An immersion coolant

Abstract

The technical field of coolants of the present invention discloses an immersion coolant, which mainly comprises component A and component B, wherein component A comprises a chain alkane having one methyl side chain on the main chain, and component B comprises a chain alkane having two side chains on the main chain, wherein one side chain is a methyl group, and the other side chain is a straight-chain alkyl group with a carbon number of at least 4. The two components are used in combination to obtain an immersion coolant with higher heat transfer performance and anti-friction performance, and the performance of the coolant can be adjusted by changing the contents of the two components. Increasing the amount of component A can improve the heat transfer performance of the coolant and simultaneously improve the pour point, which is not conducive to the low-temperature fluidity of the coolant. Increasing the amount of component B can reduce the pour point and improve the low-temperature fluidity, but the heat transfer performance is also reduced. Therefore, the formula of the immersion coolant can be flexibly adjusted to enable it to be effectively applied to different application scenarios.

Description

Technical Field

[0001] The invention relates to the technical field of cooling liquids, in particular to an immersion cooling liquid. Background Art

[0002] In the new era of promoting green and low-carbon transformation, the production and sales of new energy vehicles have been rising year by year. Among them, power batteries, as the power source of new energy vehicles, are the most important system in the whole vehicle, accounting for 30-40% of the whole vehicle cost, and directly affecting the performance of new energy vehicles.

[0003] In actual vehicle use, the battery will face complex and changeable operating conditions. In order to increase the driving range, the vehicle needs to arrange as many cells as possible in a certain space, so the space for the battery pack on the vehicle is very limited. The battery generates a lot of heat during the operation of the vehicle and accumulates in a relatively small space over time. Due to the dense stacking of cells in the battery pack, it is also relatively more difficult to dissipate heat in the middle area to a certain extent, exacerbating the temperature inconsistency between cells. As a result, the battery's charging and discharging efficiency will be reduced, affecting the battery's power. In severe cases, it will cause thermal runaway, affecting the safety and life of the system.

[0004] In order to prevent problems with the battery during use and ensure the high efficiency of the battery, the battery thermal management system is very important. The battery thermal management system mainly allows the battery pack to always work within a suitable temperature range to maintain the optimal working state of the battery pack. Battery thermal management mainly includes functions such as cooling, heating, and temperature equalization. The cooling and heating functions are mainly to make corresponding adjustments based on the possible impact of the external ambient temperature on the battery. Temperature equalization is used to reduce the temperature difference inside the battery pack to prevent rapid attenuation caused by overheating of a part of the battery. Usually we expect the battery to operate within a temperature range of 20-40°C, so that the vehicle can achieve the best power output and input, maximum available energy, and longest cycle life.

[0005] Generally speaking, the cooling modes of power batteries are mainly divided into air cooling, liquid cooling, direct cooling and immersion cooling. The air cooling mode uses natural wind or cooling air in the passenger compartment to flow through the surface of the battery to achieve the effect of heat exchange cooling. Liquid cooling generally uses independent coolant pipelines to heat or cool the power battery. The direct cooling system directly uses refrigerant to cool the power battery. Immersion liquid cooling is to immerse the heat-generating device in the coolant and rely on the circulation of the coolant to take away the heat. Compared with air cooling, liquid cooling and direct cooling technologies, immersion liquid cooling has excellent cooling efficiency and the best temperature uniformity, and the equipment structure is relatively simple, does not require frequent refilling of coolant, and the container sealing requirements are not particularly high, which can greatly reduce costs while reducing the risk and impact of thermal runaway.

[0006] In addition to battery systems, power electronics (Power Electronic) makes many efficient and powerful innovations possible by converting electrical energy from one level of voltage and frequency to another level of voltage and frequency, such as the electric drive motors of electric vehicles and hybrid vehicles. However, power electronics generate a lot of heat due to their high power during operation. As the temperature rises, the efficiency, reliability and life of the equipment will decrease, especially in the shedding of bonding wires, fatigue of solder joints (life decreases by 3-4 times for every 20K increase in temperature), thermal-mechanical stress leading to metallization reconstruction, and thermal stress leading to deformation of the base of the equipment, especially in the DC-DC converter and inverter system inside hybrid and electric vehicles. It can be seen that high temperature is not conducive to the reliability and sustainable use of power electronics, and it is urgent to introduce immersion coolants that can be directly contacted to efficiently control the temperature during the operation of power electronics.

