Heat transfer fluids for indirect liquid cooling systems

Abstract

The invention relates to the use of a heat transfer fluid based on aliphatic diesters for indirect cooling of electronic components.

Description

[0001] Description Field of the invention

[0002] The present application relates to the use of aliphatic diester-based heat transfer fluids for the indirect cooling of electronic components. Background

[0003] Nowadays, heat dissipation is a relevant topic in the design and operation of electronic devices, especially for devices comprising electronic circuit components, including densely packed ones, and in particular of the semiconductor type, such as integrated circuit components. For example, in modern server farms, as well as in telecommunication centers and data centers, heat dissipation is a serious problem, where the large number of hard disks, microprocessors or central processing units (CPUs) and their ever-increasing processing and storage power make heat dissipation a critical factor to prevent overheating of such electronic components, which can lead to malfunction and irreparable damage to these electronic components.

[0004] Therefore, in the field of design and operation of electronic devices, there is a strong felt need to find and develop new and improved cooling systems.

[0005] Nowadays, different cooling systems exist, which employ various technologies to transfer heat away from electronic components to maintain suitable operating temperatures for the electronic components; cooling systems can be classified based on the type of heat transfer fluid and based on whether the heat transfer occurs in direct or indirect contact with the electronic components.

[0006] Indirect cooling systems are designed to dissipate the heat generated by electronic components without letting the heat transfer fluid come into direct contact with such components. Depending on the physical state and type of the heat transfer fluid and on the heat dissipation mechanism, common types of indirect cooling systems are: - Air cooling systems: this type of cooling system is the most widely used method for indirectly cooling electronic components. It utilizes fans and heat sinks to dissipate heat. Fans, whether active (powered) or passive (relying on natural convection), enhance the airflow around the heat sink, thus improving heat dissipation. Air cooling systems are relatively simple, cost-effective, and suitable for many applications. However, their effectiveness can be limited in high-power or densely packed systems.

[0007] - Phase change cooling systems: they involve the use of a refrigerant that changes from a liquid state to a gaseous state and back to a liquid state. The cooling process begins with the refrigerant absorbing heat from the electronic components, causing it to evaporate into a gas. Then, the gaseous refrigerant condenses back into a liquid through a heat exchanger, releasing the absorbed heat. The liquid refrigerant then flows back to the components, repeating the cycle.

[0008] - Liquid cooling systems: Liquid cooling systems use a heat transfer fluid in liquid state to transfer heat away from electronic components. This method is more efficient than air cooling systems and is less expensive and requires less complex systems than phase change cooling systems.

[0009] Generally, indirect liquid cooling systems comprise a cooling circuit for circulating a heat transfer fluid, a pump system circulating the heat transfer fluid throughout the cooling circuit, a heat conducting element coupled with the electronic components to absorb heat from the electronic components and transfer said heat to the heat transfer fluid, a heat exchanger for dissipating the heat absorbed by the heat transfer fluid and cooling the heat transfer fluid, and optionally a reservoir containing the heat transfer fluid. In these systems, the heat transfer fluid is pumped by the pump system through the cooling circuit, which is in thermal contact with the heat conducting element and absorbs heat from the heat conducting element in this way. Thereby, the heat transfer fluid dissipates the heat generated by the electronic components and is then cooled by the heat exchanger before recirculating in the circuit or stored in the reservoir when cooling in the circuit before subsequent recirculation.

[0010] Therefore, in view of the rheological and hydrodynamic properties of the heat transfer fluid, its thermal and chemical stability properties and its thermal capacity properties, the heat transfer fluid used for liquid cooling systems plays a crucial role for the heat dissipation and the performance of the system itself. Currently, the fluids known for indirect liquid cooling are water and specialized fluids, among which fluids containing PFAS (per- and polyfluorinated substances) have gained widespread use. SUMMARY

[0011] However, the Applicant noticed that even if water is a common choice due to its excellent thermal properties and availability, it is necessary to implement complex and expensive purification systems to overcome the risks of corrosion and fouling, which can cause malfunctions and damages to the cooling system and to the electronic components. At the same time, water has a limited working temperature window and this further limits the cooling efficiency of the systems using water.

