Method for multi-dimensional quantitative characterization of response speed of phase change energy storage composite material

Abstract

The invention relates to a method for multi-dimensional quantitative characterization of the response speed of a phase change energy storage composite material. The thermal response test is carried out by utilizing the difference of the thermal conductivity, the internal pore size and different thermal conduction channels of different phase change energy storage composite materials. The method comprises the following steps: carrying out surface treatment on the phase change energy storage composite material, smearing silicone grease, pasting a thermocouple, fixing the heating rate or power of a heating table, recording the temperature and time of different time periods, extracting data, drawing, and analyzing the image to obtain the response temperature and response time of different phase change energy storage composite materials. Therefore, the novel response speed testing method has a great application prospect on the phase change energy storage material.

Description

Technical Field

[0001] The present invention relates to the field of composite material characterization, and in particular to a method for multi-dimensional quantitative characterization of the response speed of a phase-change energy storage composite material. Background Art

[0002] With the rapid development of industry, energy consumption and population growth, efficient energy storage and management have attracted increasing attention. Thermal energy storage (TES) using phase change materials (PCMs) has become a promising technology to address the mismatch between thermal energy supply and demand. Most organic PCMs have low thermal conductivity (λ PCM <0.5W m -1 K -1 ), poor thermal conductivity, which makes the PCMs have poor response ability and slow heat absorption, thus affecting the heat storage efficiency.

[0003] Therefore, the combination of PCMs and carbon materials is needed to improve its thermal conductivity. There are three main forms, namely, disordered dispersion of carbon materials into PCMs, combination of disordered continuous three-dimensional (3D) carbon frameworks with PCMs, and combination of arranged carbon frameworks with PCMs. When used for thermal energy storage, the first form is characterized by volumetric energy storage, in which only a very small amount of graphite particles (or doped graphite particles) are dispersed into the PCM as a "heat transfer bridge". Although this method has the advantage of negligible reduction in energy storage capacity, it requires the PCM to have good transparency and parallel and fixed lighting. It should also be pointed out that the composite system still has inefficient heat transfer, making it challenging to quickly extract the stored heat. In contrast, the latter two forms will generate external heat into the interior of the composite block through the formed heat transfer network. However, the response speed of phase change energy storage composites is still difficult to characterize, and can only be inferred by the thermal conductivity of the phase change energy storage composites, which is completely inaccurate.

[0004] At the same time, during the phase change energy storage process, due to the different sizes of PCMs in the phase change energy storage composite materials, the melting time of PCMs inside the skeleton is difficult to estimate. Therefore, it is very necessary to invent a method to accurately determine the response time of PCMs in phase change energy storage materials. Summary of the invention

[0005] To solve the above problems, we adopt:

[0006] 1) Pretreatment of phase change energy storage composite materials: In order to improve the accuracy of the test, the phase change energy storage composite materials will be surface treated with 100-1000 mesh sandpaper to ensure good contact of the phase change energy storage composite materials;

[0007] 2) Preparation of phase change energy storage composite material samples: using a cutting machine, cut the phase change energy storage composite material into cubes with a length, width and height of 1-50 mm respectively;

[0008] 3) Test of fast response phase change energy storage composite materials: Apply silicone grease to the bottom of the phase change energy storage composite material and place it on the heating platform. Heat it to 120°C at a heating rate of 1-20°C / min, and place a thermocouple at the center of the top of the phase change energy storage composite material to collect temperature, time, and heating power data;

[0009] 4) Analysis of test results: The data obtained in 3) are plotted as a power-temperature data graph, and the data graph is differentiated. The first peak of the differential curve is taken as the reference point, and a tangent line is taken for this point of the power-temperature data graph. The point where the tangent line intersects with the baseline is the initial rapid melting temperature (T1) and time (t1). Then, the last peak of the differential curve is taken as the reference point, and a tangent line is taken for this point of the power-temperature data graph. The point where the tangent line intersects with the baseline is the temperature (T2) and time (t2) of complete melting. t2-t1 is the response time of the material, and T2-T1 is the response temperature.

