WO2016074092A1 - Fluide de transfert thermique comprenant un sel fondu et du graphène - Google Patents

Fluide de transfert thermique comprenant un sel fondu et du graphène Download PDF

Info

Publication number
WO2016074092A1
WO2016074092A1 PCT/CA2015/051180 CA2015051180W WO2016074092A1 WO 2016074092 A1 WO2016074092 A1 WO 2016074092A1 CA 2015051180 W CA2015051180 W CA 2015051180W WO 2016074092 A1 WO2016074092 A1 WO 2016074092A1
Authority
WO
WIPO (PCT)
Prior art keywords
heat transfer
transfer fluid
heat
graphene
fluid according
Prior art date
Application number
PCT/CA2015/051180
Other languages
English (en)
Inventor
Richard Boudreault
Abdelfettah BANNARI
Original Assignee
Sigma Energy Storage Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sigma Energy Storage Inc. filed Critical Sigma Energy Storage Inc.
Publication of WO2016074092A1 publication Critical patent/WO2016074092A1/fr

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
    • C09K5/08—Materials not undergoing a change of physical state when used
    • C09K5/10—Liquid materials
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
    • C09K5/08—Materials not undergoing a change of physical state when used
    • C09K5/10—Liquid materials
    • C09K5/12—Molten materials, i.e. materials solid at room temperature, e.g. metals or salts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D20/0034—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using liquid heat storage material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D20/02—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using latent heat
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D20/00—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00
    • F28D20/0034—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using liquid heat storage material
    • F28D2020/0047—Heat storage plants or apparatus in general; Regenerative heat-exchange apparatus not covered by groups F28D17/00 or F28D19/00 using liquid heat storage material using molten salts or liquid metals