[0012] The Applicant also noticed that even if specialized fluids, such as those containing PFAS, have enhanced properties, such as a higher boiling point or better corrosion resistance, allowing their use in specialized applications, these compounds have recently shown technical and application limitations.

[0013] In fact, PFAS tend to have a high volatility and this causes a partial loss of these fluids due to their evaporation upon exposure to high temperature components. This high volatility and partial loss of PFAS requires their refilling into the heat exchange system, with the simultaneous increase of the operator exposure to said fluids.

[0014] At the same time, PFAS also raise concerns related to their environmental impact, making their use particularly critical and also requiring the adoption of complex and expensive containment systems to avoid any dispersion and / or contact with the external environment during the operation, transport, maintenance operations of the systems and devices in which they are used.

[0015] It is therefore the object of the present application to provide a new heat transfer fluid which is able to overcome the functional and environmental limits of the heat transfer fluids currently used in indirect liquid cooling systems of electronic components, and the Applicant has surprisingly found that a heat transfer fluid based on a specific class of aliphatic diesters can be effectively used for such purpose.

[0016] In particular, in a first aspect, the present application relates to the use of a heat transfer fluid for cooling electronic components with an indirect liquid cooling system, the heat transfer fluid comprising at least one diester of at least one C2-C9 aliphatic diol with at least one linear or branched C2-C7 aliphatic monocarboxylic acid.

[0017] Surprisingly, the Applicant has indeed found that such diesters show suitable rheological and hydrodynamic properties, thermal and chemical stability properties, and thermal capacity properties, making them effectively suitable for use in indirect liquid cooling systems for dissipating the heat generated by electronic components.

[0018] Advantageously, the diesters can also provide a more environmentally sustainable solution with respect to PFAS-based specialized fluids, making the operation, transport and maintenance operations of the cooling system less critical.

[0019] Notably, the diesters provide an excellent alternative to PFAS-based fluids, particularly due to their significantly low dynamic viscosity at very low temperatures. This particular property enables efficient pumping and circulation of the heat transfer fluid even in the most severe cold environments. Moreover, these esters have a high flash point and low volatility, ensuring both safety and effective cooling of electronic equipment at elevated temperatures. Their unique combination of low viscosity, high flash point and low volatility makes these diesters an ideal choice for multiple types of indirect electronic equipment cooling systems, providing efficient thermal management for a range of electronic devices, offering reliable and efficient heat transfer capabilities while prioritizing safety and performance.

[0020] These fluids have a low viscosity, facilitating the efficient transfer of heat away from electronic components in different types of indirect cooling systems. The high flash point and low volatility of these esters at the same time ensure safe operation and also minimize the risk of fire or malfunction in such systems.

[0021] For example, such diesters can be used as working fluids in heat pipes or in narrow channels or ducts, which are widely used for the indirect cooling of electronic devices. These diesters are able to achieve efficient heat transfer under such conditions, allowing heat to be absorbed from a source and dissipated at a sink. The low viscosity of the fluids at working temperatures ensures optimal circulation through narrow channels or ducts and, therefore, enhances overall cooling performance even with limited contact time and heat transfer surface area.

[0022] This is a very stringent requirement on viscosity compared to direct cooling systems, in particular those using immersion baths, in which the heat transfer fluid is not forced through narrow spaces and in which the contact time and heat transfer surface area are greater than in indirect cooling systems.

[0023] Therefore, in indirect cooling systems with closed loops, such diesters can be advantageously used as heat transfer fluids circulating through the closed loop system. Since these fluids have a low dynamic viscosity at working temperatures, they can easily flow through narrow channels and complex cooling structures, efficiently carrying away heat from electronic components. The high flash point and low volatility enhance the safety and reliability of the cooling system.

[0024] Therefore, the diesters can also be effectively used in cold plate cooling systems, in which they can advantageously flow through metal plates in direct contact with electronic components. The low viscosity of these fluids allows efficient heat transfer, enabling effective cooling of high-power electronic devices. The high flash point and low volatility of the esters ensure safe operation and minimize the risk of fluid leakage or system damage.

[0025] In this way, more effective and safe use of electronic devices installed with electronic components can be achieved by improving their thermal management and avoiding or at least significantly reducing overheating phenomena of the electronic components installed therein, which can lead to malfunction and irreparable damage of the electronic components.

