Heat transfer fluids, devices and methods

Abstract

Heat transfer fluids that do not contain halogenated (e.g., fluorinated) molecules, wherein such heat transfer fluids achieve performance within the tolerance limits described in industry for non-halogenated fluids, such heat transfer fluids comprise esters represented by structural formulas (I), (II), and (III), or wherein R and R' are independently C4 to C10 hydrocarbon groups; each X and Y is independently hydrogen or C1 to C2 hydrocarbon groups; n is an integer from 0 to 6, inclusive; and m is an integer from 2 to 4, inclusive. Heat transfer devices and methods incorporating heat transfer fluids are provided.

Description

Technical Field

[0001] This disclosure relates to heat transfer fluids, heat transfer devices, and heat transfer methods. Background Technology

[0002] Heat transfer fluids facilitate the movement of heat between a heat source and a radiator, or distribute heat concentrated in a small volume to a larger volume. Associated devices utilize heat transfer fluids to enhance heat transfer. Summary of the Invention

[0003] This document discloses heat transfer fluids that do not contain halogenated (e.g., fluorinated) molecules, wherein such heat transfer fluids achieve performance within the tolerance limits defined for non-halogenated fluids in industry. In one aspect, this document provides a heat transfer fluid comprising an ester, which is represented by the following structure:

[0004]

[0005] Where R and R' are independently C4 to C10 hydrocarbon groups; each X and Y is independently hydrogen or C1 to C2 hydrocarbon groups; n is an integer from 0 to 6, including the end value; and m is an integer from 2 to 4, including the end value.

[0006] On the other hand, a heat transfer device is provided, comprising: a heat source; a radiator; and a heat transfer fluid in fluid communication with both the heat source and the radiator; wherein the heat transfer fluid includes the heat transfer fluid of this disclosure.

[0007] In another aspect, a method for transferring heat is provided, the method comprising: providing a heat source; providing a radiator; and providing a heat transfer fluid in fluid communication with both the heat source and the radiator; wherein the heat transfer fluid includes the heat transfer fluid of this disclosure.

[0008] As used in this article:

[0009] The term "chiral center" refers to an sp-axis bonded to four different atoms or groups. 3 Carbon atoms, which prevent them from overlapping in their mirror image;

[0010] The term “free” means that a specific element (e.g., fluorine) is not present in the molecular structure, or that the element is present in the mixture at a concentration of less than 5% by weight, less than 4% by weight, less than 3% by weight, less than 2% by weight, less than 1% by weight, or less than 0.5% by weight.

[0011] The term "hydrocarbon group" refers to a monovalent group (e.g., methyl, ethyl, phenyl) formed by removing hydrogen atoms from a hydrocarbon, and includes both saturated and unsaturated hydrocarbon substances.

[0012] The features and advantages of this disclosure will be further understood when considered in conjunction with the specific embodiments and the appended claims. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a first exemplary heat transfer device.

[0014] Figure 2 This is a schematic diagram of a second exemplary heat transfer device.

[0015] Reference numerals used repeatedly in the specification and drawings are intended to indicate the same or similar features or elements of this disclosure. It should be understood that those skilled in the art can devise many other modifications and embodiments that fall within the scope and spirit of the principles of this disclosure. The drawings may not be drawn to scale. Detailed Implementation

[0016] Developing fluids for heat transfer applications has significant commercial benefits. Due to the unique properties of highly fluorinated materials (such as their low intermolecular interactions and their high to non-existent flash points), work in this field has generally focused on the use of highly fluorinated fluids.

[0017] Immersion cooling is a type of heat transfer application where compositions with low viscosity and high flash points can find particular utility. For example, large-scale computer server systems perform significant workloads and draw large amounts of power. These servers are typically rack-mounted and air-cooled via internal fans or fans attached to the back of the rack or elsewhere in the server ecosystem. As the demand for higher densities of computer components increases, more efficient conductive cooling mechanisms, such as immersion cooling, are becoming increasingly attractive.

[0018] Other heat transfer applications and devices can be adapted to the heat transfer fluids described herein. For example, the esters described herein can be used in closed-loop systems where the heat transfer fluid facilitates heat transfer from a heat source to a radiator but never comes into direct contact with the heat source. Conversely, a thermally conductive medium is used to transfer heat between a heat source and the heat transfer fluid; this thermally conductive medium includes one or more of metals, thermal pastes, and thermal interface materials.

