A coolant and its application in an immersion liquid-cooled energy storage system

Abstract

This invention belongs to the field of coolant technology, specifically relating to a coolant and its application in an immersion liquid-cooled energy storage system. The coolant, by weight, comprises 80-95 parts base oil, 1-5 parts thermally conductive nanoparticles, 0.5-2 parts composite dispersant, 0.3-1 part composite corrosion inhibitor, 0.1-0.5 parts antioxidant, 0.2-0.5 parts pour point depressant, and 0.01-0.05 parts defoamer. The base oil is a mixture of polyalphaolefin and synthetic ester, and the composite dispersant is a compound of polyisobutylene succinimide and Mannich base dispersant. Aging tests show that this coolant exhibits high thermal conductivity retention, low acid value increase, and low corrosion rate. The coolant of this invention can effectively maintain the dispersion stability of nanoparticles in the environment of precipitates from sealing materials, extending the fluid change cycle.

Description

Technical Field

[0001] This invention relates to the field of coolant preparation technology, and more specifically, to coolants and their application in immersion liquid-cooled energy storage systems. Background Technology

[0002] Immersion liquid cooling technology is gradually becoming one of the mainstream heat dissipation solutions in fields such as data centers, energy storage power stations, and electric vehicles due to its excellent temperature uniformity, high protection level, and low energy consumption. In immersion liquid cooling systems, the coolant is in direct contact with electronic components, metal connectors, and sealing materials for extended periods, requiring it to simultaneously possess high thermal conductivity, high insulation, wide temperature range adaptability, good material compatibility, and long-term stability.

[0003] To improve the thermal conductivity of coolants, the industry has widely experimented with adding high thermal conductivity nanoparticles such as boron nitride and aluminum nitride to base oils. However, nanoparticles are prone to agglomeration and sedimentation in non-polar base oils, which can lead to a significant decrease in the thermal conductivity of the coolant after long-term system operation. Currently, the industry is exploring ways to mitigate this problem by adding dispersants and modifying the surface of nanoparticles, with some success.

[0004] Some immersion liquid cooling systems use rubber seals such as nitrile rubber and fluororubber to prevent media leakage. However, during use, these rubber seals may release low-molecular-weight substances such as plasticizers. These precipitates are highly polar and easily compete with dispersants for adsorption on the surface of nanoparticles, thereby weakening the stabilizing effect of the dispersant on the nanoparticles and even causing the nanoparticles to re-aggregate, affecting the thermal conductivity of the coolant.

[0005] While assembling an energy storage system for an oilfield drilling platform, the applicant discovered that after a period of operation, the coolant darkened in color, its acid value increased, and the sealing rings showed signs of aging and hardening. Composition analysis of the old coolant revealed plasticizer residues. This proves that some plasticizers have indeed migrated from the sealing rings into the coolant, and their potential negative impact on coolant performance cannot be ignored.

[0006] Therefore, developing coolants that can more effectively resist the interference of precipitates is of great significance for ensuring the long-term stable operation of immersion liquid cooling systems under certain operating conditions. Summary of the Invention

[0007] One objective of this invention is to solve the problem of nanoparticle sedimentation caused by the precipitates of sealing materials in existing immersion coolants during long-term operation, and to provide a coolant that can maintain the long-term stable dispersion of nanoparticles, as well as its preparation method and application.

[0008] In a first aspect, the present invention provides a coolant comprising, by weight parts: 80-95 parts base oil, 1-5 parts thermally conductive nanoparticles, 0.5-2 parts composite dispersant, 0.3-1 parts composite corrosion inhibitor, 0.1-0.5 parts antioxidant, 0.2-0.5 parts pour point depressant, and 0.01-0.05 parts defoamer.

[0009] Wherein, according to the mass parts of the components in the coolant composition: Optionally, the base oil can be 80 parts, 81 parts, 82 parts, 83 parts, 84 parts, 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, 91 parts, 92 parts, 93 parts, 94 parts, or 95 parts.

[0010] Optionally, the thermally conductive nanoparticles can be 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, or 5 parts.

