A method, device, medium and equipment for establishing a model of a packed bed type cold and heat storage device

Abstract

The present application relates to a kind of packed bed type cold storage heat storage device model establishing method, device, medium and equipment, method includes the following steps: based on only considering the heat transfer behavior of heat storage medium in packed bed region, according to the system composition and working principle of molten salt single tank packed bed heat storage system, make assumptions to packed bed type cold storage heat storage device model;Based on the assumption, a one-dimensional transient heat mathematical model of molten salt single tank packed bed heat storage system is established using mixed diffusion model;The one-dimensional transient heat mathematical model is solved, i.e. the energy conservation equation set of molten salt single tank packed bed heat storage system can be obtained;The energy conservation equation set is solved until the temperature field of heat storage molten salt and the internal temperature field of each heat storage unit reach the convergence condition, save the calculation results and update system thermal state.The correctness of the model and the availability of numerical analysis tool are verified by comparing experimental data and numerical calculation results.

Description

Technical Field

[0001] This invention relates to a method, apparatus, medium, and equipment for establishing a model of a packed bed type cold and heat storage device, belonging to the technical field of cold and heat storage device model establishment. Background Technology

[0002] Renewable energy sources are inherently unstable, and achieving a high proportion of renewable energy utilization requires adequate energy storage capacity. Pumped hydro storage has already achieved large-scale installation and application, but due to terrain limitations, its further growth potential is limited. Pumped hydro storage alone cannot meet the future demand for a high proportion of renewable energy, thus creating an urgent need for new, large-capacity energy storage technologies.

[0003] To alleviate the energy and environmental crisis, improve the energy structure, and ensure energy security, the world is accelerating the development of clean and renewable energy. In 2022, global installed capacity of renewable energy power generation reached 2351 GW, accounting for more than one-third of the total global installed capacity, and is expected to continue to grow in the future. With the large-scale integration of renewable energy, its intermittency and instability pose significant challenges to the safety and stability of the power grid, urgently requiring large-scale energy storage technologies to provide effective support for a robust and stable power grid. Compressed air energy storage systems (CAES) are one of the energy storage technologies suitable for large-scale energy storage, with two large power plants already in commercial operation in Germany and the United States, respectively. To further improve the energy storage density of compressed air energy storage systems and reduce dependence on fossil fuels, liquid air energy storage (LAES) and supercritical compressed air energy storage technology (SC-CAES), characterized by liquid air storage, have been developed both domestically and internationally. In recent years, numerous research teams at home and abroad have further developed and improved the system circulation and cold storage subsystems of LAES and SC-CAES, and have conducted a series of thermodynamic, heat transfer, and experimental studies with the goal of improving system circulation efficiency.

[0004] The cold storage subsystem is a crucial component of both LAES and SC-CAES, and its efficiency significantly impacts the system's cycle efficiency. Research institutions conducted experimental studies on a small LAES system with a cold storage efficiency of 51%, revealing a cycle efficiency of only 8%. Thermodynamic analysis of an LAES system with a cold storage efficiency of 70% showed a cycle efficiency reaching 50%. Studies of LAES systems employing packed bed cold storage revealed that recovering cold energy during the energy release process can reduce energy consumption in the air liquefaction process by approximately 25%. Thermodynamic analysis of LAES systems recovering both cold and heat energy showed that cold storage has a greater impact on system efficiency than heat storage; cold energy loss leads to an efficiency loss approximately seven times greater than heat energy loss.

[0005] The cryogenic energy storage subsystem needs to store cold energy between cryogenic (78.8K) and ambient temperature, characterized by low storage temperature and a wide temperature variation range, placing high demands on the stability and safety of the storage materials. Solid storage materials such as rocks have advantages such as a wide suitable temperature range, low cost, and stable properties; therefore, rock-filled bed cryogenic energy storage technology is one of the important cryogenic energy storage technologies. Studies on the thermophysical properties of storage materials in the packed bed show that the thermophysical properties of rock and other storage materials vary greatly within the low-temperature to ambient temperature range, which has a certain impact on the system's energy storage density, the distribution characteristics of the thermocline layer in the packed bed, and the unsteady-state characteristics of the outlet temperature.

[0006] Furthermore, thermal energy storage technology has attracted widespread attention due to its advantages such as wide application range, high energy storage efficiency, low cost, large-scale scalability, long lifespan, and environmental friendliness. Especially in recent years, driven by the rapid development of various application scenarios such as solar thermal power generation, district heating, seawater desalination, and power grid peak shaving and valley filling, medium- and high-temperature thermal energy storage technology has become a research hotspot.

[0007] Packed bed thermal storage is most commonly found in the form of single-tank packed bed thermal storage. Single-tank packed bed thermal storage utilizes natural thermal stratification (thermotropic gradient) caused by the temperature difference as the heat transfer fluid flows through the packed bed to achieve stable separation of the cold and hot storage media and stable heat storage and release outlet temperatures. Packed bed thermal storage can be classified into sensible heat packed bed thermal storage and phase change packed bed thermal storage according to the form of thermal energy stored in the packed bed. Extensive experimental and applied research has shown that both single-tank sensible heat packed bed thermal storage and phase change packed bed thermal storage have good feasibility.

[0008] The influence mechanisms of design parameters and operating conditions on the operational characteristics and thermal storage performance of packed bed thermal storage devices are complex, especially for packed bed thermal storage systems containing phase change filling layers. Therefore, performance optimization and system integration design based on this are crucial for the large-scale application of packed bed thermal storage systems. However, relying solely on experimental work, researchers find it difficult to comprehensively understand the operational characteristics of packed bed thermal storage systems with practical application scales under long-term complex operating conditions in a short period of time, and there are also certain difficulties in exploring the impact of thermal storage system design parameters on thermal storage performance and system integration performance.

[0009] When determining the scale of a packed bed thermal storage system, it is necessary to consider the thermal storage requirements. Existing numerical analysis tools and methods have certain inconveniences and difficulties in the scale design of packed bed thermal storage systems. Therefore, it is particularly urgent to develop a fast, accurate, and universal method for the scale design of packed bed thermal storage systems. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention provides a method, apparatus, medium, and equipment for establishing a model of a packed bed type cold and heat storage device. Based on the mixed diffusion model, enthalpy method, and effective thermal conductivity method, it develops a one-dimensional transient heat transfer mathematical model and related numerical analysis method applicable to a single-tank packed bed heat storage system with arbitrary packed bed configuration. The correctness of the model and the usability of the numerical analysis tool are verified by comparing experimental data and numerical calculation results.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: A method for establishing a model of a filled bed type cold and heat storage device includes the following steps: Based on considering only the heat transfer behavior of the heat storage medium within the packed bed area, and according to the system composition and working principle of the molten salt single-tank packed bed heat storage system, assumptions are made for the model of the packed bed cold and heat storage device. Based on the assumptions, a one-dimensional transient heat transfer mathematical model of a molten salt single-tank packed bed thermal regeneration system is established using a hybrid diffusion model. Solving the one-dimensional transient heat transfer mathematical model yields the energy conservation equations for the molten salt single-tank packed bed thermal regeneration system. Solve the energy conservation equations until the temperature field of the heat storage molten salt and the internal temperature field of each heat storage unit reach the convergence condition, save the calculation results and update the system thermal state.