[0007] At present, mainstream automobile manufacturers are conducting research and development and testing of immersion coolants and the accompanying immersion cooling systems, see patents such as CN110709373A, EP3236727A2 and EP4124194A1 for details. For example, companies such as M&I Material, Solvay and 3M have developed immersion coolants specifically designed for electric vehicle batteries; XING Mobility launched the world's first commercial electric vehicle immersion cooling system in 2018; McLaren GTR original batteries and upgraded batteries are both cooled by dielectric fluids; Mercedes C63 AMG uses dielectric fluids to cool the center of the battery body, etc. Among them, the dielectric fluids under study include: fluoride, silicone oil, ester oil, mineral oil, vegetable oil, fully synthetic oil, etc. Fluoride has the advantages of high density and good overall heat transfer performance, but it is too easy to volatilize. After being discharged into the atmosphere, fluoride is easy to damage the ecological environment; ester oil has poor water resistance and general material compatibility; mineral oil has the advantage of low price, but high viscosity and poor heat dissipation effect; vegetable oil is also low-cost, raw materials are easy to obtain and do not rely on petroleum products, but has the defects of high viscosity, easy hydrolysis and poor fluidity; silicone oil has good viscosity-temperature performance, but poor friction performance and large thermal expansion coefficient. Compared with them, fully synthetic base oil has excellent dielectric properties, heat transfer performance, high and low temperature performance, is not easy to volatilize, has good water resistance, and suitable cost, which is an ideal material for immersion coolant. For fully synthetic base oil, it is also necessary to improve its specific heat capacity and thermal conductivity when used as immersion coolant, so as to better play the role of heat transfer. Summary of the invention

[0008] The present invention aims at solving the deficiencies of the prior art and provides an immersion cooling liquid.

[0009] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0010] An immersion cooling liquid, the cooling liquid comprising the following components: component A and component B, wherein component A comprises a chain alkane having one methyl side chain on the main chain, and component B comprises a chain alkane having two side chains on the main chain, wherein one side chain is a methyl group and the other side chain is a straight-chain alkyl group having at least 4 carbon atoms;

[0011] The carbon number of the alkane contained in the component A is 12-30, and the kinematic viscosity at 100° C. is 1.0-3.0 mm 2 •s -1 , kinematic viscosity at 40°C is 3.5-9.0mm 2 •s -1 ;

[0012] The carbon number of the alkane contained in the component B is 18-48, and the kinematic viscosity at 100° C. is 1.5-8.0 mm 2 •s -1 , kinematic viscosity at 40°C is 4.5-50 mm 2 •s -1 .

[0013] Preferably, the component B comprises a combination of at least two paraffins with different kinematic viscosities.

[0014] Preferably, the chain alkane contained in the component B is a metallocene poly-alpha olefin trimer, which is obtained by polymerization of linear alpha olefins under a metallocene catalyst system and then hydrogenation and saturation.

[0015] Wherein, the linear α-olefins mentioned above may be the same or different, and component B includes but is not limited to hydrogenated saturated 1-octene trimer, 1-decene trimer, or α-olefin trimer of a mixture of 1-octene and 1-decene. More preferably, component B is selected from hydrogenated saturated 1-octene trimer and / or 1-decene trimer, and further preferably, component B is selected from hydrogenated saturated 1-octene trimer.

[0016] Preferably, the carbon number of the alkane contained in component A is 20-30; preferably, the alkane is selected from 9-methylnonadecane and / or 11-methyltricosane.

[0017] Preferably, the amount of the coolant raw material is calculated as a percentage, component A is 1-99wt%, and component B is 1-99wt%; preferably, component A is 5-45wt%, and component B is 15-75wt%; more preferably, component A is 5-35wt%, and component B is 25-75wt%.

[0018] Preferably, the metallocene catalyst system comprises at least one metallocene catalyst, which is an inorganic-organic complex containing at least one cyclopentadienyl or cyclopentadienyl derivative as a ligand and at least one Group IVB transition element as a central atom.

[0019] Preferably, the coolant further comprises a base oil, which is one or more of API-II, API-III, and API-V base oils, and the component usage is 20-50wt%; preferably, the coolant further comprises an API-III base oil, and the component usage is 20-50wt%.

[0020] Preferably, the API-III base oil has a carbon number of 10-60 and a kinematic viscosity of 1.0-8.0 mm at 100°C. 2 •s -1 ; Preferably, the API-III base oil includes ULTRA-S series base oil, such as Ultra S-2, Ultra S-3, UltraS-4, Ultra S-6, Ultra S-8, etc.; Yubase series base oil, such as Yubase2, Yubase3, Yubase4, Yubase6, Yubase8, etc.; ADbase series base oil, such as Adbase2, Adbase3, Adbase4, Adbase6, Adbase8, etc.; Nexbase series base oil, such as Nexbase2, Nexbase3, Nexbase4, Nexbase6, Nexbase8, etc.; ICSYN series base oil, such as ICSYN2, ICSYN3, ICSYN4, ICSYN6, etc., SINOPURE series base oil, such as 2828H, 2835, 2835H, etc.

