Method for cooling electrical equipment systems by using a dielectric fluid composition with good heat dissipation over a wide temperature range - Patents.com

Abstract

The present invention relates to a method for cooling electrical systems by using a dielectric fluid composition comprising a base fluid comprising hydrogenated oligomers obtained from the oligomerization of butene. The method according to the present invention provides good and consistent heat dissipation for electrical systems over a wide temperature range.

Description

[Technical Field]

[0001] The present invention relates to a method for cooling electrical systems by using a dielectric fluid composition comprising a base fluid A) comprising hydrogenated oligomers obtained from the oligomerization of butene. The method according to the present invention provides excellent and consistent heat dissipation for electrical systems over a wide temperature range.

[0002] Background technology This invention relates to the field of thermal management fluids for direct cooling. More efficient and rapid-charging battery applications require effective cooling systems to dissipate heat from low- to high-voltage applications, such as pure electric vehicles (EVs), hybrid electric vehicles (HEVs), fuel cell electric vehicles, computers, transformers, capacitors, high-voltage cables, and switchgear. Their functions are to provide electrical insulation and suppress corona and arcing. After air and indirect cooling, direct immersion cooling is the most efficient cooling technology. Larger batteries, especially those used in electric vehicles, generate significant amounts of heat during the charging and discharging processes. The optimum temperature for lithium-ion batteries is 20–40°C, and higher temperatures can reduce battery performance and lifespan and potentially lead to battery failure, such as thermal runaway. This is why efficient thermal management fluids are needed.

[0003] Currently available refrigerant fluids are typically hydrocarbon-based refrigerant fluids with a large amount of C17 or longer branched alkyl chains. For example, International Publication No. 2022038313 discloses a renewable paraffin composition containing a large amount of a mixture of C17 and C18 paraffins. The composition should contain less than 10 wt. %, preferably less than 5 wt. % C16, as exemplified in the experimental section. The composition is also described as containing about 4 wt. % C16 iso- and n-paraffins and a total of about 90 wt. % or more of a mixture of C17 and C18 iso- and n-paraffins.

[0004] WO2018078024 describes a heat transfer fluid having a boiling point range of 200-400°C and a boiling point range below 80°C, said fluid containing more than 95% (by weight) isoparaffins and less than 3% naphthenes. This document focuses primarily on specific heat capacity and lubrication properties, but is silent on low-temperature flow properties (low-temperature pour point and viscosity) that are important for wide temperature range applications as thermal management fluids.

[0005] These thermal management compositions containing hydrocarbons with highly branched alkyl chains (predominantly C17 or longer branched alkyl chains) pose problems, particularly with regard to low temperature performance over a wide operating temperature range. Therefore, it is an object of the present invention to provide a new thermal management method for cooling electrical equipment systems, where the thermal management fluid composition should have low electrical conductivity, low viscosity, and excellent thermal properties over a wide temperature range, while maintaining a low pour point, high flash point, and high autoignition temperature.

[0006] Summary of the Invention After thorough research, the inventors of the present invention have surprisingly found that the hydrogenated branched isoparaffinic oligomers of butene according to claim 1, in which the hydrogenated branched isoparaffinic oligomers having alkyl chains of 16 carbon atoms are in predominant amounts, solves the above technical problems and provides excellent and consistent heat release over a wide temperature range, while having excellent low temperature performance and high flash point and autoignition point.

[0007] Therefore, in a first aspect, the invention relates to a method for cooling an electrical equipment system according to claim 1.

[0008] In order to better illustrate the advantages and properties of the claimed cooling method that is the object of the present invention, a graph is attached as a non-limiting example. [Brief explanation of the drawings]

[0009] [Figure 1]1 is a graph showing the heat dissipation performance of different hydrocarbons from -15°C to 40°C. Dielectric fluid composition Comp. HC1 (■) shows a sharp increase in Prandtl number at lower temperatures. Dielectric fluid compositions Comp. HC2 (▲) and HC1 (●) show similar behavior at high and intermediate temperatures. However, dielectric fluid composition HC1 shows a smaller increase in Prandtl number at lower temperatures. Dielectric fluid composition HC2 (◆) shows the lowest Prandtl number with a very low slope throughout the temperature profile.