Definitions

  • This invention relates to heat transfer fluids. More specifically, this invention relates to novel compositions of heat transfer fluids and methods for their use and preparation.
  • Thermal energy storage materials are well known in the art and are classified as phase change materials (PCM) and sensible heat storage materials (SHS).
  • PCMs are also known as latent heat storage materials and are capable of storing an amount of energy at least equal to the enthalpy change associated with the phase transition while maintaining a constant temperature.
  • SHS are materials in which heat exchange results in temperature change only (no phase transition).
  • PCMs have a storable energy density that is greater than that of SHS by roughly an order of magnitude.
  • the most common PCMs are water, diathermic oils and molten salts.
  • PCMs While PCMs have a high heat storage capacity at the phase transition they exhibit poor sensible heat storage efficiency outside this relatively narrow temperature range which implies the need to use large amounts in order to achieve desired heat storage capacity when not used at temperatures spanning the phase transition temperature and, consequently, the need to use very large containers for heat exchange that are not suitable for some applications as well as having a high cost.
  • PCMs such as molten salts further have the disadvantage of being in the solid state below the phase transition temperature, causing a prohibitive increase in viscosity where fluidity of the heat transfer fluid is important.
  • PCMs used for storing thermal energy can be comprised of organic or inorganic mixtures, capable of operating at different temperatures depending on the requirements of the conditions for thermal recovery. Paraffin or mixtures of different molecular weight polyethylene used as materials for PCM systems are already on the market.
  • SHS are also known and in use for various heat storage applications. However SHS, as mentioned above, are not as efficient as PCMs for storing heat.
  • Oils are frequently used as SHS heat transfer fluids but they often exhibit chemical stability problems at elevated temperatures together with relatively low heat capacities.
  • PCMs and SHS also present problems, such as viscosity, that are dependent on the environmental temperatures at which a heat exchange system operates. For example for systems used in extremely cold temperatures (below 0°C) the need to increase the temperature of the fluid before reaching phase transition temperature are typical problems of the prior art.
  • U. S. Patent no. 6,627,106 describes a ternary mixture of inorganic salts for storing thermal energy as latent heat, due to the phase transition.
  • the ternary mixture containing nitric acid salts (in particular magnesium nitrate hexahydrate, lithium nitrate and sodium or potassium nitrate) can only work at a limited temperature range between 60°C and 70°C, depending on the variations in content of the components.
  • a mixture of this type is problematic when the temperature is still below the temperature of the phase change, the mixture tending to separate into zones of different compositions, with consequent variations in fluidity/viscosity and reducing the heat storage capacity.
  • molten salt heat transfer fluids have been used for solar thermal systems
  • a binary salt mixture was used at the 10 MWe Solar Two central receiver projects in Barstow, CA. It is also be used in the indirect thermal energy storage (TES) system for the Andasol plant in Spain.
  • TES indirect thermal energy storage
  • molten salts have the highest thermal stability and the lowest cost, but also the highest melting point.
  • the binary salt referred to above is thermally stable at temperatures up to 454°C, and may be used up to 538°C for short periods, but a nitrogen cover gas is required to prevent the slow conversion of the nitrite component to nitrate.
  • improvements in the heat capacity and rate of heat conductivity for the heat transfer fluids are desirable, as are improvements in the stability of the heat transfer fluid components, both in terms of heat stability and physical stability (e.g. maintenance of dispersion of components, reduction in precipitation of components).
  • the present invention provides a heat transfer fluid comprising an organic fluid, a phase change material, and graphene.
  • the present invention provides an energy storing system comprising a heat transfer fluid as defined herein.
  • the present invention provides a method for exchanging heat energy in a heat transfer system comprising selecting a heat transfer fluid as defined herein and contacting the fluid with a heat exchange surface to allow heat to be conducted through the organic fluid to the phase change material.
  • the invention provides for the use of graphene and molten salts, optionally together with metallic particles or any other type of thermodynamically conductive solid particles, in an oil based fluid.
  • This oil-based heat transfer fluid medium is developed for heat transfer applications in a wide temperature range.
  • the fluid medium can be also water, ethylene glycol, any kind of oil or any kind of thermal fluid.
  • the present invention provides a heat transfer fluid comprising an organic fluid, graphene, and heat conductivity enhancing particles such as copper particles.
  • Figure I is a schematic representation of a heat fluid in a heat exchange system.
  • Figure 2 is a Differential Scanning Calorimetry (C p ) plot of exemplified heat exchange fluids A, B, C, D, E and F.
  • Figure 3 is a Differential Scanning Calorimetry (C p ) plot of exemplified heat exchange fluids D and F.
  • Figure 4 is a Differential Scanning Calorimetry (C p ) plot of exemplified heat exchange fluid A.
  • Figure 5 is a Differential Scanning Calorimetry (C p ) plot of exemplified heat exchange fluid B.
  • Figure 6 is a Differential Scanning Calorimetry (C p ) plot of exemplified heat exchange fluid C.
  • Figure 7 is a Differential Scanning Calorimetry (C p ) plot of exemplified heat exchange fluid D.
  • Figure 8 is a Differential Scanning Calorimetry (C p ) plot of exemplified heat exchange fluid E.
  • heat transfer fluids comprising at least one organic fluid such as an oil, at least one phase change material such as a molten salt, and graphene, which fluid exhibits advantageous heat storage capacities, heat conductivity, miscibility and/or viscosity properties.
  • the mixtures of oil, salts and graphene allow for a greater amount of heat to be transferred, transported and stored in the fluid than if it would be only comprised of oil, or for a greater heat conductivity for the fluid than if it only comprised an oil and salts.
  • the heat transfer fluid also may also provide advantageous viscosity characteristics.
