Downstream modular packed bed heat storage system and heat storage and heat release control method thereof

Abstract

The invention discloses a downstream modular packed bed heat storage system and a heat storage and release control method thereof.The downstream modular packed bed heat storage system comprises a plurality of heat storage units, a heat source and a load, one end of the heat source is connected with the load through a first main pipeline, and the other end of the heat source is connected with the load through a second main pipeline; a plurality of heat storage units are connected between the first main pipeline and the second main pipeline in parallel, the top end of each heat storage unit is connected with the first main pipeline through a first branch pipeline, and the bottom end of each heat storage unit is connected with the second main pipeline through a second branch pipeline. The first main pipeline is connected with the second branch pipeline of each heat storage unit through a pipeline I; the second main pipeline is connected with a second pipeline, and the second pipeline is connected with the first branch pipeline and the second branch pipeline of each heat storage unit through a bypass pipeline. Valves are arranged in front of and behind each connecting node of the first main pipeline, the second main pipeline, the first branch pipeline, the second branch pipeline, the bypass pipeline, the second pipeline and the first pipeline.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of heat storage, in particular to a downstream modular packed bed heat storage system and a heat storage and heat release control method thereof. BACKGROUND

[0002] The sensible heat storage technology of packed bed has received more and more attention in the field of solar thermal power generation due to its simple operation, low cost and high heat exchange efficiency. Various heat storage systems and methods are disclosed in the prior art, for example, a solar high-temperature modular heat storage system is disclosed in patent CN 1963371A; a single-tank-double-tank composite heat storage system and method for solar thermal power generation are disclosed in patent CN 103292486B; a large-scale solid heat storage system and control method are disclosed in patent CN 119492278A. However, the multi-tank heat storage systems disclosed in the prior art cannot realize the correlation between adjacent storage tanks to adjust the connection mode when the outlet temperature changes during the heat storage and heat release process, so that the heat can be fully utilized during heat storage and the temperature requirement can be met during heat release. The disclosed multi-tank systems are complex, each heat storage unit is equipped with a heat exchanger and a pump, which is large in investment and is not conducive to adjusting the capacity of the system according to the demand. No heat storage and heat release sequence is proposed from the system level.

[0003] Further, the heat storage and heat release processes of the heat storage units disclosed in the prior art have the following problems: the outlet temperature of a heat storage unit gradually increases in the later stage of heat storage, and the heat transfer fluid is not fully heat released, resulting in reduced heat utilization rate. In the later stage of heat release, the outlet temperature gradually decreases, and the heat transfer fluid is not fully heated, which cannot meet the temperature requirement of the load side. The disclosed invention does not involve the quantitative standard of the heat storage unit, such as considering to propose a dimensionless number standard to measure the ratio of the thermal resistance inside the solid particles to the heat transfer resistance between the fluid and the solid. The heat transfer and resistance characteristics of the packed bed heat storage unit are obtained by quantitative calculation. SUMMARY

[0004] In order to solve the technical problems in the prior art, the present application discloses a downstream modular packed bed heat storage system and a heat storage and heat release control method thereof.

[0005] In order to achieve the above-mentioned purposes, the technical solutions adopted by the present application are as follows: In a first aspect, the present application provides a downstream modular packed bed heat storage system, comprising a plurality of heat storage units, a heat source and a load, One end of the heat source is connected with the load through a first main pipeline, and the other end of the heat source is connected with the load through a second main pipeline; a plurality of heat storage units are connected in parallel between the first main pipeline and the second main pipeline, and the top end of each heat storage unit is connected with the first main pipeline through a first branch pipeline, and the bottom end of each heat storage unit is connected with the second main pipeline through a second branch pipeline; The first main pipeline is connected with the second branch pipeline of each heat storage unit through a pipeline one; The second main pipeline is connected with a pipeline two, and the pipeline two is connected with the first branch pipeline and the second branch pipeline of each heat storage unit through a bypass pipeline; Valves are arranged in front of and behind each connection node of the first main pipeline, the second main pipeline, the first branch pipeline, the second branch pipeline, the bypass pipeline, the pipeline two and the pipeline one.

[0006] As a further technical solution, a pressurizing pump is arranged on the second main pipeline; by controlling the opening and closing of the valves, the series connection or the parallel connection of the plurality of heat storage units can be realized.