[0010] MODE FOR CARRYING OUT THE INVENTION Accordingly, the present invention provides a method for cooling an electrical equipment system by using a dielectric fluid composition comprising a base fluid A) comprising hydrogenated oligomers obtained from the oligomerization of butene, wherein the base fluid A) comprises, based on the total weight of the base fluid A), a) 50 to 78% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 16 carbon atoms; b) 22 to 50% (by weight) of a hydrogenated branched isoparaffinic oligomer having an alkyl chain of 20 carbon atoms or an alkyl chain of 24 carbon atoms, or a mixture thereof; c) 0 to 5% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of more than 28 carbon atoms; The hydrogenated oligomers a), b) and c) of the base fluid A) have an iodine number according to DIN 14111 of less than 3 g iodine / 100 g oligomer.

[0011] In other words, the base fluid A) comprises hydrogenated oligomers resulting from the oligomerization of butenes of formula (I), formula (II) and formula (III), [ka] The base fluid A) is, based on the total weight of the base fluid A), a) 50 to 78% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 16 carbon atoms; b) 22 to 50% (by weight) of a hydrogenated branched isoparaffinic oligomer having an alkyl chain of 20 carbon atoms or an alkyl chain of 24 carbon atoms, or a mixture thereof; c) 0 to 5% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of more than 28 carbon atoms; The hydrogenated oligomers a), b) and c) of base fluid A) have an iodine number according to DIN 14111 of less than 3 g iodine / 100 g oligomer.

[0012] According to another preferred embodiment, the base fluid A) comprises hydrogenated oligomers resulting from the oligomerization of butenes of formula (I), formula (II) and formula (III), the content of oligomers resulting from the oligomerization of butenes of formula (III) being less than 10% (by weight), preferably less than 8% (by weight), even more preferably less than 5% (by weight), based on the total weight of the base fluid A). Preferably, the base fluid A) consists of hydrogenated oligomers resulting from the oligomerization of butenes.

[0013] In a preferred embodiment of the present invention, the base fluid A) comprising hydrogenated branched isoparaffin saturated oligomers obtained from the oligomerization of butenes and a further hydrogenation step is free of n-paraffins and aromatic components. More preferably, the base fluid A) consists of hydrogenated branched isoparaffin saturated oligomers obtained from the oligomerization of butenes of formula (I), formula (II) and formula (III), and is free of n-paraffins and aromatic components.

[0014] In another preferred embodiment of the present invention, the base fluid A) comprises, based on the total weight of the base fluid A), a) 55 to 78% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 16 carbon atoms; b) 22 to 45% (by weight) of a hydrogenated branched isoparaffinic oligomer or a mixture thereof having an alkyl chain of 20 carbon atoms or an alkyl chain of 24 carbon atoms; c) 0 to 5% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of more than 28 carbon atoms.

[0015] In yet another preferred embodiment of the present invention, the base fluid A) comprises, based on the total weight of the base fluid A), a) 60 to 75% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 16 carbon atoms; b) 25 to 40% (by weight) of a hydrogenated branched isoparaffinic oligomer having an alkyl chain of 20 carbon atoms or an alkyl chain of 24 carbon atoms, or a mixture thereof; c) 0 to 5% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of more than 28 carbon atoms.

[0016] In an even more preferred embodiment of the present invention, the base fluid A) comprises, based on the total weight of the base fluid A), a) 60 to 70% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 16 carbon atoms; b) 30 to 40% (by weight) of a hydrogenated branched isoparaffinic oligomer having an alkyl chain of 20 carbon atoms or an alkyl chain of 24 carbon atoms, or a mixture thereof; c) 0 to 5% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of more than 28 carbon atoms.

[0017] According to the present invention, the hydrogenated branched isoparaffinic oligomers b) comprise, based on the total weight of the hydrogenated branched isoparaffinic oligomers b), 50 to 98% (by weight), more preferably 70 to 98% (by weight), even more preferably 70 to 80% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 20 carbon atoms, and 2 to 50% (by weight), more preferably 2 to 30% (by weight), even more preferably 20 to 30% (by weight), of hydrogenated branched isoparaffinic oligomers having alkyl chains of 24 carbon atoms It is preferable that the composition consists of:

[0018] The base fluid A) according to the invention is prepared by oligomerization of butenes, the oligomerization of which is carried out using a heterogeneous oligomerization catalyst to form an oligomer product, followed by distillation, in which the oligomers formed during the oligomerization are partially separated from the remaining oligomer product. Finally, the distilled oligomers are hydrogenated. The resulting product is the base fluid A). Preferably, the base fluid A) according to the invention is prepared according to the example of DE 102004018753 A1.

