Medium temperature direct absorption magnetic carbon fiber array assisted heat collection device

Abstract

This invention discloses a medium-temperature direct absorption magnetic carbon fiber array-assisted heat collection device, comprising a heat collection tube, a magnetic carbon fiber array assembly, an automatic light-tracking assembly, a transmission assembly, and a phase change tube assembly. Multiple sets of the magnetic carbon fiber array assembly are arranged inside the heat collection tube, and are arrayed along the axial direction of the heat collection tube on the phase change tube assembly. The automatic light-tracking assembly is located below the heat collection tube, and the heat collection tube is detachably connected to the automatic light-tracking assembly. The transmission assembly is located at one end of the heat collection tube and connected to the automatic light-tracking assembly. The phase change tube assembly is located inside the heat collection tube and connected to the transmission assembly. This invention significantly simplifies the manufacturing process by eliminating the vacuum coating and metal shell structure of traditional heat collection tubes, resulting in lower costs compared to conventional heat transfer oil vacuum heat collection tubes. It also avoids common faults such as high-temperature aging of the coating layer and vacuum failure at the metal-glass seal, eliminating complex coating and shell processing steps and effectively extending the device's service life.

Description

Technical Field

[0001] This invention relates to the field of solar thermal utilization technology, specifically to a medium-temperature direct absorption magnetic carbon fiber array-assisted heat collection device. Background Technology

[0002] In the field of medium-temperature solar thermal utilization (120℃-200℃), the current mainstream technology is high borosilicate glass metal-sealed heat transfer oil vacuum collector tube. This type of device relies on external vacuum coating and metal structure to absorb solar heat. The heat transfer oil inside the device is only used as a simple heat transfer medium, and its own light absorption efficiency is low.

[0003] Traditional solar collectors rely on vacuum coating technology to achieve a relatively high surface absorption rate of 92%-96%, providing basic medium-temperature heat collection capabilities. However, the cost of the vacuum coating layer and the metal casing is relatively high, accounting for approximately 70% of the total cost, thus significantly increasing production costs. Furthermore, existing coating layers are prone to aging under long-term operation in medium-temperature environments, leading to a decrease in absorption efficiency. In addition, the metal-glass seal is a weak point in the device; inadequate process control can easily cause vacuum layer failure, significantly reducing heat collection efficiency. The thermal conductivity of the metal also results in additional surface heat loss, further affecting heat collection performance. Moreover, these collectors rely solely on surface heat absorption, resulting in slow internal heat transfer and diffusion. Continuous operation over a wide temperature range can easily lead to localized overheating, and improper long-term management may accelerate equipment wear and tear, even posing potential safety hazards.

[0004] To address the shortcomings of traditional solar collector tubes, the industry is gradually developing and optimizing direct absorption solar collector tubes without coatings or metal shells. These tubes use a photothermal conversion fluid to directly absorb heat, eliminating the need for coating and shell processes. This simplifies the structure and reduces heat transfer losses, becoming a core trend for cost control in the medium-temperature solar thermal field. However, most current direct absorption structures suffer from low collection efficiency and uneven heat distribution, failing to fully meet the demands for efficient and stable heat collection. Therefore, developing a low-cost, efficient, and uniformly distributed direct absorption medium-temperature solar collector is of significant practical importance for promoting the large-scale implementation of medium-temperature solar thermal technology. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art, such as the high manufacturing cost and uneven heat distribution inside the tube in the 120℃-200℃ medium-temperature solar thermal collector.

[0006] A medium-temperature direct absorption magnetic carbon fiber array-assisted heat collection device is proposed, comprising a heat collection tube, a magnetic carbon fiber array assembly, an automatic light tracking assembly, a transmission assembly, and a phase change tube assembly. Multiple sets of the magnetic carbon fiber array assembly are arranged inside the heat collection tube, and these assemblies are arrayed along the axial direction of the heat collection tube on the phase change tube assembly. The automatic light tracking assembly is located below the heat collection tube, and the heat collection tube is detachably connected to the automatic light tracking assembly. The transmission assembly is located at one end of the heat collection tube and connected to the automatic light tracking assembly. The phase change tube assembly is located inside the heat collection tube and connected to the transmission assembly.

[0007] In a preferred embodiment of the present invention, the heat collection tube is made of high borosilicate transparent glass without vacuum coating or metal shell, and the heat collection tube is filled with heat transfer oil. The heat transfer oil used is preferably synthetic alkylbenzene heat transfer oil. Synthetic alkylbenzene heat transfer oil can still maintain stable operation under high temperature conditions of 200℃ without cracking and coking problems, thus taking into account both low cost and long-term durability.

[0008] In a preferred embodiment of the present invention, both ends of the heat collection tube are connected to metal discs. An oil inlet is provided on the metal disc at one end of the heat collection tube, and a plug is provided at the oil inlet. A transmission component is provided on the metal disc at the other end of the heat collection tube. The plug is connected to the heat collection tube by threads. The structure is simple and has good sealing performance.

