Composite immersed cooling liquid as well as preparation method and application thereof

Abstract

The invention provides a composite immersed cooling liquid as well as a preparation method and application thereof. Comprising a dispersion phase, a continuous phase, an emulsifier and an additive, the dispersion phase is fluorine cooling liquid, the continuous phase is oil cooling liquid, the emulsifier is one or more compounded nonionic surfactants, and the HLB value of the emulsifier is 4-9 or 10-18; according to the composite immersed cooling liquid disclosed by the invention, the advantages of high heat conductivity of the oil phase and high safety (non-combustibility and high dielectric strength) of the fluorine phase are ingeniously combined, and 1 + 1gt is realized; 2, the effect is achieved; the oil phase with high cost performance is used for replacing most expensive fluorine phases, and the overall material cost is reduced by 40%-60% compared with that of pure fluorine cooling liquid; the nano-scale microemulsion is formed through the specific emulsifier, the fundamental problem that a traditional mixed solution is inevitably layered is solved, and the shelf life is long; the cooling liquid disclosed by the invention has good material compatibility, and the problem that a pure fluorine liquid swells some sealing materials is avoided.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cooling liquids, and particularly relates to a composite immersion cooling liquid and a preparation method and application thereof. BACKGROUND

[0002] The immersion liquid cooling technology is an effective solution to the heat dissipation problem of high-power-density electronic equipment. The mainstream cooling liquids on the market can be divided into two categories:

[0003] Fluorine-based cooling liquids, such as perfluoropolyether (PFPE), hydrofluoroether (HFE), and hydrofluoroolefin (HFO). The advantages of fluorine-based cooling liquids are high chemical inertness, non-flammability, high dielectric strength, and low volatility. However, the disadvantages are also very prominent: extremely high cost, relatively poor thermal conductivity, and environmental unfriendliness (partially high GWP value, GWP value: global warming potential).

[0004] Oil-based cooling liquids, such as mineral oil, silicone oil, and synthetic ester. The advantages of oil-based cooling liquids are low cost, better thermal conductivity than fluorine-based liquids, and good biodegradability (partially synthetic ester). However, the disadvantages are also obvious: usually high viscosity (leading to large pumping resistance), flammability, possible decrease in dielectric strength over time or water absorption, and poor compatibility with certain materials.

[0005] If oil liquid and fluorine liquid are simply physically mixed, due to the differences in surface tension, density and polarity, phase separation will occur, forming two layers of liquid, which seriously damages the uniformity and heat dissipation performance of the cooling liquid, and may cause safety hazards due to local component differences.

[0006] Therefore, those skilled in the art have been seeking a solution to combine the advantages of high thermal conductivity and low cost of oil liquid with the advantages of high safety and high stability of fluorine liquid to form a uniform, stable and high-performance composite cooling liquid, but have always faced the core problem of solving phase separation. SUMMARY

[0007] In order to solve the defects in the prior art, the application provides a composite immersion cooling liquid and a preparation method and application thereof. The composite immersion cooling liquid of the application forms a thermodynamically stable, nanoscale dispersed microemulsion of originally incompatible oil-based cooling liquid and fluorine-based cooling liquid through a unique formula and process, thereby having the characteristics of high thermal conductivity, low cost, high safety and long service life, and being suitable for heat dissipation of devices such as data centers, power electronics and energy storage.

[0008] The application adopts the following technical solutions:

[0009] In a first aspect, the application provides a composite immersion cooling liquid, which comprises the following components by mass fraction:

[0010] Dispersed phase: 15-45%;

[0011] Continuous phase: 50-80%;

[0012] Emulsifier: 3-15%;

[0013] Additives: 0.1–5%;

[0014] Wherein, the dispersed phase is a fluorine-based coolant, and the continuous phase is an oil-based coolant;

[0015] The hydrophilic-lipophilic balance value of the emulsifier is 4 to 9, or the hydrophilic-lipophilic balance value of the emulsifier is 10 to 18.

[0016] Preferably, the fluorinated coolant includes at least one of perfluoropolyether, hydrofluoroether, and hydrofluoroolefin.

[0017] Preferably, the oil-based coolant includes at least one of mineral oil, alkylbenzene synthetic oil, silicone oil, synthetic ester, and natural ester insulating oil.