[0026] Furthermore, the low viscosity of the diesters at low temperatures allows a high and constant temperature difference to be set and used between the hot electronic components and the heat transfer fluid, making heat exchange more effective and rapid. Maintaining the temperature as constant as possible, avoiding thermal variations or eliminating thermal variations as quickly as possible is in fact a fundamental requirement for cooling electronic components and in particular electronic components based on semiconductors.

[0027] In a further aspect, the present application also relates to a method for cooling an electronic component with an indirect liquid cooling system, wherein the liquid cooling system comprises a heat transfer fluid as defined in the first aspect of the present application.

[0028] In still further aspects, the present application also relates to an electronic device comprising: at least one electronic component; and at least one indirect liquid cooling system adapted to cool the electronic component and comprising at least one heat transfer fluid as defined in the first aspect of the application.

[0029] The advantages of the methods and electronic devices according to these aspects of the application have been disclosed in relation to the use according to the first aspect of the application, and are not repeated here. DETAILED DESCRIPTION

[0030] In a first aspect, the present application relates to the use of a heat transfer fluid for cooling an electronic component with an indirect liquid cooling system, the heat transfer fluid comprising at least one diester of at least one C2-C9 aliphatic diol with at least one linear or branched C2-C7 aliphatic monocarboxylic acid.

[0031] Surprisingly, the Applicant has indeed found that such diesters show suitable rheological and hydrodynamic properties, thermal and chemical stability properties, thermal capacity properties, making them effectively suitable for use in an indirect liquid cooling system for dissipating the heat generated by an electronic component.

[0032] Within the framework of this description and in the subsequent claims, unless otherwise indicated, all numerical entities expressing quantities, parameters, percentages, etc. should be understood in all cases to be preceded by the term "approximately". As used herein, the term "approximately" will be understood by those of ordinary skill in the art and will vary to some degree according to the context in which it is used. As used herein, when referring to a measurable value such as an amount, a time period, and the like, the term "approximately" means including a variation of ±20% or ±10%, including ±5%, ±1% and ±0.1% from the specified value, as such variations are appropriate to perform the disclosed methods.

[0033] Furthermore, all ranges of numerical entities include all possible combinations of the maximum and minimum values and include all possible intermediate ranges, except those specifically indicated herein below.

[0034] Unless otherwise defined, all technical and scientific terms used herein generally have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0035] As used herein, the articles "a" and "an" refer to one or to more than one (i.e. to at least one) of the grammatical object of the article. By way of example, "an element" means one element or more than one element.

[0036] As used herein, the expression "indirect liquid cooling system" means a cooling system in which the heat transfer fluid is (or remains) in liquid state or predominantly in liquid state during the operation of the system, and in which said heat transfer fluid is not in direct contact with the component that has to be cooled, while being adapted to cool this component. In particular, when referring to electronic components, an indirect liquid cooling system is a cooling system in which the heat transfer fluid is not in direct contact with such electronic components, for example by interposing a different element that is thermally coupled with the electronic component and made of a thermally conductive material such as copper or other metals, which is interposed between the electronic component and the heat transfer fluid. This thermally conductive element prevents the fluid from being in direct contact with the electronic component and has the function of transferring heat. In indirect cooling systems, according to the design of the system, this different element interposed between the electronic component and the heat transfer fluid can have different shapes and configurations (heat sink, wall in a tube, or plate).

[0037] In indirect cooling, heat transfer involves both conduction and convection, since the fluid exchanges heat with a material that is thermally coupled with the component to be cooled, and the heat exchange is mainly influenced by the temperature difference between the component to be cooled and the heat transfer fluid.

[0038] The present application can present one or more of the features disclosed below in one or more of the above aspects.

[0039] According to the present application, the heat transfer fluid comprises at least one diester of at least one C2-C9 aliphatic diol with at least one linear or branched C2-C7 aliphatic monocarboxylic acid.

[0040] Preferably, said C2-C9 aliphatic diol is selected from the group consisting of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, diethylene glycol, triethylene glycol, dipropylene glycol, neopentyl glycol, 2-methyl-1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, and mixtures thereof.