[0007] As a further technical solution, the Peclet number of the particles in the heat storage unit is ; wherein h sf is the heat transfer coefficient between the solid particles and the heat transfer fluid; d is the equivalent diameter of the solid particles, and the equivalent diameter calculation formula is ; V is the volume; and k s is the thermal conductivity of the solid particles.

[0008] In the second aspect, based on the above-mentioned down-flow modular packed bed heat storage system, the application further provides a heat storage and release control method, which is specifically as follows: When the heat storage and release demand is small, the operation of a single heat storage unit or the series connection operation of a plurality of heat storage units is realized by controlling the opening and closing of the valves; when the heat storage and release demand is large, the parallel connection operation of the plurality of heat storage units is realized; when the series connection operation is realized, the judgment standard for the communication between adjacent heat storage units is that, when the heat is stored, the outlet temperature of the previous unit rises to , and the previous unit is connected to the inlet of the next heat storage unit; when the heat is released, the outlet temperature of the previous unit drops to , and the previous unit is connected to the next heat release unit, wherein the temperature relationship is as follows:

[0009]

[0010] As a further technical solution, when only one of the heat storage units needs to store heat, only the valves on the first main pipeline, the second main pipeline and the first branch pipeline and the second branch pipeline of the corresponding heat storage unit are opened, and the other valves are closed.

[0011] As a further technical solution, when multiple heat storage units are needed to be connected in series for heat storage, the first heat storage unit is first used for heat storage; when the temperature of the fluid at the outlet of the first heat storage unit rises to a set value, the fluid enters the second heat storage unit for heat storage; when the temperature of the fluid at the outlet of the second heat storage unit rises to a set value, the third heat storage unit is opened for heat storage; in this way, the heat storage of multiple heat storage units is sequentially pushed forward; and in the whole process, when a certain heat storage unit is completely filled with heat, the valve on the branch thereof is closed.

[0012] As a further technical solution, when only one of the heat storage units is needed for heat release, the fluid flows out from the second main pipeline, sequentially flows through the pipeline two, the corresponding heat storage unit, and the pipeline one, and then is connected to the load to realize heat release.

[0013] As a further technical solution, when multiple heat storage units are needed to be connected in series for heat release, the fluid flows out from the second main pipeline, sequentially flows through the pipeline two, enters the top of the first heat storage unit, and realizes heat release of the first heat storage unit; when the temperature of the fluid at the outlet of the first heat storage unit decreases to a set temperature during the heat release process, the valve of the second heat storage unit is opened, the fluid flows out from the bottom of the first heat storage unit, enters the top of the second heat storage unit, and then flows out from the bottom of the second heat storage unit, thereby realizing heat release of the second heat storage unit; in this way, the heat release of multiple heat storage units is sequentially pushed forward, and when a certain heat storage unit is completely released, the valve on the branch thereof is closed.

[0014] As a further technical solution, when multiple heat storage units are needed to be connected in parallel for heat storage, the valves on the first branch and the second branch corresponding to each heat storage unit and the valves on the first main pipeline and the second main pipeline are simultaneously opened, and other valves are closed, thereby realizing heat storage. As a further technical solution, when multiple heat storage units are needed to be connected in parallel for heat release, the valves on the first branch and the second branch corresponding to each heat storage unit and the valves on the first main pipeline and the second main pipeline and the valves on the pipeline one and the pipeline two are simultaneously opened, and other valves are closed, thereby realizing heat release.

[0015] The beneficial effects of the present application are as follows: 1. The heat storage system proposed in the present application can be operated individually, in series or in parallel with other units; when the heat storage and release demand is small, only the inlet and outlet valves of a single heat storage unit are opened for heat storage and release; however, since the heat storage and release rate of a single heat storage unit is always limited, when there is a large amount of remaining photothermal resources, i.e., a large heat storage demand, or a large gap in photothermal resources, i.e., a large heat release demand, the inlet and outlet valves of multiple heat storage units can be opened to simultaneously complete the heat storage or release task, so as to meet the large-power heat storage and release demand.

