Patent Description:
Various fluids for use in immersion cooling are described in, for example, <NPL>; and <NPL>. <CIT> describes a chiller apparatus containing E-<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-hexafluoro-<NUM>-butene. <CIT> discloses refrigerant compositions comprising E-<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-octafluoro-<NUM>-pentene and optionally <NUM>,<NUM>,<NUM>,<NUM>,<NUM>-pentafluoropropane. <CIT> teaches azeotrope-like compositions of Z-<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-hexafluoro-<NUM>-butene and E-<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-hexafluoro-<NUM>-butene. <CIT> describes <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-decafluorohex-<NUM>-ene isomer mixtures. <CIT> discloses fluoroolefin compositions useful as refrigerants or heat transfer fluids.

The present inventions provides an immersion cooling system. The immersion cooling system includes a housing having an interior space; a heat-generating component disposed within the interior space, wherein the heat generating component comprises an electronic device; and a working fluid liquid disposed within the interior space such that the heat-generating component is in contact with the working fluid liquid. The working fluid comprises at least <NUM> % by weight of a compound having Structural Formula (IA)
<CHM>
Each Rf<NUM> and Rf<NUM> is, independently, (i) a linear or branched perhalogenated acyclic alkyl group having <NUM>-<NUM> carbon atoms and optionally contains one or more catenated heteroatoms selected from O or N; or (ii) a perhalogenated <NUM>-<NUM> membered cyclic alkyl group having <NUM>-<NUM> carbon atoms and optionally contains one or more catenated heteroatoms selected from O or N. The working fluid is a fluid with a dielectric constant of less than <NUM>, wherein said dielectric constant is measured by ASTM D150 at <NUM> at <NUM>.

The invention further provides a method for cooling a heat generating component. The method includes at least partially immersing a heat generating component, wherein the heat generating component comprises an electronic device, in a working fluid; and transferring heat from the heat generating component using the working fluid. The working fluid includes at least <NUM>% by weight of a compound having Structural Formula (IA)
<CHM>
Each Rf<NUM> and Rf<NUM> is, independently, (i) a linear or branched perhalogenated acyclic alkyl group having <NUM>-<NUM> carbon atoms and optionally contains one or more catenated heteroatoms selected from O or N; or (ii) a perhalogenated <NUM>-<NUM> membered cyclic alkyl group having <NUM>-<NUM> carbon atoms and optionally contains one or more catenated heteroatoms selected from O or N. The working fluid has a dielectric constant of less than <NUM>, wherein said dielectric constant is measured at <NUM> at <NUM>.

The above summary of the present disclosure is not intended to describe each embodiment of the present disclosure. The details of one or more embodiments of the disclosure are also set forth in the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and from the claims.

Large scale computer server systems can perform significant workloads and generate a large amount of heat during their operation. A significant portion of the heat is generated by the operation of these servers. Due in part to the large amount of heat generated, these servers are typically rack mounted and air-cooled via internal fans and/or fans attached to the back of the rack or elsewhere within the server ecosystem. As the need for access to greater and greater processing and storage resources continues to expand, the density of server systems (i.e., the amount of processing power and/or storage placed on a single server, the number of servers placed in a single rack, and/or the number of servers and or racks deployed on a single server farm), continue to increase. With the desire for increasing processing or storage density in these server systems, the thermal challenges that result remain a significant obstacle. Conventional cooling systems (e.g., fan based) require large amounts of power, and the cost of power required to drive such systems increases exponentially with the increase in server densities. Consequently, there exists a need for efficient, low power usage system for cooling the servers, while allowing for the desired increased processing and/or storage densities of the server systems.

Two-phase immersion cooling is an emerging cooling technology for the high-performance server computing market which relies on the heat absorbed in the process of vaporizing a liquid (the cooling fluid) to a gas (i.e., the heat of vaporization). The fluids used in this application must meet certain requirements to be viable in the application. For example, the boiling temperature during operation should be in a range between for example <NUM>-<NUM>. Generally, this range accommodates maintaining the server components at a sufficiently cool temperature while allowing heat to be dissipated efficiently to an ultimate heat sink (e.g., outside air). The fluid must be inert so that it is compatible with the materials of construction and the electrical components. Certain perfluorinated and partially fluorinated materials may meet this requirement. The fluid should be stable such that it does not react with common contaminants such as water or with reagents such as activated carbon or alumina that might be used to scrub the fluid during operation. The global warming potential (GWP, 100yr ITH) and ozone depletion potential (ODP) of the parent compound and its degradation products should be below acceptable limits, for example, less than <NUM> and <NUM>, respectively. The fluids should have a dielectric constant (measured at room temperature (about <NUM>) at <NUM>) of less than <NUM>, such that high frequency electronic components and connectors can be submerged in the fluids without significant loss of signal integrity.