[0041] Preferably, the aliphatic diol of the diester according to the present application is a C3-C6 aliphatic diol, more preferably selected from the group consisting of 1,3- propanediol, 1,4-butanediol, 1,3-butanediol, diethylene glycol, triethylene glycol, dipropylene glycol, neopentyl glycol, 2-methyl-1,3-propanediol, 1,5-pentanediol, 1,6- hexanediol, 3-methyl-1,5-pentanediol and mixtures thereof. Even more preferably, the aliphatic diol of the diester according to the present application is a C3-C5 aliphatic diol, still even more preferably selected from the group consisting of 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, diethylene glycol, neopentyl glycol, 2-methyl-1,3-propanediol, 1,5-pentanediol and mixtures thereof.

[0042] In a preferred embodiment, the aliphatic diol of the diester according to the present application is selected from the group consisting of 1,2-propanediol, 1,3-propanediol, neopentyl glycol and mixtures thereof, preferably selected from the group consisting of 1,2-propanediol, 1,3-propanediol and mixtures thereof.

[0043] In an embodiment of the present application, the linear or branched C2-C7 aliphatic monocarboxylic acid of the diester according to the present application is a C3-C5 aliphatic monocarboxylic acid, more preferably selected from the group consisting of propionic acid, butyric acid, isobutyric acid, 2-methylbutyric acid, 3-methylbutyric acid, valeric acid and mixtures thereof; more preferably selected from the group consisting of 2-methylbutyric acid, 3-methylbutyric acid, valeric acid and mixtures thereof.

[0044] In another embodiment of the present application, the linear or branched C2-C7 aliphatic monocarboxylic acid of the diester according to the present application is a C5-C7 aliphatic monocarboxylic acid; preferably, in such an embodiment, the at least one monocarboxylic acid of the diester according to the present application is a C5 acid. More preferably, in such an embodiment, the aliphatic monocarboxylic acid of the diester according to the present application is a C5 acid, optimally valeric acid.

[0045] In a preferred embodiment of the present application, the diester is selected from the group consisting of neopentyl glycol dipentanoate, 1,2-propanediol dipentanoate, 1,3-propanediol dipentanoate, 2-methyl-1,3-propanediol dipentanoate and mixtures thereof, more preferably 1,2-propanediol dipentanoate, 1,3-propanediol dipentanoate and mixtures thereof.

[0046] The diols, monocarboxylic acids and diesters as defined above do indeed surprisingly show a combination of properties, such as a low dynamic viscosity at temperatures up to -55°C combined with a flash point higher than 125°C and a high volume resistivity, making them particularly suitable and operationally effective in an indirect electronic cooling system in a wide temperature range window from -55°C to 125°C and thus particularly effective as a component of an indirect liquid cooling system for electronic components as a heat transfer fluid.

[0047] In addition to the diesters, the heat transfer fluid according to the application can advantageously comprise one or more other components, among which, for example, synthetic or natural esters, mineral oils, polyethers such as polyalkylene glycols, polyolefins, additives.

[0048] In an embodiment, the heat transfer fluid according to the application comprises at least one diester as defined above and at least one C6-C 12 aliphatic monoalcohol and at least one linear or branched C2-C 12 at least one monoester of an aliphatic monocarboxylic acid, for example a monoester such as 2-propylheptyl valerate, 2-ethylhexyl heptanoate.

[0049] Preferably, the heat transfer fluid according to the application comprises at least one additive chosen from the group consisting of antioxidants, pour point depressant additives, antifoams, anticorrosion agents, viscosity improvers, wear-resistance and / or extreme-pressure additives, friction modifiers, detergents, dispersants and mixtures thereof.

[0050] Advantageously, the heat transfer fluid according to the application exhibits one or more of the following characteristics: - a dynamic viscosity of less than 50 mPa*s at -30°C; - a flash point higher than 125°C; - a volume resistivity higher than 0.1 mega-ohm-centimeter (T*cm) at 25°C.

[0051] In addition, the heat transfer fluid according to the application exhibits suitable thermal capacity and thermal conductivity properties for cooling electronic components.

[0052] Preferably, the heat transfer fluid according to the application is in the liquid state during the operation of the indirect liquid cooling system.