[0016] 2. The heat storage system has only one molten salt pump installed in the main pipeline of the system, which can send molten salt to all heat storage units by controlling the opening and closing of the valve. The control valve of the heat storage unit that needs to participate in heat storage is opened. The molten salt pump is installed at the cold end of the system, and only low-temperature molten salt passes through the pump at all times, ensuring that the pump operates more safely and reliably. At the same time, the system disclosed by the present application has only one heat exchanger installed in the main pipeline to supply heat to the heat load. Overall, the system is simple, stable and reliable, has low investment and operating costs, and is more conducive to system expansion; 3. In the heat storage process, when the temperature of the outlet fluid rises to a certain value, the fluid of the previous heat storage unit is connected to the next unit to continue to release heat. When the previous heat storage unit is completely filled with heat, the inlet and outlet valves are closed, and the high-temperature heat transfer fluid directly enters the next heat storage unit. In this way, the heat storage is completed by advancing forward. Similarly, in the heat release process, when the temperature of the fluid at the outlet of the previous unit decreases to a certain temperature, it is connected to the next unit to continue to absorb heat. Since the heat preservation effect of the internal unit is always better than that of the external unit in the entire system, the internal unit is given priority in heat storage. Therefore, when a unit completes heat storage, the heat dissipation to the environment is minimized. Similarly, when releasing heat, the external unit should be given priority. Similarly, excessive heat loss can be avoided. By this way, the heat loss is minimized to improve the efficiency; at the same time, the present application has quantitative standards for independent heat storage units, and the Biot number criterion is proposed to avoid excessive temperature difference between the inside and outside of the solid particles. The quantitative calculation of the resistance and heat transfer of the heat storage unit is given as a design reference to reduce resistance, improve efficiency, and reduce investment cost.

[0017] 4. The present application has quantitative standards: the Biot number criterion is proposed to avoid excessive temperature difference between the inside and outside of the solid particles; and the quantitative calculation of the heat storage unit is given as a design reference. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The overall structure of the heat storage system disclosed in the present application is shown in the figure; Figure 2(a) is a top view of the heat storage process of a modular heat storage system; Figure 2(b) is a top view of the heat release process of a modular heat storage system Figures 3(a) and 3(b) are top views of a heat storage system composed of multiple modules; Figure 4(a) is a schematic diagram of the heat storage process of adjacent heat storage units; Figure 4(b) is a schematic diagram of the heat release process of adjacent heat storage units; Figure 5 Figure 1 is a schematic diagram of a first unit heat storage device; Figure 6 Figure 2 is a schematic diagram of the first and second unit heat storage. Figure 7 schematic diagram of heat storage of the second unit; Figure 8 schematic diagram of heat release of the first unit; Figure 9 schematic diagram of heat release of the first and second units; Figure 10 schematic diagram of heat release of the second unit; Figure 11 schematic diagram of heat storage in parallel; Figure 12 schematic diagram of heat release in parallel; Figure 13 trend chart of outlet temperature change with time during heat storage and release; Figure 14 trend chart of pressure drop of fluid flowing through the packed bed area with Peclet number; Figure 15 trend chart of heat storage and release amount and heat storage and release efficiency of fluid flowing through the packed bed area with Peclet number; Fig. 1, valve; 2, valve; 3, valve; 4, valve; 5, valve; 6, valve; 7, valve; 8, valve; 9, valve; 10, valve; 11, valve; 12, valve; 13, valve; 14, valve; 15, valve; 16, valve; 17, valve; 18, valve; 19, valve; 20, valve; 21, valve; 22, valve; 23, valve; 24, valve; 25, valve; 26, valve; 27, valve; 28, valve; 29, valve; DETAILED DESCRIPTION It should be noted that the following detailed description is merely exemplary and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0019] It should be noted that the terms used herein are merely for the purpose of describing specific embodiments and are not intended to limit exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and it should be further understood that the terms "comprise" and / or "include" as used herein specify the presence of features, steps, operations, devices, components and / or combinations thereof; In order to realize the modular heat storage and its operation process according to the present application, the present embodiment also designs a heat storage and release system as shown in Fig. 1. Figure 1The whole system shown comprises a heat source, heat storage and a load; the pipelines mainly comprise four parts: the red pipeline is the main pipeline (the upper part is the first main pipeline and the lower part is the second main pipeline), the green pipeline is the branch pipeline connecting each heat storage unit and the main pipeline (the upper part is the first branch pipeline and the lower part is the second branch pipeline), the blue pipeline comprises two pipelines, namely pipeline one and pipeline two, and the yellow pipeline is the bypass pipeline connecting each heat storage unit and the series pipeline; specifically, the connection mode is as follows: One end of the heat source is connected with the load through the first main pipeline, and the other end of the heat source is connected with the load through the second main pipeline; a plurality of heat storage units are connected in parallel between the first main pipeline and the second main pipeline, and the top end of each heat storage unit is connected with the first main pipeline through the first branch pipeline, and the bottom end of each heat storage unit is connected with the second main pipeline through the second branch pipeline; The first main pipeline is connected with the second branch pipeline of each heat storage unit through the pipeline one; The second main pipeline is connected with a pipeline two, and the pipeline two is connected with the first branch pipeline and the second branch pipeline of each heat storage unit through a bypass pipeline; Valves are arranged on the first main pipeline, the second main pipeline, the first branch pipeline, the second branch pipeline, the bypass pipeline, the pipeline two and the pipeline one; meanwhile, a valve is arranged in front of the node where the bypass pipeline is connected with the first branch pipeline.