[0019] According to the present invention, base fluid A) comprises hydrogenated oligomers a), b), and c) obtained from the oligomerization of butene, and the hydrogenated oligomers a), b), and c) of base fluid A) have an iodine value according to DIN 14111 of less than 3 g iodine / 100 g oligomer, preferably less than 2 g iodine / 100 g oligomer, more preferably less than 1.5 g iodine / 100 g oligomer. The iodine value is a measure of the relative degree of unsaturation in a component, determined by the incorporation of halogen. In the present invention, the iodine value is the mass (in grams) of iodine consumed by 100 grams of hydrogenated oligomer of base fluid A).

[0020] Preferably, the electrical equipment system is selected from the group consisting of an electric battery, an electric motor, an inverter, an electric transformer, an electric capacitor, a fluid filled transmission line, a fluid filled power cable, a computer, a data server, and power electronics.

[0021] In another preferred embodiment of the present invention, the method of cooling an electrical equipment system according to the present invention is direct immersion cooling, in which heat is removed from the system by circulating a liquid in direct contact with the hot components.

[0022] According to a preferred embodiment of the present invention, the dielectric fluid composition according to claim 1 further comprises a base fluid B) selected from the group consisting of polyol esters, monoesters, saturated hydrocarbons, dicarboxylic acid esters, carbonates, ethers, alcohols, amines, amides, or mixtures thereof. In the context of the present invention, component B) is a different base fluid from base fluid A) as defined in claim 1 and throughout the specification. Thus, preferably, the dielectric fluid composition comprises base fluid A) according to the present invention as a first base fluid and component B) as a second base fluid.

[0023] Preferably, the amounts of base fluid A) and base fluid B) total at least 90% (by weight), and more preferably total at least 95% (by weight), based on the total weight of the dielectric fluid composition.

[0024] Preferably, the dielectric fluid composition may further comprise an additive C) selected from the group consisting of antifoaming agents, seal compatibility agents, antioxidants, yellow metal passivators, rust inhibitors, electrostatic discharge suppressants, demulsifiers, dyes, or mixtures thereof. The additive compounds C) correspond to typical additives used in thermal management fluids and are described in detail, inter alia, in T. Mang, W. Dresel (eds.): "Lubricants and Lubrication," Wiley-VCH, Weinheim 2001; R. M. Mortier, S. T. Orszulik (eds.): "Chemistry and Technology of Lubricants." Preferably, suitable yellow metal passivators are selected from the list consisting of imidazolines, imidazoles, thiazoles, thiadiazoles, triazoles, tolyltriazoles, pyridines, quinolines, morpholines, or mixtures thereof.

[0025] Preferably, suitable rust inhibitors are selected from the list consisting of sulfonates, carboxylates, alkylamines, amine carboxylates, amine borates, phosphates or mixtures thereof.

[0026] Preferably, suitable electrostatic discharge inhibitors are selected from the list consisting of ester quats, imidazolium quats, alkoxyalkyl quats, trialkyl monomethyl quats, monoalkyl trimethyl quats, diamidoamine quats, benzyl quats, ethoxylated ether amines, ether diamines, fatty alcohol ethoxylates, ether amine oxides, ether amine quats or mixtures thereof.

[0027] Preferably, the suitable demulsifier is selected from the list consisting of polyalkoxylated phenols, polyalkoxylated polyols, polyalkoxylated polyamines or mixtures thereof.

[0028] Preferably, suitable antifoaming agents are selected from the list consisting of silicone oils, fluorosilicone oils, fluoroalkyl ethers, polyacrylates or mixtures thereof.

[0029] Preferably, the seal compatibility agent is selected from the list consisting of adipate esters, sebacate esters, neopentyl polyol esters, sulfolane.

[0030] Preferably, suitable antioxidants include phenolic antioxidants and amine antioxidants.

