System and method for triggering solidification and energy release of supercooled hydrated salt solution by utilizing magnetic attraction friction

Abstract

The invention provides a system and method for triggering solidification and energy release of a supercooled hydrated salt solution through magnetic attraction friction. The system consists of a fixed bracket, a disc, a magnet fixing device, a hoop, a cushion block, a motor, a magnet, a supercooled hydrated salt solution, a bearing steel ball, a heat storage unit, a power supply, a temperature data acquisition instrument, a four-wire system PT100 film platinum resistor and a computer. The fixing support, the disc and the magnet fixing device are used for fixing magnets. The hoop and the cushion block are used for fixing the heat storage unit; the motor is used for applying external force to the magnet; the magnet is used for applying a magnetic field to the bearing steel ball, magnetic attraction friction is generated under the driving of the motor, and the supercooled hydrated salt phase change material is caused to solidify and release energy; the supercooled hydrated salt solution is used for storing heat; the bearing steel ball is used for cooperating with the magnet to trigger the hydrated salt solution to solidify and release energy; the power supply is used for rotating the motor; the temperature data acquisition instrument is used for collecting temperature data measured by the four-wire PT100 film platinum resistor; the four-wire PT100 film platinum resistor is used for measuring the temperature change of the surface of the small heat storage tank in the energy release process of the supercooled hydrated salt phase change material; and the computer is used for recording and displaying the temperature data. The defects that other triggering modes are complex (such as ultrasonic waves), induction time is too long (such as local low temperature), a heat storage container is prone to being damaged (such as mechanical vibration) and the like are overcome, the method has the advantages of being easy and effective to operate, short in triggering time, free of contact with samples and the like, pollution is avoided, and long-term use of the system is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of novel environmentally friendly and efficient energy storage equipment, and in particular relates to a system and method for utilizing magnetic attraction friction to trigger the solidification and energy release of a supercooled hydrated salt solution. Background Art

[0002] The rapid development of global economy, culture and science and technology has brought about increasingly urgent problems of fossil energy consumption and environmental pollution. In the context of sustainable development, more and more policies encourage the promotion of clean renewable energy to replace traditional energy. However, some renewable energy sources are seasonal and cyclical, which will lead to insufficient energy utilization. Research on cross-seasonal energy storage is an important measure to solve this problem. Using magnetic friction to trigger the solidification and energy release of supercooled hydrated salt solutions can effectively store energy and release energy efficiently when needed, which has broad research prospects.

[0003] Thermal energy storage mainly includes three methods: sensible heat storage, latent heat storage and chemical reaction heat storage. The high heat storage density of sensible heat storage requires the use of mechanical equipment with huge volume, complicated processes and complex operations. The current technical maturity of chemical reaction heat storage is low, the system is complex and the investment cost is high, and the process of storing and releasing heat is difficult to control. Latent heat storage has the characteristics of high energy density, long-term storage, stability, reversibility and environmental friendliness, and has broad application prospects in energy storage and regulation. Compared with organic phase change materials, the advantages of inorganic phase change materials are that they have suitable temperature, high phase change latent heat and thermal conductivity, and good stability.

[0004] Inorganic phase change materials have a moderate temperature, between 0℃ and 150℃, and have high phase change latent heat and thermal conductivity, which can achieve energy storage and transmission more efficiently. In addition, inorganic phase change materials usually have good stability and can maintain stable performance during long-term use. Therefore, inorganic phase change materials are widely studied and applied in the field of low-temperature heat storage, providing a possibility for improving the efficiency and performance of heat storage systems. Inorganic phase change materials include inorganic hydrated salts, molten salts and metal materials. Molten salts and metal alloys have high melting points and are the preferred materials for large-scale medium and high temperature heat storage technology. Inorganic hydrated salts store and release energy through heat absorption and heat release during melting and crystallization, and have the advantages of high energy storage density, wide energy storage temperature range, low cost and stable performance. Long-term energy storage can be achieved by utilizing the stable supercooling characteristics of hydrated salts. When there is a demand for heat, the supercooled liquid hydrated salt phase change material is triggered to solidify and release latent heat, that is, the long-term energy storage of supercooled hydrated salts is mainly divided into three stages: heat charging, heat storage and triggering energy release. At present, the methods for triggering the solidification and energy release of supercooled hydrated salts include ultrasonic vibration, mechanical vibration, local low temperature, application of electric field and magnetic field, etc. Among them, the method of applying magnetic field is simple, effective and safe, but there is very little research on applying magnetic field to trigger the energy release of hydrated salts. Summary of the invention

