Fused salt heat storage device and active heat transfer enhancement method
By introducing a pressure lifting unit and an axial rotation thinning unit into the molten salt thermal storage device, close contact between the molten salt and the heat source and effective removal of the solidified layer are achieved. This solves the problems of low heat transfer efficiency and rapid heat transfer rate decay in traditional molten salt thermal storage devices, and enables the operation of a highly efficient and recyclable molten salt thermal storage system.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SOUTHEAST UNIV
- Filing Date
- 2026-02-26
- Publication Date
- 2026-06-02
AI Technical Summary
Existing molten salt thermal storage devices suffer from low heat transfer efficiency, rapid decay of heat transfer rate, and difficulty in achieving cyclic active contact phase change to enhance heat transfer during melting and solidification, making it difficult for the system to operate stably for a long period of time.
An active drive module, including a pressure lifting unit and an axial rotation thinning unit, is adopted. Through the contact plate and scraper assembly, heat transfer is actively enhanced during the melting and solidification processes, ensuring close contact between the molten salt and the heat source and effective removal of the solidified layer.
It significantly improves heat transfer efficiency and uniformity, enabling efficient and cyclical operation of molten salt thermal storage systems, overcoming the limitations of traditional passive enhancement technologies, and meeting the long-term stable operation requirements of high-temperature molten salt thermal storage tanks.
Smart Images
Figure CN121739802B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of molten salt thermal energy storage technology, specifically to a molten salt thermal energy storage device and an active heat transfer enhancement method. Background Technology
[0002] The inherent intermittency and volatility of new energy sources lead to uncontrollable power generation, exacerbating the dynamic imbalance between power grid supply and demand. To address these issues, "peak shaving and valley filling" has become a key measure to ensure grid stability. Molten salt thermal energy storage technology, with its advantages of high thermal density, wide operating temperature range, and strong thermal stability, plays a crucial role in new energy consumption, industrial waste heat recovery, and regional heating peak shaving. Especially in medium- and high-temperature thermal energy storage scenarios of 300-600℃, the long-term and stable thermal storage capacity of molten salt thermal energy storage becomes a key link between new energy power generation and end-user energy consumption. Its heat transfer efficiency and operational stability directly determine the energy efficiency level and economic benefits of the thermal energy storage system.
[0003] Molten salt thermal energy storage technology is mainly divided into two categories: sensible thermal energy storage and latent thermal energy storage. Sensible thermal energy storage relies on the temperature change of molten salt to store thermal energy; the technology is mature but has a low storage density. Latent thermal energy storage utilizes the latent heat of phase change in molten salt, and its storage density can reach 3 to 5 times that of sensible thermal energy storage, thus becoming a research hotspot in recent years. However, latent thermal energy storage devices face significant technical bottlenecks in practical applications: during the melting process, a thick liquid film layer easily forms between the molten salt and the heat source, leading to a significant increase in heat transfer resistance; during the solidification process, the solidified layer that gradually forms and thickens on the inner wall of the tank further reduces heat transfer efficiency, which can not only cause local overheating of the heat exchange surface but also reduce the system's steam generation efficiency, severely restricting the large-scale application of molten salt thermal energy storage technology. To improve the heat transfer performance of molten salt thermal storage devices, traditional enhancement technologies mostly employ passive heat exchange methods, which can be categorized into three types based on their mechanism of action: First, optimizing the structure of the molten salt storage tank to improve convective heat transfer by enhancing the flow state of the molten salt, but this has limited effect on reducing the thickness of the solidified layer; second, adding fins or other extended surfaces to increase the heat transfer area, but the solidified molten salt easily adheres to the fin surface, thus increasing the heat transfer resistance; third, introducing high-efficiency heat exchange elements such as heat pipes, diamond, and foamed metals, which can improve the local heat transfer coefficient, but none of these can control the liquid film thickness and solidified layer growth during the molten salt phase change process. Therefore, due to these inherent limitations, existing passive enhancement technologies are difficult to meet the basic requirements for the long-term stable operation of latent heat storage devices.
[0004] To overcome the limitations of traditional passive heat exchange enhancement technologies in high-temperature molten salt thermal storage, active force-driven heat exchange is considered one of the most promising solutions for maintaining the system's high-efficiency heat exchange performance. The core idea is to actively intervene in the molten salt phase change process through external force. Existing solutions specifically involve: during the melting stage, mechanisms such as springs and mechanical pressure rods are used to continuously push the solid phase change material close to the heat source, shortening the heat transfer path of the molten layer and maintaining efficient contact melting to alleviate the problem of continuously decreasing heat transfer rate; during the solidification stage, a scraper continuously thins or squeezes away the solidified layer on the inner wall of the tank, reducing thermal resistance to ensure efficient heat release from the high-temperature molten salt. The active power-driven heat exchange method is only applicable to the single process of melting or solidifying high-temperature molten salt, and has not yet formed an integrated solution suitable for the high-temperature molten salt heat storage and release cycle process. Secondly, the external power source device (such as the device based on elastic force, electromagnetic force, or mechanical pressure) is bulky, and the active power drive device can only achieve a single action process, making it difficult to achieve continuous and cyclical contact melting between solid high-temperature molten salt and the heat source. In addition, the overall rotating thinning structure used in the solidification process is not only energy-intensive, but also prone to molten salt splashing and increases the risk of equipment corrosion. Moreover, some scraper devices can only achieve radial scraping, which cannot be adapted to the arc-shaped inner wall of the tank, making it difficult to continuously, accurately, and stably thin the thermal resistance of the solidified layer of the high-temperature molten salt heat storage tank. Finally, the sealing and heat insulation design between the active drive device and the high-temperature molten salt environment is insufficient, which can easily lead to device overheating failure or molten salt leakage, reducing device reliability and increasing maintenance costs, making it difficult to meet the requirements of long-term and efficient operation of industrial-grade molten salt heat storage devices.