[0019] This paper discloses heat transfer fluids that do not contain halogenated (e.g., fluorinated) molecules, wherein such heat transfer fluids achieve performance within the tolerance limits defined for non-halogenated fluids in industry. When using non-halogenated fluids, they typically require complex and often variable molecular mixtures to achieve the desired performance. However, advantageously, the disclosed heat transfer fluids are not typically mixtures of many different non-halogenated compounds, but rather mixtures of diastereomeric compounds comprising substantially the same few compounds but with different atomic arrangements in three-dimensional space.

[0020] In addition to the benefits described above, non-fluorinated fluids typically used in these cooling applications are usually derived from non-renewable sources, such as petroleum byproducts. In contrast, the heat transfer fluids of this disclosure may have raw materials derived from renewable bio-based feedstocks. Therefore, the heat transfer fluids of this disclosure offer consumers a greener option and should allow for high decomposition capacity if released into the environment.

[0021] This article provides a heat transfer fluid comprising an ester, which is represented by the following structure:

[0022]

[0023] Where R and R' are independently C4 to C10 saturated or unsaturated hydrocarbon groups; each X and Y is independently hydrogen or C1 to C2 hydrocarbon group; n is an integer from 0 to 6, including the end value; and m is an integer from 2 to 4, including the end value.

[0024] The esters that can be used in embodiments of this disclosure can be prepared by methods known to those skilled in the art and described in the examples below. In some embodiments, the ester may contain one, optionally two, optionally three, optionally four, optionally five, or optionally six chiral centers. In some embodiments, the ester may be free of halogens selected from the group consisting of fluorine, chlorine, and combinations thereof.

[0025] The heat transfer fluid disclosed herein may have an absolute viscosity of less than 10 cP, less than 9 cP, less than 8 cP, or less than 7 cP at 23°C, as determined by a room temperature viscosity measurement test. In some embodiments, the heat transfer fluid may have a kinematic viscosity of less than 3000 cSt, less than 2000 cSt, less than 1000 cSt, less than 900 cSt, less than 800 cSt, less than 700 cSt, less than 600 cSt, less than 500 cSt, less than 400 cSt, less than 300 cSt, or less than 200 cSt at -60°C, as determined by a kinematic viscosity measurement test. In some embodiments, the heat transfer fluid may have a pour point of less than -50°C, less than -60°C, less than -70°C, less than -80°C, or less than -90°C, as determined by a pour point measurement test.

[0026] In some embodiments, the heat transfer fluid of this disclosure may comprise a diester, which is represented by the following structure:

[0027]

[0028] And their combinations.

[0029] In some embodiments, the heat transfer fluid of this disclosure may comprise an ester, which is represented by the following structure:

[0030]

[0031] And their combinations.

[0032] In some embodiments, the heat transfer fluid of this disclosure may comprise an ester comprising a mixture of various compositional isomers of a C10 acid, wherein the α-center is a quaternary center, and such esters are represented by the following structures:

[0033]

[0034] And their combinations.

[0035] In some embodiments, the heat transfer fluid of this disclosure may comprise a diester, which is represented by the following structure:

[0036]

[0037] And their combinations.

[0038] In some implementations, the heat transfer fluid disclosed herein may be incorporated into the heat transfer device. Figure 1 This is a schematic diagram of a first exemplary heat transfer device. (Reference) Figure 1 The heat transfer device includes a heat source 110, a heat transfer channel 120 including a heat transfer fluid 122, and a radiator 130. The heat source 110 can be any suitable heat source, including electronic equipment such as a computer or server. Without a cooling system, the heat source 110 can reach a normal operating temperature of 40°C, 50°C, 60°C, 70°C, 80°C, or higher (e.g., 125°C). The heat transfer channel 120 can take any suitable form or be made of any suitable material. For example, in some embodiments, the heat transfer channel 120 can be a pipe or cable filled with the heat transfer fluid 122. In some embodiments, the heat transfer channel 120 is directly attached to the heat source 110. In some embodiments, the heat transfer channel 120 is attached to the heat source 110 via thermally conductive adhesive, thermal paste, or a metal connector (e.g., solder) or a combination thereof. In some embodiments, the heat transfer channel 120 is similarly attached to the radiator 130. The heat transfer fluid 122 is in fluid communication with both the heat source 110 and the radiator 130. In some embodiments, the heat transfer fluid 122 can be circulated without the aid of a pump or other mechanical force. In some embodiments, the heat transfer fluid 122 can be circulated with the assistance of a pump. The heat transfer fluid 122 comprises at least one diester as described herein.