[0009] In a preferred embodiment of the present invention, the transmission assembly includes a bracket, a motor, a dynamic sealing assembly, and a protective cover. The bracket is connected to the heat collection tube, the motor is located on one side of the bracket and connected to the bracket, the dynamic sealing assembly is disposed inside the bracket and connected to the heat collection tube, and the dynamic sealing assembly is connected to the motor and the phase change tube assembly. After the transmission assembly is started, it can drive the phase change tube assembly to rotate, thereby driving the magnetic carbon fiber array assembly to rotate synchronously through the phase change tube assembly, thereby adjusting the angle of the magnetic carbon fiber array assembly.

[0010] In a preferred embodiment of the present invention, the phase change tube assembly includes a crankshaft, a heat-conducting seat, a support base, a heat-conducting pipe, and a U-shaped tube. The crankshaft is disposed inside the heat-collecting tube, and the center line of the main journal of the crankshaft coincides with the axis of the heat-collecting tube. Multiple heat-conducting seats are provided on the crankshaft, and the heat-conducting seats are arranged in accordance with the axial direction of the heat-collecting tube. Each heat-conducting seat is provided with a support base, and the support base is connected to the heat-conducting seat through the heat-conducting pipe. Each heat-conducting seat is also provided with a U-shaped tube inside. The heat-conducting seats are made of a material with a high thermal conductivity. Therefore, after the heat is conducted to the heat-conducting seat, it can be transferred to the U-shaped tube through the heat-conducting seat, thereby heating the phase change working fluid inside the U-shaped tube.

[0011] In a preferred embodiment of the present invention, each U-tube contains a phase change working fluid, preferably mannitol. When the U-tube is heated, the mannitol phase change working fluid inside the U-tube rapidly absorbs heat and vaporizes. Under the action of internal pressure difference, the vaporized working fluid rapidly diffuses to the lower temperature region. After reaching the low temperature region, it releases heat and re-liquefies. Through repeated cycles of "heat absorption and vaporization - diffusion and heat release - liquefaction and reflux", the heat inside the tube is rapidly and uniformly transferred.

[0012] In a preferred embodiment of the present invention, the magnetic carbon fiber array assembly includes a magnet, a gasket, a retaining ring, a bracket, and magnetic carbon fibers. The magnet is disposed inside the support base, the gasket is located in the middle of the magnet and the support base, the top of the heat-conducting pipe contacts the gasket, the retaining ring is connected to the top of the support base and sleeved on the outside of the magnet, and three brackets are also provided on the outside of the magnet. All three brackets are connected to the retaining ring, and the included angle between adjacent brackets is the same. There are multiple bundles of magnetic carbon fibers. The magnetic carbon fibers preferentially adsorb onto the surface of the magnet, and the remaining unadsorbed magnetic carbon fibers are dispersed in the heat-conducting oil inside the heat-collecting pipe. The magnet generates a stable magnetic field, driving the magnetic carbon fibers to align regularly along the direction of the magnetic field lines. Combined with the magnetic pole repulsion between the magnetic carbon fibers, the magnetic carbon fibers self-assemble inside the synthetic alkylbenzene heat-conducting oil to form a "hedgehog-shaped" radial array structure. This special array structure allows incident sunlight to undergo multiple reflections and scatterings inside the pipe, greatly reducing light escape and significantly improving heat collection efficiency.

[0013] In a preferred embodiment of the present invention, the heat collection tube is further provided with connecting blocks at both ends. The heat collection tube is connected to the automatic light tracking component through the connecting blocks, and the connecting blocks are connected to the automatic light tracking component through bolts. Therefore, the heat collection tube can be quickly removed from the automatic light tracking component when needed, thereby replacing the heat collection tube.

[0014] In a preferred embodiment of the present invention, the automatic light-tracking component includes a fixed base, a microcontroller, a battery, and a signal receiver. The fixed base is located below the heat collection tube, the microcontroller is located inside the fixed base, and the microcontroller and battery are connected together. The signal receiver is located on one side of the microcontroller and is electrically connected to both the microcontroller and battery. The microcontroller can preset multiple trigger commands for different time periods according to usage requirements. Therefore, during use, it can output turning signals at fixed time nodes to accurately match the corresponding calibration angle, ensuring stable and reliable operation.

[0015] The beneficial effects of this invention compared to the prior art are: This invention adopts the above-mentioned technical solution, which is specifically adapted to medium-temperature conditions of 120℃-200℃. By eliminating the vacuum coating and metal shell structure of traditional heat collection tubes, the production and preparation process is greatly simplified. Compared with conventional heat transfer oil vacuum heat collection tubes, the overall manufacturing cost is reduced by more than 55%. At the same time, it avoids common faults such as high-temperature aging of the coating layer and vacuum failure at the metal-glass seal. It eliminates the complex coating and shell processing steps, effectively extending the service life of the device. The synthetic alkylbenzene heat transfer oil filled inside can still maintain stable operation under high-temperature conditions of 200℃ without cracking and coking problems, thus balancing low cost and long-term durability.

