synthesis: N-vinylpyrrolidone, octyl methacrylate (monomer ester 1 group), and hexadecyl methacrylate (monomer ester 2 group) are mixed at a molar ratio of 1:1:0.5, 1% of α-methylstyrene dimer and 1% of tert-butyl peroxybenzoate are added to the total amount of N-vinylpyrrolidone, octyl methacrylate and hexadecyl methacrylate monomers, and then dropped into the base oil, and copolymerization reaction is carried out at 120℃ for 6h, and then the dispersant P(MAEs-co-NVP) is obtained by vacuum filtration, alcohol washing and vacuum drying.

[0051] (2) Cooling liquid preparation: antioxidant and boron nitride are added to the narrow-fraction base mineral oil, and stirred at 60℃ for 1h to obtain product a; the narrow-fraction mineral base oil is heated to 70℃, and the dispersant and rust inhibitor are added, and stirred at 200r / min for 1h to obtain product b; product a and product b are mixed and stirred at 55℃ for 1h to obtain the cooling liquid.

[0052] Example 2:

[0053] Preparation step: adjust the content of antioxidant and dispersant, the molar ratio of monomer ester 1 group and monomer ester 2 group is 1:2:1 during the synthesis of dispersant, and the rest of the steps are the same as example 1.

[0054] Example 3:

[0055] Preparation step: replace boron nitride nanoparticles with aluminum nitride nanoparticles, increase the synthesis temperature of dispersant to 130℃, and the reaction time is 5h, and the rest of the steps are the same as example 1.

[0056] Example 4:

[0057] Preparation step: the molar ratio of N-vinyl pyrrolidone, monomer ester 1 group and monomer ester 2 group is 1:3:1.5 during the synthesis of dispersant, and the amount of initiator is increased to 2% of the total amount of N-vinyl pyrrolidone and methacrylate monomer, and the rest of the steps are the same as example 1. The cooling liquid with added nano heat-conducting particles prepared in this example is subjected to normal temperature standing test, and the test phenomenon is shown in Figure 1 , from which it can be observed that the cooling liquid remains in a non-precipitated state after 240 days of normal temperature standing, fully embodying the excellent dispersion stability of the dispersant to the nano heat-conducting particles. Figure 1

[0058] Example 5:

[0059] Preparation step: increase the stirring speed to 300r / min during the preparation of the cooling liquid, the mixing temperature of products a and b is 60℃, and the stirring time is 2h, and the rest of the steps are the same as example 1. The cooling liquid with added nano heat-conducting particles prepared in this example is subjected to normal temperature standing test, and the test phenomenon is shown in Figure 2 , from which it can be observed that the cooling liquid remains in a non-precipitated state after 240 days of normal temperature standing, fully embodying the excellent dispersion stability of the dispersant to the nano heat-conducting particles. Figure 2

[0060] Example 6:

[0061] Preparation step: increase the amount of molecular chain transfer agent to 2% of the total amount of N-vinyl pyrrolidone and methacrylate monomer during the synthesis of dispersant, the reaction temperature is 120℃, and the time is 4h, and the rest of the steps are the same as example 1.

[0062] Comparative example 1:

[0063] Preparation step: omit the addition of nanoparticles, and the rest of the steps are the same as example 4, which is used to verify the influence of nanoparticles on the heat dissipation performance.

[0064] Comparative example 2

[0065] Preparation step: replace the antioxidant with amine, and the rest of the steps are the same as example 3, which is used to compare the influence of antioxidant type on oxidation stability.​​

[0066] Comparative Example 3

[0067] Preparation steps: No rust inhibitor was added, and the remaining steps were the same as in Example 1, which was used to verify the effect of rust inhibitor on equipment compatibility.

[0068] Comparative Example 4

[0069] Preparation steps: The dispersant addition was omitted; boron nitride nanoparticles were directly mixed with the antioxidant. The remaining steps were the same as in Example 1, used to verify the effect of the dispersant on the stability of the nanoparticles. A room-temperature static test was conducted on the coolant containing the thermally conductive nanoparticles prepared in this comparative example. The experimental phenomena are as follows: Figure 3 As shown, from Figure 3 As can be observed, after 240 days of standing at room temperature, a large amount of precipitate was formed, which is in stark contrast to Examples 4 and 5, and intuitively demonstrates the key role of the dispersant in maintaining the stable dispersion of the nano-thermal conductive particles.

[0070] Comparative Example 5

[0071] Preparation steps: The base oil was replaced with uncut conventional mineral oil, and the remaining steps were the same as in Example 4, to compare the effect of narrow fraction cutting on viscosity and flash point.

[0072] The data center immersion coolant of the present invention and comparative examples is composed of the following components by mass percentage, and the specific formula is shown in Table 1.