[0011] Optionally, the composite dispersant can be 0.5 parts, 0.6 parts, 0.8 parts, 1.0 parts, 1.2 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.8 parts, or 2.0 parts.

[0012] Optionally, the composite corrosion inhibitor can be 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, or 1.0 parts.

[0013] Optionally, the antioxidant can be 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, or 0.5 parts.

[0014] Optionally, the pour point depressant can be 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, or 0.5 parts.

[0015] Optionally, the defoamer can be 0.01 parts, 0.015 parts, 0.02 parts, 0.025 parts, 0.03 parts, 0.035 parts, 0.04 parts, 0.045 parts, or 0.05 parts.

[0016] base oil The base oil is the continuous phase of the coolant, and its properties affect the coolant's thermal conductivity, insulation, and low-temperature fluidity. This invention uses a mixture of polyalphaolefin base oil and synthetic ester, wherein the polyalphaolefin base oil accounts for 70%–90% by mass, and the synthetic ester accounts for 10%–30% by mass.

[0017] Pure polyalphaolefin base oils possess extremely low pour points, excellent high-temperature stability, and high volume resistivity, but have poor additive solubility. Synthetic esters can improve the thermal conductivity and additive solubility of blended base oils, but excessive amounts can reduce insulation performance. Examples show that, using the above proportions, the coolant exhibits high volume resistivity, good thermal conductivity, and good additive solubility.

[0018] In some specific embodiments, the polyalphaolefin base oil is selected from at least one of PAO2, PAO4, and PAO6, preferably PAO4 (kinematic viscosity 18 cSt at 40°C), and the synthetic ester is selected from one or more of pentaerythritol tetraester, trimethylolpropane triester, and diisooctyl adipate, preferably pentaerythritol tetraester.

[0019] Thermally conductive nanoparticles The thermally conductive nanoparticles are used to improve the thermal conductivity of the coolant. This invention uses boron nitride nanosheets or aluminum nitride nanoparticles, both of which have high thermal conductivity and high insulation properties. Unmodified nanoparticles tend to agglomerate and settle in non-polar base oils. This invention uses a silane coupling agent to modify the surface of the nanoparticles, improving their compatibility with the base oil.

[0020] The particle size of thermally conductive nanoparticles affects their dispersion stability and thermal conductivity in coolants. When the particle size is too small, the specific surface area is too large, making agglomeration difficult to avoid; when the particle size is too large, the particle settling rate is accelerated, and long-term stability decreases. Therefore, a particle size range of 50–200 nm is preferred. In some specific embodiments, boron nitride nanosheets with an average particle size of 80 nm are selected.

[0021] Composite dispersant The thermally conductive nanoparticles can maintain long-term stable dispersion through a dispersant. This invention uses a composite dispersant prepared by compounding polyisobutylene succinimide (PIBSI) with a Mannich base dispersant. The PIBSI has a number-average molecular weight of 800–2000 and an amine value of 20–80 mgKOH / g. Too low a molecular weight results in insufficient steric hindrance, while too high a molecular weight reduces the relative content of polar end groups. Too low an amine value results in insufficient adsorption sites, while too high an amine value may affect insulation due to excessive polarity. The Mannich base dispersant is a condensation product of alkylphenols, formaldehyde, and polyamines. Examples of this invention show that, under the same total dosage, the coolant using the composite dispersant, after accelerated aging tests simulating sealant precipitates, exhibits higher thermal conductivity retention and lower acid value increase, superior to coolants using only PIBSI and other types of dispersants.

[0022] Composite corrosion inhibitor Coolant is in long-term contact with metal components (copper, aluminum), requiring the addition of corrosion inhibitors to prevent corrosion. This invention uses a composite corrosion inhibitor made from a benzotriazole derivative and a silane ester. Specifically, the benzotriazole derivative is 5-hexyl-1H-benzotriazole, and the silane ester is tetraethoxysilane, with a mass ratio of 1:0.2–2. Examples show that coolant using this composite corrosion inhibitor exhibits a low aluminum corrosion rate, meeting the metal protection requirements of immersion liquid cooling systems.

[0023] Other additives The antioxidant is 2,6-di-tert-butyl-p-cresol, used to inhibit high-temperature oxidation of the base oil. In some specific embodiments, the antioxidant is present in parts by weight of 0.2 to 0.3 parts.