[0005] In summary, there is an urgent need to develop a main-powered enhanced melting and solidification phase change heat transfer technology that is recyclable, simple in structure, and controllable in performance, in order to promote the practical application and performance improvement of high-temperature molten salt thermal energy storage systems. Summary of the Invention
[0006] To address the shortcomings of existing technologies, this invention provides a molten salt thermal storage device and an active heat transfer enhancement method, which effectively solves the problems of low heat exchange rate, rapid decay of heat transfer efficiency, and difficulty in achieving cyclic active contact phase change enhanced heat transfer in traditional molten salt thermal storage tanks during the charging and discharging process. This provides an effective solution for practical engineering applications such as waste heat recovery and deep peak shaving of power grids.
[0007] To achieve the above objectives, the present invention provides the following technical solution:
[0008] A molten salt thermal storage device includes a molten salt thermal storage module, a heating module, and an active drive module. The molten salt thermal storage module includes a molten salt reservoir for filling with molten salt phase change material. The heating module is located below the molten salt reservoir and is in close contact with the bottom of the molten salt reservoir through a high-temperature resistant heat-conducting layer. The active drive module includes a pressure lifting unit and an axial rotation thinning unit. The pressure lifting unit includes a rope drive device and a contact plate. The rope drive device is installed on the top of the molten salt reservoir, and the contact plate is located inside the molten salt reservoir and connected to the power output end of the rope drive device. Under the power actuation of the rope drive device, the contact plate rises and falls within the molten salt reservoir. The axial rotation thinning unit includes a rotary motor, a two-stage gear transmission mechanism, and a scraper assembly. The fixed part of the rotary motor is installed on the top of the molten salt reservoir, and the power output end is linked to the scraper assembly through the two-stage gear transmission mechanism. Under the power actuation of the rotary motor, the scraper assembly rotates clockwise or counterclockwise against the inner wall of the reservoir.
[0009] Preferably, the rope drive device includes a lifting motor, a take-up reel, a steering pulley, and a rope; the lifting motor, the take-up reel, and the steering pulley are all installed on the top of the molten salt thermal storage tank; several steering pulleys are required according to their position; the lifting motor is connected to the take-up reel in a drive connection; one end of the rope is wound around the take-up reel, and the other end passes around each steering pulley in sequence, passes through the top of the molten salt thermal storage tank, and is connected to the contact pressure plate.
[0010] Preferably, a metal insulating outer cylinder is provided below the top of the molten salt thermal storage tank, and a fixing ring is installed against the inner wall of the metal insulating outer cylinder, which is fixedly connected to the top of the molten salt thermal storage tank; the two-stage gear transmission mechanism includes a first-stage gear transmission pair and a second-stage gear transmission pair; wherein: the first-stage gear transmission pair includes a driving gear and a driven gear that mesh with each other, and the rotation axis of the driving gear is perpendicular to the rotation axis of the driven gear; the second-stage gear transmission pair includes a rotary gear and a rotary internal gear ring; the outer wall of the rotary internal gear ring and the inner wall of the fixing ring are circumferentially rotatable, and the inner ring of the rotary internal gear ring is provided with teeth that mesh with the rotary gear, and the rotary gear and the driven gear are coaxially connected; the scraper assembly is linked to the rotary internal gear ring.
[0011] Preferably, the scraper assembly includes a concentric disc, scraper connectors, and scrapers; the concentric disc is placed above the rotating internal gear ring, and the scraper connectors are of several kinds, evenly arranged along the circumference of the concentric disc; the rotating internal gear ring is provided with a through hole corresponding to the position of each scraper connector; each scraper connector passes through the corresponding through hole and connects to the upper end of the corresponding scraper.
[0012] Preferably, the molten salt thermal storage module further includes a semi-circular coil; the semi-circular coil is attached to the outer surface of the molten salt thermal storage device to form a spirally rising heat exchange channel, and a low-temperature water inlet is arranged below it and a steam outlet is provided above it.
[0013] Preferably, the molten salt thermal storage module further includes a dome; the dome is arranged on top of the molten salt thermal storage unit to form a storage space; the dome is surrounded by a porous wall.
[0014] Preferably, the molten salt thermal storage tank includes a tank body, an upper cover plate, and a lower cover plate; the upper and lower ends of the tank body are respectively connected to the upper and lower cover plates, and the upper cover plate has a through hole in the center; the lifting motor, the take-up reel, and the steering pulley are all installed above the upper cover plate; the rope passes through the through hole in the center of the upper cover plate and is connected to the contact pressure plate; the fixed part of the rotary motor is installed above the upper cover plate; the fixing ring is fixed to the upper cover plate; the rotary gear and the driven gear are positioned and supported on the upper cover plate by bearings.
