Method for the liquid immersion cooling of an electronic component

Abstract

The invention relates to a new and improved method for the liquid immersion cooling of an electronic component with improved sustainability and longevity of the ester fluids used therein as heat transfer fluids.

Description

[0001] METHOD FOR THE LIQUID IMMERSION COOLING OF AN ELECTRONIC COMPONENT

[0002] ***

[0003] DESCRIPTION FIELD OF THE INVENTION

[0004] The present application relates to a new and improved method for the liquid immersion cooling of an electronic component with improved sustainability and longevity of the ester fluids used therein as heat transfer fluids.

[0005] BACKGROUND

[0006] Nowadays, heat dissipation is a relevant topic in the design and operation of electronic devices, especially for devices which comprise densely packed electronic circuit components and in particular semi-conductor type circuit components such as integrated circuit components. Heat dissipation is a serious issue for example in modern server farms as well as in telecommunication centres and datacentres, where the large number of hard disks, microprocessors or central processing units (CPU) and the continuous increase of their processing and storage power renders heat dissipation a crucial factor for the prevention of overheating of such electronic components, which may lead to failure and irreparable damages to them.

[0007] In the field of design and operation of electronic devices, it is therefore strongly felt the need of identifying and developing new and improved cooling systems.

[0008] Today, there are different cooling systems which employ various techniques to transfer heat away from electronic components for maintaining their suitable operating temperature; they may be classified based on the type of heat-transfer fluid and on the basis of whether the heat-transfer occurs with a direct or indirect contact of the heat-transfer with the electronic component.

[0009] In this technical field single-phase immersion cooling is becoming increasingly popular as a cutting-edge method for handling the rising heat levels produced by high-performance data center equipment. This technique involves submerging electronic devices, such as servers, in a dielectric fluid that remains in its liquid state, ensuring direct contact with such heatgenerating components. This direct interaction allows for highly efficient heat transfer, a challenge for traditional air and liquid cooling systems, particularly with today’s densely packed systems. As data centers expand and their power requirements grow, scalable and effective cooling solutions like single-phase immersion cooling are becoming essential. The heat-transfer fluid used in single-phase immersion cooling systems plays therefore a crucial role for heat dissipation. Today, known fluids for single-phase immersion cooling systems are typically synthetic specialized fluids, among which synthetic esters, particularly polyol esters, are predominantly notable and promising.

[0010] Indeed, their dielectric properties effectively prevent electrical conductivity, ensuring the system remains safe and operational. Beyond this, ester-based fluids have a high flash point, reducing fire risk, a crucial factor for densely packed systems like data centers prioritizing safety, and a high thermal stability. Additionally, their low volatility minimizes evaporation, maintaining cooling performance over extended periods and reducing the need for frequent refills. This not only simplifies maintenance but also limits exposure to potentially harmful vapours.

[0011] On top of that, thermal conductivity is another notable property of ester-based fluids, allowing such fluids to transfer heat efficiently away from the submerged components, while high heat capacity means ester-based fluids can absorb a large amount of heat before their temperature rises significantly. These properties are vital for maintaining consistent and effective cooling in high-performance, heat-generating environments.

[0012] SUMMARY OF INVENTION

[0013] The Applicant noted, however, that ester-based fluids in immersion cooling systems are exposed to moisture from the environment and in the ever-changing humidity levels of such systems, this can lead to hydrolysis, a chemical reaction where water breaks down the ester bonds in the fluid, especially considering that the ester-based fluids undergo also to continuous thermal cycles of heating / cooling when being circulated in the system.

[0014] The Applicant also noted that such combination of exposition to moisture and continuous thermal cycles of heating / cooling may limit the longevity of the ester-based fluids by affecting their properties.

[0015] The Applicant therefore felt the need to improve the sustainability and longevity of immersion cooling systems using ester-based fluids as heat transfer fluids.

[0016] An object of the present invention is therefore to provide a new and improved method for the liquid immersion cooling of an electronic component with improved sustainability and longevity of the ester-based fluids used therein as heat transfer fluids. The Applicant surprisingly found out that an efficient on-line regeneration step of simple implementation may be used for such purpose.