[0024] The pour point depressant is polymethyl methacrylate, used to lower the pour point and ensure low-temperature fluidity. In some specific embodiments, the pour point depressant is 0.3 to 0.4 parts by weight.

[0025] The defoamer is a silicone polyether used to suppress foam formation. In some specific embodiments, the defoamer is present in parts by weight of 0.02 to 0.03 parts.

[0026] Secondly, the present invention provides a method for preparing the above-mentioned coolant, comprising the following steps: S1. Mix the base oil, pour point depressant, and antioxidant, and heat to 50-60°C while stirring to dissolve. S2. Take 5% to 10% of the total volume of the mixture obtained in S1, add the composite corrosion inhibitor and composite dispersant, and mix evenly. S3. Add the thermally conductive nanoparticles to the mixture obtained in S2, disperse them ultrasonically for 15-30 min, and then disperse them by high-speed shearing. S4. Mix the dispersion obtained in S3 with the remaining mixture in S1, add defoamer, stir for 30-60 minutes, filter, and obtain coolant.

[0027] In some specific embodiments, the high-speed shearing speed in step S3 is 3000-5000 rpm, and the time is 20-40 min; a 1 μm filter element is used for filtration.

[0028] Thirdly, the present invention provides the application of the above-mentioned coolant in data centers, energy storage power stations or electric vehicle immersion liquid cooling systems.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects: 1) The coolant of this invention uses a mixture of polyalphaolefin base oil and synthetic ester as the base oil, with added thermally conductive nanoparticles modified by a silane coupling agent, and employs a composite dispersant of polyisobutylene succinimide and Mannich base dispersants. Experiments have demonstrated that this coolant possesses high thermal conductivity, high insulation, and good low-temperature fluidity, with high volume resistivity, good thermal conductivity, and a low pour point, making it suitable for immersion liquid cooling systems in data centers, energy storage power stations, and electric vehicles.

[0030] 2) This invention uses a composite dispersant of polyisobutylene succinimide and Mannich base dispersants, which effectively maintains the dispersion stability of nanoparticles. Through simulated aging tests of sealant precipitates, the coolant of this invention exhibits higher thermal conductivity retention, lower acid value increase, and no nanoparticle sedimentation, demonstrating superior performance compared to coolants using a single dispersant. It is particularly suitable for immersion liquid cooling systems where interference from sealant precipitates exists. Detailed Implementation

[0031] The technical solutions of this application will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0032] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in multiple embodiments of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0033] Preparation Example 1: Preparation of Modified Thermally Conductive Nanoparticles Take 8 g of γ-aminopropyltriethoxysilane (KH550), add 2 mL of deionized water and 100 mL of anhydrous ethanol, and hydrolyze at 30 °C for 2 h to obtain the hydrolysate.

[0034] 10 g of boron nitride nanosheets with an average particle size of 80 nm were added to a high-speed mixer, heated to 120 °C, and the hydrolysate was sprayed in. High-speed mixing continued for 30 min, followed by aging at 120 °C for 1 h. The treated boron nitride was washed three times with anhydrous ethanol and dried at 105 °C for 4 h to obtain modified boron nitride nanoparticles.

[0035] Preparation Example 2: Preparation of Composite Corrosion Inhibitor 10 g of 5-hexyl-1H-benzotriazole and 10 g of tetraethoxysilane were mixed evenly at room temperature to obtain a composite corrosion inhibitor.

[0036] Preparation Example 3: Preparation of Mannich Base Dispersants The Mannich base dispersant is a condensation product of polyisobutylene phenol, formaldehyde, and polyene polyamine. It can be commercially available or synthesized by following these steps: (1) Add 200 g of highly active polyisobutylene (number average molecular weight 800-1300), 30 g of phenol and 100 mL of xylene to a reaction vessel, heat to 80°C, add 2 g of boron trifluoride diethyl ether complex under stirring, purge with nitrogen, and keep the reaction at this temperature for 6 h. After the reaction is complete, wash with 10% sodium hydroxide solution until neutral, then wash with deionized water, separate the liquids and evaporate the xylene to obtain polyisobutylene phenol.