[0015] Preferably, the distance between the scraper and the inner wall of the molten salt heat storage tank should ensure that the scraper is separated from the contact pressure plate while the scraper can scrape off the solidified layer within a preset thickness range.
[0016] Preferably, the scraper blade adopts a bidirectional asymmetric design: the cutting angle of the scraper blade facing the solidified layer is smaller than the guiding blade angle away from the solidified layer.
[0017] Another technical objective of this invention is to provide an active heat transfer enhancement method based on the aforementioned molten salt thermal storage device. This method includes an active driving process for molten salt thermal storage and an active driving process for molten salt thermal release. The active driving process for molten salt thermal storage is implemented using a pressure lifting unit, and the active driving process for molten salt thermal release is implemented using an axial rotation thinning unit. Specifically, it includes the following steps:
[0018] Step S1: Fill the molten salt thermal storage tank with solid molten salt phase change material;
[0019] Step S2: Start the heating module to heat the solid molten salt phase change material in the molten salt heat storage tank;
[0020] Step S3: Activate the pressure lifting unit and control the contact plate to descend at a preset rate. The contact plate contacts the solid molten salt phase change material and applies pressure to it, pushing the solid molten salt phase change material to maintain close contact with the heating surface of the heating module. The liquid molten salt phase change material above the heating surface is squeezed to the top of the molten salt heat storage tank until the solid molten salt phase change material is completely melted. When the contact plate is in contact with the heating surface, control the pressure lifting unit to move in the opposite direction to drive the contact plate back to the initial position and stop the pressure lifting unit. During this process, activate the axial rotation thinning unit to drive the scraper assembly to rotate clockwise or counterclockwise against the inner wall of the tank to scrape off the solidified molten salt layer attached to the inner wall of the molten salt heat storage tank, reducing the thermal resistance of the heat release process.
[0021] Compared with the prior art, the present invention has the following beneficial effects:
[0022] This invention employs active heat transfer enhancement technology, which breaks through the technical bottleneck of low heat transfer efficiency in traditional constrained melting process, and constructs a high-efficiency contact melting and contact solidification heat transfer enhancement mode, which significantly improves heat transfer efficiency and uniformity, and effectively alleviates the decay rate of heat transfer performance.
[0023] Furthermore, by introducing active compact force-driven structures such as pressure lifting units and axial rotation thinning units, this invention overcomes the inherent technical challenge of the difficulty in recycling existing contact melting and contact solidification heat transfer modes, and provides key technical support for achieving overall efficient operation of molten salt thermal storage systems in engineering practice. Attached Figure Description
[0024] Figure 1 This is a schematic diagram of the molten salt thermal storage device described in this invention;
[0025] Figure 2 for Figure 1 A schematic diagram of the structure of the heating module;
[0026] Figure 3 for Figure 1 A schematic diagram of the pressure lifting unit of the active drive module;
[0027] Figure 4 for Figure 1 A schematic diagram of the axial rotational thinning unit of the active drive module;
[0028] Figure 5 for Figure 1 Schematic diagram of the transmission connection of the central axis rotary thinning unit;
[0029] Figure 6 A schematic diagram of the two-stage gear transmission mechanism for the axial rotation thinning unit;
[0030] Figure 7 For the present invention Figure 1 Schematic diagram of the structure of the inner metal insulation outer cylinder;
[0031] Figure 8 This is a schematic diagram of the bidirectional asymmetric scraper in Embodiment 2 of the present invention;
[0032] Figure 9 A simplified model of the pressure lifting unit based on the working principle of the active drive module described in this invention and a comparison of the results of the simplified model of the gravity-driven pressure lifting unit under different experimental conditions are shown in the figure. In the figure: (a) shows a simplified structural diagram of the simplified model based on the working principle of the pressure lifting unit of the active drive module described in this invention; (b) shows a comparison of the average temperature-heating time variation curves of the heat sink under different experimental conditions.
[0033] Figure 10 The figure shows a simplified model constructed based on the working principle of the axial rotation thinning unit of the active drive module described in this invention, and a comparison of the results under different experimental conditions. In the figure: (a) shows a simplified structural diagram of the simplified model constructed based on the working principle of the axial rotation thinning unit of the active drive module described in this invention; (b) shows a comparison of the temperature-time variation curves of the simplified model of the axial rotation thinning unit of the active drive module described in this invention under different experimental conditions; (c) shows a comparison of the heat release power-time variation curves of the simplified model of the axial rotation thinning unit of the active drive module described in this invention under different experimental conditions.
[0034] In the diagram, 1. Heating module; 2. Lower cover plate; 3. Tank body; 4. Semi-circular coil; 5. Upper cover plate; 6. Cable reel; 7. Dome; 8. Lifting motor; 9. Rotary motor; 10. Driven gear; 11. Bearing; 12. Steering pulley; 13. Electric heating rod hole; 14. Rope; 15. Contact pressure plate; 16. Scraper; 17. Metal insulation outer cylinder; 18. Rotary gear; 19. Concentric disc; 20. Fixing ring; 21. Rotary internal gear ring; 22. Metal insulation cylinder bottom; 23. Bidirectional asymmetric scraper.
