Thermal fluid comprising particles of at least one caloric material

Abstract

The present invention relates to a thermal fluid comprising solid particles of at least one caloric material having a solid-solid phase transition under the effect of at least one external physical field, preferably a magnetic, electrical and / or mechanical field. The present invention also relates to the use of the fluid as a heat transfer fluid, preferably in thermodynamic systems or applications that involve a transfer of heat. The invention also relates to a composition comprising the thermal fluid as defined previously. The invention also relates to a thermal system comprising at least one composition, at least one hot-source heat exchanger, at least one cold-source heat exchanger and at least one device that is able to apply at least one physical field, preferably a magnetic, electrical and / or mechanical field, capable of causing a solid-solid phase transition within the caloric material.

Description

[0001] DESCRIPTION

[0002] TITLE: Thermal fluid comprising particles of at least one caloric material

[0003] The present invention relates to a thermal fluid comprising solid particles of at least one caloric material having a solid-solid phase transition under the effect of at least one external physical field, preferably magnetic, electrical and / or mechanical.

[0004] The invention also relates to a composition comprising at least one thermal fluid as defined previously.

[0005] The invention also relates to the use of the composition, as defined below, as a heat transfer fluid, preferably in thermodynamic systems or applications involving heat transfer.

[0006] The invention also relates to a thermal system comprising at least one composition as defined below, or a fluid as defined below, at least one hot source heat exchanger, at least one cold source heat exchanger and at least one device capable of applying at least one physical field, preferably magnetic, electrical and / or mechanical, capable of causing a solid-solid phase transition within the calorific material.

[0007] The present invention also relates to a heat transfer method comprising circulating a composition, as described below, or a fluid as described below, and applying at least one external physical field capable of causing a solid-solid phase transition within the calorific material of the composition.

[0008] Heat transfers are generally at the heart of many industrial and residential systems intended for various applications involving the generation of heat or cold.

[0009] The majority of these systems operate primarily on heat exchanges that occur during the liquid-vapor state changes of a refrigerant, also called the working fluid, subjected to compression and expansion cycles.

[0010] For example, in a cycle within a refrigeration system, the working fluid in vapor phase is first compressed by a compressor and then liquefies, at constant temperature and pressure, in a condenser. During the vapor-liquid state change in the condenser, the refrigerant gives off heat to the external environment because its entropy decreases. Once the state change has taken place, the refrigerant in liquid form is directed to an expansion valve in which its pressure is reduced and then is conveyed to an evaporator to be vaporized. During the liquid-vapor state change in the evaporator, the refrigerant receives heat from the environment to be cooled because its entropy increases. The refrigerant is finally returned to the compressor to begin a new cycle of condensation and evaporation.Thus, during a refrigeration cycle, the working fluid vaporizes in the evaporator by absorbing the thermal energy provided by the heat of the medium to be cooled, for example the enclosure of a refrigerator. This thermal energy is then evacuated to the outside environment during the circulation of the fluid in the condenser.

[0011] Refrigeration systems, particularly used in the medical, electronics and food industries, as well as air conditioning systems in the transport sector, are generally based on this type of technology.

[0012] Similarly, heating systems, such as those using heat pumps, operate on the same principle of heat exchange occurring during successive cycles of evaporation and condensation of a refrigerant fluid passing from the liquid state to the vapor state.

[0013] However, such technology has a number of drawbacks, particularly related to the risks and compliance with quality, health, safety and environmental standards for refrigerants, which require particularly controlled use. Indeed, such fluids can be harmful to health, carry risks of ignition and contribute to global warming.

[0014] Furthermore, thermal systems based on this type of technology consume a large amount of energy. In other words, the overall energy efficiency of this type of system is not satisfactory at present.

