Experimental device and experimental method for phase change process of liquid-solid energy harvesting material

Abstract

The invention discloses an experimental device and an experimental method for a phase change process of a liquid-solid energy harvesting material, and belongs to the technical field of experimental equipment. The experimental device comprises a pressurization system, a liquid level monitoring device, a phase-change heat exchange cylinder and a radial size recording camera. The liquid level monitoring device is provided with a columnar sealing cavity filled with a phase change material and a liquid level monitoring sensor; the pressurizing system is used for pressurizing and measuring the pressure of the sealing cavity; the phase-change heat exchange cylinder is composed of a metal heat exchange pipe, a center liquid supplementing column and inner fins, an inner sealed heat exchange cavity is divided into an inner cylinder cavity and an outer ring cavity through a cylindrical heat insulation wall, the outer ring cavity is provided with radial inner fins, and a transparent end cover at the top facilitates recording of radial phase-change boundary images. The device has the advantages of being flexible in structure, visible in process, quantifiable in data and the like, and provides support for research and application of a liquid-solid energy harvesting technology in a marine environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of experimental equipment, and in particular relates to an experimental device and an experimental method for a phase change process of a liquid-solid energy-harvesting material. Background Art

[0002] In recent years, with the continuous development of phase change energy capture technology, researchers have begun exploring the application of the thermal expansion and contraction properties of liquid-solid phase change materials in ocean temperature environments to underwater equipment. By exploiting the temperature differences at different depths in the seawater, the phase change material is driven to repeatedly transform between liquid and solid states, thereby achieving mechanical energy output or energy storage. This technology can provide a continuous and stable micropower energy supply for underwater sensors, autonomous vehicles, and other equipment, and is expected to enhance the endurance and intelligence level of underwater equipment, becoming a key direction for the next generation of ocean energy utilization.

[0003] Currently, the application of liquid-solid phase change energy harvesting technology in underwater marine environments still faces a series of key technical bottlenecks. First, the longitudinal temperature gradient of seawater is small, with the surface temperature typically not exceeding 30°C, while the temperature at a depth of approximately 1,000 meters is only around 5°C. Furthermore, although the paraffin-based liquid-solid phase change materials commonly used in energy harvesting systems have a suitable phase transition temperature and high latent heat, their thermal conductivity is low, limiting the material's heat transfer efficiency during the phase change process, thereby affecting the overall energy conversion efficiency. Currently, there is a lack of experimental platforms that can systematically characterize the thermal behavior of liquid-solid phase change, making it difficult to accurately obtain heat transfer data under varying temperature boundary conditions, cylinder dimensions, and structural parameters such as the number and specifications of built-in fins. Therefore, there is an urgent need to develop a controllable and visual liquid-solid phase change experimental device to obtain quantitative heat transfer characteristic data, thereby providing solid data support and a theoretical basis for optimizing phase change energy harvesting materials and structural design, and improving the performance of marine temperature difference energy harvesting devices. Summary of the Invention

[0004] In view of the problem in the prior art that the thermal conductivity of phase change materials lacks systematic experimental means, resulting in difficulty in quantifying heat transfer characteristics, the present invention provides an experimental device and experimental method for the phase change process of liquid-solid energy-harvesting materials.

[0005] The present invention is implemented as follows: an experimental device for the phase change process of liquid-solid energy-capturing materials, characterized in that it includes: a pressurizing system, a liquid level monitoring device, a phase change heat exchange cylinder and a radial dimension recording camera; the liquid level monitoring device is provided with a cylindrical sealed cavity filled with phase change material and a liquid level monitoring sensor; the pressurizing system is connected to the liquid level detection device and is used to pressurize and measure the pressure of the cylindrical sealed cavity; the phase change heat exchange cylinder includes a metal heat exchange tube, a central fluid replenishment column and an inner fin, the inner side of the metal heat exchange tube forms a sealed heat exchange cavity filled with phase change material, the central fluid replenishment column is arranged at the center of the sealed heat exchange cavity and the sealed heat exchange cavity is divided into an inner cylinder cavity and an outer ring cavity by a cylindrical insulation wall with a through hole, the inner cylinder cavity is connected to the cylindrical sealed cavity, and the outer ring cavity is provided with the radial inner fin; the phase change heat exchange cylinder is provided with a perspective sealing end cover, and the radial dimension recording camera captures radial phase change boundary image information of the phase change material.