[0031] In a preferred embodiment, the phenolic antioxidant is octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; 4,4'-methylenebis(2,6-di-tert-butylphenol); 4,4'-bis(2,6-di-t-butylphenol); 4,4'-bis(2-methyl-6-t-butylphenol); 2,2'-methylenebis(4-ethyl-6-t-butylphenol); 2,2'-methylenebis(4-methyl- 6-t-butylphenol; 4,4'-butylidenebis(3-methyl-6-t-butylphenol); 4,4'-isopropylidenebis(2,6-di-t-butylphenol); 2,2'-methylenebis(4-methyl-6-nonylphenol); 2,2'-isobutylidenebis(4,6-dimethylphenol); 2,2'-methylenebis(4-methyl-6-cyclohexylphenol); 2,6-di-t-butyl-4-methylphenol; 2,6-di-t- Butyl-4-ethyl-phenol; 2,4-dimethyl-6-t-butylphenol; 2,6-di-t-amyl-p-cresol; 2,6-di-t-butyl-4-(N,N'-dimethylaminomethylphenol); 4,4'-thiobis(2-methyl-6-t-butylphenol); 4,4'-thiobis(3-methyl-6-t-butylphenol); 2,2'-thiobis(4-methyl-6-t-butylphenol); Bis(3-methyl-4-hydroxy-5-t-butyl)

[0033] The phenolic antioxidant is preferably selected from the list consisting of n-octyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate; n-octadecyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate; 2,2'-thio[diethyl-bis-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] or a mixture thereof. Even more preferred phenolic antioxidants are bis-phenolic antioxidants and ester group-containing phenolic antioxidants.

[0032] Examples of the amine antioxidants include monoalkyldiphenylamines, such as monooctyldiphenylamine and monononyldiphenylamine; dialkyldiphenylamines, such as 4,4'-dibutyldiphenylamine, 4,4'-dipentyldiphenylamine, 4,4'-dihexyldiphenylamine, 4,4'-diheptyldiphenylamine, 4,4'-dioctyldiphenylamine and 4,4'-dinonyldiphenylamine; polyalkyldiphenylamines, such as tetrabutyldiphenylamine and tetrahexyldiphenylamine; These include tetraoctyldiphenylamine, tetranonyldiphenylamine, naphthylamine, specifically alpha-naphthylamine, phenyl-alpha-naphthylamine, and further alkyl-substituted phenyl-alpha-naphthylamines, such as butylphenyl-alpha-naphthylamine, pentylphenyl-alpha-naphthylamine, hexylphenyl-alpha-naphthylamine, heptylphenyl-alpha-naphthylamine, octylphenyl-alpha-naphthylamine, and nonylphenyl-alpha-naphthylamine.Among these, diphenylamine is more preferred than naphthylamine in terms of antioxidant effect.

[0033] According to a preferred embodiment of the present invention, the dielectric fluid composition according to the present invention comprises 2 to 100% (by weight) of base fluid A), 0 to 98% (by weight) of base fluid B), and 0 to 10% (by weight) of additive C), based on the total weight of the dielectric fluid composition. More preferably, the total amounts of A), B), and C) add up to at least 90% (by weight), more preferably at least 95% (by weight), and even more preferably 100% (by weight), based on the total weight of the dielectric fluid composition according to the present invention.

[0034] According to a preferred embodiment of the present invention, the base fluid A) has a pour point of less than minus eighty degrees Celsius (-80°C) according to ASTM D5950.

[0035] In the present invention, the Prandtl number (Pr) is calculated by the following formula: The Prandtl number is a dimensionless quantity that correlates the viscosity of a fluid with its thermal conductivity (see Bastian E. Rapp, in Microfluidics: Modeling, Mechanics and Mathematics, 2017). The Prandtl number is given as follows: Pr=θ / α=momentum diffusivity / thermal diffusivity=(μ / ρ) / (k / (c p ρ))=c p μ / k During the ceremony θ: Momentum diffusivity (kinetic viscosity) θ=μ / ρ; SI unit: m 2 / s α: Thermal diffusivity; SI unit: m 2 / s μ: dynamic viscosity; SI unit: Pa s=N s / m 2 k: Thermal conductivity; SI unit: W / (m K) c p : specific heat; SI unit: J / (kg K) ρ: Density; SI unit: kg / m 3

[0036] As shown in the experimental section below, the inventors of the present invention have surprisingly found that the base fluid A) of the method of the present invention all have low Prandtl numbers over a wide temperature range. The base fluid A) of the present invention has high thermal conductivity and low viscosity, which are confirmed to be advantageous for thermal management in electrical devices. This means that the dielectric fluid of the present invention can efficiently exchange heat with electrical devices. In fact, the higher the thermal conductivity, the better the heat transfer capacity. Furthermore, the fluid exhibits significant low-temperature flow properties.