[0035] 24. Temperature measuring thermocouple; 25. Base; 26. Weight tray; 27. Gravity support rod. Detailed Implementation
[0036] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0037] In the description of this invention, it should be understood that the terms "upper," "lower," "inner," "opening," "thickness," etc., indicating orientation or positional relationship are only for the purpose of simplifying the description and do not indicate or imply that a component or element must have a specific orientation and be constructed and operated in that orientation, and therefore should not be regarded as a limitation of this invention.
[0038] The following is based on Figures 1-8 This invention describes the molten salt thermal storage device provided in an embodiment of the invention. Example 1
[0039] Please refer to this embodiment. Figures 1-7 .
[0040] Please see Figure 1This invention provides a molten salt thermal storage device, including a molten salt thermal storage module, a heating module 1, and an active drive module, wherein:
[0041] The molten salt thermal storage module includes a molten salt thermal storage unit, a semi-circular coil 4, and a dome 7. The molten salt thermal storage unit is used to fill molten salt phase change material and includes a tank body 3, an upper cover plate 5, and a lower cover plate 2. The upper and lower ends of the tank body 3 are respectively connected to the upper and lower cover plates 2 to form a molten salt thermal storage unit filled with high-temperature molten salt phase change material. A through hole is also opened in the center of the upper cover plate 5. The semi-circular coil 4 is welded to the outer surface of the tank body 3 to form a spiral upward heat exchange channel. A low-temperature water inlet is arranged below it, and a steam outlet is provided above it. A dome 7 is arranged above the upper cover plate 5 to form a storage space. The dome 7 has a porous wall surface to achieve ventilation and cooling. The inner wall of the tank body 3 is provided with a surface functional layer. The surface functional layer is a high-temperature resistant low surface energy coating or a micro-nano scale structure surface, which is used to reduce the adhesion of the solid molten salt phase change material during solidification and phase change.
[0042] It should be noted that the tank body 3 is sealed to the upper and lower cover plates 2 by mechanically pressing high-temperature resistant gaskets. High-temperature resistant gaskets include, but are not limited to, graphite metal gaskets, steel-coated ceramic fiber gaskets, and metal spiral wound gaskets.
[0043] The heating module 1 is located below the molten salt thermal storage module and is in close contact with the lower cover plate 2 through a high-temperature resistant heat-conducting layer. The heating method of the heating module 1 includes, but is not limited to, electric heating, heat transfer oil heating, and molten salt heating. When electric heating is used, the heating module 1 is provided with several electric heating rod holes 13, and each electric heating rod is installed in the electric heating rod hole 13, which can be heated after being powered on.
[0044] In the heating module 1 of this invention, the electric heating rods are symmetrically distributed, wherein the depth of the heating rod holes, the diameter of the heating rod holes, the spacing between the heating holes, and the symmetrical spacing between the heating holes can be arranged according to actual needs. In a preferred embodiment, the depth of the heating rod holes is 260-310mm, the diameter of the heating rod holes is 15-18mm, the spacing between the heating holes is 7.5-9mm, and the symmetrical spacing between the heating holes is 5-10mm.
[0045] The active drive module includes a pressure lifting unit and an axial rotation thinning unit, wherein:
[0046] The pressure lifting unit includes a rope drive device and a contact plate 15. The rope drive device is installed on the top of the molten salt thermal storage tank, and the contact plate 15 is located inside the molten salt thermal storage tank and connected to the power output end of the rope drive device. Under the power actuation of the rope drive device, the contact plate 15 rises and falls within the molten salt thermal storage tank. In this invention, the rope drive device includes a lifting motor 8, a take-up reel 6, a guide pulley 12, and a rope 14. The lifting motor 8, the take-up reel 6, and the guide pulley 12 are all installed above the upper cover plate 5. Several guide pulleys 12 are arranged according to their positions, and three are shown in the attached figure. The lifting motor 8 is connected to the take-up reel 6 for transmission. One end of the rope 14 is wound around the take-up reel 6, and the other end passes around each guide pulley 12 in sequence, passes through the central hole of the upper cover plate 5, and connects to the contact plate 15. Thus, this invention can pull the rope 14 to lift / lower the contact plate 15 by controlling the direction of the lifting motor 8, that is, drive the contact plate 15 to move up and down along the direction of gravity. In this invention, the pressure lifting unit uses a lifting motor 8 to rotate in the forward and reverse directions to drive the contact plate 15 to move upward and downward in a cyclical motion. There is a certain distance between the contact plate 15 and the inner wall of the tank 3. The contact plate 15 has multiple holes in the circumferential direction and is connected by bolts to achieve loading and unloading. Multiple layers of pressure plates can be stacked or reduced on top of the contact plate 15 to increase or decrease the downward pressure.
[0047] The axial rotation thinning unit includes a rotary motor 9, a two-stage gear transmission mechanism, and a scraper assembly. The fixed part of the rotary motor 9 is installed on the top of the molten salt heat storage tank, and the power output end is linked to the scraper assembly through the two-stage gear transmission mechanism. Under the power of the rotary motor 9, the scraper assembly is attached to the inner wall of the tank 3 and rotates clockwise or counterclockwise.