[0012] The method for establishing the model of the packed bed type cold and heat storage device, preferably, makes the following assumptions about the packed bed type cold and heat storage device model: For heat transfer and flow in heat storage molten salts, a packed bed is equivalent to an isotropic porous medium. The heat transfer and flow of the heat-storing molten salt in the packed bed are both one-dimensional axial. The density and specific heat capacity of heat-storing molten salts are constant, while their viscosity and thermal conductivity are functions of temperature. All packed bed thermal storage units are spherical, and thermal storage units of the same type have a uniform hydraulic diameter; The phase change heat storage medium is uniformly filled in the phase change heat storage unit, and the volume and property changes caused by the solid-liquid phase change are ignored. The melting and solidification processes of phase change thermal storage materials occur within the same temperature range; The thermal properties of the packed bed thermal storage unit are all constant; The contact heat conduction and radiation heat transfer between packed bed heat storage units are ignored, as are the radiation heat transfer between heat storage molten salts and the heat exchange between the heat storage system and the environment.

[0013] The method for establishing the model of the packed bed type cold and heat storage device, preferably, uses a one-dimensional transient heat transfer mathematical model to divide the molten salt single-tank packed bed heat storage system into two computational domains: the first computational domain is the packed bed region through which the heat-transferring molten salt flows, and the second computational domain is the internal region of a single packed bed heat storage unit.

[0014] The method for establishing the model of the packed bed type cold and heat storage device, preferably, uses the following transient energy conservation equation for the packed bed region through which the heat storage molten salt flows: (2.1) In the formula, Porosity of the packed bed; For the transfer of heat storage molten salt density; To transfer the specific heat capacity of the heat-storing molten salt; To transfer the temperature of the heat-storing molten salt; For time; The apparent flow rate of the heat-storing molten salt; In the direction of the filling bed height; The effective thermal conductivity of the heat-storing molten salt; The specific surface area of ​​the packed bed; The thermal resistance per unit area for heat transfer between the heat storage molten salt and the packed bed heat storage unit; Temperature of the packed bed heat storage material; The direction of the thermal storage unit radius; denoted as the inner radius of the heat storage unit.

[0015] The method for establishing the model of the packed bed type cold and heat storage device, preferably, uses the following transient energy conservation equation for the internal region of a single packed bed heat storage unit: (2.14) In the formula, Density of the packed bed heat storage material; Specific enthalpy of packed bed heat storage material; The effective thermal conductivity of the packed bed heat storage material.

[0016] The method for establishing the model of the packed bed type cold and heat storage device, preferably, uses the finite volume method to solve the one-dimensional transient heat transfer mathematical model, and the mesh division of the two computational domains is as follows: the first computational domain is divided along the axial direction into i The first is a cylindrical control volume with the same thickness; the second computational domain is divided along the radial direction into two parts. jEach spherical shell control body has the same thickness. According to the model assumption, the external thermal environment of the heat storage units within each heat transfer and storage molten salt control body is the same. Therefore, by calculating the energy conservation equation of a representative heat storage unit within the control body, the thermal state of all heat storage units within the control body, as well as the heat exchange with the heat transfer and storage molten salt within the control body, can be determined. The energy conservation equation set of the molten salt single-tank packed bed heat storage system consists of equation (2.1) and... i Formula (2.14) is a coupled composition.

[0017] The method for establishing the model of the packed bed cold and heat storage device, preferably, uses the following discretization format for the energy conservation equations of the molten salt single-tank packed bed heat storage system: (2.30) (2.31) In the formula, For the first i Bed porosity of a molten salt fluid control volume; For the first i The volume of the heat storage molten salt control body; For the first i Cross-sectional area of ​​the heat storage molten salt control body; For the first i The first heat storage unit j The volume of each control unit; For the first i The first heat storage unit j The outer surface area of ​​each control body; Let be the inner surface area of ​​the j-th control body within the i-th thermal storage unit; for n At time +1, the... i The molten salt temperature of the fluid control volume; for n At that moment, the i Fluid control volume molten salt temperature; for n +1 hour, j and j +1 Molten salt temperature at the interface of the fluid control volume; for n +1 hour, j and j -1 Molten salt temperature at the interface of the fluid control volume; For the fluid side j , j +1 Axial equivalent thermal conductivity of the interface; for n +1 hour, j +1 adjacent fluid control volume molten salt temperature; For the fluid side j , j -1 Axial equivalent thermal conductivity of the interface; for n +1 hour, j -1 adjacent fluid control volume molten salt temperature; For the first i Control the total solid-liquid heat transfer specific surface area within the body; The solid thermal storage salt wall / packing temperature is the solid phase temperature for interfacial heat transfer. For the first j The molten salt temperature of the fluid control volume is the fluid-side temperature for convective heat transfer. For the first i Density of the unit solid heat storage medium; for n At time +1, the... i thermal storage unit j Enthalpy per unit mass of a solid control volume; for n In the past, the enthalpy per unit mass of the same solid control volume; solid phase j , j +1 Radial interface equivalent thermal conductivity; solid phase j , j -1 Radial interface equivalent thermal conductivity; for n +1 hour, i unit j +1 Solid control body temperature; for n +1 hour, i unit j Solid control volume temperature; for n +1 hour, i unit j -1 solid control body temperature.

[0018] The method for establishing the model of the packed bed thermal energy storage device is preferably that equations (2.30) and (2.31) can be solved using a tridiagonal matrix algorithm. In each time step, equation (2.30) is solved first to obtain the temperature field of the heat transfer and storage molten salt, and the partial thermal properties of the heat transfer and storage molten salt are updated. The apparent flow rate of the heat transfer and storage molten salt is also updated according to equation (2.3). Then, this temperature field is used as the temperature boundary condition of equation (2.31) to solve the internal temperature field of the heat storage unit in the computational domain of each heat transfer and storage molten salt, and the partial thermal properties of the phase change heat storage medium are updated. Then, the obtained surface temperature of each heat storage unit is used as the temperature boundary condition of equation (2.30) to solve the temperature field of the heat transfer and storage molten salt. Equations (2.30) and (2.31) are solved alternately until the temperature field of the heat transfer and storage molten salt and the internal temperature field of each heat storage unit reach the convergence condition. Then, the calculation results are saved and the thermal state of the system is updated.

