Multi-zone gas closed cycle heat exchange method for large solid heat storage device

Abstract

The application discloses a multi-partition gas closed cycle heat exchange method of a large solid heat storage device, and belongs to the technical field of industrial energy storage and heat exchange. The method divides a heat storage silo into multiple independently controlled partitions and is equipped with independent flow regulating valves. A distributed temperature measurement system is used to collect temperatures in real time and calculate a radial temperature uniformity index TUI. Based on a flow resistance balance weight model, the air flow of each partition is dynamically distributed. A controller is used to realize closed loop regulation of the flow to suppress the wall channeling effect. In addition, sound waves are introduced to excite and strengthen heat transfer in the low flow rate heat exchange dead zone. The application can control the radial temperature difference of the heat storage silo to be within 20 DEG C, the TUI index is stably above 0.95, the effective heat capacity is increased from 75% to above 93%, and the device can support stable operation of a wide load of 10% to 100%. The application can be widely applied to large solid heat storage systems such as photovoltaic power stations and large capacity long time energy storage of power grid sides.

Description

Technical Field

[0001] This invention belongs to the field of industrial energy storage and heat exchange technology, specifically relating to a multi-zone gas closed-loop heat exchange method for a large solid thermal energy storage device. It can be widely applied to large solid thermal energy storage systems such as molten salt tower solar thermal power plants, grid-side large-capacity long-term energy storage, and industrial waste heat recovery and utilization. Background Technology

[0002] Under the strategic backdrop of dual-carbon goals, the proportion of new energy power generation such as wind power and photovoltaic power continues to increase. Large-capacity long-term energy storage technology has become the core support for solving the problems of intermittency and volatility of new energy and achieving the integration of new energy and the safe and stable operation of the power grid. Among them, solid-filled bed thermal energy storage technology has become the mainstream technical route for GWh-level ultra-large-scale long-term energy storage scenarios due to its low cost of thermal storage media, high safety, wide operating temperature range, and long system life.

[0003] Currently, ultra-large solid thermal energy storage devices in the industry generally adopt cylindrical silo structures with diameters of 20m-50m, using air as the heat exchange medium and achieving heat charging and releasing of the storage medium through closed-loop gas circulation. However, in engineering applications, this type of device faces four major unresolved core technical bottlenecks: First, significant wall channeling effect and extremely poor temperature field uniformity. When gas flows within a porous medium-filled bed, it tends to flow along areas with higher porosity on the silo wall, resulting in severe lag in heat exchange in the central region of the silo. During the charging and releasing process, the radial temperature difference between the center and the wall can reach over 200℃, and the effective heat capacity of the thermal energy storage device can only reach about 75%, leaving a large amount of storage space unutilized. Second, high risk of structural thermal stress damage. Extremely uneven temperature fields generate enormous shear thermal stress between the refractory lining and the steel structure wall of the silo. Long-term hot and cold cycle operation can lead to refractory brick detachment and cracking at the welded joints of the wall, seriously affecting the service life and operational safety of the device and significantly increasing maintenance costs. Third, severely insufficient wide-load regulation capability. Traditional equipment employs a single air inlet and a fixed gas distribution structure, which cannot adapt to the wide load adjustment requirements of 10%-100%. Under low load conditions, the total gas flow rate decreases, the apparent flow velocity within the packed bed becomes too low, the flow field collapses, and the heat exchange efficiency drops sharply, failing to meet the operational requirements of renewable energy consumption and grid peak shaving. Fourth, heat exchange dead zones cannot be effectively managed. After long-term operation, problems such as ash accumulation and particle compaction of the heat storage medium may occur in some areas, forming low-flow-rate heat exchange dead zones. Existing technologies cannot achieve accurate identification and efficient management of dead zones. Long-term operation can lead to local hot spots, continuous decay of heat storage capacity, and even safety accidents such as medium sintering.

[0004] To address the aforementioned issues, some improved solutions for zoned air distribution have emerged in existing technologies, but they generally suffer from the following drawbacks: a quantitative evaluation system for temperature field uniformity has not been established, closed-loop feedback control logic is lacking, and the flow resistance differences caused by temperature changes cannot be dynamically compensated; only air distribution plates with fixed apertures are used, which cannot adaptively suppress hot airflow short-circuiting; and for heat exchange dead zones, there are no efficient and non-contact methods to enhance heat exchange, thus failing to fundamentally solve the aforementioned technical deficiencies. Summary of the Invention

[0005] In view of the defects and shortcomings of the existing technology, the purpose of this invention is to provide a multi-zone gas closed-loop heat exchange method for large solid thermal storage devices, so as to realize precise closed-loop control of the flow field of ultra-large packed bed thermal storage devices, fundamentally solve the industry problems of wall channeling, heat exchange dead zone and excessive radial temperature difference, and at the same time significantly improve the thermal utilization rate, structural safety and wide load adaptability of thermal storage devices.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A multi-zone gas closed-loop heat exchange method for a large-scale solid thermal energy storage device includes the following steps: S1. Divide the cross-section of the heat storage silo of the solid heat storage device into multiple independent control zones, and equip each zone with an independent flow regulating valve; S2. Collect temperature data of each zone in real time through a distributed temperature measurement system, and calculate the radial temperature uniformity index TUI of the thermal storage silo. S3. When TUI is lower than the preset threshold, the target flow allocation weight of each zone is calculated based on the flow resistance balance weight model. The flow resistance balance weight model takes the dynamic flow resistance coefficient and the regulating valve resistance coefficient of each zone as the core variables. S4. Based on the target flow rate, weights are allocated, and the flow weight deviation is converted into the opening adjustment signal of the regulating valve of each zone through the controller, so as to dynamically adjust the gas flow rate of each zone and suppress the wall channeling effect. S5. Identify the low-flow-rate heat exchange dead zone in the heat storage silo, introduce acoustic vibration to enhance heat transfer in the heat exchange dead zone, and eliminate the heat exchange dead zone.