[0017] Particularly, the present invention relates, in a first aspect, to a method for the liquid immersion cooling of an electronic component, comprising the steps of:

[0018] a) operating an electronic component while immersed in a liquid heat transfer fluid comprising an ester, thereby cooling the electronic component and obtaining an heated liquid ester fluid;

[0019] b) transferring the heated liquid ester fluid of step a) to a regeneration unit and flowing an gas into said heated liquid ester fluid in said regeneration unit; and

[0020] c) using the liquid ester fluid obtained from step b) as liquid heat transfer fluid in step a). Surprisingly, the Applicant has indeed found out that by subjecting the heated ester fluid to an on-line regeneration step (step b) with a flow of a gas into it, it is possible to remove moisture and other volatiles components that may lead to hydrolysis of the ester and progressively worsen its performances as heat transfer fluid in immersion cooling systems. Advantageously, in the method according to the invention such regeneration step is performed on-line, that is without removing the fluid from immersion cooling systems and thus also without need of forced interruptions in the operation of the electronic components to refill such systems with fresh heat transfer fluids; in this way the efficiency and costeffectiveness and sustainability of the immersion cooling system is improved. In addition, the possibility of subjecting the heat transfer fluid to such an on-line regeneration step safeguards its properties and therefore ensures stability in the heat removal from the electronic components during their operations, thus minimizing the risks of their overheating that may lead to failure and irreparable damages to them.

[0021] In this way, an improved and more sustainable immersion cooling method for electronic components is obtained.

[0022] In a further aspect, the present invention relates also to an immersion cooling apparatus for an electronic component, including:

[0023] - an immersion cooling tank, apt to contain at least one electronic component submerged into a liquid ester fluid comprising an ester;

[0024] - a regeneration unit, apt to contain an heated liquid ester fluid and to flow a gas into said heated liquid ester fluid; - an heat exchanger, apt to cool an heated liquid ester fluid; and

[0025] - a circulation loop system, apt to circulate a liquid ester fluid within the immersion cooling apparatus.

[0026] The advantages of the immersion cooling apparatus according to this further aspect of the present invention has been already disclosed in relation to the method according to the first aspect of the present invention and are not herewith repeated.

[0027] DETAILED DESCRIPTION OF INVENTION

[0028] The present invention relates, in a first aspect, to a method for the liquid immersion cooling of an electronic component, comprising the steps of:

[0029] a) operating an electronic component while immersed in a liquid heat transfer fluid comprising an ester, thereby cooling the electronic component and obtaining an heated liquid ester fluid;

[0030] b) transferring the heated liquid ester fluid of step a) to a regeneration unit and flowing a gas into said heated liquid ester fluid in said regeneration unit; and c) using the liquid ester fluid obtained from step b) as liquid heat transfer fluid in step a).

[0031] Surprisingly, the Applicant has indeed found out that by subjecting the heated ester fluid to an on-line regeneration step (step b) with a flow of a gas into it, it is possible to remove moisture and other volatiles components that may lead to hydrolysis of the ester and progressively worsen its performances as heat transfer fluid in immersion cooling systems. Advantageously, said on-line regeneration step is performed on-line, without removing the fluid from immersion cooling systems and thus also without need of forced interruptions in the operation of the electronic components to refill such systems with fresh heat transfer fluids, thus improving the efficiency and cost-effectiveness of the system and its sustainability. In addition, the possibility of subjecting the heat transfer fluid to such on-line regeneration step safeguards its properties and therefore ensures stability in the heat removal from the electronic components during their operations, thus minimizing the risks of their overheating that may lead to failure and irreparable damages to them.

[0032] In this way, an improved and more sustainable immersion cooling of electronic components is obtained. Within the framework of the present description and in the subsequent claims, except where otherwise indicated, all the numerical entities expressing amounts, parameters, percentages, and so forth, are to be understood as being preceded in all instances by the term "about". As used herein, the term “about” will be understood by persons of ordinary skill in the art and will vary to some extent on the context in which it is used. As used herein when referring to a measurable value such as an amount, a temporal duration, and the like, the term “about” is meant to encompass variations 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] Also, all ranges of numerical entities include all the possible combinations of the maximum and minimum values and include all the possible intermediate ranges, in addition to those specifically indicated herein below.

[0034] Unless defined otherwise, 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 invention 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] The present invention may present in one or more of the above aspects one or more of the characteristics disclosed hereinafter.

[0037] According to the present invention, in step a) the electronic component is operated while being immersed in the liquid heat transfer fluid comprising an ester. In this step, therefore, the electronic component thereby cooling the and obtaining an heated liquid ester fluid. Step a) is herein not particularly limited and may be any type of direct liquid cooling step known to the skilled person in the relevant technical field for immersion cooling an electronic component.

[0038] In said step a), any type of immersion cooling tank apt to contain at least one electronic component submerged into a liquid fluid comprising an ester is advantageously used.