[0015] In order to address the issues raised, particularly in light of the growing environmental and energy challenges, alternative heat transfer solutions have been developed, notably based on phase transitions from one solid state to another solid state of a caloric material which are caused by the action of a specific external physical field, for example a magnetic field, an electric field or a mechanical stress such as a pressure stress. In other words, thermal systems exploiting the caloric effects occurring during thermodynamic change within a material under the effect of a magnetic or electric field, or even a mechanical stress, such as a pressure stress, have been developed in order to compete with current thermal systems based on successive cycles of evaporation and condensation of a working fluid.

[0016] Such solid caloric materials can then correspond to magnetocaloric, electrocaloric or mechanocaloric materials which comprise several solid phases.

[0017] The caloric effects of such materials are notably reversible when the induced external physical field is removed.

[0018] Among them, barocaloric materials, i.e. materials undergoing solid-solid phase transitions under the effect of pressure stress, have recently attracted considerable interest because the caloric effects obtained can be significant in relation to the applied pressure stresses which are relatively low and easier to control than a magnetic or electric field.

[0019] As an illustration, recent studies have highlighted that neopentyl glycol crystals have the ability to deform, particularly from a disordered crystalline phase to an ordered phase, under the action of a relatively low pressure stress and to return to their original shape when this stress is removed while yielding or absorbing heat during these solid-solid phase changes. These crystals have a so-called "plastic" structure and exhibit cooling performances likely to be equivalent to that of a standard refrigerant.

[0020] However, one of the technical difficulties of these alternative solutions lies in the unilateral, continuous or semi-continuous heat transfer from the cold source to the hot source of the system in order to achieve an effective transfer of energy.

[0021] Indeed, the application of an external physical field causes a decrease in entropy, for example a decrease in the entropy of the dipoles in the case of an electric field or the obtaining of an ordered crystalline phase in the case of a pressure constraint, within the caloric material which causes a transfer of heat towards the cold source. Alternatively, when the external physical field is removed, the entropy of the material increases, for example the orientation of the dipoles becomes more and more random in the case of the removal of an electric field or the return to a more disordered crystalline phase in the case of the removal of a pressure constraint, which causes heating and therefore a transfer of heat from the outside to the material.

[0022] Thus, one of the technical difficulties of this solution lies in minimizing the back and forth between the material and the cold source during the alternation of the applied physical field and in ensuring that the material absorbs energy in a cold source in such a way as to create an effective transfer of energy from the latter to the hot source.

[0023] To achieve this, the solutions currently proposed consist of implementing a thermal enclosure with the calorific material in the solid state associated with a system of thermal diodes to ensure unidirectional thermal transfer of heat. Such thermal diodes can, for example, take the form of micro-channels or pressurized fluid exchangers.

[0024] More generally, the fact that the caloric material represents a static caloric solution requires the implementation of complex and expensive heat drainage systems, the effectiveness of which may be limited.

[0025] Furthermore, it has been observed that caloric materials, especially barocaloric materials, are likely to exhibit a significant temperature hysteresis loop, making their use in an industrial system problematic. This means that, in the case of a barocaloric material, the structural deformation evolution curve upon removal of the pressure stress does not follow the same path as that followed upon application of the pressure stress.

[0026] In view of the above, one of the objectives of the present invention is to overcome the drawbacks mentioned above, in particular to achieve effective heat transfer between the calorific material and the cold and hot sources of the thermal system in order to obtain performances equivalent to current thermal systems while minimizing negative impacts on the environment and health.

[0027] In other words, there is a real need to propose a solution capable of promoting the heat transfer between the hot source and the cold source of a thermal system so as to obtain an efficient thermal system, in particular in terms of energy performance and efficiency, while remaining viable from an ecological and health point of view. In particular, one of the objectives of the present invention is to improve current technical solutions or applications based on heat transfers occurring during phase transitions from one solid state to another solid state of a caloric material caused by the action of a specific external physical field.

[0028] The present invention therefore relates in particular to a thermal fluid comprising solid particles of at least one caloric material having a variation in absolute value of the entropy AS greater than or equal to 100 J. K 1 . kg 1, under the action of at least one external physical field, the content of which varies from 2 to 98% by weight, relative to the total weight of the fluid.

