A new type of tubular phase change thermal storage unit and method with inner tube rotation

Abstract

The application discloses a novel tubular phase change energy storage unit with rotating inner tube and a method, which comprises an outer tube, an inner tube, a rotating driving mechanism, a rotating joint assembly, an end sealing device, a supporting device and a control system. The shell is filled with phase change material, and the inner tube is coaxially arranged in the shell and initially contacts with the solid phase change material. During heat storage, the hot fluid is introduced into the inner tube, and the solid phase change material near the outer wall of the inner tube is melted to form a dynamic expanding annular gap; the inner tube rotates in the annular gap to excite Taylor vortex, and the radial flow of the Taylor vortex efficiently transfers heat to the solid-liquid interface, accelerates melting and expands the annular gap outward. The inner tube is a smooth round tube without fins or blades. The end sealing device adopts a double-cavity isolation sealing structure, which simultaneously meets the sealing requirements of the solid and liquid phase change materials. The application solves the heat transfer bottleneck of the phase change material and the problem of the decreased heat storage capacity caused by the addition of fins, and has the advantages of high heat transfer efficiency, simple structure, reliable sealing and the like.

Description

Technical Field

[0001] This invention relates to the field of phase change thermal energy storage technology, specifically to a novel tubular phase change energy storage unit and method with rotating inner tube, which is particularly suitable for occasions requiring the storage and release of thermal energy, such as solar thermal utilization, industrial waste heat recovery, power grid peak shaving, and building heating. Background Technology

[0002] In the fields of renewable energy utilization and industrial energy conservation, there is often a mismatch between energy supply and demand in terms of time, space, and intensity. Thermal energy storage technology, as an effective means to resolve this contradiction, has become a research hotspot in the field of energy utilization. Among them, phase change thermal energy storage technology utilizes the characteristic of phase change materials (PCMs) to absorb or release a large amount of latent heat during phase change, exhibiting significant advantages such as high thermal energy storage density and constant temperature during the heat storage and release process.

[0003] Shell-and-tube structures are one of the most common forms of phase change thermal storage units. They typically use an inner tube through which a heat transfer fluid flows, and the annular space between the shell and the inner tube is filled with a phase change material. However, most phase change materials have low thermal conductivity, resulting in a large thermal resistance when heat is transferred between the inner tube wall and the phase change material far from the inner tube, which severely limits the heat storage and release rates.

[0004] To overcome the above problems, various heat transfer enhancement schemes have been proposed in the prior art, mainly including: (1) adding fins, spiral blades and other extended surface structures to the outer wall of the inner tube to increase the heat exchange area; (2) doping the phase change material with a high thermal conductivity medium (such as expanded graphite, foamed metal); (3) using methods such as rotation stirring or vibration to enhance convection. However, these schemes still have the following shortcomings:

[0005] First, while adding fins or blades increases the heat exchange area, the structure is complex and the manufacturing cost is high. Furthermore, the temperature difference between the root and tip of the fins limits the actual heat enhancement effect. More importantly, these additional structures reduce the effective filling volume of the phase change material, thus decreasing the overall heat storage capacity.

[0006] Secondly, while doping phase change materials with high thermal conductivity media can improve the equivalent thermal conductivity, it will reduce the heat storage density of the phase change materials and cause problems such as sedimentation and agglomeration.

[0007] Furthermore, existing rotary stirring solutions typically employ impellers, which pose a risk of jamming during startup in solid-phase PCMs, and the impeller structure increases fluid resistance and energy consumption.

[0008] Furthermore, existing technologies do not adequately address the end-sealing issues of phase change thermal energy storage units. Phase change materials undergo significant volume changes during solid-liquid phase transitions and exhibit high hardness in the solid phase, posing a severe challenge to rotary dynamic seals—the seals must prevent leakage of the liquid PCM while also preventing wear or jamming of the solid PCM at the sealing surface.

[0009] Therefore, there is an urgent need in this field for a phase change thermal storage unit that is simple in structure, has no additional fins, can adapt to the solid-liquid phase change process, is reliably sealed, and has high heat transfer efficiency. Summary of the Invention

[0010] To address the aforementioned shortcomings in the existing technology, this invention provides a novel tubular phase change energy storage unit and method with an inner tube rotation. This energy storage unit has a simple structure, reliable sealing, and high heat transfer efficiency.

[0011] To achieve the above objectives, the present invention provides the following technical solution:

[0012] A novel tubular phase change energy storage unit with rotating inner tube includes a shell, an inner tube, an end cap, a rotation drive mechanism, a rotary joint assembly, an end sealing device, a support device, and a control system.

[0013] The shell is provided with end caps at both ends, and the inner tube is coaxially disposed inside the shell. The space between the shell interior and the outer wall of the inner tube is filled with phase change material, and the outer wall of the inner tube is initially in contact with the phase change material.

[0014] The rotary drive mechanism is connected to the inner tube via gears, and is used to drive the inner tube to rotate around its axis; the rotary joint assembly is disposed at at least one end of the inner tube, and is used to introduce hot fluid from an external stationary pipe into the rotating inner tube, and to...

[0015] Heat fluid removal;

[0016] The end sealing device is disposed at both ends of the housing and is used to seal the phase change material inside the housing when the inner tube is rotating and stationary.

[0017] The support device is located at both ends of the inner tube and the lower end of the shell, and is used to support the shell and the inner tube and maintain the coaxiality of the shell and the inner tube.

[0018] The control system is connected to the motor of the rotary drive mechanism and is used to control the start-up, shutdown, and rotational speed of the inner tube.

[0019] In the above scheme, the inner tube is a smooth circular tube with no additional fins or blades on the outer surface; the phase change material is selected from materials with solid-liquid phase change characteristics within the heat storage temperature range. During heat storage, the phase change material melts from a solid to a liquid state; during heat release, it solidifies from a liquid state to a solid state.

