Heat transfer and energy storage composite material and preparation method thereof

Abstract

The invention discloses a heat transfer and energy storage composite material and a preparation method thereof, and belongs to the field of heat transfer and energy storage materials, and the preparation method comprises the following steps: carrying out first calcination on Ca (NO3) 2.4 H2O to obtain Ca (NO3) 2 in a molten state; and adding KNO3, LiNO3 and nano SiO2 into Ca (NO3) 2 in a molten state, uniformly stirring, carrying out secondary calcination, cooling and drying to obtain the heat transfer and energy storage composite material. The composite material has high specific heat capacity, wide use temperature range and high heat transfer performance. Nano particle silicon dioxide is used for modification on the basis of ternary nitrate, the specific heat capacity and the heat conductivity of the ternary nitrate are effectively improved, and long-time storage of heat of compressed air energy storage can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of heat transfer and energy storage, and particularly relates to a heat transfer and energy storage composite material and a preparation method thereof. Background Art

[0002] With the acceleration of industrialization, the demand for energy in industrial production has increased dramatically. The rapid development of industries such as manufacturing and construction has led to a continuous increase in energy consumption.

[0003] Energy storage systems can store excess electricity and reduce energy waste. This is especially true for intermittent energy sources like wind and solar. Energy storage systems can balance the time difference between power generation and consumption, minimizing energy losses caused by supply-demand mismatches. Energy storage technology offers significant advantages in improving energy efficiency, enhancing grid stability, supporting the integration of renewable energy, and reducing energy costs. It holds broad application prospects and is a key technology for achieving energy transformation.

[0004] Phase-change energy storage materials (PCES) store energy through latent heat, absorbing and releasing large amounts of heat during phase changes. Their energy storage density is far higher than traditional sensible heat storage methods. The heat storage process of PCES is reversible, and they have a long lifespan, enabling stable operation over extended periods. Their extended heat storage cycle makes them suitable for long-term thermal energy storage.

[0005] Molten salt phase change heat storage utilizes the phase change process of molten salt between liquid and solid to absorb and release large amounts of heat. It has a high energy storage density and is suitable for large-scale heat storage. Compared with traditional working fluids, molten salt has a series of advantages, such as a wide operating temperature range, high heat transfer performance, low operating pressure and low price. Among them, nitrate is an excellent heat transfer and heat storage medium with good stability at high temperatures, low vapor pressure, low viscosity, low corrosiveness, and high heat storage density. However, the specific heat capacity and other properties of existing energy storage materials need to be further improved. Therefore, there is an urgent need to develop a new type of high specific heat capacity heat transfer material to improve its application performance in the field of heat storage and better meet the requirements of compressed air energy storage. Summary of the Invention

[0006] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0007] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0008] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a heat transfer and energy storage composite material.

[0009] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0010] The Ca(NO3)2·4H2O is calcined for the first time to obtain molten Ca(NO3)2;

[0011] KNO3, LiNO3 and nano-SiO2 are added to molten Ca(NO3)2 and stirred evenly, and then calcined for the second time, cooled and dried to obtain a heat transfer and energy storage composite material.

[0012] As a preferred solution of the method for preparing the heat transfer and energy storage composite material of the present invention, the mass ratio of KNO3, LiNO3, Ca(NO3)2, and nano-SiO2 is 50-85:0-25:10-50:0-10.

[0013] As a preferred solution of the method for preparing the heat transfer and energy storage composite material of the present invention, the mass ratio of KNO3, LiNO3, Ca(NO3)2, and nano-SiO2 is 66.9:13.1:19:1.

[0014] As a preferred embodiment of the method for preparing the heat transfer and energy storage composite material of the present invention, the temperature of the first calcination is 180-220°C.

[0015] As a preferred solution of the method for preparing the heat transfer and energy storage composite material of the present invention, the time of the first calcination is 1 to 2 hours.

[0016] As a preferred embodiment of the method for preparing the heat transfer and energy storage composite material of the present invention, the temperature of the second calcination is 200-220°C.

[0017] As a preferred solution of the method for preparing the heat transfer and energy storage composite material of the present invention, the second calcination time is 1 to 2 hours.

[0018] As a preferred embodiment of the method for preparing the heat transfer and energy storage composite material of the present invention, the first calcination and the second calcination are both carried out in air.

[0019] Another object of the present invention is to overcome the deficiencies in the prior art and provide a heat transfer and energy storage composite material prepared by a method for preparing the heat transfer and energy storage composite material.

[0020] As a preferred embodiment of the heat transfer and energy storage composite material of the present invention, it has the following characteristics:

[0021] The average specific heat capacity in the range of 200-400°C tested by the stepscan method is 1.40-1.70 J / g·°C, and the thermal conductivity measured by the Hot Disk thermal conductivity meter is 0.55-0.75 W / m·K.

