A fluid lattice magnetically controlled solar energy heat collection device

Abstract

The present invention discloses a fluid lattice type magnetically controlled enhanced absorption solar heat collection device, comprising a concentrator and a solar absorption unit installed above the concentrator, a permanent magnet is arranged at the bottom of the concentrator, the permanent magnet is arranged above a rotating disk, the rotating disk is connected to a controller for controlling the rotation of the rotating disk, and the controller and the rotating disk are both connected to a power supply; the solar absorption unit comprises a heat collection tube and a water storage tube and a glass vacuum inner tube which are sequentially embedded on the outside of the heat collection tube, the heat collection tube is provided with a transverse and longitudinal arc optical fiber inside, and the arc optical fiber is provided with an enhanced lattice absorption unit. The present invention overcomes the problems of poor high temperature resistance and durability of the absorption coating of the traditional solar collector, and the problems of slow heat absorption and long heat transfer time caused by uneven heat absorption of the existing direct absorption type collector, and further improves the heat collection, energy storage efficiency and heat transfer efficiency of the collector.

Description

Technical Field

[0001] The invention belongs to the field of solar energy thermal utilization, and in particular relates to a fluid lattice type magnetically controlled enhanced absorption solar energy heat collecting device. Background Art

[0002] As the most abundant energy among renewable energy sources, solar energy has become the focus of current scientific research. In particular, the study of solar thermal energy is a hot topic of research. Conventional medium-temperature heat collection methods mainly rely on the selective absorption coating on the vacuum-coated tube to absorb solar radiation and heat the internal working fluid, and transfer heat to the fluid in the tube by heat conduction and convection. This indirect absorption method has poor system stability, reliability and durability due to the difficulty in maintaining the heat resistance and vacuum degree of the selective absorption coating for a long time, and the large temperature difference causes the heat collection tube to burst easily, which has become the main obstacle to its application. In view of this, direct absorption collectors that directly absorb solar energy with nanofluids have attracted widespread attention. The heat transfer mechanism of nanofluid direct absorption solar collectors is to add nanoparticles with strong heat collection ability to the traditional heat collection fluid, so that the heat collection absorption working fluid itself has a strong solar absorption characteristic. The heat collection medium integrates the three characteristics of heat absorption, heat transfer and heat carrying. It is simple to manufacture and has low cost, which greatly improves the heat collection efficiency.

[0003] In recent years, with the development of magnetic fluids, researchers have found that although nanofluids can effectively improve the absorption of solar heat by directly absorbing solar collectors, changing the type, size, and shape of nanoparticles can further improve the absorption efficiency of solar heat. Magnetic nanofluids not only have the magnetism of solid substances, but also have the flow characteristics of liquids. Under the action of an external magnetic field, the magnetic particles in the magnetic nanofluids will aggregate in a small range, and the change in the shape of the aggregates will also enhance the heat transfer.

[0004] Patent CN110195938A discloses a magnetic field-assisted nanofluid direct absorption type concentrating magnetic fluid solar thermal collector, including a solar positioning tracking reflection device, a solar absorption device and a heat exchange steam generation device. The nanofluid is used to effectively improve the efficiency of photothermal absorption and heat transfer, and at the same time, an external magnetic field is used to form a nanomagnetic fluid hill-shaped structure in the nanofluid to supplement the absorption of solar energy. However, although the device has improved the solar energy absorption efficiency to a certain extent, it generally shows the heat absorption characteristics of fast temperature rise in the surrounding area and slow temperature rise in the middle, resulting in a long heat transfer time and low overall heat absorption efficiency. Summary of the invention

[0005] The purpose of the present invention is to solve the above technical problems and provide a fluid lattice type magnetically controlled enhanced absorption solar energy collector with improved solar energy collection efficiency and heat transfer efficiency, long equipment life and energy saving.

[0006] The present invention solves the technical problem by the following technical solutions:

[0007] A fluid lattice type magnetically controlled enhanced absorption solar energy heat collection device comprises a concentrator and a solar energy absorption unit installed above the concentrator, a permanent magnet is arranged at the bottom of the concentrator, the permanent magnet is arranged above a rotating disk, the rotating disk is connected to a controller for controlling the rotation of the rotating disk, the controller and the rotating disk are both connected to a power supply; the solar energy absorption unit comprises a heat collecting tube and a water storage tube and a glass vacuum inner tube which are sequentially embedded on the outside of the heat collecting tube, the heat collecting tube is provided with transverse and longitudinal arc optical fibers, and the arc optical fibers are provided with an enhanced lattice absorption unit.