[0020] In the above scheme, the end sealing device includes a sealing housing, a first sealing cavity and a second sealing cavity disposed within the sealing housing, and an isolation ring disposed between the first sealing cavity and the second sealing cavity;

[0021] The first sealing cavity is filled with an isolation fluid; the second sealing cavity is provided with a sealing assembly; a heating device is provided on the outside of the sealing housing; the sealing assembly is a replaceable structure, and the sealing housing and the end cap are connected by a flange;

[0022] The isolation fluid is heat-conducting oil or silicone oil; the heating device is an electric heating tape or a heating jacket; the sealing assembly is a mechanical seal assembly or a packing seal assembly.

[0023] In the above scheme, the support device includes two pairs of fixed-end supports; the fixed-end supports include paired angular contact ball bearings.

[0024] In the above scheme, the rotary drive mechanism includes a motor, a driving gear, and a driven gear;

[0025] The driven gear is mounted on one end of the inner tube via a keyway; the motor is a variable frequency motor and is electrically connected to the control system.

[0026] In the above scheme, the control system includes a controller and a temperature sensor;

[0027] The temperature sensor is located on the outer wall of the housing and / or the outlet end of the inner tube, and is used to detect the temperature state of the phase change material and transmit it to the controller;

[0028] The controller determines the formation and expansion process of the dynamically expanding annular gap based on the temperature sensor signal, and controls the rotational speed of the inner tube.

[0029] A phase change thermal energy storage method for a novel tubular phase change energy storage unit based on the rotation of the inner tube includes the following steps:

[0030] Initial state: The shell is filled with phase change material, and the outer wall of the inner tube is in contact with the phase change material.

[0031] touch;

[0032] Initiating thermal storage: Hot fluid is introduced into the inner tube, and the phase change material near the outer wall of the inner tube absorbs heat and begins to melt, forming a dynamic expanding annular gap between the outer wall of the inner tube and the surrounding phase change material.

[0033] Initiating rotation: The control system initiates the rotation drive mechanism to drive the inner tube to rotate, thereby stimulating Taylor vortices in the liquid phase change material within the dynamically expanding annular gap to form a Taylor vortex generation region.

[0034] Taylor vortex-enhanced heat transfer: The radial circulating flow of Taylor vortexes efficiently transfers heat from the outer wall of the inner tube to the solid-phase interface at the outer edge of the dynamically expanding annular gap, accelerating solid-phase melting and causing the width of the dynamically expanding annular gap to gradually expand outward.

[0035] Continuous heat storage: As the solid-phase interface continues to move outward, the width of the dynamically expanding annular gap gradually increases. The control system adjusts the inner tube speed according to temperature feedback to maintain the full development of the Taylor vortex.

[0036] Heat release phase: Stop the flow of hot or cold fluid, keep the inner tube rotating, and use Taylor vortices to slow down the growth of the solidified layer on the outer wall of the inner tube; when the latent heat release is determined to be complete, stop the rotation of the inner tube.

[0037] In the above scheme, during the starting rotation step, the timing of starting rotation of the inner tube is any one of the following:

[0038] When the temperature sensor detects that the rate of increase of the water temperature at the inner pipe outlet has slowed down and the temperature of the outer wall of the shell has begun to rise, it is determined that the dynamic expansion annular gap has been initially formed, and rotation is started; wherein, the slowing down means that the rate of increase of the outlet water temperature decreases to below 0.05~0.1℃ / s and lasts for 10~30 seconds, and the beginning of the rise means that the rate of increase of the shell wall temperature reaches above 0.02~0.05℃ / s and lasts for 10~20 seconds;

[0039] Monitor the temperature of the outer wall of the inner tube. When the temperature rise rate of the outer wall of the inner tube is below 0.1℃ / s for 30 consecutive seconds and the temperature of the outer wall of the inner tube has exceeded the melting point of the phase change material by 3~5℃, start the rotation. Alternatively, preset a basic melting time. After the time is reached, jog the rotation at a speed of 10~20rpm and monitor the motor current. If the current does not exceed 130% of the rated value, continue the rotation. If it does, stop heating and try again.

[0040] In the above scheme, during the continuous heat storage step, the control system adjusts the inner tube rotation speed based on the estimated width of the dynamically expanding annular gap. Specifically, when the radius of the dynamically expanding annular gap is less than 1 / 3 of the difference between the shell and the inner tube radius, the rotation speed is maintained at 80~100 rpm; when the radius of the dynamically expanding annular gap is between 1 / 3 and 2 / 3 of the difference between the shell and the inner tube radius, the rotation speed is increased to 120~150 rpm; and when the radius of the dynamically expanding annular gap is greater than 2 / 3 of the difference between the shell and the inner tube radius, the rotation speed is increased to 150~200 rpm.

[0041] In the above scheme, during the heat release stage, the method for determining the completion of latent heat release is as follows: monitor the temperature rise rate of the cold fluid at the inner tube outlet and / or the outer wall temperature of the shell. When the outer wall temperature decreases by 10% or more compared to the temperature at which melting is completed, or when the temperature rise rate of the cold fluid at the inner tube outlet remains below 0.02℃ / s for 2 minutes, the latent heat release is determined to be complete, and the rotation of the inner tube is stopped.

[0042] Compared with the prior art, the beneficial effects of the present invention are:

[0043] 1. This invention utilizes the heating of the inner tube to cause the surrounding solid PCM to melt spontaneously, forming a dynamically expanding annular gap. The width of the annular gap gradually increases with the heat storage process. The rotation of the inner tube generates Taylor vortices within this annular gap. The radial flow of the Taylor vortices efficiently transfers heat to the solid-phase interface at the outer edge of the annular gap, increasing the solid-phase melting rate several times compared to pure heat conduction. The dynamically expanding annular gap provides space for the development of Taylor vortices, which in turn accelerate the expansion of the annular gap, forming a positive feedback loop that achieves enhanced heat transfer throughout the entire process.