  • heat transfer fluids comprising at least one organic fluid such as an oil, at least one phase change material such as a molten salt, graphene, and metallic particles, which fluid exhibits advantageous heat storage capacities. It has been discovered by the inventors that the combination of graphene and of PCMs such as salts, with organic fluids such as oils, provides mixtures that can retain the advantageous characteristics of its components while avoiding some of their
  • Heat transfer fluids of the present invention advantageously combine sensible heat storage, latent heat storage, improved heat conductivity, and viscosity characteristics enabling operation over a broad range of temperatures and with a diversity of heat exchange systems.
  • phase transitions that are similar, although not necessarily identical, to the phase transitions of the salts alone and permits the establishment of a heat capacity profile as a function of temperature that can be tailored to optimize heat storage and transfer in a variety of heat transfer systems.
  • the viscosity of the mixtures is similar, though not identical, to the viscosity of the oil(s) alone.
  • the mixtures are therefore usable at low ambient (environmental) temperatures because the viscosity of oils is low and compatible with fluid circulation in conduits in a range of temperature encompassing, in certain cases, sub-zero degree Celsius temperatures.
  • the heat transfer fluids of the invention can also be used to exchange heat in systems operating at very high
  • fluid is meant a liquid, an emulsion, a slurry, and/or a stream of solid particles that has flow characteristics similar to liquid flow.
  • heat stability is meant that a material, for example an oil, is not chemically degraded up to a predetermined or specified temperature.
  • liquidus temperature is meant the temperature at which crystals of a material (for example molten salts) can co-exist with the melt. Above the liquidus temperature the material is homogeneous and liquid. Below the liquidus temperature the material crystallizes and more and more crystals are formed up to forming a completely crystallized or solidified material (solidus temperature).
  • mass fraction is meant the mass of a particular component of a mixture divided by the mass of the total composition comprising the component.
  • an organic fluid such as an oil
  • phase change materials such as molten salts
  • the use of graphene, with or without other metallic particles boosts the thermal and electrical conductivity of the resulting thermal fluid.
  • the organic fluid which is comprised in the heat transfer fluid acts as a sensible heat storage material. Therefore as the temperature is raised the contribution of the SHS material to the total heat capacity manifests itself in a more or less linear fashion (no phase transition) although some oils may exhibit phase transitions but generally of smaller heat capacity variations than those observed for PCMs, such as salts.
  • the organic fluid component of the heat transfer fluids of the invention may consist of an oil, or two or more oils
  • the choice of the oil (or oils) is dictated by the desired physico- chemical characteristics of the heat transfer fluid obtained, which in turn are dictated by the conditions of operation of the heat transfer unit.
  • Suitable oils, or mixture of oils may consist, for example, of synthetic oils or silicone oils.
  • the synthetic oil can be selected, for example, from biphenyl, biphenyl oxide, diphenyl oxide, di and tri-aryl ethers, diphenylethane, alkylbenzenes, diaryl alkyls cyclohexanes, terphenyls and combination thereof.
  • Silicone oil which is any liquid polymerized siloxane with organic side chains, can be selected, for example, from polymethoxy phenyl siloxane, dimethyl polysiloxane and combination thereof.
  • the organic fluid is a silicone oil selected on the basis of high- temperature stability.
  • suitable silicone oils can maintain stability at temperatures up to 750°F.
  • this high-temperature stability is combined with a low end working temperature of -40°F, providing a silicone heat transfer fluid ideally suited for low-temperature applications, and a thermally stable heat transfer fluid offering precise temperature control in applications requiring the highest level of oxidative stability with high and low-temperature workability.
  • the silicone oil also provides very good surface tension behaviour, which helps to reduce or prevent the agglomeration of the graphene and other solid particles that may be present in the fluid.
  • suitable silicone oils include those that have a low viscosity and a good heat capacitance.
  • Examples of silicon oil may include the volatile
  • the oil is obtained from Hangzou Chemical Co Ltd. As RJ-255. This oil comprises a molecule of the following formula: C 6 H 5 CH j C*H 5 CH 3 C 6 H 5
  • This oil offers excellent resistance to high and low temperatures ( from about -70°C to about 300°C), it has a low volatility, it offers good heat transfer characteristics, it has a flat viscosity temperature curve, it has good compressibility characteristics, it has good oxidation and radiation resistance, and it has good miscibility with organic resins.
  • the organic fluid may be for example water, ethylene glycol, or any kind of thermal fluid known in the art. While water is not normally considered to be an organic fluid due to its lack of carbon atoms, in the context of the present application the organic fluid is understood to specifically encompass water as an embodiment.
  • Graphene is a two-dimensional (2D) material, formed of a lattice of hexagonally arranged carbon atoms. Graphene is typically referred to as a single layer of graphite. However, in the context of the present application references to graphene encompass bilayer or multilayer graphene embodiments.
  • graphene can be in all its forms such as, but not being limited to, single or multi-layer, spherical, roller or 2D sheet form.
  • Graphene also encompasses composites comprising graphene, such as graphene nano-sheet / alumina composites, or composites comprising graphene mixed with one or more ceramics.
  • the graphene may be a graphene/graphite composite consisting of thin graphene flakes bonded to bigger graphite flakes. Such composite graphene materials may provide good conductivity and heat resistance.
  • the graphene may be in the form a fully or partially oxidated graphene.
  • the graphene may be in the form of silicon-graphene composites or titanium dioxide-graphene composites.
  • the graphene may be selected to have low crystalline defects and/or activated edges.
  • Graphene with low crystalline defects may assist in imparting conductivity properties to the fluid in which it is added.
  • Graphene with activated edges may be obtained based on the method used for the preparation of the graphene.