[0016] Driven by the magnetic field of a magnet, magnetic carbon fibers self-assemble to form a "hedgehog-shaped" light-harvesting structure. The spacing between the fiber tips matches the main energy band of the solar spectrum. Combined with a timed and angled automatic light-tracking system, this achieves a comprehensive improvement in solar thermal efficiency. The magnetic carbon fibers preferentially adsorb onto the surface of the magnet, while the remaining unadsorbed fibers are dispersed in the heat-conducting oil. This breaks the traditional surface heat absorption mode and achieves full-range absorption of sunlight, making it difficult for incident light to escape after multiple reflections and scatterings. This effectively compensates for the shortcomings of existing direct absorption structures, such as disordered distribution of light-absorbing fillers and high light scattering loss. With the light-tracking system relying on local historical meteorological data of solar activity, it achieves precise turning at fixed times and angles, and adjusts the orientation of the light-absorbing structure at regular intervals to maximize the reception of solar radiation, further improving the full-band absorption rate and heat collection efficiency of sunlight.

[0017] By embedding a U-shaped stainless steel phase change tube assembly inside the collector tube, and utilizing the rapid gas-liquid phase change cycle of mannitol working fluid and its synergistic temperature control with the heat transfer oil, high-speed and uniform heat diffusion within the tube is achieved. This solves the core problem of uneven heating in traditional devices. The mannitol working fluid stably completes the heat absorption and vaporization, heat diffusion and release, and liquefaction and reflux cycle within a wide temperature range of 120-200℃. It can also smooth out solar radiation fluctuations, and the heat diffusion efficiency is significantly improved compared to traditional collector tube structures. This fundamentally avoids the technical problem of local overheating and eliminates safety hazards such as damage and explosion caused by uneven heating of the collector tube, significantly improving the operational safety factor. It combines the dual advantages of high-efficiency heat collection and stable safety. At the same time, the overall structure is compact and integrated, eliminating the need for traditional high-cost coating and metal shells, making it highly adaptable and requiring no major modifications to existing supporting equipment. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a medium-temperature direct absorption magnetic carbon fiber array-assisted heat collection device. Figure 2 This is a schematic diagram of the internal structure of the solar collector tube (the solar collector tube is a whole, with one part removed to show the internal structure); Figure 3 This is a schematic diagram of the heat collection tube structure; Figure 4This is a schematic diagram of the oil inlet and plug structure of the heat collector tube; Figure 5 This is a schematic diagram of the transmission assembly structure; Figure 6 This is a schematic diagram of the phase change tube assembly (the heat collector tube is a whole, with one piece removed to show the internal structure). Figure 7 for Figure 6 A schematic diagram of the structure at point A; Figure 8 This is a schematic diagram of the internal structure of a U-shaped tube (the U-shaped tube is a whole, with a piece removed to show the internal structure). Figure 9 This is a schematic diagram of the magnetic carbon fiber array component structure; Figure 10 This is a schematic diagram of the exploded structure of a magnetic carbon fiber array assembly. Figure 11 This is a schematic diagram of the exploded structure of a phase change tube assembly; Figure 12 This is a schematic diagram of a magnetic carbon fiber adsorption magnet structure. Figure 13 This is a schematic diagram of the magnetic field distribution structure of a magnet. Figure 14 This is a schematic diagram of the automatic tracking light assembly (the mounting base is a single unit; one piece has been removed to show the internal structure). In the diagram: 1-Heat collector tube, 11-Oil inlet, 12-Plug, 13-Connecting block, 2-Magnetic carbon fiber array assembly, 21-Magnet, 22-Gasket, 23-Snap ring, 24-Bracket, 25-Magnetic carbon fiber, 3-Automatic tracking light assembly, 31-Fixed base, 32-Microcontroller, 33-Battery, 34-Signal receiver, 4-Transmission assembly, 41-Bracket, 42-Motor, 43-Dynamic sealing assembly, 44-Protective cover, 5-Phase change tube assembly, 51-Crankshaft, 52-Heat conduction base, 53-Support base, 54-Heat conduction tube, 55-U-tube. Detailed Implementation

[0019] The following will refer to the appendices in the embodiments of the present invention. Figures 1-14 The technical solutions in the embodiments of the present invention will be described in detail below.

[0020] like Figures 1-2 As shown, a medium-temperature direct absorption magnetic carbon fiber array-assisted heat collection device includes a heat collection tube 1, a magnetic carbon fiber array assembly 2, an automatic light tracking assembly 3, a transmission assembly 4, and a phase change tube assembly 5. There are multiple sets of magnetic carbon fiber array assemblies 2, all of which are arranged inside the heat collection tube 1. The magnetic carbon fiber array assemblies 2 are arranged in an array along the axial direction of the heat conduction tube 54. Each set of magnetic carbon fiber array assemblies 2 is connected to the phase change tube assembly 5. Therefore, when the phase change tube assembly 5 rotates...

[0021] like Figures 1-2 As shown, the phase change tube assembly 5 can synchronously drive all magnetic carbon fiber array assemblies 2 to rotate. The automatic light tracking assembly 3 is located below the heat collection tube 1, and the heat collection tube 1 can be detachably connected to the automatic light tracking assembly 3. Therefore, the heat collection tube 1 can be replaced as needed. The transmission assembly 4 is located at one end of the heat collection tube 1 and connected to the heat collection tube 1. The transmission assembly 4 is connected to the automatic light tracking assembly 3.

