Heat storage particles as well as preparation method and application thereof
By introducing a core-shell structure of conductive and magnetic core and outer shell into the thermal storage particles, and using an alternating magnetic field internal heat source for heating, the problems of heat transfer lag and particle damage under traditional external heating methods are solved, achieving rapid and uniform heat transfer and efficient thermal storage.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2026-01-19
- Publication Date
- 2026-05-12
AI Technical Summary
Existing thermal storage particles suffer from slow heat transfer, delayed thermal response, large temperature gradient, and easy particle damage during heating. In particular, thermochemical thermal storage particles are prone to surface sintering and blockage of gas diffusion channels when heated externally.
The core-shell structure employs a conductive and magnetic core and a heat storage outer shell. The conductive and magnetic core acts as an internal heat source, generating heat in an alternating magnetic field to achieve volume heating from the inside of the particle to the outside, changing the direction of heat transfer, improving the heating rate and uniformity, and enhancing the bonding force between the core and the outer shell through surface roughening treatment.
It enables rapid and uniform heating of thermal storage particles, reduces the risk of particle cracking and damage, improves thermal response speed and thermal storage capacity utilization, improves gas diffusion, and enhances system stability and efficiency.
Smart Images
Figure CN122012039A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of thermal storage technology, specifically to a thermal storage particle, its preparation method, and its application. Background Technology
[0002] Thermal energy storage technology, as a key means to balance energy supply and demand and improve the efficiency of renewable energy utilization, has wide applications in fields such as industrial waste heat recovery and solar thermal power generation. Solid thermal energy storage particles have become an important medium in thermal energy storage systems due to their advantages such as wide operating temperature range, low cost, and ease of large-scale filling.
[0003] Commonly used solid thermal storage materials, such as sensible thermal storage materials like metal oxides, silicate rocks, or concrete, as well as thermochemical thermal storage materials like metal hydroxides and carbonates, typically employ indirect heating methods. This involves heating the metal container walls or internal heat exchange elements, and then transferring the heat from the outside to the particle bed.
[0004] In this heating mode, heat needs to be transferred from the outside to the inside of the particle bed. Due to the generally low thermal conductivity of solid thermal storage materials and the gas-solid contact thermal resistance within the particle bed, the heat transfer process is slow, the thermal response is lag, and some of the storage capacity cannot be effectively utilized. Simultaneously, external heating easily creates large temperature gradients within the particles and radially within the bed, inducing thermal stress during thermal cycling and leading to problems such as microcracks and pulverization on the particle surface, affecting the long-term stability of the system. For thermochemical thermal storage particles, external heating may also cause surface sintering, blocking gas diffusion channels and reducing reaction efficiency. Summary of the Invention
[0005] To address the issues of improving the heating rate and uniformity of thermal storage particles under heating conditions, and avoiding problems such as hindered heat transfer, large temperature gradients, and easy damage to particles, this invention provides a thermal storage particle, its preparation method, and its application.
[0006] The first aspect of this invention provides a thermal storage particle. The thermal storage particle includes a conductive and magnetic core and a thermal storage outer shell covering the conductive and magnetic core, wherein the thermal conductivity of the conductive and magnetic core is greater than that of the thermal storage outer shell. By using the conductive and magnetic core as an internal heat source, heat is directly generated in an alternating magnetic field, achieving volumetric heating from the inside of the particle to the outside. This reconstructs the radial temperature distribution, resulting in a gradient characteristic of high internal temperature and low external temperature. Compared to the gradient of high external temperature and low internal temperature formed by traditional external heating methods, this internal heating mode ensures that both the heat transfer direction and the temperature gradient direction are from the inside to the outside, effectively reducing the risk of cracking of the outer shell due to tensile stress. This improves the overall heating rate and uniformity, and significantly reduces the risk of particle damage due to thermal stress.
[0007] Optionally, the material of the conductive and magnetic core is selected from one or more combinations of low-carbon steel, iron-nickel alloy, and iron-chromium-aluminum alloy. These materials have high magnetic permeability and high electrical conductivity, which can efficiently generate eddy current heat in an alternating magnetic field, thereby improving the efficiency of induction heating.