[0006] In the above technical solution, preferably, the pressurization system includes an air pump, a pressure gauge, a four-way joint and a pressure reducing valve; the air pump is used to pressurize the cylindrical sealed cavity, the pressure gauge is used to display the pressurization data, and the pressure reducing valve is used to control the pressurization value.

[0007] In the above technical solution, preferably, the liquid level monitoring device includes a liquid level monitoring tube, an upper sealing end cover, a lower sealing end cover, and a liquid level float; the upper sealing end cover and the lower sealing end cover are respectively sealed and installed on the upper and lower ends of the liquid level monitoring tube, and the inner side of the liquid level monitoring tube forms the cylindrical sealing cavity, the liquid level float is arranged on the inner side of the cylindrical sealing cavity and is located on the liquid surface of the phase change material, and the liquid level detection sensor is arranged on the upper part of the cylindrical sealing cavity and monitors the position data of the liquid level float.

[0008] In the above technical solution, preferably, the liquid level detection tube is a transparent long cylindrical structure; and a supporting rod is connected between the upper sealing end cover and the lower sealing end cover.

[0009] In the above technical solution, preferably, the phase change heat exchange cylinder includes a top end cover, a bottom end cover and a fixed pull rod, the top end cover and the bottom end cover are sealed with the top and bottom ends of the metal heat exchange tube and the central fluid replenishment column respectively, and the fixed pull rod connects the top end cover and the bottom end cover.

[0010] In the above technical solution, preferably, the cylindrical inner wall of the metal heat exchange tube is evenly distributed with a plurality of slots circumferentially, and the metal heat exchange tube is connected to a plurality of the inner fins through the slots, and the inner fins are evenly distributed and arranged circumferentially at phase angles and installed inside the metal heat exchange tube.

[0011] In the above technical solution, preferably, the inner fin is a rectangular structure made of metal material.

[0012] In the above technical solution, preferably, circular through holes are evenly distributed on the cylindrical insulation wall of the central fluid infusion column.

[0013] The present invention proposes an experimental device for the phase change process of liquid-solid energy-harvesting materials, which has many advantages such as adjustable structure, comprehensive data acquisition, and accurate experimental results.

[0014] The device allows for the flexible insertion of internal fins of varying numbers and specifications based on experimental requirements, and can systematically evaluate the effect of the internal fin structure on the heat transfer performance of the phase change heat exchange cylinder, thereby providing an experimental basis for optimizing the internal structure of the energy capture device. At the same time, a radial dimension recording camera is installed on the top of the device, which can monitor and record the radial changes of the phase change material during the phase change process in real time, obtain the radius data of the liquid-solid two-phase interface, and then draw the phase change interface evolution curve, facilitating in-depth analysis of the spatial dynamic process of the phase change behavior. In addition, the device can also accurately reflect the volume changes of the phase change material during the solidification process, providing a direct quantitative basis for studying the volume expansion or contraction effects associated with liquid-solid phase changes.

[0015] In summary, the experimental device of the present invention excels in experimental design flexibility, phase change process visualization, and quantitative data acquisition, providing an important support platform for in-depth research and engineering applications of liquid-solid phase change energy harvesting technology in marine environments.

[0016] The second object of the present invention is to provide an experimental method based on the above-mentioned experimental device for the phase transition process of liquid-solid energy-harvesting materials, comprising the following steps:

[0017] S1. Use a graduated cylinder and electronic scale to fill the phase change material to be tested into the phase change heat exchange cylinder until it is full, and record the volume V0 and mass m of the phase change material filled into the phase change heat exchange cylinder. POM Then, the phase change material is filled into the liquid level detection device until it reaches half of the maximum liquid level;

[0018] S2. Before the test begins, place the phase change heat exchanger in a water tank simulating sea surface temperature (T0°C) to keep the phase change material in a liquid state.

[0019] S3 to carry out solidification test, pressurize the liquid level detection device through the pressurization system, when the set pressure value is reached, record the pressure value p1 and liquid level data h0 within the liquid level detection device;

[0020] S4. Lowering the water temperature in the tank from the simulated sea surface temperature (T0°C) to the simulated seabed temperature (T1°C);

[0021] S5. Record the phase change time t of the filled phase change material during the solidification process from the simulated sea surface water temperature (T0℃) to the simulated seabed water temperature (T1℃) 总, recording the liquid level data change Δh in the liquid level monitoring device every Δt1 time, and using the radial dimension recording camera to take an image every Δt2 to record the radial phase change process of the phase change material on the top of the phase change heating cylinder;

[0022] S6. Remove the phase change heat exchanger from the water tank and allow the phase change material to gradually melt to a liquid state at room temperature. Repeat the above test steps after reaching the initial state for the next test.