[0073]

[0074] II. Experimental Results

[0075]

[0076] III. Summary

[0077] 1. The physicochemical properties of the data center immersion coolants of Examples 1-6 and Comparative Examples 1-5 were tested, and the test results are shown in the table. The volatility and viscosity of Examples 1-6 were lower than those of Comparative Example 5, indicating that narrow-fraction mineral base oils have better volatility than conventional mineral base oils, and their low viscosity allows for faster flow and cooling of the coolant.

[0078] 2, The electrical insulation performance of the data center immersion cooling liquid of examples 1-6 and comparative examples 1-5 was tested, and the test results are shown in the table. The breakdown voltage of examples 1-6 is higher than that of comparative example 4, which shows that the ester structure contained in the dispersant can improve the breakdown voltage of the cooling liquid; the volume resistivity of examples 4-6 is higher than that of comparative example 1, which shows that the nano-thermal-conductive microparticles can improve the resistivity of the cooling liquid. The volume resistivity of examples 4-6 is higher than that of comparative example 4, which shows that the dispersant can better disperse the nano-thermal-conductive microparticles in the cooling liquid, and the insulation performance of the cooling liquid is optimized, so that the high-frequency electronic components immersed in the cooling liquid will not significantly lose signal integrity.

[0079] 3, The insulation cooling liquid heat dissipation performance of the data center immersion cooling liquid of examples 1-6 and comparative examples 1-5 was tested, and the test results are shown in the table. The breakdown voltage of examples 1-6 is higher than that of comparative example 1, which shows that the nano-thermal-conductive microparticles can improve the heat dissipation performance of the cooling liquid. The volume resistivity of examples 4-6 is higher than that of comparative example 4, which shows that the dispersant can better disperse the nano-thermal-conductive microparticles in the cooling liquid, and the heat dissipation performance of the cooling liquid is optimized.

[0080] 5, The insulation cooling liquid heat dissipation performance of the data center immersion cooling liquid of examples 1-6 and comparative examples 1-5 was tested, and the test results are shown in the table. The breakdown voltage of examples 1-6 is higher than that of comparative example 1, which shows that the nano-thermal-conductive microparticles can improve the heat dissipation performance of the cooling liquid. The volume resistivity of examples 4-6 is higher than that of comparative example 4, which shows that the dispersant can better disperse the nano-thermal-conductive microparticles in the cooling liquid, and the heat dissipation performance of the cooling liquid is optimized. The dispersant and the nano-thermal-conductive microparticles have a synergistic effect. The nano-thermal-conductive microparticles have a large number of micro-particles with high energy, which can affect the thermal vibration of the liquid micro-particles and the number of micro-particles with high energy, thereby improving the thermal conductivity of the liquid.

[0081] 6, The oxidation stability of the data center immersion cooling liquid of examples 1-6 and comparative examples 1-5 was tested, and the test results are shown in the table. The antioxidant performance of examples 1-6 is better than that of comparative example 2, and the sulfur content of examples 1-6 is higher than that of comparative example 2. It shows that the sulfur-containing hindered phenol antioxidant can improve the antioxidant performance of the cooling liquid, and the sulfur-containing hindered phenol antioxidant strengthens the antioxidant performance of the narrow distillation range mineral base oil. The oxidation stability of examples 4-6 is better than that of comparative example 4, which shows that the dispersant can better disperse the high-temperature deposits, and the oxidation stability performance of the cooling liquid is optimized. The dispersant and the antioxidant have a synergistic effect.

[0082] 7. The safety and environmental friendliness of the data center immersion coolants in Examples 1-6 and Comparative Examples 1-5 were tested, and the test results are shown in the table. Examples 1-6 and Comparative Examples 1-5 contained no polychlorinated biphenyls (PCBs), and the content of polycyclic aromatic hydrocarbons (PCA) was extremely low. The flash point of Examples 1-6 was higher than that of Comparative Example 5, indicating that the flash point of narrow-fraction mineral base oil is superior to that of conventional mineral base oil. Flash point is a safety indicator for insulating coolants; a high flash point ensures the safety of storage, transportation, and operation of insulating coolants. Based on the viscosity and volatility of the physicochemical indicators, the above comparative data shows that narrow-fraction mineral base oils have the characteristics of low viscosity, high flash point, and low ash content, meeting the technical requirements for safety and heat dissipation performance of coolants.

[0083] Example 4, Example 5 and Comparative Example 4 were selected for static testing under different temperature gradients. The test results are shown in the table.

