Heat-transfer fluid, apparatus, and methods

Abstract

Heat-transfer fluids free of halogenated (e.g., fluorinated) molecular species, where such heat- transfer fluids achieve performances that are within the tolerance limits set forth by the industry for nonhalogenated fluids, such heat-transfer fluids comprising monoethers and diethers. Heat transfer apparatuses including the heat transfer fluids and methods of transferring heat are provided.

Description

[0001] PA102864W002

[0002] HEAT-TRANSFER FLUID, APPARATUS, AND METHODS

[0003] TECHNICAL FIELD

[0004] 5 The present disclosure relates to heat-transfer fluids, heat-transfer apparatuses, and heat- transfer methods.

[0005] BACKGROUND

[0006] Heat-transfer fluids facilitate the movement of heat between a heat source and a heat sink or distribute heat concentrated in a small volume to a larger volume. Associated apparatuses facilitate heat0 transfer through the use of a heat-transfer fluid.

[0007] SUMMARY

[0008] Disclosed herein are heat-transfer fluids free of halogenated (e.g., fluorinated) molecular species, where such heat-transfer fluids achieve performances that are within the tolerance limits set forth by the5 industry for nonhalogenated fluids. In one aspect, provided herein are heat-transfer fluid comprising an ether, the ether represented by the structure 0 wherein

[0009] Ri and R2 are independently a C4 to C12 alkyl hydrocarbyl group or a C4 to CIO alkenyl hydrocarbyl group; and the total carbon count is 12 to 20.

[0010] In another aspect, provided herein are heat-transfer fluid comprising an ether, the ether represented by the structure wherein 0 R3 and R4 are independently a Cl to CIO alkyl hydrocarbyl group; each X is independently a hydrogen or a Cl to C3 alkyl hydrocarbyl group; n is an integer from 0 to 4 inclusive; and the total carbon count is 10 to 24. In another aspect, provided are heat transfer apparatuses comprising a heat source; a heat sink; and a heat transfer fluid in fluid communication with both the heat source and the heat sink; where the heat transfer fluid comprises a heat transfer fluid of the present disclosure.

[0011] In another aspect, provided are methods of transferring heat comprising providing a heat source; providing a heat sink; and providing a heat transfer fluid in fluid communication with both the heat source and the heat sink; where the heat transfer fluid comprises a heat transfer fluid of the present disclosure.

[0012] As used herein: the term “alkenyl hydrocarbyl group” refers to a hydrocarbyl group including unsaturated hydrocarbon species; the term “alkyl hydrocarbyl group” refers to a hydrocarbyl group including saturated hydrocarbon species; the term “free of’ means that a particular element, e.g., fluorine, is not present in a molecular structure or refers to an element in a mixture present in a concentration of less than 5 wt.%, less than 4 wt.%, less than 3 wt.%, less than 2 wt.%, less than 1 wt.%, or less than 0.5 wt.%; the term “hydrocarbyl group” refers to a univalent group formed by removing a hydrogen atom from a hydrocarbon, e.g., methyl, ethyl, phenyl, and includes both saturated and unsaturated hydrocarbon species.

[0013] Features and advantages of the present disclosure will be further understood upon consideration of the detailed description as well as the appended claims.

[0014] BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a schematic of a first exemplary heat transfer apparatus.

[0016] FIG. 2 is a schematic of a second exemplary heat transfer apparatus.

[0017] Repeated use of reference characters in the specification and drawings is intended to represent the same or analogous features or elements of the disclosure. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the disclosure. The figures may not be drawn to scale.

[0018] DETAILED DESCRIPTION

[0019] There is significant commercial interest in the development of fluids for use in heat transfer applications. Work in this field has typically focused on the use of highly fluorinated fluids due to the unique properties of highly fluorinated materials such as, for example, their low intermolecular interactions as well as their high to non-existent flash points. Immersion cooling is one of the heat-transfer applications where compositions having low viscosity and high flash point may find particular utility. For example, large-scale computer server systems perform significant workloads and draw a considerable amount of power. These servers are conventionally rack mounted and air-cooled via internal fans or fans attached to the back of the rack or elsewhere within the server ecosystem. As the need for higher density of computer components increases, more efficient conductive cooling mechanisms, such as immersion cooling, become increasingly attractive.