[0023] S7. Through mathematical conversion analysis of the recorded data, the volume change rate of the tested phase change material during the liquid-solid solidification phase change process is obtained. The volume change rate calculation formula is:

[0024]

[0025] The average heat transfer rate of the phase change heat exchange cylinder is obtained. The calculation formula of the average heat transfer rate of the phase change heat exchange cylinder is:

[0026]

[0027] in, is the specific heat capacity of the energy-capturing phase change material in liquid state;

[0028] T 相 is the phase change temperature of the phase change material;

[0029] L POM is the phase change latent heat of the phase change material;

[0030] is the specific heat capacity of the energy-harvesting phase change material in the solid state.

[0031] In the above technical solution, preferably, the method further includes S8. Grayscale processing is performed on the photos taken by the radial dimension recording camera at intervals of Δt2 in S5, the boundary between the solid and liquid states of the phase change material is marked, the radius R of the boundary is measured, and a curve is drawn showing the change of the solid-liquid interface of the phase change boundary over time, with the initial point being the boundary radius when the phase change material is entirely liquid and the end point being the boundary radius when the phase change material is entirely solid. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the overall structure of the experimental device in the present invention;

[0033] Figure 2 Schematic diagram of the structure of the pressurizing system of the present invention;

[0034] Figure 3 Schematic diagram of the structure of the liquid level detection device in the present invention;

[0035] Figure 4 Schematic diagram of the structure of the phase change heat exchanger in the present invention;

[0036] Figure 5 This is a top view of the installation of the inner fins in the present invention;

[0037] Figure 6a This is a schematic diagram of the working process of the test device in the present invention;

[0038] Figure 6b Schematic diagram of the solid-liquid interface at the phase change boundary of the phase change material in the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0040] To address the problem in existing technologies of phase change materials' thermal conductivity, which lacks systematic experimental methods and makes it difficult to quantify heat transfer characteristics, the present invention provides an experimental device and method for the phase change process of liquid-solid energy-harvesting materials. To further illustrate the structure of the present invention, a detailed description is provided below with reference to the accompanying drawings:

[0041] See also Figure 1 , an experimental device for the phase change process of liquid-solid energy-capturing materials, including a pressurizing system 1, a liquid level monitoring device 3, a phase change heating cylinder 6 and a radial dimension recording camera 4.

[0042] See also Figure 2 The pressurization system is connected to the liquid level detection device and is used to pressurize and measure the cylindrical sealed cavity. The pressurization system includes an air pump 101, a pressure gauge 102, a cross-connector 103, and a pressure reducing valve 104. The air pump is used to pressurize the cylindrical sealed cavity within the liquid level detection device, the pressure gauge is used to display the pressurization data, and the pressure reducing valve is used to control the pressurization value. Specifically, the cross-connector connects the air pump, pressure gauge 2, cross-connector, pressure reducing valve, and liquid level detection device.

[0043] See also Figure 3The liquid level detection device comprises a cylindrical sealed cavity filled with phase change material and a liquid level detection sensor. Specifically, the liquid level detection device includes a liquid level detection tube 303, an upper sealed end cap 301, a lower sealed end cap 309, a liquid level float 304, a support rod 306, a sealing ring 307, an adapter 308, and a sealing plug 310. The upper and lower sealed end caps are sealedly mounted on the upper and lower ends of the liquid level monitoring tube, respectively. The inner side of the liquid level monitoring tube forms a cylindrical sealed cavity. The liquid level float is located within the cylindrical sealed cavity and floats on the liquid surface 305. The liquid level monitoring sensor is located above the cylindrical sealed cavity and monitors the position of the liquid level float. In this embodiment, the liquid level monitoring sensor uses a laser position sensor, which illuminates the liquid level float to measure the distance from the laser position sensor to the liquid level float. The liquid level detection tube is a transparent long cylindrical structure, which facilitates observation of liquid level changes during phase change from the outside. Its inner wall radius is r3. The support rod is connected between the upper sealing end cover and the lower sealing end cover, and the support rod is connected to the upper sealing end cover and the lower sealing end cover respectively through the support rod hole. Under the tightening action of the support rod, the upper sealing end cover and the lower sealing end cover are respectively fitted with the two ends of the liquid level detection tube.