Single phase immersion cooling has a long history in computer server cooling. There is no phase change in single phase immersion. Instead the liquid warms and cools as it flows or is pumped to the computer server and a heat exchanger, respectively, thereby transferring heat away from the computer server. The fluids used in single phase immersion cooling of computer servers should meet the same requirements as outlined above with respect to two-phase immersion cooling, except that they typically have higher boiling temperatures exceeding about <NUM>-<NUM> to limit evaporative losses.

It is generally understood that perfluorinated liquids may exhibit dielectric constants of <NUM> or less. However, these materials are often associated with high GWP, well outside of the requirement for many industrial applications, including two-phase and single-phase immersion cooling. Therefore, there continues to be a need for working fluids useful for two-phase and single phase immersion cooling that satisfy the dielectric constant requirement of the industry (less than <NUM>), while also exhibiting GWPs (100yr ITH) that are below the acceptable limits for the industry (typically less than about <NUM>).

Generally, the present disclosure is directed to compositions, or working fluids, that exhibit boiling points, reactivity, stability, GWPs, and dielectric constants that render them particularly suitable for use as cooling fluids in two-phase and single phase immersion cooling systems.

As used herein, "catenated heteroatom" means an atom other than carbon (for example, oxygen, nitrogen, or sulfur) that is bonded to at least two carbon atoms in a carbon chain (linear or branched or within a ring) so as to form a carbon-heteroatom-carbon linkage.

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, "perhalogenated" means completely halogenated such that, except as may be otherwise indicated, any carbon-bonded hydrogens are replaced by a halogen atom.

As used herein, the singular forms "a", "an", and "the" include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended embodiments, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise.

As used herein, the recitation of numerical ranges by endpoints includes all numbers subsumed within that range (e.g. <NUM> to <NUM> includes <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>).

Unless otherwise indicated, all numbers expressing quantities or ingredients, measurement of properties and so forth used in the specification and embodiments are to be understood as being modified in all instances by the term "about.

The working fluid of the present disclosure includes a hydrofluoroolefin compound having the following Structural Formula (IA):
<CHM>.

Surprisingly, it was discovered that the alkylene segment of Structural Formula (IA), namely an alkylene segment in which each carbon of the segment is bonded to one hydrogen atom and one perhalogenated moiety in the E (or trans) configuration, provides surprisingly low dielectric constants of less than <NUM>. No other hydrofluoroolefin structures have been found which provide similarly low dielectric constants. Consequently, it has been discovered that the hydrofluorolefin compounds of the present disclosure have measured dielectric constants that render them particularly suitable for use as working fluids in immersion cooling systems, particularly those used for the immersion cooling of high performance computer server hardware or devices that operate at high frequencies (e. g, greater than <NUM>, or greater than <NUM>, or greater than <NUM>, or greater than <NUM>, or greater than <NUM>, or greater than <NUM>, or greater than <NUM>, or greater than <NUM>, or greater than <NUM>).

The hydrofluoroolefin compounds of Structural Formula (IA) represent the E (or trans) isomer of a hydrofluoroolefin that can exist in two isomeric forms, the other isomeric form being the Z (or cis) isomer, depicted in Structural Formula (IB):
<CHM>
Surprisingly, it has also been discovered that the (E) isomer (Structural Formula (IA)) has a significantly lower dielectric constant than its (Z) counterpart and, therefore, compositions rich in the (Z) isomer do not exhibit dielectric constants that would be suitable for use as working fluids in high performance server immersion cooling systems.

Each Rf<NUM> and Rf<NUM> is, independently, (i) a linear or branched perhalogenated acyclic alkyl group having <NUM>-<NUM>, <NUM> -<NUM>, or <NUM> - <NUM> carbon atoms and optionally contain one or more catenated heteroatoms selected from O or N; or (ii) a perhalogenated <NUM>-<NUM> membered cyclic alkyl group having <NUM>-<NUM> or <NUM>-<NUM> carbon atoms and optionally containing one or more catenated heteroatoms selected from O or N. In some embodiments, each perhalogenated Rf<NUM> and Rf<NUM> may be substituted with only fluorine atoms or chlorine atoms. In some embodiments, each perhalogenated Rf<NUM> and Rf<NUM> may be substituted with only fluorine atoms and one chlorine atom.