[0039] Heat sink 130 is configured to release heat transferred from heat transfer fluid 122 to the external environment. In some embodiments, the external environment is air. Heat sink 130 may be configured with fins or other design elements known to those skilled in the art to provide a high surface area to volume ratio. This high surface area to volume ratio of heat sink 130 helps to allow maximum heat transfer between heat sink 130 and the external environment.

[0040] Figure 2 This is a schematic diagram of a second exemplary heat transfer device. The heat transfer device 200 is similar to... Figure 1 The heat transfer device 100 differs in that the heat transfer fluid 222 is not only in fluid communication with the heat source 210, but also in direct contact with the heat source. (Reference) Figure 2 The heat transfer channel 220 provides the volume surrounding the heat source 210. The heat transfer fluid 222 is also in fluid communication with the radiator 230. As... Figure 1 In the case of heat transfer device 100, a pump or other mechanism may be used to circulate heat transfer fluid 222. Heat transfer fluid 222 contains esters as described herein. Figure 2 An alternative exemplary method is illustrated, wherein the heat source is immersed in the heat transfer fluid 222, i.e., in direct contact with the heat transfer fluid.

[0041] It can be expected that... Figure 1 and Figure 2 Modifications and enhancements to the general functional form shown; for example, access doors, support mechanisms, electronic cables and components, monitoring sensors and hardware, pipes and / or tubes, coatings, filters and other mechanisms may be utilized as needed or suitable for a particular application.

[0042] The purposes and advantages of this disclosure are further illustrated by the following non-limiting examples, but the specific materials and quantities cited in these examples, as well as other conditions and details, should not be considered as an excessive limitation of this disclosure.

[0043] Example

[0044] Unless otherwise specified or readily apparent from the context, all parts, percentages, ratios, etc., in the embodiments and the remainder of the specification are by weight.

[0045]

[0046] The ester used in the preparation examples

[0047] Preparation of esters in Table 1 :

[0048] The desired alcohol (2.08 equivalents) is added to a solution of the desired diacid or cyclic anhydride (1.00 equivalents) and p-toluenesulfonic acid monohydrate (0.01 equivalents) in heptane in a round-bottom flask equipped with a stir bar. A Dean-Stark apparatus and a reflux condenser are attached, and the reaction mixture is heated under reflux with stirring until the desired amount of water is produced. The reaction is cooled to room temperature, and the organic layer is washed with multiple portions of saturated NaHCO3 aqueous solution until the pH of the organic layer is neutral. The organic layer is dried with MgSO4, and the solvent is removed using a rotary evaporator. The concentrated solution is then purified by vacuum distillation to separate the desired ester, which is a clear, colorless liquid.

[0049] Preparation of esters in Table 2 :

[0050] Acyl chloride scheme

[0051] Add tert-carbonic acid (1.00 equivalents) to an oven-dried flask equipped with a reflux condenser, which has been purged three times. Then add anhydrous DMF (0.005 equivalents). Cool the solution to 0°C and then add oxaloyl chloride (1.02 equivalents) dropwise to minimize gas release from the solution. While the addition of oxaloyl chloride is complete, allow the reaction to slowly heat to room temperature and stir overnight. The next day, cool the solution to 0°C and then add pyridine (2.10 equivalents) slowly to the reaction. While the addition of pyridine is complete, stir the solution at 0°C for 20 minutes, then add the desired alcohol (1.20 equivalents) dropwise rapidly. Then heat the solution to room temperature and then to reflux or 100°C, whichever is lower, overnight. The next day, cool the reaction to room temperature and then remove the solid by vacuum filtration, washing the solid with a small amount of dichloromethane. The organic layer is then washed with 3M HCl solution until it is acidic. The organic layer was then washed with a portion of water, and subsequently washed continuously with a saturated aqueous solution of NaHCO3 until a neutral pH was reached. The resulting organic layer was dried with MgSO4, and the solvent was removed using a rotary evaporator to obtain an oily substance. This oily substance was purified by vacuum distillation to obtain the desired material as a clear, colorless liquid.