[0044] 2. The inner tube of this invention is a smooth round tube, which eliminates the need for processing fins or blades, thus completely eliminating the risk of blade jamming. The structure is simple, with no additional parts, and it is easy to manufacture and has low cost.

[0045] 3. Adaptive control with strong adaptability to operating conditions: This invention dynamically adjusts the inner tube speed based on temperature feedback, ensuring the Taylor vortex is always fully developed and adapts to changes in the annular gap width. Compared to a fixed speed solution, the enhancement effect is more stable.

[0046] 4. This invention employs a dual-cavity isolation and sealing structure. The isolation fluid in the first sealing cavity forms a liquid barrier, preventing PCM from entering the sealing area; the mechanical seal in the second sealing cavity is responsible for rotational sealing; and the heating device ensures that the temperature of the sealing cavity is higher than the melting point of the PCM. This design simultaneously solves the problems of wear on the seals caused by solid PCM and leakage from liquid PCM.

[0047] 5. The present invention adopts a double bearing support structure, which can prevent abnormal displacement of the inner tube in the radial and axial directions, and facilitates the installation and disassembly of the inner shell. Attached Figure Description

[0048] Figure 1 This is a schematic diagram (axial sectional view) of the overall structure of an embodiment of the present invention.

[0049] Figure 2 for Figure 1 A schematic diagram of the radial section of the inner tube AA, showing the initial and intermediate states (inner tube in contact with solid PCM).

[0050] Figure 3 for Figure 1 A schematic diagram of the axial section of the middle BB shows the axial manifestation of the dynamically expanding annular gap and the Taylor vortex structure;

[0051] Explanation of the reference numerals in the figure:

[0052] 1. Shell; 2. Inner tube; 3. End cap; 4. First sealing cavity; 5. Second sealing cavity; 6. Sealing end cap; 7. Rotary joint; 8. Driven gear; 9. Driving gear; 10. Outlet pipe section; 11. Inlet pipe section; 12. Fixing device; 13. Angular contact ball bearing; 14. Keyway; 15. Phase change material; 16. Variable frequency motor; 31. Dynamically expanding annular gap; 32. Taylor vortex generation region. Detailed Implementation

[0053] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0054] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0055] This invention aims to solve the following technical problems: In existing phase change thermal energy storage units, the inner tube is in direct contact with the solid PCM, and heat transfer relies solely on conduction, resulting in an extremely slow rate; existing heat transfer enhancement schemes require the addition of fins or blades to the outer wall of the inner tube, which is structurally complex, poses a risk of jamming, and reduces the total heat storage capacity; existing technologies do not fully consider the volume changes during the solid-liquid phase change process of phase change materials and the special requirements for the sealing system; existing rotary dynamic sealing schemes are difficult to adapt to the sealing requirements of both solid and liquid phase change materials simultaneously.

[0056] Figure 1 The figure shows a preferred embodiment of the novel tubular phase change energy storage unit with inner tube rotation according to the present invention. The novel tubular phase change energy storage unit with inner tube rotation includes a shell 1, an inner tube 2, an end cap 3, a rotation drive mechanism, a rotary joint assembly, an end sealing device, a support device, and a control system.

[0057] The housing 1 has end caps 3 at both ends. The inner tube 2 is coaxially arranged inside the housing 1. A phase change material 15 is filled between the inside of the housing 1 and the outer wall of the inner tube 2. Initially, the outer wall of the inner tube 2 is in contact with the phase change material 15. The rotary drive mechanism is connected to the inner tube 2 via gears and is used to drive the inner tube 2 to rotate around its axis. The rotary joint assembly is arranged at at least one end of the inner tube 2 and is used to introduce hot fluid from an external stationary pipeline into the rotating inner tube 2 and to discharge the hot fluid. The end sealing device is arranged at both ends of the housing 1 and is used to seal the phase change material 15 inside the housing 1 when the inner tube 2 is rotating and stationary. The end sealing device can simultaneously meet the sealing requirements of solid and liquid phase change materials. The support device is arranged at both ends of the inner tube 2 and the lower end of the housing 1 and is used to support the housing 1 and the inner tube 2 and maintain their coaxiality. The control system is connected to the motor of the rotary drive mechanism and is used to control the start, stop and rotation speed of the inner tube 2.

[0058] The shell 1 is a cylindrical structure made of metal materials (such as stainless steel or carbon steel).

[0059] The inner tube 2 is a smooth circular tube made of a material with good thermal conductivity (such as copper, stainless steel, or aluminum alloy). The outer surface of the inner tube 2 has no additional fins or blades. The outer diameter of the inner tube 2 is smaller than the inner diameter of the shell 1.

[0060] The end cap 3 has a through hole to accommodate the inner tube 2 and the end sealing device. The end cap 3 and the housing 1 are connected by a flange.

[0061] In its initial state, the interior of the shell 1 is filled with solid phase change material 15, and the outer wall of the inner tube 2 is directly and tightly bonded to the phase change material 15, such as... Figure 2 As shown, the annular gap (dynamically expanding annular gap) formed during the initial melting stage is entirely occupied by the molten liquid phase change material itself. This liquid phase change material does not need to be discharged to other areas; it serves as the lubrication and heat transfer medium between the inner tube 2 and the surrounding solid phase change material. When the inner tube 2 rotates, Taylor vortices are generated within this liquid layer, thereby enhancing heat transfer.

[0062] In this invention, the phase change material 15 is selected from materials that have solid-liquid phase change characteristics within the heat storage temperature range. During heat storage, the phase change material melts from a solid state to a liquid state; during heat release, it solidifies from a liquid state to a solid state.