[0022] like Figures 1-2 As shown, the automatic light tracking component 3 can start the transmission component 4 according to the preset command, so that the transmission component 4 drives the phase change tube component 5 to rotate. The phase change tube component 5 is located inside the heat collection tube 1, and one end of the phase change tube component 5 is connected to the transmission device. Therefore, after the transmission device is turned on, it can drive the phase change tube component 5 to rotate.

[0023] like Figures 3-4 As shown, the heat collection tube 1 used is preferably made of high borosilicate transparent glass without vacuum coating or metal shell, which is suitable for medium temperature conditions of 120-200℃. Therefore, after being exposed to sunlight, the light can pass through the transparent heat collection tube 1 and directly contact the magnetic carbon fiber 25 in the magnetic carbon fiber array component 2. Moreover, compared with the vacuum heat collection tube 1 in the traditional solution, this heat collection tube 1 is a single-layer glass tube structure, which eliminates the vacuum coating process and the matching structure of the metal shell, and greatly reduces the production and manufacturing cost from the source.

[0024] like Figures 3-4 As shown, the heat collector tube 1 is filled with synthetic alkylbenzene heat transfer oil as the heat transfer medium. The heat transfer oil has an applicable temperature range of -25 to 320℃, and has long-term thermal stability at 200℃. It does not crack or coke, and its service life can reach 5-10 years. The heat collector tube 1 is tubular and its diameter is about 70 mm. A metal disk (made of non-magnetic material) is provided at both ends of the heat collector tube 1. The ends of the heat collector tube 1 and the metal disk are sealed by a heating and melting process to ensure airtightness.

[0025] like Figures 3-4 As shown, the thermal expansion coefficient of the metal disc is close to that of high borosilicate transparent glass, thus avoiding excessive internal stress. One end of the heat collection tube 1 is provided with an oil inlet 2, and a plug cap 12 is provided at the oil inlet 2. The plug cap 12 is connected to the heat collection tube 1 by a thread. The threaded connection structure is simple and has good sealing performance. Both ends of the heat collection tube 1 are also provided with connecting blocks 13. The connecting blocks 13 and the metal disc are made by an integral molding process (such as casting).

[0026] like Figures 3-4As shown, the heat collection tube 1 is connected to the automatic light tracking component 3 via the connecting block 13. The connecting block 13 is connected to the automatic light tracking component 3 via bolts. Therefore, the heat collection tube 1 can be quickly removed from the automatic light tracking component 3 when needed, so as to replace the heat collection tube 1.

[0027] like Figure 5 As shown, the transmission assembly 4 includes a bracket 41, a motor 42, a dynamic sealing assembly 43, and a protective cover 44. The bracket 41 is located at one end of the heat-conducting pipe 54 and is positioned on the axis of the heat-collecting pipe 1. The bracket 41 is made of stainless steel and is bonded to the end face of the heat-collecting pipe 1. The motor 42 is located on one side of the bracket 41 and is fixed to the bracket 41 by bolts. The motor 42 is either a servo motor 42 or a stepper motor 42 equipped with a controller.

[0028] like Figure 5 As shown, the bracket 41 has a through hole at the position of the output shaft of the motor 42. Therefore, the output shaft of the motor 42 can pass through the through hole and connect to the dynamic sealing assembly 43 (the dynamic sealing assembly 43 is an existing device, such as the dynamic sealing device for bearing housing disclosed in Chinese Patent Publication No. CN205824184U, which is not described in detail here). The end cap of the dynamic sealing assembly 43 is connected to the metal disk at one end of the heat collection tube 1, and the end cap and the metal disk are sealed by a sealing gasket 22.

[0029] like Figure 5 As shown, the two ends of the shaft inside the dynamic sealing assembly 43 are connected to the output end of the motor 42 and the crankshaft 51 of the phase change tube assembly 5, respectively. Therefore, after the motor 42 starts, it can drive the crankshaft 51 of the phase change tube assembly 5 to rotate through the circumference of the dynamic sealing assembly 43, and the dynamic sealing assembly 43 can ensure that leakage does not occur when the crankshaft 51 rotates.

[0030] like Figure 5 As shown, the motor 42 is connected to the microcontroller 32 and the battery 33 of the automatic tracking component 3. Therefore, the motor 42 can be started and stopped by the microcontroller 32 during use. The protective cover 44 is placed on the motor 42, and the protective cover 44 has heat dissipation gaps. This not only prevents external rain and snow from corroding the motor 42, but also meets the heat dissipation requirements of the motor 42.

[0031] like Figures 6-8 As shown, the phase change tube assembly 5 includes a crankshaft 51, a heat-conducting seat 52, a support base 53, a heat-conducting pipe 54, and a U-shaped tube 55. The crankshaft 51 is located inside the heat-collecting pipe 1, and the center line of the main journal of the crankshaft 51 coincides with the axis of the heat-collecting pipe 1. Therefore, when the crankshaft 51 rotates, it can rotate with the axis of the heat-collecting pipe 1 as the center.