[0018] Preferably, the emulsifier comprises a perfluoropolyether-based surfactant or a compound of sorbitan fatty acid ester and polyoxyethylene sorbitan fatty acid ester.

[0019] Preferably, the additive includes at least one of an antioxidant, a corrosion inhibitor, and a coupling agent;

[0020] The antioxidants include hindered phenolic antioxidants or aromatic amine antioxidants;

[0021] The corrosion inhibitors include benzotriazole or thiadiazole derivatives;

[0022] The coupling agent is a silane coupling agent.

[0023] Preferably, the composite immersion coolant contains 0.2-1.5% by mass of antioxidant, 0.2-1.5% by mass of corrosion inhibitor, and 0-2% by mass of coupling agent.

[0024] Secondly, the present invention also provides a method for preparing the aforementioned composite immersion coolant, comprising the following steps:

[0025] After mixing the continuous phase with the emulsifier, the dispersed phase is added and stirred to obtain a mixture;

[0026] The mixture was homogenized in a homogenizer to obtain a microemulsion;

[0027] Additives were added to the microemulsion and stirred to obtain a composite immersion coolant.

[0028] Preferably, the continuous phase and the emulsifier are mixed at 40-60°C, and then the dispersed phase is added and stirred at 5000-10000 rpm to obtain a mixture.

[0029] Preferably, the mixture is homogenized in a homogenizer at 50-100 MPa 2-4 times to obtain a microemulsion;

[0030] Additives are added to the microemulsion and stirred at 200-500 rpm to obtain a composite immersion coolant.

[0031] Thirdly, the present invention also provides an application of the composite immersion coolant or the composite immersion coolant prepared by the preparation method described above in a single-phase immersion cooling system.

[0032] The composite immersion coolant, its preparation method, and its application of the present invention have the following advantages compared to the prior art:

[0033] 1. The composite immersion coolant of the present invention comprises a dispersed phase, a continuous phase, an emulsifier, and additives. The dispersed phase is a fluorinated coolant, the continuous phase is an oil-based coolant, and the emulsifier is one or more compounded nonionic surfactants with a hydrophilic-lipophilic balance value (HLB value) of 4-9 (suitable for oil-in-fluorine type) or 10-18 (suitable for water-in-oil type). The composite immersion coolant of the present invention, through a specific emulsifier, enables the originally incompatible oil-based coolant and fluorinated coolant to form a thermodynamically stable (stable in a temperature range of -40℃ to 80℃, without phase separation) nanoscale (droplet particle size distribution between 10 and 100 nanometers, appearance as a translucent or transparent liquid) microemulsion, thus possessing the characteristics of high thermal conductivity, low cost, high safety, and long life, and is suitable for heat dissipation of data centers, power electronics, energy storage and other equipment.

[0034] 2. The composite immersion coolant of this invention cleverly combines the advantages of high thermal conductivity of the oil phase and high safety (non-flammable, high dielectric strength) of the fluorine phase, achieving a 1+1>2 effect; this invention uses a cost-effective oil phase to replace most of the expensive fluorine phase, reducing the overall material cost by 40%-60% compared to pure fluorine coolant; this invention uses a specific emulsifier to form a nanoscale microemulsion, solving the fundamental problem of inevitable stratification in traditional mixtures, resulting in a long shelf life; the coolant of this invention has good material compatibility: the external continuous phase (oil phase) has better compatibility with common materials in electronic devices such as metals, plastics, and elastomers, avoiding the swelling problem of pure fluorine liquid on certain sealing materials. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a particle size distribution diagram of the composite immersion coolant in Example 1;

[0037] Figure 2 The image shows the appearance of the composite immersion coolant in Example 1;

[0038] Figure 3 This is an image showing the appearance of the coolant in Comparative Example 1. Detailed Implementation

[0039] To facilitate understanding of the present invention, a more comprehensive description of the invention will be provided below in conjunction with specific embodiments. Preferred embodiments of the invention are given in the specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0040] The order in which the embodiments are described below is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0041] This invention provides a composite immersion coolant comprising the following components by mass fraction:

[0042] Dispersed phase: 15–45%;

[0043] Continuous phase: 50-80%;

[0044] Emulsifier: 3-15%;

[0045] Additives: 0.1–5%;

[0046] The dispersed phase is a fluorinated coolant, and the continuous phase is an oil-based coolant.