[0052] S N 2 options

[0053] Over a period of several minutes, tertiary carbonate (1.00 equivalent) is slowly added to a solution of K₂CO₃ (1.01 equivalent) in DMF (sufficient DMF to obtain a concentration of 2M relative to the acid and DMF) in a round-bottom flash evaporator equipped with a large stir bar. The reaction is heated to 100°C and maintained for 1 hour or until CO₂ production ceases, whichever is later. Then, the desired alkyl halide (1.20 equivalent) is added dropwise over a period of time to maintain the internal temperature within ±5 degrees of 100°C. The reaction is heated overnight while the alkyl halide is completely added. After heating overnight, the reaction is cooled to room temperature, and the solid is then removed by vacuum filtration, retaining the liquid layer. The solvent is removed using a rotary evaporator, and the resulting oil is then purified by vacuum distillation to obtain the desired product as a clear, colorless oil.

[0054] Preparation of esters in Table 3 :

[0055] Fischer esterification scheme

[0056] The desired carboxylic acid (3.00 equivalents) was added to a solution of the desired diol (1.00 equivalents) and p-toluenesulfonic acid (0.01 equivalents) in toluene (sufficient toluene to obtain a diol concentration of 10 M relative to the volume of toluene) in a round-bottom flask equipped with a stir bar. A Dean-Stark apparatus and a reflux condenser were attached, and the reaction mixture was heated under reflux with stirring until the desired amount of water was produced. The reaction was cooled to room temperature, and the organic layer was washed with multiple portions of saturated NaHCO3 aqueous solution until the pH of the organic layer was neutral. The organic layer was dried with MgSO4, and the solvent was removed using a rotary evaporator. The concentrated solution was then purified by vacuum distillation to separate the desired ester, which was a clear, colorless liquid.

[0057] Acyl chloride scheme

[0058] Add the desired carboxylic acid (1.05 equivalents) to an oven-dried 250 mL round-bottom flask equipped with a stir bar and a reflux condenser, followed by dichloromethane (sufficient DCM to make the solution 3.3 M relative to the alcohol) and DMF (0.02 equivalents). Cool the reaction mixture to 0 °C with stirring, and then add oxalyl chloride (1.04 equivalents) dropwise. Upon completion of the addition, allow the reaction to slowly reach room temperature and stir overnight at that temperature. Then, cool the reaction mixture to 0 °C and add triethylamine (2.15 equivalents) dropwise. Add more DCM to the solution (sufficient DCM to make the final concentration of alcohol relative to DCM 1.8 M). Upon completion of the DCM addition, add the alcohol dropwise slowly, and allow the reaction to slowly reach room temperature and stir overnight at that temperature. The solution was then vacuum filtered to remove solids, and the filtered liquid was extracted with 3M HCl until the organic layer was acidic, extracted with a fraction of deionized water, extracted with saturated NaHCO3 solution until the pH of the organic layer was neutral, and extracted with a final fraction of deionized water. The resulting organic layer was dried with MgSO4, and the solvent was removed using a rotary evaporator to obtain a colored oil. The colored oil was purified by vacuum distillation to obtain the desired product as a clear, colorless oil.

[0059] Preparation of esters in Table 4 :

[0060] Add p-toluenesulfonic acid (0.005 equivalents) to a round-bottom flask, followed by the desired alcohol (1.00 equivalents), carboxylic acid (1.02 equivalents), and then heptane or toluene (sufficient solvent to obtain an alcohol concentration of 10 M relative to the solvent volume). Attach a Dean-Stark apparatus and a reflux condenser, and heat the reaction mixture under reflux with stirring until the desired amount of water is produced. Then, cool the reaction to room temperature and wash the organic layer with a saturated aqueous solution of NaHCO3 until the pH of the organic layer is 7. Dry the organic layer with MgSO4, and then remove the solvent using a rotary evaporator. The resulting oily substance is then purified by vacuum distillation to give the desired ester as a clear, colorless liquid.