[0008] The permanent magnet is embedded in the center of the rotating disk. When the rotating disk rotates, it can rotate with it. The purpose is that during its rotation, the direction of the magnetic field it generates also changes, which can control the synaptic direction of the enhanced lattice absorption unit on the optical fiber inside the heat collecting tube to change together, so that it receives the maximum intensity of light at the most appropriate angle, strengthening Figure 3 The light and heat absorption of the middle part can be improved, thereby improving the absorption efficiency of solar energy. Furthermore, the enhanced lattice absorption unit is a magnetic particle adsorbed with a magnetic high thermal conductivity composite material. The magnetic particle is a magnetic steel that has been mechanically crushed and ground by a ball mill to become a fine magnet, which is adhered to the optical fiber through epoxy glue. The composite material with magnetism, high absorption and high thermal conductivity can be adsorbed around the small magnet, and under the action of the magnet, a synapse is formed along the direction of the magnetic field, and the direction of the synapse changes with the rotation of the permanent magnet, which is used to capture and conduct solar light, such as Figure 4 As shown in Figure 1, when sunlight shines on these protruding structures, it is repeatedly absorbed and reflected until the sunlight is completely absorbed, so that these synapses can maximize the absorption and storage of solar heat at the most appropriate angle.

[0009] Furthermore, the magnetic high thermal conductivity composite material is a composite nanomaterial of ferroferric oxide modified carbon nanotubes.

[0010] Furthermore, the heat collecting tube contains an absorption medium, which is a mixed liquid in which Fe3O4-graphene composite functional nano magnetic fluid is added to a base liquid. The base liquid is heat transfer oil, water or ethylene glycol. Under the action of the dispersant, the nanoparticles can be evenly and stably distributed in the base liquid. Under the action of the permanent magnet, the evenly distributed nanoparticles begin to aggregate in a small range to form a chain-like heat channel, which can effectively improve the absorption efficiency of solar energy.

[0011] Furthermore, the water storage pipe, glass vacuum inner tube and heat collecting pipe are fixed on one side of the fixed baffle, and the other side of the fixed baffle is respectively provided with a water inlet and a water outlet connected to the water storage pipe, and connected to the absorption medium inlet and outlet of the heat collecting pipe.

[0012] Furthermore, the controller is connected to a photosensor, and the power source is a solar panel.

[0013] Furthermore, the concentrator includes a metal semi-arc light reflecting surface, and the surface of the reflecting surface is coated with a high reflectivity film. The sunlight around the heat collecting tube is focused by the reflecting surface and concentratedly reflected on the heat collecting tube and absorbed by the absorbing medium in the heat collecting tube. At the same time, some light that has not been absorbed by the absorbing medium and thus penetrates the vacuum inner tube can be reflected again by the focusing light reflecting surface-13, achieving the effect of secondary absorption, thereby improving the internal heat collecting tube (③ Figure 3 )Absorption by the part farthest from the sun.

[0014] Furthermore, the solar energy absorption unit is supported on the inner concave surface of the light reflecting surface through a bracket.

[0015] Furthermore, two ends of the light reflecting surface are fixed on a tripod.

[0016] The beneficial effects of the present invention are:

[0017] Compared with the prior art, the present invention proposes a fluid lattice magnetically controlled enhanced absorption solar thermal collector device, which overcomes the problems of poor high temperature resistance and durability of the absorption coating of traditional solar thermal collectors, as well as uneven heat absorption of existing direct absorption type collectors, resulting in slow heat absorption and long heat transfer time. By optimizing the structure and materials of the device, it is possible to solve the limitations of slow heat absorption of the absorption working fluid or slow heating speed and long time relying on heat conduction on the basis of existing direct absorption type solar thermal collectors. By adding a device to the middle area where the temperature rises slowly, the middle area absorbs light and heat at a speed synchronized or nearly synchronized with other parts, thereby further improving the heat collection, energy storage efficiency and heat transfer efficiency of the collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0019] Figure 2 It is a schematic structural diagram of the solar energy absorption unit in the present invention;

[0020] Figure 3 is a schematic diagram of the light reflecting surface reflecting sunlight in the present invention;

[0021] Figure 4 It is an enlarged schematic diagram of the solar energy absorption principle of the enhanced lattice absorption unit in the present invention.