[0020] Specifically, the operation process is as follows: high-temperature fluid from a solar heat absorption field and other heat sources meets the heat required by the power load, and if there is surplus heat, part of the high-temperature fluid flows into the packed bed heat storage unit from the top, and in the process of flowing downward, the heat is transferred to the solid particles and stored, and the low-temperature fluid after heat release flows out from the bottom of the heat storage unit and returns to the heat absorption field to be reheated. If the temperature of the outlet of the first heat storage unit rises, the heat transfer medium flowing out from the bottom of the first heat storage unit is sent to the top inlet of the next heat storage unit through another pipeline to continue the heat release of the low-temperature solid packing particles.

[0021] When the light heat cannot meet the power generation demand of the load side, the heat stored in the heat storage unit can serve as a supplementary heat source, at this time, the low-temperature heat transfer fluid enters from the top of the heat storage unit, absorbs heat from the solid particles in the process of flowing downward, and flows out from the bottom of the heat storage unit after the temperature rises, and together with the high-temperature fluid from the solar heat absorption field, provides the required heat for the load.

[0022] When the temperature of the heat transfer medium flowing out of the bottom of the heat storage unit decreases as the exothermic process proceeds, the fluid flowing out of the bottom outlet of the heat storage unit is led to the top inlet of the next heat storage unit through a bypass pipeline to continue to absorb heat in the next unit, and the high-temperature fluid flowing out of the bottom outlet of the next unit is sent to the load to release heat, so that the heat storage system can maintain a relatively stable output power.

[0023] One of the heat storage units is a cylindrical heat storage unit, and the heat storage device is composed of a heat storage unit, solid heat storage particles, and fluid inlet and outlet pipelines. In order to make the fluid flow in the heat storage unit more uniform and stable, a flow equalizer is installed at the top and bottom of the heat storage unit body. Meanwhile, a metal support for supporting the solid heat storage particles is also installed at the bottom of the heat storage unit. The spherical heat storage particles are stacked in the cylindrical heat storage unit to form a packed bed, and the gaps formed by mutual support thereof serve as channels for fluid flow and heat exchange.

[0024] For a single heat storage unit, the heat storage process is as follows: high-temperature heat transfer medium with a temperature of T ch,in flows in from the upper flow channel, enters the packed bed area through the flow equalizer, and in the packed bed area, the high-temperature fluid heats the solid particles to transfer heat energy to the heat storage balls in the form of sensible heat. The cooled low-temperature fluid flows out of the lower flow channel. When the heat storage process is completely finished, the heat storage device is filled with heat transfer fluid and solid particles with a temperature of T ch,in .

[0025] The heat release process is as follows: low-temperature fluid with a temperature of T dis,in enters from the upper flow channel, absorbs heat from the solid particles, and then flows out of the bottom flow channel of the heat storage unit. When the heat release process of the heat storage unit is completely finished, the heat storage unit is filled with heat transfer fluid and solid heat storage particles with a temperature of T dis,in .

[0026] Figure 2(a) and Figure 2(b) show a top view of a modular thermal storage system. A circle represents a thermal storage unit. In order to minimize the footprint and heat dissipation area, the cylindrical thermal storage units are arranged in a staggered manner to form a hexagonal area as shown. For a thermal storage unit with a diameter of 20 m and a height of 15 m, the thermal storage capacity is about 720 MWh. For a seasonal large-capacity long-period thermal storage requirement of 100 GWh, about 140 single-tank thermal storage units are needed to form a large-scale thermal storage system. The specific thermal storage and release methods are as follows: the red units in Figure 2(a) are the units that have completed thermal storage, the yellow units are the units that are currently being stored, and the blue units are the units that are to be stored. During thermal storage, the units are heated in sequence until the thermal storage process is complete. Since the thermal insulation effect of the inner units is always better than that of the outer units in the entire system, the inner units are given priority during thermal storage, so that when a unit completes thermal storage, the heat dissipation to the environment is minimized. Similarly, during heat release, the outer units are given priority, and the heat stored in the outer units is also prevented from being excessively dissipated.