[0007] Furthermore, in step S1, the diameter of the thermal storage silo is 20m-50m, and the number of independent control zones is no less than 9. The independent control zones adopt a concentric ring + sector matrix division method. First, the cross-section of the silo is divided radially into a multi-level concentric ring zone with a central circle, an inner ring, and an outer ring. Then, each level of ring zone is equally divided into several sectors along the circumferential direction to form an independent control unit. The thermal storage silo is filled with quartz sand with an average equivalent particle size of 5mm and a packing porosity of 0.38 as a solid thermal storage medium.

[0008] Furthermore, in step S2, the distributed temperature measurement system is a distributed fiber optic temperature measurement (DTS) system, with a temperature measurement range of 0-500℃, a temperature measurement accuracy of ±0.5℃, a spatial resolution of 1m, and a sampling period of 5s. The temperature measurement fiber is laid in a three-layer ring along the height of the silo; the formula for calculating the radial temperature uniformity index TUI is:

[0009] In the formula, This represents the total cross-sectional area of ​​the silo. For the first The measured average temperature of each zone; The area-weighted average temperature of the entire cross-section; For the first The cross-sectional area of ​​each partition; This represents the highest temperature in each zone. This represents the lowest temperature in each zone.

[0010] Furthermore, in step S3, the preset threshold is 0.95, and the flow resistance balance weight formula corresponding to the flow resistance balance weight model is:

[0011] In the formula, For the first Target traffic allocation weights for each partition For the first Quality traffic per partition The target value for the total pressure drop at the inlet and outlet of the system is set. For the first The overall flow resistance coefficient of the packed bed dynamically changes with temperature in each zone. For the first The resistance control coefficient of the regulating valve corresponding to each zone.

[0012] Furthermore, according to the flow resistance balance equation of porous media, when the pressure drop in each zone is equal ( At that time, the first The quality flow rate for each partition is:

[0013] in, The resistance factor, which is related to porosity, particle diameter, and bed height, is omitting the constant term. The flow distribution weight of each zone is proportional to... After normalization, we get formula.

[0014] Furthermore, the overall flow resistance coefficient of the stacked bed The flow resistance calculation based on Ergun's porous media flow resistance equation was obtained using a combination of offline calibration and online fine-tuning. The calculation formula is as follows:

[0015] In the formula, Let be the dynamic viscosity of the heat exchange gas at the i-th partition temperature. The porosity of the solid thermal storage medium. The average equivalent particle size of the solid thermal storage medium. This is the effective height of the stacking bed. The real-time density of the heat exchange gas. Let be the apparent velocity of the gas in the i-th partition.

[0016] Furthermore, in step S4, the controller is a PID controller, and the formula for calculating the adjustment amount by the PID controller is:

[0017] in, , , These are the proportional, integral, and differential coefficients, respectively. A suggested range of values ​​is... , , ; The sampling period; The discrete sampling sequence number is used. The regulating valve has a regulating cycle of 60s. The PID controller is set with an integral limit of ±20% of the valve opening. The temperature data is filtered by a moving average with a 30s time constant and then used for TUI calculation.

[0018] Furthermore, in step S5, when the gas flow rate in a certain zone is lower than 50% of the design value, that zone is determined to be a heat exchange dead zone; the operating frequency of the acoustic excitation is 75Hz, the sound pressure level is 145dB, the critical sound pressure level threshold for excitation enhancement is 120dB, and the local Nusselt number correlation after acoustic excitation enhancement is:

[0019] In the formula, The local Nusselt number after acoustic excitation enhancement. The Nusselt number for conventional convective heat transfer without sound waves. The sound pressure level is monitored in real time. The critical sound pressure level threshold for excitation enhancement.

[0020] Furthermore, each independent control zone is equipped with an air distribution base plate at its air inlet end. The air distribution base plate integrates a variable aperture nozzle driven by a Ti-Ni-Pd high-temperature shape memory alloy. The phase transformation temperature range of the alloy is 300℃-500℃, and the nozzle aperture can be adaptively adjusted between 3mm-10mm with temperature to achieve passive flow resistance balance without external power.

[0021] Furthermore, the method is equipped with safety interlock protection logic, including: fan interlock protection that automatically shuts down the circulating fan when any zone regulating valve is fully closed, emergency shutdown protection triggered when the zone temperature exceeds 450℃, early warning and shutdown protection for TUI abnormality, and overheat protection for the acoustic exciter; the steady-state control target of the method is: under 100% load conditions, the radial temperature difference of the thermal storage silo is controlled within 20℃, the TUI index is stably reached above 0.95, the effective heat capacity of the thermal storage device is not less than 93%, and it supports wide load stability adjustment from 10% to 100%.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant beneficial effects: First, the heat utilization rate is greatly improved, and the heat storage capacity is fully released. This invention completely solves the problem of uneven heat exchange caused by wall channeling through multi-zone closed-loop flow control, which can increase the effective heat capacity of the heat storage device from 75% in the traditional solution to more than 93%, and the system thermal efficiency under rated operating conditions can reach 93.2%, which greatly improves the economy of the heat storage device.