[0029] The fluid according to the invention makes it possible to effectively promote the transfer of heat between the hot source and the cold source of a thermal system, thus giving it performance equivalent to current thermal systems while minimizing negative impacts on the environment and health.

[0030] In particular, the application of at least one physical field, preferably a magnetic, electrical and / or mechanical field, makes it possible to activate the solid-solid phase transition of the particles of at least one caloric material, as defined above, immersed in the fluid, thus causing a heat exchange within the fluid. This results in a conduction of heat between the particles of the caloric material, the fluid and the hot and cold sources of the thermal system, thus achieving a work cycle.

[0031] The fluid according to the invention has the particular advantage of being able to transport the calorific material in the form of solid particles immersed in a fluid, which makes it possible to move the place where the material takes up heat and that where it evacuates it and to improve heat transfers.

[0032] The fluid according to the invention therefore allows the calorific material not to be fixed or static in a thermodynamic system or application involving heat transfer but to move in the form of a flowing fluid.

[0033] The fluid according to the invention therefore has the advantage of minimizing the back and forth movements between the material and the cold source during an alternation of the applied physical field.

[0034] Thus, the fluid according to the invention makes it possible to effectively take advantage of the caloric effects, in particular magnetocaloric, electrocaloric and / or mechanocaloric of a material, while minimizing the heat transfer losses likely to occur in a thermodynamic system involving heat transfer. In addition, the fluid according to the invention makes it possible to minimize the hysteresis phenomena previously observed in thermal systems using a caloric material, in particular barocaloric, which is static, i.e. which does not move between the hot source and the cold source of the system.

[0035] In other words, the invention makes it possible to implement a caloric material in the form of particles in a fluid in order to generate an improved heat transfer between the hot source and the cold source of the thermal system. In this way, the fluid makes it possible to transport heat between several temperature sources, which means that it is possible to dispense with the installation of devices intended to drain the heat from the caloric material.

[0036] The present invention also relates to the use of the fluid, as defined above, as a heat transfer fluid, in particular in thermodynamic systems involving heat transfer.

[0037] The present invention also relates to a composition comprising at least one fluid as defined previously.

[0038] In other words, the composition according to the invention comprises at least one thermal fluid mixed with solid particles of at least one caloric material having a variation in absolute value of the entropy AS greater than or equal to 100 J. K 1 .kg 1 , under the action of at least one external physical field, and whose content varies from 2 to 98% by weight, relative to the total weight of the fluid

[0039] The invention also relates to the use of the composition, as defined above, for transferring heat, in particular in thermodynamic systems involving heat transfer.

[0040] Likewise, the present invention also relates to a thermal system comprising at least one composition, as described previously, or a fluid, as defined previously, at least one hot source heat exchanger, at least one cold source heat exchanger, and at least one device for applying at least one physical field capable of causing a variation in the entropy AS greater than or equal to 100 JK^.kg 1 within the caloric material of said fluid.

[0041] The thermal system according to the invention has particularly advantageous energy performance.

[0042] Another object of the present invention further consists in proposing a heat transfer method comprising at least the circulation of a composition, as defined previously, or of a fluid, as defined previously, between at least one hot source heat exchanger and at least one cold source heat exchanger, and at least the application of a physical field to cause a variation in the absolute value of the entropy AS greater than or equal to 100 J. K 1 .kg 1 within the caloric material of said fluid.

[0043] Such a method is particularly advantageous because it allows heat transfer to be carried out without requiring the implementation of a heat drainage system towards the system's temperature sources.

[0044] Other characteristics and advantages of the invention will appear more clearly on reading the description and examples which follow.

[0045] In what follows, and unless otherwise indicated, the limits of a domain of values ​​are included in this domain.

[0046] The expression "at least one" is equivalent to the expression "one or more".