[0027] Meanwhile, the form of the entire thermal storage system can also be diverse. As can be seen from the pipe arrangement on the schematic diagram of the thermal storage system, the pipes of the system can be completely arranged on the periphery of the system, and there is no need to arrange pipes for each unit in the gaps between the thermal storage units. Therefore, the thermal storage units can be designed in a closely arranged form, as shown in Figure 3(a) and Figure 3(b). When there is a large thermal storage power requirement and rapid thermal storage is needed, multiple thermal storage units can be simultaneously connected in parallel for thermal storage.

[0028] Figure 4(a) and Figure 4(b) show the working mode of two adjacent thermal storage units during thermal storage and heat release. During thermal storage, when the temperature of the outlet fluid rises to a certain value, the fluid of the previous thermal storage unit is connected to the next unit to continue to release heat. When the previous thermal storage unit is completely filled with heat, the inlet and outlet valves are closed, and the high-temperature heat transfer fluid is directly connected to the next thermal storage unit. In this way, the thermal storage process is completed by advancing forward in sequence.

[0029] Similarly, during heat release, when the temperature of the outlet fluid of the previous unit decreases to a certain temperature, the fluid is connected to the next unit to continue to absorb heat. In this way, the heat carried by the fluid can be fully utilized during thermal storage to improve the thermal storage efficiency, and the stable power output can be maintained during heat release to meet the requirements of the load side for the temperature of the heat source.

[0030] The switching temperature criterion is:

[0031]

[0032] In the formula, the physical meanings of the symbols are as follows: The switching temperature during thermal storage; The switching temperature during heat release; The temperature of the molten salt at the inlet during thermal storage, i.e., the temperature of the high-temperature molten salt; The temperature of the inlet molten salt during heat release is the temperature of the low-temperature molten salt. The first formula above describes the switching standard during thermal storage, that is, the outlet molten salt temperature of the previous unit during thermal storage is changed from the temperature of the low-temperature molten salt (…). Gradually rising to When that happens, it is connected to the inlet of the next thermal storage unit; the second formula describes the switching standard during heat release, where the outlet molten salt temperature of the previous unit during heat release is determined by the temperature of the high-temperature molten salt ( Gradually decreased to When the heat is released, it is connected to the next heat release unit. This is mainly due to the limitations of the heat source and the temperature of the heat used, so that the outlet temperature is not too high during heat storage, which would result in the heat not being fully utilized, and the outlet temperature is not too low during heat release, which would fail to meet the heat demand.