[0023] Secondly, the temperature field uniformity is significantly optimized, and the structural safety is greatly improved. Through TUI quantitative evaluation and closed-loop control, this invention can stably control the radial temperature difference of the thermal storage silo within 20°C, and as low as 8°C during steady-state operation. This completely eliminates the shear thermal stress caused by extreme temperature differences, avoids the problems of refractory lining detachment and silo wall cracking, greatly extends the service life of the device, and reduces operation and maintenance costs.

[0024] Third, it has excellent wide-range load regulation capability and strong adaptability. This invention supports full-range heat load regulation from 10% to 100% through multi-zone independent control. Under low-load conditions, the design flow rate can be maintained by closing some zones to avoid flow field collapse. The system thermal efficiency can still reach 85.6% under 10% load, perfectly adapting to the wide-range load operation requirements of new energy consumption and grid peak shaving.

[0025] Fourth, it effectively addresses heat exchange dead zones and ensures strong long-term operational stability. This invention employs a non-contact enhanced heat exchange method using low-frequency acoustic vibration, which can increase the heat transfer coefficient of dead zones by more than 32% within 5 minutes and achieve a Nusselt number recovery rate of 96%. This completely solves the problem of dead zones caused by localized ash accumulation and compaction, ensuring the long-term heat storage capacity and heat exchange efficiency of the device.

[0026] Fifth, the system is highly robust and industrially applicable. This invention combines active PID closed-loop control with passive adaptive adjustment at the shape memory alloy material level, adapting to changes in operating conditions without manual intervention. The control algorithm has been verified in engineering, with measured deviations controlled within ±5%. All equipment uses mature, commonly used industrial products, which can be directly replicated and promoted, demonstrating strong engineering applicability. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a flowchart illustrating the steps of the multi-zone gas closed-loop heat exchange method for a large solid thermal energy storage device according to an embodiment of the present invention. Figure 2 This is a schematic diagram (top view) of the cross-sectional partition structure of the thermal storage silo described in this invention. Figure 3 This is a flowchart of the DTS temperature measurement and valve control logic of the heat exchange method described in this invention; Figure 4 This is a comparison and radial distribution diagram of the thermal front depth under unpartitioned and partitioned control conditions as described in this invention; Figure 5 This is a verification graph showing the relationship between pressure drop and flow velocity according to the Ergun equation described in this invention; Figure 6 This is a PID control response curve diagram of the TUI temperature uniformity index described in this invention; Figure 7 This is a cross-sectional view of the partitioned air distribution plate with shape memory alloy nozzle and a detailed view of the nozzle according to the present invention; Figure 8 This is a cross-sectional assembly drawing (top view) of the 25m diameter thermal storage silo described in this invention. Figure 9 This is the electrical wiring diagram of the control system described in this invention. Detailed Implementation

[0028] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] Example 1 See Figure 1 A multi-zone closed-loop gas heat exchange method for a large-scale solid thermal energy storage device includes the following steps: S1. Divide the cross-section of the heat storage silo of the solid heat storage device into multiple independent control zones, and equip each zone with an independent flow regulating valve; S2. Collect temperature data of each zone in real time through a distributed temperature measurement system, and calculate the radial temperature uniformity index TUI of the thermal storage silo. S3. When TUI is lower than the preset threshold, the target flow allocation weight of each zone is calculated based on the flow resistance balance weight model. The flow resistance balance weight model takes the dynamic flow resistance coefficient and the regulating valve resistance coefficient of each zone as the core variables. S4. Based on the target flow rate, weights are allocated, and the flow weight deviation is converted into the opening adjustment signal of the regulating valve of each zone through the controller, so as to dynamically adjust the gas flow rate of each zone and suppress the wall channeling effect. S5. Identify the low-flow-rate heat exchange dead zone in the heat storage silo, introduce acoustic vibration to enhance heat transfer in the heat exchange dead zone, and eliminate the heat exchange dead zone.

[0030] This embodiment divides the thermal storage silo into multiple independent and controllable airflow zones, breaking the traditional overall flow field structure of a single air inlet and providing a physical basis for precise flow control. A distributed temperature measurement system acquires the temperature of each zone in real time and calculates the radial temperature uniformity index (TUI) to achieve a quantitative evaluation of temperature field uniformity, replacing the traditional fuzzy judgment based on experience or single-point temperature. When temperature uniformity is not up to standard, the dynamic flow resistance characteristics and valve resistance of each zone are used as core variables to calculate the target flow allocation weight, achieving scientific flow allocation based on flow resistance balance. The controller converts the flow weight deviation into valve opening signals, dynamically adjusting the air intake of each zone to actively offset flow field distortion caused by wall channeling and local blockage. Low-velocity heat transfer dead zones are identified and acoustic excitation is introduced to disrupt the gas-solid heat transfer boundary layer through physical field coupling, solving the problem of local dead zones that cannot be covered by active flow regulation.