[0020] Other heat transfer applications and apparatuses may also be suitable for the heat transfer fluids described herein. For example, the ethers described herein may be used in a closed loop system, wherein the heat-transfer fluid facilitates transfer of heat from a heat source to a heat sink but is never directly in contact with the heat source. Instead, a heat-conductive medium is used to transfer heat between the heat source and the heat transfer fluid, including one or more of metals, thermal paste, and thermal interface materials.

[0021] Disclosed herein are heat-transfer fluids free of halogenated (e.g., fluorinated) molecular species, where such heat-transfer fluids achieve performances that are within the tolerance limits set forth by the industry for nonhalogenated fluids. When fluids that are not halogenated are used, they typically require the use of complex and often variable mixtures of molecules to achieve the desired performance. Advantageously, however, the disclosed heat-transfer fluids are generally not mixtures of many different non-halogenated compounds.

[0022] In addition to the benefits described above, the nonfluorinated fluids often employed for these cooling applications are frequently obtained from nonrenewable sources, such as, for example, petroleum by-products. In contrast, heat-transfer fluids of the present disclosure may have their raw materials sourced from renewable, biologically based feedstocks. Consequently, heat-transfer fluids of the present disclosure may offer a greener choice for consumers and should allow these fluids to have a high degree of ability to decompose if released into the environment.

[0023] Provided herein are heat-transfer fluids comprising an ether. In one aspect the ether is represented by the monoether structure wherein

[0024] Ri and R2 are independently a C4 to C12 alkyl hydrocarbyl group or a C4 to CIO alkenyl hydrocarbyl group; and the total carbon count is 12 to 20.

[0025] In another aspect, the ether is represented by the diether structure wherein

[0026] R3 and R4 are independently a Cl to CIO alkyl hydrocarbyl group; each X is independently a hydrogen or a Cl to C3 alkyl hydrocarbyl group; n is an integer from 0 to 4 inclusive; and the total carbon count is 10 to 24.

[0027] Ethers useful in embodiments of the present disclosure may be prepared by methods known to those of ordinary skill in the relevant arts and as described in the Examples below.

[0028] Heat transfer fluids of the present disclosure may have a kinematic viscosity at -20 °C of less than or equal to 25 cP as determined by the Kinematic Viscosity Measurement Test. Heat transfer fluids of the present disclosure may have a kinematic viscosity at -40 °C of less than or equal to 30 cP as determined by the Kinematic Viscosity Measurement Test. Heat transfer fluids of the present disclosure may have a kinematic viscosity at -60 °C of less than or equal to 100 cP as determined by the Kinematic Viscosity Measurement Test.

[0029] In some embodiments, heat-transfer fluids of the present disclosure may include a monoether represented by the structure

[0030] and combinations thereof.

[0031] In some preferred embodiments, heat transfer fluids of the present disclosure includes a monoether represented by the structure

[0032] In some embodiments, heat-transfer fluids of the present disclosure may include a diether represented by the structure

[0033] , and combinations thereof.

[0034] In some preferred embodiments, heat transfer fluids of the present disclosure may include a diether represented by the stmcture

[0035] In some embodiments, the heat transfer fluids disclosed herein may be incorporated into a heat transfer apparatus. FIG. 1 is a schematic of a first exemplary heat transfer apparatus. Referring to FIG. 1, heat transfer apparatus includes heat source 110, heat transfer channel 120 including heat transfer fluid 122, and heat sink 130. Heat source 110 may be any suitable heat source, including, for example, electronic devices such as a computer or a server. In the absence of a cooling system, heat source 110 may reach normal operating temperatures of 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, or higher (e.g., 125 °C) Heat transfer channel 120 may take any suitable form or be made from any suitable material. For example, in some embodiments heat transfer channel 120 may be a pipe or cable filled with heat transfer fluid 122. In some embodiments, heat transfer channel 120 is directly attached to heat source 110. In some embodiments, heat transfer channel 120 is attached to heat source 110 via a thermal adhesive, a thermal paste, a metal joint (e.g., solder), or combinations thereof. In some embodiments, heat transfer channel 120 is similarly attached to heat sink 130. Heat transfer fluid 122 is in fluid communication with both the heat source 110 and the heat sink 130. In some embodiments, heat transfer fluid 122 may be circulated without the aid of a pump or other mechanical forcing. In some embodiments, heat transfer fluid 122 may be circulated with the assistance of a pump. Heat transfer fluid 122 includes at least one ether as described herein.