[0008] Optionally, the surface of the conductive and magnetic core is constructed with a roughened structural layer obtained by sandblasting or chemical etching. This roughened structure enhances the mechanical bonding force between the core and the outer shell layer, prevents interface delamination, reduces contact thermal resistance, and improves heat transfer.
[0009] Optionally, the diameter of the conductive and magnetic core is greater than twice its skin depth at the operating frequency. This ensures that electromagnetic energy is primarily absorbed by the core and converted into heat, avoiding energy transmission loss and improving heating efficiency.
[0010] Optionally, the heat storage particles are sensible heat storage particles, and the outer shell layer of the sensible heat storage particles is also a sensible heat storage shell layer; the sensible heat storage shell layer is doped with thermally conductive filler or a conductive auxiliary phase; the particle size of the sensible heat storage particles is 10~30 mm; the diameter of the conductive and magnetic core core accounts for 30%~40% of the particle size of the sensible heat storage particles. This structure optimizes the heat conduction path, shortens the thermal response time, and improves the utilization rate of sensible heat storage capacity.
[0011] Optionally, the thermal storage particles are thermochemical thermal storage particles, and the outer shell layer of the thermochemical thermal storage particles is also a thermochemical thermal storage shell layer; the thermochemical thermal storage shell layer is doped with a pore-forming agent; the particle size of the thermochemical thermal storage particles is 20~50 mm; the diameter of the conductive and magnetic core core accounts for 15%~25% of the particle size of the thermochemical thermal storage particles. This facilitates the diffusion of gaseous products from the inside to the outside, avoids surface sintering and pore blockage, and improves reaction kinetics and cycle stability.
[0012] Optionally, the heat storage particles can be spherical, spindle-shaped, or teardrop-shaped. These shapes improve the flowability and uniformity of the particles in the bed, and reduce fluid resistance.
[0013] A second aspect of the present invention provides a method for preparing thermal storage particles, comprising the following steps: Preparation of conductive and magnetic core: Processing a conductive and magnetically permeable material into a conductive and magnetic core; Core surface roughening treatment: The surface of the conductive and magnetic core is roughened; Core-shell structure coating granulation molding: The conductive and magnetic core obtained in the core surface roughening treatment step is used as the granulation seed crystal. The heat storage outer shell powder is covered on the surface of the conductive and magnetic core by the adhesive until the set particle size is reached to obtain the heat storage particle green blank. Heat treatment and curing of green blanks: Heat treatment is performed on the green blanks of heat storage particles to obtain heat storage particles.
[0014] This method can produce composite thermal storage particles with stable structure and strong interfacial bonding.
[0015] A third aspect of this invention provides a thermal storage system, comprising the aforementioned thermal storage particles, a thermal storage tank body, an induction coil, and an induction power supply. The induction coil is electrically connected to the induction power supply. The thermal storage particles are placed inside the thermal storage tank body. The conductive and magnetic core is heated in an alternating electromagnetic field generated by the induction coil, and the generated heat is transferred to and stored by the thermal storage outer shell layer. This system achieves rapid and uniform heating inside the particles, improving the thermal storage rate and power density.
[0016] Optionally, the thermal storage system also includes a flow equalization plate. The thermal storage tank body includes a first opening and a second opening, and the flow equalization plate is disposed inside the thermal storage tank body, close to the first and second openings. This can improve the uniformity of fluid distribution and increase heat exchange efficiency. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the thermal storage particle structure provided for some embodiments of the present invention.
[0018] Figure 2 This is a schematic diagram of the thermal storage system provided in the second embodiment of the present invention.
[0019] Figure 3 This is a schematic diagram of the microscopic interlocking interface between the conductive and magnetic core and the heat storage outer shell layer, provided for some embodiments of the present invention.
[0020] Figure 4 A flowchart illustrating the preparation method of heat storage particles provided in the third embodiment of the present invention.
[0021] Reference numerals: 1-Conductive and magnetic core, 2-Sensible heat storage outer shell, 3-Thermochemical heat storage outer shell, 4-Heat storage particles, 5-Flow equalization plate, 6-Fluid inlet, 7-Fluid outlet, 8-Induction coil, 9-Insulation layer, 10-Induction power supply, 11-Roughened structure layer, 100-Heat storage system. Detailed Implementation
[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0023] <First Implementation Method> This embodiment provides a heat storage particle.