[0048] In this invention, in order to realize the installation of the two-stage gear transmission mechanism, a metal insulation outer cylinder 17 is provided below the top of the molten salt heat storage tank. A fixing ring 20 is installed inside the metal insulation outer cylinder 17 and is fixedly connected to the top of the molten salt heat storage tank. The fixing ring 20 is placed directly above the metal insulation cylinder bottom 22 of the metal insulation outer cylinder 17. The metal insulation cylinder bottom 22 is made of heat insulation material.
[0049] The two-stage gear transmission mechanism includes a first-stage gear transmission pair and a second-stage gear transmission pair; wherein: the first-stage gear transmission pair includes a driving gear and a driven gear 10 that mesh with each other, and the rotation axis of the driving gear is perpendicular to the rotation axis of the driven gear 10; the second-stage gear transmission pair includes a rotary gear 18 and a rotary internal gear ring 21; the outer wall of the rotary internal gear ring 21 and the inner wall of the fixed ring 20 are circumferentially rotatable, and the inner ring of the rotary internal gear ring 21 is provided with teeth that mesh with the rotary gear 18; the rotary gear 18 and the driven gear 10 are coaxially connected and positioned and supported on the upper cover plate 5 by bearing 11; the scraper assembly is linked to the rotary internal gear ring 21. Specifically, the scraper assembly includes a concentric disc 19, scraper connectors, and a scraper 16. The concentric disc 19 is positioned above a rotating internal gear ring 21. Several scraper connectors are evenly arranged along the circumference of the concentric disc 19. The rotating internal gear ring 21 has a through hole corresponding to the position of each scraper connector. Each scraper connector passes through the corresponding through hole and connects to the upper end of the corresponding scraper 16. By controlling the direction and speed of the rotary motor 9, the scraper 16 is driven to rotate clockwise or counterclockwise against the inner wall of the tank 3, enabling the scraper 16 to directionally scrape away the solidified layer.
[0050] It should be noted that the distance between the scraper 16 and the rotating internal gear ring 21 can be further adjusted according to the adhesion of the solid molten salt phase change material on the inner wall of the tank 3. Adjusting the appropriate distance of the scraper 16 allows for rapid scraping away of the solidified molten salt phase change material on the inner wall of the tank 3. Specifically, each scraper connector has a fixing hole at its lower end, and a screw is welded to the upper end of the scraper 16. After the screw passes through the fixing hole, it is locked with a lock nut, thus connecting and fixing the scraper 16 to the scraper connector. Therefore, adjusting the distance between the scraper 16 and the concentric disc 19 (i.e., the distance of the adjusting screw) adjusts the distance between the scraper 16 and the inner wall of the tank 3, allowing the rotating motor 9 to control the direction and speed, enabling the scraper 16 to directionally scrape away the solidified layer.
[0051] Preferably, the distance between the scraper 16 and the inner wall of the tank 3 (optionally less than 5mm) should ensure that the scraper 16 can scrape off the solidified layer within a preset thickness range (optionally 1mm~2mm) while the scraper 16 is separated from the contact pressure plate 15. The thickness of the scraper arm (optionally not less than 2mm) should ensure the rigidity of the scraper 16 during rotation. The aforementioned adjustment of the distance between the scraper 16 and the concentric disc 19 can adjust the distance between the scraper 16 and the inner wall of the tank 3 to be within a preset range (for example, the distance between the scraper 16 and the inner wall of the tank 3 is less than 5mm), ensuring that the rotation direction and speed controlled by the rotary motor 9 can achieve directional scraping of the solidified layer by the scraper 16.
[0052] Therefore, this invention features a tank 3 for storing molten salt phase change material. A semi-circular coil 4 is added to the outer wall of the tank 3 for circulating low-temperature water. A heating module 1 is installed below the tank 3 to heat the molten salt phase change material inside. An active drive module is placed inside the tank 3 and above the upper cover 5. The active drive module includes a pressure lifting unit and an axial rotation thinning unit. The pressure lifting unit is connected to a lifting motor 8, a take-up reel 6, a rope 14, and a steering pulley 12 to lift the contact pressure plate 15, causing the contact pressure plate 15 to apply pressure to the molten salt phase change material inside the tank 3, thus lifting the tank 3. The heat exchange rate between the internal molten salt phase change material and the heating module 1 accelerates the melting of the solid molten salt phase change material. The axial rotation thinning unit achieves adjustable rotation of the scraper 16 through the transmission connection of the rotary motor 9, the first-stage gear transmission pair, and the second-stage gear transmission assembly. This allows the scraper 16 to scrape off the solidified molten salt phase change material adhering to the inner wall of the tank 3, reducing the thermal resistance of the heat release process. This enables efficient heat exchange between the low-temperature water in the semi-circular coil 4 and the high-temperature molten salt phase change material in the tank 3, generating high-temperature steam. Both the pressure lifting unit and the rotation thinning unit adopt an adjustable cyclic active control mode, and both can return to their initial state after the cycle ends.