[0032] like Figures 6-8As shown, bearings are provided at both ends of the crankshaft 51. The outer ring of the bearing is mechanically fixed (such as by screws) to the side wall of the metal disc. The inner ring of the bearing is preferably fixed to the end of the crankshaft 51 by means of a shoulder and a shaft end baffle. The end of the crankshaft 51 located at the motor 42 is fixed to the shaft of the dynamic seal assembly 43 by means of a key connection after passing through the inner ring of the bearing. Therefore, the motor 42 can drive the crankshaft 51 to rotate after starting.

[0033] like Figures 6-8 As shown, the crankshaft 51 is provided with multiple heat conduction seats 52, which are arranged along the axial direction of the heat collection tube 1. Each heat conduction seat 52 has a metal clamp at its lower end (all clamps are existing products, so they will not be described in detail). The heat conduction seats 52 are connected to the crankshaft 51 through the metal clamps, so the heat conduction seats 52 can be driven to rotate synchronously when the crankshaft 51 rotates. The heat conduction seats 52 are made of high thermal conductivity materials (such as stainless steel or copper) to meet the requirements of high thermal conductivity.

[0034] like Figures 6-8 As shown, each heat-conducting seat 52 is provided with a hemispherical support base 53. The support base 53 is preferably made of non-magnetic steel to avoid disturbing the magnetic field of the magnet 21. Multiple heat-conducting pipes 54 are vertically arranged between the support base 53 and the heat-conducting seat 52. The heat-conducting pipes 54 are made of non-magnetic metal materials (such as silver or aluminum alloy) with high vertical thermal conductivity. The shape of the lower end of the heat-conducting pipe 54 corresponds to the shape of the outer surface of the heat-conducting seat 52, and the shape of the upper end of the heat-conducting pipe 54 corresponds to the shape of the contact surface between the gasket 22 and the support base 53.

[0035] like Figures 6-8 As shown, the support base 53 has a corresponding through hole at the position of the heat pipe 54. The middle section of the heat pipe 54 passes through the pre-set through hole of the support base 53. The support base 53 is connected to the outer wall of the heat pipe 54, thereby supporting the support base 53 through the heat pipe 54. Each heat pipe seat 52 also has a U-shaped tube 55 inside. The heat pipe seat 52 has a corresponding through hole at the position of the U-shaped tube 55. The U-shaped tube 55 is made of a material with non-magnetic properties and high thermal conductivity (such as stainless steel).

[0036] like Figures 6-8 As shown, the fit between the heat-conducting seat 52 and the U-shaped tube 55 is an interference fit. The friction between the heat-conducting seat 52 and the U-shaped tube 55 ensures that the U-shaped tube 55 will not be displaced during use. The inner wall of the through hole of the heat-conducting seat 52 is in contact with the outer wall of the U-shaped tube 55. Therefore, after the heat-conducting tube 54 transfers heat to the heat-conducting seat 52, it can then transfer heat to the U-shaped tube 55 through the heat-conducting seat 52.

[0037] like Figures 6-8As shown, the U-shaped tube 55 has a cavity inside, which is filled with mannitol phase change working fluid with a phase change temperature of 165℃. The outer wall of the U-shaped tube 55 is in direct contact with the heat transfer oil inside the tube. The mannitol phase change temperature is located in the middle of the working range of 120-200℃, and it has good chemical compatibility with the stainless steel tube body. Mannitol can undergo a rapid vaporization reaction within the working temperature range of 120-200℃ to form a stable gas-liquid phase change cycle.

[0038] like Figures 6-8 As shown, when mannitol is not heated, its physical state is liquid. When liquid mannitol is inside the U-shaped tube 55, it will be at the lowest point of the U-shaped tube 55 (i.e., the contact position between the U-shaped tube 55 and the heat-conducting seat 52) ​​under its own gravity. Then, when the local area inside the heat-collecting tube 1 is heated or the heat-conducting seat 52 transfers the temperature to the U-shaped tube 55, the temperature of the area on the U-shaped tube 55 corresponding to the position of the heat-conducting seat 52 will rise. At this time, the mannitol phase change working fluid in the corresponding position of the U-shaped tube 55 will rapidly absorb heat and vaporize.

[0039] like Figures 6-8 As shown, the vaporized working fluid diffuses rapidly to the lower temperature region under the action of internal pressure difference. After reaching the low temperature region, it releases heat and re-liquefies. Through repeated cycles of "heat absorption and vaporization - diffusion and heat release - liquefaction and reflux", the heat inside the tube is transferred rapidly and evenly. During this process, mannitol will be at the high position of U-tube 55 when it diffuses and releases heat. At this time, the heat emitted by mannitol will be transferred to the heat transfer oil located at the high position of U-tube 55.

[0040] like Figures 6-8 As shown, the U-shaped tube 55 and the heat transfer oil work together. When the temperature of the heat transfer oil rises above 165°C, the mannitol melts and absorbs excess heat, inhibiting the temperature from rising too quickly. When the temperature of the heat transfer oil drops below 165°C, the mannitol solidifies and releases heat, slowing down the temperature drop and effectively suppressing solar radiation fluctuations, thus avoiding local overheating. The length of the U-shaped tube 55 from its lowest point to its highest point is 40-60 mm, and the diameter of the U-shaped tube 55 is 8-10 mm. Both the lowest and highest points of the U-shaped tube 55 are left with a margin from the inner wall of the heat collector tube 1 to prevent the U-shaped tube 55 from contacting the inner wall of the heat collector tube 1 when it rotates.