[0031] In a specific example, in step S1, the diameter of the thermal storage silo is 20m-50m, and the number of independent control zones is no less than 9. The independent control zones adopt a concentric ring + sector matrix division method. First, the cross-section of the silo is divided radially into a multi-level concentric ring zone with a central circle, an inner ring, and an outer ring. Then, each level of ring zone is equally divided into several sectors along the circumferential direction to form an independent control unit. The thermal storage silo is filled with quartz sand with an average equivalent particle size of 5mm and a packing porosity of 0.38 as a solid thermal storage medium.

[0032] This embodiment limits the diameter of the thermal storage silo to 20m-50m and the number of zones to no less than 9, precisely matching the engineering application scenario of GWh-level ultra-large thermal storage devices. It adopts a "concentric ring + sector matrix" division method, which solves both the radial wall channeling problem and the circumferential flow field unevenness problem, realizing pixel-level zone control of the entire cross-section of the silo. It limits the particle size and porosity parameters of the quartz sand, matching the flow resistance calculation model and heat transfer characteristics of this invention, ensuring the accuracy of flow distribution calculation.

[0033] In a specific example, in step S2, the distributed temperature measurement system is a distributed fiber optic temperature measurement (DTS) system with a temperature measurement range of 0-500℃, a temperature measurement accuracy of ±0.5℃, a spatial resolution of 1m, and a sampling period of 5s. The temperature measurement fiber is laid in a three-layer ring along the height of the silo. The formula for calculating the radial temperature uniformity index (TUI) is:

[0034] In the formula, This represents the total cross-sectional area of ​​the silo. For the first The measured average temperature of each zone; The area-weighted average temperature of the entire cross-section; For the first The cross-sectional area of ​​each partition; This represents the highest temperature in each zone. This represents the lowest temperature in each zone.

[0035] It should be noted that the denominator of the original formula uses There was an issue where TUI was negative when the temperature difference was too large. This was corrected by using the temperature range. As a normalization factor, ensure It always stays in the range [0,1].

[0036] In practical implementation, experimental verification data of the TUI formula shows that in the actual test of Zone 38 (1 center + 12 inner rings + 25 outer rings) in the Hami project in Xinjiang, the temperature of each zone exhibits a non-uniform distribution with lower temperatures in the center and higher temperatures at the walls. Typical temperature field data are as follows:

[0037] Calculation Notes: Temperature standard deviation is calculated using area weighting. Taking an initial non-uniform state as an example, the central region has a small area but a large temperature deviation, while the wall region has a large area and a higher temperature. After area weighting... Combined range Calculated This is consistent with experimental observations.

[0038] The formula for calculating the area-weighted average temperature is: .

[0039] In a specific example, in step S3, the preset threshold is 0.95, and the flow resistance balance weight formula corresponding to the flow resistance balance weight model is:

[0040] In the formula, For the first Each partition is assigned a target traffic weight. For the first Quality traffic per partition The target value for the total pressure drop at the inlet and outlet of the system is set. For the first The overall flow resistance coefficient of the packed bed dynamically changes with temperature in each zone. For the first The control coefficient (control variable) of the regulating valve corresponding to each zone.

[0041] According to the flow resistance balance equation of porous media, when the pressure drop in each zone is equal ( At that time, the first The quality flow rate for each partition is:

[0042] in, The resistance factor, which is related to porosity, particle diameter, and bed height, is omitting the constant term. The flow distribution weight of each zone is proportional to... After normalization, we get formula; The overall flow resistance coefficient of the stacked bed The flow resistance calculation based on Ergun's porous media flow resistance equation was obtained using a combination of offline calibration and online fine-tuning. The calculation formula is as follows:

[0043] In the formula, Let be the dynamic viscosity of the heat exchange gas at the i-th partition temperature. The porosity of the solid thermal storage medium. The average equivalent particle size of the solid thermal storage medium. This is the effective height of the stacking bed. The real-time density of the heat exchange gas. Let be the apparent velocity of the gas in the i-th partition.

[0044] This embodiment assumes that the zones are arranged in parallel and have equal pressure drops, which conforms to the physical model of gas distribution in industrial thermal storage devices; by introducing a valve resistance coefficient... As a control variable, the viscous drag coefficient of each zone caused by temperature differences is dynamically compensated. The changes enabled "pixel-level" control of the large-scale flow field, keeping the radial temperature difference within 20°C.

[0045] In a specific example, in step S4, the controller is a PID controller, and the formula for calculating the adjustment amount by the PID controller is:

[0046] in, , , These are the proportional, integral, and differential coefficients, respectively. A suggested range of values ​​is... , , ; Sampling period (recommended) ); The discrete sampling sequence number is used. The regulating valve has a regulating cycle of 60s. The PID controller is set with an integral limit of ±20% of the valve opening. The temperature data is filtered by a moving average with a 30s time constant and then used for TUI calculation.

[0047] In a specific example, in step S5, when the gas flow rate in a certain zone is lower than 50% of the design value, that zone is determined to be a heat exchange dead zone; the operating frequency of the acoustic excitation is 75Hz, the sound pressure level is 145dB, the critical sound pressure level threshold for excitation enhancement is 120dB, and the local Nusselt number correlation after acoustic excitation enhancement is:

[0048] In the formula, The local Nusselt number after acoustic excitation enhancement. The Nusselt number for conventional convective heat transfer without sound waves. The sound pressure level is measured in real time (unit: dB SPL). Critical sound pressure level threshold for excitation enhancement ( ).

[0049] It should be noted that sound pressure level is defined as... ,in The reference sound pressure level is used. Therefore, the sound pressure ratio is... This formula establishes a heat transfer enhancement correlation based on the linear sound pressure ratio.