[0019] A second aspect of the present invention provides a model building device for a filled bed type cold and heat storage device, comprising: The first processing unit is used to make assumptions about the model of the packed bed thermal storage device based on the heat transfer behavior of the heat storage medium within the packed bed area only, and according to the system composition and working principle of the molten salt single-tank packed bed heat storage system. The second processing unit is used to establish a one-dimensional transient heat transfer mathematical model of the molten salt single-tank packed bed thermal storage system based on assumptions and using a hybrid diffusion model. The third processing unit is used to solve the one-dimensional transient heat transfer mathematical model, which can obtain the energy conservation equations of the molten salt single-tank packed bed thermal storage system. The fourth processing unit is used to solve the energy conservation equations until the temperature field of the heat storage molten salt and the internal temperature field of each heat storage unit reach the convergence condition, save the calculation results and update the system thermal state.

[0020] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the method for establishing a model of a filled bed type cold and heat storage device as described in any one of claims 1-8.

[0021] A fourth aspect of the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method for establishing a model of a filled bed type cold and heat storage device as described in any one of claims 1-8.

[0022] The present invention has the following advantages due to the adoption of the above technical solutions: 1. This invention first focuses on the system structure design of a packed bed thermal storage system, including the design of the manifold distributor, the structure of the storage tank, and the classification and selection of the thermal storage medium. It characterizes the working principle and characteristics of the thermal storage system from the perspective of heat transfer and storage cycles. Then, based on the mixing-diffusion model, enthalpy method, and effective thermal conductivity method, a one-dimensional transient heat transfer mathematical model and related numerical analysis methods applicable to single-tank packed bed thermal storage systems with arbitrary packed bed configurations are developed. The boundary conditions, initialization conditions, and calculation solution steps of the model are given. The model is validated by comparing simulation results with experimental results calculated using this model. This provides technical support for studying the operating characteristics and thermal storage performance of single-tank packed bed thermal storage systems.

[0023] 2. Existing numerical analysis tools and methods present certain inconveniences and difficulties in the large-scale design of packed bed thermal regeneration systems. Therefore, it is particularly urgent to develop a fast, accurate, and universal method for the large-scale design of packed bed thermal regeneration systems. Numerical simulation methods offer lower time and economic costs, as well as greater flexibility, and can provide effective guidance for performance optimization, parameter design, and system integration research of packed bed thermal regeneration. Attached Figure Description

[0024] Figure 1 A schematic cross-sectional view of a molten salt single-tank packed bed thermal regeneration system; Figure 2 This is a schematic cross-sectional view of a typical three-layer hybrid packed bed; Figure 3 Tank structure for a molten salt single-tank packed bed thermal regeneration system; Figure 4 A schematic diagram of molten salt flow in a molten salt single-tank packed bed regenerator system; Figure 5 a is a diagram of the packed bed region through which the heat-transferring molten salt flows. Figure 5 b is a diagram of the internal area of ​​a single packed bed thermal storage unit; Figure 6 Flowchart for transient calculations of heat storage in a packed bed; Figure 7 The experimental results show the temperature distribution of the heat-transferring molten salt along the axis. Figure 8 A graph showing the change of water temperature over time as measured by each thermocouple; The attached figures are labeled as follows: 1-Storage tank body; 2-Storage medium; 3-Lower manifold distributor; 4-Foundation; 5-Upper manifold distributor; 6-Molten salt free surface; 7-Cryogenic molten salt pump; 8-High temperature molten salt pump; 9-Ventilation port; 10-Insulation layer. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0026] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," "third," "fourth," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0027] For ease of description, spatial relative terms may be used in the text to describe the relationship of one element or feature relative to another element or feature as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "above," etc. Such spatial relative terms are intended to include different orientations of the device in use or operation, other than those depicted in the figure.

[0028] The influence mechanisms of design parameters and operating conditions on the operational characteristics and thermal storage performance of packed bed thermal storage devices are complex, especially for packed bed thermal storage systems containing phase change filling layers. Therefore, performance optimization and system integration design based on this are crucial for the large-scale application of packed bed thermal storage systems. However, relying solely on experimental work, researchers find it difficult to comprehensively understand the operational characteristics of packed bed thermal storage systems with practical application scales under long-term complex operating conditions in a short period of time, and there are also certain difficulties in exploring the impact of thermal storage system design parameters on thermal storage performance and system integration performance.

[0029] When determining the scale of a packed bed thermal storage system, it is necessary to consider the thermal storage requirements. Existing numerical analysis tools and methods have certain inconveniences and difficulties in the scale design of packed bed thermal storage systems. Therefore, it is particularly urgent to develop a fast, accurate, and universal method for the scale design of packed bed thermal storage systems.

[0030] Based on the above-mentioned technical problems, this invention provides a method for establishing a model of a packed bed cold and heat storage device. Based on the mixed diffusion model, enthalpy method and effective thermal conductivity method, a one-dimensional transient heat transfer mathematical model and related numerical analysis method for a single-tank packed bed heat storage system applicable to any packed bed configuration are developed. The correctness of the model and the usability of the numerical analysis tool are verified by comparing experimental data and numerical calculation results.

[0031] like Figure 1 As shown, the structure and functions of the components of the packed bed device are first introduced. Taking the molten salt single-tank packed bed thermal regeneration system as an example, the system consists of four main parts: the thermal regeneration tank body 1, the thermal regeneration medium 2, the manifold distributor (including the lower manifold distributor 3 and the upper manifold distributor 5), and the molten salt pump (including the low-temperature molten salt pump 7 and the high-temperature molten salt pump 8).

[0032] Specifically, the cylindrical heat storage tank 1 sits on the foundation 4. Inside the tank, from bottom to top, are the lower manifold distributor 3, the heat storage medium 2 located in the packed bed area (including the solid packed bed and the surrounding heat transfer and storage molten salt), the upper manifold distributor 5, the molten salt free surface 6, the tank top space, and the vent 9. The molten salt pump is vertically inserted into the tank. The working fluid inlet of the low-temperature molten salt pump 7 is connected to the outlet of the lower manifold distributor 3, and the working fluid inlet of the high-temperature molten salt pump 8 is connected to the outlet of the upper manifold distributor 5.