[0053] In the indirect liquid cooling system according to the application, the heat transfer fluid has the function of dissipating the heat generated by the electronic components, which can advantageously be installed in an electronic device.

[0054] In indirect cooling, heat transfer involves both conduction and convection, since the fluid exchanges heat with the material that is thermally coupled to the components to be cooled, and the heat exchange is mainly influenced by the temperature difference between the components to be cooled and the heat transfer fluid. Another well-known factor that influences the heat exchange is the amount of heat exchange fluid used, which in turn is limited by the design of the cooling system.

[0055] Due to the advantageous properties of the heat transfer fluid according to the present application, the indirect liquid cooling system is not particularly limited and can be any type of indirect liquid cooling system for indirectly cooling electronic components known to the person skilled in the relevant technical field.

[0056] Preferably, the indirect liquid cooling system according to the present application comprises at least one thermally conductive element thermally coupled with said electronic component, and said thermally conductive element is adapted to transfer heat from said electronic component to said heat transfer fluid. More preferably, said thermally conductive element is selected from the group consisting of a wall, a layer, a heat sink, a cold plate, a heat pipe and a vapour chamber.

[0057] Preferably, said indirect liquid cooling system comprises: a liquid cooling circuit adapted to circulate said heat transfer fluid; a pump adapted to pump said heat transfer fluid throughout said liquid cooling circuit; a heat exchanger adapted to cool said heat transfer fluid; and optionally, a reservoir adapted to contain said heat transfer fluid.

[0058] According to the present application, the electronic component can be any type of electronic component that tends to generate heat when in use and therefore needs to be cooled, or an electronic component that can suffer from malfunction and irreparable damage upon overheating.

[0059] Preferably, said electronic component is selected from the group consisting of a microprocessor, a semiconductor die, a power control semiconductor, an electrochemical cell, an electrical distribution switch gear, a power transformer, a circuit board, a multi-chip module, a hard disk, a central processor, a packaged or unpackaged semiconductor device, a fuel cell, a laser and a semiconductor integrated circuit.

[0060] More preferably, said electronic component is selected from the group consisting of a microprocessor, a semiconductor die, a power control semiconductor, a circuit board, a multi-chip module, a hard disk, a central processor, a packaged or unpackaged semiconductor device and a semiconductor integrated circuit.

[0061] Preferably, said electronic component is mounted in an electronic device.

[0062] According to the present application, the electronic device can be any type of electronic device in which an electronic component is mounted, and is not particularly limited. Preferably, said electronic device is selected from the group consisting of a computer, a server, a server farm, a telecommunication centre and a data centre.

[0063] Thanks to the properties of the heat transfer fluid according to the present application, a more efficient and safe cooling method of electronic components can be achieved by improving the thermal management of electronic components and avoiding or significantly reducing overheating phenomena that can cause malfunctions and irreparable damages.

[0064] Therefore, in a further aspect, the present application also relates to a method for cooling an electronic component with an indirect liquid cooling system, wherein said liquid cooling system comprises a heat transfer fluid comprising at least one diester of at least one C2-C9 aliphatic diol with at least one linear or branched C2-C7 aliphatic monocarboxylic acid, as defined above in the first aspect of the present application.

[0065] The advantages and preferred features of the method have been defined above in relation to the first aspect of the present application, and are therefore not repeated here.

[0066] In the method according to this aspect of the present application, a heat transfer fluid as defined in the first aspect of the present application is used. Therefore, the preferred features of this heat transfer fluid have been defined above in relation to the heat transfer fluid in the first aspect of the present application, and are therefore not repeated here.

[0067] The preferred features of the indirect liquid cooling system and of the electronic component of the method according to the present application have also been defined above in relation to the indirect liquid cooling system and to the electronic component in the first aspect of the present application, and are therefore not repeated here.

[0068] Preferably, the method for cooling an electronic component according to the present application comprises the step of transferring heat from said electronic component to said heat transfer fluid.

[0069] In a preferred embodiment, when in the method according to the present application the indirect liquid cooling system comprises at least one heat-conducting element thermally coupled with said electronic component, in said step of transferring heat, said heat-conducting material is adapted to transfer heat from said electronic component to said heat transfer fluid.