[0047] The hydrophilic-lipophilic balance value of the emulsifier is 4 to 9, or the hydrophilic-lipophilic balance value of the emulsifier is 10 to 18.

[0048] The composite immersion coolant of the present invention comprises a dispersed phase, a continuous phase, an emulsifier, and additives. The dispersed phase is a fluorinated coolant, the continuous phase is an oil-based coolant, and the emulsifier is one or more compounded nonionic surfactants with a hydrophilic-lipophilic balance value (HLB value) in the range of 4-9 (applicable to oil-in-fluorine type) or 10-18 (applicable to water-in-oil type). The composite immersion coolant of the present invention, through a specific emulsifier, enables the originally incompatible oil-based coolant and fluorinated coolant to form a thermodynamically stable, nanoscale dispersed microemulsion, thereby possessing the characteristics of high thermal conductivity, low cost, high safety, and long life, and is suitable for heat dissipation of equipment such as data centers, power electronics, and energy storage.

[0049] The composite immersion coolant of the present invention has the following advantages:

[0050] (1) Performance Synergy: It cleverly combines the advantages of high thermal conductivity of oil phase and high safety (non-flammable, high dielectric strength) of fluorine phase, achieving a 1+1>2 effect.

[0051] (2) Cost optimization: The high-performance oil phase replaces most of the expensive fluorine phase, and the overall material cost is reduced by 40%-60% compared with pure fluorine coolant.

[0052] (3) Excellent stability: Through specific emulsifiers, nanoscale microemulsions are formed, which solves the fundamental problem that traditional mixtures inevitably separate into layers and has a long shelf life.

[0053] (4) Good material compatibility: The external continuous phase (oil phase) is more compatible with common materials such as metals, plastics and elastomers in electronic devices, avoiding the swelling problem of pure fluorine liquid on some sealing materials.

[0054] In some embodiments, the fluorinated coolant includes at least one of perfluoropolyether (PFPE), hydrofluoroether (HFE), and hydrofluoroolefin (HFO).

[0055] In some embodiments, the oil-based coolant includes at least one of mineral oil, alkylbenzene synthetic oil, silicone oil, synthetic ester, and natural ester insulating oil.

[0056] In some embodiments, the emulsifier includes a perfluoropolyether-based surfactant or a compound of sorbitan fatty acid ester and polyoxyethylene sorbitan fatty acid ester.

[0057] In some embodiments, the additive includes at least one of an antioxidant, a corrosion inhibitor, and a coupling agent;

[0058] In some embodiments, antioxidants include hindered phenolic antioxidants (such as 2,6-di-tert-butyl-p-cresol (BHT)) or aromatic amine antioxidants.

[0059] In some embodiments, corrosion inhibitors include benzotriazole or thiadiazole derivatives;

[0060] In some embodiments, the coupling agent is a silane coupling agent.

[0061] In some embodiments, the composite immersion coolant contains 0.2-1.5% by mass of antioxidant, 0.2-1.5% by mass of corrosion inhibitor, and 0-2% by mass of coupling agent.

[0062] The composite immersion coolant of the present invention is in the form of a microemulsion, with droplet size distribution between 10 and 100 nanometers. It is a semi-transparent or transparent liquid and remains stable in a temperature range of -40°C to 80°C without phase separation.

[0063] Based on the same inventive concept, the present invention also provides a method for preparing the above-mentioned composite immersion coolant, comprising the following steps:

[0064] S1. After mixing the continuous phase with the emulsifier, add the dispersed phase and stir to obtain a mixture;

[0065] S2. The mixture is homogenized in a homogenizer to obtain a microemulsion;

[0066] S3. Add the additive to the microemulsion and stir to obtain a composite immersion coolant.

[0067] In some embodiments, the continuous phase and the emulsifier are mixed at 40–60°C, and then the dispersed phase is added and stirred at 5000–10000 rpm to obtain a mixture.