[0063] Preferably, the phase change material 15 is paraffin wax with a melting point of 58°C and a solidification shrinkage rate of approximately 12%. Hydrated salts, fatty acids, or other multi-element eutectic mixtures may also be used; preferably, the initial filling rate is 90%.

[0064] The end sealing device is located at both ends of the inner shell connection. The end sealing device includes a sealing shell, a first sealing cavity 4 and a second sealing cavity 5 disposed within the sealing shell, and an isolation ring disposed between the first sealing cavity 4 and the second sealing cavity 5. The first sealing cavity 4 is filled with an isolation fluid that is incompatible with the phase change material 15 and remains liquid within the operating temperature range. A sealing assembly is disposed within the second sealing cavity 5. A heating device is disposed on the outside of the sealing shell to maintain the temperature of the sealing cavity above the melting point of the phase change material 15. The sealing assembly is a replaceable structure, and the sealing shell and the end cap 3 are connected by a flange. The isolation fluid is heat transfer oil or silicone oil. The heating device is an electric heating tape or a heating jacket. The sealing assembly is a mechanical seal assembly or a packing seal assembly.

[0065] In one specific embodiment of the present invention, the sealing housing is connected to the end of the housing via a flange or thread, forming a sealing cavity between the sealing housing and the inner tube 2. The sealing housing and the end cover 3 are connected via a flange, facilitating disassembly and maintenance.

[0066] The first sealing cavity 4 (near the phase change material 15): The cavity of the first sealing cavity 4 is filled with an isolation fluid that is incompatible (immiscible) with the phase change material 15 and remains liquid within the operating temperature range (120°C). In this embodiment, methyl silicone oil is used, which has a freezing point below 50°C, a boiling point above 200°C, and is chemically inert. The first sealing cavity 4 and the phase change material 15 are connected by a narrow annular gap, and the isolation fluid forms a liquid barrier to prevent the phase change material 15 from entering the subsequent sealing area.

[0067] The second sealing cavity 5 (away from the phase change material 15): A mechanical seal assembly is installed inside the second sealing cavity 5. The mechanical seal uses a silicon carbide rotating ring paired with a graphite stationary ring, with a maximum temperature resistance of 150℃ and a pressure resistance of 1.0MPa. The rotating end of the mechanical seal is connected to the inner tube 2, and the stationary end is fixed to the sealing shell. The mechanical seal assembly is a replaceable structure.

[0068] The isolation ring is disposed between the first sealing cavity 4 and the second sealing cavity 5. It is an annular metal part with a gap of 0.5~1mm between its inner diameter and the inner tube 2. It is used to reduce the leakage of the isolation fluid into the second sealing cavity 5 and at the same time prevent wear particles of the mechanical seal from entering the phase change material 15.

[0069] The heating device is installed on the outside of the sealed housing 1, wrapped with electric heating tape, and covered with an insulation layer. The heating device is controlled by a temperature controller, and the set temperature is 510°C higher than the melting point of the phase change material 15 (65°C in this embodiment) to ensure that the temperature of the sealed cavity is always higher than the melting point of the phase change material 15, preventing the phase change material 15 from solidifying at this point.

[0070] Working process: At the start of heat storage, the heating device preheats the fluid in the first sealing cavity 4 to 65°C. When the phase change material 15 melts, an interface is formed between the liquid phase change material 15 and the isolation fluid at the inlet of the first sealing cavity 4. Due to their immiscibility and the slightly higher density of the isolation fluid (silicone oil approximately 0.96 g / cm³, liquid paraffin approximately 0.78 g / cm³), the isolation fluid effectively prevents the phase change material 15 from entering the sealing cavity. Even if a small amount of phase change material 15 seeps in, it remains liquid due to the high temperature and will not clog or wear the mechanical seal. When the inner tube 2 rotates, the mechanical seal assembly is responsible for the rotating dynamic seal, resulting in minimal leakage.

[0071] The rotary joint assembly includes a rotary joint 7, which is disposed at at least one end of the inner pipe 2 for introducing hot water from an external stationary pipe into the rotating inner pipe 2.

[0072] This embodiment employs two single-channel rotary joints 7, installed at both ends of the inner tube 2. The rotary joint 7 uses a graphite silicon carbide mechanical seal, resistant to 120℃ and 1.0MPa. The rotating end of the rotary joint 7 is connected to the end of the inner tube 2 via a left-hand fine-pitch thread, rotating in the opposite direction to prevent loosening during operation. A high-temperature anti-seize agent is applied to the threaded connection, and a lock nut is used for tightening. The stationary end of the rotary joint 7 is connected to the inlet pipe section 11 and the outlet pipe section 10 via stainless steel flexible metal hoses. The inlet pipe section 11 is used to introduce external hot fluid, and the outlet pipe section 10 is used to discharge the heat-exchanged fluid. The flexible metal hoses absorb installation errors and thermal expansion stress.

[0073] Support devices are located at both ends of the inner tube 2, employing a double-bearing, end-fixed layout. The support devices include two pairs of fixed-end supports; each fixed-end support includes paired angular contact ball bearings 13, used to withstand radial and axial forces and determine the axial reference position of the inner tube 2; the angular contact ball bearings 13 are installed within a fixed device 12, which has a housing support frame and bearing seats to provide a stable mounting base for the bearings. The angular contact ball bearings 13 are lubricated with high-temperature grease. Figure 1 As shown on the right, fixed end supports are located at both ends of the inner tube 2. These include a pair of back-to-back (DB) angular contact ball bearings 13, mounted within bearing housings. The inner ring is secured to the shoulder of the inner tube 2 by a lock nut, and the outer ring is pressed against the bearing housing end cap. This support defines the axial reference position of the inner tube 2 and withstands radial and bidirectional axial forces.