[0041] like Figures 9-13As shown, the magnetic carbon fiber array assembly 2 includes a magnet 21, a gasket 22, a retaining ring 23, a bracket 24, and magnetic carbon fibers 25. The magnet 21 is spherical, and each support base 53 has a spherical magnet 21 inside. There is a sufficient gap between adjacent magnets 21 (the gap is about 2-3 times the diameter of the magnet 21) to reduce the intensity of magnetic field interference between adjacent magnets 21. When the magnets 21 are arrayed in the axial direction of the heat collection tube 1, the magnetic poles of the magnets 21 are arranged alternately according to the "NSNS" setting method to avoid magnetic field repulsion between adjacent magnets 21.

[0042] like Figures 9-13 As shown, the magnets 21 used are neodymium iron boron magnets 21. Each magnet 21 has a hemispherical pad 22 below it. The pad 22 is located in the middle between the magnet 21 and the support base 53. The pad 22 is made of a non-magnetic or weakly magnetic material with a high thermal conductivity (such as graphite or copper) to avoid disturbing the magnetic field of the magnet 21 during use. The inner surface of the pad 22 is in contact with the magnet 21, and the outer surface of the pad 22 is in contact with the top of the heat pipe 54.

[0043] like Figures 9-13 As shown, the heat on the surface of the magnet 21 can be transferred to the heat pipe 54 through the gasket 22. The rotation center line of the magnet 21 coincides with the axis of the heat collection pipe 1. The retaining ring 23 is located at the top of the support base 53 and is sleeved on the outside of the magnet 21. The retaining ring 23 is threaded into the groove of the support base 53. Three brackets 24 are also provided above the retaining ring 23. The cross section of the bracket 24 is "L" shaped. The lower end of the bracket 24 is bonded to the retaining ring 23. The angle between adjacent brackets 24 is 120 degrees.

[0044] like Figures 9-13 As shown, the bracket 24 gently supports the magnet 21 from the side, thereby restricting the horizontal movement of the magnet 21. However, the bracket 24 does not apply a downward pressing force to the magnet 21. There are multiple bundles of magnetic carbon fibers 25, all of which are arranged inside the heat collection tube 1. The magnetic carbon fibers 25 are magnetic themselves. Therefore, after the magnetic carbon fibers 25 enter the magnetic field range of the magnet 21, the magnetic carbon fibers 25 close to the magnet 21 will preferentially be attracted to the magnet 21 by their own magnetism. The magnetic carbon fibers 25 located inside the magnetic field of the magnet 21 will be arranged according to the shape of the magnetic field lines of the magnet 21. The magnetic carbon fibers 25 located outside the magnetic field of the magnet 21 or in a slightly weaker magnetic field will be distributed in the heat transfer oil.

[0045] like Figures 9-13As shown, since the heat collection tube 1 is filled with heat-conducting oil, the magnetic carbon fiber 25 will be distributed in the heat-conducting oil. The magnet 21 generates a stable magnetic field, which drives the magnetic carbon fiber 25 to be arranged in a regular manner along the direction of the magnetic field lines. Combined with the magnetic pole repulsion between the magnetic carbon fibers 25, the magnetic carbon fiber 25 self-assembles in the heat-conducting oil to form a "hedgehog-shaped" radial array structure.

[0046] like Figures 9-13 As shown, the magnetic carbon fiber 25 used is a porous Fe3C / ZnFe@C composite microstructure derived from ZnO. Fe3O4 nanospheres were synthesized by hydrothermal method, and then mixed with commercial ZnO nanoparticles and polyacrylonitrile (PAN) in DMF to form a spinning solution. Fe3O4 / ZnO / PAN composite fibers were prepared by electrospinning, and then pre-oxidized at 250℃ for 2 hours and carbonized at 700-800℃ in a nitrogen atmosphere to obtain the final product. (The method of preparing the magnetic carbon fiber 25 is an existing method. The preparation scheme of the magnetic carbon fiber 25 is disclosed in the paper "Preparation and Electromagnetic Properties Study of Lightweight Magnetic Carbon Fiber 25" published by Huazhong University of Science and Technology, so it will not be described in detail.)

[0047] like Figures 9-13 As shown, the magnetic carbon fiber 25 can maintain good magnetic responsiveness and dispersion stability under medium-temperature conditions of 120-200℃. The single filament diameter is 300-500nm and the length is 30-50μm. The initial dispersion concentration in the heat transfer oil is 0.8-1.5mg / mL. Under the action of a magnetic field, the average spacing between the fiber tips is stable at 1.0-3.0μm. This spacing matches the main energy band of the solar spectrum (300-2500nm). Therefore, this special array structure can cause the incident sunlight to undergo multiple reflections and scatterings inside the tube, greatly reducing light escape and significantly improving the heat collection efficiency, transforming the traditional surface absorption heat collection method into internal overall absorption.