[0047] Fluid

[0048] As indicated above, the thermal fluid comprises solid particles of at least one caloric material having a variation in absolute value of the entropy AS greater than or equal to 100 J. K 1 .kg 1 , under the action of at least one external physical field, the content of which varies from 2 to 98% by weight, relative to the total weight of the fluid.

[0049] For the purposes of the present invention, the external physical field corresponds to an external stress applied at a level sufficient to induce a solid-solid phase transition within the caloric material, for example a change in orientation of dipoles upon application of an electric field or a structural change, passing from a disordered crystalline phase to an ordered crystalline phase, upon application of a pressure stress or a magnetic field.

[0050] In accordance with the present invention, several external stresses of different nature can be applied to cause a solid-solid phase transition within the caloric material.

[0051] For the purposes of the present invention, the solid-solid phase transition within the caloric material results in a variation in the absolute value of the entropy AS of the material to a value greater than or equal to 100 JK^.kg 1 .

[0052] The variation of AS entropy can be measured using a calorimeter capable of applying a stress field inside the test cell. Barocaloric effects are for example evaluated in a pressure field calorimeter in a cell capable of rising to a pressure of at least 3 kbar (or 3.10 8 Pa).

[0053] Electrocaloric effects are, for example, evaluated in an electric field calorimeter.

[0054] Magnetocaloric effects are, for example, evaluated in a magnetic field calorimeter.

[0055] Thermal sensors are used to measure heat exchanges in the calorimetric cell when the stress field is applied. The temperature in the cell is controlled by a heating bath external to the cell. The calorimetric measurements provide a dQ / dT value for each temperature. The integration of the dQ / dT and 1 / T.dQ / dT values ​​allows the determination of the enthalpies and entropies respectively of the solid / solid phase transition generated by the application of the stress field in the measuring cell.

[0056] The variation in absolute value of the entropy AS of the caloric material can also be greater than or equal to 200 J. K 1 .kg 1 , preferably greater than or equal to 300 J. K 1 . kg 1 .

[0057] Preferably, the variation in absolute value of the entropy AS of the caloric material can range from 100 JK^.kg 1 at 1000 J. K 1 .kg 1, more preferably 200 J. K 1 .kg 1 at 800 J. K 1 .kg 1 , more preferably 300 J. K 1 .kg 1 at 700 J. K 1 .kg 1 .

[0058] Preferably, the variation in absolute value of the entropy AS of the caloric material occurs at a temperature ranging from 231 K to 420 K, preferably from 233 K to 400 K, and more preferably from 273 K to 320 K.

[0059] The external physical field is preferably applied at a temperature as defined previously.

[0060] Preferably, the external physical field may be an electric field, a magnetic field and / or a mechanical stress.

[0061] Thus the caloric material present in the composition according to the invention may be a magnetocaloric, electrocaloric and / or mechanocaloric material.

[0062] Mechanical stress can correspond to the application of a tension, which is particularly the case for materials with entropic elasticity, or to a stress induced by a change in pressure.

[0063] The physical field is more particularly a mechanical constraint. In other words, the physical field is in particular a field of mechanical constraints. Preferably, the mechanical constraint is a pressure constraint, that is to say a pressure field inducing a solid-solid phase transition within the caloric material.

[0064] In the case of a mechanocaloric material, the material can be elastocaloric or barocaloric, preferably barocaloric.

[0065] Preferably, the external physical field is an electric field and / or a pressure stress (or a pressure stress field), more preferably a pressure stress.

[0066] Thus the caloric material present in the fluid can be an electrocaloric and / or barocaloric material, preferably barocaloric.

[0067] Preferably, the fluid comprises solid particles of at least one barocaloric material having a variation in absolute value of the entropy AS greater than or equal to 100 J. K 1 .kg 1 , under the action of a pressure constraint, the content of which varies from 2 to 98% by weight, relative to the total weight of the fluid.