[0074] Bearing lubrication: Angular contact ball bearing 13 is lubricated with high temperature grease, which is synthetic oil-based polyurea grease (temperature range: -30℃~160℃), and the filling amount is 30%~50% of the bearing cavity volume.

[0075] The rotary drive mechanism includes a motor, a driving gear 9, and a driven gear 8; the driven gear 8 is mounted on one end of the inner tube 2 via a keyway 14; the motor is a variable frequency motor 16, which is electrically connected to the control system.

[0076] Driven pulley 8 is fixedly installed on the fixed end support side of inner tube 2 (opposite to or on the same side as rotary joint 7, towards the outside). Variable frequency motor 16 is fixed on the support frame of housing 1, and the speed of variable frequency motor 16 is adjusted by the control system, preferably in the range of 0~300 rpm.

[0077] The control system includes a controller and a temperature sensor; the temperature sensor is located on the outer wall of the housing 1 and / or the outlet end of the inner tube 2, and is used to detect the temperature state of the phase change material 15 and transmit it to the controller; the controller determines the formation and expansion process of the dynamic expansion annular gap 31 based on the temperature sensor signal and controls the rotation speed of the inner tube 2.

[0078] A phase change thermal energy storage method for a novel tubular phase change energy storage unit based on the rotation of the inner tube includes the following steps:

[0079] Initial state: The shell 1 is filled with phase change material 15, and the outer wall of the inner tube 2 is in contact with the phase change material 15.

[0080] touch;

[0081] Start-up of thermal storage: hot fluid is introduced into the inner tube 2, and the phase change material 15 near the outer wall of the inner tube 2 absorbs heat and begins to melt, forming a dynamic expanding annular gap 31 between the outer wall of the inner tube 2 and the outer phase change material 15.

[0082] Rotation start: The control system starts the rotation drive mechanism to drive the inner tube 2 to rotate, thereby exciting Taylor vortices in the liquid phase change material within the dynamically expanding annular gap 31 and forming a Taylor vortex generation region 32.

[0083] Taylor vortex enhanced heat transfer: The radial circulating flow of Taylor vortex efficiently transfers the heat from the outer wall of the inner tube 2 to the solid phase interface at the outer edge of the dynamically expanding annular gap 31, accelerating the solid phase melting and causing the width of the dynamically expanding annular gap 31 to gradually expand outward.

[0084] Continuous heat storage: As the solid-phase interface continues to move outward, the width of the dynamically expanding annular gap 31 gradually increases. The control system adjusts the rotation speed of the inner tube 2 according to the temperature feedback to maintain the full development of the Taylor vortex.

[0085] Heat release phase: Stop the flow of hot or cold fluid, keep the inner tube 2 rotating, and the Taylor vortex delays the growth of the solidified layer on the outer wall of the inner tube 2; when the latent heat release is determined to be complete, stop the rotation of the inner tube 2.

[0086] During the rotation initiation process, the timing for initiating rotation of the inner tube 2 is as follows:

[0087] When the temperature sensor detects that the rate of increase of the water temperature at the inner pipe outlet has slowed down and the temperature of the outer wall of the shell 1 has begun to rise, it is determined that the dynamic expansion annular gap 31 has been initially formed, and rotation is started; wherein, the slowing down means that the rate of increase of the outlet water temperature decreases to below 0.05~0.1℃ / s and lasts for 10~30 seconds, and the beginning of the rise means that the rate of increase of the shell wall temperature reaches above 0.02~0.05℃ / s and lasts for 10~20 seconds;

[0088] The timing for initiating rotation can also be determined using the following alternative or supplementary criteria:

[0089] The temperature of the outer wall of the inner tube 2 is monitored by rotating a slip ring, infrared thermometer, or wireless thermometer. When the temperature rise rate of the outer wall of the inner tube 2 is below 0.1℃ / s for 30 consecutive seconds and the temperature of the outer wall of the inner tube 2 exceeds the melting point of the phase change material by 3~5℃, rotation is started. Alternatively, a basic melting time is preset. After the time is reached, the tube is jogged at a speed of 10~20rpm and the motor current is monitored. If the current does not exceed 130% of the rated value, rotation is maintained. If it does, heating is stopped and the process is repeated.

[0090] During the continuous heat storage step, the control system adjusts the rotational speed of the inner tube 2 based on the estimated width of the dynamic expansion annular gap 31. When the radius of the dynamic expansion annular gap 31 is less than 1 / 3 of the radius difference between the shell 1 and the inner tube 2, the rotational speed is maintained at 80~100 rpm; when the radius of the dynamic expansion annular gap 31 is between 1 / 3 and 2 / 3 of the radius difference between the shell 1 and the inner tube 2, the rotational speed is increased to 120~150 rpm; when the radius of the dynamic expansion annular gap 31 is greater than 2 / 3 of the radius difference between the shell 1 and the inner tube 2, the rotational speed is increased to 150~200 rpm.

[0091] In the heat release stage, the method to determine the completion of latent heat release is as follows: monitor the temperature rise rate of the cold fluid at the outlet of inner tube 2 and / or the outer wall temperature of shell 1. When the outer wall temperature decreases by 10% or more compared with the temperature when melting is completed, or when the temperature rise rate of the cold fluid at the outlet of inner tube 2 is below 0.02℃ / s for 2 minutes, the latent heat release is determined to be complete, and the rotation of inner tube 2 is stopped.

[0092] In one specific embodiment of the present invention, 3 to 5 thermocouples are arranged axially on the outer wall of the shell 1 to monitor the wall temperature of the shell 1. A thermocouple is placed at the outlet end of the inner tube 2 to monitor the outlet water temperature.

[0093] Working principle:

[0094] The shell 1 is filled with solid paraffin wax (below 58℃), and the outer wall of the inner tube 2 is in direct contact with the solid paraffin wax. At this time, the inner tube 2...

[0095] still.