[0048] like Figures 9-13 As shown, after the magnetic carbon fiber 25 adsorbed on the magnet 21 is exposed to sunlight, the sunlight will be refracted multiple times between adjacent magnetic carbon fibers 25. Then the magnetic carbon fiber 25 can transfer the heat of the sunlight to the magnet 21. Then the pad 22 will conduct the heat on the magnet 21 to the heat pipe 54 and the heat seat 52, and finally transfer it to the phase change working fluid in the U-shaped tube 55 through the heat seat 52.

[0049] like Figure 14 As shown, the automatic light tracking component 3 includes a mounting base 31, a microcontroller 32, a battery 33, and a signal receiver 34. The mounting base 31 is located above the heat collection tube 1. The mounting base 31 can be fixed to the ground or metal bracket 41 by mechanical fixing (such as bolts or riveting). The microcontroller 32 is located inside the mounting base 31 and is connected to the mounting base 31 by mechanical fixing.

[0050] like Figure 14 As shown, the microcontroller 32 is connected to the motor 42. Therefore, the microcontroller 32 can cooperate with the controller built into the motor 42 to start and stop the motor 42 at timed intervals according to the built-in control instructions. The battery 33 is located on one side of the microcontroller 32 and is electrically connected to the microcontroller 32 and the motor 42 to provide power support for the microcontroller 32 and the motor 42. The signal receiver 34 is located on one side of the microcontroller 32 and is electrically connected to the microcontroller 32 and the battery 33.

[0051] like Figure 14 As shown, the signal receiver 34 is mechanically fixed on the mounting base 31, so the motor 42 can be remotely started and stopped by receiving the signal when needed. The battery 33 has a built-in charging controller (the battery 33 with a built-in charging controller is an existing product, such as the Greenjia 48V20AH solar-specific battery, so it will not be described in detail). Therefore, it can be used in conjunction with existing solar panel products.

[0052] The movement process in this embodiment is as follows: After the fixing seat 31 is fixed in the required position by mechanical fixation, the magnetic carbon fiber 25 in the heat transfer oil will be distributed in the heat transfer oil under the influence of the magnetic field. When exposed to sunlight, the light will be refracted multiple times when it shines on the magnetic carbon fiber 25 on the magnet 21. The heat in the light will be conducted to the magnet 21 through the magnetic carbon fiber 25. Then the magnet 21 can be transferred to the U-shaped tube 55 through the gasket 22, the heat transfer pipe 54, and the heat transfer seat 52. Finally, it will be transferred to the mannitol phase change working medium in the U-shaped tube 55 through the U-shaped tube 55. Then the mannitol phase change working medium will be heated and vaporized. After vaporization, the working medium will diffuse rapidly to the lower temperature area under the action of internal pressure difference. After reaching the low temperature area, it will release heat and re-liquefy. Through repeated cycles of "heat absorption and vaporization-diffusion and heat release-liquefaction and reflux", the heat in the tube is rapidly and evenly transferred. During this process, the heat emitted by the mannitol will be transferred to the heat transfer oil, thereby increasing the temperature of the heat transfer oil in the heat collection tube 1.

[0053] When in use, it can rely on local historical meteorological data of solar movement to achieve timed and angled rotation. For example, in a certain place, from 10 am to 3 pm, the angle between the sun and the ground (solar altitude angle) rises from about 45° to 60° and then falls back to 45°. During this period, the total angle of the sun's movement is 30°. Divide the angle between the sun's movement from 10 am to 3 pm (i.e., 30 degrees) into eight parts, set eight timed start commands in the microcontroller 32, so that the microcontroller 32 starts the motor 42 at a fixed time point. In this way, the motor 42 and the crankshaft 51 drive the magnet 21 and the U-shaped tube 55 to rotate to a fixed angle at each time point, ensuring that the carbon fiber on the U-shaped tube 55 and the magnet 21 is always in the optimal angle of sunlight, thus adapting to the long-term normal operation requirements of medium-temperature heat collection.

[0054] To verify the heat collection efficiency and operational stability of the device of the present invention, a comparative experiment was set up. Pure synthetic alkylbenzene heat transfer oil (without coating transparent tube), heat transfer oil system with magnetic carbon fiber 25 array, heat transfer oil system with magnetic carbon fiber 25 array plus U-shaped phase change tube, and the complete device of the present invention with magnetic carbon fiber 25 array plus U-shaped phase change tube plus micro automatic light tracking system were placed on the same solar thermal test platform. The test environment was outdoor sunny weather with solar radiation intensity ≥800W / ㎡. The saturation experiment lasted for 120 minutes, and the temperature changes at different stages were recorded. All samples were repeated 3 times, and the test results were averaged.

[0055]

[0056] As can be seen from Table 1, the pure synthetic alkylbenzene heat transfer oil has a poor effect on direct heat absorption and collection in the uncoated transparent tube, with the temperature only rising to 65.8℃ in 120 minutes. The heat collection efficiency is significantly increased after adding the magnetic carbon fiber 25 array. After further adding the U-shaped phase change tube assembly 5 and the micro automatic tracking system, the temperature uniformity inside the tube is greatly improved, and the heat collection efficiency is further improved.