[0061] Test methods

[0062] Flash point measurement test

[0063] The flash point of the sample was analyzed using ASTM D-3278-96 e-1, "SETAFLASH Series 8 'ACTIVECOOL' Small Closed Cup Apparatus for the Determination of Flash Point of Liquids".

[0064] Kinematic viscosity measurement test

[0065] Between -20°C and -60°C: Samples were measured on an ARES-G2 rheometer using a 25mm diameter titanium recessed rotor in a 27mm cup. Temperatures were controlled between -20°C and -60°C in a forced convection oven under a nitrogen atmosphere at a temperature rate of 1°C / min. A temperature rate of 1°C was chosen to limit thermal hysteresis. (20s) -1 With 50s -1 Viscosity is measured at a constant shear rate to increase measurement sensitivity based on the torque measured by the instrument. In some cases, 50 s⁻¹ is used to further improve sensitivity. Comparison of data at different shear rates implies that the fluid is expected to be a Newtonian fluid under shear.

[0066] Pour point measurement test

[0067] Place a sealed glass vial containing 1 mL of the target fluid into a stirred Dewar flask containing a cold isopentane bath. Connect the vial directly to a thermocouple probe. Cool the bath by bringing a plastic beaker of liquid nitrogen into contact with the bath and cooling until the sample no longer tipes. Increase the temperature in 1°C increments until tipping occurs. Tipping is defined as the visible movement of material during a five-second count, as specified in ASTM D97.

[0068] Room temperature viscosity measurement test

[0069] Absolute viscosity was measured using a VL-4000 viscometer (CambridgeViscosity, Inc., Boston MA, USA), with the piston tuned for measurement parameters from 1 cP to 20 cP.

[0070] result

[0071]

[0072]

[0073]

[0074]

[0075] All references, patents, and patent applications cited in the above-mentioned patent-certified applications are incorporated herein by reference in their entirety. In the event of any inconsistency or contradiction between the incorporated references and this application, the information in the foregoing description shall prevail. The foregoing description, given to enable those skilled in the art to practice this disclosure protected by the claims, should not be construed as a limitation on the scope of this disclosure, which is defined by the claims and all their equivalents.

Claims

1. A heat transfer fluid comprising an ester, the ester represented by the structure: wherein R and R' are independently C4 to C10 hydrocarbyl groups; each X and Y is independently hydrogen or a Ci to C2 hydrocarbyl group; n is an integer from 0 to 6, inclusive; and m is an integer from 2 to 4, inclusive.

2. The heat transfer fluid of claim 1, wherein the ester comprises 1, optionally 2, optionally 3, optionally 4, optionally 5, or optionally 6 chiral centers.

3. The heat transfer fluid of claim 1, wherein the heat transfer fluid has an absolute viscosity at 23 °C of less than 10 cP, less than 9 cP, less than 8 cP, or less than 7 cP, as determined by the Room Temperature Viscosity Measurement Test.

4. The heat transfer fluid of claim 1, wherein the heat transfer fluid has a kinematic viscosity at -60 °C of less than 3000 cSt, less than 2000 cSt, less than 1000 cSt, less than 900 cSt, less than 800 cSt, less than 700 cSt, less than 600 cSt, less than 500 cSt, less than 400 cSt, less than 300 cSt, or less than 200 cSt, as determined by the Kinematic Viscosity Measurement Test.

5. The heat transfer fluid of claim 1, wherein the heat transfer fluid has a pour point of less than -50 °C, less than -60 °C, less than -70 °C, less than -80 °C, or less than -90 °C, as determined by the Pour Point Measurement Test.

6. The heat transfer fluid of claim 1, wherein the ester is free of halogens selected from the group consisting of fluorine, chlorine, and combinations thereof.

7. The heat transfer fluid of claim 1, wherein the heat transfer fluid comprises an ester represented by the structure:

8. The heat transfer fluid of claim 1, wherein the heat transfer fluid comprises an ester represented by the structure: 。 and combinations thereof.

9. The heat transfer fluid of claim 1, wherein the heat transfer fluid comprises a di-ester represented by the structure: and combinations thereof.

10. A heat transfer device 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.

11. A method of transferring heat, the method 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. ； ​

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