A solar heat recovery cycle system based on phase change material

Abstract

The application relates to the technical field of phase change energy storage, and discloses a solar heat recovery circulating system based on a phase change material, which comprises a packaging container and a light collecting cover plate located at the upper end of the packaging container, a crystal box is jointly arranged between a second crystal conveying pipe and a first crystal conveying pipe, and the crystal box and the inside of the packaging container are both filled with composite phase change fillers. The composite phase change fillers are simultaneously filled into the packaging container and the crystal box with a grinding function. In each crystallization heat absorption, the composite phase change fillers in the crystal box are added into the packaging container through a second conveying pump and the first crystal conveying pipe, and the composite phase change fillers are mechanically stirred in the packaging container, so that supercooling can be completely eliminated, and the cycle life and the cycle stability are very good. The composite phase change fillers are prepared from nano aluminum nitride, foamed copper, deionized water and sodium acetate trihydrate, and have the characteristics of high latent heat, high thermal conductivity, no phase separation, no supercooling and good stability.

Description

Technical Field

[0001] This invention relates to the field of phase change energy storage technology, specifically a solar thermal recovery cycle system based on phase change materials. Background Technology

[0002] With the rapid development of science and technology and the improvement of living standards, global primary energy consumption has increased dramatically. Overexploitation and utilization of fossil fuels have caused serious environmental pollution and ecological damage, attracting widespread attention from governments and research institutions worldwide. The use of renewable energy is considered an effective way to meet the rapidly growing energy demand and solve the environmental problems caused by traditional fossil fuels. Actively promoting and developing renewable energy has become an important means of solving ecological problems and reducing carbon emissions. Under these conditions, solar thermal energy has developed rapidly. Due to the intermittent and fluctuating nature of solar energy, there is a mismatch between energy supply and demand in solar energy systems. Therefore, energy storage technology is an effective way to solve this contradiction. Among various energy storage technologies, phase change thermal energy storage technology has advantages such as low cost and long lifespan. It also has high energy density, making it suitable for large-capacity energy storage. It can solve the contradiction of energy supply imbalance in time and space, meet the application needs of large-scale power peak shaving, multi-energy complementarity, and efficient utilization, and is conducive to large-scale commercial promotion and application. Therefore, developing efficient phase change thermal energy storage technology to meet the needs of modern applications is of great practical significance. The core of phase change thermal energy storage technology is phase change materials.

[0003] Phase change materials are characterized by high latent heat of fusion and long cycle life. Among them, sodium acetate trihydrate is one of the main phase change materials. Although sodium acetate trihydrate has a high latent heat, its thermal conductivity is very low. At the same time, the melting process is accompanied by phase separation and supercooling. These disadvantages seriously affect its application and promotion.

[0004] Chinese patent discloses an energy-saving phase change material energy storage agent and its preparation method and production equipment (Announcement No. CN104559 937A). The phase change material energy storage in this patented technology is prepared from sodium acetate trihydrate, sodium metasilicate pentahydrate, gelatin and diglycerol. It can eliminate some separation and supercooling phenomena, but its elimination of separation and supercooling phenomena is incomplete, resulting in poor cycle life and cycle stability of the phase change material. Summary of the Invention

[0005] The purpose of this invention is to provide a solar thermal recovery cycle system based on phase change materials to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A solar thermal recovery cycle system based on phase change materials includes an encapsulation container and a concentrating cover plate located on the upper part of the encapsulation container. The outer side and bottom of the encapsulation container are jointly wrapped with an integrated insulation layer, and a mechanical rotor is set at the center of the lower inner side of the encapsulation container. A temperature sensor is installed on the inner side wall of the encapsulation container, and a liquid level detector is set at the upper inner side of the encapsulation container. A second crystal delivery pipe and a first crystal delivery pipe are respectively installed through the left and right sides of the upper end of the concentrating cover plate. A crystal box is installed between the second crystal delivery pipe and the first crystal delivery pipe. A magnetic stirrer is installed at the bottom of the integrated insulation layer. The crystal box and the interior of the encapsulation container are both filled with composite phase change filler.

[0008] As a further embodiment of the present invention: the crystal box is electrically connected to a first controller and a second controller, and the first controller, the second controller, the temperature sensor and the liquid level detector are all electrically connected to a computer.

[0009] As a further embodiment of the present invention: a first delivery pump is provided inside the second crystal delivery tube, and a second delivery pump is provided inside the first crystal delivery tube.

[0010] As a further aspect of the present invention: the crystal box is a crystal box with a built-in grinding function.

[0011] As a further embodiment of the present invention: the composite phase change filler is prepared from hydrated salt phase change thermal storage material, comprising the following components by mass percentage: 0.4% to 1% nano aluminum nitride, 1% to 4% copper foam, 0.5% to 2% deionized water, and 93% to 98.1% sodium acetate trihydrate.