  • Activated edges may be desirable on the graphene flakes to assist in dispersion of the graphene in certain media.
  • the graphene may be bonded at its edges with molecular groups which promote dispersion/suspension. Active edges assist in the functionalization of the graphene. Functional groups which may be present at the edges include hydroxyl, epoxy, and carbonyl.
  • graphene without activated edges may be desirable, for example to reduce chemical interactions between the graphene and the other components present in the heat transfer fluid.
  • the graphene is present in the heat transfer fluid in an mass fraction of from 1 to 10%, from 1 to 5%, from 3 to 5% or about 1 %. Larger mass fractions of graphene may also be used.
  • the graphene is present in the heat transfer fluid in the form of flakes.
  • their diameter may be, for example, from lOOnm to ⁇ , from 0.5 to 5 ⁇ , from 5 to 20 ⁇ , or about 5 ⁇ .
  • the graphene may have a thickness of 1 or more graphene layers.
  • the number of graphene layers may be, for example, from 1 to 10 layers, from 1 to 5 layers, from 6 to 10 layers, or 2 to 3 layers.
  • Thinner graphene materials such as those having 5 or less graphene layers, may preserve more thermal and electrical conductivity. Larger materials, such as those having 6 or more graphene layers, may have lesser thermal and electrical conductivities, but increased strength.
  • graphene is selected on the grounds of its physico-chemical properties, enabling superior mechanical and thermal properties. These can be obtained in several ways depending on the quality and size of material desired.
  • the presence of graphene in the heat transfer fluid may promote the eutectic nature of salt mixtures therein.
  • a eutectic phenomenon is observed - when salts having different melting temperatures are admixed, the mixture melts as a single temperature. This temperature, which can be referred to as the eutectic fusion temperature, is lower than the respective fusion temperatures of the individual salts comprised in the mixture.
  • this eutectic property is slightly lost, perhaps due to the dispersion of the salts.
  • the phase change material of the present heat transfer fluid is a molten salt.
  • molten salt is meant a salt or salt mixture which, upon heating to one or more specific temperatures, undergoes a phase change.
  • a "molten salt" as described herein is not necessarily in the liquid state, this term being used to characterise salts that have the desired phase change properties suitable for use in heat transfer fluids.
  • the molten salts can be any salt having heat transfer and heat capacity (C p ) characteristics compatible with the heat transfer system in which they are used.
  • the heat transfer fluids of the present invention comprise nitrate salts, for example nitric acid salts, nitric oxide salts, and combination thereof.
  • the nitrate salts can e.g. be selected from Ba, Be, Sr, Na, Ca, Li, K, and Mg nitrate salts.
  • the salts are selected from Mg-nitrate (Mg(N0 3 ) 2 ), -nitrate (KN0 3 ), Na- nitrate (NaN0 3 ), Li-nitrate (LiN0 3 ), Ca-nitrate (Ca(N0 3 ) 2 ), K-nitrite (KN0 2 ), Na-nitrite (NaN0 2 ), Li-nitrite (LiN0 2 ), Ca-nitrite (Ca(N0 2 ) 2 ) salts and combination thereof.
  • Nitrate may be used instead of nitrite salts for health and safety reasons.
  • the molten salt is a single salt, or a binary, ternary, or quaternary salt mixture.
  • the nitrate salts are monovalent (e.g. K-nitrate
  • KN0 3 Na-nitrate (NaN0 3 ), Li-nitrate (LiN0 3 )).
  • Nitrate salts are known in the art to be phase change materials having the ability of storing thermal energy as latent heat in applications such as concentrated solar power plants (CSP plants).
  • CSP plants concentrated solar power plants
  • the molten salts are used as a stagnant substance whereby heat is conducted and transferred to it via an oil flow circulation.
  • salts are dispersed within the thermal fluid medium to provide mobility and reduce heat losses in the process.
  • the phase change material is insoluble or substantially insoluble in the organic fluid.
  • salts are not (or only negligibly) soluble in oils. Thus below the liquidus temperature(s) (phase transition) at least a portion of the salts will exist in solid or crystallized form. These salt “particles” exist in suspension in the oil (see FIG. 1 for a schematic representation) and their size will vary with temperature, especially in relation to the phase(s) transition(s) temperature(s), and the relative proportion of the salts in the mixture.
  • the salts in the heat exchange fluid mixtures of the invention When used in a heat exchange system, the salts in the heat exchange fluid mixtures of the invention will typically be cycled between at least a partially solid state when below the phase(s) transition(s) temperature(s) and a liquid phase above that temperature(s). As the temperature is increased and approaches the liquidus (phase transition) temperature(s), the salts will start to melt and absorb large amount of heat until all salts are melted. Away from the phase transition(s) temperature(s) range, salts exhibit sensitive heat capacity characteristics which also contribute to the heat storage of the heat transfer fluid.
  • compositions that comprise more than one salt can exhibit multiple phase transition temperatures (multiple liquidus temperatures). Also it is possible that certain salt mixtures exhibit eutectic behaviour, that is to say exhibiting a single phase transition for a specific molar ratio of salts.
  • the phase transition temperatures are important to consider in the overall design of a heat exchange system. By this it is meant that because every heat exchange system will exhibit different temperature profiles (temperature distribution within the system) optimization of the heat transfer and storage will depend on the phase state of the heat transfer fluid.
  • the PCM is present in a mass fraction of 5 to 40% or from 20 to
  • the salt content in the heat transfer fluid is selected to be from 5% a 10% to avoid precipitation of the salt particles, particularly when a mechanical mixing system is not used. Lowering the salt concentration reduces the likelihood of precipitation, and the addition of graphene may permit such a reduction in the mass fraction for the salt in the heat transfer fluid without substantially jeopardizing the heat transfer characteristic of the fluid.
  • the heat transfer fluids of the invention may further comprise heat conductivity enhancing particles (HCEP) other than graphene.
  • HCEP heat conductivity enhancing particles
  • heat transfer fluids which comprise, in addition to the organic fluid, PCM and graphene, further heat conductivity enhancing particles.
  • the heat conductivity enhancing particles are selected from metals such as Au, Al, Cu, Fe and the like.