[0039] Preferably, said electronic component is selected from the group consisting of: a microprocessor, a circuit board, a multi-chip module, an hard disk, a central processing unit, a packaged or unpackaged semiconductor device, and a semiconductor integrated circuit. In step a) of the method according to the invention, a liquid heat transfer fluid comprising an ester is used to cool the electronic component.

[0040] Preferably, said ester is an ester of at least one monocarboxylic acid and / or dicarboxylic acid with at least one monohydric alcohol and / or polyhydric alcohol, more preferably selected from the group consisting of: a monoester, a polyol ester, a complex ester.

[0041] Exemplary monocarboxylic acids suitable as building blocks of esters according to the present invention are: propanoic acid, butyric acid, isobutyric acid, 2-methylbutyric acid, 3-methylbutyric acid, valeric acid, hexanoic acid, heptanoic acid, 2-ethylhexanoic acid, 3-propylheptanoic acid, n-octanoic acid, n-nonanoic acid, 3,5,5-trimethylhexanoic acid, n-decanoic acid, isodecanoic acid (8-methyl-1-nonanoic acid), isoundecanoic acid (9-methyl-1 -decanoic acid), lauric acid, 2,4 - diethyl octanoic acid, and mixtures thereof.

[0042] Exemplary dicarboxylic acids suitable as building blocks of esters according to the present invention are: oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, dodecandioic acid, hexadecanedioic acid, and mixtures thereof.

[0043] Exemplary monohydric alcohols suitable as building blocks of esters according to the present invention are: 1 -propanol, 2-propanol, 1 -butanol, 2-butanol, isobutanol, tert-butanol, 1 -pentanol, 2-pentanol, 3-pentanol, 1 -hexanol, 2-hexanol, 1 -heptanol, 2-heptanol, 1- octanol, 2-ethylhexanol, isononanol, 3,5,5-trimethylhexanol, 2-propylheptanol, 1 -decanol, isodecanol (8-methyl-1 -nonanol), isoundecanol (9-methyl-1 -decanol), lauryl alcohol (dodecanol), 2,4 - diethyl octanol, and mixtures thereof.

[0044] Exemplary polyhydric alcohols suitable as building blocks of esters according to the present invention are: neopentyl glycol, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, glycerol, ethylene glycol, 1 ,2- propanediol, 1,3- propanediol, 1 ,4-butanediol, 1 ,3-butanediol, di-ethylene glycol, tri-ethylene glycol, di¬ propylene glycol, 2-methyl-1 ,3-propanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, 3-metyl-1 ,5- pentanediol, 2-butyl-2-ethyl-1 ,3-propanediol, and 2,2,4-trimethyl-1 ,3-pentanediol, and mixtures thereof.

[0045] In an embodiment of the present invention, said ester in the liquid heat transfer fluid is a monoester of at least one C6-C12 aliphatic monohydric alcohol with at least one linear or branched C2-C7 aliphatic monocarboxylic acid. In a further preferred embodiment of the present invention, said ester in the liquid heat transfer fluid is a polyol ester of at least one linear or branched C2-C15 aliphatic polyhydric alcohol (also referred to as “polyol”) with at least one linear or branched C2-C12 aliphatic monocarboxylic acid.

[0046] In a still further preferred embodiment, the ester of the liquid heat transfer fluid according to the invention is a polyol ester of pentaerythritol esterified with at least one linear or branched C2-C7 aliphatic monocarboxylic acid, more preferably valeric acid. In an even more preferred embodiment the ester is pentaerythritol tetravalerate.

[0047] The liquid heat transfer fluid according to the invention may consist or essentially consist of an ester, due to the extremely good properties of such compounds when it comes to heat exchange, dielectric properties, thermal and rheological properties and to the effectiveness of the regeneration step b) according to the invention.

[0048] Notwithstanding the above, in addition to the esters the liquid heat transfer fluid according to the invention may also advantageously contain one or more other components, among which for example a mineral oil, a polyether such as a polyalkylene glycol, a polyolefin, an additive.

[0049] Suitable additives liquid heat transfer fluid according to the invention are for example an antioxidant, a pour-point-depressant additive, an antifoam agent, an anticorrosion agent, a viscosity modifier, a wear-resistance and / or extreme-pressure additive, a friction modifier, a detergent, a dispersant, or any mixtures thereof.

[0050] In step b) the heated liquid ester fluid obtained in step a) is transferred to a regeneration unit for advantageously remove moisture and other volatiles components that may lead to hydrolysis of the ester and progressively worsen its performances. Such removal is obtained by flowing a gas into said heated liquid ester fluid in said regeneration unit.

