WO2023031768A1

WO2023031768A1 - Immersion cooling system including hydrolysis-resistant fluoroketone

Info

Publication number: WO2023031768A1
Application number: PCT/IB2022/058078
Authority: WO
Inventors: Forrest A. COUGHLIN; Tyler S. MATTHEWS
Original assignee: 3M Innovative Properties Company
Priority date: 2021-08-30
Filing date: 2022-08-29
Publication date: 2023-03-09

Abstract

Immersion cooling systems are described. In particular, immersion cooling systems including hydrolysis-resistant fluoroketones are described. Certain hydrolysis-resistant fluoroketones include a fully fluorinated morpholine moiety. Despite being hydrolysis-resistant these fluoroketones may still exhibit low global warming potential.

Description

IMMERSION COOLING SYSTEM INCLUDING HYDROLYSIS-RESISTANT FLUOROKETONE

Background

Immersion cooling systems may provide highly efficient heat transfer from electronic components through direct conduction. Fluoroketones are fluorinated chemicals with a ketone functional group. Hydrolysis is the reaction of water with chemicals that can lead to the formation of new breakdown or degradation products.

Summary

In one aspect, the present description relates to an immersion cooling system. The immersion cooling system includes a container, a fluoroketone disposed within the container, and at least one electrical component disposed within the container and in contact with the fluoroketone. The fluoroketone has a boiling point of at least 100°C but no higher than 200°C and is of the form

where CnF2n is linear or branched, CmF2m is linear or branched, and n and m are each integers, n being between 1 and 3 and m being between 1 and 5. The container is configured such that the at least one electrical component is accessible to be changed or replaced, and accessing the at least one electrical component exposes the fluoroketone to air.

In another aspect, the present description relates to a method of configuring an immersion cooling system. The method includes providing a container, disposing at least one electrical component within the container such that the at least one electrical component is accessible to be changed or replaced; and at least partially filling the container with a fluoroketone, where the fluoroketone is disposed such that the fluoroketone is in contact with the at least one electrical component, and that accessing the at least one electrical component exposes the fluoroketone to air. The fluoroketone has a boiling point of at least 100°C but no higher than 200°C and is of the form

where C_nF_2n is linear or branched, C_mF_2m is linear or branched, and n and m are each integers, n being between 1 and 3 and m being between 1 and 5.

Brief Description of the Drawings

FIG. 1 is a schematic side elevation cross section of an immersion cooling system.

Detailed Description

As used herein, "fluoro-" (for example, in reference to a group or moiety, such as in the case of "fluoroalkylene" or "fluoroalkyl" or "fluorocarbon") or "fluorinated" means (i) partially fluorinated such that there is at least one carbon-bonded hydrogen atom, or (ii) perfluorinated.

As used herein, "perfluoro-" (for example, in reference to a group or moiety, such as in the case of "perfluoroalkylene" or "perfluoroalkyl" or "perfluorocarbon") or "perfluorinated" means completely fluorinated such that, except as may be otherwise indicated, any carbon- bonded hydrogens are replaced by fluorine atoms.

As used herein, “fluid” refers to the liquid phase and/or the gaseous phase.

Fluorinated materials, including fluorinated fluids (fluid including both liquid and gas phases), are useful in numerous applications. This is at least in part to its electric nonconductivity at normal operating temperatures and environments, and its ability to prevent electrical short circuits (shorts). Electrical non-conductivity may be quantified by its breakdown strength at a given voltage, for a standard gap. For example, electrically non-conductive may mean greater than a 35kV breakdown strength at a 2.5 mm gap, according to ASTM D877 (1987). In some embodiments, electrically non-conductive may mean greater than a 25kV breakdown strength at a 2.5 mm gap, according to ASTM D877 (1987). In some embodiments, electrically non-conductive may mean having very high electrical resistivity, such as greater than 10^A7 Ω cm.

The insulating properties of such fluorinated materials may make them particularly useful for insulating gasses (such as in electrical grid equipment) to prevent arcing electrical shorts, in fire-suppression applications to flood (and thereby remove heat or cut off oxygen from) electronic equipment without shorting it, and in immersion heat-transfer applications to efficiently transfer heat from electronic equipment without providing an electrically conductive medium to potentially allow short circuits to damage it.

Fluorinated materials having low global warming potential (GWP) are of particular interest for users of immersion cooling systems. Fluoroketones are an example of a class of materials that have low GWP and may be particularly suitable for immersion cooling. However, the same functional groups that enable the quick atmospheric breakdown (and thereby a low GWP) may also react with other elements within the immersion cooling system, including electronic components immersed therein, forming undesirable byproducts. For example, fluoroketones may undergo hydrolysis in the presence of water to form a highly corrosive acid (perfluoropropionic acid, or PFPA), which may circulate through the system and corrode or etch materials in contact with the circulating fluid. Along with PFPA, HFC-227ea (1,1, 1,2, 3, 3, 3 heptafluoropropane) is produced, which is a gas at room temperature. Because the gas may leave the system, such a process may be irreversible.