  • the particles are selected from: silver oxide (AgO), titanium oxide (Ti0 2 ), copper oxide ( ⁇ 3 ⁇ 40), aluminum oxide (AI 2 O 3 ), germanium oxide (GeO), zirconium oxide (Zr0 2 ), yttrium oxide (Y 2 O 3 ), zinc oxide (ZnO), vanadium oxide (V 2 O5), indium oxide (InO), tin oxide (SnO), a doped and/or alloyed form thereof, and combinations thereof.
  • other conducting materials can be used, such as ceramic for example.
  • the size of the HCEPs is between 1 nm to 10 mm, for example between about 0.1 ⁇ and 50 ⁇ . In some embodiments, the mass fraction of the particles in the heat transfer fluid is between about 0.1 to 20%, from 1 to 10%, or from 1 to 5%.
  • HCEPs may be necessary depending on the increase in conductivity imparted by the present of graphene in the heat transfer fluid.
  • the size and shape of the HCEPs can influence their heat conductivity and as such these characteristics can be optimized depending of the desired heat transfer properties for the fluid.
  • heat transfer fluids comprising both graphene and metallic conductivity enhancing particles have been found to provide enhanced heat transfer properties to the fluid.
  • the present invention provides a heat transfer fluid which comprises an organic fluid such as an oil, a PCM such as a salt, graphene, and a further heat conductivity enhancing particle comprising a metal such as Au, Al, Cu and Fe.
  • a heat transfer fluid which comprises an oil, one or more nitrate salts, graphene, and copper particles.
  • the mixing of the different components of a heat transfer fluid of the invention is achieved according to the following procedure:
  • the fluids are first mixed together and then the graphene (and optional further heat conducting particles) are added and mixed with the fluids.
  • the phase change materials e.g. salts
  • the PCMs are then added to fluid(s) and this final mixture is then stirred until a homogeneous texture is obtained.
  • PCMs may be dried prior to addition to the fluids if they contain water and it is determined that the presence of water might be undesired because of the nature of the fluid.
  • the PCM is a salt, it may be dried at a temperature of approximately 100°C for several hours, e.g. between 10 to 14 hours, and then allowed to cool prior to grinding.
  • the graphene and PCM e.g. molten salt
  • the speed of the stirring after dispersion can be reduced, the surface tension of the fluid preventing the agglomeration and/or sedimentation
  • Dispersion of the particles, e.g. graphene sheets, copper particles, within the fluid may also be achieved using ultrasonication.
  • the thermal behaviour of the heat transfer fluids of the invention may be complex.
  • heat cycling of the mixtures may result in hysteresis.
  • thermo storage and/or thermal energy transfer system comprising a heat transfer fluid as described herein.
  • the thermal system may utilise concentrated solar power, wind turbines, compressed air energy storage (CAES) and the like.
  • CAES compressed air energy storage
  • the heat transfer fluid of the invention advantageously provides a composition in which the heat from a medium such as compressed air can be efficiently transferred to the PCM (salts) because the dispersion of the salts within the oil increase the uniformity of the heat distribution within the fluid enabling a more rapid and uniform heat storage within the most efficient heat storing component of the fluid, namely the PCM (salt).
  • the presence of graphene, and optionally of a further heat conductivity enhancing particle increases the heat conductivity through the organic fluid to facilitate transference of the heat from the medium (such as compressed air) to the PCM.
  • thermodynamic values that characterize heat transfer fluids such as the total heat capacity within a certain temperature range (that can be obtained by integrating the area under the DSC curve in a range of temperatures: Int C p ) may be sufficient to choose an appropriate heat transfer fluid for a particular heat exchange system.
  • the heat transfer fluid would be used in a CAES system an Int Cp of between 2 and 4 x 10 3 J/g (table 23) between -50°C and 300°C irrespective of the actual relative proportion of the different components of the fluid would result in optimized heat exchange efficiency.
  • the increase in heat conductivity for the organic fluid provided by the presence of graphene may affect the design of the heat transfer unit.
  • the heat exchange apparatus may be reduced in size, as the increase in heat conductivity for the fluid may permit a smaller surface area to be used at the location where heat is transferred from the media (e.g. compressed air) to the heat transfer fluid.
  • V ⁇ P m V ⁇ P m
  • ⁇ 8 the volume fraction of particles.
  • Two key factors influence the viscosity of the suspension at a given volume fraction of the additives: the viscosity of the organic fluid (oil) without additives, and the intrinsic viscosity of the additives (salts, graphene, optional HCEPs).
  • the volume fraction of the graphene, salts and HCEP's should be less than approximately 60%.
  • the density can be calculated by adding the density of each component weighed by its volume fraction in the composition. Alternatively the density can be measured experimentally.
  • a method for storing heat energy whereby a heat is stored primarily in a PCM comprising suspending a PCM in an organic fluid such as oil, the organic fluid comprising graphene, to provide a heat transfer fluid, contacting the fluid with a surface heated by a medium from which heat is to be transferred, such that heat is conducted through the oil, aided by the graphene, to the PCM for storage.
  • the phase change material, graphene, and any heat conducting particles can be stable in suspension for a sufficiently long period to be used without an agitator or circulation.
  • particle sizes from about 0.1 ⁇ to about 10 pm in the organic fluids mentioned above can remain in suspension for more than a week without settling or separation.
  • the tolerable particle size and the time that the system remains in suspension can depend on the organic fluid's viscosity and other properties.
  • the heat conducting particles for example copper, can separate and be re-homogenized into the fluid with more difficulty than some salts.
  • the ability of an organic fluid to retain solid particles in suspension will be related to the surface tension at the solid parti cle/organic fluid interface and the size of the particles to be kept in suspension.
  • salt particles and copper particles could be maintained in suspension when the fluid is an oil.
  • there was no guidance in this reference or in the prior art regarding the ability of other solid particles to be retained in suspension while not negatively affecting the suspension of salts and/or copper particles.