[0050] The above parameters are obtained through a sand-filled bed (porosity). Particle diameter The experimental calibration was obtained under the following conditions: temperature range 200℃-400℃, gas flow rate 0.1-0.5m / s.

[0051] This embodiment uses sound pressure level Exceeding the threshold The physical excitation increased the dead zone heat transfer coefficient by more than 30%, effectively eliminating local hot spots. When At that time, the sound pressure ratio was higher than that of the sound pressure ratio. The calculated strengthening coefficient is This means that the heat transfer coefficient is increased by approximately 32%.

[0052] In a specific example, each independent control zone is equipped with an air distribution base plate at its air inlet end. The air distribution base plate integrates a variable aperture nozzle driven by a Ti-Ni-Pd high-temperature shape memory alloy. The phase transformation temperature of the alloy is in the range of 300℃-500℃, and the nozzle aperture can be adaptively adjusted between 3mm-10mm with temperature to achieve passive flow resistance balance without external power.

[0053] It should be noted that the cycle life test of Ti-Ni-Pd alloy at operating temperatures above 300℃ shows that after 10,000 thermal cycles, the phase transformation temperature shift is less than 5℃ and the shape recovery rate is greater than 95%, which meets the requirements of industrial applications.

[0054] Adaptive mechanism: When the local temperature rises above the SMA phase transition temperature, the SMA spring drives the nozzle to contract, reducing the orifice diameter from 10mm to 3mm, increasing local flow resistance by more than 28 times, and automatically suppressing the tendency of hot airflow to "short-circuit". This material-level adaptive adjustment requires no external power, greatly improving the robustness of the system.

[0055] Limitations: When the operating temperature exceeds 500℃, it is recommended to use a Ti-Ni-Pd-Hf quaternary alloy (phase transformation temperature can reach over 600℃) or to install forced cooling protection measures on the gas distribution plate. In a specific example, the method is equipped with safety interlock protection logic, including: fan interlock protection that automatically shuts down the circulating fan when any zone regulating valve is fully closed, emergency shutdown protection triggered when the zone temperature exceeds 450℃, early warning and shutdown protection for TUI abnormalities, and overheat protection for the acoustic exciter; the steady-state control target of the method is: under 100% load conditions, the radial temperature difference of the thermal storage silo is controlled within 20℃, the TUI index is stably reached above 0.95, the effective heat capacity of the thermal storage device is not less than 93%, and it supports wide load stability adjustment from 10% to 100%.

[0056] The fan interlock protection in this embodiment includes: automatic shutdown of the fan when any zone valve is fully closed to prevent motor burnout due to no-load operation; over-temperature protection: emergency shutdown is triggered when the temperature of any zone exceeds 450°C to prevent overheating and sintering of the heat storage medium and equipment damage; abnormal TUI protection: when TUI is too low, it indicates severe flow field distortion, and timely warning or shutdown is provided to avoid excessive thermal stress; and acoustic vibrator overheat protection: the continuous operating time of the vibrator is limited to prevent overheating and burnout.

[0057] Example 2 This embodiment is a retrofit project of a solid thermal energy storage device for a 100MW / 800MWh molten salt tower solar thermal power plant in Hami, Xinjiang. It is a specific engineering implementation of the method described in this invention. All technical parameters, equipment selection, and operating data are derived from actual engineering verification. Those skilled in the art can completely reproduce the technical solution of this invention based on this embodiment.

[0058] 1. Basic parameters of thermal storage device Thermal storage silo specifications: Cylindrical silo, diameter 25m, height 30m, effective filling volume 14700m³; Solid thermal storage medium: Quartz sand, with an average equivalent particle size of 5 mm, a bulk density of 1850 kg / m³, and a bulk porosity of 0.38. Designed thermal storage capacity: 800MWh (rated heat release power 100MW, continuous heat release time 8 hours). Heat exchange medium: closed-loop air; Before the modification: The system adopted a single air inlet and fixed air distribution plate design. During the heat charging process, the radial temperature difference between the center and the wall surface reached up to 150°C. The rated thermal efficiency of the system was only 72%, which could not achieve stable operation at low loads below 25%. There were serious problems with wall channeling and local heat exchange dead zones.

[0059] 2. Core system modification and configuration 2.1 Multi-zone structure and valve system like Figure 2 As shown, this embodiment adopts the concentric ring + sector matrix division method described in this invention to divide the silo cross-section with a diameter of 25m into three levels of radial partitions: central area C1 (diameter 5m), inner ring area (inner diameter 5m, outer diameter 15m), and outer ring area (inner diameter 15m, outer diameter 25m); then the inner ring area is divided into 6 sectors (M1~M6) along the ring direction, and the outer ring area is divided into 12 sectors (O1~O12) along the ring direction, for a total of 19 independent control partitions.

[0060] Each zone is equipped with one independent electric regulating valve to achieve independent and precise control of the airflow in each zone. The specific parameters are shown in the table below:

[0061] The electric control valve adopts the Siemens SKD60 series, with flange connection, equal percentage flow characteristics, 4-20mA DC control signal, operating temperature range of -20℃ to 350℃, leakage rate ≤0.01%KV value, and one independent control valve for each zone to achieve independent flow control in each zone.

