Heat-transfer fluid including cyclic siloxanes, 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 a cyclic siloxane, the cyclic siloxane represented by the structure (I), where R1 is a hydrocarbyl group or a heterohydrocarbyl group; R2 is hydrogen or a hydrocarbyl group; R3 is hydrogen or a hydrocarbyl group; and R4 is R2 or R3. Heat transfer apparatuses including the heat transfer fluids and methods of transferring heat are provided.

Description

[0001] HEAT-TRANSFER FLUID INCLUDING CYCLIC SILOXANES, APPARATUS, AND METHODS

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to heat-transfer fluids, heat-transfer apparatuses, and heat- transfer methods.

[0004] BACKGROUND

[0005] 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 heat transfer through the use of a heat-transfer fluid.

[0006] SUMMARY

[0007] 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. In one aspect, provided herein are heat-transfer fluid comprising a cyclic siloxane, the cyclic siloxane represented by the structure where Ri is a hydrocarbyl group or a hetero hydrocarbyl group; R2 is hydrogen or a hydrocarbyl group; R3 is hydrogen or a hydrocarbyl group; and R4 is R2 or R3.

[0008] 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.

[0009] 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.

[0010] As used herein: 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 “hetero hydrocarbyl group” refers to a univalent group formed by removing a hydrogen atom from a hydrocarbon that incorporates at least one heteroatom, e.g., nitrogen, oxygen, sulfur, in the carbon chain, and includes both saturated and unsaturated species. 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.

[0011] Features and advantages of the present disclosure will be further understood upon consideration of the detailed description as well as the appended claims.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a schematic of a first exemplary heat transfer apparatus.

[0014] FIG. 2 is a schematic of a second exemplary heat transfer apparatus.

[0015] 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.

[0016] DETAILED DESCRIPTION

[0017] 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.

[0018] 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.

[0019] Other heat transfer applications and apparatuses may also be suitable for the heat transfer fluids described herein. For example, the cyclic siloxanes 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.

[0020] 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.

[0021] Provided herein are heat-transfer fluids comprising a cyclic siloxane, the cyclic siloxane represented by the structure where Ri is a hydrocarbyl group or a hetero hydrocarbyl group; R2 is hydrogen or a hydrocarbyl group; R3 is hydrogen or a hydrocarbyl group; and and R4 is R2 or R3.

[0022] Cyclic siloxane s 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.

[0023] Heat transfer fluids of the present disclosure may have an absolute viscosity at 23 °C of less than 25 cP, less than 10 cP, less than 5 cP, or less than 1 cP as determined by the Room-Temperature Viscosity Measurement Test. In some embodiments, the heat transfer fluid may have a kinematic viscosity at - 60°C of less than 100 cSt, less than 50 cSt, less than 25 cSt, or less than 10 cSt as determined by the Kinematic Viscosity Measurement Test. In some embodiments, the heat transfer fluid may have a pour point of less than -70 °C, less than -80 °C, less than -90 °C, or less than -100 °C as as determined by the Pour Point Measurement Test.

[0024] In some embodiments, heat-transfer fluids of the present disclosure may include a cyclic siloxane represented by the structure In some embodiments, heat-transfer fluids of the present disclosure may include a cyclic siloxane represented by the structure

[0025] In some embodiments, heat-transfer fluids of the present disclosure may include a cyclic siloxane represented by the structure

[0026] 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 cyclic siloxane as described herein.

[0027] 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.

[0028] 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 cyclic siloxane 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.

[0029] 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.

[0030] 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.

[0031] EXAMPLES

[0032] 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. Materials

[0033] Test Methods

[0034] Flash Point Measurement Test

[0035] Sample flash points are analyzed for Closed Cup Flash Point using ASTM D-3278-96 e-1 "Flash Point of Liquids” by SETAFLASH SERIES 8‘ACTIVECOOL’ Small Scale Closed-Cup Apparatus.

[0036] Kinematic Viscosity Measurement Test

[0037] Between temperature of -20 and -60°C: Samples are measured on an ARES-G2 rheometer, using a 25mm diameter titanium recessed bob in a 27mm cup. Temperature is controlled from -20°C to -60°C at a temperature rate of l°C / min by a forced convection oven in nitrogen atmosphere. The temperature rate is chosen at 1°C to limit thermal lag. Viscosity is measured at a constant shear rate between 20 and 50s'1to increase measure sensitivity depending on instrument measured torque. In some case, a 50s- 1 is 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.