[0070] Thanks to the use of a heat transfer fluid comprising diesters as defined above in an indirect liquid cooling system for cooling electronic components, a more efficient and safe use of electronic devices in which electronic components are installed can be achieved by improving their thermal management and avoiding or significantly reducing overheating phenomena that can cause malfunctions and irreparable damages.

[0071] Therefore, in a further aspect, the present application also relates to an electronic device comprising: at least one electronic component; and at least one indirect liquid cooling system adapted to cool the electronic component and comprising at least one heat transfer fluid comprising at least one diester of a C2-C9 aliphatic diol with at least one linear or branched C2-C7 aliphatic mono carboxylic acid, as defined above in the first aspect of the present application.

[0072] Advantages and preferred features of the electronic device according to the present application have been disclosed with respect to the use and method according to the other aspects of the present application and are not repeated here.

[0073] In the device according to this aspect of the present application, a heat transfer fluid and an indirect liquid cooling system as defined in the other aspects of the present application are used. Therefore, the preferred features of the heat transfer fluid and the indirect liquid cooling system have been defined above with respect to the heat transfer fluid and the indirect liquid cooling system in the other aspects of the present application and are therefore not repeated here.

[0074] Preferably, the electronic device according to this aspect of the present application is selected from the group consisting of a computer, a server, a server cluster, a telecommunication center and a data center.

[0075] Preferably, in the device according to this aspect of the present application, the electronic component of the device according to this aspect of the present application is selected from the group consisting of a microprocessor, a semiconductor wafer, a power control semiconductor, an electrochemical cell, a power distribution switchgear, a power transformer, a circuit board, a multi-chip module, a hard disk, a central processor, a packaged or unpackaged semiconductor device, a fuel cell, a laser and a semiconductor integrated circuit.

[0076] More preferably, the electronic component is selected from the group consisting of a microprocessor, a semiconductor wafer, a power control semiconductor, a circuit board, a multi-chip module, a hard disk, a central processor, a packaged or unpackaged semiconductor device and a semiconductor integrated circuit.

[0077] In a further aspect, the present application also relates to a heat transfer fluid for cooling an electronic component comprising at least one diester of a C2-C9 aliphatic diol with at least one linear or branched C2-C7 aliphatic mono carboxylic acid and at least one additive selected from the group consisting of an antioxidant, a pour point depressant additive, an antifoam agent, an anticorrosion agent, a viscosity improver, a wear and / or extreme pressure additive, a friction modifier, a detergent, a dispersant and mixtures thereof.

[0078] Advantages and preferred features of the heat transfer fluid according to the present application have been disclosed with respect to the use and method according to the other aspects of the present application and are not repeated here.

[0079] Thus, the preferred features of the heat transfer fluid according to this further aspect of the application have been defined above in relation to the heat transfer fluid in the first aspect of the application, and are therefore not repeated here.

[0080] Further features and advantages of the present application will become more apparent from the following description of some preferred embodiments of the application, given by way of non-limiting example only, with reference to the following figures.

[0081] Experimental part Example 1 - Preparation of neopentyl glycol dipentanoate A multi-necked reaction flask, equipped with an anchor stirrer, a Vigreux column, a condenser and a distillation vessel, was charged with 400 g (3.84 moles) of neopentyl glycol. 980 g (9.6 moles) of pentanoic acid and 3 g of sodium hypophosphite monohydrate were added to the flask. Stirring was started and the system was purged with nitrogen, then the temperature was raised to the boiling of the reaction mixture. The reaction was then continued until the amount of water corresponding to 100% stoichiometric quantity of esterification yield was evaporated. After that, the unreacted pentanoic acid was removed by vacuum distillation until an acid value of less than 5 mg KOH / g was obtained. To the esterification product was added a stoichiometric excess of 4 wt% of sodium hydroxide aqueous solution in the amount required to neutralize the acid value and stirred for 30 minutes; then the organic phase was separated from the aqueous phase, then washed with water, and then dried under vacuum and filtered.

[0082] Example 2 - Preparation of 1,2-propanediol dipentanoate Example 1 was repeated using 292.18 g (3.84 moles) of 1,2-propanediol instead of 400 g of neopentyl glycol and an acid value of 5 mg KOH / g was obtained at the end of the pentanoic acid removal.