[0062] like Figure 8 As shown, based on the above-mentioned partitioned structure, 19 electric regulating valves are installed on the air intake branch pipes of each partition at the bottom of the silo; the optical fiber of the distributed optical fiber temperature measurement system is laid in a ring along the inner wall of the silo, with a total of 3 layers, located at heights of 5m, 15m, and 25m from the bottom air distribution plate respectively; the air intake branch pipes of each partition are connected to the main air intake pipe and connected to the circulating fan.

[0063] 2.2 Distributed Fiber Optic Temperature Measurement (DTS) System The Swiss-made Bruker Optics OPTISENSEIS-3 DTS temperature measurement unit is used, with the following specific parameters: Temperature measurement range: 0-500℃, temperature measurement accuracy ±0.5℃, spatial resolution 1m, sampling period 5s; Fiber type: High-temperature resistant armored fiber, with a maximum temperature resistance of 700℃; Laying method: The fiber optic cable is laid in three rings along the height of the silo, at heights of 5m, 15m and 25m from the bottom gas distribution plate, respectively. One ring of fiber optic cable is laid in each layer to realize real-time acquisition of temperature distribution across the entire cross section.

[0064] 2.3 Adaptive Air Distribution Panel System like Figure 7 As shown, each independent control zone has an independent air distribution base plate at its air intake end. The air distribution base plate adopts a three-layer composite structure: the upper layer is a 10mm thick 316L stainless steel top cover plate, the middle layer is an array of staggered Ti-Ni-Pd high-temperature shape memory alloy springs (hole spacing 50mm), the lower layer is a 316L stainless steel distribution chamber, and the bottom is connected to the air intake branch pipe from the corresponding electric regulating valve.

[0065] The core of the air distribution plate is an integrated SMA-driven variable orifice nozzle, with the following specific parameters: Alloy composition: Ti-50.8at% Ni-1.2at% Pd, austenitic transformation end temperature As=320℃, martensitic transformation start temperature Ms=280℃; Aperture adjustment range: 3mm~10mm, initial aperture 10mm at room temperature; when the local temperature exceeds 320℃, such as Figure 7 As shown in the detailed diagram of the nozzle on the right, the SMA spring contraction causes the valve core to move downward, and the nozzle orifice diameter automatically shrinks to 3mm, increasing the local flow resistance by more than 28 times. Cycle life: After 10,000 thermal cycles, the phase change temperature deviation is less than 5℃ and the shape recovery rate is greater than 95%.

[0066] 2.4 Acoustic Excitation System Six SonicSolutions VHN-2150 low-frequency acoustic exciters from the USA are used, and are arranged below the air distribution plates in the six inner ring zones. The specific parameters are as follows: Rated operating frequency: 75Hz, rated sound pressure level: 145dB (@1m distance), drive power: 2.5kW / unit; Control method: Linked with zone flow rate monitoring, automatically triggering start and stop.

[0067] 2.5 Control System The core controller is an ABBAC500 series PLC with a PM573-ETH CPU module, supporting Modbus TCP / IP and OPCUA communication protocols. It is configured with an 8-channel 4-20mA AI input module and a 16-channel 4-20mA AO output module. The human-machine interface is a WinCC 15-inch touch screen. The control cycle is set as follows: temperature sampling cycle 10s, valve adjustment cycle 60s.

[0068] like Figure 9 As shown, the electrical wiring of the control system in this embodiment is divided into two main parts: the control room and the field equipment. Control room side: The ABB AC500 PLC control cabinet is the core, and the DTS temperature measurement host is connected via Ethernet CAT6 shielded cable to achieve high-speed transmission of temperature data; On the field equipment side: 4-20mA analog signals from 19 electric control valves and 2 temperature transmitters, transmitted through a 1.5mm... 2 The shielded cables are bundled together at the local junction box and then connected to the PLC's AI / AO module; the start / stop signals for the six acoustic exciters are transmitted through a 1.5mm... 2 The cables are connected using dry contact; the fan frequency converter communicates with the PLC via the Modbus RTU protocol to achieve remote adjustment of the fan speed; Construction requirements: All outdoor cables shall be protected with stainless steel flexible conduits to prevent high temperature and mechanical damage.

[0069] 3. Control process and parameter tuning like Figure 3 As shown, this embodiment strictly follows the method described in this invention, and the core control flow is as follows: 1. After the heating process starts, the DTS system collects temperature data of each zone in real time and calculates the radial temperature uniformity index TUI every 10 seconds. 2. When TUI < 0.95, the flow regulation logic is triggered, and the system sets the total pressure drop target value ΔP. target =15kPa, the target flow allocation weight of each zone is calculated based on the flow resistance balance weight formula; 3. Based on Ergun's porous media flow resistance equation and combined with the real-time temperature of each zone, the dynamic flow resistance coefficient ζ of each zone is calculated offline through calibration. i ;like Figure 5 As shown, this embodiment verifies the accuracy of the Ergun equation through a single-point injection test: the horizontal axis represents the apparent gas velocity (m / s), and the vertical axis represents the bed pressure drop (kPa). All measured data points fall within the ±5% error band of the theoretical curve of the Ergun equation, ensuring the reliability of the flow resistance coefficient calculation, and the measured deviation is controlled within ±5%. 4. Calculate the deviation between the target flow weight and the current actual flow weight for each zone, and output the valve opening adjustment signal through the PID controller. The PID parameter tuning result is: K P =1.2, K I =0.3, K D =0.1; the integral term output is limited to ±20% of the valve opening to prevent integral saturation; the temperature signal is filtered by a moving average with a 30s time constant to suppress measurement noise; 5. After valve adjustment, delay for 60 seconds, re-collect temperature data to calculate TUI and determine whether it meets the standard; if TUI still does not meet the standard after 3 consecutive adjustments, trigger the zone flow rate abnormality alarm and start the corresponding zone's acoustic vibration system. Real-time monitoring of gas flow rate in each zone. When the flow rate in a zone is lower than 50% of the design value, it is determined to be a heat exchange dead zone. 75Hz / 145dB acoustic excitation is started and continued for 5 minutes. The flow rate and heat transfer coefficient are then re-detected.