[0037] (2) Add 100 g of the above-mentioned polyisobutylene phenol, 10 g of triethylenetetramine, 15 g of 36% formaldehyde aqueous solution and 80 mL of toluene to a reaction vessel equipped with a water separator. Heat to reflux, and continuously remove the water generated in the reaction through the water separator under reflux conditions. Monitor and maintain the pH of the reaction system between 6.5 and 7.5, and reflux for 2 h. After the reaction is completed, remove the toluene by vacuum distillation, add 80 g of aromatic diluent oil, stir evenly, and obtain Mannich base dispersant.

[0038] Preparation Example 4: Formulation of Composite Dispersant Composite dispersant D1 (PIBSI: Mannich base = 1:2) Take 5 g of polyisobutylene succinimide (PIBSI, Mn=1500, amine value 45), add 10 g of the Mannich base dispersant prepared above, stir and mix evenly at room temperature to obtain composite dispersant D1.

[0039] Composite dispersant D2 (PIBSI: Mannich base = 1:1) Take 10 g of polyisobutylene succinimide (PIBSI, Mn=1500, amine value 45), add 10 g of the Mannich base dispersant prepared above, stir and mix evenly at room temperature to obtain composite dispersant D2.

[0040] Composite dispersant D3 (PIBSI: Mannich base = 2:1) Take 10 g of polyisobutylene succinimide (PIBSI, Mn=1500, amine value 45), add 5 g of the Mannich base dispersant prepared above, stir and mix evenly at room temperature to obtain composite dispersant D3.

[0041] To investigate the effects of base oil ratio (A), thermally conductive nanoparticle dosage (B), and composite dispersant dosage (C) on coolant performance, a single-factor experiment was conducted. The influencing factors are shown in Table 1 below.

[0042] Table 1. Range of experimental factor levels

[0043] The coolants in Examples 1-12 below were all prepared according to the following steps: Add the formulated amounts of PAO base oil (PAO4, viscosity 18 cSt at 40℃), synthetic ester (pentaerythritol tetraester), pour point depressant (polymethyl methacrylate), and antioxidant (2,6-di-tert-butyl-p-cresol) to the reactor, heat to 55℃, and stir to dissolve to obtain the base liquid.

[0044] Separately, mix the formulated amounts of composite corrosion inhibitor and composite dispersant with 10 g of base liquid to obtain an additive premix. Add the formulated amounts of modified boron nitride nanoparticles to the additive premix, ultrasonically disperse for 20 min, and then shear at 4000 rpm for 30 min to obtain a nanoparticle dispersion. Mix the nanoparticle dispersion with the remaining base liquid, add the formulated amounts of defoamer (silicone polyether), stir for 40 min, and filter through a 1 μm filter to obtain a coolant.

[0045] Example 1 80 g PAO base oil, 20 g synthetic ester, 1 g modified boron nitride nanoparticles, 0.5 g composite dispersant D2, 0.6 g composite corrosion inhibitor, 0.2 g antioxidant, 0.3 g pour point depressant, and 0.02 g defoamer.

[0046] Example 2 80 g PAO base oil, 20 g synthetic ester, 3 g modified boron nitride nanoparticles, 1.2 g composite dispersant D2, 0.6 g composite corrosion inhibitor, 0.2 g antioxidant, 0.3 g pour point depressant, and 0.02 g defoamer.

[0047] Example 3 80 g PAO base oil, 20 g synthetic ester, 5 g modified boron nitride nanoparticles, 2.0 g composite dispersant D2, 0.6 g composite corrosion inhibitor, 0.2 g antioxidant, 0.3 g pour point depressant, and 0.02 g defoamer.

[0048] Example 4 90 g PAO base oil, 10 g synthetic ester, 3 g modified boron nitride nanoparticles, 1.2 g composite dispersant D2, 0.6 g composite corrosion inhibitor, 0.2 g antioxidant, 0.3 g pour point depressant, and 0.02 g defoamer.