[0024] like Figure 1 As shown, the thermal storage particle 4 has a core-shell structure, including a conductive and magnetic core 1 located at the center and a thermal storage outer shell layer tightly covering it. The thermal conductivity of the conductive and magnetic core 1 is set to be greater than that of the thermal storage outer shell layer.
[0025] The conductive and magnetic core 1 serves as the internal heat source and structural framework of the particle. Its function is to induce eddy currents in an alternating magnetic field, efficiently converting electromagnetic energy into heat energy. Due to the excellent thermal conductivity of the core material itself, heat can be rapidly and uniformly distributed within the core, forming an internal homogeneous body. The heat storage outer shell primarily functions to store thermal energy. Its material typically possesses a high specific heat capacity or is capable of undergoing reversible thermochemical reactions to achieve high-density energy storage.
[0026] When the heat storage particle 4 is placed in an alternating magnetic field, the magnetic field penetrates the outer shell and acts directly on the internal conductive and magnetic core 1, causing it to heat up instantly. Since the heat source is located in the particle core, the heat generation starts from the inside. Then, thanks to the high thermal conductivity of the core, the heat is rapidly and uniformly conducted radially from the core to the outer shell. This inside-out heating mode changes the traditional external heating path where heat needs to be slowly transferred from the particle surface inward, significantly shortening the distance heat is transferred to various parts of the outer shell and reducing the heat transfer lag caused by the poor thermal conductivity of the material itself. Therefore, the particle as a whole can achieve rapid and uniform heating, effectively avoiding excessive temperature gradients in the radial direction of the particle. Due to the more uniform temperature distribution, the thermal stress borne by the particle during thermal cycling is greatly reduced, thereby suppressing the generation, propagation, and even particle pulverization caused by uneven thermal expansion and contraction, improving the structural stability and cycle life of the particle.
[0027] In this embodiment, the material of the conductive and magnetic core 1 needs to possess high magnetic permeability and high electrical conductivity to ensure high energy conversion efficiency in an alternating magnetic field. It should be noted that, in addition to specific materials such as low-carbon steel, iron-nickel alloys, and iron-chromium-aluminum alloys, other metals or alloys that meet similar soft magnetic properties (such as high saturation magnetization and low coercivity) and good conductivity, such as certain amorphous or nanocrystalline soft magnetic alloys, can also be used as alternatives. The core is typically spherical to facilitate subsequent coating granulation and ensure the overall flowability of the particles, but it can also be adjusted to a near-spherical shape or other regular geometries depending on the specific application scenario.
[0028] Furthermore, such as Figure 3As shown, to enhance the bonding force between the core and the outer shell and improve interfacial thermal conductivity, a roughened structure layer 11 can be constructed on the surface of the conductive and magnetic core 1. This microstructure increases the contact area between the two and creates a mechanical interlocking effect. It should be noted that the formation of the roughened structure layer 11 is not limited to sandblasting or chemical etching; other physical or chemical methods that can increase surface roughness, such as laser roughening and plasma treatment, can also achieve similar effects.
[0029] Preferably, the size of the conductive and magnetic core 1 is set to match the operating electromagnetic frequency, and its diameter is typically set to be more than twice its skin depth at the operating frequency. This setting ensures that the penetration depth of the alternating magnetic field inside the core is limited, and electromagnetic energy can be concentrated and absorbed and efficiently converted into heat energy in the surface area of the core, avoiding energy loss caused by the magnetic field directly penetrating the entire core, thereby optimizing heating efficiency.
[0030] Depending on the different heat storage mechanisms, the heat storage particles 4 in this embodiment can be divided into two types: sensible heat storage type and thermochemical heat storage type.
[0031] For the sensible heat storage particles 4, the outer shell is a sensible heat storage outer shell layer 2, and the material utilizes its sensible heat for heat storage. Optional materials include alumina, magnesium oxide, silicate rock, ceramic composites, or stabilized metal oxides. These materials typically possess high specific heat capacity and thermal stability. To compensate for the potentially low intrinsic thermal conductivity of the outer shell material, high thermal conductivity fillers, such as graphite, silicon carbide, and aluminum nitride, or conductive auxiliary phases, such as metal powder, can be doped into the sensible heat storage outer shell layer 2 to further improve the effective thermal conductivity of the outer shell layer and accelerate heat diffusion from the core to the outer surface of the particles. The particle size of the sensible heat storage particles 4 is preferably 10–30 mm; the diameter of the conductive and magnetic core 1 is preferably 30%–40% of the total particle size. This proportion ensures sufficient internal heat source power density while maintaining a reasonable outer shell layer thickness, ensuring rapid heat conduction to the particle surface and achieving a rapid thermal response.