[0021] Preferably, the coolant further includes one or more antioxidants, corrosion inhibitors, antifoaming agents, antiwear additives, dispersants, detergents, viscosity improvers and any combination thereof; preferably, the coolant further includes one or more antioxidants and antifoaming agents; more preferably, the coolant further includes the antioxidant 2,6-di-tert-butyl-p-methylphenol and the Xinxing No. 1 composite antifoaming agent.

[0022] Preferably, the pour point of the coolant is not higher than -20°C, and more preferably, the pour point of the coolant is not higher than -40°C, wherein the pour point is tested using the GB / T 3535 standard.

[0023] Preferably, the kinematic viscosity of the coolant at 100°C (KV@100°C) is not less than 2.50 mm 2 ·s -1The kinematic viscosity at 40℃ (KV@40℃) is not less than 9.00 mm 2 ·s -1 , where the kinematic viscosity is tested using the GB / T 265 standard.

[0024] Preferably, the viscosity index of the coolant is not less than 100, and more preferably, the viscosity index of the coolant is not less than 110, wherein the viscosity index is calculated using the standard of GB / T 1995.

[0025] Preferably, the flash point of the coolant is not less than 160° C., and more preferably, the flash point of the coolant is not less than 170° C., wherein the flash point is tested using the Cleveland open cup method of standard GB / T 3536.

[0026] Preferably, the specific heat capacity of the coolant at 40°C is not less than 2.10 (J·g -1 ·K -1 ), wherein the specific heat capacity is tested using the standard of ASTM E1269-2011.

[0027] Preferably, the thermal conductivity of the coolant is not less than 0.190 (W·m -1 ·K -1 ), wherein the thermal conductivity is tested using the standard of ASTM D 2717-2009.

[0028] Preferably, the dielectric strength of the coolant is not less than 30KV. More preferably, the dielectric strength of the coolant is not less than 33KV, wherein the dielectric strength is tested using the test method 5.1 in standard YD / T 3982-2021.

[0029] Preferably, the oxidation stability of the coolant is not less than 300 min, and more preferably, the oxidation stability of the coolant is not less than 340 min, wherein the oxidation stability is tested using the rotating oxygen bomb method (RBOT) of standard SH / T 0193.

[0030] Preferably, the anti-friction performance of the coolant has an average wear spot diameter of less than 1.00 mm, wherein the anti-friction performance is tested using the four-ball test method of standard NB / SH / T 0189-2017 to test the average wear spot diameter.

[0031] Furthermore, the present invention also discloses a method for preparing the immersion cooling liquid, the method comprising mixing component A and component B to obtain the immersion cooling liquid;

[0032] Preferably, the preparation method further comprises mixing the mixture of component A and component B with an additive and a base oil;

[0033] Preferably, after the mixing is completed, the immersion cooling liquid is obtained by filtering;

[0034] Preferably, the mixing is carried out at room temperature to 60°C;

[0035] Preferably, the mixing time is 5-60 min.

[0036] Furthermore, the present invention also discloses a battery system, which comprises: a battery and the immersion coolant, wherein the immersion coolant is in direct contact with the battery; preferably, at least a portion of the battery is immersed in the immersion coolant; preferably, the battery is a lithium-ion battery.

[0037] Furthermore, the present invention also discloses a power electronics, which refers to a high-power device that converts electric energy from one level voltage and frequency to another level voltage and frequency and provides power supply to a load. The power electronics includes: a heat generating component and the immersion coolant, the immersion coolant is in direct contact with the heat generating component; preferably, at least a part of the heat generating component is immersed in the immersion coolant; preferably, the power electronics is a power device of a charging pile, an electric control system of an electric vehicle, or an electric control system of an energy storage battery.

[0038] The beneficial effects of the present invention are as follows: the immersion coolant proposed by the present invention uses a chain alkane having one methyl side chain on the main chain (component A) and a chain alkane having two side chains on the main chain (component B) in combination, thereby obtaining an immersion coolant with higher heat transfer performance, and changing the contents of the two components can adjust the performance of the coolant. Increasing the amount of component A can improve the heat transfer performance of the coolant and increase the pour point at the same time, which is not conducive to the low-temperature fluidity of the coolant. Increasing the amount of component B can reduce the pour point and improve the low-temperature fluidity, but the corresponding heat transfer performance is also reduced; at the same time, the coolant prepared by adding component A to component B has higher anti-friction performance without adding an anti-wear agent. It can be seen that the immersion coolant prepared by the present invention has the potential to be used as a lubricant in addition to good heat transfer performance.

[0039] The coolant provided by the present invention has good heat transfer performance and anti-friction performance, high metal corrosion inhibition, good insulation performance and oxidation resistance. At the same time, according to the above rules, the formula of the immersion coolant can be adjusted according to different application scenarios. In the case where the low-temperature fluidity requirement is not high, the content of component A is increased to improve the heat transfer performance, and in the case where the low-temperature fluidity requirement is high, the content of component B is increased to reduce the pour point. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is the chemical structural formula of 1-octene trimer.