[0049] Example 5 70 g PAO base oil, 30 g synthetic ester, 3 g modified boron nitride nanoparticles, 1.2 g composite dispersant D2, 0.6 g composite corrosion inhibitor, 0.2 g antioxidant, 0.3 g pour point depressant, and 0.02 g defoamer.

[0050] Example 6 80 g PAO base oil, 20 g synthetic ester, 3 g modified boron nitride nanoparticles, 1.2 g composite dispersant D1, 0.6 g composite corrosion inhibitor, 0.2 g antioxidant, 0.3 g pour point depressant, and 0.02 g defoamer.

[0051] Example 7 80 g PAO base oil, 20 g synthetic ester, 3 g modified boron nitride nanoparticles, 1.2 g composite dispersant D3, 0.6 g composite corrosion inhibitor, 0.2 g antioxidant, 0.3 g pour point depressant, and 0.02 g defoamer.

[0052] Example 8 80 g PAO base oil, 20 g synthetic ester, 3 g modified boron nitride nanoparticles, 1.5 g composite dispersant D2, 0.6 g composite corrosion inhibitor, 0.2 g antioxidant, 0.3 g pour point depressant, and 0.02 g defoamer.

[0053] Example 9 80 g PAO base oil, 20 g synthetic ester, 3 g modified boron nitride nanoparticles, 2.0 g composite dispersant D2, 0.6 g composite corrosion inhibitor, 0.2 g antioxidant, 0.3 g pour point depressant, and 0.02 g defoamer.

[0054] The specific ingredient combinations for each embodiment are shown in Table 2 below.

[0055]

[0056] Comparative Example 1 Compared with Example 2, the amount of composite dispersant D2 was reduced to 0.2 g, while the rest remained the same.

[0057] Comparative Example 2 Compared to Example 2, the composite dispersant D2 was replaced with a single polyisobutylene succinimide (PIBSI, Mn=1500, amine value 45), with the amount remaining the same at 1.2 g.

[0058] Comparative Example 3 Compared to Example 2, the composite dispersant D2 was replaced with polyisobutylene monosuccinimide (monosuccinimide, Mn=1000) at a dosage of 1.2 g, while the rest remained the same.

[0059] Comparative Example 4 Compared to Example 2, composite dispersant D2 was replaced with polymethyl methacrylate dispersant (PMA dispersant) at a dosage of 1.2 g, while the rest remained the same.

[0060] Experimental Example To make the beneficial effects of the present invention clearer, the thermal conductivity, insulation properties, corrosion resistance and dispersion stability of the coolants obtained in each embodiment and comparative example under simulated sealing material precipitate environment will be evaluated below.

[0061] 1) Basic performance test Pour point shall be determined according to GB / T 3535; kinematic viscosity at 40℃ shall be determined according to GB / T 265; kinematic viscosity at -40℃ shall be determined according to GB / T 265; flash point (open cup) shall be determined according to GB / T 3536; breakdown voltage shall be determined according to GB / T 507; moisture content shall be determined according to GB / T 11133; oxidation stability (rotating bomb oxidation method) shall be determined according to SH / T 0193.

[0062] 2) Compatibility Testing Volume resistivity was determined according to GB / T 5654 (test temperature 25℃, 500 V, 60 s). Copper corrosion was performed according to GB / T 5096. Aluminum corrosion was performed using the plate method: the test piece (6061 aluminum alloy, 75×12.5×3 mm) was polished, degreased, weighed, and then immersed in coolant and left to stand at 120℃ for 168 h. After removal, it was acid-washed (20% nitric acid, 5 min), rinsed, dried, and weighed.

[0063] The corrosion rate is calculated using the following formula: ν(mm / a) = (m0 - m1) × 87600 / (A ×t × ρ). Where: m0 is the initial mass (g), m1 is the mass after the test (g), A is the surface area (cm²), t is the time (h), and ρ is the density (g / cm³). 3 Aluminum density: 2.7 g / cm³ 3 Three test pieces were tested in parallel for each sample, and the average value was taken.