[0033] The main function of the heat storage tank is to contain the heat storage medium 2, which in turn absorbs, stores, and releases heat energy. The main functions of the upper manifold distributor 5 and the lower manifold distributor 3 are to establish a nearly axially uniform flow field of the heat transfer molten salt within the packed bed region, so as to efficiently utilize the theoretical heat storage capacity of the heat storage system. The main function of the molten salt submersible pump is to realize the flow of the heat transfer molten salt within the heat storage system and its mass exchange with the outside environment. Since the volume change of the heat transfer molten salt with temperature changes during system operation is not negligible, sufficient space must be reserved at the top of the tank for the free movement of the molten salt surface. It is worth noting that... Figure 1 The number and location of the submerged pump and the top ventilation openings of the tank are for illustrative purposes only and do not represent the specific design layout.

[0034] The manifold distributor consists of three types of pipes of different diameters: inlet / outlet mains, primary manifolds, and secondary manifolds. The secondary manifolds have holes of a certain density to allow the heat transfer molten salt to flow in and out. An ideal manifold distributor ensures that the heat transfer molten salt forms a nearly uniform axial flow field distribution after entering the packed bed region. Another important function of the manifold distributor is to prevent the solid heat storage medium 2 from flowing out of the heat storage system within the packed bed region, thus ensuring the purity of the heat transfer molten salt. This function can be achieved by installing filters at the holes in the secondary manifolds. It is worth noting that the size of the filter needs to be considered in conjunction with the total pressure drop of the heat storage system and the average diameter of the solid heat storage units (and their debris).

[0035] The heat storage medium 2 of the molten salt single-tank packed bed heat storage system can be divided into two categories according to its form: solid packed bed and liquid heat transfer and heat storage molten salt. The packed bed is formed by randomly stacking heat storage units in the internal space of the tank between the upper and lower manifold distributors; the heat transfer and heat storage molten salt fills the void area of ​​the packed bed and flows in the void area of ​​the packed bed under the drive of the molten salt pump, realizing heat exchange with the packed bed heat storage units.

[0036] Packed bed thermal storage units can be classified into two categories based on their thermal energy utilization type: sensible heat storage units and phase change thermal storage units. Sensible heat storage units provide thermal storage capacity solely in the form of sensible heat within the operating temperature range of the thermal storage system. The advantages of sensible heat storage units are: easy to obtain, easy to manufacture, inexpensive, and highly corrosion-resistant; their disadvantages are: lower thermal energy density, larger volumetric expansion coefficient, and generally lower thermal conductivity. Phase change thermal storage units provide thermal storage capacity simultaneously in the form of sensible heat and latent heat of solid-liquid phase change within the operating temperature range of the thermal storage system. To avoid contamination of the heat transfer fluid by the liquid phase change thermal storage medium, the phase change thermal storage material must be encapsulated within a certain space. Common encapsulation technologies include: direct filling, electroplating, and hot isostatic pressing. Common encapsulation materials include: glass, metal, ceramics, and graphite. Phase change thermal storage units are typically spherical in shape. The advantages of phase change thermal energy storage units are: high thermal energy density, strong corrosion resistance, and good thermal conductivity (except for inorganic salts); the disadvantages are: complex manufacturing process, poor economic efficiency, and high risk of damage.

[0037] Based on the selection and configuration of the heat storage units, packed beds can be divided into three categories: sensible heat type, phase change type, and hybrid type. Sensible heat type packed beds consist entirely of sensible heat storage units; phase change type packed beds consist of one or more phase change heat storage units; and hybrid type packed beds consist of both sensible heat storage units and phase change heat storage units.

[0038] like Figure 2 The diagram shows a typical cross-sectional view of a three-layer hybrid packed bed (the thick black dashed box represents the internal space of the tank between the upper and lower manifold distributors). As shown... Figure 2As shown, the packed bed consists of a high-temperature phase change heat storage unit (the melting point of the high-temperature phase change material is slightly lower than the upper limit of the working temperature of the heat storage system), a sensible heat storage unit, and a low-temperature phase change heat storage unit (the melting point of the low-temperature phase change material is slightly higher than the lower limit of the working temperature of the heat storage system) from top to bottom (in the direction of gravity).

[0039] Heat transfer and storage molten salts not only act as heat transfer fluids in heat storage systems, but also provide a portion of the heat storage capacity as sensible liquid heat storage media. Common heat transfer and storage molten salts are mostly multi-component nitrates, which have the following advantages: wide operating temperature range, large volumetric specific heat capacity, low viscosity, low toxicity, wide distribution, easy to manufacture, and relatively low price.

[0040] Figure 3 The diagram shows the tank structure of a molten salt single-tank packed bed thermal regenerator system. As can be seen from the diagram, to stabilize the tank structure at high temperatures and prevent leakage of the thermal regenerator medium, the tank wall thickness gradually increases from top to bottom, while the tank bottom thickness gradually increases from the inside to the outside.

[0041] Because the temperature of the heat storage medium 2 in a molten salt single-tank packed bed thermal regeneration system continuously changes within the system's operating temperature range during operation, the tank material should be selected based on its highest operating temperature. Referring to the tank design experience of commercially available molten salt dual-tank thermal regeneration systems, molten salt tank materials can be divided into two categories based on their highest operating temperature: stainless steel (operating temperature above 425℃) and carbon steel (operating temperature below 425℃). Therefore, for traditional thermal oil trough-type solar thermal power generation systems (requiring a thermal regeneration system operating temperature range of 290℃~390℃), carbon steel can be used for the tank material of the packed bed thermal regeneration system; while for molten salt tower-type solar thermal power generation systems with a higher heat collection ratio (requiring a thermal regeneration system operating temperature range of 290℃~570℃), stainless steel is required for the tank material of the packed bed thermal regeneration system.

[0042] The molten salt submersible pump used in the molten salt single-tank packed bed regenerative system is the same as that used in the molten salt dual-tank system, so its structure and operating principle will not be described in detail here. It is worth noting that the terms "high-temperature molten salt pump" and "low-temperature molten salt pump" are merely for ease of distinguishing between different working environments (high- and low-temperature molten salt pumps respectively handle the transport of high- and low-temperature heat transfer and regeneration molten salt). In practice, all molten salt submersible pumps have the same upper limit of design allowable temperature.