[0037] According to a preferred embodiment, the base fluid A) of the present invention has a Prandtl number of less than 60 at 40° C. and a pressure of 1013 hPa, more preferably less than 55 at 40° C. and a pressure of 1013 hPa.

[0038] Example The present invention will now be described in more detail with reference to examples and comparative examples, without intending to limit the scope of the invention.

[0039] Abbreviation Autoignition temperature according to AIT DIN 51794 Comp. HC1 Yubase 3 (KV40 11.80 mm) from SK Lubricants, a distillate containing iso- and n-paraffins with alkyl chains of more than 20 carbon atoms. 2 / s hydrotreated light paraffin base oil) Comp.HC2 PAO 2 corresponding to 1-decene dimer Cp Specific heat capacity according to the temperatures shown in Table 1 and ASTM D7896-19 Elect. Cond. conductivity was measured at 25°C according to ASTM D2624. FP Flash Point ASTM D93 HC1 64 wt% C16 / 34 wt% C20 and C24 hydrogenated branched isoparaffinic hydrocarbons / remaining high boiling hydrocarbons (C28 and above hydrogenated branched isoparaffinic hydrocarbons) HC2 78 wt% C16 / 22 wt% C20 and C24 hydrogenated branched isoparaffinic hydrocarbons KV Kinematic viscosity according to ASTM D445 at temperatures shown in Table 1 PN Prandtl number (1 atm) at the temperatures and 1013 hPa shown in Table 1 Pour point according to PP ASTM D5950 λ Thermal conductivity according to ASTM D7896-14 and temperatures shown in Table 1 δ Temperatures shown in Table 1 and densities according to DIN EN ISO 12185

[0040] Test Method The kinematic viscosity of the dielectric fluid compositions was measured at the temperatures shown in Table 1 (ie, 40° C., 20° C., and −15° C.) and according to ASTM D445.

[0041] The specific heat capacity and thermal conductivity were measured at the temperatures shown in Table 1 using the hot wire method according to ASTM D7896-19.

[0042] Pour point (PP) was measured according to ASTM D5950.

[0043] Flash points were measured using a closed cup Pensky Martin apparatus according to ASTM D93.

[0044] Conductivity was measured at 25°C according to ASTM D2624.

[0045] The density was determined in accordance with DIN EN ISO 12185 at the temperatures indicated in Table 1.

[0046] The autoignition temperature was determined according to DIN 51794.

[0047] Quantitative analysis of the thermal management fluid components was performed by gas chromatography. The analysis was performed using an Agilent DB-5 5% diphenyl / 95% dimethylpolysiloxane quartz capillary column (30 m × 0.25 mm × 0.25 μm) connected to a flame ionization detector. The temperature program was 50 °C for 4 min, which was increased to 350 °C in 20 min. The flow rate was 1.5 mL / min for 34 min, which was increased to 2 mL / min. The injection temperature was 280 °C, and the detector temperature was 350 °C. Helium gas was used as the carrier gas, and the column flow rate was adjusted to 1.5 mL / min.

[0048] Mass spectrometry was used to identify the chromatographic peaks. Analysis was performed using an Agilent DB-5 5% diphenyl / 95% dimethylpolysiloxane quartz capillary column (30 m × 0.25 mm × 0.25 μm) connected to a mass spectrometer. The temperature program was 80 °C for 2 min, which was then increased to 320 °C in 22 min. The injection temperature was 250 °C, and the carrier flow was 1.1 mL / min.

[0049] The degree of hydrogenation of the hydrogenated oligomers a), b) and c) obtained from the oligomerization of the butenes of the base fluid was determined according to DIN 14111.

[0050] Preparation of base fluid The base fluid HCl is prepared analogously to the examples of DE 102004018753 A1. The butene compounds of formulae (I), (II) and (III) are oligomerized in the presence of a nickel catalyst. The C16 oligomers formed are then separated by distillation and finally hydrogenated.