[0064] 3) Pollutant tolerance test To simulate the effect of sealant precipitates on coolant, 0.5 parts by weight (relative to 100 parts by weight of the total base oil and synthetic ester) of dioctyl phthalate (DOP) was added to each coolant as a simulated sealant precipitate. After thorough mixing, the mixture was placed in a sealed oven at 80°C for 720 h. After aging, the retention rate of thermal conductivity, the increase in acid value, and the sedimentation of nanoparticles were measured. Thermal conductivity was measured according to ASTM D7896-19 at 25°C. Acid value was measured according to GB / T 4945. Nanoparticle sedimentation was evaluated using the absorbance method (measuring the change in transmittance at 550 nm): after aging and standing for 24 h, the transmittance of the supernatant was measured. Compared with the initial transmittance, a transmittance change ≤5% indicated no sedimentation, 5%-15% indicated slight sedimentation, and >15% indicated sedimentation.

[0065] 4) Test Results The basic performance of each embodiment of the present invention is shown in Tables 3 and 4 below.

[0066] Table 3. Test Results of Basic Performance of Coolant

[0067] Table 4. Test results of the electrical and chemical properties of the coolant

[0068] Test results show that the kinematic viscosity of the coolant in each embodiment at 40°C is 18.5-22.0 mm. 2 / s, kinematic viscosity at -40℃ is less than 400 mm. 2 / s, pour point ≤ -47℃, flash point ≥ 235℃, breakdown voltage ≥ 50 kV, moisture content ≤ 18 mg / kg, oxidation stability ≥ 383 min, meeting the performance requirements of immersion liquid cooling systems for coolant.

[0069] The material compatibility test results of the coolant in each embodiment of the present invention are shown in Table 5 below.

[0070] Table 5. Material compatibility test results

[0071] The results show that the volume resistivity of the coolant in each embodiment is greater than 1×10⁻⁶. 15 The temperature is Ω·cm, which meets the insulation requirements; the corrosion rates of copper and aluminum are both less than 0.01 mm / a, and the material has good compatibility with metallic materials.

[0072] The contaminant tolerance test results of the coolant in each embodiment of the present invention are shown in Table 6 below.

[0073] Table 6 Results of Pollutant Tolerance Tests

[0074] As shown in Table 6, the coolant provided by the present invention exhibits good contaminant tolerance in the simulated aging test of sealant precipitates.

[0075] With the same total amount of dispersant (1.2 parts), Example 2, which used composite dispersant D2 (1:1), maintained a thermal conductivity retention rate of 95.5%, increased the acid value by only 0.15 mgKOH / g, and showed no sedimentation of nanoparticles; while Comparative Example 2, which used single PIBSI, maintained a thermal conductivity retention rate of only 89.0%, increased the acid value by 0.35 mgKOH / g, and showed slight sedimentation, indicating that the composite dispersant performed better.

[0076] Compared with other types of dispersants, Comparative Example 3 (monosuccinimide) retained 80.1% of its thermal conductivity, increased its acid value by 0.58 mgKOH / g, and showed significant sedimentation; Comparative Example 4 (PMA dispersant) retained 78.3% and increased its acid value by 0.65 mgKOH / g, respectively, showing even more severe sedimentation. PIBSI alone (Comparative Example 2) was significantly superior to both.

[0077] From the perspective of the ratio of the composite dispersants, all three ratios are superior to single PIBSI. Among them, D2 (1:1) has the best overall performance, with a retention rate of 95.5% in Example 2 and an increase in acid value of 0.15 mgKOH / g; D1 (1:2) has a retention rate of 90.0% in Example 6 and an increase in acid value of 0.32 mgKOH / g; D3 (2:1) has a retention rate of 94.0% in Example 7 and an increase in acid value of 0.18 mgKOH / g. D1 and D3 are also superior to single PIBSI, but the 1:1 ratio has the most outstanding effect.

[0078] Regarding the dosage of dispersant, when the dosage was 0.5 parts (Example 1), the retention rate was 86.0%, the acid value increased by 0.40 mg KOH / g, and slight sedimentation occurred. When the dosage was increased to more than 1.2 parts (Examples 2, 8, and 9), the retention rate increased to more than 95%, the acid value decreased to below 0.15 mg KOH / g, and no sedimentation occurred. In the coolant system of this invention, the composite dispersant can better exert its stabilizing effect when the dosage reaches about 1.2 parts.