[0032] For the thermochemical thermal storage particles 4, their outer shell is a thermochemical thermal storage outer shell layer 3. The material is used for heat storage and release through reversible chemical reactions, such as calcium hydroxide / calcium oxide systems (Ca(OH)2 / CaO) or calcium carbonate / calcium oxide systems (CaCO3 / CaO). The advantage of this type of material is that its energy storage density is much higher than that of sensible heat storage. To solve the problem of gas diffusion during the reaction of thermochemical thermal storage materials, this embodiment utilizes the characteristics of internal heating. During the endothermic decomposition reaction, the reaction starts from the inside of the particle and proceeds to the outer surface. The diffusion direction of the gaseous products (such as water vapor and carbon dioxide) produced by the reaction is consistent with the direction of heat transfer, both from the inside to the outside, which greatly shortens the diffusion path of the gas in the product layer. To further optimize the gas diffusion channels, pore-forming agents, such as ammonium carbonate, starch, and polymer microspheres, can be doped into the thermochemical thermal storage outer shell layer 3. These pore-forming agents decompose or volatilize during subsequent heat treatment, forming a uniformly distributed and interconnected pore network in the outer shell layer. The particle size of the thermochemical thermal storage particles 4 is typically larger than that of the sensible thermal type, preferably 20-50 mm. This is because thermochemical reactions are often accompanied by large volume changes and gas diffusion requirements, necessitating a thicker reaction layer to accommodate them. Correspondingly, the diameter of the conductive and magnetic core 1 is slightly lower, preferably 15%-25%, to reserve sufficient space for the reaction and gas diffusion of the outer shell layer, while still providing an effective internal heat source.
[0033] The overall shape of the heat storage particles 4 is preferably spherical, spindle-shaped, or teardrop-shaped. These shapes facilitate uniform filling of the particles in the heat storage bed, reduce the non-uniformity of local porosity, thereby improving the uniformity of fluid distribution (such as carrier gas or heat exchange fluid) when passing through the bed, reducing flow resistance, and improving heat exchange or reaction efficiency.
[0034] This embodiment achieves direct, rapid, and uniform internal heating of the heat storage particles 4 in an electromagnetic field by constructing a core-shell structure with a high thermal conductivity, electrical conductivity, and magnetic conductivity core and a heat storage outer shell layer, and by optimizing the material and structural parameters of each component. This effectively overcomes the problems of heat transfer lag, large temperature gradient, and easy damage to particles under traditional external heating methods.
[0035] <Second Implementation Method> This embodiment provides a thermal storage system applicable to the thermal storage particles 4 of the first embodiment.
[0036] like Figure 2As shown, the thermal storage system 100 includes: a thermal storage tank body, an induction coil 8, an induction power supply 10, and thermal storage particles 4 as the thermal storage medium. The thermal storage tank body is typically a vertical or horizontal high-temperature pressure vessel, and its shape can be cylindrical, square, etc. The tank body is provided with a fluid inlet 6 and a fluid outlet 7 for introducing and discharging carrier gas or heat exchange fluid. The tank body itself needs to be made of non-magnetic, electrically insulating, and high-temperature resistant materials to ensure that the alternating magnetic field generated externally can penetrate the tank wall without loss and directly act on the internal thermal storage particles 4, while the tank body itself will not heat up due to induction. Optional materials include refractory bricks, refractory castables, ceramics (such as alumina ceramics), or quartz glass. To reduce heat loss, the outer wall of the tank is usually covered with a high-efficiency thermal insulation layer 9, such as ceramic fiber cotton, aluminosilicate felt, or aerogel felt.
[0037] The induction coil 8 is tightly wound around the outside of the heat storage tank body and is usually made of hollow copper tubing, which can be cooled by water during operation. The induction coil 8 is connected to an external induction power supply 10 via a cable. The induction power supply 10 can generate a high-frequency alternating current, which, when flowing through the induction coil 8, generates a high-intensity high-frequency alternating magnetic field in the space surrounding the coil.