In some embodiments, each Rf<NUM> and Rf<NUM> may be, independently, (i) a linear or branched perfluorinated acyclic alkyl group having <NUM>-<NUM>, <NUM> -<NUM>, or <NUM> - <NUM> carbon atoms and optionally contain one or more catenated heteroatoms selected from O or N; or (ii) a perfluorinated <NUM>-<NUM> membered cyclic alkyl group having <NUM>-<NUM> or <NUM>-<NUM> carbon atoms and optionally containing one or more catenated heteroatoms selected from O or N. In some embodiments, Rf<NUM> and Rf<NUM> may be the same perfluorinated alkyl groups (acyclic or cyclic, including any catenated heteroatoms).

In some embodiments, the compositions of the present disclosure may be rich in the isomer of Structural Formula (IA) (the E isomer). In this regard, in some embodiments, the compositions of the present disclosure may include hydrofluoroolefins having Structural Formula (IA) in an amount of at least <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> weight percent, based on the total weight of the hydrofluoroolefins having Structural Formula (IA) and (IB) in the composition.

In various embodiments, representative examples of the compounds of general formula (I) include the following:
<CHM>
<CHM>
<CHM>
<CHM>
<CHM>.

In some embodiments, the hydrofluoroolefin compounds of the present disclosure may be hydrophobic, relatively chemically unreactive, and thermally stable. The hydrofluoroolefin compounds may have a low environmental impact. In this regard, the hydrofluoroolefin compounds of the present disclosure may have a zero, or near zero, ozone depletion potential (ODP) and a global warming potential (GWP, 100yr ITH) of less than <NUM>, <NUM>, <NUM>, <NUM> or less than <NUM>. As used herein, GWP is a relative measure of the global warming potential of a compound based on the structure of the compound. The GWP of a compound, as defined by the <NPL>, is calculated as the warming due to the release of <NUM> kilogram of a compound relative to the warming due to the release of <NUM> kilogram of CO<NUM> over a specified integration time horizon (ITH).

In this equation ai is the radiative forcing per unit mass increase of a compound in the atmosphere (the change in the flux of radiation through the atmosphere due to the IR absorbance of that compound), C is the atmospheric concentration of a compound, τ is the atmospheric lifetime of a compound, t is time, and i is the compound of interest. The commonly accepted ITH is <NUM> years representing a compromise between short-term effects (<NUM> years) and longer-term effects (<NUM> years or longer). The concentration of an organic compound, i, in the atmosphere is assumed to follow pseudo first order kinetics (i.e., exponential decay). The concentration of CO<NUM> over that same time interval incorporates a more complex model for the exchange and removal of CO<NUM> from the atmosphere (the Bern carbon cycle model).

In some embodiments, the fluorine content in the hydrofluoroolefin compounds of the present disclosure may be sufficient to make the compounds non-flammable according to ASTM D-<NUM>-<NUM> e-<NUM> test method ("Flash Point of Liquids by Small Scale Closed Cup Apparatus").

In some embodiments, the hydrofluoroolefin compounds represented by Structural Formula (IA) can be synthesized by the methods described in <CIT>, <CIT>, <CIT>, <NPL>, and <CIT>.

The working fluid of the present disclosure includes at least <NUM>% by weight of the above-described hydrofluoroolefins, based on the total weight of the composition. In some embodiments, the working fluids of the present disclosure may include at least <NUM>%, at least <NUM>%, at least <NUM>%, at least <NUM>%, or at least <NUM>% by weight of the above-described hydrofluoroolefins, based on the total weight of the composition. In addition to the hydrofluoroolefins, the compositions may include a total of up to <NUM>%, up to <NUM>%, up to <NUM>%, up to <NUM>%, up to <NUM>%, or up to <NUM>% by weight of one or more of the following components (individually or in any combination): ethers, alkanes, perfluoroalkenes, alkenes, haloalkenes, perfluorocarbons, perfluorinated tertiary amines, perfluoroethers, cycloalkanes, esters, perfluoroketones, ketones, oxiranes, aromatics, siloxanes, hydrochlorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, hydrofluoroolefins, hydrochloroolefins, hydrochlorofluoroolefins, hydrofluoroethers, or mixtures thereof based on the total weight of the working fluid; or alkanes, perfluoroalkenes, haloalkenes, perfluorocarbons, perfluorinated tertiary amines, perfluoroethers, cycloalkanes, perfluoroketones, aromatics, siloxanes, hydrochlorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, hydrofluoroolefins, , hydrochlorofluoroolefins, hydrofluoroethers, or mixtures thereof, based on the total weight of the working fluid. Such additional components can be chosen to modify or enhance the properties of a composition for a particular use.