[0079] Based on the above test data, it can be seen that the coolant provided by this invention has a high flash point (≥235℃) and good thermal conductivity, which can meet the safety and heat exchange efficiency requirements of immersion liquid cooling systems. In terms of rust prevention performance, the corrosion rates of copper and aluminum are both less than 0.01 mm / a, which can effectively reduce the impact of corrosion factors on metals. In accelerated aging tests simulating sealant precipitates, a coolant using composite dispersant D2 (1:1) at a dosage of no less than 1.2 parts maintained a thermal conductivity retention rate of over 95%, with an acid value increase of less than 0.20 mgKOH / g and no nanoparticle sedimentation. The coolant prepared by this invention possesses excellent rust prevention, good thermal conductivity, and long-term stability, effectively resisting interference from sealant precipitates and maintaining long-term stable dispersion of nanoparticles. It is suitable for immersion liquid cooling systems in data centers, energy storage power stations, and electric vehicles.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A coolant, characterized in that, By weight, it includes: 80-95 parts base oil, 1-5 parts thermally conductive nanoparticles, 0.5-2 parts composite dispersant, 0.3-1 part composite corrosion inhibitor, 0.1-0.5 parts antioxidant, 0.2-0.5 parts pour point depressant, and 0.01-0.05 parts defoamer; The base oil is a mixture of polyalphaolefin base oil and synthetic ester, with a mass ratio of polyalphaolefin base oil to synthetic ester of 70-90:10-30; the composite dispersant includes a mixture of polyisobutylene succinimide and Mannich base dispersant, with a mass ratio of polyisobutylene succinimide to Mannich base dispersant of 1:0.5-2.

2. The coolant according to claim 1, characterized in that, By weight, it includes 85-90 parts base oil, 2-4 parts thermally conductive nanoparticles, 1.0-1.5 parts composite dispersant, 0.5-0.8 parts composite corrosion inhibitor, 0.2-0.3 parts antioxidant, 0.3-0.4 parts pour point depressant, and 0.02-0.03 parts defoamer.

3. The coolant according to claim 1 or 2, characterized in that, The polyisobutylene succinimide has a number-average molecular weight of 800–2000 and an amine value of 20–80 mgKOH / g; the Mannich base dispersant is a condensation product of polyisobutylene phenol, formaldehyde, and polyene polyamine.

4. The coolant according to claim 3, characterized in that, The mass ratio of polyisobutylene succinimide to Mannich base dispersant in the composite dispersant is 1:

1.

5. The coolant according to claim 1, characterized in that, The composite corrosion inhibitor comprises a mixture of benzotriazole derivative and silane ester, with a mass ratio of 1:0.2 to 2; the benzotriazole derivative is 5-hexyl-1H-benzotriazole, and the silane ester is tetraethoxysilane.

6. The coolant according to claim 1, characterized in that, The thermally conductive nanoparticles are boron nitride nanosheets or aluminum nitride nanoparticles modified with a silane coupling agent.

7. The coolant according to claim 6, characterized in that, The surface modifier of the thermally conductive nanoparticles is γ-aminopropyltriethoxysilane, with an average particle size of 50–200 nm.

8. The coolant according to claim 1, characterized in that, The antioxidant is 2,6-di-tert-butyl-p-cresol; the pour point depressant is polymethyl methacrylate; and the defoamer is silicone polyether.

9. A method for preparing the coolant according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Mix the base oil, pour point depressant, and antioxidant, and heat to 50-60°C while stirring to dissolve. S2. Take 5% to 10% of the total volume of the mixture obtained in S1, add the composite corrosion inhibitor and composite dispersant, and mix evenly. S3. Add the thermally conductive nanoparticles to the mixture obtained in S2, disperse them ultrasonically for 15-30 min, and then disperse them by high-speed shearing. S4. Mix the dispersion obtained in S3 with the remaining mixture in S1, add defoamer, stir for 30-60 minutes, filter, and obtain coolant.

10. The application of the coolant as described in any one of claims 1 to 8 or the coolant prepared by the method of claim 9 in data centers, energy storage power stations or electric vehicle immersion liquid cooling systems.

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