  • the particle size is greater than 10 ⁇ , it has been found that the settling time is sufficiently short that agitation can be required to maintain the suspension.
  • the fluid can be very useful up to particle sizes of about 25 ⁇ , after which the agitation effort can become challenging.
  • the heat storage system includes a circulation pump, stirring device or the like within or in association with the storage vessel or storage vessels for the heat transfer fluid.
  • a circulation pump, stirring device or the like within or in association with the storage vessel or storage vessels for the heat transfer fluid.
  • These can maintain the phase change material, graphene, and any heat conducting particles in suspension for any length of time, and can also allow larger particle sizes, for example from about 10 ⁇ to about 25 ⁇ to be used, even if particle sizes between about 0.1 ⁇ to about 10 ⁇ may be chosen to have improved suspension stability in the absence of agitation.
  • a surfactant may be added to the fluid to assist in dispersion of certain heat conductivity enhancing particles such as copper, or to assist in maintaining these particles in suspension.
  • suitable surfactants may include, for example, sodium dodecyl sulfate (SDS), Salt and oleic acid, dodecyltrimethylammonium bromide (DTAB), hexadecyltrimethylammonium bromide (HCTAB), polyvinylpyrrolidone (PVP), and Gum Arabic.
  • the surfactant may be added in an amount of about 0.1 wt% based on the weight of heat conductivity enhancing particles such as copper.
  • Thermal conductivity of a two component heterogeneous mixture is a function of the conductivity of the pure materials, the composition of the mixture and the manner in which pure materials are distributed throughout the mixture.
  • Kp and Ko are the conductivities of the particle material and the base fluid and ⁇ is volume fraction of nanoparticles.
  • the heat transfer enhancement due to the Brownian motion can be estimated from the known fluid temperature and size of the particles contained.
  • the increase of the thermal conductivity due to the rotational motion of a spherical particle can be estimated as:
  • Peclet number Pe f (r 2 Vp C pf / k f ), where r is the radius of particle, Vp is the velocity gradient calculated from the mean Brownian motion velocity and the average distance between particles, k f is the base liquid density, and C pf is the specific heat of base liquid.
  • Gupte et al. Role of Micro-Convection Due to Non-Affme Motion of Particles in a Mono-Disperse Suspension; Int. J. Heat Mass Transfer, Vol. 38, No. 16, pp. 2945-2958, 1995
  • the base liquid and particles were assumed to have identical thermal conductivity, density, and heat capacity. Their results are fitted with the following fourth- order polynomial:
  • the graphene component is in the form of a powder comprising flakes of a graphite/graphene composite, available from NanoXplore as heXog-g -E.
  • This product is obtained by a mechano-electro-chemical exfoliation of natural flake graphite, and it has a purity of 96% by weight, an average specific surface area of from 7-9 m 2 /g, an average sheet diameter or from 5 to 20 um graphene sheets mixed with large natural graphite flakes.
  • This product also has a C content of about 96%, impurities in an amount of less than 2 by wt%, and an IG/ID ratio of 20, indicating a low defect density (calculated from Raman Spectroscopy G and D peaks).
  • the ratio of the intensity of D- Raman peak and G- Raman peak (ID/IG) is often used for characterization of diamond-like carbon films, for example to estimate number and size of the sp2 clusters.
  • the heat transfer fluids of the invention comprising an organic fluid, a molten salt and graphene, possess the following physico-chemical characteristics: a dynamic viscosity between about 1.0 centipoise (cP) and 200 cP at temperatures from about -40°C to about 400°C, a heat stability greater than about 200°C with the heat stability reaching 400 to 700 °C with certain compositions.
  • a dispersion of copper in oil was prepared by the following method:
  • Table 2 provides examples of ranges for the different components of a heat transfer fluid composition of the invention.
  • Table 3 provides examples of ranges for certain salts, and table 4 provides a specific example of a mixture of salts (mixture Ml).
  • Tables 5 to 10 provide examples of specific heat transfer fluid compositions (heat transfer fluid A, B, C, D, and E)
  • the temperature sweep differential scanning calorimetry curves were prepared as follows. First, the sample (6 grams in the examples) was thermally stabilized at 20°C for 10 minutes. Temperature was then increased at a rate of 10°C per minute from 20 to 300°C, at which point the sample was allowed to thermally stabilize for 2 minutes. Temperature was then decreased at a rate of 10°C per minute from 300°C to 20°C, to complete a full cycle. The duration of one cycle of Cp measurement by way of this temperature sweep differential scanning calorimetry was thus 70 minutes in total.
  • FIGs 2 to 8 Differential scanning calorimetry curves for compositions A-F are provided in Figures 2 to 8.
  • Figure 2 there are provided overlapping DSC plots for composition A (205), composition B (204), composition C (201), composition D (203), composition E (202), and composition F 206).
  • Figure 3 provides differential scanning calorimetry curves for compositions D (301) and F (302).
  • Figures 4-8 provide DSC curves for compositions A-E, respectively.
  • the total heat capacity Cp of the heat transfer fluids of the invention over a range of temperature is the combination of the sensible heat capacity and the phase change enthalpy. Different compositions will exhibit different total Cp furthermore the cumulative Cp as a function of temperature also varies as a function of the composition of the mixtures as can be seen from the DSC curves.
  • Table 11 provides integrated values of Cp over the range of temperatures used for obtaining the DSC curves for compositions A-E (area under the curve for Figures 3-8). As the DSC measurements were not made under equilibrium conditions, these values do not reflect the exact heat capacity of the exemplified fluids. However, comparison of the integrated values qualifies the relative heat capacity and heat conductivity of each composition.
  • samples of the fluids identified above were allowed to rest without agitation for 24 hours. After this period of rest, it was visually observed that samples with copper particles had formed a precipitate. For samples with graphene and no copper, no precipitation was observed after 24 hours.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion & Propulsion (AREA)
  • Thermal Sciences (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Lubricants (AREA)