[0012] As a further aspect of the present invention, the preparation method of the composite phase change filler includes the following steps:

[0013] S1. Melt sodium acetate trihydrate crystals with a mass percentage of 93% to 98.1% by heating, and then add 0.4% to 1% nano aluminum nitride, 1% to 4% copper foam, and 0.5% to 2% deionized water to obtain a mixed solution.

[0014] S2. Nucleation reaction is carried out under continuous stirring of the mixed solution to obtain composite phase change filler.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] This invention simultaneously loads a composite phase change filler into a packaging container and a crystal box with a built-in grinding function. During each crystallization endothermic process, the composite phase change filler in the crystal box is added to the packaging container via a second delivery pump and a first crystal delivery pipe. The composite phase change filler is mechanically stirred in the packaging container, thereby completely eliminating supercooling and achieving excellent cycle life and cycle stability. The composite phase change filler is prepared from nano-aluminum nitride, foamed copper, deionized water, and sodium acetate trihydrate, and features high latent heat, high thermal conductivity, no phase separation, no supercooling, and good stability. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a solar thermal recovery cycle system based on phase change materials;

[0018] In the diagram: 1. First controller; 2. Crystal box; 3. Computer; 4. Second controller; 5. First crystal delivery tube; 6. Mechanical rotor; 7. Encapsulation container; 8. Composite phase change packing; 9. Magnetic stirrer; 10. Second crystal delivery tube; 11. Temperature sensor; 12. Integrated insulation layer; 13. Focusing cover plate; 14. Liquid level detector; 15. First delivery pump; 16. Second delivery pump. Detailed Implementation

[0019] Please see Figure 1 In this embodiment of the invention, a solar thermal recovery cycle system based on phase change material includes a packaging container 7 and a concentrating cover plate 13 located at the upper end of the packaging container 7. The outer side and bottom of the packaging container 7 are jointly wrapped with an integrated heat preservation layer 12, and a mechanical rotor 6 is provided at the center of the lower inner side of the packaging container 7. A temperature sensor 11 is installed on the inner side wall of the packaging container 7, and a liquid level detector 14 is provided at the upper inner side of the packaging container 7. A second crystal delivery pipe 10 and a first crystal delivery pipe 5 are respectively provided through the left and right sides of the upper end of the concentrating cover plate 13. A crystal box 2 is installed between the second crystal delivery pipe 10 and the first crystal delivery pipe 5. A magnetic stirrer 9 is installed at the bottom of the integrated heat preservation layer 12. The crystal box 2 and the interior of the packaging container 7 are both filled with composite phase change filler 8.

[0020] Preferably, the crystal box 2 is electrically connected to a first controller 1 and a second controller 4, and the first controller 1, the second controller 4, the temperature sensor 11 and the liquid level detector 14 are all electrically connected to a computer 3.

[0021] Preferably, a first delivery pump 15 is provided inside the second crystal delivery pipe 10, and a second delivery pump 16 is provided inside the first crystal delivery pipe 5.

[0022] Preferably, the crystal box 2 is a crystal box with a built-in grinding function.

[0023] Preferably, the composite phase change filler 8 is prepared from hydrated salt phase change thermal storage material, comprising the following components by mass percentage: 0.4%–1% nano aluminum nitride, 1%–4% copper foam, 0.5%–2% deionized water, and 93%–98.1% sodium acetate trihydrate.

[0024] The preferred mass percentage of nano-aluminum nitride is 0.8 wt%. When the mass percentage of nano-aluminum nitride is 0.8 wt%, the supercooling of sodium acetate trihydrate can be reduced from 30℃ to 1.5℃. The preferred mass percentage of foamed copper is 3 wt%. Foamed copper can improve the thermal conductivity and solve phase separation in a short time. The preferred mass percentage of deionized water is 0.75 wt%. An appropriate amount of deionized water can also solve phase separation well in a short time without affecting latent heat and supercooling.

[0025] Preferably, the preparation method of the composite phase change filler 8 includes the following steps:

[0026] S1. Melt sodium acetate trihydrate crystals with a mass percentage of 93% to 98.1% by heating, and then add 0.4% to 1% nano aluminum nitride, 1% to 4% copper foam, and 0.5% to 2% deionized water to obtain a mixed solution.

[0027] S2. Nucleation reaction is carried out under continuous stirring of the mixed solution to obtain composite phase change filler 8. Nano aluminum nitride can solve the supercooling of sodium acetate trihydrate and improve the latent heat. Mechanical stirring can solve the phase separation of sodium acetate trihydrate and also solve the supercooling. When nano aluminum nitride and mechanical stirring work together, the supercooling of sodium acetate trihydrate can be completely eliminated.

[0028] Sodium acetate trihydrate has a phase change temperature of 58℃, a supercooling of 25-30℃, a latent heat of phase change of 268kJ / kg, and a thermal conductivity of 0.62 w / (m•k). The composite phase change filler 8 prepared by this invention does not exhibit supercooling or phase separation, and has excellent cycle stability. Its thermal conductivity can be increased from 0.62 w / (m•k) to 2.3 w / (m•k), while maintaining a latent heat as high as 240 kJ / kg.