[0068] Preferably, the fluid comprises solid particles of at least one barocaloric material having a variation in absolute value of the entropy AS greater than or equal to 100 J. K 1 .kg 1, under the action of a pressure constraint, the content of which varies from 10 to 90% by weight, preferably in a content of 20 to 80% by weight, more preferably from 30 to 70% by weight, and even more preferably from 40 to 60% by weight, relative to the total weight of the fluid.

[0069] Furthermore, the caloric material may be in particular insoluble in the fluid of the composition according to the invention.

[0070] The calorific material can be organic, inorganic, or a hybrid organic-inorganic material.

[0071] The calorific material may be chosen from the group consisting of plastic crystals, in particular plastic crystals derived from neopentane comprising amine functions, hydroxyl functions and mixtures thereof, in particular neopentyl glycol, 2-amino-2-(hydroxymethyl)propane-1,3-diol, 2-amino-2-methyl-1,3-propanediol, 2-hydroxymethyl-2-methyl-1,3-propanediol, 2,2-dimethyl-1-propanol; salts such as ferroelectric salts, ammonium salts, in particular ammonium iodide, ammonium sulfate;organic-inorganic hybrid compounds such as organic perovskites, intermetallic compounds (e.g. based on transition metals such as iron, copper, cobalt, titanium, nickel, zirconium, manganese, rhodium, based on poor metals such as aluminum, zinc, lead, based on metalloids such as germanium, silicon, boron, based on alkaline earth metals such as magnesium, barium, based on lanthanides such as lanthanum, cerium, gadolinium).;

[0072] Preferably, the barocaloric material is organic.

[0073] For example, the barocaloric material may be selected from the group consisting of an alkylcarboxylic acid, an alkyl carboxylate salt, in particular barium or calcium salts of alkyl carboxylate, a liquid crystal, for example 4-(trans-4-pentylcyclohexyl) benzonitrile (PCH5), a plastic crystal, in particular neopentyl glycol (NPG) or 1-adamantanol, 2-amino-2-(hydroxymethyl)propane-1,3-diol, ammonium sulfate salts, and mixtures thereof.

[0074] Preferably, the barocaloric material is a plastic crystal, particularly neopentyl glycol or 1-adamantanol, more particularly neopentyl glycol.

[0075] The calorific material in the form of particles is present in a content ranging from 2 to 98% by weight, relative to the total weight of the fluid.

[0076] The calorific material in the form of particles is present in a content preferably greater than or equal to 10% by weight, preferably greater than or equal to 15% by weight, preferably greater than or equal to 20% by weight, preferably greater than or equal to 25% by weight, preferably greater than or equal to 30% by weight, preferably greater than or equal to 35% by weight, preferably greater than or equal to 40% by weight, preferably greater than or equal to 45% by weight, preferably greater than or equal to 50% by weight, relative to the total weight of the fluid.

[0077] The calorific material in the form of particles is present in a content preferably less than or equal to 90%, preferably less than or equal to 85% by weight, more preferably less than or equal to 70% by weight, even more preferably less than or equal to 60% by weight, relative to the total weight of the fluid.

[0078] Preferably, the calorific material in the form of particles is present in a content varying from 2 to 90% by weight, from 2 to 85% by weight, from 2 to 70% by weight, from 2 to 60% by weight, relative to the total weight of the fluid.

[0079] Preferably, the calorific material in the form of particles is present in a content varying from 10 to 90% by weight, preferably in a content varying from 20 to 80% by weight, more preferably in a content varying from 30 to 70% by weight, even more preferably in a content varying from 40 to 60% by weight, relative to the total weight of the fluid. Preferably, the calorific material in the form of particles is present in a content ranging from 40 to 95% by weight, more preferably in a content ranging from 50 to 90% by weight, relative to the total weight of the fluid.

[0080] Preferably, the particles of the calorific material have an average size ranging from 0.1 to 1000 pm, preferably an average size ranging from 1 to 500 pm.