[0022] Beneficial effects of the present invention:

[0023] The present invention adds nanoparticles to the inorganic salt mixture, which effectively improves the specific heat capacity and thermal conductivity of the material, expands the operating temperature range, and can achieve long-term storage of heat for compressed air energy storage at low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0025] Figure 1 This is a flow chart of preparing a heat transfer and energy storage composite material according to Example 1 of the present invention.

[0026] Figure 2 This is a curve showing how the mass of the heat transfer and energy storage composite material prepared in Example 1 of the present invention changes with temperature.

[0027] Figure 3 The DSC curves of the energy storage materials prepared in Example 1 and Comparative Example 1 of the present invention are shown.

[0028] Figure 4 Graph showing the change in specific heat capacity of the energy storage materials prepared in Example 1 and Comparative Example 1 of the present invention within the range of 100-400°C.

[0029] Figure 5 This is a graph showing the viscosity change of the energy storage materials prepared in Example 1 and Comparative Example 1 of the present invention within the range of 100-500°C. DETAILED DESCRIPTION

[0030] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0032] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0033] The Ca(NO3)2·4H2O, KNO3 and LiNO3 used in the present invention were all analytically pure and purchased from Sinopharm Chemical Reagent Co., Ltd.

[0034] The nano-SiO2 used in the present invention was analytically pure and purchased from Glatt Technology Co., Ltd.

[0035] The phase transition point and phase transition enthalpy of the heat transfer and energy storage material in the present invention are tested by differential scanning calorimetry (model PE-DSC8000), and the thermal properties and thermal behavior of the material are studied by measuring the heat difference between the sample and the reference.

[0036] The heat transfer and energy storage material of the present invention is tested for its specific heat capacity within the range of 200 to 400° C. using the stepscan method.

[0037] The thermal conductivity of the heat transfer energy storage material in the present invention is measured at room temperature using a HotDisk thermal conductivity meter.

[0038] The viscosity of the heat transfer and energy storage material in the present invention is tested using a DV2T-LV Brookfield viscosity meter. The measurement is performed in the range of 150°C to 450°C with a step size of 10°C. The sample is heated to a molten state and kept warm for 1 hour after reaching the corresponding temperature. Then, the speed is controlled to measure the viscosity.

[0039] The heat transfer and energy storage material in the present invention is subjected to weight loss analysis using a thermogravimetric analyzer, and the test is performed using a heating rate of 5°C / min. A heating upper limit of 500°C is first set, and the temperature is further increased. If the weight decreases, it means that the molten salt has decomposed.

[0040] Example 1

[0041] This embodiment provides a method for preparing a heat transfer and energy storage composite material, specifically:

[0042] (1) Calcinate Ca(NO3)2·4H2O in air at 220°C for 2 h to obtain molten Ca(NO3)2;

[0043] (2) KNO3, LiNO3, and nano-SiO2 were added to the molten Ca(NO3)2 and stirred evenly, wherein the mass ratio of KNO3, LiNO3, Ca(NO3)2, and nano-SiO2 was 63.4:8.6:27:1. The mixture was calcined at 220°C in air for 2 h, taken out, cooled, and dried to obtain a heat transfer and energy storage composite material.

[0044] Figure 1 This is a flow chart for preparing the heat transfer and energy storage composite material of Example 1.

[0045] The decomposition temperature of the heat transfer and energy storage composite material prepared in Example 1 was tested, and the results were as follows: Figure 2 shown.

[0046] from Figure 2 It can be seen that the molten salt decomposition phenomenon of the heat transfer and energy storage composite material occurs at about 520°C, indicating that it can meet the use requirements within the temperature range of 400°C.

[0047] Comparative Example 1

[0048] The difference between this comparative example and Example 1 is that nano-SiO2 is not added, the mass ratio of KNO3, LiNO3, and Ca(NO3)2 is adjusted to 63.7:9:27.3, and the rest of the preparation process is the same as that of Example 1 to prepare the energy storage material of this comparative example.

[0049] The phase transition point, phase transition enthalpy, specific heat capacity in the range of 200-400°C and thermal conductivity of the energy storage materials prepared in Example 1 and Comparative Example 1 were tested. The results are shown in Table 1 and Figures 3-4 As shown. Among them, Figure 3 is the DSC curve diagram, Figure 4 This is a graph showing the change in specific heat capacity within the range of 100 to 400°C.

[0050] Table 1 Physical properties of different energy storage materials

[0051]

[0052]

[0053] According to Table 1 Figures 3-4 It can be seen that the specific heat capacity and thermal conductivity of the energy storage material prepared by adding nano-SiO2 are improved, and the phase change enthalpy is reduced.

[0054] The viscosity of the energy storage materials prepared in Example 1 and Comparative Example 1 was further tested, and the results were as follows: Figure 5 shown.