[0005] The present invention brings a magnet into contact with the surface of a supercooled heat storage unit equipped with bearing steel balls. The magnet applies a magnetic field to the bearing steel balls. The magnet is driven by an external force to perform uniform circular motion. A magnetic torque is generated between the bearing steel balls due to changes in the magnetic field. Friction is generated between the bearing steel balls under the action of the magnetic torque. The friction force triggers the supercooled hydrated salt solution to solidify and release heat, which is of great significance for medium and low temperature cross-seasonal energy storage.

[0006] The present invention proposes a system and method for magnetic friction-triggered solidification and energy release of supercooled hydrated salt solution, which is composed of a fixed bracket, a disc, a magnet fixing device, a clamp, a cushion block, a motor, a magnet, a supercooled hydrated salt solution, a bearing steel ball, a heat storage unit, a power supply, a temperature data acquisition instrument, a four-wire PT100 thin film platinum resistor, and a computer. The fixing bracket, disc and clamp are used to fix the heat storage unit and the motor; the motor, disc, magnet fixing device and clamp enable the motor to drive the magnet to perform uniform circular motion, causing changes in magnetic lines of force, thereby generating a magnetic torque between the two balls. The magnetic torque causes friction between the balls, causing the supercooled hydrated salt phase change material to solidify and release energy; the magnet is used to apply a magnetic field to the bearing steel ball; the supercooled hydrated salt solution is used to store heat; the bearing steel ball is used to cooperate with the magnet to trigger the supercooled hydrated salt solution to solidify and release energy; the heat storage unit is used to store the supercooled hydrated salt phase change material; the power supply is used to provide electrical energy to the motor; the four-wire PT100 thin film platinum resistor is used to measure the temperature change on the surface of the heat storage unit during the energy release process of the supercooled hydrated salt phase change material; the temperature data acquisition instrument is used to collect temperature data measured by the four-wire PT100 thin film platinum resistor; and the computer is used to record and display the temperature data.

[0007] Preferably, the fixing bracket, the disc, the magnet fixing device, the clamp and the spacer are made of 304 stainless steel.

[0008] Preferably, the motor is a permanent magnet synchronous motor with a power of 14 W, a torque of 1.96 N·m and a rotation speed of 10 rpm.

[0009] Preferably, the magnet is a N35 neodymium strong magnet with a maximum magnetic field strength of 260mT.

[0010] Preferably, the supercooled hydrated salt solution is a supercooled sodium acetate trihydrate solution with a purity of 99.1%.

[0011] Preferably, the bearing steel ball is made of GCr15 high carbon chromium bearing steel.

[0012] Preferably, the heat storage unit is in the shape of a round tank with rounded bottom, and is made of polyvinyl chloride.

[0013] Preferably, the magnet moves in a uniform circular rotation at the bottom of the heat storage unit.

[0014] The beneficial effects of the present invention are as follows: the method of triggering hydrated salt of the present invention only requires a motor to drive the magnet to absorb the steel ball and rotate to quickly trigger the hydrated salt solution to release heat energy. It has the advantage of quickly triggering the heat storage unit to release heat, making up for the shortcomings of other triggering operation methods such as complex operation (such as ultrasound), long induction time (such as local low temperature), and easy damage to the heat storage container (such as mechanical vibration). The system of the present invention is simple to operate, non-hazardous, and the magnet has no contact with the internal hydrated salt solution, which avoids pollution and facilitates long-term use of the system. In the system of the present invention, the number and diameter of the bearing steel balls in the supercooled heat storage unit can be adjusted to determine the optimal triggering conditions according to different working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a diagram of a magnetic friction trigger device;

[0016] Figure 2 It is a schematic diagram of the movement of the magnet at the bottom of the supercooling thermal storage unit;

[0017] Figure 3 This is the curve of the temperature change of the thermal storage unit over time when the thermal storage unit is triggered under different steel ball diameters (the moment when the magnet starts to move is time 0);

[0018] Figure 4 This is the curve of the temperature change of the thermal storage unit over time when the thermal storage unit is triggered under different numbers of steel balls (the moment when the magnet starts to move is time 0).