[0053] More specifically, the active drive module of this molten salt thermal storage device consists of two processes: first, a pressure lifting unit actively drives the molten salt heat storage (melting) process; second, an axial rotation thinning unit actively drives the molten salt heat release (solidification) process. Specifically:
[0054] like Figures 2 to 3 As shown, in this embodiment of the invention, the pressure lifting unit actively drives the molten salt heat storage (melting) process. The heating module 1 is located below the molten salt heat storage module. The heating module 1 uses electric heating to heat the solid molten salt phase change material in the molten salt tank 3. When the heating module 1 starts heating, the lifting motor 8 of the pressure lifting unit is activated to rotate forward. The lifting motor 8 is connected to the take-up reel 6, which drives the rope 14 to slowly descend and contact the pressure plate 15 wound around its other end. The pressure plate 15 contacts the solid molten salt phase change material and applies pressure to the solid molten salt phase change material, pushing the solid molten salt to melt. The salt phase change material and the heating surface of the heating module 1 are always kept in close contact. The liquid molten salt phase change material above the heating surface is squeezed to the top of the tank 3. When the solid molten salt phase change material is completely melted, the contact plate 15 is in contact with the heating surface, and the lifting motor 8 is started to rotate in the opposite direction. The take-up reel 6 pulls the contact plate 15 up through the rope 14. When the contact plate 15 returns to the initial position, the lifting motor 8 turns off the start / stop function, thus completing the entire active driving molten salt heat storage process. When the heat storage process is carried out again, the pressure lifting unit performs the cycle again, improving the heat exchange rate of the solid molten salt phase change material melting process.
[0055] Optionally, the molten salt phase change material can be a binary molten salt or a ternary molten salt.
[0056] Priority should be given to the stopping distance between the contact pressure plate 15 and the upper cover plate 5 of the molten salt tank 3, as well as the distance between the contact pressure plate 15 and the inner wall of the tank 3, so as to allow for the adjustment of the scraper 16, so as to facilitate the precise scraping of the solidification thermal resistance.
[0057] It should be noted that the contact pressure plate 15 has multiple openings in the circumferential direction and is connected by bolts to achieve loading and unloading. Multiple layers of pressure plates can be stacked or reduced on top of the contact pressure plate 15 to increase or decrease the downward pressure.
[0058] Therefore, the pressure lifting unit provided in this embodiment of the invention actively drives the molten salt to store heat. The lifting motor 8 is connected to the take-up reel 6, the steering pulley 12, the rope 14 and the contact pressure plate 15. When the molten salt tank 3 stores heat, the contact pressure plate 15 applies downward pressure to the solid molten salt phase change material to maintain efficient heat exchange between the solid molten salt phase change material and the heat exchange surface.
[0059] like Figure 4 As shown, in this embodiment of the invention, the axial rotation thinning unit actively drives the molten salt heat release (solidification) process. The rotary motor 9 is installed above the upper cover plate 5, and the rotary gear 18 and scraper 16 are both located below the upper cover plate 5. The driving gear is coaxially arranged with the motor shaft of the rotary motor 9, and the driven gear 10 is coaxially arranged with the rotary gear 18. The scraper 16 is positioned and installed on the rotary internal gear ring 21 through the scraper connector, and its edge is in close contact with the inner wall surface of the tank 3. By controlling the direction and speed of the rotary motor 9, the scraper 16 is driven to adhere to the inner wall of the tank 3 and rotate clockwise or counterclockwise.
[0060] like Figure 7 As shown, in this embodiment of the invention, a heat-resistant structure is added at the position where the axial rotating thinning unit contacts the high-temperature molten salt to prevent the high-temperature molten salt from transferring heat to the rotating thinning unit and the equipment above the upper cover plate 5, thus protecting the active drive module to operate stably.
[0061] Preferably, the thickness of the metal insulation outer cylinder 17 should be 3~5mm. The outer edge thickness of the inner insulation material (optional 2~4mm) is thinner than the center thickness (optional 4~9mm). Increasing the center thickness of the inner insulation material can prevent heat from being transferred upwards and ensure the safe operation of the equipment above the top cover plate 5. Example 2
[0062] Please refer to this embodiment. Figure 8 .
[0063] The difference between this embodiment and Embodiment 1 is that the scraper 16 of the axial rotation thinning unit is improved according to different molten salt phase change materials and the solidification state of the inner wall of the tank 3. The cutting edge of the scraper 16 adopts a bidirectional asymmetric design, becoming as follows: Figure 8The bidirectional asymmetric scraper 23 shown reduces the resistance to cutting into the solidified layer on the inner wall of the tank 3. The blade angle is designed to match the rotation direction, which improves the efficiency of scraping off the solidified layer, accelerates the high-temperature molten salt phase change material in the tank 3 and the low-temperature water flowing in the semi-circular coil 4 to maintain efficient heat exchange, and improves the steam temperature and steam power generation efficiency.
[0064] It should be noted that the cutting angle of the bidirectional asymmetric scraper 23 facing the solidified layer is designed to be small (for example, the cutting angle facing the solidified layer can be set to 10°~30°). It uses rotational inertia to quickly cut into the solidified layer, avoiding direct contact between the cutting edge and the solidified layer, thus reducing the initial scraping resistance. The guiding cutting edge away from the solidified layer is designed to be large (for example, the guiding cutting edge away from the solidified layer can be set to 60°~80°). This not only prevents the scraped solidified layer fragments from sticking to the cutting edge in the opposite direction, but also guides the fragments to slide down to the molten salt layer at the bottom of the tank, thus avoiding the accumulation of fragments and increasing the load on the bidirectional asymmetric scraper 23.