Abstract

Cette invention concerne des fluides de transfert thermique comprenant un fluide organique tel qu'une huile, un matériau à changement de phase tel qu'un sel fondu, et du graphène, ledit fluide présentant des capacités de stockage de chaleur, des propriétés de conductivité thermique, et de viscosité avantageuses. Ces fluides peuvent être utilisés dans les systèmes où des fluides de transfert thermique sont souhaitables, tels que des systèmes de stockage d'énergie par air comprimé.
PCT/CA2015/051180 2014-11-11 2015-11-12 Fluide de transfert thermique comprenant un sel fondu et du graphène WO2016074092A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201462078079P 2014-11-11 2014-11-11
US62/078,079 2014-11-11

Publications (1)

Publication Number Publication Date
WO2016074092A1 true WO2016074092A1 (fr) 2016-05-19

Family

ID=55953510

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CA2015/051180 WO2016074092A1 (fr) 2014-11-11 2015-11-12 Fluide de transfert thermique comprenant un sel fondu et du graphène

Country Status (1)

Country Link
WO (1) WO2016074092A1 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108003845A (zh) * 2017-12-08 2018-05-08 中国科学院青海盐湖研究所 一种三元硝酸熔盐及其制备方法
CN108467712A (zh) * 2018-03-09 2018-08-31 北京理工大学 一种熔盐储热材料
DE102017008115A1 (de) * 2017-08-26 2019-02-28 Hans-Jürgen Maaß Speicherung thermischer Energie mit Phasenwechselmaterial
CN110127689A (zh) * 2019-05-05 2019-08-16 陈让珠 硅油相石墨烯的制作方法
CN110449101A (zh) * 2018-05-07 2019-11-15 中国石油化工股份有限公司 基于离子液体相变撤热抑制失控反应的反应器及其应用
CN110746941A (zh) * 2019-12-11 2020-02-04 北京交通大学 一种新型的定形导热增强型复合相变储能材料及其制备方法
CN110914214A (zh) * 2017-07-12 2020-03-24 欧盟委员会 热能储存系统的生产
US10914293B2 (en) 2018-06-20 2021-02-09 David Alan McBay Method, system and apparatus for extracting heat energy from geothermal briny fluid
WO2022236178A1 (fr) * 2021-05-07 2022-11-10 Cratus Llc Système et milieu de stockage d'énergie thermique améliorés

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH616119A5 (en) * 1975-08-26 1980-03-14 Kuper Heinrich Fa Apparatus for the packaging of articles in foil
CN102634212A (zh) * 2012-04-23 2012-08-15 钱新明 一种导热硅脂组合物
WO2013087949A1 (fr) * 2011-12-13 2013-06-20 Ingeteam Power Technology, S.A. Système hybride de génération d'électricité à partir d'énergie solaire et de biomasse
US20140084205A1 (en) * 2012-09-26 2014-03-27 Dileep Singh Nanoparticles for heat transfer and thermal energy storage
CN104087254A (zh) * 2014-07-29 2014-10-08 江苏启能新能源材料有限公司 一种高导热无机相变储能材料

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH616119A5 (en) * 1975-08-26 1980-03-14 Kuper Heinrich Fa Apparatus for the packaging of articles in foil
WO2013087949A1 (fr) * 2011-12-13 2013-06-20 Ingeteam Power Technology, S.A. Système hybride de génération d'électricité à partir d'énergie solaire et de biomasse
CN102634212A (zh) * 2012-04-23 2012-08-15 钱新明 一种导热硅脂组合物
US20140084205A1 (en) * 2012-09-26 2014-03-27 Dileep Singh Nanoparticles for heat transfer and thermal energy storage
CN104087254A (zh) * 2014-07-29 2014-10-08 江苏启能新能源材料有限公司 一种高导热无机相变储能材料