[0044] See also Figure 4 The phase-change heat exchange tube includes a top end cap 601, a central fluid-infusion column 602, inner fins 603, a metal heat exchange tube 604, a bottom end cap 607, a sealing ring 307, a fixing rod 605, a fixing nut 606, an adapter 308, and a sealing plug 310. A sealed heat exchange chamber filled with phase-change material is formed inside the metal heat exchange tube. The central fluid-infusion column is located at the center of the sealed heat exchange chamber, which is divided into an inner cylindrical chamber and an outer annular chamber by a cylindrical insulation wall with through holes. The inner cylindrical chamber communicates with the cylindrical sealing chamber, and the outer annular chamber is equipped with radial inner fins.

[0045] See also Figure 5 The cylindrical inner wall of the metal heat exchange tube is evenly distributed with several slots along the circumference. The metal heat exchange tube is connected to several inner fins through the slots. The inner fins are evenly distributed and arranged circumferentially at phase angles and installed inside the metal heat exchange tube. The radius of the metal heat exchange tube is r1. The inner fins are rectangular structures made of metal material, which can enhance the heat transfer area and thermal conductivity of the phase change heat exchange tube. The cylindrical insulation wall of the central fluid replenishment column is evenly distributed with circular through holes. The outer radius of the hot wall of the central fluid replenishment column is r2. The central fluid replenishment column is made of insulation material, forming an adiabatic boundary on the outer diameter of the central fluid replenishment column, making the experimental data more accurate.

[0046] The phase-change heating element is equipped with a transparent sealed end cap, and a radial dimension recording camera captures image information of the radial phase change boundary of the phase-change material. Specifically, in this embodiment, the top and bottom end caps of the phase-change heating element are made of a transparent material, which is heat-resistant and highly transparent, facilitating the use of the radial dimension recording camera to capture the radial phase change process of the phase-change material from the top of the phase-change heating element. The adapter at the top of the phase-change heating element is connected to the adapter at the bottom of the liquid level detection device via a fluid guide hose.

[0047] The phase-change heat exchange cylinder includes a top end cap, a bottom end cap, and a fixed rod. The top and bottom end caps are sealed to the top and bottom ends of the metal heat exchange tube and the central fluid injection column, respectively. The fixed rod connects the top and bottom end caps. The fixed rods are connected to the top and bottom end caps through fixed rod holes. With the tightening action of the fixed rods, the top and bottom end caps are respectively attached to the ends of the metal heat exchange tube.

[0048] The present invention can be used to conduct liquid-solid solidification experiments based on the liquid-solid phase change process experimental device. Please refer to Figure 6a and Figure 6b , the specific test steps include:

[0049] S1. Complete the integrated installation of the liquid level monitoring device and the phase change heat exchange cylinder respectively, fill the metal heat exchange tube with the phase change material to be tested using a measuring cylinder and an electronic scale until it is full, and record the volume V0 and mass m of the phase change material filled into the phase change heat exchange cylinder. POM , connect the liquid level monitoring device through one end of the diversion hose, and then fill the phase change material into the liquid level detection device until it reaches half of the maximum liquid level, that is, half of the capacity of the cylindrical sealing cavity, to complete the filling of the phase change material and ensure that there are no bubbles in the device.

[0050] S2. Before the test begins, place the phase change heat exchanger into a water tank simulating sea surface temperature (T0°C) to keep the phase change material 305 in a liquid state, thus completing the preliminary preparations for the test.

[0051] S3. When conducting the solidification test, the liquid level detection device is pressurized by the air pump. When the pressure value set by the pressure reducing valve is reached, the pressure value p1 of the barometer and the data h0 output by the laser position sensor are recorded simultaneously.

[0052] S4. Gradually lower the water temperature in the tank from the simulated sea surface temperature (T0°C) to the simulated seabed temperature (T1°C).

[0053] S5. Record the phase change time t of the filled phase change material during the solidification process from the simulated sea surface water temperature (T0℃) to the simulated seabed water temperature (T1℃) 总, record the data change Δh output by the laser position sensor every Δt1 time, and use the radial dimension recording camera to take a photo every Δt2 to record the radial phase change process of the phase change material on the top of the phase change heating cylinder.

[0054] S6. Remove the phase change heat exchanger from the water tank and allow the phase change material to gradually melt to a liquid state at room temperature. Repeat the above test steps after reaching the initial state for the next test.