[0036] Heat sink 130 is configured to release heat transferred from heat transfer fluid 122 to an external environment. In some embodiments, this external environment is air. Heat sink 130 may be configured with fins or another design element known to those of ordinary skill in the relevant arts to provide a high ratio between surface area and volume. This high ratio between surface area and volume of the heat sink 130 may assist in allowing the maximum heat energy to transfer between the heat sink 130 and the external environment.

[0037] FIG. 2 is a schematic of a second exemplary heat transfer apparatus. Heat transfer apparatus 200 is similar to heat transfer apparatus 100 of FIG. 1 except heat transfer fluid 222 is not only in fluid communication with but is also in direct contact with heat source 210. Referring to FIG. 2, heat transfer channel 220 provides a volume that surrounds heat source 210. Heat transfer fluid 222 is also in fluid communication with heat sink 230. As in the case of the heat transfer apparatus 100 in FIG. 1, a pump or other mechanism may be used to circulate heat transfer fluid 222. Heat transfer fluid 222 includes an ether as described herein. FIG. 2 illustrates an alternative exemplary approach wherein the heat source is immersed in, i.e., is in direct contact with, heat transfer fluid 222.

[0038] Modifications and enhancements to the general functional form shown in FIGS. 1 and 2 are contemplated; for example, access doors, support mechanisms, electronic cabling and components, monitoring sensors and hardware, piping and / or tubing, coatings, filters, and other mechanisms can be utilized as necessary or as suited to the particular application.

[0039] Objects and advantages of this disclosure are further illustrated by the following non-limiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure. EXAMPEES

[0040] Unless otherwise noted or readily apparent from the context, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight.

[0041] Materials Used in Examples

[0042] Preparation of Ethers Used in the Examples

[0043] Synthetic Method 1: Neat Protocol for the Synthesis of Diethers from 1,4-dibromobutane

[0044] To a round bottom flask was added solid potassium hydroxide (2.10 equiv) followed by the desired alcohol (3.50 equiv). The reaction mixture was allowed to stir at room temperature until the heat of dissolution dissipated. The reaction mixture was then heated to 70 °C. Once at that temperature 1,4-dibromobutane (1.00 equiv) was added in a slow dropwise fashion. Upon complete addition of the dibromide the reaction mixture was stirred at 70 °C overnight. The crude reaction mixture was then cooled to room temperature. Water was added to the solution until all of the salts were fully dissolved. The biphasic solution was poured into a separatory funnel, the reaction flask was washed with ethyl acetate to ensure full transfer, and the layers were separated. The organic layer was dried with Na2SC>4 or MgSOi transferred to a round bottom flask and the solvent was removed with a rotary evaporator. The resulting oil was then purified using vacuum distillation to yield the desired diether.

[0045] Synthetic Method 2: Dean-Stark Protocol for the Synthesis of Ethers 2a. Dean-Stark Protocol for the Synthesis of Monoethers

[0046] To a round bottom flask was added solid potassium hydroxide (3.00 equiv) followed by the desired alcohol (1.00 equiv), the solvent (cyclohexane or toluene depending on the boiling point of the other materials, enough to make a 5M solution relative to the diol), and finally the desired alkyl halide (2.00 equiv). A Dean-Stark trap filled with the desired solvent is added to the top of the flask followed by a reflux condenser. The reaction mixture is then heated to reflux overnight or until the maximum production of water based on the alkyl halide is reached. The reaction mixture is then cooled to room temperature and the solid is removed via vacuum filtration through a fritted funnel into a round bottom flask. The reaction flask and the solid in the filter was then washed with half the volume of solvent used in the reaction and this was washed into the round bottom flask. The solvent was then removed in the rotary evaporator. The resulting oil was then purified by vacuum distillation yielding the desired monoether.