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110914214A (zh) * 2017-07-12 2020-03-24 欧盟委员会 热能储存系统的生产
DE102017008115A1 (de) * 2017-08-26 2019-02-28 Hans-Jürgen Maaß Speicherung thermischer Energie mit Phasenwechselmaterial
CN108003845A (zh) * 2017-12-08 2018-05-08 中国科学院青海盐湖研究所 一种三元硝酸熔盐及其制备方法
CN108467712A (zh) * 2018-03-09 2018-08-31 北京理工大学 一种熔盐储热材料
CN110449101B (zh) * 2018-05-07 2021-10-15 中国石油化工股份有限公司 基于离子液体相变撤热抑制失控反应的反应器及其应用
CN110449101A (zh) * 2018-05-07 2019-11-15 中国石油化工股份有限公司 基于离子液体相变撤热抑制失控反应的反应器及其应用
US10914293B2 (en) 2018-06-20 2021-02-09 David Alan McBay Method, system and apparatus for extracting heat energy from geothermal briny fluid
US11225951B2 (en) 2018-06-20 2022-01-18 David Alan McBay Method, system and apparatus for extracting heat energy from geothermal briny fluid
US11692530B2 (en) 2018-06-20 2023-07-04 David Alan McBay Method, system and apparatus for extracting heat energy from geothermal briny fluid
CN110127689A (zh) * 2019-05-05 2019-08-16 陈让珠 硅油相石墨烯的制作方法
CN110746941A (zh) * 2019-12-11 2020-02-04 北京交通大学 一种新型的定形导热增强型复合相变储能材料及其制备方法
CN110746941B (zh) * 2019-12-11 2020-09-08 北京交通大学 一种定形导热增强型复合相变储能材料及其制备方法
WO2022236178A1 (fr) * 2021-05-07 2022-11-10 Cratus Llc Système et milieu de stockage d'énergie thermique améliorés

Similar Documents

Publication Publication Date Title
WO2016074092A1 (fr) Fluide de transfert thermique comprenant un sel fondu et du graphène
Bahiraei et al. Experimental and numerical investigation on the performance of carbon-based nanoenhanced phase change materials for thermal management applications
Akilu et al. Properties of glycerol and ethylene glycol mixture based SiO2-CuO/C hybrid nanofluid for enhanced solar energy transport
He et al. Preparation, thermal characterization and examination of phase change materials (PCMs) enhanced by carbon-based nanoparticles for solar thermal energy storage
Vivekananthan et al. Characterisation and thermophysical properties of graphene nanoparticles dispersed erythritol PCM for medium temperature thermal energy storage applications
Motahar et al. A novel phase change material containing mesoporous silica nanoparticles for thermal storage: a study on thermal conductivity and viscosity
Liu et al. Study on the supercooling degree and nucleation behavior of water-based graphene oxide nanofluids PCM
Li A nano-graphite/paraffin phase change material with high thermal conductivity
Liu et al. Thermal properties and enhanced thermal conductivity of capric acid/diatomite/carbon nanotube composites as form-stable phase change materials for thermal energy storage
Putra et al. Characterization of the thermal stability of RT 22 HC/graphene using a thermal cycle method based on thermoelectric methods
Anand et al. Cycle test stability and corrosion evaluation of phase change materials used in thermal energy storage systems
Saydam et al. Dispersing different nanoparticles in paraffin wax as enhanced phase change materials: A study on the stability issue
Elarem et al. Experimental investigations on thermophysical properties of nano-enhanced phase change materials for thermal energy storage applications
US20190161665A1 (en) Heat transfer fluids compositions
Aljaerani et al. Thermo-physical properties and corrosivity improvement of molten salts by use of nanoparticles for concentrated solar power applications: A critical review
Sivasamy et al. Preparation and thermal characteristics of caprylic acid based composite as phase change material for thermal energy storage
Salyan et al. Liquid metal gallium laden organic phase change material for energy storage: an experimental study
Barthwal et al. Effect of nanomaterial inclusion in phase change materials for improving the thermal performance of heat storage: A review
Li et al. Thermal conductivity enhancement and shape stabilization of phase-change materials using three-dimensional graphene and graphene powder
Zhang et al. Enhanced thermal properties of Li 2 CO 3–Na 2 CO 3–K 2 CO 3 nanofluids with nanoalumina for heat transfer in high-temperature CSP systems
Xiao et al. Molten salt/metal foam/graphene nanoparticle phase change composites for thermal energy storage
Parameshwaran et al. Study on thermal storage properties of hybrid nanocomposite-dibasic ester as phase change material
Amin et al. Thermal properties of paraffin based nano-phase change material as thermal energy storage
Ristić et al. IEA SHC Task 42/ECES Annex 29 WG A1: Engineering and processing of PCMs, TCMs and sorption materials
Li et al. Preparation and thermal characterization of nitrates/expanded graphite composite phase-change material for thermal energy storage

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 15858183

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 15858183

Country of ref document: EP

Kind code of ref document: A1