[0010] Preferably, the mesh size of the sandpaper used for the surface treatment in step 1) is preferably 500-800 mesh;

[0011] Preferably, the length, width and height of the sample in step 2) are optimally 20-40 mm;

[0012] Preferably, the heating rate in step 3) is optimally 5-15°C / min.

[0013] The beneficial effects of the present invention are: 1. This method can accurately determine the response speed of phase-change energy storage composite materials, understand the performance of different phase-change energy storage composite materials, and make the most accurate connection between our needs and performance. 2. This method allows us to establish a basic material information database for different types of phase-change energy storage composite materials, which can provide a direction for the research of phase-change energy storage composite materials and also enable us to use phase-change energy storage composite materials that can quickly and efficiently select responses. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is an analysis of the power-temperature data graph. DETAILED DESCRIPTION

[0015] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0016] Embodiment 1:

[0017] The response speed characterization method of the phase change energy storage composite material described in this embodiment is specifically carried out according to the following steps:

[0018] 1) Pretreatment of phase change energy storage composite materials: In order to improve the accuracy of the test, the phase change energy storage composite materials will be surface treated with 300-grit sandpaper to ensure good contact of the phase change energy storage composite materials;

[0019] 2) Preparation of phase change energy storage composite material samples: Use a cutting machine to cut the phase change energy storage composite material into cubes with a length, width and height of 20 mm respectively;

[0020] 3) Test of fast response phase change energy storage composite materials: Apply silicone grease to the bottom of the phase change energy storage composite material and place it on the heating platform. Heat it to 120°C at a heating rate of 3°C / min, and place a thermocouple at the center of the top of the phase change energy storage composite material to collect temperature, time, and heating power data;

[0021] 4) Analysis of test results: The data obtained in 3) are used to make a power-temperature data graph, and the data graph is derived. The first peak of the differential curve is used as the reference point, and a tangent is taken for this point of the power-temperature data graph. The point where the tangent intersects with the baseline is the initial rapid melting temperature (T1=62.03°C) and time (t1=20.1min). Then, the last peak of the differential curve is used as the reference point, and a tangent is taken for this point of the power-temperature data graph. The point where the tangent intersects with the baseline is the complete melting temperature (T2=67.73°C) and time (t2=24.5min). t2-t1=4.4min is the response time of the material, and T2-T1=5.70°C is the response temperature.

[0022] The length, width and height of the phase-change energy storage composite material prepared in Example 1 are 20 mm.

[0023] The response time of the phase-change energy storage composite material tested in this embodiment is 4.4 minutes, and the response temperature is 5.70° C. The accuracy of the thermal conductivity test and calculation of the conventional phase-change energy storage composite material is improved by 30%.

[0024] Embodiment 2:

[0025] In the response speed characterization method of the phase change energy storage composite material described in this embodiment, only the mesh size of the sandpaper in step 1) is changed to 500 mesh.

[0026] The length, width and height of the phase-change energy storage composite material prepared in Example 2 are 20 mm.

[0027] The response time of the phase change energy storage composite material tested in this embodiment is 4.2 minutes, and the response temperature is 5.10°C. The accuracy of the thermal conductivity test and calculation of the conventional phase change energy storage composite material is improved by 34%. This is because increasing the mesh of the sandpaper can make the surface of the phase change energy storage composite material smoother, the contact surface with the heating platform is larger, and the heat transfer is faster and more accurate.

[0028] Embodiment three:

[0029] In the response speed characterization method of the phase-change energy storage composite material described in this embodiment, only the heating rate in step 3) is changed to 5° C. / min.

[0030] The length, width and height of the phase-change energy storage composite material prepared in Example 2 are 20 mm.

[0031] The response time of the phase change energy storage composite material tested in this embodiment is 3.9 minutes, and the response temperature is 4.7°C. The accuracy of the thermal conductivity test and calculation of the traditional phase change energy storage composite material is improved by 38%. The accuracy of the test is improved because the heating rate increases. When the traditional method is used, the temperature lag phenomenon will occur. Therefore, the accuracy of the traditional method decreases. However, through this test method, during the heating process of the phase change energy storage composite material, it will not be affected by the heating rate within a certain range of heating rate.