[0022] Description of reference numerals:

[0023] 1-glass vacuum outer tube, 2-water storage tube, 3-heat collecting tube, 4-fixed baffle, 5-screw cap, 6-water outlet, 7-anticorrosion sealing material, 8-absorbent inlet and outlet, 9-water inlet, 10-screw cap, 11-optical fiber, 12-enhanced lattice absorption unit, 13-light reflecting surface, 14-tripod, 15-fixer, 16-bracket, 17-permanent magnet, 18-controller, 19-rotating disk. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below through specific embodiments and drawings. The following embodiments are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0025] Example 1

[0026] like Figure 1 and 2 As shown, a fluid lattice type magnetically controlled enhanced absorption solar energy heat collection device comprises a concentrator and a solar energy absorption unit installed above the concentrator, a permanent magnet 17 is provided at the bottom of the concentrator, the permanent magnet 17 is located above a rotating disk 19, the rotating disk 19 is connected to a controller 18 for controlling the rotation of the rotating disk 19, and the controller 18 and the rotating disk 19 are both connected to a power supply; the solar energy absorption unit comprises a heat collecting tube 3 and a water storage tube 2 (made of glass) and a glass vacuum inner tube 1 which are sequentially embedded on the outside of the heat collecting tube, a transverse and longitudinal arc optical fiber 11 is provided inside the heat collecting tube, and an enhanced lattice absorption unit 12 is provided on the arc optical fiber 11.

[0027] The water storage pipe 2, the glass vacuum inner pipe 1 and the heat collecting pipe 3 are fixed on one side of the fixed baffle 4, and the other side of the fixed baffle 4 is respectively provided with a water inlet 9 and a water outlet 6 connected to the water storage pipe 1, and an absorption medium inlet and outlet 8 connected to the heat collecting pipe 3. The controller 18 is connected to a photosensitive sensor, and the power supply is a solar panel, which is used to store energy and provide energy for the rotation of the rotating disk 19 and the operation of the intelligent controller 18. The power supply device can also be selected according to needs, and batteries, generators or directly connected to household or industrial circuits can also be used.

[0028] The concentrator includes a metal semi-arc light reflecting surface 13, and the surface of the reflecting surface 13 is coated with a high reflectivity film. The sunlight around the heat collecting tube is focused by the reflecting surface and concentratedly reflected on the heat collecting tube and absorbed by the absorbing medium in the heat collecting tube. At the same time, some light that has not been absorbed by the absorbing medium and thus penetrates the vacuum inner tube can be reflected again by the focusing light reflecting surface 13 to achieve the effect of secondary absorption, thereby improving the absorption of the part farthest from the sun in the heat collecting tube. The solar energy absorption unit is fixed on the inner concave surface of the light reflecting surface 13 by a fixer 15 and a bracket 16. The two ends of the light reflecting surface 13 are fixed on the tripod 14. Screw caps 5 and 10 are installed on the water inlet 6 and the water outlet 9, which are used for connecting and fixing the water inlet, the water outlet and the water pipe. The absorbing medium inlet and outlet 8 are provided with a sealing material 7, which can seal the absorbing medium inside the heat collecting tube 3 to prevent it from leaking.

[0029] According to the time and arc from the rising to the setting of the sun, the speed of the sun's movement is reasonably calculated, so as to set the angular velocity of the rotating disk 19, so that the permanent magnet 17 embedded in the rotating disk 19 is always facing the sun, so that the enhanced lattice absorption unit 12 controlled by the permanent magnet 17 and the nanoparticle aggregates in the absorption medium can maximize the absorption of the sun's light and heat along the direction of the sun's rays and the fastest heat transfer. At the same time, the length of the time period from the rising to the setting of the sun is different in different seasons, so a photosensitive sensor is set on the surface of the controller as the working switch of the rotating disk 19. When the photosensitive sensor senses sunlight, the rotating disk 19 starts working. When night falls and the photosensitive sensor cannot sense light, the rotating disk 19 stops working. The enhanced lattice absorption unit 12 is a magnetic particle adsorbed with a magnetic high thermal conductivity composite material, and the magnetic high thermal conductivity composite material is a composite nanomaterial of ferroferric oxide modified carbon nanotubes.

[0030] The heat collecting tube 3 contains an absorption medium, which is a mixed liquid in which Fe3O4-graphene composite functional nano magnetic fluid is added to a base liquid.