[0029] The working principle of this invention is as follows:

[0030] S10. The prepared composite phase change filler 8 is loaded into the encapsulation container 7 and the crystal box 2 with a built-in grinding function, respectively.

[0031] S20. When sunlight shines on the concentrating cover plate 13 on the encapsulation container 7 during the day, the concentrating cover plate 13 will concentrate the solar energy onto the composite phase change filler 8 until the composite phase change filler 8 is completely melted. At this time, except for the concentrating cover plate 13 which is in direct contact with the outside, the other walls of the encapsulation container 7 are sealed with an integrated heat insulation layer 12 to reduce heat dissipation.

[0032] After the composite phase change filler 8 in the encapsulation container 7 is completely melted, it is sealed. When crystallization and heat release are required, the temperature sensor 11 measures the temperature of the composite phase change filler 8 in the encapsulation container 7. When the temperature reaches 58-60℃, the signal is transmitted to the computer 3. Then, the control program of the computer 3 simultaneously executes two commands: one is to command the magnetic stirrer 9 to start, which drives the mechanical rotor 6 to rotate and stir the composite phase change filler 8 in the encapsulation container 7; the other is to command the second controller 4 to control the crystal box 2 with grinding function to grind the composite phase change filler 8 inside the crystal box 2. The ground composite phase change filler 8 is then sent into the encapsulation container 7 through the second delivery pump 16 and the first crystal delivery pipe 5 to provide crystal particles to the encapsulation container 7 for 3-5 seconds. The stirring and crystal addition by the mechanical rotor 6 can effectively solve the problems of phase separation and supercooling.

[0033] S40. After adding crystal particles multiple times, the liquid level detector 14 monitors the height of the solution level in the encapsulation container 7. When the height exceeds the set value, the computer 3 starts another program and commands the first controller 1 to extract a portion of the composite phase change filler 8 from the encapsulation container 7 through the first delivery pump 15 and the second crystal delivery pipe 10, and store it in the crystal box 2 with a built-in grinding function. After it becomes crystals, the first controller 1 starts the grinding function again to grind the composite phase change filler 8 in the crystal box 2 into small particles for the next cycle.

[0034] S50. The process from external heat absorption and melting to crystallization and heat release is considered as one cycle. If such a cycle is repeated 500 times without significant changes such as a decrease in latent heat, an increase in supercooling, or phase separation, it is considered to have good cycle life and cycle stability.

[0035] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A solar thermal recovery cycle system based on phase change materials, comprising a packaging container (7) and a concentrating cover plate (13) located at the upper end of the packaging container (7), characterized in that, The outer side and bottom of the encapsulation container (7) are wrapped with an integrated heat insulation layer (12), and a mechanical rotor (6) is provided at the center of the lower inner side of the encapsulation container (7). A temperature sensor (11) is installed on the inner wall of the encapsulation container (7), and a liquid level detector (14) is provided at the upper inner side of the encapsulation container (7). A second crystal delivery pipe (10) and a first crystal delivery pipe (5) are respectively installed through the left and right sides of the upper end of the focusing cover plate (13). A crystal box (2) is installed between the second crystal delivery pipe (10) and the first crystal delivery pipe (5). A magnetic stirrer (9) is installed at the bottom of the integrated heat insulation layer (12). The crystal box (2) and the encapsulation container (7) are both filled with composite phase change filler (8). The crystal box (2) is a crystal box with a built-in grinding function.

2. The solar thermal recovery cycle system based on phase change materials according to claim 1, characterized in that, The crystal box (2) is electrically connected to a first controller (1) and a second controller (4). The first controller (1), the second controller (4), the temperature sensor (11) and the liquid level detector (14) are all electrically connected to a computer (3).

3. A solar thermal recovery cycle system based on phase change materials according to claim 1, characterized in that, A first delivery pump (15) is provided on the inner side of the second crystal delivery pipe (10), and a second delivery pump (16) is provided on the inner side of the first crystal delivery pipe (5).

4. A solar thermal recovery cycle system based on phase change materials according to claim 1, characterized in that, The composite phase change filler (8) is prepared from hydrated salt phase change thermal storage material and includes the following components by mass percentage: 0.4% to 1% nano aluminum nitride, 1% to 4% copper foam, 0.5% to 2% deionized water, and 93% to 98.1% sodium acetate trihydrate.

5. A solar thermal recovery cycle system based on phase change materials according to claim 4, characterized in that, The preparation method of the composite phase change filler (8) includes the following steps: S1. Melt sodium acetate trihydrate crystals with a mass percentage of 93% to 98.1% by heating, and then add 0.4% to 1% nano aluminum nitride, 1% to 4% copper foam, and 0.5% to 2% deionized water to obtain a mixed solution. S2. Nucleation reaction is carried out under continuous stirring of the mixed solution to obtain composite phase change filler (8).

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