[0051] In said step b) a regeneration unit apt to contain an heated liquid ester fluid and to flow a gas into said heated liquid ester fluid is advantageously used. By way of example, such a regeneration unit may be a tank with a gas distribution system to let the gas flow into a liquid. In step b), a gas is made to flow into the heated liquid ester fluid obtained in step a). Preferably, the flowing of said gas is obtained by infusing the gas into the heated liquid ester. Preferably, in said step b) said heated liquid ester fluid has a temperature comprised in the range from 20 to 90 °C, more preferably from 30 to 70 °C, even more preferably from 40 to 60 °C, optimally about 50 °C.

[0052] Preferably, said gas is selected from the group consisting of: air, nitrogen, helium, carbon dioxide, argon, or any combination thereof. In a preferred embodiment, the gas is air.

[0053] Preferably, in said step b) said gas is made to flow into said heated liquid ester fluid in the form of bubbles. This advantageously increases the surface contact of the gas with the ester fluid thus improving the removal of moisture and other volatiles.

[0054] Preferably, in said step b) said gas is made to flow into said heated liquid ester fluid at a flow rate comprised in the range from 0.1 to 10 ml / second, more preferably from 0.5 to 4 ml / second, optimally about 1 ml / second, per every liter of heated liquid ester fluid.

[0055] According to the method according to the invention, the liquid ester fluid is regenerated as a result of step b). The properties of such liquid ester fluid are therefore advantageously suitable for its subsequent use as liquid heat transfer fluid in immersion cooling.

[0056] Preferably, in step c) the liquid ester fluid obtained from step b) is cooled before using it as heat transfer fluid in step a); more preferably in step c) the liquid ester fluid is cooled by feeding it to a heat exchanger.

[0057] Any type of heat exchanger apt to cool the liquid ester fluid obtained from step b) and known to the skilled person in the relevant technical field for immersion cooling an electronic component may be advantageously used in step c) of the method according to the invention. In a further aspect, the present invention relates also to an immersion cooling apparatus for an electronic component, including:

[0058] - an immersion cooling tank, apt to contain at least one electronic component submerged into a liquid fluid comprising an ester;

[0059] - a regeneration unit, apt to contain an heated liquid ester fluid and to flow a gas into said heated liquid ester fluid;

[0060] - an heat exchanger, apt to cool an heated liquid ester fluid; and

[0061] - a circulation loop system, apt to circulate a liquid ester fluid within the immersion cooling apparatus. The advantages of the immersion cooling apparatus according to this further aspect of the present invention has been already disclosed in relation to the method according to the first aspect of the present invention and are not herewith repeated.

[0062] In the immersion cooling apparatus according to the invention, any type of immersion cooling tank apt to contain at least one electronic component submerged into a liquid fluid comprising an ester any type of heat exchanger apt to cool an heated liquid ester fluid known to the skilled person in the relevant technical field for immersion cooling an electronic component may be advantageously used.

[0063] In the immersion cooling apparatus according to the invention, the regeneration unit is apt to contain an heated liquid ester fluid and to flow an gas into said heated liquid ester fluid is advantageously used. By way of example, such a regeneration unit may be a tank with a gas distribution system to let the gas flow into a liquid.

[0064] The immersion cooling apparatus according to the invention includes a circulation loop system, apt to circulate a liquid ester fluid within the immersion cooling apparatus.

[0065] Preferably, said circulation loop system includes:

[0066] - a first stretch apt to circulate a liquid fluid comprising an ester from said immersion cooling tank to said regeneration unit;

[0067] - a second stretch apt to circulate a liquid fluid comprising an ester from said regeneration unit to said heat exchanger; and

[0068] - a third stretch apt to circulate a liquid fluid comprising an ester from said heat exchanger to said immersion cooling tank.

[0069] The apparatus so defined is therefore advantageously suitable to perform the immersion cooling method according to the first aspect of the present invention.

[0070] In this way, an improved and more sustainable immersion cooling apparatus for electronic components is obtained in the present invention.

[0071] Further features and advantages of the invention will appear more clearly from the following description of some preferred embodiments thereof, made hereinafter by way of the following non-limiting examples.

[0072] EXPERIMENTAL PART

[0073] Example 1 As a proof of concept of the effectiveness of step b) of the method according to the invention, in a thermal bath set at 50 °C, 750 grams of a polyol ester fluid (pentaerythritol tetravalerate, water content 0.07 weight %, acid number 0.017 mg KOH / g) were introduced. The thermal bath was provided with a submerged infusion system with infusion nozzles at the bottom of the bath; ambient air at 50 °C at a flow rate of 1 ml / sec was infused into the polyol ester fluid, letting said air to flow into it.