Besides being corrosive, certain contaminants and degradation and reaction products in fluorinated fluid systems may act as a co-solvent for other potentially harmful contaminants, such as solder flux residue, plasticizers, metal salts, and (other) degradation and reaction products. Moreover, these contaminants may compromise other properties of the fluid, including dielectric properties. However, certain fluoroketones, particularly fluoroketones that include a fully fluorinated morpholine moiety, demonstrate resistance to hydrolysis reactions that form degradation or breakdown products, while still having low GWP.

FIG. 1 is a schematic side elevation cross section of an exemplary immersion cooling system. System 100 includes container 110 including access door 112. Disposed within container 110 is a fluorinated fluid 120 and at least one electrical component 130 in contact with the fluorinated fluid. Optional fluid conditioning loop 140 may be present to condition the fluorinated fluid 120 within container 110.

Container 110 may be any suitable space or volume, formed from any suitable material or materials, which may be fully or partially filled with fluorinated fluid 120. For example, container 110 may be a tank in which servers, computers, and/or other electronics are fully or partially immersed in a liquid fluorinated fluid, for heat transfer applications. In some embodiments, container 110 may be a switchgear or other sensitive electrical device wherein a gaseous fluid is present in a sufficient quantity to prevent the arcing between high voltage components. In some embodiments, container 110 may be filled with both liquid and gaseous fluid. In some embodiments, container 110 may not always include a fluorinated fluid, but it may be filled in response to a certain event (e.g., fire suppression in response to a detected fire or fire risk). Container 110 may contain any suitable additional components to manage the pressure or ambient environment within the container. Container 110 may also contain (not illustrated) components selected for the particular application (e.g., server docks, electrical and network cables, circuit breakers, etc.), or other systems. For example, a heat exchanger, compressor, or other thermal management device may be present. In some embodiments, at least a portion of container may be at least partially transparent to permit the monitoring and viewing of the operation and health of components located therein.

Access door 112 may be any suitable component for accessing components disposed within container 120. Access door may be a physical entry point (such as a door, flap, hinged lid, or other moveable component) or any other interface whereby one can safely access and repair or install/remove components within container 110 (with or without direct human interaction or intervention: for example, a fully or partially automated robotic arm system). In some embodiments, using access door 112 in at least some fashion exposes the inside of container 110 to air 150 (or any other environmental atmosphere with a non-negligible humidity). Access door may include a window or other partially transparent surface for observing the internal environment of container 110.

Fluorinated fluid 120 may be any suitable fluorinated fluid or blend of fluids. In some embodiments, the fluorinated fluid 120 may be or include one or more fluoroketones. In some embodiments, the fluoroketones may be perfluorinated. In some embodiments, the fluoroketones may include from 5 to 12 carbon atoms or from 5 to 8 carbon atoms. In some embodiments, the fluoroketones may include a partially or fully fluorinated morpholine moiety. In some embodiments, fluoroketones may be present in the fluid in an amount of a least 80 wt. %, at least 90 wt. %, or at least 95 wt. %, based on the total weight of the fluid.

In some embodiments, in addition to or in place of the fluoroketones or perfluorinated sulfones, the fluid may also include (individually or in any combination): ethers, alkanes, perfluoroalkenes, alkenes, hydrofluoroalkenes, aromatic fluoroalkenyl esters, haloalkenes, perfluorocarbons, perfluorinated tertiary amines (saturated or mono-unsaturated), perfluoroethers (saturated or mono-unsaturated), cycloalkanes, esters, oxiranes, aromatics, siloxanes, hydrochlorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, hydrofluoroolefins, hydrochloroolefins, hydrochlorofluoroolefins, or hydrofluoroethers. Such additional components can be chosen to modify or enhance the properties of a fluid for a particular use.

In some embodiments, the fluids of the present disclosure may be hydrophobic, relatively chemically unreactive, and thermally stable. The fluids may have a low environmental impact. In this regard, the fluids of the present disclosure may have a zero, or near zero, ozone depletion potential (ODP) and a global warming potential (GWP, 100-year ITH) of less than 800, 500, 300, 200, 100 or less than 10. In some embodiments, the fluids of the present disclosure may have certain useful boiling points, for example, a boiling point between 30°C and 75°C, a boiling point between 130°C and 150°C, a boiling point between 100°C and 200°C, a boiling point between 130°C and 200°C, or a boiling point between 150°C and 200°C. In some embodiments, the fluids of the present disclosure may have a low dielectric constant, such as less than 4, or less than 2 at 1 kHz. In some embodiments, the fluids of the present disclosure may have useful pour points, for example, a pour point of less than -40°C, a pour point of less than -50°C, or a pour point of less than -60°C.