[0068] In some embodiments, the mixture is homogenized in a homogenizer at 50-100 MPa 2-4 times to obtain a microemulsion;

[0069] Additives are added to the microemulsion and stirred at 200-500 rpm to obtain a composite immersion coolant.

[0070] In some embodiments, the preparation method of the composite immersion coolant of the present invention includes the following steps:

[0071] S1. Mix the oil-based coolant (continuous phase) and emulsifier evenly at 40-60℃, and then add the fluorine-based coolant (dispersed phase) under high-speed shearing (shear rate 5000~10000rpm) stirring to obtain a mixture;

[0072] S2. The mixture is passed through a high-pressure homogenizer and circulated 2 to 4 times under a pressure of 50 to 100 MPa until a uniform and stable microemulsion is formed.

[0073] S3. After cooling to 20-30℃, add performance additives such as antioxidants and corrosion inhibitors, and stir at low speed (200-500rpm) until completely dissolved to obtain a composite immersion coolant.

[0074] The preparation method of the composite immersion coolant of the present invention adopts the above-mentioned process, especially the homogenization treatment under a pressure of 50-100 MPa, to prepare the composite immersion coolant; the coolant is a microemulsion in the form of a coolant, and the average particle size of the dispersed phase droplets is 10-100 nanometers; the present invention solves the core problem existing in the prior art - phase separation: the present invention is not a simple mixing, but creatively introduces microemulsion technology into the field of immersion cooling; the biggest breakthrough of the present invention is that through a specific emulsifier system (such as Span / Tween compound) and high-pressure homogenization process, a thermodynamically stable microemulsion with a nanoscale particle size (10-100 nm) is formed, which completely solves the problem of stratification; the composite immersion coolant of the present invention has the "hybrid" advantage of performance: achieving the effect of "1+1>2".

[0075] The composite immersion coolant of this invention exhibits excellent safety, determined by the external phase (continuous phase). The continuous phase is an oil phase, thus exhibiting the high flash point of an oil phase overall; simultaneously, the presence of an internal fluorine phase further enhances safety.

[0076] The composite immersion coolant of the present invention has good thermal conductivity: it is dominated by a high thermal conductivity oil phase as the continuous phase, and its overall thermal conductivity is far superior to that of pure fluorine liquid.

[0077] The composite immersion coolant of this invention has low cost: by replacing the expensive fluorine phase with a large amount of inexpensive oil phase, the cost is significantly reduced.

[0078] The composite immersion coolant of this invention has good compatibility: the equipment mainly contacts the external phase (oil phase), which avoids the swelling problem that pure fluorine liquid may cause to some sealing materials, and thus has better compatibility.

[0079] Based on the same inventive concept, the present invention also provides an application of the above-mentioned composite immersion coolant or the composite immersion coolant prepared by the above-mentioned preparation method in a single-phase immersion cooling system.

[0080] Specifically, a single-phase immersion cooling system is a system that directly and completely immerses heat-generating electronic devices in a liquid coolant, removing heat through the sensible heat exchange of the coolant, and the coolant does not undergo a phase change throughout the process (remaining in a liquid state). Because two-phase systems require boiling, and microemulsions may compromise stability, their application scenarios need to be clearly defined. Specifically, the composite immersion coolant of this invention is suitable for heat dissipation in data centers, power electronics, energy storage, and other equipment.

[0081] The following detailed embodiments further illustrate the composite immersion coolant of the present invention, its preparation method, and its application. This section further explains the invention in conjunction with specific embodiments, but should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0082] In the following examples and comparative examples, the natural ester insulating oil is Depuxi natural ester insulating oil (purchased from Jiangsu Shuangjiang Energy Technology Co., Ltd.). Depuxi natural ester insulating oil is a natural ester plant-based transformer oil produced by purifying natural oil esters derived from plants using patented technology (patent name: A natural ester transformer oil and its preparation method, patent number: ZL 202010908706.3). It is a renewable resource.