[0074] The properties of the polyol ester fluid over time were measured and reported in Table 1. In order to simulate a long residence time into a regeneration unit and a high thermal stress condition for the fluid, the following properties of the polyol ester fluid were tested for 4 weeks:

[0075] - Acid number: The acid number was measured according to ASTM D974 to assess the degree of hydrolysis by determining the amount of acid generated. An increase in acid value indicates degradation of the ester bonds, which can impact the fluid's stability;

[0076] - Water Content: The water content was determined using the Karl Fischer Coulometric (KFC) method, as per ASTM E 1064-92;

[0077] - Tan 5: Tested according to IEC 60247 at 90°C, this measure of the dissipation factor reveals the amount of energy loss in the fluid when exposed to an alternating electric field. Lower tan 5 values correspond to better dielectric properties and less energy loss;

[0078] - Volume Resistivity: Measured according to IEC 60247 at 90°C and 50 Hz, this test evaluates the electrical resistance of the fluid. High resistivity indicates the fluid’s effectiveness as an insulator.

[0079] TABLE 1

[0080]

[0081]

[0082] From the data above, it was found out that the treatment by infusing air into the polyol ester fluid kept and even slightly improved its properties, showing the effectiveness of the method according to the invention to improve the sustainability and longevity of immersion cooling systems using ester-based fluids as heat transfer fluids.

Claims

CLAIMS1. A method for the liquid immersion cooling of an electronic component, comprising the steps of:a) operating an electronic component while immersed in a liquid heat transfer fluid comprising an ester, thereby cooling the electronic component and obtaining an heated liquid ester fluid;b) transferring the heated liquid ester fluid of step a) to a regeneration unit and flowing a gas into said heated liquid ester fluid in said regeneration unit; c) using the liquid ester fluid obtained from step b) as liquid heat transfer fluid in step a).

2. The method according to claim 1 , wherein said electronic component is selected from the group consisting of: a microprocessor, a circuit board, a multi-chip module, an hard disk, a central processing unit, a packaged or unpackaged semiconductor device, and a semiconductor integrated circuit.

3. The method according to claim 1 or 2, wherein said ester is an ester of at least one monocarboxylic acid and / or dicarboxylic acid with at least one monohydric alcohol and / or polyhydric alcohol.

4. The method according to claim 3, wherein said ester is selected from the group consisting of: a monoester, a polyol ester, a complex ester.

5. The method according to any of claims 1 -4, wherein said ester is a monoester of at least one C6-C12 aliphatic monohydric alcohol with at least one linear or branched C2-C7 aliphatic monocarboxylic acid.

6. The method according to any of claims 1 -4, wherein said ester is a polyol ester of at least one linear or branched C2-C15 aliphatic polyhydric alcohol with at least one linear or branched C2-C12 aliphatic monocarboxylic.

7. The method according to any of claims 1 -6, wherein in step b) said flowing of said gas is obtained by infusing the gas into the heated liquid ester.

8. The method according to any of claims 1 -7, wherein in said step b) said heated liquid ester fluid has a temperature of comprised in the range from 20 to 90 °C.

9. The method according to any of claims 1 -8, wherein in said step b) said gas is selected from the group of: air, nitrogen, helium, carbon dioxide, argon, or any combination thereof.

10. The method according to any of claims 1-9, wherein in said step b) said gas is made to flow into said heated liquid ester fluid at a flow rate comprised in the range from 0.1 to 10 ml / second, per every liter of heated liquid ester fluid.

11. An immersion cooling apparatus for an electronic component, including:- an immersion cooling tank, apt to contain at least one electronic component submerged into a liquid fluid comprising an ester,- a regeneration unit, apt to contain an heated liquid ester fluid and to flow a gas into said heated liquid ester fluid,- an heat exchanger, apt to cool an heated liquid ester fluid, and- a circulation loop system, apt to circulate a liquid ester fluid within the immersion cooling apparatus.

12. The immersion cooling apparatus according to claim 11 , wherein said circulation loop system includes:- a first stretch apt to circulate a liquid fluid comprising an ester from said immersion cooling tank to said regeneration unit;- a second stretch apt to circulate a liquid fluid comprising an ester from said regeneration unit to said heat exchanger; and- a third stretch apt to circulate a liquid fluid comprising an ester from said heat exchanger to said immersion cooling tank.

13. The immersion cooling apparatus according to claim 11 or 12, wherein said regeneration unit is apt to perform step b) of the method according to any of claims 1 - 10.

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