[0043] The operating principle of the system of this invention is explained as follows: The molten salt single-tank packed bed thermal storage system utilizes the density difference of the heat-transferring molten salt at different temperatures to achieve natural fluid stratification, effectively separating the cold and hot heat storage media 2. This ensures that the quality of the thermal energy output at the storage and release ends remains stable over a long period. For example... Figure 4As shown, during operation, the hot molten salt (red area) remains above the cold molten salt (blue area) due to its lower density. In the region where the hot and cold molten salts meet, the temperature of the heat-transferring molten salt exhibits an axial gradient distribution. We call this region the "thermospheric slope." The size and location of the thermospheric slope change as the system's heat storage and release processes progress.

[0044] The heat storage and release behavior of the molten salt single-tank packed bed thermal regeneration system is governed by the molten salt pump. The cryogenic molten salt pump draws cold molten salt from the bottom of the packed bed region via the lower manifold distributor 3. After absorbing heat from the outside environment, the cold molten salt becomes hot molten salt and is then injected into the top of the packed bed region via the upper manifold distributor 5. The high-temperature molten salt pump 8 draws hot molten salt from the top of the packed bed region via the upper manifold distributor 5. After releasing heat from the outside environment, the hot molten salt becomes cold molten salt and is then injected into the bottom of the packed bed region via the lower manifold distributor 3. If the mass flow rate of the cryogenic molten salt pump 7 is greater than the mass flow rate of the high-temperature molten salt pump 8, the system stores heat; if the mass flow rate of the cryogenic molten salt pump 7 is less than the mass flow rate of the high-temperature molten salt pump 8, the system releases heat; if the mass flow rate of the cryogenic molten salt pump 7 is equal to the mass flow rate of the high-temperature molten salt pump 8, the system's heat storage and release are balanced (standby state).

[0045] During system heat storage, the hot molten salt, under the action of the upper manifold distributor 5, forms a uniform axial velocity flow, flowing from top to bottom and gradually heating the packed bed, while the inclined temperature layer moves towards the bottom of the tank. When the inclined temperature layer reaches the bottom of the tank, the temperature of the heat-transferring molten salt pumped by the low-temperature molten salt pump 7 begins to rise. When the temperature of the heat-transferring molten salt exceeds the heat storage cutoff temperature, the low-temperature molten salt pump 7 stops working, and the heat storage process ends. During system heat release, the cold molten salt, under the action of the lower manifold distributor 3, forms a uniform axial velocity flow, flowing from bottom to top and gradually cooling the packed bed, while the inclined temperature layer moves towards the top of the tank. When the inclined temperature layer reaches the top of the tank, the temperature of the heat-transferring molten salt pumped by the high-temperature molten salt pump 8 begins to decrease. When the temperature of the heat-transferring molten salt is lower than the heat release cutoff temperature, the high-temperature molten salt pump 8 stops working, and the heat release process ends.

[0046] The temperature of most of the heat storage medium 2 located within the thermocline is between the heat storage and release cutoff temperatures. Due to the existence of these cutoff temperatures, a portion of the heat storage capacity of this part of the heat storage medium 2 cannot be used to store and release heat energy. Therefore, the morphology of the thermocline during the operation of the heat storage system is closely related to the heat storage performance of the system.

[0047] A second aspect of the present invention provides a method for establishing a model of a filled bed type cold and heat storage device, comprising the following steps: 1. Modeling assumptions To balance computational resources and model accuracy, only the heat transfer behavior of the regenerator medium within the packed bed region is considered. Based on the system composition and working principle of the molten salt single-tank packed bed regenerator system, the following model assumptions are proposed: (1) For heat transfer and flow of heat storage molten salt, the packed bed is equivalent to an isotropic porous medium; (2) The heat transfer and flow of the heat storage molten salt in the packed bed are both one-dimensional axial; (3) The density and specific heat capacity of heat transfer and storage molten salt are constant, while the viscosity and thermal conductivity are functions of temperature; (4) All packed bed heat storage units are spherical, and heat storage units of the same type have a uniform hydraulic diameter; (5) The phase change heat storage medium is uniformly filled in the phase change heat storage unit, and the volume and physical property changes caused by the solid-liquid phase change are ignored; (6) The melting and solidification processes of the phase change thermal storage material occur within the same temperature range; (7) The thermal properties of the packed bed heat storage unit are all constant; (8) Neglecting contact heat conduction and radiation heat transfer between packed bed heat storage units, neglecting radiation heat transfer between heat storage molten salts, and neglecting heat exchange between the heat storage system and the environment.

[0048] 2. Heat transfer control equations and correlations Based on the above assumptions, a one-dimensional transient heat transfer mathematical model of the molten salt single-tank packed bed thermal regeneration system is established using a hybrid diffusion model (a known model). This model divides the thermal regeneration system into two computational domains, such as... Figure 5 As shown. The first computational domain ( Figure 5 a) is the packed bed region through which the heat-transferring molten salt flows, and the second computational domain ( Figure 5 b) is the internal region of a single packed bed thermal storage unit.

[0049] The transient energy conservation equation for the packed bed region (porous medium) through which the heat-transferring molten salt flows can be written as: (2.1) In the formula, Porosity of the packed bed; For the transfer of heat storage molten salt density; To transfer the specific heat capacity of the heat-storing molten salt; To transfer the temperature of the heat-storing molten salt; For time; The apparent flow rate of the heat-storing molten salt; In the direction of the filling bed height; The effective thermal conductivity of the heat-storing molten salt; The specific surface area of ​​the packed bed; The thermal resistance per unit area for heat transfer between the heat storage molten salt and the packed bed heat storage unit; Temperature of the packed bed heat storage material; The direction of the thermal storage unit radius; denoted as the inner radius of the heat storage unit.

[0050] like Figure 5 As shown in Figure a, the packed bed region can be divided into k different packed layer regions. Since the size of the heat storage units in different packed layers is different, their porosity may also be different. Therefore, the porosity of the packed bed can be expressed as a function of the packed bed height: (2.2) apparent flow rate of heat storage molten salt It can be calculated using the following formula: (2.3) In the formula, The thermal power of the heat storage system; The cross-sectional area of ​​the filling bed; This refers to the bottom outlet temperature of the heat storage system. This refers to the temperature at the top inlet of the heat storage system.

[0051] The specific surface area of ​​a packed bed is the surface area of ​​the heat storage unit per unit volume of the packed bed, which can be expressed as: (2.4) In the formula, This refers to the outer radius of the heat storage unit. It is worth noting that the inner and outer radii of the sensible heat storage unit are the same. That is:

[0052] The thermal resistance per unit area between the heat transfer molten salt and the packed bed heat transfer unit can be expressed by the following formula: (2.5) In the formula, α The convective heat transfer coefficient per unit area between the heat storage molten salt and the packed bed heat storage unit; Let be the thermal conductivity of the encapsulation material. The convective heat transfer coefficient is expressed using an empirical correlation: (2.6) In the formula, For the packed bed Reynolds number (Equation 2.6 only) ≤10 5 (Applicable at times) For the Prandtl number of the filling bed; The thermal conductivity of the heat-storing molten salt; Where is the diameter of the heat storage unit. The Reynolds number and Prandtl number of the packed bed can be expressed by the following formula: (2.7) (2.8) In the formula, The dynamic viscosity of the heat-transferring molten salt.