[0065] The bidirectional asymmetric scraper 23 includes, but is not limited to, a unidirectional structure with a spiral guide groove design on the cutting edge. The unidirectional structure of the cutting edge has a spiral guide groove on the side away from the solidified layer. The spiral direction of the guide groove is consistent with the rotation direction of the bidirectional asymmetric scraper 23.
[0066] like Figure 9 The figure shown is a comparison of the results of a simplified model (hereinafter referred to as the pressure driving model) constructed based on the working principle of the pressure lifting unit of the active driving module described in this invention and a simplified model of the gravity-driven pressure lifting unit (hereinafter referred to as the gravity driving model, which is driven by the gravity of the solid molten salt phase change material itself) under different experimental conditions. Figure 9 (a) is a simplified structural diagram of a pressure lifting unit based on the working principle of the active drive module described in this invention. In the pressure drive model, the interior is filled with molten salt phase change material, a heating module 1 is set at the bottom, a preheating inlet and an outlet are set on the left and right respectively, and a weight tray 26 is set at the top via a gravity support rod 27 to hold weights, simulating the pressure applied to the internal molten salt phase change material by the contact pressure plate 15. Figure 9Figure (b) shows a comparison of the contact melting results between the pressure-driven model and the gravity-driven model. As can be seen from the figure, in the early stage of melting, both the pressure-driven model and the gravity-driven model maintain the same heat transfer rate, and the average temperature of the heat sink increases in the same direction. As the melting process heats up, the average temperature of the heat sink in the gravity-driven model shows a rapid upward trend, while the average temperature of the heat sink in the pressure-driven model shows a steady upward trend. This is because the contact melting in the pressure-driven model continuously pushes the solid molten salt phase change material towards the heating surface, thereby reducing the melting distance and maintaining a high-efficiency heat flux density. When the contact melting of both the pressure-driven model and the gravity-driven model reaches a quasi-steady state, the average temperature of the heat sink in the pressure-driven model decreases by 51%. It can be seen that, compared with the contact melting in the gravity-driven model, the contact melting in the pressure-driven model has a significant advantage in overall heat transfer performance under the same working conditions, maintaining stable and efficient contact melting heat transfer at the bottom.
[0067] like Figure 10 The figure shown is a simplified model constructed based on the working principle of the axial rotation thinning unit of the active drive module described in this invention, and a comparison of the results under different experimental conditions. Figure 10 (a) is a simplified model constructed based on the working principle of the axial rotary thinning unit of the active drive module described in this invention (hereinafter referred to as the simplified rotary thinning unit). The tank 3 of the simplified rotary thinning unit is filled with molten salt phase change material and equipped with scraper 16. The tank 3 is installed above the base 25, and heat exchange inlet and heat exchange outlet are set on the left and right respectively. The temperature change inside the tank 3 is measured by a thermocouple. The scraper 16 is connected to the rotary motor 9 through a coupling. Figure 10 Figures (b) and (c) show a comparison of the solidification results of the scraper 16 at different rotation speeds. The figures show that at the same time, the temperature with the scraper 16 is lower than without it, and the temperature of the simplified rotary thinning unit gradually decreases with increasing rotation speed. Simultaneously, considering the heat release power at the same time, it is clear that the heat release power without the scraper 16 is lower than with it. When the scraper 16 maintains a rotation speed of 200 rpm, the heat release power is 48.9% higher than without the scraper, while when the scraper 16's rotation speed is increased to 400 rpm, the heat release power is 93.5% higher than without the scraper. Therefore, the scraper 16 can remove the thermal resistance of the solidified layer (i.e., the solid molten salt phase change material) on the inner wall of the tank 3, increasing the heat exchange rate between the heat exchange fluid and the tank 3. Furthermore, as the rotation speed of the scraper 16 increases, the thermal resistance of the solidified layer on the inner wall gradually decreases, maintaining efficient contact solidification heat exchange between the heat exchange fluid and the molten salt phase change material in the tank 3, thus achieving stable and efficient contact solidification heat transfer.
[0068] The preferred embodiments of the present invention disclosed herein are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, numerous modifications and variations can be made based on this specification. This specification selects and specifically describes these embodiments to more clearly explain the principles and practical applications of the invention, thereby helping those skilled in the art to fully understand and rationally utilize the invention. The scope of protection of the present invention is limited only by the claims and their full scope and equivalents.