[0031] The above materials can be purchased from the market or prepared by referring to the existing technology. The present invention provides a preparation method of an absorption medium and a reinforced lattice absorption unit.

[0032] Example 2 Preparation of Absorbent

[0033] The Fe3O4-graphene composite functional nano-magnetic fluid is prepared by a two-step method. A trace amount of sodium tripolyphosphate is added to the heat-conducting oil, and ultrasonic oscillation is performed for 20 minutes under a water bath condition of 50°C to prepare a heat-conducting oil solution of sodium tripolyphosphate with a mass concentration of 2g / L. A certain mass of dry nano-Fe3O4 powder and nano-graphene are weighed, added to the sodium tripolyphosphate heat-conducting oil solution, and a composite solution with a volume fraction of 5% is prepared. The solution is stirred with a magnetic heating stirrer, heated and stirred to 70°C, and ultrasonic oscillated for 40 minutes under a water bath condition of 70°C, so that Fe3O4 can be completely wrapped on the surface of graphene to form composite magnetic particles, which are uniformly dispersed in the solution under the action of the dispersant. Graphene has good heat absorption and heat conduction properties but no magnetism, and Fe3O4 has magnetism but poor heat absorption. The composite functional nano-magnetic fluid prepared above not only has good heat absorption and heat conduction properties, but also has magnetism, can be controlled by a magnetic field, and can aggregate under the action of a magnetic field.

[0034] Example 3 Preparation of Strengthened Lattice Absorption Unit:

[0035] Magnetic ferroferric oxide nanoparticles were prepared by chemical coprecipitation. NH3·H2O was used as a precipitant. A certain amount of FeCl2 and FeCl3 mixed solution was added to a beaker, and then 28% ammonia water was added to the beaker. Mechanical stirring, constant temperature in a water bath, electric stirring for 45 minutes, and then placed on a magnet. After the black solid was completely precipitated, the supernatant was discarded. Repeated washing with distilled water until the pH was neutral, and drying in a 60℃ vacuum drying oven for 24 hours to obtain magnetic ferroferric oxide nanoparticles.

[0036] Take 1g of pretreated carbon nanotubes and put them into a 100mL flask. Add 15mL of concentrated nitric acid and 45mL of concentrated sulfuric acid in turn. Install the reflux condenser and absorption device, and heat to reflux for 0.5h. After cooling to room temperature, filter the excess acid, and the remaining powdery substance is pure carbon nanotubes. Wash the obtained carbon nanotubes with deionized water until the pH value is 7. Finally, put the washed carbon nanotubes into an oven and dry for 2h to obtain pure carbon nanotubes.

[0037] The obtained magnetic ferroferric oxide nanoparticles and pure carbon nanotubes were placed in a ball mill for 3 hours and 1 hour respectively. 80 mg of ball-milled multi-walled carbon nanotubes were weighed and added to 25 mL of triethylene glycol solution, and ultrasonicated for 10 minutes; then 200 mg of ball-milled magnetic Fe3O4 nanoparticles were added while stirring with magnetic force, and the mixed solution was placed in a heat-collecting constant temperature heating magnetic stirrer and heated to 280°C, and maintained for 30 minutes, and then naturally cooled to room temperature. Dilute with ethanol and separate the product from the aqueous solution through the magnetic adsorption process using a commercial magnet; finally, wash it repeatedly with ethanol and dry it in a vacuum oven to obtain a composite nanomaterial of ferroferric oxide-modified carbon nanotubes.

[0038] The strong magnetic steel is crushed and ball-milled for 1 hour, and then the ball-milled steel particles are evenly adhered to the optical fiber with a two-component epoxy glue. After that, the prepared composite nanomaterial of ferroferric oxide modified carbon nanotubes is adsorbed on the steel fixed on the optical fiber, and the two ends of the composite optical fiber are fixed to the wall of the collector tube with aerogel so that it is suspended in the middle position of the collector tube.