[0041] Figure 2 It is the chemical structural formula of 1-decene trimer.

[0042] Figure 3 The figure of merit (FOM) of heat transfer of the immersion cooling liquids of Examples 1-7 and Comparative Examples 1-3 under laminar and turbulent flow conditions is compared.

[0043] Figure 4 This is the wear spot diameter test image of the four-ball test of immersion coolant in Example 1.

[0044] Figure 5 This is the wear spot diameter test image of the four-ball test of immersion coolant in Example 4.

[0045] Figure 6 This is the wear spot diameter test image of the four-ball test of immersion coolant in Example 7.

[0046] Figure 7 This is the wear spot diameter test image of the four-ball test of immersion coolant in comparative example 1. DETAILED DESCRIPTION

[0047] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0049] The present invention is further described in conjunction with specific examples. The following examples are only for explaining the present invention and are not intended to limit the content thereof. If the specific experimental conditions are not specified in the examples, they are usually carried out under conventional conditions or under conditions recommended by the sales company; the materials and reagents used in the examples, unless otherwise specified, can be purchased through commercial channels.

[0050] The properties of the main components of the immersion coolant are shown in Table 1.

[0051] Table 1

[0052] name <![CDATA[KV@100℃ / mm 2 ·s -1 ]]> <![CDATA[KV@40℃ / mm 2 ·s -1 ]]> Viscosity Index Flash point / ℃ Pour point / ℃ 9-Methylnonadecane(CAS:13287-24-6) 1.70 4.55 - - - 11-Methyltricosane(CAS:27538-41-6) 1.96 6.14 - - - 1-Octene trimer (7-methyl-9-hexyl-heptadecane) 2.08 6.59 114 188 <-60 1-Decene trimer (9-methyl-11-octyl-heneicosane) 3.65 14.73 137 238 <-60 PAO2 1.67 4.99 89 161 <-60 API-III base oil (Yubase3) 3.02 11.98 108 187 -39 API-III base oil (2835H) 1.43 3.81 114 136 -30

[0053] Main components of immersion coolant:

[0054] 9-Methylnonadecane and 11-methyltricosane are chain alkanes having one methyl side chain on the main chain.

[0055] 1-Octene trimer (7-methyl-9-hexyl-heptadecane) and 1-decene trimer (9-methyl-11-octyl-heneicosane) are α-olefin trimers prepared by polymerization of 1-octene and 1-decene and hydrogenation saturation based on a metallocene catalyst system. The metallocene catalyst has a single active center and can accurately control the molecular structure of mPAO. Before hydrogenation saturation, the double bond positions in the trimer molecules are different. After hydrogenation saturation, the trimer has a neat comb-like structure with uniform side chain length.

[0056] Characterization of 1-octene trimer, 13 C-NMR (Bruker, Germany, AVANCE III HD 400, solvent CDCl3): 37.8, 37.2, 36.5, 31.8, 31.3, 30.4, 30.0, 29.4, 28.3, 26.5, 22.6,22.3, 21.8, 20.0, 14.6, 14.4, 14.0. The chemical structure of the 1-octene trimer was characterized by carbon spectrum as 7-methyl-9-hexyl-heptadecane, as shown in the following figure: Figure 1 shown.

[0057] Characterization of 1-decene trimer, 13 C-NMR (Bruker, Germany, AVANCE III HD 400, solvent CDCl3): 37.5, 37.0, 36.4, 31.9, 31.4, 30.6, 30.1, 29.4, 28.3, 26.5, 22.6, 22.3, 21.9, 20.0, 14.5, 14.2, 14.0. The chemical structure of the 1-decene trimer was characterized by carbon spectrum as 9-methyl-11-octyl-heneicosane, such as Figure 2 shown.

[0058] Among them, the kinematic viscosities of 1-octene trimer and 1-decene trimer at 100°C are 2.0 and 3.5 mm 2 •s -1 about.

[0059] PAO2 is a polyalphaolefin prepared by polymerization of alpha olefins catalyzed by BF3, AlCl3 catalyst or Ziegler-Natta catalyst system and hydrogenation saturation. Its mechanism is to carry out polymerization reaction by means of carbon cations, with multiple catalytic active centers and more rearrangements. Therefore, the molecular structure of PAO2 is more diversified, which is reflected in the higher proportion of short chains and branches in the molecule, and the length of the branches varies. The kinematic viscosity of PAO2 at 100°C is 2.0mm 2 •s -1 about.

[0060] Yubase3 comes from South Korea's SK Group. It is a YUBASE series of three base oils produced from hydrocracking tail oil (UCO) through processes such as hydroisomerization and hydrorefining.