Claims
1. A molten salt thermal storage device, comprising a molten salt thermal storage module, a heating module, and an active drive module, wherein the molten salt thermal storage module includes a molten salt reservoir for filling with molten salt phase change material; the heating module is disposed below the molten salt reservoir and is in close contact with the bottom of the molten salt reservoir through a high-temperature resistant heat-conducting layer; characterized in that, The active drive module includes a pressure lifting unit and an axial rotation thinning unit, wherein: The pressure lifting unit includes a rope drive device and a contact plate. The rope drive device is installed on the top of the molten salt thermal storage tank, and the contact plate is located inside the molten salt thermal storage tank and connected to the power output end of the rope drive device. Under the power actuation of the rope drive device, the contact plate rises and falls inside the molten salt thermal storage tank. The axial rotation thinning unit includes a rotary motor, a two-stage gear transmission mechanism, and a scraper assembly. The fixed part of the rotary motor is installed on the top of the molten salt heat storage tank, and the power output end is linked to the scraper assembly through the two-stage gear transmission mechanism. Under the power of the rotary motor, the scraper assembly is attached to the inner wall of the tank and rotates clockwise or counterclockwise. A metal insulation outer cylinder is installed below the top of the molten salt thermal storage tank. A fixing ring is installed inside the metal insulation outer cylinder against the wall and is fixedly connected to the top of the molten salt thermal storage tank. The two-stage gear transmission mechanism includes a first-stage gear transmission pair and a second-stage gear transmission pair; wherein: The first-stage gear transmission pair includes a driving gear and a driven gear that mesh with each other, with the rotation axis of the driving gear and the rotation axis of the driven gear being perpendicular to each other. The second-stage gear transmission pair includes a rotary gear and a rotary internal gear ring; the outer wall of the rotary internal gear ring and the inner wall of the fixed ring can be circumferentially rotated, and the inner ring of the rotary internal gear ring is provided with teeth that mesh with the rotary gear; the rotary gear and the driven gear are coaxially connected. The scraper assembly is linked to the rotating internal gear ring; The scraper assembly includes a concentric disc, a scraper connector, and a scraper. The concentric disc is placed above the rotating internal gear ring. There are several scraper connectors, which are evenly arranged along the circumference of the concentric disc. The rotating internal gear ring is provided with a through hole corresponding to the position of each scraper connector. Each scraper connector passes through the corresponding through hole and connects to the upper end of the corresponding scraper. The molten salt thermal storage module also includes a semi-circular coil; the semi-circular coil is attached to the outer surface of the molten salt thermal storage device to form a spirally rising heat exchange channel, and a low-temperature water inlet is arranged below it and a steam outlet is provided above it. The distance between the scraper and the inner wall of the molten salt heat storage tank should ensure that the scraper is separated from the contact pressure plate while the scraper can remove the solidified layer within the preset thickness range.
2. The molten salt thermal storage device according to claim 1, characterized in that, The rope drive device includes a lifting motor, a take-up reel, a steering pulley, and a rope. The lifting motor, take-up reel, and steering pulley are all installed on the top of the molten salt thermal storage tank. Several steering pulleys are required according to their position. The lifting motor is connected to the take-up reel for transmission. One end of the rope is wound around the take-up reel, and the other end passes around each steering pulley in sequence, passes through the top of the molten salt thermal storage tank, and is connected to the contact pressure plate.
3. The molten salt thermal storage device according to claim 2, characterized in that, The molten salt thermal storage module also includes a dome; the dome is arranged on top of the molten salt thermal storage unit to form a storage space; the dome is surrounded by porous walls.
4. The molten salt thermal storage device according to claim 3, characterized in that, The molten salt thermal storage tank includes a tank body, an upper cover plate, and a lower cover plate; the upper and lower ends of the tank body are respectively connected to the upper and lower cover plates, and the upper cover plate has a through hole in the center; The lifting motor, cable reel, and steering pulley are all installed above the upper cover plate; the rope passes through the through hole in the center of the upper cover plate and is connected to the contact pressure plate. The fixed part of the rotary motor is installed above the upper cover plate; The retaining ring is fixed to the upper cover plate; The rotary gear and driven gear are positioned and supported on the upper cover plate by bearings.
5. The molten salt thermal storage device according to claim 2, characterized in that, The scraper blade adopts a bidirectional asymmetric design: the cutting angle of the scraper blade facing the solidified layer is smaller than the guiding blade angle away from the solidified layer.
6. An active heat transfer enhancement method, implemented based on the molten salt thermal storage device of claim 1, characterized in that, It includes an actively driven molten salt heat storage process and an actively driven molten salt heat release process. The actively driven molten salt heat storage process is realized based on a pressure lifting unit, and the actively driven molten salt heat release process is realized based on an axial rotation thinning unit. Specifically, it includes the following steps: Step S1: Fill the molten salt thermal storage tank with solid molten salt phase change material; Step S2: Start the heating module to heat the solid molten salt phase change material in the molten salt heat storage tank; Step S3: Activate the pressure lifting unit and control the contact plate to descend at a preset rate. The contact plate contacts the solid molten salt phase change material and applies pressure to it, pushing the solid molten salt phase change material to maintain close contact with the heating surface of the heating module. The liquid molten salt phase change material above the heating surface is squeezed to the top of the molten salt heat storage tank until the solid molten salt phase change material is completely melted. When the contact plate is in contact with the heating surface, control the pressure lifting unit to move in the opposite direction to drive the contact plate back to the initial position and stop the pressure lifting unit. During this process, activate the axial rotation thinning unit to drive the scraper assembly to rotate clockwise or counterclockwise against the inner wall of the tank to scrape off the solidified molten salt layer attached to the inner wall of the molten salt heat storage tank, reducing the thermal resistance of the heat release process.