[0039] Example 4 Working Principle

[0040] When the photosensor senses sunlight, the controller 18 issues an instruction to control the rotating disk 19 to start rotating with the permanent magnet 17, and turns to the direction facing the sun. At this time, the device starts to work. The sunlight first shines on the water through the transparent glass vacuum outer tube 1 and the glass water storage tube 2. A small part of the sunlight is absorbed by the water filled between the glass vacuum inner tube 2 and the heat collecting tube 3. Most of the sunlight that is not absorbed by the water passes through the water to the absorption medium installed in the heat collecting tube 3. The part of the absorption medium closest to the sun begins to collect heat. At the same time, the sunlight irradiated on the light reflecting surface 13 is concentrated and reflected by the light reflecting surface 13 and enters the water below the heat collecting tube 3. Figure 3 As shown, similarly, the part that passes through the water is absorbed and stored by the part in the absorbing medium. Since the part of the absorbing medium is added with optical fiber 11 and the enhanced lattice absorption unit 12 fixed on the surface of the optical fiber 11, the light and heat absorption of the part is improved, and a large amount of light and heat is partially absorbed and stored. Since the ability of the absorbing medium to absorb light and heat is faster than that of water, the absorbing medium transfers the heat it absorbs to the water. Through heat transfer, the water temperature is increased, and cold water continuously enters from the water inlet 9. The heated hot water is discharged from the water outlet 6 for daily household or industrial use. The irradiation angle of sunlight is different in different time periods. The controller-18 controls the rotating disk-19 and the permanent magnet-17 to always rotate in the direction of the sun to receive the strongest sunlight to the greatest extent. The solar energy absorption device part in this device can also be arranged in a large-scale socket to meet the needs of different application occasions.

[0041] Example 5 Comparative Experiment Photothermal Test:

[0042] The device of the present invention and the device of patent CN110195938A were subjected to photothermal test. 2 ) and tested by the temperature inspection instrument. The test results are shown in the following table. Figure 3 As shown, Table 1 is the test result of the patent CN110195938A device, and Table 2 is the device described in the present invention. The patent CN110195938A device is a fluid that transfers heat from the outside to the inside. It can be found from Table 1 that the temperature gradually decreases from the outside to the inside, and the water contacts the lowest temperature of the fluid, so the heat transfer is slow. In the present invention, the fluid transfers heat from the inside to the outside, and the water contacts the highest or higher temperature of the fluid, so the heat transfer is fast. It can be found from Table 2 that the temperature difference between different positions is small, which reduces the heat transfer inside the fluid and accelerates the heat transfer from the fluid to the water.

[0043] Table 1

[0044]

[0045] Table 2

[0046]

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fluid lattice type magnetically controlled enhanced absorption solar thermal collector, comprising a concentrator and a solar absorption unit installed above the concentrator, characterized in that: A permanent magnet is provided at the bottom of the concentrator, and the permanent magnet is located above a rotating disk. The rotating disk is connected to a controller for controlling the rotation of the rotating disk, and the controller and the rotating disk are both connected to a power supply; the solar energy absorption unit includes a heat collecting tube and a water storage tube and a glass vacuum inner tube which are sequentially embedded on the outside of the heat collecting tube. The heat collecting tube is provided with transverse and longitudinal arc optical fibers inside, and an enhanced lattice absorption unit is provided on the arc optical fiber. The enhanced lattice absorption unit is a magnet particle adsorbed with a magnetic high thermal conductivity composite material.

2. The solar thermal collector according to claim 1, characterized in that: The magnetic high thermal conductivity composite material is a composite nano material of ferroferric oxide modified carbon nanotubes.

3. The solar thermal collector according to claim 1, characterized in that: The heat collecting tube contains an absorption medium inside, and the absorption medium is a mixed liquid in which Fe3O4-graphene composite functional nano magnetic fluid is added to a base liquid.

4. The solar thermal collector according to claim 3, characterized in that: The base liquid is heat transfer oil, water or ethylene glycol.

5. The solar thermal collector according to claim 1, characterized in that: The water storage pipe, glass vacuum inner pipe and heat collecting pipe are fixed on one side of the fixed baffle, and the other side of the fixed baffle is respectively provided with a water inlet and a water outlet connected to the water storage pipe, and connected to the absorption medium inlet and outlet of the heat collecting pipe.

6. The solar thermal collector according to claim 1, characterized in that: The controller is connected with a photosensor, and the power source is a solar panel.

7. The solar thermal collector according to claim 1, characterized in that: The concentrator comprises a metal semi-arc light reflecting surface, and the surface of the reflecting surface is plated with a high reflectivity film.

8. The solar thermal collector according to claim 7, characterized in that: The solar energy absorption unit is supported on the inner concave surface of the light reflecting surface through a bracket.

9. The solar thermal collector according to claim 7, characterized in that: The two ends of the light reflecting surface are fixed on the tripod.

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