[0084]

[0085] As shown in Table 3, the coolant prepared in Comparative Example 4 became turbid after standing at room temperature for 30 days, and the amount of sediment increased further with the extension of standing time. The experimental phenomena are as follows. Figure 3 As shown in Tables 4 and 5, the coolant in Comparative Example 4 showed a small amount of precipitation after standing at low temperature for 30 days and at high temperature for 120 days. However, the coolants prepared in Examples 4 and 5 did not show any precipitation after standing for 240 days under different temperature conditions (room temperature, low temperature, and high temperature). These experimental results demonstrate that the coolant with added dispersant in this invention can effectively disperse and stabilize the thermally conductive nanoparticles, effectively avoiding the problem of agglomeration and precipitation of nanoparticles during long-term standing at different temperature environments.

[0086] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A narrow-fraction mineral base oil single-phase submerged coolant, characterized in that, Based on the total mass of the coolant, the raw materials include the following mass percentages: antioxidant 0.5%-3.0%, rust inhibitor 0.5%-3%, nano thermally conductive particles 1.0%-5%, dispersant 1.0%-5%, and the remainder is narrow-fraction mineral base oil.

2. The narrow-fraction mineral base oil single-phase submerged coolant according to claim 1, characterized in that, The narrow-fraction mineral base oil is produced by processing minerals with a viscosity of 2 mm at 100°C. 2 Group III base oils are distilled under reduced pressure at a rate of / s, with 10% to 90% of the distillate recovered. Less than 10% of the low flash point distillate and more than 90% of the high viscosity, high flash point distillate are removed, retaining a viscosity of 5.0 mm at 40℃. 2 / s~7mm 2 / s, distillate oil with a flash point of 155℃ or higher.

3. The narrow-fraction mineral base oil single-phase submerged coolant according to claim 1, characterized in that, The antioxidant mentioned is a thio-hindered phenol antioxidant.

4. The narrow-fraction mineral base oil single-phase submerged coolant according to claim 1, characterized in that, The rust inhibitor mentioned is sodium petroleum sulfonate.

5. The narrow-fraction mineral base oil single-phase submerged coolant according to claim 1, characterized in that, The aforementioned thermally conductive nanoparticles are one or more of boron nitride, silicon nitride, and aluminum nitride.

6. The narrow-fraction mineral base oil single-phase submerged coolant according to claim 1, characterized in that, The dispersant is a copolymer formed by the copolymerization reaction of methacrylate and N-vinylpyrrolidone, wherein the methacrylate comprises monomer ester group 1 and monomer ester group 2.

7. A narrow-fraction mineral base oil single-phase submerged coolant according to claim 6, characterized in that, The monomer ester group 1 is one or more of octyl methacrylate, isooctyl methacrylate, decyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, isotridecyl methacrylate, or tetradecyl methacrylate, and the monomer ester group 2 is one or more of hexadecyl methacrylate, octadecyl methacrylate, eicosyl methacrylate, dodecyl methacrylate, or tetradecyl methacrylate.

8. A narrow-fraction mineral base oil single-phase submerged coolant according to claim 6, characterized in that, The molar ratio of the N-vinylpyrrolidone, monomer ester group 1, and monomer ester group 2 is 1:(1-10):(0.5-8).

9. A method for preparing a narrow-fraction mineral base oil single-phase submerged coolant according to any one of claims 1-8, characterized in that, Includes the following steps: (1) N-vinylpyrrolidone, methacrylate monomer, molecular chain transfer agent and initiator are mixed evenly and added dropwise to narrow-fraction mineral base oil. The copolymerization reaction is carried out at 60-160℃ for 3-10h. After the reaction is completed, the dispersant is obtained by vacuum filtration, alcohol washing and vacuum drying. (2) Add antioxidant and nano thermally conductive particles to narrow-fraction mineral base oil in sequence according to the formula ratio, stir continuously at a temperature of 60-70℃ for 1-2 hours to obtain product a; (3) Add narrow-fraction mineral base oil to a blending vessel, start stirring and heat to 70-80℃ and maintain this temperature, add dispersant and rust inhibitor, continue stirring and reaction, stirring speed is 200-300r / min, stirring time is 1-2h, to obtain product b; (4) Finally, add product a to product b and continue stirring the reaction. The stirring temperature is 55-60℃ and the stirring time is 1-2h to obtain the immersion coolant composition.

10. The method for preparing a narrow-fraction mineral base oil single-phase submerged coolant according to claim 9, characterized in that, Step (1) The copolymerization reaction includes a chain transfer agent and an initiator. The chain transfer agent is α-methylstyrene dimer, and the amount added is 0.5%-6% of the total amount of N-vinylpyrrolidone and methacrylate monomers. The initiator is one or more of tert-butyl peroxide, azodicyanovalerate, azobisisobutyronitrile, benzoyl peroxide, and azobisisoheptane, and the amount added is 0.5%-6% of the total amount of N-vinylpyrrolidone and methacrylate monomers.

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