[0096] Hot water at 90°C is introduced into the inner tube 2. The solid paraffin near the outer wall of the inner tube 2 absorbs heat, and its temperature rises above its melting point, causing it to melt. Due to the low thermal conductivity of paraffin, the heat mainly accumulates near the inner tube 2, forming a thin layer of liquid paraffin. This liquid layer creates an initial annular gap, i.e., a dynamically expanding annular gap 31, between the inner tube 2 and the surrounding solid paraffin. During this stage, the inner tube 2 remains stationary.

[0097] The controller monitors the outlet water temperature of inner tube 2 and the shell wall temperature. When the rate of increase of the outlet water temperature of inner tube 2 slows down (indicating a decrease in the temperature difference between the inner tube 2 wall and the solid phase change material 15) and the shell wall temperature begins to rise slowly (indicating that heat has begun to be transferred to the shell), it is determined that the dynamic expansion annular gap 31 has been initially formed (typically the annular gap width is about 1~2mm). The motor is started to drive the inner tube 2 to rotate at a low speed (e.g., 50rpm). In practical applications, if the inlet water temperature fluctuates greatly or the flow rate is too high, resulting in insignificant changes in the outlet water temperature, one or a combination of the following alternative or supplementary criteria can be used: detect the outer wall temperature of inner tube 2 (by rotating the slip ring or wireless temperature measurement), and start rotation when the rate of increase of the outer wall temperature of inner tube 2 is below 0.1℃ / s for 30 consecutive seconds; preset a minimum heating time (e.g., 2min), and after the time is reached, attempt to jog the rotation at a very low speed (10~20rpm) regardless of the temperature change. If the current is normal, maintain rotation; if overloaded, pause and continue heating. This scheme can completely avoid the risk of failure to start due to an insignificant temperature signal.

[0098] In one specific embodiment of the present invention, the determination of the timing for initiating rotation is as follows:

[0099] The controller monitors the outlet water temperature of the inner tube 2 and the outer wall temperature of the shell 1 in real time. When both of the following conditions are met simultaneously, it is determined that the solid phase change material 15 near the outer wall of the inner tube 2 has initially melted to form a dynamically expanding annular gap 31. At this time, the rotary drive mechanism is activated to prevent the inner tube 2 from getting stuck in the solid phase change material:

[0100] (i) The rate of increase of the outlet water temperature in the inner pipe slows down significantly. In the initial stage of normal heating, the rate of increase of the outlet water temperature is about 0.2~0.5℃ / s (the specific value depends on the flow rate of the hot fluid and the inlet temperature); when the rate of increase decreases to ≤0.05~0.1℃ / s and lasts for 10~30 seconds, it is judged as "slowing down".

[0101] (ii) The outer wall temperature of shell 1 begins to rise at a positive rate. Initially, the rate of temperature rise of the outer wall is 0 or negative (due to heat dissipation from the environment); when the rate of rise is ≥0.02~0.05℃ / s and lasts for 10~20 seconds, it is determined that "the temperature has started to rise".

[0102] As a supplement to or alternative to the above temperature criterion, the following methods can also be used to determine the start-up timing:

[0103] Inner tube outer wall temperature monitoring: The temperature of the outer wall of the inner tube 2 is monitored by rotating slip ring, infrared thermometry, or wireless thermometry. When the temperature rise rate of the outer wall of the inner tube is below 0.1℃ / s for 30 consecutive seconds, and the temperature of the outer wall of the inner tube has exceeded the melting point of the phase change material by 3~5℃, rotation is started.

[0104] Fixed minimum heating time + inching test: A preset basic melting time is established (e.g., 2-5 minutes, depending on the temperature of the hot fluid and the thermal conductivity of the phase change material). Once this time is reached, the control system attempts inching rotation at a very low speed (10-20 rpm) while monitoring motor current or torque feedback. If the motor current is normal and there is no overload indication (e.g., current does not exceed 130% of the rated value), rotation is maintained and the system enters normal operating mode. If the current exceeds 30% of the rated value or the speed feedback is abnormal, rotation stops, heating continues for 1 minute, and the system tries again until successful startup.

[0105] The specific values ​​in the above criteria (such as temperature change rate, duration, minimum heating time, etc.) are all exemplary parameters. Those skilled in the art can optimize and adjust them through a limited number of conventional tests based on the type of phase change material used, the temperature of the heat fluid, the size of the equipment, and the environmental conditions.

[0106] After the inner tube 2 rotates, the liquid paraffin within the dynamically expanding annular gap 31 is subjected to shear and centrifugal forces. When the rotational speed of the inner tube 2 reaches the speed corresponding to the critical Taylor number, Taylor vortices are excited within the dynamically expanding annular gap 31, such as... Figure 3 As shown, the Taylor vortex is a series of axisymmetric, counter-rotating annular vortex cells. Each vortex cell has a strong radial flow component; the fluid near the inner tube 2 wall flows towards the outer edge, while the fluid near the solid-phase interface flows towards the inner tube 2 wall. The radial flow of the Taylor vortex efficiently transfers heat from the inner tube 2 wall to the solid-phase interface at the outer edge of the dynamically expanding annular gap 31, causing the paraffin at the solid-phase interface to rapidly absorb heat and melt. Simultaneously, the temperature distribution within the annular gap is more uniform, avoiding thermal stratification caused by natural convection.