[0038] A large number of thermal storage particles 4 are filled into the thermal storage tank, forming a fixed particle bed. To improve the uniformity of fluid distribution within the bed and prevent airflow short-circuiting or particle blow-out, flow equalization plates 5 are typically installed inside the tank near the fluid inlet 6 and fluid outlet 7. The flow equalization plates 5 are made of high-temperature resistant inert materials (such as ceramics or refractory materials) and have numerous small holes smaller than the particle size of the thermal storage particles 4, thus blocking particle passage while ensuring uniform fluid flow through the bed. At the bottom of the bed, a high-temperature resistant insulating grid is sometimes installed to support the weight of the particles and ensure unobstructed flow at the bottom.
[0039] Specifically, the working process of the thermal storage system 100 is as follows: During the heat storage stage, the induction power supply 10 is activated, and a high-frequency alternating current passes through the induction coil 8, generating an alternating magnetic field inside the heat storage tank. This magnetic field penetrates the tank wall and the outer shell of the particles, directly acting on the conductive and magnetic core 1 inside each heat storage particle 4. The conductive and magnetic core 1 generates strong eddy currents due to electromagnetic induction, rapidly converting electrical energy into heat energy, causing a sharp rise in core temperature. Since the thermal conductivity of the core is much higher than that of the outer shell, heat is quickly homogenized within the core and rapidly conducted radially outward to the outer heat storage shell. For sensible heat storage particles, the outer shell absorbs and stores heat through sensible heat, causing a rapid rise in overall temperature. For thermochemical heat storage particles, when the heat transferred by the core causes the outer shell temperature to reach its reaction temperature, an endothermic decomposition reaction occurs. It is noteworthy that, because the heat source is internal, the reaction front advances from the inside of the particle to the outer surface, the diffusion direction of the generated gaseous products is consistent with the heat flow direction, and the unreacted outer layer remains porous, resulting in low gas diffusion resistance and effectively avoiding surface sintering and pore blockage problems. At this point, an appropriate carrier gas can be introduced as needed, entering through fluid inlet 6, to carry the gaseous products generated by the reaction out of the system and promote the forward decomposition reaction. For example, for the decomposition of Ca(OH)2, an inert gas or a gas with a low water vapor partial pressure can be introduced.
[0040] During the heat release phase, induction heating is stopped. When heat needs to be released, a cold heat exchange fluid (such as air, nitrogen, carbon dioxide, or molten salt) is introduced into the heat storage tank through the fluid inlet 6. The fluid passes through the flow equalization plate 5 and flows evenly through the bed of high-temperature heat storage particles 4. For sensible heat storage particles, the fluid undergoes convective heat exchange with the particle surface, absorbing the sensible heat stored in the particles and becoming a hot fluid, which flows out from the fluid outlet 7 to supply heat to the user end. For thermochemical heat storage particles, the introduced fluid usually contains reactant gases, which diffuse within the porous outer shell of the particles and undergo an exothermic synthesis reaction with the thermochemical materials. The heat released by the reaction rapidly heats the fluid, and the hot fluid flows out of the tank for heating. During this process, the highly thermally conductive and magnetically conductive core 1 inside the particles also plays a role in heat equalization, helping to quickly transfer the heat of reaction to the particle surface and improve heat exchange efficiency.
[0041] This embodiment organically combines thermal storage particles 4 with an electromagnetic induction heating system to construct a large-scale thermal storage system 100 with fast response speed, uniform heating, high thermal efficiency and low risk of particle damage. It is suitable for scenarios such as smoothing fluctuations in renewable energy power generation, industrial waste heat recovery and grid peak shaving.
[0042] <Third Implementation Method> This embodiment provides a method for preparing thermal storage particles, used to prepare thermal storage particles 4 of the first embodiment and the second embodiment.
[0043] like Figure 4As shown, the preparation method of the heat storage particle 4 includes four steps: preparation of conductive and magnetic core 1, surface roughening treatment of core, core-shell structure coating and granulation molding, and green body heat treatment and curing.