[0061] 2835H comes from Shanxi Lu'an Taihang Lubrication Technology Co., Ltd. It is a SINOPURE series Class III base oil made from coal-to-syngas and then through Fischer-Tropsch synthesis.

[0062] Selection of additives: Antioxidant 2,6-di-tert-butyl-p-methylphenol (T501) and Xinxing No. 1 composite anti-foaming agent are selected as additives for the immersion coolant formula.

[0063] Preparation of immersion coolant: Mix the paraffin with one methyl side chain on the main chain with 1-octene trimer and 1-decene trimer at room temperature for 10 minutes, then add the remaining components and mix and stir for 20 minutes at room temperature, and filter to obtain immersion coolant. According to the above preparation method and the formula listed below, the immersion coolant samples of Examples 1-7 and Comparative Examples 1-3 were prepared.

[0064] The specific formulation components of Examples 1-7 and Comparative Examples 1-3 are listed in Table 2.

[0065] Table 2

[0066] sample Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 Comparative Example 3 1-Decene trimer 30 35 40 30 35 25 20 30 49.84 30 PAO2 0 0 0 0 0 0 0 30 0 0 9-Methylnonadecane 16.5 13.8 11 19.2 0 0 20 0 0 0 11-Methyltricosane 0 0 0 0 17.7 11.8 20 0 0 0 1-Octene trimer 13.5 11.2 9 15.8 17.3 13.2 0 0 0 30 Yubase3 39.84 34.84 29.84 34.84 29.84 49.84 39.84 39.84 25 34.84 2835H 0 5 10 0 0 0 0 0 25 5 T501 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 Xinxing No. 1 composite antifoaming agent 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 <![CDATA[KV@100℃(mm 2 ·s -1 )]]> 2.68 2.73 2.70 2.67 2.69 2.82 2.66 2.69 2.78 2.77 <![CDATA[KV@40℃(mm 2 ·s -1 )]]> 9.52 9.86 9.74 9.59 9.72 10.35 9.70 9.90 10.12 10.24 Viscosity Index 122 120 118 117 116 120 111 110 120 114

[0067] Kinematic viscosity and viscosity index: GB / T 265 standard is used to test the kinematic viscosity of immersion coolant at 40℃ and 100℃. The higher the kinematic viscosity, the stronger the ability of the coolant to transfer heat, but the flow ability is reduced. At the same time, GB / T 1995 standard is used to calculate the viscosity index of the coolant sample;

[0068] Pour point: GB / T 3535 standard is used to test the pour point of immersion coolant. The higher the pour point, the worse the low-temperature fluidity of the sample.

[0069] Flash point: The flash point of the immersion coolant is tested using the Cleveland open cup method of standard GB / T 3536. The lower the flash point, the higher the fire hazard index of the sample;

[0070] Density: The density of immersion coolant at 100°C and 40°C is tested using the standard ASTM D 1298-1999 method. High density is beneficial to improving the heat transfer capacity of the coolant, but the coolant mass is higher under the same volume conditions, which increases the overall weight of the coolant device.

[0071] Oxidation resistance: The RBOT method of standard SH / T 0193 is used to test the oxidation stability of the immersion coolant. The oxidation stability of the sample is expressed in minutes (min) according to the oxygen bomb test time. The longer the oxygen bomb test time, the higher the oxidation stability of the sample.

[0072] Specific heat capacity: The specific heat capacity of the immersion coolant is determined by differential scanning calorimetry (DSC) using the standard ASTM E1269-2011 method. The higher the specific heat capacity, the greater the ability of the coolant to transfer heat. The test temperatures are 40°C and 60°C.

[0073] Thermal conductivity: The immersion coolant is tested at 40°C using the ASTM D 2717-2009 standard test method for thermal conductivity of liquids. The higher the thermal conductivity, the greater the ability of the coolant to transfer heat.

[0074] Figure of Merit (FOM): Referring to the method of Dielectric Fluids for the Direct Forced Convection Cooling of Power Electronics, 2021 20th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (iTherm), Brian Kelly; Gilberto Moreno; Steve Myers; Sreekant Narumanchi; Yogendra Joshi; Samuel Graham. (DOI:10.1109 / ITherm51669.2021.9503212), the FOM value of the immersion coolant at 40°C was calculated using the heat transfer figure of merit (FOM) evaluation formula under laminar and turbulent conditions. The FOM value is used to evaluate the heat transfer or heat exchange performance of the immersion coolant under laminar or turbulent conditions. The higher the FOM value, the stronger the fluid's ability to transfer heat.

[0075] Among them, the calculation formula of FOM under laminar flow state is expressed as:

[0076]

[0077] Among them, the calculation formula of FOM under turbulent state is expressed as:

[0078]

[0079] In the formula, ρ is the fluid density, κ is the thermal conductivity of the fluid, C p is the specific heat capacity of the fluid, μ is the kinematic viscosity of the fluid.