[0055] from Figure 5 It can be seen that the addition of nano-SiO2 significantly increases the kinematic viscosity of the material. The viscosity decreases with increasing temperature, and the downward trend slows down after 350°C. The final viscosity is still close to 20mPa·s.

[0056] Example 2

[0057] The difference between this embodiment and Example 1 is that the mass ratio of KNO3, LiNO3, Ca(NO3)2, and nano-SiO2 is adjusted to 66.9:13.1:19:1, and the rest of the preparation process is the same as that of Example 1 to prepare the heat transfer and energy storage composite material of this embodiment.

[0058] Comparative Example 2

[0059] The difference between this comparative example and Example 2 is that nano-SiO2 is not added, the mass ratio of KNO3, LiNO3, and Ca(NO3)2 is adjusted to 67.2:13.5:19.3, and the rest of the preparation process is the same as that of Example 2 to prepare the energy storage material of this comparative example.

[0060] The performance of the heat transfer and energy storage composite materials prepared in Example 2 and Comparative Example 2 was tested, and the results are shown in Table 2.

[0061] Table 2 Physical properties of different energy storage materials

[0062]

[0063] As can be seen from Table 2, compared with Example 1, the specific heat capacity and thermal conductivity of the energy storage material prepared in Example 2 are further improved. The specific heat capacity without adding nano-SiO2 is also lower.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 1 is that KNO3, LiNO3, and Ca(NO3)2 are first mixed and calcined to a molten state and then nano-SiO2 is added. The rest of the preparation process is the same as that of Example 1 to prepare the heat transfer and energy storage composite material of this comparative example.

[0066] Comparative Example 4

[0067] The difference between this comparative example and Example 1 is that KNO3 is first calcined to a molten state, and then nano-SiO2, LiNO3, and Ca(NO3)2 are added successively, stirred evenly, and calcined. The rest of the preparation process is the same as that of Example 1 to prepare the heat transfer and energy storage composite material of this comparative example.

[0068] Observation of the heat transfer and energy storage composite materials prepared in Comparative Examples 3 and 4 and testing their thermal conductivity revealed that the energy storage material prepared in Comparative Example 1 exhibited localized agglomeration, resulting in a thermal conductivity of 0.5000 W / m·K. The energy storage material prepared in Comparative Example 2 exhibited some nanoparticle aggregation on the surface of KNO3, resulting in a thermal conductivity of only 0.4856 W / m·K. The energy storage material prepared in Example 1 exhibited no agglomeration. This demonstrates that the thermal conductivity of the energy storage material can only be improved by adding nanoparticles to the molten state of Ca(NO3)2.

[0069] In summary, the present invention provides a thermal energy storage composite material and a preparation method thereof. By modifying calcium nitrate by adding nanoparticles to the molten state, the obtained composite material has a high specific heat capacity, a wide operating temperature range, and high heat transfer performance, and can achieve long-term storage of heat for compressed air energy storage.

[0070] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a heat transfer and energy storage composite material, characterized in that: include, The Ca(NO3)2·4H2O is calcined for the first time to obtain molten Ca(NO3)2; KNO3, LiNO3 and nano-SiO2 are added to molten Ca(NO3)2 and stirred evenly, and then calcined for the second time, cooled and dried to obtain a heat transfer and energy storage composite material.

2. The method for preparing the heat transfer and energy storage composite material according to claim 1, wherein: The mass ratio of KNO3, LiNO3, Ca(NO3)2 and nano-SiO2 is 50-85:0-25:10-50:0-10.

3. The method for preparing the heat transfer and energy storage composite material according to claim 2, wherein: The mass ratio of KNO3, LiNO3, Ca(NO3)2 and nano-SiO2 is 66.9:13.1:19:

1.

4. The method for preparing the heat transfer and energy storage composite material according to claim 1, wherein: The temperature of the first calcination is 180-220°C.

5. The method for preparing the heat transfer and energy storage composite material according to claim 4, wherein: The first calcination time is 1 to 2 hours.

6. The method for preparing the heat transfer and energy storage composite material according to claim 1, wherein: The temperature of the second calcination is 200-220°C.

7. The method for preparing the heat transfer and energy storage composite material according to claim 6, wherein: The second calcination time is 1 to 2 hours.

8. The method for preparing the heat transfer and energy storage composite material according to claim 1, wherein: The first calcination and the second calcination are both carried out in air.

9. The heat transfer and energy storage composite material prepared by the preparation method according to any one of claims 1 to 8.

10. The heat transfer and energy storage composite material according to claim 9, characterized in that: It has the following characteristics, The average specific heat capacity in the range of 200-400°C tested by the stepscan method is 1.40-1.70 J / g·°C, and the thermal conductivity measured by the Hot Disk thermal conductivity meter is 0.55-0.75 W / m·K.

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