[0047] 2b. Dean-Stark Protocol for the Synthesis of Diethers

[0048] To a round bottom flask was added solid potassium hydroxide (5.00 equiv) followed by the desired diol (1.00 equiv), the solvent (cyclohexane or toluene depending on the boiling point of the other materials, enough to make a 5M solution relative to the diol), and finally the desired alkyl halide (4.00 equiv). A Dean-Stark trap filled with the desired solvent is added to the top of the flask followed by a reflux condenser. The reaction mixture is then heated to reflux overnight or until the maximum production of water based on the alkyl halide is reached. The reaction mixture is then cooled to room temperature and the solid is removed via vacuum filtration through a fritted funnel into a round bottom flask. The reaction flask and the solid in the filter was then washed with half the volume of solvent used in the reaction and this was washed into the round bottom flask. The solvent was then removed in the rotary evaporator. The resulting oil was then purified by vacuum distillation yielding the desired diether.

[0049] Synthetic Method 3: Acid-catalyzed Preparations of Monoethers

[0050] To a 2L three neck round bottom flask equipped with a stir bar, a large Dean-Stark trap with a reflux condenser above it connected to a nitrogen inlet / outlet T-joint, a thermocouple, and a PTFE stopper was added 1000.8 g (6.93 mol) of 3,5,5-trimethylhexanol (Sigma Aldrich).75.8 g of wet Amberlite IR 120H resin (Sigma Aldrich) was added, along with 254 g of heptane (VWR Chemicals BDH) to rinse the resin beads in. A heating mantle was added and the Variac connected to it was set to 60 / 100. After 22 hours, the Variac was turned off and the reaction was cooled to 113 °C. An aliquot was removed for NMR analysis, which showed complete conversion of the alcohol. Once the reaction was cooled to room temperature, a l” pad of Celite 545 (Alfa Aesar) was packed in a glass medium fritted funnel. The contents of the flask, now a hazy, slightly brown liquid with black beads, were poured into the funnel and the fdtrate was collected in a 2 L distillation pot under vacuum. The flask was rinsed once with 70 mL of heptane and fdtered through Celite. The fdtrate was a pale-yellow liquid.

[0051] The volatiles were stripped after attaching a Vigreux column and a short path distillation head. The Variac was set to 48 / 100 and the vacuum was set to 50 torr. Once the temperature reached 100 °C, the pressure was lowered to 10 torr. Once collection ceased, the heat was turned off and the system was vented to the atmosphere. Next, the vacuum source was switched to a rotary vane pump connected to a Schlenk line. A 56 g forecut was removed and the main cut was distilled at 98.7 °C and 4 mtorr. 662.19 g of a clear, colorless liquid was collected in 71% yield.

[0052] Test Methods

[0053] Flash Point Measurement Test

[0054] Sample flash points were analyzed for Closed Cup Flash Point using ASTM D-3278-96 e-1 "FlashPoint of Liquids” by SETAFLASH SERIES 8‘ACTIVECOOL’ Small Scale Closed-Cup Apparatus.

[0055] Kinematic Viscosity Measurement Test

[0056] Between temperature of -20 and -60°C: Samples were measured on an ARES-G2 rheometer, using a 25mm diameter titanium recessed bob in a 27mm cup. Temperature was controlled from -20°C to -60°C at a temperature rate of l°C / minby a forced convection oven in nitrogen atmosphere. The temperature rate was chosen at 1°C to limit thermal lag. Viscosity was measured at a constant shear rate between 20 and 50s'1to increase measure sensitivity depending on instalment measured torque. In some case, a 50s- 1 was used to improve sensitivity even further. The comparison of the data at different shear rate implies that the fluids are expected to be Newtonian in shear.

[0057] Results

[0058] Table 1. Properties of Selected Monoethers

[0059] * EX4 is a mixture of the following three compounds:

[0060] Table 2. Properties of Selected Monoethers Table 3. Properties of Selected Monoethers

[0061] Table 4. Properties of Selected Monoethers

[0062] 15 Table 5. Properties of Selected Diethers

[0063] Table 6. Properties of Selected Diethers

[0064] * EX39 is a mixture of the following three compounds:

[0065] ** EX41 is a mixture of the following three compounds: Table 7. Properties of Selected Diethers

[0066] * M42 is a mixture of the following six compounds:

[0067] Table 8. Properties of Selected Diethers Table 9. Properties of Selected Diethers

[0068] Table 10. Properties of Selected Diethers All cited references, patents, and patent applications in the above application for letters patent are herein incorporated by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control. The preceding description, given in order to enable one of ordinary skill in the art to practice the claimed disclosure, is not to be construed as limiting the scope of the disclosure, which is defined by the claims and all equivalents thereto.