[0080] Dielectric strength: The dielectric strength of the immersion coolant is determined using the dielectric strength test method in 5.1 of standard YD / T 3982-2021.

[0081] Friction performance test: The anti-friction performance of immersed coolant samples was tested using a four-ball testing machine in accordance with the NB / SH / T 0189-2017 standard. Specifically, three lower steel balls with a diameter of 12.7 mm were clamped in an oil box and immersed in the coolant sample. Another upper steel ball with the same diameter was placed on top of the three lower steel balls. A specified load was applied. Under the action of the experimental force, the upper steel ball formed a three-point contact with the three lower steel balls. When the coolant sample was heated to the specified test temperature, the top ball rotated at a specified speed. After the test, the wear spot diameter of the lower steel ball was measured. The smaller the wear spot diameter, the better the anti-friction performance of the sample. The average value of the wear spot diameter of the three lower steel balls was taken to evaluate the anti-friction performance of the coolant sample.

[0082] The four-ball test conditions are: load: 392 N (40 kgf); spindle speed: 1200 r / min; test time: 60 min; test temperature: 75 °C.

[0083] The performances of Examples 1-7 and Comparative Examples 1-3 obtained through the above tests are shown in Table 3.

[0084] Table 3

[0085] sample Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 Comparative Example 3 Pour point(℃) -45 -49 -51 -42 -43 -46 -25 ＜-60 ＜-60 -54 Flash point(℃) 179 176 175 180 178 176 161 174 163 177 <![CDATA[Specific heat capacity at 40 °C (J·g -1 ·K -1 )]]> 2.173 2.165 2.157 2.183 2.188 2.171 2.189 2.065 2.054 2.134 <![CDATA[Specific heat capacity at 60 °C (J·g -1 ·K -1 )]]> 2.251 2.236 2.219 2.258 2.265 2.246 2.242 2.098 2.083 2.203 <![CDATA[Density at 40 °C (g / cm 3 )]]> 0.794 0.795 0.795 0.794 0.794 0.795 0.794 0.794 0.797 0.795 <![CDATA[Thermal conductivity at 40 °C, (W·m -1 ·K -1 )]]> 0.199 0.198 0.193 0.201 0.198 0.202 0.207 0.192 0.196 0.195 <![CDATA[Figure of Merit for Heat Transfer, Laminar Flow (FOM L , 40 °C)]]> 0.0454 0.0435 0.0427 0.0458 0.0446 0.0424 0.0467 0.0400 0.0398 0.0406 <![CDATA[Figure of Merit for Heat Transfer, Turbulent (FOM T , 40 °C)]]> 0.1872 0.1811 0.1787 0.1886 0.1855 0.1778 0.1915 0.1660 0.1646 0.1711 Dielectric strength(KV) 33.9 35.1 34.3 34.7 34.8 34.5 33.0 34.2 33.6 35.4 Antioxidant activity (RBOT), min 348 361 360 356 359 354 350 342 330 336 Wear spot diameter (mm) 0.982 0.967 0.989 0.968 0.973 0.995 0.952 1.021 1.047 1.024

[0086] As shown in Table 3, the samples of Examples 1-6 are added with some three types of base oils on the basis of 9-methylnonadecane, 11-methyltricosane, 1-octene trimer and 1-decene trimer, and the pour point can still reach below -40°C, and the flash point is not less than 170°C. Through the comparison of thermal properties, it is found that the specific heat capacity and thermal conductivity of the samples of Examples 1-6 are better than those of Comparative Examples 1 and 2 without adding 9-methylnonadecane or 11-methyltricosane and 1-octene trimer. This may be because the core base oil components in Examples 1-6 contain paraffins with one methyl side chain on the main chain, such as 9-methylnonadecane and 11-methyltricosane, and the molecular structure is closer to normal alkanes, with higher specific heat capacity, thermal conductivity and heat transfer capacity, and higher heat transfer merit can be obtained regardless of whether the flow state of the coolant is laminar flow or turbulent flow.

[0087] For Example 7 in which no octene trimer is added and only 9-methylnonadecane, 11-methyltricosane, 1-decene trimer and three types of base oils are used, the heat transfer effect is significantly better, but the pour point is correspondingly increased to -25°C, and the flash point and dielectric strength are slightly reduced. The content of component A in Example 7 reaches 40wt% of the total weight of the immersion coolant, which shows that adding a chain alkane with a methyl side chain on the main chain can significantly improve the specific heat capacity, thermal conductivity and heat transfer performance of the coolant, but the molecular structure of this type of chain alkane with a methyl side chain is closer to a straight-chain alkane, which significantly improves the pour point of the coolant and significantly reduces its low-temperature fluidity, which is not conducive to the use of the coolant at low temperatures.