[0019] Figure 5 This is a schematic diagram of the effect of steel ball diameter D and number of steel balls N on induction time. DETAILED DESCRIPTION

[0020] To make the technical solution of the present invention clearer, the present invention is further described below in conjunction with the accompanying drawings. The present invention is specifically implemented according to the following steps:

[0021] The present invention proposes a system and method for triggering the solidification and energy release of supercooled hydrated salt solution by magnetic friction. The system is composed of a fixed bracket, a disc, a magnet fixing device, a clamp, a cushion block, a motor, a magnet, a supercooled hydrated salt solution, a bearing steel ball, a heat storage unit, a power supply, a temperature data acquisition instrument, a four-wire PT100 thin film platinum resistor, and a computer.

[0022] Figure 1The schematic diagram of the structure of the magnetic friction-triggered supercooled hydrated salt solution device includes 1, a fixed bracket; 2, a disc; 3, a magnet fixing device; 4, a clamp; 5, a pad; 6, a motor; 7, a magnet; 8, a supercooled hydrated salt solution; 9, a bearing steel ball; 10, a heat storage unit; 11, a power supply. In one embodiment of the present invention, the fixed bracket 1 is preferably stainless steel, made of 304, the disc 2 is preferably a stainless steel disc, with a diameter of 80 mm and a thickness of more than 3 mm, and the motor and the disc are connected by threads. The magnet fixing device 3 is preferably a square, uncovered stainless steel, made of 304, and the magnet fixing device and the disc are connected by welding. The clamp 4 and the pad 5 are preferably made of 304 stainless steel, and the two fix the heat storage unit 10 together. The motor 6 is preferably a permanent magnet synchronous motor with a power of 14W, a torque of 1.96N·m, and a speed of 10rpm. The magnet 7 is preferably an N35 neodymium strong magnet with a size of 50×30×20mm and a maximum magnetic field strength of 260mT. The supercooled hydrated salt solution 8 is preferably a sodium acetate trihydrate solution. The bearing steel ball 9 is preferably a GCr15 high carbon chromium bearing steel, and its diameter is 12, 14, 16, 18, 20 mm, and the number of bearing steel balls N is ≥ 2. The thermal storage unit 10 is preferably an experimental grade homogeneous round tank, and its shape is a circle with a bottom diameter of 80 mm and a height of 92 mm. The power supply 11 is preferably an AC 220V circuit.

[0023] A temperature measuring point is distributed at the bottom of the thermal storage unit, located in the center of the bottom of the unit. Preferably, a four-wire PT100 thin film platinum resistor is arranged at the temperature measuring point to measure the temperature. The collected temperature data is sent to the computer using a data acquisition instrument, and the computer records and displays the temperature change curve over time.

[0024] To illustrate the method proposed by the present invention for triggering the solidification and energy release of a supercooled hydrated salt solution by magnetic friction, in an implementation example of the present invention, it is necessary to first heat the heat storage unit containing the hydrated salt solution to 80°C and maintain it for 8 hours, then stop heating, and cool it in the environment for 14 hours to reach a supercooled state. At this time, the hydrated salt phase change material is in a supercooled liquid state and eventually exists in the heat storage unit in a long-term and stable supercooled state to store the heat of fusion.

[0025] A four-wire PT100 thin-film platinum resistor is used as a temperature sensor and fixed at the bottom center of the thermal storage unit to monitor the temperature change of the thermal storage unit. The induction time is defined as: from the moment the motor starts to rotate to the moment when the temperature suddenly rises (crystallization of the supercooled solution occurs), that is, Figure 3 and Figure 4 The time from the inflection point of the sudden rise of the temperature curve shown in . The temperature data is collected by Agilent 34907A data acquisition instrument, and recorded and displayed by computer.