The working fluid of the present disclosure has a dielectric constant less that is than <NUM> as measured with ASTM D150 at room temperature. In some embodiments, the working fluids of the present disclosure may have dielectric constants that are less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, less than <NUM>, or less than <NUM>, as measured in accordance with ASTM D150 at room temperature.

In some embodiments, the working fluids of the present disclosure may have a boiling point between <NUM>-<NUM>, or <NUM>-<NUM>, <NUM>-<NUM>, or <NUM>-<NUM>. In some embodiments, the working fluids of the present invention may have a boiling point greater than <NUM>, or greater than <NUM>, or greater than <NUM>, greater than <NUM>, or greater than <NUM>.

The present disclosure is directed to an immersion cooling system that includes the above-discussed hydrofluoroolefin-containing working fluids. The immersion cooling systems may be single-phase or two-phase immersion cooling systems.

In some embodiments, the immersion cooling systems may operate as two-phase vaporization-condensation cooling systems for cooling one or more heat generating components. As shown in <FIG>, in some embodiments, a two-phase immersion cooling system <NUM> may include a housing <NUM> having an interior space <NUM>. Within a lower volume 15A of interior space <NUM>, a liquid phase <NUM> of a hydrofluoroolefin-containing working fluid having an upper liquid surface 20A (i.e., the topmost level of the liquid phase <NUM>) may be disposed. The interior space <NUM> may also include an upper volume 15B extending from the liquid surface 20A up to an upper portion 10A of the housing <NUM>.

In some embodiments, a heat generating component <NUM> may be disposed within the interior space <NUM> such that it is at least partially immersed (and up to fully immersed) in the liquid phase <NUM> of the working fluid. That is, while heat generating component <NUM> is illustrated as being only partially submerged below the upper liquid surface 20A, in some embodiments, the heat generating component <NUM> may be fully submerged below the liquid surface 20A. In some embodiments, the heat generating components may include one or more electronic devices, such as computing servers.

In various embodiments, a heat exchanger <NUM> (e.g., a condenser) may be disposed within the upper volume 15B. Generally, the heat exchanger <NUM> may be configured such that it is able to condense a vapor phase 20B of the working fluid that is generated as a result of the heat that is produced by the heat generating element <NUM>. For example, the heat exchanger <NUM> may have an external surface that is maintained at a temperature that is lower than the condensation temperature of a vapor phase of the working fluid. In this regard, at the heat exchanger <NUM>, a rising vapor phase 20B of the working fluid may be condensed back to liquid phase or condensate 20C by releasing latent heat to the heat exchanger <NUM> as the rising vapor phase 20B comes into contact with the heat exchanger <NUM>. The resulting condensate 20C may then be returned back to the liquid phase <NUM> disposed in the lower volume of 15A.

In some embodiments, the present disclosure may be directed to an immersion cooling system which operates by single phase immersion cooling. Generally, the single phase immersion cooling system is similar to that of the two phase system in that it may include a heat generating component disposed within the interior space of a housing such that it is at least partially immersed (and up to fully immersed) in the liquid phase of the working fluid. The single phase system may further include a pump and a heat exchanger, the pump operating to move the working fluid to and from the heat generating components and the heat exchanger, and the heat exchanger operating to cool the working fluid. The heat exchanger may be disposed within or external to the housing.

While the present disclosure describes examples of suitable two-phase and single-phase immersion cooling systems, it is to be appreciated that the benefits and advantages of the hydrofluoroolefin-containing working fluids of the present disclosure may be realized in any known two-phase or single phase immersion cooling system.

The present disclosure is further directed to methods for cooling heat generating components. The methods include at least partially immersing the heat generating component (e.g., a computer server) in the above-described working fluid. The method further includes transferring heat from the heat generating component using the above-described working fluid.

