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US-12617992-B1 - Nanofluid for heat transfer, method for producing a nanofluid and method for recycling of nanoparticles of a nanofluids and uses of the nanofluid

US12617992B1US 12617992 B1US12617992 B1US 12617992B1US-12617992-B1

Abstract

A nanofluid for heat transfer that includes nanoparticles, a dielectric oil in which the nanoparticles are dispersed, and a stabilizer, wherein the nanoparticles are surface-modified by the stabilizer, a mass ratio of stabilizer to nanoparticles ranges from about 0.01 to about 110, and a molar mass of the stabilizer is less than 300 g/mol.

Inventors

  • Srikanth Birudula
  • Alexander Korobko
  • Sana Fateh

Assignees

  • Synano B.V.

Dates

Publication Date
20260505
Application Date
20250314

Claims (12)

  1. 1 . A nanofluid for heat transfer comprising: nanoparticles; a dielectric oil in which the nanoparticles are dispersed; and a stabilizer, wherein: the nanoparticles are surface-modified by the stabilizer, a mass ratio of stabilizer to nanoparticles ranges from about 0.01 to about 110, a molar mass of the stabilizer is less than 300 g/mol, and the nanoparticles are attached to an additional organic surface modifier, wherein the additional organic surface modifier is chemically bonded to the nanoparticles, wherein the additional organic surface modifier comprises a monomeric and oligomeric form of acrylic acid.
  2. 2 . The nanofluid according to claim 1 , wherein the stabilizer is attached to the nanoparticles by a chemical bond and/or the stabilizer is a surfactant physically adsorbed to the nanoparticle.
  3. 3 . The nanofluid according to claim 1 , wherein the nanoparticles are selected from the group consisting of alumina, titania, silicon dioxide, graphene, graphene oxide, carbon nanotubes, boron nitride, manganese dioxide and combinations thereof.
  4. 4 . The nanofluid according to claim 1 , wherein a concentration of the nanoparticles ranges from about 0.0001 Ma.-% to about 10% Ma.-% with respect to a total mass of the nanofluid.
  5. 5 . The nanofluid according to claim 1 , wherein the stabilizer is selected from the group consisting of glycol ethers, organic solvents comprising an OH-group, fatty alcohols, fatty acids, hydrophilic-hydrophobic molecules, and a combination thereof.
  6. 6 . The nanofluid according to claim 1 , wherein the nanoparticles are surface-modified by the stabilizer by a method comprising the steps of: (a1) mixing the nanoparticles and the stabilizer in a stabilizer to nanoparticles mass ratio ranging from about 0.01 to about 110 and wherein the stabilizer has a molecular mass of less than 300 g/mol; and (a2) evaporating excess stabilizer to obtain nanoparticles to which the stabilizer is attached; or (b1) adding the stabilizer to the dielectric oil; (b2) adding the nanoparticles to the composition of (b1) and dispersing the nanoparticles to obtain nanoparticles to which the stabilizer is attached, wherein the mass ratio of the stabilizer to the nanoparticles is between about 0.01 to about 110 and the molar mass of the stabilizer is less than 300 g/mol.
  7. 7 . The nanofluid according to claim 1 , wherein the dielectric oil is selected from the group consisting of mineral oils, paraffin oils, vegetable oils, poly-alpha-olefins (PAO), silicone oils, natural esters, synthetic esters, synthetic oils, fluorocarbon oils, and combinations thereof; and/or wherein a volume content of the dielectric oil ranges between about 30 Vol.-% to about 99 Vol.-% with respect to a total volume of the nanofluid.
  8. 8 . The nanofluid according to claim 1 , further comprising a viscosity reducing agent dispersed in the nanofluid.
  9. 9 . The nanofluid according to claim 8 , wherein the viscosity reducing agent is present in a content ranging from about 0.1 Ma.-% to about 30 Ma.-% with respect to a total mass of the nanofluid.
  10. 10 . The nanofluid according to claim 1 , wherein an average size of the nanoparticles ranges between about 1 nm and about 2000 nm.
  11. 11 . The nanofluid according to claim 1 , further comprising an antioxidant and/or a corrosion inhibitor.
  12. 12 . A method of recycling a nanofluid according to claim 1 , the method comprising the steps of: (a) destabilizing the nanoparticles dispersed in the dielectric oil; (b) extracting the destabilized nanoparticles from the dielectric oil; and (c) preparing a new nanofluid with the extracted particles in step (b).