[0088] For Comparative Example 3 in which no 9-methylnonadecane or 11-methyltricosane was added and only 1-octene trimer, 1-decene trimer and three types of base oils were used, the pour point, flash point and dielectric strength were close to those of Examples 1-6, but the heat transfer performance was significantly reduced, which shows that adding a chain alkane with a methyl side chain on the main chain to the coolant formula can effectively improve its heat transfer effect and can take away more heat from the surface of the battery or other heat-generating components.

[0089] The results of the four-ball test for the wear spot diameter show that, without adding anti-wear additives in the formulation, the wear spot diameters of the coolant samples of Examples 1-7 are lower than those of Comparative Examples 1-3, indicating that the addition of paraffins with a methyl side chain on the main chain such as 9-methylnonadecane or 11-methyltricosane can also improve the anti-friction performance of the coolant. It can be seen that the coolant with the addition of a specific structural alkane compound has the potential to be used as a lubricant compared with traditional heat transfer fluids.

[0090] The dielectric strength and oxidation resistance test results show that the dielectric strength of the coolant samples of Examples 1-7 is high enough to meet the insulation performance requirements in the electric vehicle system. From the rotating oxygen bomb test results, the samples of Examples 1-7 all have high oxidation stability.

[0091] The above is a description of the embodiments of the present invention. Through the above description of the disclosed embodiments, professionals and technicians in the field can implement or use the present invention. Various modifications to these embodiments will be apparent to professionals and technicians in the field. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown in this article, but will conform to the widest range consistent with the principles and novelties disclosed herein.

Claims

1. An immersion coolant, characterized in that: The coolant comprises the following components: component A and component B, wherein component A comprises an alkane having one methyl side chain on the main chain, and component B comprises an alkane having two side chains on the main chain, wherein one side chain is a methyl group and the other side chain is a straight-chain alkyl group having at least 4 carbon atoms; The carbon number of the alkane contained in the component A is 12-30, and the kinematic viscosity at 100° C. is 1.0-3.0 mm 2 •s -1 , kinematic viscosity at 40°C is 3.5-9.0mm 2 •s -1 ; The carbon number of the alkane contained in the component B is 18-48, and the kinematic viscosity at 100° C. is 1.5-8.0 mm 2 •s -1 , kinematic viscosity at 40°C is 4.5-50 mm 2 •s -1 ; The chain alkane contained in the component B is a metallocene poly-alpha olefin trimer, and the metallocene poly-alpha olefin trimer is obtained by polymerization of linear alpha-olefins under a metallocene catalyst system and then hydrogenation and saturation.

2. An immersion cooling liquid according to claim 1, characterized in that: The kinematic viscosity of the coolant at 100°C is not less than 2.5 mm 2 ·s -1 , the kinematic viscosity at 40°C is not less than 9.0 mm 2 ·s -1 , where the kinematic viscosity is tested using the GB / T 265 standard.

3. The immersion cooling liquid according to claim 1, characterized in that: The pour point of the coolant is not higher than -20°C, wherein the pour point is tested according to the standard of GB / T 3535.

4. An immersion cooling liquid according to claim 3, characterized in that: The pour point of the cooling liquid is not higher than -40°C.

5. The immersion cooling liquid according to claim 1, characterized in that: The viscosity index of the coolant is not less than 100, wherein the viscosity index is calculated using the standard of GB / T 1995.

6. An immersion cooling liquid according to claim 5, characterized in that: The viscosity index of the coolant is not less than 110.

7. The immersion cooling liquid according to claim 1, characterized in that: The flash point of the coolant is not less than 160° C., wherein the flash point is tested using the Cleveland open cup method of standard GB / T 3536.

8. An immersion cooling liquid according to claim 7, characterized in that: The flash point of the coolant is not less than 170°C.

9. The immersion cooling liquid according to claim 1, characterized in that: The specific heat capacity of the coolant at 40°C is not less than 2.10 (J·g -1 ·K -1 ), wherein the specific heat capacity is tested using the standard of ASTM E1269-2011.

10. The immersion cooling liquid according to claim 1, characterized in that: The thermal conductivity of the coolant is not less than 0.190 (W·m -1 ·K -1 ), wherein the thermal conductivity is tested using the standard of ASTM D 2717-2009.

11. The immersion cooling liquid according to claim 1, characterized in that: The dielectric strength of the coolant is not less than 30KV, wherein the dielectric strength is tested using the test method 5.1 in standard YD / T 3982-2021.

12. An immersion cooling liquid according to claim 11, characterized in that: The dielectric strength of the coolant is not less than 33KV.

13. The immersion cooling liquid according to claim 1, characterized in that: The oxidation stability of the coolant is not less than 300 minutes, wherein the oxidation stability is tested by the rotating oxygen bomb method of standard SH / T 0193.

14. The immersion cooling liquid according to claim 1, characterized in that: The oxidation stability of the coolant is not less than 340 minutes.