At least one of electrical component 130 is disposed in immersion cooling system 100. Electrical component 130 may be any suitable component. In some embodiments, electrical component may be an electrical component that generates a lot of heat, and/or may be limited in performance (including, for example, throttled or limited by a controller for safety or longevity reasons) when reaching or approaching certain thermal thresholds. Examples of such components include single and multi-core processors, sensors, general and specialized purpose integrated circuits, graphics processing units, hard disk or solid state memory storage devices, displays, random access memory, electronic transformers, inverters, or rectifiers, and networking component (LAN or wireless transceiver). Any of electrical component 130 may include heat sinks or heat piping to transfer heat to a location, typically away from the more sensitive components. As described elsewhere, cabling and other connective wiring for power supply, or data transfer may also be included, although it is not shown in detail in FIG. 1 for ease of illustration.

At least one of electrical component 130 may be multiple electrical components, including multiples of certain components for certain applications. As an example, a specialized cloud-based graphics rendering operation may utilize multiple graphics processing units, and a specialized server may include multiple processors and storage disks.

Fluid conditioning loop 140 is optionally present. Fluid conditioning loop 140 may include any system present to improve or maintain the condition of fluid 120. Fluid conditioning loop 140 may include filtration media and filtration housing. Depending on the application, the fluid conditioning loop may incorporate or utilize different flow schemes within, in order to place the fluid to be conditioned in contact with the appropriate media. Suitable housings and general filtration regimes will depend on the particular requirements of the applications (e g., liquid versus gaseous filtration, acceptable pressure drop, nature and quantity of the expected contaminants, etc.). Any filter housing may be specifically configured in order to allow for the quick and easy change of any filtration/sorbent media. Note, that for the purposes of this description, filtration is not limited to the separation of solid phases (not dissolved) and liquid phases. Filtration as used herein includes separation of the bulk fluid from dissolved impurities, degradation or reaction products, or other undesired contaminants, whether or not dissolved or of the same phase.

The fluid path through fluid conditioning loop 140 may be any suitable conduit for appropriate fluids to travel within and through the fluid conditioning system. The fluid path may vary depending on the matter phases of the fluid. For example, a fluid path through fluid conditioning loop may be formed or created by piping or tubing. In some embodiments, a fluid path may be formed by ducting. In some embodiments, a fluid path through the fluid conditioning loop may be less rigidly constrained: for example, the fluid path through the fluid conditioning loop may be dictated by currents or other influences of force or pressure. In some embodiments, the fluid path through the fluid conditioning loop may emerge from an expansion and compression cycle, a phase change cycle, or from a heating and cooling cycle.

Fluid conditioning loop 140 may also include a pump. The pump may be any suitable device or mechanism to circulate the fluid through the fluid conditioning system. The pump may be a conventional fan or turbine to mechanically move fluid within the fluid conditioning loop. The pump may be of any suitable style and its performance and characteristics may be selected based on the particular application and environment. The pump may also be powered by any suitable means. In some embodiments, the pump may not always be on, and may be intermittently triggered by a sensor or timer detecting a certain property threshold or the passing of an appropriate time interval.

Examples

Test Method

Hydrolytic Stability Test

A hydrolytic stability test was performed by boiling/refluxing 1,1,4,4,4-pentafluoro-l- (2,2,3,3,5,5,6,6-octafluoromorpholin-4-yl)-3-(trifluoromethyl)butan-2-one (PFOFMTFMB) in a 2 neck round bottom flask. The flask was equipped with a water condenser and a humidified nitrogen stream. The humidified nitrogen stream was bubbled into the liquid phase, i.e., the PFOFMTFMB which filled approximately 50% of the flask volume. One, 4 cm x 1cm, aluminum-coated polyethylene terephthalate (PET) coupon was added to the flask and submersed in the boiling liquid. The coupon was made by depositing a thin film (50 nm) of aluminum onto the surface of a conventional PET film via e-beam evaporation. In the presence of corrosive byproducts, produced by the decomposition of PFOFMTFMB, the aluminum film was expected to dissolve, producing a transparent film which served as a simple detection device for decomposition products. The nitrogen stream was humidified by passing the gas through water and then into the boiling liquid. This test was designed to emulate a datacenter immersion cooling environment wherein low concentrations of water (lower than the solubility limit) are steadily extracted from computing and related hardware components. Surprisingly, there was no visual sign of degradation of the aluminum coating of the coupon after 12 weeks of continuous exposure to the boiling PFOFMTFMB. This observation was confirmed by conventional F¹⁹ NMR analysis which did not detect hydrolysis products expected from the decomposition of PFOFMTFMB (Table 1).