[0051] Analysis of the product shows that the base fluid consists of 64 wt% C16 / 34 wt% C20 and C24 branched isoparaffinic hydrocarbons / remaining high boiling hydrocarbons (C28 and above branched isoparaffinic hydrocarbons).

[0052] The iodine number according to DIN 14111 of the base fluid HC1 is 1.3 g iodine / 100 g oligomer.

[0053] Base fluid HC2 is prepared in the same manner as base fluid HC1. The product obtained after further purification by distillation has the following composition:

[0054] Analysis of the product shows that the base fluid consists of 78 wt% C16 / 22 wt% C20 and C24 branched isoparaffinic hydrocarbons.

[0055] The iodine number according to DIN 14111 of the base fluid HC1 is 1.3 g iodine / 100 g oligomer.

[0056] The comparative base fluid Comp. HC1 is a distillate containing iso- and n-paraffins with alkyl chains of more than 20 carbon atoms (hydrotreated light paraffinic base oil with a KV40 of 11.80 mm2 / s).

[0057] The comparative base fluid Comp.HC2 corresponds to a 1-decene based dimer.

[0058] An example of a base fluid according to the invention (Base Fluid A) of claim 1) and an example of a comparative base fluid (Comp. HC) are shown in Table 1 below, along with their respective physical properties.

[0059] [Table 1]

[0060] As shown in Table 1 above, the C16-enriched hydrocarbon-based fluids according to the present invention (Examples HC1 and HC2) have very good heat transfer properties combined with low viscosity and excellent low temperature performance. In contrast, Comparative Examples Comp.HC1 and Comp.HC2 do not combine all of the properties shown above together and therefore do not perform as efficiently.

[0061] Furthermore, Example HC1, a C16-enriched hydrocarbon-based fluid according to the present invention, exhibits an acceptable flash point (124°C), but surprisingly, the autoignition point of Example HC1 is superior to that of Comp. HC1 (275°C vs. 260°C, respectively). This, of course, is a major advantage in preventing autoignition when an electrical system malfunctions causing thermal runaway.

[0062] Table 2 below shows the change in Prandtl Index values ​​for several thermal management fluid compositions according to the present invention and several comparative thermal management fluids over a wide range of temperatures. The slope indicates the efficiency of the Prandtl number over a wide temperature range, with a lower increase indicating better efficiency. The intercept represents the Prandtl number at 0°C. Again, the lower the Prandtl number, the better the heat removal for the electrical system. This is also reflected in Figure 1 of the present invention.

[0063] [Table 2]

[0064] The comparative thermal management fluid Comp. HC1 exhibits a sharp increase in slope at 30° C. and therefore does not provide a stable thermal management effect over a wide temperature range.

[0065] The comparative thermal management fluid composition Comp. HC2 also exhibits an increased Prandtl Index value. Even though the results are better than the comparative thermal management fluid Comp. HC1, the slope of the base fluid Comp. HC2 is steeper than the slopes of the inventive base fluids HC1 and HC2 according to the present invention.

[0066] In particular, the base fluid HC2 of the present invention exhibits the lowest slope. In fact, the slope of the Prandtl Index values ​​should be stable over a wide temperature profile. This is observed with the inventive thermal management fluid composition according to the present invention, and a clear improvement can be observed.

[0067] The above experimental data demonstrate that the C16-enriched hydrocarbon-based fluid A) of the present invention has a low and stable Prandtl number over a wide temperature range. This confirms that the dielectric fluid composition of the present invention has high thermal conductivity and low viscosity over a wide temperature range, which is advantageous for effective circulation and pumping to dissipate heat within electrical devices. Furthermore, the base fluid A) of the present invention has excellent low-temperature flow properties (very low pour point values ​​as shown in Table 1).

Claims

1. 1. A method for cooling an electrical equipment system by using a dielectric fluid composition comprising a base fluid A) comprising a hydrogenated oligomer obtained from the oligomerization of butene, said base fluid A) comprising, based on the total weight of said base fluid A), a) 50 to 78% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 16 carbon atoms; b) 22 to 50% (by weight) of a hydrogenated branched isoparaffinic oligomer having an alkyl chain of 20 carbon atoms or an alkyl chain of 24 carbon atoms, or a mixture thereof; c) 0-5% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains greater than 28 carbon atoms; 10. A process according to claim 1, wherein the hydrogenated oligomers a), b) and c) of the base fluid A) have an iodine number according to DIN 14111 of less than 3 g iodine / 100 g oligomer.