Description

TECHNICAL FIELD The present disclosure relates to a nanofluid for heat transfer applications. In particular, the nanofluid is an oil-based nanofluid. The present disclosure also relates to a method of producing the nanofluids a well as a method of recycling nanoparticle in the nanofluid and redispersing the nanoparticles in another dielectric oil. Additionally, the present disclosure relates to various uses of the inventive nanofluid. BACKGROUND Nano dielectric oils are nanofluids containing nanoparticles of varying sizes, shapes, concentrations, and dispersed within a base dielectric oil. This approach is aimed at improving the performance of conventional oils across various high-demand applications, such as immersion cooling systems and other applications, where heat transfer and dielectric properties are critical. Advantages of nano dielectric oils are manifold. For example, they exhibit a superior thermal conductivity: Metal and metal oxide nanoparticles exhibit significantly higher thermal conductivity than base oils, which, when added to the oil, boosts the overall thermal conductivity of the nanofluid. Furthermore, heat transfer is enhanced over the dielectric oil: In low-viscosity oils, the random movement of nanoparticles contributes to heat transfer and reduces the risk of phase separation. Additionally, an increased breakdown voltage is to be expected: The presence of nanoparticles enhances the dielectric strength, making these fluids ideal for electrical applications. Furthermore, nanoparticles moving near solid surfaces break down the thermal boundary layer, facilitating more efficient heat exchange between the oil and the contact surface and finally improving interfacial heat exchange. Another advantage is that the so called Soret effect in nano dielectric oils further supports heat dissipation, particularly in applications with varying temperature zones. Despite these advantages, the development of stable nano dielectric oils involves challenges related to stability, compatibility, viscosity, and interfacial properties. As a main challenge in the art of nanofluids, achieving stable dispersions with minimal sedimentation remains challenging due to natural differences in density, structure, and polarity between nanoparticles and the dielectric oil. This can lead to aggregation and sedimentation of nanoparticles, reducing the nanofluid's effectiveness. Another challenge is the compatibility: Limited interactions between nanoparticles and oils can cause performance degradation, often necessitating surface modifications or stabilizers. Furthermore, viscosity control might be difficult: Higher nanoparticle concentrations can increase viscosity, requiring additional pumping power. Balancing thermal conductivity with manageable viscosity is essential. Moreover, an interface sensitivity is a further challenge: Effective energy transfer depends on the nanoparticle-oil interface, which can introduce thermal resistance due to limited affinity and structural differences. While nano dielectric oils have shown great potential, they remain largely under academic and small experimental development, with few patent applications filed but limited commercial adoption. Therefore, it is an objective of the present disclosure to provide improvements with respect to the above-mentioned challenges; in particular with respect to stability. SUMMARY OF THE INVENTION This disclosure is intended as only a general description and should not be interpreted as a limitation of the disclosure in any way. Moreover, this disclosure should be read and understood as it would be by one of ordinary skill in the art in the light of the entire disclosure. This disclosure describes nanofluid for heat transfer applications, methods for producing a nanofluid and for recycling of nanoparticles of nanofluids, and uses of the nanofluid. An aspect of the present disclosure is directed to a nanofluid for heat transfer includes nanoparticles; a dielectric oil in which the nanoparticles are dispersed; and a stabilizer, wherein the nanoparticles are surface-modified by the stabilizer and a mass ratio of stabilizer to nanoparticles ranges from about 0.01 to about 110 and a molar mass of the stabilizer is less than 300 g/mol. In some embodiments, the stabilizer is attached to the nanoparticles by a chemical bond and/or as a surfactant. In some embodiments, the nanoparticles are selected from the group consisting of alumina, titania, silicon dioxide, graphene, graphene oxide, carbon nanotubes, boron nitride, manganese dioxide and combinations thereof. In some embodiments, a concentration of the nanoparticles ranges from about 0.0001 Ma.-% to about 10% Ma.-% with respect to a total mass of the nanofluid. In some embodiments, the nanoparticles are attached to an additional organic surface modifier, wherein the additional organic surface modifier is chemically bond to the nanoparticles, wherein optionally the additional organic surface modifier compri