[0044] The preparation steps of the conductive and magnetic core are as follows: The goal of this step is to obtain a metallic core with specific composition, size, and magnetoelectric properties. Powder metallurgy is typically used. First, suitable metal or alloy powders are selected, such as atomized iron powder, iron-nickel alloy powder, or iron-chromium-aluminum alloy powder. The powder is filled into a mold of a specific shape (e.g., spherical) and pressed under pressure to obtain a green compact with a certain strength. Subsequently, the green compact is sintered at high temperature in a protective atmosphere (e.g., argon, nitrogen, or an argon-hydrogen mixture). The sintering temperature and time depend on the material, and the purpose is to allow metallurgical bonding to form between powder particles through diffusion, resulting in dense or near-dense metal particles. To optimize the soft magnetic properties of the core (e.g., increasing permeability and reducing coercivity), the sintered core is usually subjected to annealing heat treatment to eliminate internal stress generated during processing, purify grain boundaries, and promote grain growth. Annealing also needs to be carried out in a protective atmosphere or vacuum to prevent oxidation. It should be noted that, in addition to powder metallurgy, for materials with specific requirements, spherical metal powders can also be directly prepared by molten metal atomization, and then the cores of the required particle size can be obtained by sieving. This method may eliminate the pressing and sintering steps, but may require annealing of the powder to improve its performance.
[0045] Core Surface Roughening Process: The purpose of this step is to create a micro-roughened structure layer 11 on the surface of the conductive and magnetic core 1 to enhance its mechanical bonding with the subsequent outer shell layer. Commonly used methods include sandblasting and chemical etching. In sandblasting, the core is placed in a sandblasting machine, and abrasives of a specific particle size (such as white or brown fused alumina) are used under compressed air to uniformly impact the core surface, creating an uneven surface. After treatment, thorough cleaning is required to remove any adhering abrasive residue. Chemical etching involves immersing the core in a specific etching solution, selectively corroding the surface through a chemical reaction to form trenches and pores. For example, for iron-based materials, dilute hydrochloric acid or dilute sulfuric acid solutions can be used, often with the addition of corrosion inhibitors to control the corrosion rate and uniformity. After etching, thorough washing, neutralization, and drying are necessary. It should be noted that the specific process parameters for roughening (such as sandblasting pressure, abrasive type, etching solution concentration, time, and temperature) need to be optimized based on the properties of the core material and the processing objectives. The microstructure formed in this step provides a basis for the subsequent anchoring of the outer shell powder.
[0046] Core-shell structure coating granulation molding steps: This step involves uniformly coating the heat storage outer shell material onto the surface-treated conductive and magnetic core 1 to form a core-shell structure green body. Rolling granulation or fluidized bed spraying granulation methods are typically used. Taking rolling granulation as an example: First, the surface-treated, cleaned, and dried conductive and magnetic core 1 is placed as a "seed" in a granulator (such as a coating machine or rotary table). The equipment is started to keep the seed continuously rolling. Then, the following operations are performed alternately: First, an atomized adhesive solution (such as polyvinyl alcohol PVA aqueous solution, silica sol, etc.) is sprayed onto the surface of the rolling seed to wet the seed surface; then, a measured amount of premixed and dried outer shell powder is added. Relying on the adhesive force of the adhesive and the extrusion force generated by rolling, the powder gradually adheres to and compacts onto the wet core surface. By repeating the "spraying liquid-adding powder" cycle, the outer shell layer grows layer by layer until the preset particle size is reached. Fluidized bed spray granulation is carried out in a fluidized bed granulator. The seed crystal core is fluidized under the action of airflow, while the binder solution and outer shell powder are simultaneously atomized and sprayed onto the fluidized seed crystal surface, achieving coating. This method offers high coating efficiency and good uniformity. During this process, the roughened structure of the seed crystal core surface effectively captures the outer shell powder, and the binder cures to form a strong mechanical bond.