2. 10. The method of claim 1, wherein said base fluid A) is free of n-paraffins and aromatic components.

3. The base fluid A) comprises, based on the total weight of the base fluid A), a) 55 to 78% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 16 carbon atoms; b) 22 to 45% (by weight) of hydrogenated branched isoparaffinic oligomers or mixtures thereof having alkyl chains of 20 carbon atoms or alkyl chains of 24 carbon atoms; c) 0-5% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of more than 28 carbon atoms.

4. 4. The method according to claim 1, wherein the hydrogenated oligomers a), b) and c) of the base fluid A) have an iodine value according to DIN 14111 of less than 2 g iodine / 100 g oligomer, preferably less than 1.5 g iodine / 100 g oligomer.

5. The base fluid A) comprises, based on the total weight of the base fluid A), a) 60 to 75% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 16 carbon atoms; b) 25 to 40% (by weight) of hydrogenated branched isoparaffinic oligomers or mixtures thereof having alkyl chains of 20 carbon atoms or alkyl chains of 24 carbon atoms; c) 0-5% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of more than 28 carbon atoms; 5. The method of claim 1, comprising:

6. The base fluid A) comprises, based on the total weight of the base fluid A), a) 60-70% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 16 carbon atoms; b) 30 to 40% (by weight) of hydrogenated branched isoparaffinic oligomers or mixtures thereof having alkyl chains of 20 carbon atoms or alkyl chains of 24 carbon atoms; c) 0-5% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of more than 28 carbon atoms; 6. The method of claim 1, comprising:

7. 7. The method according to any one of claims 1 to 6, wherein the hydrogenated branched isoparaffinic oligomers b) consist of 50 to 98% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 20 carbon atoms and 2 to 50% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 24 carbon atoms, based on the total weight of hydrogenated branched isoparaffinic oligomers b).

8. 8. The method of claim 7, wherein the hydrogenated branched isoparaffinic oligomers b) consist of 70 to 98% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 20 carbon atoms and 2 to 30% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 24 carbon atoms, based on the total weight of hydrogenated branched isoparaffinic oligomers b).

9. 9. The method of claim 8, wherein the branched isoparaffinic oligomers b) consist of 70 to 80% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 20 carbon atoms and 20 to 30% (by weight) of hydrogenated branched isoparaffinic oligomers having alkyl chains of 24 carbon atoms, based on the total weight of hydrogenated branched isoparaffinic oligomers b).

10. 10. The method of any one of claims 1 to 9, wherein the electric equipment system is selected from the group consisting of an electric battery, an electric motor, an inverter, an electric transformer, an electric capacitor, a fluid-filled transmission line, a fluid-filled power cable, a computer, a data server, and power electronics.

11. 11. The method of any one of claims 1 to 10, wherein the method of cooling the electrical equipment system is direct immersion cooling.

12. 12. The method of any one of claims 1 to 11, wherein the dielectric fluid composition further comprises a base fluid B) selected from the group consisting of polyol esters, monoesters, saturated hydrocarbons, dicarboxylic acid esters, carbonates, ethers, alcohols, amines, amides, or mixtures thereof.

13. 13. The method of any one of claims 1 to 12, wherein the dielectric fluid composition further comprises an additive C) selected from the group consisting of an antifoaming agent, a seal compatibility agent, an antioxidant, a yellow metal passivator, a rust inhibitor, an electrostatic discharge suppressant, a demulsifier, a dye, or a mixture thereof.

14. 14. The method of any one of claims 1 to 13, wherein the dielectric fluid composition comprises 2 to 100% (by weight) of base fluid A), 0 to 98% (by weight) of base fluid B), and 0 to 10% (by weight) of additive C), based on the total weight of the dielectric fluid composition.

15. 15. The method of any one of claims 1 to 14, wherein the amounts of A) to C) together amount to at least 90% (by weight), more preferably at least 95% (by weight), and even more preferably 100% (by weight), based on the total weight of the dielectric fluid composition.

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