[0053] The effective thermal conductivity of heat-storing molten salt can be expressed as the sum of its static and dynamic thermal conductivity: (2.9) (2.10) (2.11) In the formula, The effective thermal conductivity of the heat-storing molten salt; This is the static thermal conductivity; The dynamic thermal conductivity; The ratio of the thermal conductivity of the heat storage molten salt to that of the packed bed heat storage material; Let be the shape factor of the filling bed. Both can be expressed by the following formula: (2.12) (2.13) Using the temperature-based enthalpy method, the transient energy conservation equation for a packed bed thermal storage unit can be written as: (2.14) In the formula, Density of the packed bed heat storage material; Specific enthalpy of packed bed heat storage material; The effective thermal conductivity of the packed bed heat storage material; For phase change thermal storage materials, considering the effect of encapsulation volume voids, their density is rewritten as the effective density: (2.15) In the formula, This refers to the volumetric porosity of the package.

[0054] For phase change heat storage materials, their specific enthalpy can be written as a piecewise function of temperature: (2.16) In the formula, The specific heat capacity of the solid state of the phase change thermal storage material; The specific heat capacity of the phase change thermal storage material in liquid state; ... The specific phase change enthalpy of the phase change heat storage material; The phase change temperature range of phase change thermal storage materials; This refers to the melting temperature of the phase change thermal storage material. This refers to the solidification temperature of the phase change thermal storage material. The latent heat of phase change per unit mass of the phase change heat storage material, also known as the latent heat of melting / solidification, is expressed in J / kg.

[0055] The effective thermal conductivity of phase change thermal storage materials can also be written as a piecewise function of temperature: (2.17) In the formula, The solid-state thermal conductivity of the phase change thermal storage material; The liquid thermal conductivity of the phase change thermal storage material; The convective heat transfer enhancement factor can be expressed by the following formula: (2.18) In the formula, A function for filling the Prandtl number of the bed. The shape factor of the phase change thermal storage material; Let Rayleigh number be the phase change thermal storage material. These three factors can be expressed by the following formula: (2.19) (2.20) (2.21) In the formula, The thickness of the liquid phase change material inside the heat storage unit; The diameter of the solid phase change material inside the heat storage unit; It is the acceleration due to gravity; is the volume expansion coefficient of the phase change material.

[0056] For sensible heat storage materials, their specific enthalpy and effective thermal conductivity can be calculated using the first segment of the function calculated by Equations 2.16 and 2.17.

[0057] The pressure drop of the heat-transferring molten salt flowing through the packed bed can be expressed by the following formula: (2.22) In the formula, This is the drag coefficient; Let be the permeability coefficient. Both can be expressed as: (2.23) (2.24) 3. Boundary conditions and initialization During the operation of the thermal storage system, the temperature boundary conditions of the computational domain for the thermal storage molten salt are as follows: (2.25) (2.26) The temperature boundary conditions of the heat storage unit are as follows: (2.27) (2.28) The thermal storage system is in a fully releasing state at the initial moment of the calculation, meaning that the temperature of all thermal storage media is equal to the lower limit of the thermal storage temperature range. (2.29) 4. Calculation methods and steps The model is solved using the Finite Volume Method (FVM), and the meshing of the two computational domains is shown in the corresponding figure in the "Heat Transfer Control Equations and Correlations" section above. The computational domain for heat transfer and storage molten salt is divided along the axial direction into... i A group with the same thickness ( The cylindrical control volume of the thermal storage unit is divided into sections along the radial direction. j A group with the same thickness ( The system is a spherical shell control volume. According to the model assumptions, the external thermal environment of each heat storage unit within the molten salt control volume is the same. Therefore, by calculating the energy conservation equation of a representative heat storage unit within the control volume, the thermal state of all heat storage units within the control volume, and the heat exchange with the molten salt within the control volume, can be determined. The energy conservation equations for the molten salt single-tank packed bed heat storage system consist of Equation 2.1 and... i Formula 2.14 is a coupling composition.

[0058] The time term of the equations is discretized using a fully implicit scheme, the diffusion term using a central difference scheme, and the convection term using a first-order upwind scheme. According to these discretization schemes, equations 2.1 and 2.14 can be written as: (2.30) (2.31) In the formula, Let be the bed porosity of the i-th molten salt fluid control volume; For the first i The volume of the heat storage molten salt control body; For the first i Cross-sectional area of ​​the heat storage molten salt control body; For the first i The first heat storage unit j The volume of each control unit; For the first i The first heat storage unit j The outer surface area of ​​each control body; Let be the inner surface area of ​​the j-th control body within the i-th thermal storage unit; for n At time +1, the... i The molten salt temperature of the fluid control volume; forn At that moment, the i Fluid control volume molten salt temperature; for n +1 hour, j and j +1 Molten salt temperature at the interface of the fluid control volume; for n +1 hour, j and j -1 Molten salt temperature at the interface of the fluid control volume; For the fluid side j , j +1 Axial equivalent thermal conductivity of the interface; for n +1 hour, j +1 adjacent fluid control volume molten salt temperature; For the fluid side j , j -1 Axial equivalent thermal conductivity of the interface; for n +1 hour, j -1 adjacent fluid control volume molten salt temperature; For the first i Control the total solid-liquid heat transfer specific surface area within the body; The solid thermal storage salt wall / packing temperature is the solid phase temperature for interfacial heat transfer. For the first j The molten salt temperature of the fluid control volume is the fluid-side temperature for convective heat transfer. For the first i Density of the unit solid heat storage medium; for n At time +1, the... i thermal storage unit j Enthalpy per unit mass of a solid control volume; for n In the past, the enthalpy per unit mass of the same solid control volume; solid phase j , j +1 Radial interface equivalent thermal conductivity; solid phase j , j -1 Radial interface equivalent thermal conductivity; for n +1 hour, i unit j +1 Solid control body temperature; for n +1 hour, i unit j Solid control volume temperature; for n +1 hour,i unit j -1 solid control body temperature.