[0081] For the purposes of the present invention, "particle size" means the maximum dimension that can be measured between two diametrically opposite points of an individual particle.

[0082] The size can be determined, for example, by transmission electron microscopy or from the measurement of the specific surface area by the BET method or by means of a laser granulometer.

[0083] The average particle size is preferably a number average size.

[0084] The fluid may be a heat transfer fluid, preferably liquid at a temperature of 23°C.

[0085] Preferably, the fluid is selected from the group consisting of alcohols, oils, polar solvents and their mixtures.

[0086] As examples, the fluid may be chosen from the group consisting of water, alkanes, alkenes, alcohols, ethers, esters, amines, amides, sulfoxides, fluoroalkanes, perfluoroalkanes, chloroalkanes, siloxanes.

[0087] Preferably, the fluid may be selected from the group consisting of hexane, ethanol, toluene, propanone, di-n-propyl ether, tetrahydrofuran, 1-butanol, butanamide, pyrrolidine, dimethyl sulfoxide, 1-fluoropentane, water and polydimethylsiloxane and mixtures thereof.

[0088] Preferably, the fluid is selected from the group consisting of alcohols, oils, polar solvents and mixtures thereof and the caloric material is a barocaloric material, in particular selected from the group consisting of an alkylcarboxylic acid, an alkyl carboxylate salt, in particular barium or calcium salts of alkyl carboxylate, a liquid crystal, for example 4-(trans-4-pentylcyclohexyl) benzonitrile (PCH5), a plastic crystal, in particular neopentyl glycol (NPG) or 1-adamantanol, 2-amino-2-(hydroxymethyl)propane-1,3-diol, ammonium sulfate salts, and mixtures thereof.

[0089] Preferably, the fluid is selected from the group consisting of alcohols, oils, polar solvents and mixtures thereof and the caloric material is a barocaloric material, in particular neopentyl glycol or 1-adamantanol, more particularly neopentyl glycol.

[0090] Composition

[0091] As indicated above, the composition comprises at least one fluid as defined previously.

[0092] The composition according to the invention may further comprise one or more additives chosen from the group consisting of surfactants, antioxidants, dispersants, friction modifying agents, antifreeze agents, anti-emulsifying agents, antibacterial agents, olfactory tracers and mixtures thereof.

[0093] The additive(s) may be present in the composition according to the invention at a content ranging from 0.05 to 5% by weight, preferably in a content ranging from 0.1% by weight to 3%, relative to the total weight of the composition.

[0094] Use

[0095] The present invention also relates to the use of the fluid, as defined above, as a heat transfer fluid, in particular in thermodynamic systems involving heat transfer.

[0096] Preferably, the fluid is used as a heat transfer fluid in thermodynamic systems or applications involving heat transfer.

[0097] Preferably, the fluid is used as a heat transfer fluid in thermal systems, in cryogenic applications or in mechanical energy conversion systems into pressure.

[0098] The invention also relates to the use of a composition, as described above, for transferring heat.

[0099] Preferably, the composition is used to transfer heat in thermodynamic systems or applications involving heat transfer as described above.

[0100] Thermal systems can be refrigeration, air conditioning or heating systems, preferably refrigeration or heating systems.

[0101] The refrigeration systems may be refrigeration systems used in the residential and / or industrial sector (including freezing), for example in the food industry, in particular for the refrigeration of foodstuffs, the medical sector, in particular for the refrigeration of pharmaceutical compositions, or the electronics sector, battery cooling systems for electric cars, industrial cooling systems, in particular cooling units for hydrogen stations and gas separation units in refineries, for example the separation of olefins at the outlet of a steam cracker.

[0102] Preferably, the refrigeration systems are industrial cooling systems, in particular cooling units for hydrogen stations and gas separation units in refineries.

[0103] Air conditioning systems can be residential, industrial or transport air conditioners, for example in the automotive, heavy goods vehicle or aviation sectors.

[0104] Heating systems include heat pumps, particularly for residential or industrial heating and reheating, such as air, defrost, oil or water heating.