Claims

What is claimed is:A heat-transfer fluid comprising an ether, the ether represented by the structurewhereinRi and R2 are independently a C4 to C12 alkyl hydrocarbyl group or a C4 to CIO alkenyl hydrocarbyl group; and the total carbon count is 12 to 20.

2. The heat-transfer fluid of claim 1, wherein Ri and R2 are independently a C5 to CIO alkyl hydrocarbyl group or a CIO alkenyl hydrocarbyl group.

3. The heat-transfer fluid of claim 1 or claim 2, wherein Ri and R2 are different groups.

4. The heat-transfer fluid of any one of claims 1 to 3, wherein the heat transfer fluid has a kinematic viscosity at - 60°C of less than 100 cP as determined by the Kinematic Viscosity Measurement Test.

5. The heat-transfer fluid of any one of claims 1 to 3, wherein the heat transfer fluid has a kinematic viscosity at - 40°C of less than 30 cP as determined by the Kinematic Viscosity Measurement Test.

6. The heat-transfer fluid of any one of claims 1 to 3, wherein the heat transfer fluid has a kinematic viscosity at - 20°C of less than 25 cP as determined by the Kinematic Viscosity Measurement Test.

7. The heat-transfer fluid of any one of claims 1 to 6, wherein the ether is free of halogens selected from the group consisting of fluorine, chlorine, and combinations thereof.

8. A heat-transfer fluid comprising an ether, the ether represented by the structurewhereinR3 and R4 are independently a Cl to CIO alkyl hydrocarbyl group;each X is independently a hydrogen or a Cl to C3 alkyl hydrocarbyl group; n is an integer from 0 to 4 inclusive; and the total carbon count is 10 to 24.

9. The heat-transfer fluid of claim 8, wherein R3and R4 are independently a Cl to CIO alkyl hydrocarbyl group or a hydrocarbyl group or a C5 alkenyl hydrocarbyl group.

10. The heat-transfer fluid of claim 8 or claim 9, wherein R3and R4 are different groups.

11. The heat-transfer fluid of any one of claims 8 to 10, wherein the heat transfer fluid has a kinematic viscosity at - 60°C of less than 100 cP as determined by the Kinematic Viscosity Measurement Test.

12. The heat-transfer fluid of any one of claims 8 to 10, wherein the heat transfer fluid has a kinematic viscosity at - 40°C of less than 30 cP as determined by the Kinematic Viscosity Measurement Test.

13. The heat-transfer fluid of any one of claims 8 to 10, wherein the heat transfer fluid has a kinematic viscosity at - 20°C of less than 25 cP as determined by the Kinematic Viscosity Measurement Test.

14. The heat-transfer fluid of any one of claims 8 to 13, wherein the ether is free of halogens selected from the group consisting of fluorine, chlorine, and combinations thereof.

15. The heat-transfer fluid of claim 1, wherein the heat transfer fluid includes a monoether represented by the structureand combinations thereof.

16. The heat-transfer fluid of claim 1, wherein the heat transfer fluid includes a monoether represented by the structure17. The heat-transfer fluid of claim 8, wherein the heat transfer fluid includes a diether represented by the structure18. The heat-transfer fluid of claim 8, wherein the heat transfer fluid includes a diether represented by10 the structure19. A heat transfer apparatus, comprising: a heat source; a heat sink; and a heat transfer fluid in fluid communication with both the heat source and the heat sink; wherein the heat transfer fluid comprises the heat transfer fluid of claim 1 or claim 8.

20. A method of transferring heat, comprising: providing a heat source; providing a heat sink; and providing a heat transfer fluid in fluid communication with both the heat source and the heat sink; wherein the heat transfer fluid comprises the heat transfer fluid of claim 1 or claim 8.

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