[0055] S7. Through mathematical conversion analysis of the recorded data, the volume change rate of the tested phase change material during the liquid-solid solidification phase change process is obtained. The volume change rate calculation formula is:

[0056]

[0057] The average heat transfer rate of the phase change heat exchange cylinder is obtained. The calculation formula for the average heat transfer rate of the phase change heat exchange cylinder is:

[0058]

[0059] in, Specific heat capacity of energy-harvesting phase change material in liquid state, T 相 is the phase change temperature of the phase change material, L POM is the phase change latent heat of the phase change material, Specific heat capacity of energy-harvesting phase change materials in the solid state.

[0060] S8. Grayscale the photographs taken by the radial dimension recording camera at intervals of Δt2 in S5, mark the boundary between the solid and liquid phase change materials, and measure the radius R of the boundary. Draw a curve that starts at the boundary radius when the phase change material is entirely liquid (i.e., the inner wall radius r1 of the metal heat exchange tube) and ends at the boundary radius when the phase change material is entirely solid (i.e., the outer wall radius r2 of the central fluid replenishment column), showing the change in the solid-liquid interface at the phase change boundary over time.

[0061] By calculating the average heat transfer rate and volume change rate of the phase change material, the performance of the material in thermal energy conversion and volume response during the liquid-solid phase change process can be comprehensively evaluated. The average heat transfer rate reflects the heat transfer capacity of the phase change material under a specific temperature difference drive. It is an important indicator to measure its energy capture efficiency and thermal response speed. It can be used to compare the heat transfer performance of different materials and different structural parameters (such as the number of fins, fin arrangement, and barrel diameter), and provide a quantitative basis for the material selection and structural design of marine temperature difference energy capture devices. The volume change rate reveals the volume contraction or expansion characteristics of the material caused by the density change during the phase change process. This data is of great significance for the subsequent device sealing design, energy release mechanism design, and buoyancy control. The combination of the two will help to achieve an accurate evaluation of the comprehensive performance of liquid-solid energy capture materials and promote the development and application of efficient, safe, and structurally optimized marine underwater energy capture devices.

[0062] The curve of the solid-liquid interface change reflects the dynamic evolution process of the solid region advancing to the liquid region (or reverse solidification) during the phase change process, and is one of the important means to reveal the phase change heat transfer mechanism. Through this curve, the position change of the phase change boundary at different time points can be visually observed, and the propagation speed and path of heat conduction inside the phase change material can be quantitatively analyzed. This data helps to understand the actual action area of ​​fin-enhanced heat transfer and its influence on the boundary advancement speed, and can also infer the distribution characteristics of local heat transfer intensity. The slope and morphological changes of the curve can be used to identify key thermal characteristics such as whether the phase change is uniform and whether the phase change rate is stable, providing a theoretical basis for optimizing fin design, adjusting heat source layout, and improving the thermal efficiency of the heat exchange tube structure. Therefore, the solid-liquid interface change curve not only reveals the dynamic behavior of heat migration inside the material, but also provides important support for the design of efficient and controllable ocean temperature difference energy capture devices.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An experimental device for the phase transition process of liquid-solid energy-harvesting materials, characterized by: It includes a pressurizing system, a liquid level monitoring device, a phase change heat exchange cylinder and a radial dimension recording camera; the liquid level monitoring device is provided with a cylindrical sealed cavity filled with phase change material and a liquid level monitoring sensor; the pressurizing system is connected to the liquid level detection device and is used to pressurize and measure the pressure of the cylindrical sealed cavity; the phase change heat exchange cylinder includes a metal heat exchange tube, a central fluid replenishment column and an inner fin, the inner side of the metal heat exchange tube forms a sealed heat exchange cavity filled with phase change material, the central fluid replenishment column is arranged at the center of the sealed heat exchange cavity and the sealed heat exchange cavity is divided into an inner cylinder cavity and an outer ring cavity by a cylindrical insulation wall with a through hole, the inner cylinder cavity is connected to the cylindrical sealed cavity, and the outer ring cavity is provided with the radial inner fin; the phase change heat exchange cylinder is provided with a perspective sealing end cover, and the radial dimension recording camera captures radial phase change boundary image information of the phase change material.

2. The experimental device for liquid-solid energy-harvesting material phase transition process according to claim 1, characterized in that: The pressurization system includes an air pump, a pressure gauge, a four-way joint and a pressure reducing valve; the air pump is used to pressurize the cylindrical sealed cavity, the pressure gauge is used to display the pressurization data, and the pressure reducing valve is used to control the pressurization value.