[0032] Comparative Example 2:

[0033] The response speed characterization method of the phase-change energy storage composite material described in this comparative example only changes the heating rate in step 3) to 35°C / min.

[0034] The length, width and height of the phase-change energy storage composite material prepared in this comparative example 2 are 20 mm.

[0035] The response time of the phase change energy storage composite material tested in this comparative example is 5.7 minutes, and the response temperature is 6.8°C. Compared with the traditional phase change energy storage composite material, the thermal conductivity test and the accuracy of the calculation are reduced by 22%. This is because the temperature lag caused by the excessively fast heating rate reduces the test accuracy.

[0036] Comparative Example 2:

[0037] The response speed characterization method of the phase-change energy storage composite material described in this comparative example only changes the heating rate in step 3) to 35°C / min.

[0038] The length, width and height of the phase-change energy storage composite material prepared in this comparative example 2 are 20 mm.

[0039] The response time of the phase change energy storage composite material tested in this comparative example is 5.7 minutes, and the response temperature is 6.8°C. Compared with the traditional phase change energy storage composite material, the thermal conductivity test and the accuracy of the calculation are reduced by 22%. This is because the temperature lag caused by the excessively fast heating rate reduces the test accuracy.

[0040] Comparative Example 3:

[0041] In the method for characterizing the response speed of the phase-change energy storage composite material described in this comparative example, only the size of the phase-change energy storage composite material in step 2) is changed to 100 mm.

[0042] The length, width and height of the phase change energy storage composite material prepared in this comparative example 3 are 100 mm.

[0043] The response time of the phase change energy storage composite material tested in this comparative example is 5.3 minutes, and the response temperature is 5.9°C. Compared with the traditional phase change energy storage composite material test thermal conductivity and the accuracy of calculation, it is 19% lower. This is because the sample size is too large, which leads to the obstruction of heat transfer of the phase change energy storage composite material during the test, thereby reducing the accuracy of the test.

Claims

1. A method for multi-dimensional quantitative characterization of the response speed of a phase change energy storage composite material, characterized in that: The following steps are involved: 1) Pretreatment of phase change energy storage composite materials: In order to improve the accuracy of the test, the phase change energy storage composite materials will be surface treated with 100-1000 mesh sandpaper to ensure good contact of the phase change energy storage composite materials; 2) Preparation of phase change energy storage composite material samples: using a cutting machine, cut the phase change energy storage composite material into cubes with a length, width and height of 1-50 mm respectively; 3) Test of fast response phase change energy storage composite materials: Apply silicone grease to the bottom of the phase change energy storage composite material and place it on the heating platform. Heat it to 120°C at a heating rate of 1-20°C / min, and place a thermocouple at the center of the top of the phase change energy storage composite material to collect temperature, time, and heating power data; 4) Analysis of test results: Make a power-temperature data graph with the data obtained in 3), and differentiate the data graph. Take the first peak of the differential curve as the reference point, take a tangent to this point of the power-temperature data graph, and the point where the tangent intersects with the baseline is the initial rapid melting temperature (T1) and time (t1). Then, take the last peak of the differential curve as the reference point, take a tangent to this point of the power-temperature data graph, and the point where the tangent intersects with the baseline is the complete melting temperature (T2) and time (t2). t2-t1 is the response time of the material, and T2-T1 is the response temperature.

2. The method for multi-dimensional quantitative characterization of the response speed of a phase change energy storage composite material according to claim 1, characterized in that: The mesh number of the sandpaper described in step 1) is 100-1000 meshes.

3. The method for multi-dimensional quantitative characterization of the response speed of a phase change energy storage composite material according to claim 1, characterized in that: In step 2), the sample size of the phase change energy storage composite material is 1-50 mm.

4. The method for multi-dimensional quantitative characterization of the response speed of a phase change energy storage composite material according to claim 1, characterized in that: The heating rate in step 3) is 1-20°C / min.

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