[0038] Pour Point Measurement Test

[0039] A sealed glass vial containing 1 mL of the target fluid is placed into a stirred Dewar Flask containing cold iso-pentane bath fluid. The vial is attached directly to the thermocouple probe. The bath fluid is chilled by placing a plastic beaker of liquid nitrogen in contact with the bath fluid, cooling until the sample does not pour. Temperature is increased in 1 deg C increments until it pours. Pouring is defined as visible movement of the material during a five second count, as specified in ASTM D97.

[0040] Room-Temperature Viscosity Measurement Test

[0041] Absolute viscosity is measured using a VL- 4000 viscometer (Cambridge Viscosity, Inc., Boston MA, USA) with the piston tuned for the 1 - 20 cP measurement parameter.

[0042] Preparation of Cyclic Siloxanes Used in the Examples For examples EXI - EX3, the following general procedure is used with the quantities as shown in Table 1. The PT CATALYST is diluted from 2% w / w, as received, to 0.2% w / w using toluene immediately prior to use.

[0043] To a 500 mL 3 -neck reaction flask fitted with a thermocouple and temperature controller (J-KEM Scientific, Model Apollo, St. Louis, MO), a 29 / 42 PTFE tube adapter for 1 / 8” tubing and a distillation head (Ace Glass Model 7792-20, Vineland, NJ) is added D4H, toluene and 0.2% w / w PT CATALYST according to Table 1. The distillation head is fitted with a 250 mL round bottom receiver. Nitrogen gas is introduced into the reaction assembly through the thermometer port of the distillation head. The reaction flask is heated to 50°C using a heating mantle. The desired alkene is introduced into the reaction flask through the 29 / 42 port using a syringe pump (Cole Parmer Model 270, Vernon Hills, IL) at a rate of 0.5 mL / min. After the alkene is added to the reaction flask, the temperature is raised to 60°C for 2 hours. At the end of the two-hour period, the temperature is further raised to 125°C and the toluene is distilled off. Once the rate of distillation has slowed down, the reaction mixture is further subjected to a 20 - 50 mmHg vacuum at 130°C for a period of 1 hour. The reaction mixture is then cooled down to ambient temperature and collected.

[0044] Table 1. Reagent Quantities for Examples EXI - EX3.

[0045] 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:

1. A heat-transfer fluid comprising a cyclic siloxane, the cyclic siloxane represented by the structurewhereinRi is a hydrocarbyl group or a heterohydrocarbyl group;R2 is hydrogen or a hydrocarbyl group;R3 is hydrogen or a hydrocarbyl group; andR4 is R2 or R3.

2. The heat-transfer fluid of claim 1, wherein the heat transfer fluid has as an absolute viscosity at 23 °C of less than 25 cP, less than 10 cP, less than 5 cP, or less than 1 cP as determined by the Room- Temperature Viscosity Measurement Test.

3. The heat-transfer fluid of claim 1 or claim 2, wherein the heat transfer fluid has a kinematic viscosity at - 60°C of less than 100 cSt, less than 50 cSt, less than 25 cSt, or less than 10 cSt as determined by the Kinematic Viscosity Measurement Test.

4. The heat-transfer fluid of any one of claims 1 to 3, wherein the heat transfer fluid has a pour point of less than -70 °C, less than -80 °C, less than -90 °C, or less than -100 °C as determined by the Pour Point Measurement Test.

5. The heat-transfer fluid of any one of claims 1 to 4, wherein the cyclic siloxane is free of halogens selected from the group consisting of fluorine, chlorine, and combinations thereof.

6. The heat-transfer fluid of any one of claims 1 to 5, wherein the heat transfer fluid is free of halogens selected from the group consisting of fluorine, chlorine, and combinations thereof.

7. The heat-transfer fluid of any one of claims 1 to 6, wherein the heat transfer fluid includes a cyclic siloxane represented by the structure8. The heat-transfer fluid of any one of claims 1 to 7, wherein the heat transfer fluid includes a cyclic siloxane represented by the structure9. The heat-transfer fluid of any one of claims 1 to 8, wherein the heat transfer fluid includes a cyclic siloxane represented by the structure10. 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 any one of claims 1 to 9.

11. 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 any one of claims 1 to 9.

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