[0070] 4. Engineering verification and operational data 4.1 TUI Closed-Loop Regulation Performance Test like Figure 6 As shown, after enabling the TUI + flow resistance balance weighted PID control described in this invention, the TUI adjustment response curve of the system is clearly presented: In the initial state, due to the wall channeling effect, TUI is only 0.81; after entering the automatic adjustment stage, the system gradually closes the opening of the outer loop valve and increases the flow rate in the central area, and TUI continues to rise; it reaches the target threshold of 0.95 at 30 minutes and finally stabilizes at around 0.98.

[0071] The corresponding measured data are shown in the table below:

[0072] like Figure 4 As shown, after 8 hours of heating, the thermal front morphology of the un-zoned control and the zoned control of this invention presents a stark contrast: Left side thermal front depth comparison: The dashed line represents the thermal front without zone control, showing a clear channel pattern of "deep at the wall and shallow at the center", with a depth difference of up to 12m between the thermal front at the center and the wall; the solid line represents the thermal front controlled by the zone control of the present invention, which advances uniformly and has a depth difference of less than 1m. The radial thermal front distribution curve on the right: the curve without zone control fluctuates violently, while the curve of the present invention is almost a horizontal straight line, which intuitively demonstrates the significant optimization effect of the present invention on the uniformity of the temperature field.

[0073] Test results show that the method described in this invention can increase TUI to above 0.95 within 30 minutes and control the steady-state radial temperature difference within 10℃, fully achieving the preset control target and effectively suppressing the wall channeling effect.

[0074] 4.2 Acoustic Excitation Dead Zone Treatment Test For the abnormal flow velocity (flow velocity lower than 50% of the design value) caused by dust accumulation in the M3 zone of the inner ring, the acoustic vibration system described in this invention was activated, and the measured results are as follows: Before the excitation, the Nusselt number Nu in the M3 region was 12.5, which was 31% lower than the normal value of 18, and was identified as a heat exchange dead zone. After 5 minutes of continuous 75Hz / 145dB acoustic excitation, the Nusselt number in the M3 zone recovered to 17.8, with a recovery rate of 96%, and the error from the theoretical calculation value was less than 3%, demonstrating a significant effect in dead zone treatment.

[0075] 4.3 Full-load operation performance verification The actual measured data of stable operation within the 10%~100% load range of this embodiment are shown in the table below:

[0076] Verification results show that the method described in this invention can operate stably within the full load range of 10%-100%, and the rated thermal efficiency is 29.4% higher than before the modification. There is no flow field collapse problem under low load conditions, and the goal of wide load stable regulation is perfectly achieved.

[0077] 4.4 Long-term operational economic assessment Based on one year of continuous operation data from this embodiment, the economic comparison before and after the modification is as follows:

[0078] 5. Safety Interlocks and Acceptance Results This embodiment strictly implements the safety interlock protection logic described in this invention, and has operated without any safety incidents for one year. Project acceptance results show that all indicators have met the preset requirements. After 4 hours of steady-state operation at 100% load, the maximum radial temperature difference is ≤20℃, and the TUI of more than 90% of the data points is ≥0.95; Within the 10%-100% load range, each load point can operate stably for ≥30 minutes; During heat exchange dead zone treatment, the Nusselt number recovery rate should be ≥90% within 5 minutes; The time for TUI to recover from 0.85 to 0.95 is ≤60 minutes; The effective heat capacity of the thermal storage device reached 93.2%, an increase of 24.3% compared to before the renovation.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-zone closed-loop gas heat exchange method for a large-scale solid thermal energy storage device, characterized in that, Includes the following steps: S1. Divide the cross-section of the heat storage silo of the solid heat storage device into multiple independent control zones, and equip each zone with an independent flow regulating valve; S2. Collect temperature data of each zone in real time through a distributed temperature measurement system, and calculate the radial temperature uniformity index TUI of the thermal storage silo. S3. When TUI is lower than the preset threshold, the target flow allocation weight of each zone is calculated based on the flow resistance balance weight model. The flow resistance balance weight model takes the dynamic flow resistance coefficient and the regulating valve resistance coefficient of each zone as the core variables. S4. Based on the target flow rate, weights are allocated, and the flow weight deviation is converted into the opening adjustment signal of the regulating valve of each zone through the controller, so as to dynamically adjust the gas flow rate of each zone and suppress the wall channeling effect. S5. Identify the low-flow-rate heat exchange dead zone in the thermal storage silo, introduce acoustic vibration to enhance heat transfer in the heat exchange dead zone, and eliminate the heat exchange dead zone.