[0033] The heat storage and release process of the above system is explained below with reference to the specific accompanying drawings: The thermal storage process is as follows: When the first thermal storage unit stores heat: (e.g.) Figure 5 As shown, valves 1, 2, 5, 6, 7, 8, 28, and 29 are open; the remaining valves are closed. Specifically, the open valves are: Figure 5 Valves on solid lines; The flow direction of the high-temperature fluid is as follows: the high-temperature fluid coming out of the heat source first flows through valve 1 and valve 28 to heat the load. After heating the load, the low-temperature fluid passes through valve 29 and valve 2 and then re-enters the heat source for heating. When the high-temperature fluid meets the heat requirements of the load, the heat of the high-temperature fluid will be stored in the heat storage unit. At this time, part of the high-temperature fluid flows through valve 1, valve 5, and valve 6 to enter the first heat storage unit for heat storage. After heat storage is completed, it comes out of the first heat storage unit and re-enters the heat source for heating and circulation through valve 7, valve 8, pump, and valve 2. When the temperature of the fluid at the outlet of the first thermal storage unit rises to a certain value, its outlet is connected to the inlet of the second thermal storage unit: For example... Figure 6 As shown, Figure 6 The diagram shows the state of two thermal storage units during thermal storage. In this state, valves 1, 2, 4, 5, 6, 7, 15, 16, 17, 18, 19, 20, 28, and 29 are open, and the remaining valves are closed. Specifically, the open valves are: Figure 6The valves on the solid line; the specific process is as follows: the high-temperature fluid coming out of the heat source first flows through valve 1 and valve 28 to heat the load. After heating the load, the low-temperature fluid passes through valve 29 and valve 2 and then re-enters the heat source for heating. When the high-temperature fluid meets the heat requirements of the load, the heat of the high-temperature fluid will be stored in the heat storage unit. At this time, part of the high-temperature fluid flows through valve 1, valve 5, and valve 6 to enter the first heat storage unit. When the temperature of the fluid at the outlet of the first heat storage unit rises to a certain value, valves 7, 4, 10, 20, 19, 18, and 15 are opened, and the fluid enters the second heat storage unit for heat storage. After the second heat storage unit has completed heat storage, it re-enters the heat source through valve 16, valve 17, as well as the pump and valve 2 for heating and circulation. When the first thermal storage unit is fully filled with heat, the valves associated with the first thermal storage unit are closed, and the high-temperature fluid is directly connected to the second thermal storage unit: For example... Figure 6 As shown, in this state: valves 1, 2, 14, 15, 16, 17, 28, and 29 are open, and the remaining valves are closed; specifically, the open valves are... Figure 7 Valves on solid lines; When the outlet temperature of the second thermal storage unit rises to a certain value, its outlet is connected to the third thermal storage unit. The specific opening mode is the same as that for the first and second thermal storage units. Figure 6 ); and so on; to complete the thermal storage of all thermal storage units. The system's heat release process is as follows: When the first thermal storage unit releases heat, valves 1, 2, 3, 6, 7, 11, 21, 28, and 29 are opened, and the remaining valves are closed. The specific valves that are opened are... Figure 8 The valves on the solid line; after the low-temperature fluid flows out from the load valve 29, part of it enters the heat source for heating through the pump body and valve 2; the other part enters the first heat storage unit for heating through valve 3 and valve 6 in sequence. The heated fluid enters the load through valve 7, valve 11, valve 21 and valve 28 to heat the load. When the temperature of the outlet fluid in the first thermal storage unit drops to a certain temperature during the heat release process, its outlet is connected to the heat release inlet of the second unit, such as... Figure 9 As shown; valves 1, 2, 3, 4, 6, 7, 15, 16, 18, 19, 20, 21, 28, and 29 are open, and the remaining valves are closed; the specific open valves are... Figure 8The valve on the solid line; the specific process is: after the low-temperature fluid flows out from the valve 29 of the load, part of the low-temperature fluid enters the heat source through the pump body and the valve 2 for heating; another part of the low-temperature fluid enters the first heat storage unit for heating through the valve 3, the valve 6, and the valve 7, the valve 4, the valve 10, the valve 20, the valve 19, the valve 18, and the valve 15 are opened when the temperature of the fluid at the outlet of the first heat storage unit decreases to a certain temperature, the second heat storage unit is entered for heat absorption; when the temperature of the fluid at the outlet of the second heat storage unit decreases to a certain temperature, the third heat storage unit can be opened for heat absorption according to the same method, and so on, and the fluid flowing out of the last heat storage unit enters the load through the pipeline 1 and the valve 8 to heat the load; When the first unit completely releases heat, the low-temperature fluid can be directly connected to the second unit for heat absorption. As shown in Figure 10 The valve 1, the valve 2, the valve 3, the valve 15, the valve 16, the valve 18, the valve 21, the valve 28, and the valve 29 are opened, and the remaining valves are closed; wherein the opened valves are specifically Figure 9 The valve on the solid line; the specific process is: after the low-temperature fluid flows out from the valve 27 of the load, part of the low-temperature fluid enters the heat source through the pump body and the valve 2 for heating; another part of the low-temperature fluid enters the second heat storage unit for heating through the valve 3, the valve 12, the valve 18, and the valve 15, and the fluid after heating enters the load through the valve 16, the valve 21, and the valve 28 to heat the load; Meanwhile, the heat storage system provided by the embodiment can also adopt a multi-tank parallel connection mode for heat storage and heat release, as shown in Figure 11 It is a schematic diagram of parallel heat storage; Figure 12 It is a schematic diagram of parallel heat release; as shown in Figure 11 When the first heat storage unit and the second heat storage unit are in parallel heat storage, the valve 1, the valve 2, the valve 5, the valve 6, the valve 7, the valve 8, the valve 14, the valve 15, the valve 16, the valve 17, the valve 28, and the valve 29 are opened, and the remaining valves are closed; wherein the opened valves are specifically Figure 10The valves on the solid line; the specific process is as follows: the high-temperature fluid coming out of the heat source first flows through valve 1 and valve 28 to heat the load. After heating the load, the low-temperature fluid passes through valve 29 and valve 2 and then re-enters the heat source for heating. When the high-temperature fluid meets the heat requirements of the load, the heat of the high-temperature fluid will be stored in the heat storage unit. At this time, part of the high-temperature fluid flows through valve 1, valve 5, and valve 6 to enter the first heat storage unit. After exiting the first heat storage unit, it passes through valve 7, valve 8, pump, and valve 2 and re-enters the heat source for heating and circulation. At the same time, part of the high-temperature fluid flows through valve 1, valve 14, and valve 15 to enter the second heat storage unit. After exiting the bottom of the second heat storage unit, it passes through valve 16, valve 17, pump, and valve 2 and re-enters the heat source for heating and circulation. like Figure 12 As shown, when the first and second thermal storage units are connected in parallel to release heat, valves 1, 2, 3, 6, 7, 8, 11, 21, 12, 18, 14, 15, 16, 28, and 29 are closed; the remaining valves are closed. Specifically, the open valves are: Figure 12 The valves on the solid line. The specific process is as follows: After the cryogenic fluid flows out from valve 27 of the load, a portion of it passes through the pump body and valve 2 to enter the heat source for heating; simultaneously, another portion passes through valves 3 and 6 in sequence to enter the first heat storage unit for heating. The heated fluid then passes through valves 7, 11, 21, and 28 to enter the load and heat it. Meanwhile, another portion passes through valves 3, 12, 18, and 15 in sequence to enter the second heat storage unit for heating. The heated fluid then passes through valves 16, 21, and 28 to enter the load and heat it. Furthermore, in packed bed thermal storage tanks, the heat carried by the heat transfer fluid is first transferred to the surface of the solid particles, and then transferred to the center of the particles through thermal conduction. In order to transfer heat from the outer surface to the center with a small temperature gradient and avoid excessive temperature difference between the inside and outside of the particles, which would reduce the heat storage and release efficiency, a dimensionless criterion for estimating the relative importance of the internal thermal resistance of the particles, namely the Biot number, is proposed, which is defined as follows:

[0034] Among them, h sf Let d be the heat transfer coefficient between the solid particles and the heat transfer fluid, and d be the diameter of the solid particles. The formula for calculating the equivalent diameter is: V is the volume; k s The thermal conductivity of the solid particles; In order to meet the above requirements, in the heat transfer fluid is molten salt, solid particles material is steel slag, the ratio of the solid particle thermal resistance described by Peclet number and the convective heat transfer resistance should be 0.339.

[0035] Further, the test process of resistance and heat transfer characteristics of each heat storage unit is as follows, wherein the resistance characteristic analysis is as follows: The pressure drop of the fluid flowing through the packed bed area changes with the Peclet number as shown in the figure Figure 14 It can be seen from the figure that when the Peclet number in the packed bed is 0.238, 0.339, 0.42 and 0.491 respectively, the pressure drop of the heat transfer fluid flowing through the packed bed area is 15.08, 4.07, 1.95 and 1.16 Pa respectively. It can be seen that when the Peclet number increases from 0.238 to 0.491, the pressure drop decreases rapidly at first, and then the decreasing amplitude of the pressure drop becomes smaller and smaller as the Peclet number increases.

[0036] The analysis process of the heat transfer characteristics is as follows: As the Peclet number increases, the heat storage and release gradually decrease. When the Peclet number is 0.238, the heat storage is 484.9 MW and the heat release is 428.4 MW, and when the Peclet number is 0.491, the heat storage is 438.5 MW and the heat release is 294.4 MW. From the heat storage and release efficiency curves shown in the figure Figure 15 It can be seen that the heat storage and release efficiency decreases approximately linearly as the Peclet number increases, and the heat release efficiency decreases faster. When the Peclet number is 0.238, the heat storage and release efficiency is 0.94 and 0.83 respectively, and when the Peclet number is 0.491, the heat storage and release efficiency is 0.85 and 0.57 respectively.