[0105] Cryogenic applications can be for example the liquefaction of natural gas or the liquefaction of hydrogen.

[0106] Preferably, the fluid is used as a heat transfer fluid in refrigeration, air conditioning or heating systems, preferably in refrigeration or heating systems, more preferably in refrigeration systems, in particular for vehicle batteries (for example light or heavy goods vehicles).

[0107] Preferably, the composition is used to transfer heat in refrigeration, air conditioning or heating systems, more preferably in refrigeration or heating systems, more preferably in refrigeration systems, in particular for vehicle batteries (for example light or heavy goods vehicles).

[0108] Thermal system

[0109] The present invention also relates to a thermal system comprising at least one composition, as described above, or a fluid, as defined above, at least one hot source heat exchanger, at least one cold source heat exchanger, and at least one device for applying at least one physical field capable of causing a variation in the absolute value of the entropy AS greater than or equal to 100 J. K 1 .kg 1 within the calorific material of said composition or said fluid.

[0110] Preferably, the device applies at least one electric field, one magnetic field and / or one mechanical stress, such as one pressure stress, more preferably one electric field and / or one mechanical stress.

[0111] Even more preferably, the device applies at least one electric field and / or a pressure constraint, in particular a pressure constraint.

[0112] Preferably, the device applies a physical field, in particular a pressure stress.

[0113] The external physical field is preferably applied at a temperature which can vary from 231 K to 420 K, preferably from 233 K to 400 K, and more preferably from 273 K to 320 K.

[0114] For example, the device for applying at least one physical field may be chosen from the group consisting of an electromagnet, an electric field generator and / or hydraulic cylinder, for example a hydraulic cylinder.

[0115] The thermal system may further comprise at least one system capable of circulating the composition as described above, or the fluid as described above, in particular a pump, between at least the hot source heat exchanger and at least one cold source heat exchanger.

[0116] Preferably, the thermal system is a thermal system as defined above.

[0117] Preferably, the thermal system is selected from the group consisting of a refrigeration system, an air conditioning system or a heating system such as a heat pump.

[0118] Preferably, the thermal system is a refrigeration system, preferably a vehicle battery cooling system (e.g. light or heavy goods vehicles).

[0119] Preferably, the thermal system is an air conditioning system.

[0120] Preferably, the thermal system is a heating system.

[0121] Process

[0122] Another object of the present invention also lies in a heat transfer method comprising at least the circulation of a composition, as defined previously, or of a fluid, as defined previously, between at least one hot source heat exchanger and at least one cold source heat exchanger, and at least the application of at least one physical field to cause a variation in absolute value of entropy AS greater than or equal to 100 J.K' ^kg 1 within the calorific material of said composition or said fluid.

[0123] Preferably, the circulation of the composition or fluid is carried out by at least one circulation pump.

[0124] Preferably, the external physical field may be at least an electric field, a magnetic field and / or a mechanical stress, such as a pressure stress, more preferably an electric field and / or a mechanical stress.

[0125] Even more preferably, the external physical field is an electric field and / or a pressure constraint, in particular a pressure constraint.

[0126] The external physical field is preferably applied at a temperature ranging from 231K to 420K, preferably from 233K to 400K, and more preferably from 273K to 320K.

[0127] According to the present invention, the physical field is in particular applied such that the calorific material is preferably at least temporarily exposed to an interaction with said physical field, preferably with a magnetic field, an electric field and / or a mechanical stress, in particular a pressure stress.

[0128] Preferably, the method according to the invention is a method of transferring heat within a thermal system, as described previously, preferably chosen from the group consisting of a refrigeration system, an air conditioning system or a heating system such as a heat pump.

Claims

DEMANDS 1. Thermal fluid comprising solid particles of at least one heat-retaining material exhibiting an absolute entropy change AS greater than or equal to 100 JK⁻¹.kg⁻¹ 1 , under the action of at least one external physical field, the content of which varies from 2 to 98% by weight, relative to the total weight of the fluid.