[0083] Example 3 - Preparation of 1,3-propanediol dipentanoate Example 1 was repeated using 292.184 g (3.84 moles) of 1,3-propanediol instead of 400 g of neopentyl glycol and an acid value of 5 mg KOH / g was obtained at the end of the pentanoic acid removal.

[0084] Example 4 - Preparation of 2-methyl-1,3-propanediol dipentanoate Example 1 was repeated using 346 g (3.84 moles) of 2-methyl-1,3-propanediol instead of 400 g of neopentyl glycol and an acid value of 5 mg KOH / g was obtained at the end of the pentanoic acid removal.

[0085] Example 5 - Characterization of the diesters The diesters obtained according to Examples 1-4 were characterized in terms of dynamic viscosity at -30°C according to ISO 3219, flash point according to ASTM D7094-04, pour point according to ASTM D5950 and volume resistivity at 25°C according to ASTM D1169. The results are reported in Table 1 below.

[0086] Table 1

[0087] Example 6 - Characterization of diesters The diesters obtained according to Examples 1-4 were characterized in terms of thermal conductivity, thermal diffusivity and specific heat.

[0088] The analysis was performed with the transient hot wire method according to ASTM D7896-19. The testing equipment was Thermtest THW-L2; thermal conductivity and thermal diffusivity were measured at 40°C, while the specific heat was calculated as follows: Cp at 40°C = thermal conductivity at 40°C / (thermal diffusivity at 40°C * density at 40°C).

[0089] The results are reported in Table 2 below.

[0090] Table 2

[0091] Based on the overall characterization of the diesters developed and characterized for indirect cooling according to the above examples, it is clear that these fluids present very promising properties as alternative solutions to PFAS-based fluids. The diesters exhibit remarkable features such as low viscosity at ultra-low temperatures, enabling efficient flow and circulation even in demanding cooling applications. Moreover, their high flash point improves safety measures, reducing the risk of potential fire hazards.

[0092] In addition, the diesters exhibit excellent volume resistivity and dielectric constant, guaranteeing optimal electrical insulation properties. Furthermore, their excellent thermal conductivity and heat transfer capacity enable efficient heat dissipation, contributing to enhanced performance and reliability of electronic systems. Considering these advantageous properties, the diesters represent a very advantageous alternative to PFAS fluids in the field of electronic equipment cooling applications.

[0093] In summary, the diesters offer a more sustainable and environmentally friendly choice compared to PFAS fluids, particularly in terms of greenhouse gas emissions. Their superior properties, combined with reduced environmental impact, make them a very advantageous alternative for cooling electronic equipment.

Claims

1. Use of a heat transfer fluid for cooling an electronic component with an indirect liquid cooling system, said heat transfer fluid comprising at least one diester of at least one C2-C9 aliphatic diol with at least one linear or branched C2-C7 aliphatic monocarboxylic acid.

2. Use according to claim 1, wherein in the heat transfer fluid, the C2-C9 aliphatic diol of the diester is selected from the group consisting of ethylene glycol, 1,2- propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, diethylene glycol, triethylene glycol, dipropylene glycol, neopentyl glycol, 2-methyl-1,3- propanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-butyl-2- ethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol and mixtures thereof.

3. Use according to claim 1 or 2, wherein in the heat transfer fluid, the aliphatic diol of the diester is a C3-C6 aliphatic diol.

4. Use according to claim 3, wherein in the heat transfer fluid, the aliphatic diol of the diester is a C3-C5 aliphatic diol.

5. Use according to any one of claims 1 to 4, wherein in the heat transfer fluid, the monocarboxylic acid of the diester is a C3-C5 aliphatic monocarboxylic acid.

6. Use according to any one of claims 1 to 4, wherein in the heat transfer fluid, the monocarboxylic acid of the diester is a C5-C7 aliphatic monocarboxylic acid.

7. Use according to any one of claims 1 to 6, wherein in the heat transfer fluid, the diester is selected from the group consisting of neopentyl glycol dipentanoate, 1,2- propanediol dipentanoate, 1,3-propanediol dipentanoate, 2-methyl-1,3-propanediol dipentanoate and mixtures thereof.