[0026] When heat supply is needed (such as heating or domestic hot water demand in cold winter), the method of the present invention is used to absorb the steel ball with a magnet so that the magnet performs the following steps: Figure 2 As shown in the rotation, the rotation of the magnet causes the change of the magnetic lines of force, which in turn generates a torque between the two balls (i.e., a rotational force, which is called magnetic torque in magnetism). This torque twists the bearing steel balls together like a pretzel. The friction generated by the rotation causes the molecules to aggregate to reach the critical nucleation radius, forming an initial crystal nucleus, which in turn triggers the crystallization of the entire solution and releases the heat of fusion.

[0027] There is an optimal ratio between the diameter D of the steel ball and the number N of the steel balls (the combination with the shortest induction time). The results are as follows: Figure 5 As shown: when the number of steel balls N is 2, the diameter D of the steel ball with the shortest induction time is 18 mm; when the number of steel balls N is 3, the diameter D of the steel ball with the shortest induction time is 16 mm; when the number of steel balls N is 4, the diameter D of the steel ball with the shortest induction time is 14 mm.

[0028] The above embodiments are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A magnetic friction-triggered system for solidification and energy release of supercooled hydrated salt solution, which consists of a fixed bracket, a disc, a magnet fixing device, a clamp, a pad, a motor, a magnet, a supercooled hydrated salt solution, a bearing steel ball, a heat storage unit, a power supply, a temperature data acquisition instrument, a four-wire PT100 thin-film platinum resistor, and a computer. The fixing bracket, disc and clamp are used to fix the heat storage unit and the motor; the motor, disc, magnet fixing device and clamp enable the motor to drive the magnet to perform uniform circular motion to cause the change of magnetic lines of force, thereby generating a magnetic torque between the two balls. The magnetic torque causes friction between the balls, causing the supercooled hydrated salt phase change material to solidify and release energy; the magnet is used to apply a magnetic field to the bearing steel ball; the supercooled water and salt solution are used to store heat; the bearing steel ball is used to cooperate with the magnet to trigger the supercooled hydrated salt solution to solidify and release heat; the heat storage unit is used to store the supercooled hydrated salt phase change material; the power supply is used to provide electrical energy to the motor; the four-wire PT100 thin film platinum resistor is used to measure the temperature change on the surface of the heat storage unit during the energy release process of the supercooled hydrated salt phase change material; the temperature data acquisition instrument is used to collect temperature data measured by the four-wire PT100 thin film platinum resistor; and the computer is used to record and display the temperature data.

2. The fixing bracket, disc, magnet fixing device, clamp and spacer according to claim 1 are all made of 304 stainless steel.

3. The motor according to claim 1 is a permanent magnet synchronous motor with a power of 14 W, a torque of 1.96 N·m and a rotation speed of 10 rpm.

4. The magnet model according to claim 1 is N35, and the maximum magnetic field strength is 260mT.

5. The supercooled hydrated salt solution according to claim 1 is a supercooled sodium acetate trihydrate solution with a purity of 99.1%.

6. The bearing steel ball according to claim 1 is made of GCr15 high carbon chromium bearing steel.

7. The heat storage unit according to claim 1 is characterized in that it is made of polyvinyl chloride and has an experimental grade homogeneous round tank shape.

8. The system for releasing energy by solidification of supercooled hydrated salt solution by magnetic friction triggering according to claim 1, characterized in that: A temperature measuring point is distributed at the center of the bottom surface of the small heat storage tank.

9. A method for triggering the solidification and energy release of a supercooled hydrated salt solution heat storage unit by using the magnetic attraction-triggered supercooled hydrated salt solution solidification and energy release system as described in any one of claims 1 to 8, characterized in that: The small heat storage tank filled with the hydrated salt phase change material is fixed on a fixing device; after the small heat storage tank is fully cooled to room temperature, a magnet is slowly adsorbed on the bottom of the small heat storage tank, and then the motor is powered on to drive the magnet to perform uniform circular motion to solidify the hydrated salt phase change material and release the melting heat.

10. A method for triggering the solidification and energy release of a supercooled hydrated salt thermal storage unit by using a magnetic attraction friction-triggered supercooled hydrated salt solution solidification and energy release system according to claims 1-9, characterized in that: The number of bearing steel balls in the small heat storage tank is 2, 3, or 4, and the diameters are 12, 14, 16, 18, or 20 mm.

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