15. The immersion cooling liquid according to claim 1, characterized in that: The anti-friction performance of the coolant has an average wear spot diameter of less than 1.00 mm, wherein the anti-friction performance is tested using the four-ball test method of standard NB / SH / T 0189-2017 to test the average wear spot diameter.

16. The immersion cooling liquid according to claim 1, characterized in that: The component B comprises a combination of at least two paraffins with different kinematic viscosities.

17. The immersion cooling liquid according to claim 1, characterized in that: The component B includes, but is not limited to, hydrogenated saturated 1-octene trimer, 1-decene trimer, or a mixed α-olefin trimer of 1-octene and 1-decene.

18. The immersion cooling liquid according to claim 1, characterized in that: Component B includes hydrogenated saturated 1-octene trimer and / or 1-decene trimer.

19. The immersion cooling liquid according to claim 1, characterized in that: Component B includes hydrogenated saturated 1-octene trimer.

20. The immersion cooling liquid according to claim 1, characterized in that: The carbon number of the alkane contained in the component A is 20-30.

21. The immersion cooling liquid according to claim 1, characterized in that: The chain alkane of component A is selected from 9-methylnonadecane and / or 11-methyltricosane.

22. The immersion cooling liquid according to claim 1, characterized in that: The amount of the coolant raw materials is calculated as a percentage, with component A being 1-99wt% and component B being 1-99wt%.

23. An immersion cooling liquid according to claim 22, characterized in that: The amount of component A is 5-45wt%, and the amount of component B is 15-75wt%.

24. An immersion cooling liquid according to claim 22, characterized in that: The amount of component A is 5-35wt%, and the amount of component B is 25-75wt%.

25. An immersion cooling liquid according to claim 1, characterized in that: The metallocene catalyst system comprises at least one metallocene catalyst, which is an inorganic-organic complex containing at least one cyclopentadienyl or cyclopentadienyl derivative as a ligand and at least one Group IVB transition element as a central atom.

26. An immersion cooling liquid according to any one of claims 1 to 25, characterized in that: The coolant further comprises base oil, which is one or more of API-II, API-III and API-V base oils, and the amount of the component is 20-50wt%.

27. An immersion cooling liquid according to claim 26, characterized in that: The coolant also includes API-III base oil, the component usage is 20-50wt%.

28. An immersion cooling liquid according to claim 26, characterized in that: The API-III base oil has a carbon number of 10-60 and a kinematic viscosity of 1.0-8.0 mm at 100°C. 2 •s -1 .

29. An immersion cooling liquid according to claim 26, characterized in that: The API-III base oils include ULTRA-S series base oils, Yubase series base oils, ADbase series base oils, Nexbase series base oils, ICCSYN series base oils, and SINOPURE series base oils.

30. An immersion cooling liquid according to any one of claims 1 to 25, characterized in that: The coolant may further include one or more additives including antioxidants, corrosion inhibitors, foam suppressants, anti-wear additives, dispersants, detergents, viscosity improvers, and any combination thereof.

31. An immersion cooling liquid according to any one of claims 1 to 25, characterized in that: The coolant may also include one or more antioxidants and antifoaming agents.

32. An immersion cooling liquid according to any one of claims 1 to 25, characterized in that: The coolant also includes an antioxidant 2,6-di-tert-butyl-p-methylphenol and a Xinxing No. 1 composite anti-foaming agent.

33. A method for preparing an immersion cooling liquid according to any one of claims 1 to 32, characterized in that: The preparation method comprises mixing component A and component B to obtain an immersion cooling liquid.

34. The preparation method according to claim 33, characterized in that: The preparation method further comprises mixing the mixture of component A and component B with additives and base oil.

35. The preparation method according to claim 33, characterized in that: After the mixing is completed, the immersion coolant is obtained by filtering.

36. The preparation method according to claim 33, characterized in that: The mixing is performed at room temperature to 60°C.

37. The preparation method according to claim 33, characterized in that: The mixing time is 5-60 min.

38. A battery system, characterized in that: The battery system comprises: a battery and the immersion coolant according to any one of claims 1 to 32, wherein the immersion coolant is in direct contact with the battery.

39. A battery system according to claim 38, characterized in that: At least a portion of the battery is submerged in the immersion coolant.

40. A battery system according to claim 39, characterized in that: The battery is a lithium-ion battery.

41. A power electronic device, characterized in that: The power electronics comprises: a heat generating component and the immersion cooling liquid according to any one of claims 1 to 32, wherein the immersion cooling liquid is in direct contact with the heat generating component.

42. A power electronic device according to claim 41, characterized in that: At least a portion of the heat generating component is immersed in the immersion cooling liquid.

43. A power electronic device according to claim 41, characterized in that: The power electronics are power devices of charging piles, electronic control systems of electric vehicles, and electronic control systems of energy storage batteries.

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