[0059] Figure 6 The flowchart of the transient calculation of packed bed thermal storage is shown. Equations 2.30 and 2.31 can both be solved using the tridiagonal matrix algorithm. Within each time step, Equation 2.30 is first solved to obtain the temperature field of the heat transfer molten salt, and some thermal properties of the heat transfer molten salt are updated. The apparent flow rate of the heat transfer molten salt is also updated according to Equation 2.3. Then, this temperature field is used as the temperature boundary condition of Equation 2.31 to solve the internal temperature field of each heat transfer molten salt calculation domain within the thermal storage unit, and some thermal properties of the phase change thermal storage medium are updated. The obtained surface temperatures of each thermal storage unit are then used as the temperature boundary condition of Equation 2.30 to solve the temperature field of the heat transfer molten salt. Equations 2.30 and 2.31 are solved alternately until the temperature field of the heat transfer molten salt and the internal temperature field of each thermal storage unit reach the convergence condition (temperature field residual less than 10). -6 ).

[0060] 5. Model Validation The model is validated by comparing experimental results reported in the literature with numerical results calculated using the above model. Two different examples are then used to verify the applicability of the model to sensible heat packed bed thermal storage systems and phase change packed bed thermal storage systems.

[0061] The first verification example referenced the experimental work of foreign researchers Pacheco et al., and a heat storage capacity of 2.3 MWh was built and tested. t A pilot-scale sensible heat storage system for molten salt packed bed was developed. The structure of this system is essentially the same as that of a single-tank packed bed molten salt system. The system uses a propane heater to heat the extracted cold molten salt and an air cooler to cool the extracted hot molten salt. The system uses a mixture of quartz and gravel at a mass ratio of 2:1 as the sensible heat storage unit in the packed bed. A thermocouple is placed every 15 cm along the axis of the packed bed to measure the temperature of the heat-transferring molten salt.

[0062] The experimental steps for this experiment are as follows: (1) The heat storage molten salt is preheated to 260°C in the salt discharge tank, and then injected into the heat storage tank and heated to 290°C. At this time, the heat storage system is in a state of complete heat release. (2) From a certain moment, the system begins constant power heat storage until the temperature of the heat storage molten salt pumped out by the low temperature molten salt pump exceeds the heat storage cutoff temperature. (3) The system then begins to release heat at a constant power until the temperature of the heat transfer and storage molten salt pumped out by the high-temperature molten salt pump is lower than the heat storage cutoff temperature. (4) After multiple consecutive heat storage-heat release cycles, a complete heat release process is taken as the reference segment for model verification.

[0063] Experimental results of the temperature distribution of the heat-transferring molten salt along the axis are as follows: Figure 7 The hollow symbol is shown. To accurately simulate this exothermic process, the initial temperature distribution of all heat storage media in the system (including the heat transfer molten salt and the packed bed heat storage unit) is uniformly set to the temperature distribution of the heat transfer molten salt at the initial moment of the experiment, as shown below. Figure 7 The red curve in the middle shows the grid numbers for the packed bed region and the regenerator unit, which are 10⁴ and 10, respectively, with a time step of 10 s. The independence of both the grid and the time step was verified. During operation, the Reynolds number of the regenerator fluid was between 10⁴ and 10⁻¹⁰. 0 ~10 1 The simulation results of the temperature distribution of the heat-transferring molten salt along the axis at half-hour intervals are shown as the black curve in the figure. Comparison reveals a high degree of agreement between the simulation and experimental results, with a maximum error of 17.7%. These errors can be attributed to thermocouple measurement errors and model assumptions.

[0064] The second verification example references the experimental work of Nallusamy et al. A small-scale phase change packed bed hot water storage system was constructed and tested. This system simultaneously performs one process of heat storage and release. The system uses solar collectors to heat the extracted cold water and a shower system to cool the extracted hot water. The system uses paraffin wax encapsulated in high-polyethylene as the packed bed phase change heat storage unit. Four thermocouples are arranged at four equal points along the axis of the packed bed to measure the water temperature.

[0065] The initial temperature of the heat storage medium in the heat storage tank is 32℃, at which point the heat storage system is in a state of complete heat release. From a certain moment, the system begins constant mass flow heat storage for 3 hours; this heat storage process is taken as the reference period for model verification. The changes in water temperature over time measured by various thermocouples are as follows: Figure 8 The hollow symbol is shown. The grid numbers for the filled bed region and the regenerator unit are 46 and 30, respectively, with a time step of 10 s. The independence of both the grid and the time step was verified. During operation, the Reynolds number of the regenerator fluid was between 101 and 102. The simulated water temperature at the corresponding location is shown by the black curve in the figure below. By comparison, it can be found that the simulation results are in high agreement with the experimental results, with a maximum error of 9.2%, which can be attributed to the measurement error of the thermocouple and the model assumptions.

[0066] Through the two model verification examples above, it can be concluded that the model has good applicability to simulating the heat storage and release processes of sensible heat packed bed thermal storage systems and phase change packed bed thermal storage systems, and can be used as an effective tool for performance simulation of molten salt single-tank packed bed thermal storage systems.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for establishing a model of a packed bed type cold and heat storage device, characterized in that, Includes the following steps: Based on considering only the heat transfer behavior of the heat storage medium within the packed bed area, and according to the system composition and working principle of the molten salt single-tank packed bed heat storage system, assumptions are made for the model of the packed bed cold and heat storage device. Based on the assumptions, a one-dimensional transient heat transfer mathematical model of a molten salt single-tank packed bed thermal regeneration system is established using a hybrid diffusion model. Solving the one-dimensional transient heat transfer mathematical model yields the energy conservation equations for the molten salt single-tank packed bed thermal regeneration system. Solve the energy conservation equations until the temperature field of the heat storage molten salt and the internal temperature field of each heat storage unit reach the convergence condition, save the calculation results and update the system thermal state.

2. The method for establishing a model of a packed bed type cold and heat storage device according to claim 1, characterized in that, The specific assumptions made for the model of the packed bed type cold and heat storage device are as follows: For heat transfer and flow in heat storage molten salts, a packed bed is equivalent to an isotropic porous medium. The heat transfer and flow of the heat-storing molten salt in the packed bed are both one-dimensional axial. The density and specific heat capacity of heat-storing molten salts are constant, while their viscosity and thermal conductivity are functions of temperature. All packed bed thermal storage units are spherical, and thermal storage units of the same type have a uniform hydraulic diameter; The phase change heat storage medium is uniformly filled in the phase change heat storage unit, and the volume and property changes caused by the solid-liquid phase change are ignored. The melting and solidification processes of phase change thermal storage materials occur within the same temperature range; The thermal properties of the packed bed thermal storage unit are all constant; The contact heat conduction and radiation heat transfer between packed bed heat storage units are ignored, as are the radiation heat transfer between heat storage molten salts and the heat exchange between the heat storage system and the environment.