[0047] Green body heat treatment and curing steps: The purpose of this step is to give the coated green body particles the final required mechanical strength and microstructure. The heat treatment process varies depending on the type of outer shell. For sensible heat storage particles, the outer shell typically needs to be densified to improve strength and thermal conductivity, therefore a high-temperature sintering process is used. The green body is heated to the sintering temperature of the outer shell material in a suitable atmosphere (such as air, a weakly oxidizing, or a protective atmosphere) and held for a period of time to allow the outer shell powder particles to undergo ceramic sintering, forming a dense shell. Sintering conditions need to be precisely controlled to avoid excessive oxidation of the core or adverse chemical reactions with the outer shell. For thermochemical heat storage particles, the outer shell needs to remain porous to facilitate gas diffusion, therefore a low-temperature curing process is used. The green body is heated under conditions far below its thermal decomposition temperature (such as in air). The core purpose is to completely remove organic binders added during molding and any pore-forming agents that may have been added, while simultaneously giving the outer shell a certain mechanical strength. This process does not cause the heat storage material to sinter and densify, but rather forms a porous, stable shell structure.
[0048] The preparation method provided in this embodiment has clear steps and controllable process, and can effectively prepare core-shell structured composite thermal storage particles 4 with strong interfacial bonding and adjustable structural parameters, providing a manufacturing basis for achieving its excellent electromagnetic induction heating performance and cycle stability.
[0049] The above are merely optional embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A type of heat storage granules, characterized in that, include: Conductive and magnetic core; A thermal storage outer shell layer covers the outside of the conductive and magnetic core. The thermal conductivity of the conductive and magnetic core is greater than that of the thermal storage outer shell.
2. The heat storage particles as described in claim 1, characterized in that, The material of the conductive and magnetic core is selected from one or more combinations of low-carbon steel, iron-nickel alloy, and iron-chromium-aluminum alloy.
3. The heat storage particles as described in claim 1, characterized in that, The surface of the conductive and magnetic core is constructed with a roughened structural layer obtained by sandblasting or chemical etching.
4. The heat storage particles as described in claim 1, characterized in that, The diameter of the conductive magnetic core is greater than twice its skin depth at the operating frequency.
5. The heat storage particles as described in claim 1, characterized in that, The heat storage particles are sensible heat storage particles, and the heat storage outer shell layer of the sensible heat storage particles is a sensible heat storage outer shell layer. The sensible heat storage outer shell layer is doped with thermally conductive filler or a conductive auxiliary phase. The particle size of the sensible heat storage particles is 10~30 mm; the diameter of the conductive and magnetic core is 30%~40% of the particle size of the sensible heat storage particles.
6. The heat storage particles as described in claim 1, characterized in that, The heat storage particles are thermochemical heat storage particles, and the heat storage outer shell layer of the thermochemical heat storage particles is a thermochemical heat storage outer shell layer. The thermochemical thermal storage outer shell layer is doped with a pore-forming agent; The particle size of the thermochemical thermal storage particles is 20-50 mm; the diameter of the conductive and magnetic core is 15%-25% of the particle size of the thermochemical thermal storage particles.
7. The heat storage particles as described in claim 1, characterized in that, The heat storage particles are spherical, spindle-shaped, or teardrop-shaped.
8. A method for preparing thermal storage particles, applied to the thermal storage particles as described in any one of claims 1-7, characterized in that, Includes the following steps: Preparation of conductive and magnetic core: Processing conductive and magnetic materials into conductive and magnetic cores; Core surface roughening treatment: The surface of the conductive and magnetic core is roughened; Core-shell structure coating granulation molding: The conductive and magnetic core obtained in the core surface roughening treatment step is used as a granulation seed crystal. The heat storage outer shell powder is covered on the surface of the conductive and magnetic core by an adhesive until the set particle size is reached to obtain a heat storage particle green blank. Heat treatment and curing of green blanks: The green blanks of the heat storage particles are subjected to heat treatment to obtain heat storage particles.
9. A thermal storage system, characterized in that, The device includes thermal storage particles as described in any one of claims 1-7, a thermal storage tank body, an induction coil, and an induction power supply, wherein the induction coil is electrically connected to the induction power supply, the thermal storage particles are placed inside the thermal storage tank body, and the conductive magnetic core is heated in an alternating electromagnetic field generated by the induction coil, and the generated heat is transferred to the thermal storage outer shell layer and stored by the thermal storage outer shell layer.
10. The thermal storage system as described in claim 9, characterized in that, It also includes a flow equalization plate. The heat storage tank body includes a first opening and a second opening. The flow equalization plate is disposed inside the heat storage tank body, close to the first opening and the second opening.