[0083] Example 1

[0084] This embodiment provides a composite immersion coolant, comprising the following components:

[0085] Dispersed phase: 25 kg hydrofluoroether (HFE-7100, chemical formula C5H3F9O, Chinese name is methyl nonafluorobutyl ether);

[0086] Continuous phase: 70kg natural ester insulating oil;

[0087] Emulsifier: 4.5 kg (The emulsifier is a mixture of Span 80 and Tween 80 in a mass ratio of 4:1, with an HLB value of 7.5);

[0088] Additives: including 0.5 kg of antioxidant (2,6-di-tert-butyl-p-cresol (BHT)) and 0.3 kg of benzotriazole (BTA, corrosion inhibitor);

[0089] The mass fractions of the components of the above-mentioned composite immersion coolant are as follows: continuous phase synthetic ester (Mobil ETRO 20) 69.791%, dispersed phase hydrofluoroether (HFE-7100) 24.925%, emulsifier 4.487%, antioxidant (2,6-di-tert-butyl-p-cresol (BHT)) 0.499%, and corrosion inhibitor (benzotriazole (BTA)) 0.299%.

[0090] The preparation method of the above-mentioned composite submersible coolant includes the following steps:

[0091] S1. The synthetic ester (Mobil ETRO 20) and emulsifier were mixed at 50°C, and then hydrofluoroether (HFE-7100) was added and stirred at 8000 rpm for 1 hour to obtain a mixture.

[0092] S2. Place the mixture in a homogenizer at 75 MPa and homogenize it three times to obtain a microemulsion.

[0093] S3. After cooling the microemulsion to 30°C, add antioxidant (BHT) and corrosion inhibitor (BTA), and stir at 200 rpm for 30 min to obtain a composite immersion coolant.

[0094] Comparative Example 1

[0095] This comparative example provides a method for preparing a coolant, including the following steps:

[0096] Equal amounts of 70 kg of Depus natural ester insulating oil and 25 kg of hydrofluoroether (HFE-7100) were stirred at 8000 rpm for 1 hour to obtain a coolant, which quickly separated into layers after standing.

[0097] Performance testing

[0098] The performance of the composite immersion coolant in Example 1, as well as pure Depus natural ester insulating oil and pure HFE-7100, was tested, and the results are shown in Table 1 below.

[0099] Table 1 - Performance test results of composite immersion coolant, pure synthetic ester, and pure HFE-7100 in Example 1

[0100]

[0101] The fact that pure HFE-7100 has no flash point in Table 1 means that this substance does not have a measurable flash point, i.e., it is a non-flammable fluid.

[0102] As can be seen from Table 1, the present invention has successfully prepared a stable composite immersion coolant with a thermal conductivity significantly higher than that of pure fluorine liquid HFE7100 and slightly better than that of pure oil phase (Depus natural ester insulating oil). This is due to the enhanced heat conduction caused by the interface effect of nanodroplets. The safety of the composite immersion coolant of the present invention is jointly guaranteed by the continuous phase oil liquid (high flash point) and the dispersed phase fluorine liquid (non-flammable), exhibiting an extremely high flash point and significantly optimizing the cost.

[0103] In Example 1, the composite immersion coolant is a microemulsion coolant, and its particle size distribution is shown in the figure. Figure 1 As shown; the test method is as follows: at a temperature of 25℃, the nanoparticle size analyzer Nano ZS of Malvern Zetasizer is used for measurement.

[0104] from Figure 1 As can be seen, the Z-Average (average particle size) is 52.8 nm, indicating that the average hydraulic diameter of the microemulsion droplets is approximately 52.8 nanometers, which is at the nanoscale and a typical characteristic of microemulsions. The PDI (polydispersity index) is 0.152. The smaller the PDI value, the more uniform the droplet size distribution. A PDI value of 0.152 indicates that the droplet size in this microemulsion is relatively uniform, and the system has good stability. The particle size distribution curve shows a single peak, indicating that the microemulsion droplets are mainly concentrated around a specific particle size range, further confirming the relatively uniform particle size distribution of this microemulsion.

[0105] Figure 2 The image shows the appearance of the composite immersion coolant in Example 1. Figure 3 This is an image showing the appearance of the coolant in Comparative Example 1.

[0106] from Figure 2 As can be seen from the data, the composite immersion coolant in Example 1 forms a uniform, non-layered microemulsion; while the coolant in Comparative Example 1 is a two-phase layer.