[0057] The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

[0058] The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solutions based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A medium-temperature direct absorption magnetic carbon fiber array-assisted heat collection device, characterized in that: The device includes a heat collection tube (1), a magnetic carbon fiber array assembly (2), an automatic light tracking assembly (3), a transmission assembly (4), and a phase change tube assembly (5). The magnetic carbon fiber array assembly (2) consists of multiple sets, all of which are located inside the heat collection tube (1). The magnetic carbon fiber array assembly (2) is arranged in an array on the phase change tube assembly (5) along the axial direction of the heat collection tube (1). The automatic light tracking assembly (3) is located below the heat collection tube (1). The heat collection tube (1) is detachably connected to the automatic light tracking assembly (3). The transmission assembly (4) is located at one end of the heat collection tube (1) and connected to the automatic light tracking assembly (3). The phase change tube assembly (5) is located inside the heat collection tube (1) and connected to the transmission device.

2. The medium-temperature direct absorption magnetic carbon fiber array-assisted heat collection device according to claim 1, characterized in that: The heat collection tube (1) is made of high borosilicate transparent glass without vacuum coating or metal shell, and the heat collection tube (1) is filled with heat-conducting oil.

3. The medium-temperature direct absorption magnetic carbon fiber array-assisted heat collection device according to claim 2, characterized in that: Both ends of the heat collection tube (1) are connected to metal discs. An oil inlet (11) is provided on the metal disc at one end of the heat collection tube, and a plug (12) is provided at the oil inlet (11). A transmission assembly (4) is provided on the metal disc at the other end of the heat collection tube (1).

4. The medium-temperature direct absorption magnetic carbon fiber array-assisted heat collection device according to claim 3, characterized in that: The transmission assembly (4) includes a bracket (41), a motor (42), a dynamic sealing assembly (43), and a protective cover (44). The bracket (41) is connected to the heat collection tube (1). The motor (42) is located on one side of the bracket (41) and connected to the bracket (41). The dynamic sealing assembly (43) is located inside the bracket (41) and connected to the heat collection tube (1). The dynamic sealing assembly (43) is connected to the motor (42) and the phase change tube assembly (5).

5. The medium-temperature direct absorption magnetic carbon fiber array-assisted heat collection device according to claim 4, characterized in that: The phase change tube assembly (5) includes a crankshaft (51), a heat-conducting seat (52), a support base (53), a heat-conducting pipe (54), and a U-shaped tube (55). The crankshaft (51) is located inside the heat-collecting pipe (1), and the center line of the main journal of the crankshaft (51) coincides with the axis of the heat-collecting pipe (1). Multiple heat-conducting seats (52) are provided on the crankshaft (51). The heat-conducting seats (52) are arranged in accordance with the axial direction of the heat-collecting pipe (1). Each heat-conducting seat (52) is provided with a support base (53). The support base (53) is connected to the heat-conducting seat (52) through the heat-conducting pipe (54). Each heat-conducting seat (52) is also provided with a U-shaped tube (55) inside.

6. The medium-temperature direct absorption magnetic carbon fiber array-assisted heat collection device according to claim 5, characterized in that: Each U-tube (55) is equipped with a phase change working medium inside.

7. The medium-temperature direct absorption magnetic carbon fiber array-assisted heat collection device according to claim 5, characterized in that: The magnetic carbon fiber array assembly (2) includes a magnet (21), a gasket (22), a retaining ring (23), a bracket (24), and magnetic carbon fibers (25). The magnet (21) is located inside the support base (53). The gasket (22) is located in the middle between the magnet (21) and the support base (53). The top end of the heat-conducting pipe (54) is in contact with the gasket (22). The retaining ring (23) is connected to the top end of the support base (53) and sleeved on the outside of the magnet (21). Three brackets (24) are also provided on the outside of the magnet (21). All three brackets (24) are connected to the retaining ring (23). The included angle between the brackets (41) of adjacent brackets (24) is the same. There are multiple bundles of magnetic carbon fibers (25). The magnetic carbon fibers (25) are preferentially adsorbed on the surface of the magnet (21). The remaining unadsorbed magnetic carbon fibers (25) are dispersed in the heat-conducting oil inside the heat-collecting pipe (1).

8. The medium-temperature direct absorption magnetic carbon fiber array-assisted heat collection device according to claim 7, characterized in that: The heat collection tube (1) is also provided with connecting blocks (13) at both ends, and the heat collection tube (1) is connected to the automatic light tracking component (3) through the connecting blocks (13).

9. The medium-temperature direct absorption magnetic carbon fiber array-assisted heat collection device according to claim 8, characterized in that: The automatic light-tracking component (3) includes a mounting base (31), a microcontroller (32), a battery (33), and a signal receiver (34). The mounting base (31) is located below the heat collection tube (1). The microcontroller (32) is located inside the mounting base (31). The microcontroller (32) and the battery (33) are connected to the battery. The signal receiver (34) is located on one side of the microcontroller (32) and is electrically connected to the microcontroller (32) and the battery (33).

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