2. Fluid according to claim 1, characterized in that the external physical field is chosen from the group consisting of an electric field, a magnetic field and / or a mechanical stress, preferably an electric field and / or a pressure stress.

3. Fluid according to claim 1 or 2, characterized in that the external physical field is a pressure constraint.

4. Fluid according to any one of the preceding claims, characterized in that the calorific material in the form of particles is present in a content ranging from 10 to 90% by weight, preferably in a content ranging from 20 to 80% by weight, more preferably in a content ranging from 30 to 70% by weight, even more preferably in a content ranging from 40 to 60% by weight, relative to the total weight of the fluid.

5. Fluid according to any one of the preceding claims, characterized in that the particles of the calorific material have an average size ranging from 0.1 pm to 1000 pm, preferably an average size ranging from 1 pm to 500 pm.

6. Fluid according to any one of the preceding claims, characterized in that the material is a barocaloric material.

7. Fluid according to any one of the preceding claims, characterized in that it is selected from the group consisting of water, alkanes, alkenes, alcohols, ethers, esters, amines, amides, sulfoxides, fluoroalkanes, perfluoroalkanes, chloroalkanes, siloxanes, and mixtures thereof.

8. Fluid according to the preceding claim, characterized in that it is selected from the group consisting of hexane, ethanol, toluene, propanone, din-n-propyl ether, tetrahydrofuran, 1-butanol, butanamide, pyrrolidine, dimethyl sulfoxide, 1-fluoropentane, water and polydimethylsiloxane and mixtures thereof 9. Use of the fluid as defined according to any one of the preceding claims as a heat transfer fluid, preferably in thermodynamic systems or applications involving heat transfer.

10. Composition comprising at least one thermal fluid as defined according to any one of claims 1 to 8 and optionally one or more additives selected from the group consisting of surfactants, antioxidants, dispersants, friction modifiers, antifreezes, anti-emulsifiers, antibacterials, olfactory tracers and mixtures thereof.

11. Use of the composition as defined according to claim 10 for transferring heat, preferably in thermodynamic systems or applications involving heat transfer, more preferably in thermal systems, cryogenic applications or systems for converting mechanical energy into pressure.

12. Use according to claim 11, characterized in that the thermal systems are refrigeration, air conditioning or heating systems, preferably refrigeration or heating systems.

13. Use according to claim 12, characterized in that the refrigeration systems are systems in the food industry, in particular for refrigerating foodstuffs, the medical field, in particular for refrigerating pharmaceutical compositions, or the electronics field, battery cooling systems for electric cars, industrial cooling systems, in particular cooling units for hydrogen stations and refinery gas separation units, preferably battery cooling systems for electric cars.

14. A thermal system comprising at least one composition, as defined in claim 10, or a fluid, as defined in any one of claims 1 to 8, at least one hot source heat exchanger, at least one cold source heat exchanger, and at least one device for applying at least one physical field capable of causing an absolute entropy change AS greater than or equal to 100 JK⁻¹.kg⁻¹ 1 within the calorific material of said composition.

15. Thermal system according to claim 14, characterized in that the device is a device for applying at least one electric field, one magnetic field and / or one mechanical stress, preferably one pressure stress.

16. System according to claim 14 or 15, characterized in that it is selected from the group consisting of a refrigeration system, preferably a system of vehicle battery cooling, an air conditioning system, or a heating system.

17. A heat transfer method comprising at least circulating a composition, as defined in claim 10, or a fluid, as defined in any one of claims 1 to 8, between at least one hot source heat exchanger and at least one cold source heat exchanger, and at least applying at least one physical field to cause an absolute entropy change AS greater than or equal to 100 J.K 1 .kg 1 within the calorific material of said composition or of said fluid, preferably the physical field being an electric field, a magnetic field and / or a mechanical stress, in particular a pressure stress.