The operation of the present disclosure will be further described with regard to the following detailed examples. These examples are offered to further illustrate various embodiments and techniques. It should be understood, however, that many variations and modifications may be made while remaining within the scope of the present disclosure.

The present disclosure is more particularly described in the following examples that are intended as illustrations only, since numerous modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise noted, all parts, percentages, and ratios reported in the following examples are on a weight basis. Reagents were purchased from Sigma Aldrich Company, St. Louis, MO, USA, unless otherwise indicated.

Examples <NUM>, <NUM>, and <NUM>, and Comparative Examples CE2, CE3, and CE4 were purchased from Synquest Laboratories, Alachua FL, USA, and used as received.

To prepare Example <NUM>, antimony pentafluoride (<NUM>, <NUM> mmol) was charged in a <NUM> Parr reactor. The reactor was sealed and cooled in dry ice. Vacuum was then applied when the reactor was cold. Then <NUM>,<NUM>-difluoro-N-(trifluoromethyl)methanimine (<NUM>, <NUM> mmol, prepared by the decarboxylation of bis(trifluoromethyl)carbamic fluoride, which can be prepared by the electrochemical fluorination of dimethyl formamide) and (E)-<NUM>,<NUM>,<NUM>,<NUM>-tetrafluoroprop-<NUM>-ene (<NUM>, <NUM> mmol, available from Honeywell) were then charged sequentially to the headspace of the reactor as liquids. The reactor was then placed in the stand, stirred and allowed to warm to room temperature. Once at room temperature, the heat on the reactor was gradually increased to <NUM>. After holding for <NUM> hours the reactor was cooled, vented and poured over ice. The weight of crude fluorochemical product that was recovered was <NUM>. Approximately <NUM>% of the total mass recovered is the desired product according to GC analysis. The material was subsequently purified by fractional distillation and the structure was verified to be primarily the (E) isomer of <NUM>,<NUM>,<NUM>-trifluoro-N,N-bis(trifluoromethyl)prop-<NUM>-en-<NUM>-amine by GC/MS and F19 and H1 NMR.

To prepare Comparative Example CE1, in a <NUM> <NUM>-neck round bottom flask equipped with overhead stirring, thermocouple, cold water condenser, dry N2 line and an addition funnel, sodium borohydride (<NUM>,<NUM> mmol) and diethylene glycol dimethyl ether (<NUM>) were charged. The mixture was stirred to dissolve some of the borohydride. The mixture was then cooled down to -<NUM>, <NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>-nonafluoro-<NUM>-(trifluoromethyl)pent-<NUM>-ene (<NUM>, <NUM> mmol) was then added via addition funnel dropwise with stirring while maintaining the temperature between -<NUM> to -<NUM>. Once the addition was complete, the batch was stirred at -<NUM> for another hour. Then reaction mixture was warmed to <NUM>, and quenched with <NUM> water and <NUM> <NUM>% H3PO4. The reaction mixture was transferred to a separatory funnel, <NUM> product was collected. GC-MS results indicate the crude product consisted of monohydride and dihydride mainly. The desired monohydride was further purified by fractional distillation yielding the pure material. The boiling point of the material is <NUM>. The structure was confirmed by GC/MS and F19 and H1 NMR.

Dielectric constants were determined using ASTM D150 at room temperature with the average value reported at <NUM>.

Claim 1:
An immersion cooling system comprising:
a housing having an interior space;
a heat-generating component disposed within the interior space, wherein the heat generating component comprises an electronic device; and
a working fluid liquid disposed within the interior space such that the heat-generating component is in contact with the working fluid liquid;
wherein the working fluid comprises at least <NUM>% by weight of a compound having Structural Formula (IA)
<CHM>
wherein each Rf<NUM> and Rf<NUM> is, independently, (i) a linear or branched perhalogenated acyclic alkyl group having <NUM>-<NUM> carbon atoms and optionally contains one or more catenated heteroatoms selected from O or N; or (ii) a perhalogenated <NUM>-<NUM> membered cyclic alkyl group having <NUM>-<NUM> carbon atoms and optionally contains one or more catenated heteroatoms selected from O or N, and wherein the working fluid is a fluid with a dielectric constant of less than <NUM>, wherein said dielectric constant is measured by ASTM D150 at <NUM> at <NUM>.