[0107] As the solid-phase interface continues to move outward, the width of the dynamically expanding annular gap 31 gradually increases. The size of the Taylor vortex is proportional to the annular gap width, so the vortex cell size adapts to the annular gap change. However, the intensity of the Taylor vortex is related to the rotational speed and the annular gap width. When the annular gap increases, maintaining the same Taylor number requires increasing the rotational speed. The rotational speed of the inner tube 2 can be dynamically adjusted based on temperature feedback and a preset model. For example: when the radius of the dynamically expanding annular gap 31 is less than 1 / 3 of the difference between the radii of the shell 1 and the inner tube 2, the rotational speed is maintained at 80~100 rpm; when the radius of the dynamically expanding annular gap 31 is between 1 / 3 and 2 / 3 of the difference between the radii of the shell 1 and the inner tube 2, the rotational speed is increased to 120~150 rpm; when the radius of the dynamically expanding annular gap 31 is greater than 2 / 3 of the difference between the radii of the shell 1 and the inner tube 2, the rotational speed is increased to 150~200 rpm. This control strategy ensures that the Taylor vortex is always fully developed, achieving efficient radial heat transfer.

[0108] When the solid-phase interface reaches the inner wall of shell 1, all the paraffin wax is completely melted. At this time, the temperature sensor shows that the shell wall temperature is close to the outlet water temperature of inner tube 2. The controller can continue to maintain the rotation of inner tube 2 for a period of time, using Taylor vortex to enhance the sensible heat transfer between liquid paraffin wax and inner tube 2, so as to further homogenize the paraffin wax temperature.

[0109] When heat release is required, the flow of hot water is stopped or switched to cold water (or room temperature fluid). Inner tube 2 continues to rotate (the speed can be adjusted as needed), and Taylor vortices continue to act. In the initial stage of heat release, the temperature of liquid paraffin decreases, and the radial flow of Taylor vortices disrupts the temperature boundary layer near the wall, delaying the formation of the solidified layer. As the temperature drops below the melting point, solidification begins, but the disturbance of Taylor vortices can inhibit the rapid growth of the solidified layer on the outer wall of inner tube 2, allowing the heat release power to be maintained for a longer period of time. As the solidified layer gradually thickens and the annular gap width decreases, the controller can reduce the speed to adapt to the changes in the annular gap.

[0110] During the latent heat release process, the inlet and outlet fluid temperatures and the outer wall temperature of the inner tube remain essentially constant. When the temperature difference and wall temperature decrease by 10% or more, the latent heat release can be considered complete, and the rotation of the inner tube can be stopped to avoid the risk of jamming. Throughout the entire heat storage and release process, the end sealing device continues to operate.

[0111] The heating device maintains the temperature of the sealed shell above 65°C to ensure that the phase change material 15 does not solidify in this area.

[0112] The silicone oil in the first sealing cavity 4 forms a liquid barrier. Even if the phase change material 15 melts and comes into contact with the silicone oil, the phase change material 15 will not penetrate deep into the sealing cavity due to incompatibility and density difference.

[0113] When the inner tube 2 rotates, the mechanical seal assembly achieves a rotary dynamic seal, resulting in extremely low leakage (typically at the level of drops / hour).

[0114] If there is a slight leak in the mechanical seal, the silicone oil will seep out without causing the phase change material 15 to leak.

[0115] In this invention, the shell 1 is filled with phase change material 15, and the inner tube 2 is coaxially disposed inside the shell 1 and initially contacts the phase change material 15. At the start of heat storage, a hot fluid is introduced into the inner tube 2. The solid phase change material 15 near the outer wall of the inner tube 2 melts first, forming a dynamically expanding annular gap 31 between the outer wall of the inner tube 2 and the inner wall of the surrounding solid phase change material. The rotation of the inner tube 2 within this annular gap generates Taylor vortices. The radial circulation of the Taylor vortices efficiently transfers heat to the solid-phase interface at the outer edge of the annular gap, accelerating solid-phase melting and causing the annular gap width to gradually expand outward. Through this synergistic effect, the heat transfer bottleneck caused by the low thermal conductivity of the phase change material is effectively overcome, while avoiding the problem of decreased heat storage capacity caused by adding fins or blades. This design offers advantages such as high heat transfer efficiency, simple structure, and reliable sealing.

[0116] The detailed descriptions listed above are merely specific illustrations of feasible embodiments of the present invention and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A novel tubular phase change energy storage unit with an inner tube rotating, characterized in that, Includes a housing (1), an inner tube (2), an end cap (3), a rotary drive mechanism, a rotary joint assembly, an end sealing device, a support device, and a control system; The shell (1) is provided with end caps (3) at both ends. The inner tube (2) is coaxially arranged inside the shell (1). The space between the inside of the shell (1) and the outer wall of the inner tube (2) is filled with phase change material (15). The outer wall of the inner tube (2) is initially in contact with the phase change material (15). The rotary drive mechanism is connected to the inner tube (2) via gears and is used to drive the inner tube (2) to rotate around its axis; the rotary joint assembly is disposed at at least one end of the inner tube (2) and is used to introduce hot fluid from the external stationary pipeline into the rotary joint. The hot fluid is discharged from the inner tube (2) of the rotating tube. The end sealing device is disposed at both ends of the housing (1) and is used to seal the phase change material (15) inside the housing (1) when the inner tube (2) is rotating and stationary. The support device is provided at both ends of the inner tube (2) and the lower end of the shell (1) to support the shell (1) and the inner tube (2) and maintain the coaxiality of the shell (1) and the inner tube (2); The control system is connected to the motor of the rotary drive mechanism and is used to control the start-up, stop and rotation speed of the inner tube (2).

2. The novel tubular phase change energy storage unit with inner tube rotation according to claim 1, characterized in that, The inner tube (2) is a smooth round tube with no additional fins or blades on its outer surface; The phase change material (15) is selected from materials with solid-liquid phase change characteristics within the heat storage temperature range. During heat storage, the phase change material melts from solid to liquid; during heat release, it solidifies from liquid to solid.