Synthesis of 2, 2, 3, 3, 5, 5, 6, 6-octafluoromorpholine-4-carbonyl fluoride

2,2,3,3,5,5,6,6-octafluoromorpholine-4-carbonyl fluoride, may be synthesized, for example, following a procedure similar to that disclosed in JP2000087276A. In that description, 450 g of anhydrous hydrofluoric acid was introduced, and this was purified by preliminary electrolysis, and 40.9 g of N- (2 -hydroxyethyl) morpholine was dissolved in anhydrous hydrogen fluoride. This electrolytic solution was subjected to 228 Ahr electrolysis at 5.7 to 6.1 V. The electrolysis voltage finally reached 6.8V. The generated gas was collected in a trap cooled to -78 ° C. in a dry ice-ethanol bath after removing accompanying hydrogen fluoride through a sodium fluoride tube. After the electrolysis was completed, the drain cock at the bottom of the electrolytic cell was opened, and the 2,2,3,3,5,5,6,6-octafluoromorpholine-4-carbonyl fluoride was extracted. Further, some 2,2,3,3,5,5,6,6-octafluoromorpholine-4-carbonyl fluoride was collected in the cooling trap.

Synthesis of 1, 1, 4, 4, 4-pentafluoro-l-(2, 2, 3, 3, 5, 5, 6, 6-octafluoromorpholin-4-yl)-3-

(trifluoromethyl) butan-2-one (PFOFMTFMB) 2,2,3,3,5,5,6,6-octafluoromorpholine-4-carbonyl fluoride was purified by fractionation to

98% purity. To a 600 ml parr reactor was charged 225 grams of 2, 2, 3, 3, 5, 5,6,6- octafluoromorpholine-4-carbonyl fluoride, 200 grams di ethylene glycol dimethyl ether, and 12 grams potassium fluoride. The reactor was sealed and placed under vacuum. The temperature of the reactor was brought up to 70°C and charged with 124 grams of hexafluoropropylene from and inverted cylinder over a 1-hour time period. The reaction was stirred for 12 hours, cooled, vented and the contents transferred to a separatory funnel. The bottom phase was collected and distilled to yield 242 grams of PFOFMTFMB (approx.73% yield). Table 1. ¹⁹F-NMR Analysis of PFOFMTFMB after Hydrolytic Stability Testing.

1) No acidic protons were detected by ¹H-NMR analysis.

2) PFOFMTFMB with no boiling/no refluxing/no coupon in liquid.

Claims

9 What is claimed is:

1. An immersion cooling system, comprising: a container; a fluoroketone disposed within the container; and at least one electrical component disposed within the container and in contact with the fluoroketone; wherein the fluoroketone has a boiling point of at least 100°C but no higher than

200°C and is of the form

, wherein C_nF_2n is linear or branched, C_mF_2m is linear or branched, and n and m are each integers, n being between 1 and 3 and m being between 1 and 5; and wherein the container is configured such that the at least one electrical component is accessible to be changed or replaced, and accessing the at least one electrical component exposes the fluoroketone to air.

2. The immersion cooling system of claim 1, wherein the fluoroketone has a boiling point of at least 130°C.

3. The immersion cooling system of claim 1, wherein the fluoroketone has a greater than a 25kV breakdown strength at a 2.5 mm gap, according to ASTM D877 (1987).

4. The immersion cooling system of claim 1; wherein n = m = 1.

5. The immersion cooling system of claim 1, wherein the fluoroketone has a 100-year GWP of less than 100.

6. The immersion cooling system of claim 1, wherein C_nF_2n is linear and CmFrm is linear.

7. The immersion cooling system of claim 1, wherein C_nF_2n is branched and CmF2m is branched. The immersion cooling system of claim 1, wherein the container includes a fluid conditioning loop. The immersion cooling system of claim 8, wherein the fluid containing loop includes filter media. A method of configuring an immersion cooling system, comprising: providing a container; disposing at least one electrical component within the container such that the at least one electrical component is accessible to be changed or replaced; and at least partially filling the container with a fluoroketone, wherein the fluoroketone is disposed such that the fluoroketone is in contact with the at least one electrical component, and that accessing the at least one electrical component exposes the fluoroketone to air; wherein the fluoroketone has a boiling point of at least 100°C but no higher than 200°C and is of the form

, wherein CnF2n is linear or branched, C_mF_2m is linear or branched, and n and m are each integers, n being between 1 and 3 and m being between 1 and 5.