[0107] Further thermal stability tests were conducted on the composite immersion coolant in Example 1 to verify its reliability under extreme temperatures. The specific test method is as follows:

[0108] High-temperature test: The sample was stored in an 80℃ oven for 30 days. After the test, the sample remained semi-transparent, without any layering or precipitation. The particle size was tested, and the average particle size changed from the initial 52.8 nm to 55.1 nm, a change rate of 4.4%. The PDI value was still less than 0.2, indicating that the microstructure of the system was stable.

[0109] Low-temperature test: The sample was stored at -40℃ for 30 days. The sample did not completely solidify and still had a certain degree of fluidity. After returning to room temperature, its appearance, transparency, and fluidity immediately returned to their initial state, without any phase separation.

[0110] High and low temperature cycling test: The sample was tested for 20 cycles (-40℃ to 80℃, 8 hours each), and the test results are shown in Table 2.

[0111] Table 2 - Results of thermal stability tests on the composite immersion coolant in Example 1

[0112] Test item Initial state State after 20 cycles Change rate Appearance Translucent, uniform Translucent, uniform No change Average particle size (nm) 52.8 56.5 +7.0％ PDI 0.152 0.183 +20.4％ Transmittance (660 nm, %) 78.5 76.2 -2.9％

[0113] The above data proves that the composite immersion coolant prepared by this invention has excellent thermodynamic stability in an extreme temperature range of -40℃ to 80℃, and can meet the requirements for long-term use in harsh environments.

[0114] It is understood that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] The above are merely preferred embodiments of this application, and only specifically describe the technical principles of this application. These descriptions are only for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, as well as other specific embodiments of this application that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of this application.

Claims

1. A composite immersion coolant, characterized in that, Components including the following mass fractions: Dispersed phase: 15–45%; Continuous phase: 50-80%; Emulsifier: 3-15%; Additives: 0.1–5%; Wherein, the dispersed phase is a fluorine-based coolant, and the continuous phase is an oil-based coolant; The hydrophilic-lipophilic balance value of the emulsifier is 4 to 9, or the hydrophilic-lipophilic balance value of the emulsifier is 10 to 18.

2. The composite immersion coolant as described in claim 1, characterized in that, The fluorinated coolant includes at least one of perfluoropolyether, hydrofluoroether, and hydrofluoroolefin.

3. The composite immersion coolant as described in claim 1, characterized in that, The oil-based coolant includes at least one of mineral oil, alkylbenzene synthetic oil, silicone oil, synthetic ester, and natural ester insulating oil.

4. The composite immersion coolant as described in claim 1, characterized in that, The emulsifier includes a perfluoropolyether-based surfactant or a compound of sorbitan fatty acid ester and polyoxyethylene sorbitan fatty acid ester.

5. The composite immersion coolant as described in claim 1, characterized in that, The additives include at least one of antioxidants, corrosion inhibitors, and coupling agents; The antioxidants include hindered phenolic antioxidants or aromatic amine antioxidants; The corrosion inhibitors include benzotriazole or thiadiazole derivatives; The coupling agent is a silane coupling agent.

6. The composite immersion coolant as described in claim 5, characterized in that, The composite immersion coolant contains 0.2-1.5% antioxidant, 0.2-1.5% corrosion inhibitor, and 0-2% coupling agent by mass.

7. A method for preparing a composite immersion coolant as described in any one of claims 1 to 6, characterized in that, Includes the following steps: After mixing the continuous phase with the emulsifier, the dispersed phase is added and stirred to obtain a mixture; The mixture was homogenized in a homogenizer to obtain a microemulsion; Additives were added to the microemulsion and stirred to obtain a composite immersion coolant.

8. The method for preparing the composite immersion coolant as described in claim 7, characterized in that, The continuous phase and emulsifier are mixed at 40–60°C, and then the dispersed phase is added. The mixture is stirred at 5000–10000 rpm to obtain a mixture.

9. The method for preparing the composite immersion coolant as described in claim 7, characterized in that, The mixture was homogenized in a homogenizer at 50–100 MPa 2–4 ​​times to obtain a microemulsion. Additives are added to the microemulsion and stirred at 200-500 rpm to obtain a composite immersion coolant.

10. The application of a composite immersion coolant as described in any one of claims 1 to 6 or a composite immersion coolant prepared by any one of claims 7 to 9 in a single-phase immersion cooling system.

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