3. The novel tubular phase change energy storage unit with inner tube rotation according to claim 1, characterized in that, The end sealing device includes a sealing housing, a first sealing cavity (4) and a second sealing cavity (5) disposed within the sealing housing, and an isolation ring disposed between the first sealing cavity (4) and the second sealing cavity (5); The first sealing cavity (4) is filled with an isolation fluid; the second sealing cavity (5) is provided with a sealing assembly; a heating device is provided on the outside of the sealing housing; the sealing assembly is a replaceable structure, and the sealing housing and the end cap (3) are connected by a flange; The isolation fluid is heat-conducting oil or silicone oil; the heating device is an electric heating tape or a heating jacket; the sealing assembly is a mechanical seal assembly or a packing seal assembly.

4. The novel tubular phase change energy storage unit with inner tube rotation according to claim 1, characterized in that, The support device includes two pairs of fixed-end supports; the fixed-end supports include paired angular contact ball bearings (13).

5. The novel tubular phase change energy storage unit with inner tube rotation according to claim 1, characterized in that, The rotary drive mechanism includes a motor, a drive gear (9), and a driven gear (8). The driven gear (8) is mounted on one end of the inner tube (2) via a keyway (14); the motor is a variable frequency motor and is electrically connected to the control system.

6. The novel tubular phase change energy storage unit with inner tube rotation according to claim 1, characterized in that, The control system includes a controller and a temperature sensor; The temperature sensor is located on the outer wall of the housing (1) and / or the outlet end of the inner tube (2) to detect the temperature state of the phase change material (15) and transmit it to the controller; The controller determines the formation and expansion process of the dynamically expanding annular gap (31) based on the temperature sensor signal and controls the rotational speed of the inner tube (2).

7. A phase change thermal energy storage method for a novel tubular phase change energy storage unit with inner tube rotation according to any one of claims 1-6, characterized in that, Includes the following steps: Initial state: The shell (1) is filled with phase change material (15), and the outer wall of the inner tube (2) is in contact with the phase change material (15). touch; Start-up of thermal storage: The hot fluid is introduced into the inner tube (2), and the phase change material (15) near the outer wall of the inner tube (2) absorbs heat and begins to melt, forming a dynamic expanding annular gap (31) between the outer wall of the inner tube (2) and the outer phase change material (15). Initiating rotation: The control system initiates the rotation drive mechanism to drive the inner tube (2) to rotate, thereby stimulating Taylor vortices in the liquid phase change material within the dynamically expanding annular gap (31) to form a Taylor vortex generation region (32). Taylor vortex enhanced heat transfer: The radial circulation of Taylor vortex efficiently transfers the heat from the outer wall of the inner tube (2) to the solid interface at the outer edge of the dynamically expanding annular gap (31), accelerating the melting of the solid phase and causing the width of the dynamically expanding annular gap (31) to gradually expand outward. Continuous heat storage: As the solid-phase interface continues to move outward, the width of the dynamically expanding annular gap (31) gradually increases. The control system adjusts the rotation speed of the inner tube (2) according to the temperature feedback to maintain the full development of the Taylor vortex. Heat release stage: Stop the flow of hot or cold fluid, keep the inner tube (2) rotating, and Taylor vortex delays the growth of solidified layer on the outer wall of the inner tube (2); when the latent heat release is determined to be complete, stop the rotation of the inner tube (2).

8. The phase change thermal energy storage method for the novel tubular phase change energy storage unit with inner tube rotation according to claim 7, characterized in that, During the rotation initiation step, the timing of the rotation initiation of the inner tube (2) is any one of the following: When the temperature sensor detects that the rate of increase of the water temperature at the outlet of the inner pipe has slowed down and the temperature of the outer wall of the shell (1) has started to rise, it is determined that the dynamic expansion annular gap (31) has been initially formed and the rotation is started; wherein, the slowing down means that the rate of increase of the outlet water temperature has decreased to below 0.05~0.1℃ / s and lasts for 10~30 seconds, and the starting to rise means that the rate of increase of the outer pipe wall temperature has reached above 0.02~0.05℃ / s and lasts for 10~20 seconds; Monitor the temperature of the outer wall of the inner tube (2). When the temperature rise rate of the outer wall of the inner tube (2) is below 0.1℃ / s for 30 consecutive seconds, and the temperature of the outer wall of the inner tube (2) exceeds the melting point of the phase change material by 3~5℃, start the rotation. Alternatively, preset a basic melting time. After the time is reached, jog the rotation at a speed of 10~20rpm and monitor the motor current. If the current does not exceed 130% of the rated value, continue the rotation. If it does, stop heating and try again.

9. The phase change thermal energy storage method for a novel tubular phase change energy storage unit with rotating inner tube as described in claim 7, characterized in that, During the continuous heat storage step, the control system adjusts the rotational speed of the inner tube (2) according to the estimated width of the dynamic expansion annular gap (31). When the radius of the dynamic expansion annular gap (31) is less than 1 / 3 of the difference between the radii of the shell (1) and the inner tube (2), the rotational speed is maintained at 80~100 rpm. When the radius of the dynamic expansion annular gap (31) is between 1 / 3 and 2 / 3 of the difference between the radii of the shell (1) and the inner tube (2), the rotational speed is increased to 120~150 rpm. When the radius of the dynamic expansion annular gap (31) is greater than 2 / 3 of the difference between the radii of the shell (1) and the inner tube (2), the rotational speed is increased to 150~200 rpm.

10. The phase change thermal energy storage method of the novel tubular phase change energy storage unit with inner tube rotation according to claim 7, characterized in that, In the heat release stage, the method to determine the completion of latent heat release is as follows: monitor the temperature rise rate of the cold fluid at the outlet of the inner tube (2) and / or the outer wall temperature of the shell (1). When the outer wall temperature is reduced by 10% or more compared with the temperature when melting is completed, or when the temperature rise rate of the cold fluid at the outlet of the inner tube (2) is lower than 0.02℃ / s for 2 minutes, the latent heat release is determined to be complete, and the rotation of the inner tube (2) is stopped.

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