3. The experimental device for liquid-solid energy-harvesting material phase transition process according to claim 1, characterized in that: The liquid level monitoring device includes a liquid level monitoring tube, an upper sealed end cover, a lower sealed end cover, and a liquid level float; the upper sealed end cover and the lower sealed end cover are respectively sealed and installed on the upper and lower ends of the liquid level monitoring tube, the inner side of the liquid level monitoring tube forms the cylindrical sealed cavity, the liquid level float is arranged on the inner side of the cylindrical sealed cavity and is located on the liquid surface of the phase change material, and the liquid level detection sensor is arranged on the upper part of the cylindrical sealed cavity and monitors the position data of the liquid level float.

4. The experimental device for liquid-solid energy-harvesting material phase transition process according to claim 3, characterized in that: The liquid level detection tube is a perspective long cylindrical structure; a supporting pull rod is connected between the upper sealing end cover and the lower sealing end cover.

5. The experimental device for liquid-solid energy-harvesting material phase transition process according to claim 1, characterized in that: The phase change heat exchange cylinder includes a top end cover, a bottom end cover and a fixed pull rod. The top end cover and the bottom end cover are sealed with the top and bottom ends of the metal heat exchange tube and the central fluid replenishment column respectively. The fixed pull rod connects the top end cover and the bottom end cover.

6. The experimental device for liquid-solid energy-harvesting material phase transition process according to claim 5, characterized in that: The cylindrical inner wall of the metal heat exchange tube is uniformly distributed with a plurality of slots in the circumferential direction. The metal heat exchange tube is connected to a plurality of inner fins through the slots. The inner fins are uniformly distributed and arranged circumferentially at phase angles and installed inside the metal heat exchange tube.

7. The experimental device for liquid-solid energy-harvesting material phase transition process according to claim 6, characterized in that: The inner fin is a rectangular structure made of metal material.

8. The experimental device for liquid-solid energy-harvesting material phase transition process according to claim 6, characterized in that: Circular through holes are evenly distributed on the cylindrical heat-insulating wall of the central fluid-infusing column.

9. An experimental method based on the experimental device for phase transition of liquid-solid energy-harvesting materials according to any one of claims 1 to 8, comprising the following steps: S1. Use a graduated cylinder and electronic scale to fill the phase change material to be tested into the phase change heat exchange cylinder until it is full, and record the volume V0 and mass m of the phase change material filled into the phase change heat exchange cylinder. POM Then, the phase change material is filled into the liquid level detection device until it reaches half of the maximum liquid level; S2. Before the test begins, place the phase change heat exchanger in a water tank simulating sea surface temperature (T0°C) to keep the phase change material in a liquid state. S3 to carry out solidification test, pressurize the liquid level detection device through the pressurization system, when the set pressure value is reached, record the pressure value p1 and liquid level data h0 within the liquid level detection device; S4. Lowering the water temperature in the tank from the simulated sea surface temperature (T0°C) to the simulated seabed temperature (T1°C); S5. Record the phase change time t of the filled phase change material during the solidification process from the simulated sea surface water temperature (T0℃) to the simulated seabed water temperature (T1℃) 总 , recording the liquid level data change Δh in the liquid level monitoring device every Δt1 time, and using the radial dimension recording camera to take an image every Δt2 to record the radial phase change process of the phase change material on the top of the phase change heating cylinder; S6. Remove the phase change heat exchanger from the water tank and allow the phase change material to gradually melt to a liquid state at room temperature. Repeat the above test steps after reaching the initial state for the next test. S7. Through mathematical conversion analysis of the recorded data, the volume change rate of the tested phase change material during the liquid-solid solidification phase change process is obtained. The volume change rate calculation formula is: The average heat transfer rate of the phase change heat exchange cylinder is obtained. The calculation formula of the average heat transfer rate of the phase change heat exchange cylinder is: in, is the specific heat capacity of the energy-capturing phase change material in liquid state; T 相 is the phase change temperature of the phase change material; L POM is the phase change latent heat of the phase change material; is the specific heat capacity of the energy-harvesting phase change material in the solid state.

10. The experimental method according to claim 9, characterized in that include: S8. Perform grayscale processing on the photos taken by the radial dimension recording camera every Δt2 time in S5, mark the boundary line between the solid and liquid states of the phase change material, measure the radius R of the boundary line, and draw a curve with the initial point being the boundary line radius when the phase change material is all liquid and the end point being the boundary line radius when the phase change material is all solid, and the curve showing the change of the solid-liquid interface of the phase change boundary with time.

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