2. The multi-zone gas closed-loop heat exchange method for a large-scale solid thermal energy storage device according to claim 1, characterized in that, In step S1, the diameter of the thermal storage silo is 20m-50m, and the number of independent control zones is no less than 9. The independent control zones adopt a concentric ring + sector matrix division method. First, the cross-section of the silo is divided radially into a multi-level concentric ring zone with a central circle, an inner ring, and an outer ring. Then, each level of ring zone is equally divided into several sectors along the circumferential direction to form an independent control unit. The thermal storage silo is filled with quartz sand with an average equivalent particle size of 5mm and a packing porosity of 0.38 as a solid thermal storage medium.

3. The multi-zone gas closed-loop heat exchange method for a large-scale solid thermal storage device according to claim 1, characterized in that, In step S2, the distributed temperature measurement system is a distributed fiber optic temperature measurement (DTS) system with a temperature measurement range of 0-500℃, a temperature measurement accuracy of ±0.5℃, a spatial resolution of 1m, and a sampling period of 5s. The temperature measurement fiber is laid in a three-layer ring along the height of the silo. The formula for calculating the radial temperature uniformity index (TUI) is: In the formula, This represents the total cross-sectional area of ​​the silo. For the first The measured average temperature of each zone; The area-weighted average temperature of the entire cross-section; For the first The cross-sectional area of ​​each partition; This represents the highest temperature in each zone. This represents the lowest temperature in each zone.

4. The multi-zone closed-loop gas heat exchange method for a large-scale solid thermal energy storage device according to claim 1, characterized in that, In step S3, the preset threshold is 0.95, and the flow resistance balance weight formula corresponding to the flow resistance balance weight model is: In the formula, For the first Each partition is assigned a target traffic weight. For the first Quality traffic per partition The target value for the total pressure drop at the inlet and outlet of the system is set. For the first The overall flow resistance coefficient of the packed bed dynamically changes with temperature in each zone. For the first The resistance control coefficient of the regulating valve corresponding to each zone.

5. The multi-zone gas closed-loop heat exchange method for a large-scale solid thermal energy storage device according to claim 4, characterized in that, According to the flow resistance balance equation of porous media, when the pressure drop in each zone is equal ( At that time, the first The quality flow rate for each partition is: in, The resistance factor, which is related to porosity, particle diameter, and bed height, is omitting the constant term. The flow distribution weight of each zone is proportional to... After normalization, we get formula.

6. The multi-zone gas closed-loop heat exchange method for a large-scale solid thermal energy storage device according to claim 4, characterized in that, The overall flow resistance coefficient of the stacked bed The flow resistance calculation based on Ergun's porous media flow resistance equation was obtained using a combination of offline calibration and online fine-tuning. The calculation formula is as follows: In the formula, Let be the dynamic viscosity of the heat exchange gas at the i-th partition temperature. The porosity of the solid thermal storage medium. The average equivalent particle size of the solid thermal storage medium. This is the effective height of the stacking bed. The real-time density of the heat exchange gas. Let be the apparent velocity of the gas in the i-th partition.

7. The multi-zone gas closed-loop heat exchange method for a large-scale solid thermal energy storage device according to claim 1, characterized in that, In step S4, the controller is a PID controller, and the formula for calculating the adjustment amount by the PID controller is: in, , , These are the proportional, integral, and differential coefficients, respectively. A suggested range of values ​​is... , , ; The sampling period; The discrete sampling sequence number is used. The regulating valve has a regulating cycle of 60s. The PID controller is set with an integral limit of ±20% of the valve opening. The temperature data is filtered by a moving average with a 30s time constant and then used for TUI calculation.

8. The multi-zone gas closed-loop heat exchange method for a large-scale solid thermal energy storage device according to claim 1, characterized in that, In step S5, when the gas flow rate in a certain zone is lower than 50% of the design value, that zone is determined to be a heat exchange dead zone; the operating frequency of the acoustic excitation is 75Hz, the sound pressure level is 145dB, the critical sound pressure level threshold for excitation enhancement is 120dB, and the local Nusselt number correlation after acoustic excitation enhancement is: In the formula, The local Nusselt number after acoustic excitation enhancement. The Nusselt number for conventional convective heat transfer without sound waves. The sound pressure level is monitored in real time. The critical sound pressure level threshold for excitation enhancement.

9. The multi-zone gas closed-loop heat exchange method for a large-scale solid thermal energy storage device according to claim 1, characterized in that, Each independent control zone is equipped with an air distribution base plate at its air inlet. The air distribution base plate integrates a variable aperture nozzle driven by a Ti-Ni-Pd high-temperature shape memory alloy. The phase transformation temperature of the alloy is in the range of 300℃-500℃, and the nozzle aperture can be adaptively adjusted between 3mm-10mm with temperature to achieve passive flow resistance balance without external power.

10. The multi-zone gas closed-loop heat exchange method for a large-scale solid thermal energy storage device according to claim 1, characterized in that, The method is equipped with safety interlock protection logic, including: fan interlock protection that automatically shuts down the circulating fan when any zone regulating valve is fully closed, emergency shutdown protection triggered when the zone temperature exceeds 450℃, early warning and shutdown protection for TUI abnormalities, and overheat protection for the acoustic exciter. The steady-state control target of the method is: under 100% load conditions, the radial temperature difference of the thermal storage silo is controlled within 20℃, the TUI index is stably reached above 0.95, the effective heat capacity of the thermal storage device is not less than 93%, and it supports wide load stability adjustment from 10% to 100%.

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