8. Use according to any one of claims 1 to 7, wherein the indirect liquid cooling system comprises at least one thermally conductive element in thermal coupling with the electronic component, wherein the thermally conductive element is adapted to transfer heat from the electronic component to the heat transfer fluid.

9. Use according to claim 8, wherein the thermally conductive element is selected from the group consisting of a wall, a layer, a heat sink, a cold plate, a heat pipe and a vapor chamber.

10. Use according to any one of claims 1 to 9, wherein the indirect liquid cooling system comprises: a liquid cooling circuit adapted to circulate the heat transfer fluid; a pump adapted to pump the heat transfer fluid throughout the liquid cooling circuit; a heat exchanger adapted to cool the heat transfer fluid; and optionally, a reservoir adapted to contain the heat transfer fluid.

11. Use according to any one of claims 1 to 10, wherein the electronic component is selected from the group consisting of a microprocessor, a semiconductor wafer, a power control semiconductor, an electrochemical cell, a power distribution switchgear, a power transformer, a circuit board, a multi-chip module, a hard disk, a central processing unit, a packaged or unpackaged semiconductor device, a fuel cell, a laser and a semiconductor integrated circuit. ​ 12. Use according to any one of claims 1 to 11, wherein the electronic component is mounted in an electronic device.

13. Use according to claim 12, wherein the electronic device is selected from the group consisting of a computer, a server, a group of servers, a telecommunication center and a data center.

14. A method of cooling an electronic component with an indirect liquid cooling system, wherein the liquid cooling system comprises a heat transfer fluid, the heat transfer fluid comprising at least one diester of at least one C2-C9 aliphatic diol with at least one linear or branched C2-C7 aliphatic monocarboxylic acid.

15. The method of claim 14, wherein the method comprises the steps of: transferring heat from the electronic component to the heat transfer fluid.

16. The method according to claim 14 or 15, wherein the heat transfer fluid is a heat transfer fluid as defined in any one of claims 1 to 7.

17. The method according to any one of claims 14 to 16, wherein the indirect liquid cooling system is an indirect liquid cooling system as defined in any one of claims 8 to 10.

18. The method according to claim 17, wherein the indirect liquid cooling system comprises at least one thermally conductive element in thermal coupling with the electronic component, and wherein in the step of transferring heat, the thermally conductive material is adapted to transfer heat from the electronic component to the heat transfer fluid.

19. The method according to any one of claims 14 to 18, wherein the electronic component is an electronic component as defined in any one of claims 11 to 12.

20. An electronic device comprising: at least one electronic component; and at least one indirect liquid cooling system adapted to cool the electronic component and comprising at least one heat transfer fluid, the heat transfer fluid comprising at least one diester of at least one C2-C9 aliphatic diol with at least one linear or branched C2-C7 aliphatic monocarboxylic acid.

21. The electronic device according to claim 20, wherein the heat transfer fluid is a heat transfer fluid as defined in any one of claims 1 to 7.

22. The electronic device according to claim 20 or 21, wherein the indirect liquid cooling system is an indirect liquid cooling system as defined in any one of claims 8 to 10.

23. The electronic device according to any one of claims 20 to 22, wherein the electronic device is selected from the group consisting of a computer, a server, a group of servers, a telecommunication center and a data center.

24. The electronic device according to any one of claims 20 to 23, wherein the electronic component is an electronic component selected from the group consisting of a microprocessor, a semiconductor wafer, a power control semiconductor, an electrochemical cell, a power distribution switchgear, a power transformer, a circuit board, a multi-chip module, a hard disk, a central processing unit, a packaged or unpackaged semiconductor device, a fuel cell, a laser and a semiconductor integrated circuit.

25. A heat transfer fluid for cooling electronic components comprising at least one diester of a C2-C9 aliphatic diol with at least one linear or branched C2-C7 aliphatic monocarboxylic acid and at least one additive selected from the group consisting of antioxidants, pour point depressant additives, antifoams, anticorrosion agents, viscosity improvers, wear and / or extreme pressure additives, friction modifiers, detergents, dispersants and mixtures thereof.

Images