3. The method for establishing a model of a packed bed type cold and heat storage device according to claim 2, characterized in that, The one-dimensional transient heat transfer mathematical model divides the molten salt single-tank packed bed heat storage system into two computational domains: the first computational domain is the packed bed region through which the heat-transferring molten salt flows, and the second computational domain is the internal region of a single packed bed heat storage unit.

4. The method for establishing a model of a packed bed type cold and heat storage device according to claim 3, characterized in that, The transient energy conservation equation for the packed bed region through which the heat-transferring molten salt flows is as follows: （2.1）； In the formula, Porosity of the packed bed; For the transfer of heat storage molten salt density; To transfer the specific heat capacity of the heat-storing molten salt; To transfer the temperature of the heat-storing molten salt; For time; The apparent flow rate of the heat-storing molten salt; In the direction of the filling bed height; The effective thermal conductivity of the heat-storing molten salt; The specific surface area of ​​the packed bed; The thermal resistance per unit area for heat transfer between the heat storage molten salt and the packed bed heat storage unit; Temperature of the packed bed heat storage material; The direction of the thermal storage unit radius; denoted as the inner radius of the heat storage unit.

5. The method for establishing a model of a packed bed type cold and heat storage device according to claim 4, characterized in that, The transient energy conservation equations for the internal region of a single packed bed thermal regenerator are as follows: （2.14）； In the formula, Density of the packed bed heat storage material; Specific enthalpy of packed bed heat storage material; The effective thermal conductivity of the packed bed heat storage material.

6. The method for establishing a model of a packed bed type cold and heat storage device according to claim 5, characterized in that, The one-dimensional transient heat transfer mathematical model is solved using the finite volume method. The mesh of the two computational domains is as follows: the first computational domain is divided along the axial direction into... i The first is a cylindrical control volume with the same thickness; the second computational domain is divided along the radial direction into two parts. j Each spherical shell control body has the same thickness. According to the model assumption, the external thermal environment of the heat storage units within each heat transfer and storage molten salt control body is the same. Therefore, by calculating the energy conservation equation of a representative heat storage unit within the control body, the thermal state of all heat storage units within the control body, as well as the heat exchange with the heat transfer and storage molten salt within the control body, can be determined. The energy conservation equation set of the molten salt single-tank packed bed heat storage system consists of equation (2.1) and... i Formula (2.14) is a coupled composition.

7. The method for establishing a model of a packed bed type cold and heat storage device according to claim 6, characterized in that, The discretization scheme of the energy conservation equations for a molten salt single-tank packed bed thermal regeneration system is as follows: （2.30）； （2.31）； In the formula, Let be the bed porosity of the i-th molten salt fluid control volume; For the first i The volume of the heat storage molten salt control body; For the first i Cross-sectional area of ​​the heat storage molten salt control body; For the first i The first heat storage unit j The volume of each control unit; For the first i The first heat storage unit j The outer surface area of ​​each control body; Let be the inner surface area of ​​the j-th control body within the i-th thermal storage unit; for n At time +1, the... i The molten salt temperature of the fluid control volume; for n At that moment, the i Fluid control volume molten salt temperature; for n +1 hour, j and j +1 Molten salt temperature at the interface of the fluid control volume; for n +1 hour, j and j -1 Molten salt temperature at the interface of the fluid control volume; For the fluid side j , j +1 Axial equivalent thermal conductivity of the interface; for n +1 hour, j +1 adjacent fluid control volume molten salt temperature; For the fluid side j , j -1 Axial equivalent thermal conductivity of the interface; for n +1 hour, j -1 adjacent fluid control volume molten salt temperature; For the first i Control the total solid-liquid heat transfer specific surface area within the body; The solid thermal storage salt wall / packing temperature is the solid phase temperature for interfacial heat transfer. For the first j The molten salt temperature of the fluid control volume is the fluid-side temperature for convective heat transfer. For the first i Density of the unit solid heat storage medium; for n At time +1, the... i thermal storage unit j Enthalpy per unit mass of a solid control volume; for n In the past, the enthalpy per unit mass of the same solid control volume; solid phase j , j +1 Radial interface equivalent thermal conductivity; solid phase j , j -1 Radial interface equivalent thermal conductivity; for n +1 hour, i unit j +1 Solid control body temperature; for n +1 hour, i unit j Solid control volume temperature; for n +1 hour, i unit j -1 solid control body temperature.

8. The method for establishing a model of a packed bed type cold and heat storage device according to claim 7, characterized in that, Equations (2.30) and (2.31) can both be solved using a tridiagonal matrix algorithm. Within each time step, equation (2.30) is solved first to obtain the temperature field of the heat transfer and storage molten salt, and some thermal properties of the heat transfer and storage molten salt are updated. The apparent flow rate of the heat transfer and storage molten salt is also updated according to equation (2.3). Then, this temperature field is used as the temperature boundary condition of equation (2.31) to solve the internal temperature field of the heat storage unit in the computational domain of each heat transfer and storage molten salt, and some thermal properties of the phase change heat storage medium are updated. The obtained surface temperature of each heat storage unit is then used as the temperature boundary condition of equation (2.30) to solve the temperature field of the heat transfer and storage molten salt. Equations (2.30) and (2.31) are solved alternately until the temperature field of the heat transfer and storage molten salt and the internal temperature field of each heat storage unit reach the convergence condition. Then, the calculation results are saved and the thermal state of the system is updated.

9. A model-building device for a filled bed type cold and heat storage device, characterized in that, include: The first processing unit is used to make assumptions about the model of the packed bed thermal storage device based on the heat transfer behavior of the heat storage medium within the packed bed area only, and according to the system composition and working principle of the molten salt single-tank packed bed heat storage system. The second processing unit is used to establish a one-dimensional transient heat transfer mathematical model of the molten salt single-tank packed bed thermal storage system based on assumptions and using a hybrid diffusion model. The third processing unit is used to solve the one-dimensional transient heat transfer mathematical model, which can obtain the energy conservation equations of the molten salt single-tank packed bed thermal storage system. The fourth processing unit is used to solve the energy conservation equations until the temperature field of the heat storage molten salt and the internal temperature field of each heat storage unit reach the convergence condition, save the calculation results and update the system thermal state.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for establishing a model of a packed bed type cold and heat storage device as described in any one of claims 1-8.

11. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method for establishing a model of a filled bed type cold and heat storage device as described in any one of claims 1-8.

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