[0037] The above only describes the preferred embodiments of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A co-current modular packed bed thermal storage system, characterized in that, Includes multiple thermal storage units, heat sources, and loads. One end of the heat source is connected to the load through a first main pipeline, and the other end of the heat source is connected to the load through a second main pipeline; multiple heat storage units are connected in parallel between the first main pipeline and the second main pipeline, and the top of each heat storage unit is connected to the first main pipeline through a first branch pipeline, and the bottom of each unit is connected to the second main pipeline through a second branch pipeline. The first main pipeline is connected to the second branch pipeline of each thermal storage unit through pipeline one; The second main pipeline is connected to a second pipeline, and the second pipeline is connected to the first branch pipeline and the second branch pipeline of each thermal storage unit through a bypass pipeline. Valves are installed before and after each connection node of the first main pipeline, the second main pipeline, the first branch pipeline, the second branch pipeline, the bypass pipeline, pipeline two, and pipeline one.

2. The co-current modular packed bed thermal storage system as described in claim 1, characterized in that, A booster pump is installed in the second main pipeline; multiple thermal storage units can be connected in series or in parallel by controlling the opening and closing of each valve.

3. The co-current modular packed bed thermal storage system as described in claim 1, characterized in that, Biwo number of particles inside the thermal storage unit ; where h sf Let be the heat transfer coefficient between the solid particles and the heat transfer fluid; d is the equivalent diameter of the solid particles, calculated using the formula: V is the volume; k s is the thermal conductivity of the solid particles.

4. The method for controlling heat storage and release in a co-current modular packed bed thermal storage system as described in any one of claims 1-3, characterized in that, as follows: When the demand for heat storage and release is small, the operation of a single heat storage unit or multiple heat storage units in series is achieved by controlling the opening and closing of valves; when the demand for heat storage and release is large, multiple heat storage units are operated in parallel; when operating in series, the criterion for determining whether adjacent heat storage units are connected is: when storing heat, the outlet temperature of the previous unit rises to... When heat is released, it is connected to the inlet of the next thermal storage unit; when heat is released, the outlet temperature of the previous unit drops to... When connected to the next heat release unit, the temperature relationship is as follows: 。 5. The control method for the co-current modular packed bed thermal storage system as described in claim 4, characterized in that, When only one thermal storage unit is needed for thermal storage, simply open the valves on the first main pipeline, the second main pipeline, and the first and second branch pipelines of the corresponding thermal storage unit, and close the other valves.

6. The control method for the co-current modular packed bed thermal storage system as described in claim 4, characterized in that, When multiple thermal storage units need to be connected in series for thermal storage, the first thermal storage unit starts thermal storage. When the temperature of the fluid at the outlet of the first thermal storage unit rises to a set value, the fluid enters the second thermal storage unit for thermal storage. When the temperature of the fluid at the outlet of the second thermal storage unit rises to a set value, the third thermal storage unit is opened for thermal storage. This process is continued sequentially to complete the thermal storage of multiple thermal storage units. During the entire process, when a thermal storage unit is fully filled with heat, the valve on its branch is closed.

7. The control method for the co-current modular packed bed thermal storage system as described in claim 4, characterized in that, When only one of the thermal storage units is needed to release heat, the fluid flows out from the second main pipeline, then flows through pipeline two, the corresponding thermal storage unit, and pipeline one in sequence; and then it is connected to the load to release heat.

8. The control method for the co-current modular packed bed thermal storage system as described in claim 4, characterized in that, When multiple thermal storage units need to be connected in series for heat release, the fluid flows out from the second main pipeline, then flows through the second pipeline in sequence, and enters the top of the first thermal storage unit to release heat. When the temperature of the outlet fluid of the first thermal storage unit drops to the set temperature during the heat release process, the valve of the second thermal storage unit is opened. The fluid comes out from the bottom of the first thermal storage unit, enters the top of the second thermal storage unit, and then flows out from the bottom of the second thermal storage unit to release heat. This process is continued to advance in sequence to complete the heat release of multiple thermal storage units. When a thermal storage unit has completely released heat, the valve on its branch is closed.

9. The control method for the co-current modular packed bed thermal storage system as described in claim 4, characterized in that, When multiple thermal storage units need to be connected in parallel for thermal storage, the valves on the first and second branches corresponding to each thermal storage unit, as well as the valves on the first and second main pipelines, are opened simultaneously, while the other valves are closed to perform thermal storage.

10. The control method for the co-current modular packed bed thermal storage system as described in claim 4, characterized in that, When multiple thermal storage units need to release heat in parallel, the valves on the first and second branches corresponding to each thermal storage unit, as well as the valves on the first and second main pipelines, and the corresponding valves on pipeline one and pipeline two, are opened simultaneously, while other valves are closed to release heat.

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