Expanded graphite-hydrated salt composite phase change cold storage material, preparation method and application

Abstract

The invention relates to the technical field of composite phase change materials, in particular to an expanded graphite-hydrated salt composite phase change cold storage material, a preparation method and application, and the expanded graphite-hydrated salt composite phase change cold storage material at least comprises a hydrated salt crystal mixture, a phase change temperature regulator, a supercooling inhibitor, a phase separation inhibitor and expanded graphite; wherein the hydrated salt crystal mixture is used as a cold storage functional body; the phase change temperature regulator is used for controlling the phase change temperature of the composite phase change cold storage material so as to meet the requirements of different application scenes; the supercooling inhibitor cooperates with the hydrated salt crystal mixture, so that the supercooling degree is further reduced, and the cold storage performance is improved; the phase separation inhibitor inhibits phase separation of the hydrated salt crystal mixture, and cooperates with the expanded graphite to retain water molecules in the phase change material, so that the stability of the phase change material is enhanced, and the finally obtained phase change cold storage material has the advantages of appropriate phase change temperature, high phase change latent heat, small degree of supercooling, stable property, difficulty in phase separation, environmental friendliness and the like. The problems that an existing hydrated salt phase change cold storage material is large in supercooling degree and poor in stability are solved.

Description

Technical Field

[0001] The invention relates to the technical field of composite phase change materials, in particular to an expanded graphite-hydrated salt composite phase change cold storage material, a preparation method and application thereof. Background Art

[0002] Energy is a strategic element of economic and social development, and cold storage technology is a relatively important one in energy development, which has received more and more policy support and researchers' attention. Cold storage technology is a technology that can store a specific temperature environment for a long time, and is often used to maintain a low temperature environment for refrigerated food and medicine during transportation or storage. Cold storage technology is based on the principles of physics. It cools or freezes liquids or solids, stores them in sealed containers, and releases cold energy when needed to keep the transported or stored goods in their original low temperature state. Specifically, it uses water, ice or eutectic salt as a medium, uses the nighttime grid valley electricity (when electricity prices are low) for refrigeration, stores the obtained low-temperature water or ice for cold storage, and uses the stored low-temperature water or ice as a cold source during peak electricity consumption (when electricity prices are high). Among cold storage technologies, phase change cold storage technology has become a research focus due to its high energy storage density, simple device, low cost, and small size. It has a relatively broad development prospect in the fields of cold chain transportation, building cooling, refrigerator energy saving, and air conditioning temperature control.

[0003] Phase change cold storage technology is based on the phase change principle of matter, that is, when a substance changes between solid and liquid, it absorbs or releases a large amount of heat. The latent heat change in this phase change process is used to store and release cold. Phase change material (PCM) is the core of phase change cold storage technology. It undergoes phase change at a specific temperature to absorb or release cold. Among them, hydrated salt phase change cold storage materials use the characteristics of inorganic hydrated salts undergoing phase change within a specific temperature range to store and release heat or cold. That is, when the ambient temperature drops, the hydrated salt absorbs cold and undergoes phase change to store cold energy; when the cold needs to be released, the hydrated salt undergoes a reverse phase change and releases cold; hydrated salt phase change cold storage materials are widely used in industrial waste heat recovery, food preservation, air conditioning cold storage, building cooling and cold chain transportation due to their high latent heat of phase change, small volume change during phase change, and low cost. However, hydrated salt phase change energy storage materials are prone to large supercooling problems during the phase change process, and after multiple phase change cycles, hydrated salt phase change energy storage materials may experience phase separation, which limits the application of hydrated salt phase change energy storage materials. Summary of the invention

[0004] In view of the problems of large supercooling and poor stability of hydrated salt phase change cold storage materials in the prior art, the present invention provides an expanded graphite-hydrated salt composite phase change cold storage material, a preparation method and application thereof.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides an expanded graphite-hydrated salt composite phase-change cold storage material, which at least comprises a hydrated salt crystal mixture, a phase-change temperature regulator, a supercooling inhibitor, a phase separation inhibitor and expanded graphite; The hydrated salt crystal mixture includes several kinds of hydrated salt crystals, and the unit cell structure parameters of the hydrated salt crystals differ by less than 15%; In terms of mass percentage, after the hydrated salt crystal mixture is mixed with the phase change temperature regulator, the proportion of the phase change temperature regulator is 10% to 25%; after the hydrated salt crystal mixture is mixed with the phase change temperature regulator and the supercooling inhibitor, the proportion of the supercooling inhibitor is 1% to 4%; after the hydrated salt crystal mixture is mixed with the phase change temperature regulator, the supercooling inhibitor and the phase separation inhibitor, the proportion of the phase separation inhibitor is 1% to 4%; after the hydrated salt crystal mixture is mixed with the phase change temperature regulator, the supercooling inhibitor, the phase separation inhibitor and the expanded graphite, the proportion of the expanded graphite is 3% to 9%.

[0006] Optionally, the hydrated salt crystal mixture includes disodium hydrogen phosphate dodecahydrate and sodium sulfate decahydrate.

[0007] Optionally, in the hydrated salt crystal mixture, by mass percentage, disodium hydrogen phosphate dodecahydrate accounts for 55% to 65%, and sodium sulfate decahydrate accounts for 35% to 45%.

[0008] Optionally, the phase change temperature regulator is ammonium chloride.

[0009] Optionally, the supercooling inhibitor is borax.

[0010] Optionally, the phase separation inhibitor is sodium carboxymethyl cellulose.

[0011] The method for preparing the above-mentioned expanded graphite-hydrated salt composite phase change cold storage material comprises: Melting the hydrated salt crystal mixture into a molten mixture A; Mixing the molten mixture A with the phase change temperature regulator to melt into the molten mixture B; Mixing the molten mixture B with the supercooling inhibitor to melt into a molten mixture C; Mixing the molten mixture C with a phase separation inhibitor and melting them into a molten mixture D; The molten mixture D is mixed evenly with expanded graphite to obtain an expanded graphite-hydrated salt composite phase change cold storage material.

[0012] Optionally, the melting temperatures of the melt-to-molten mixture A, the melt-to-molten mixture B, the melt-to-molten mixture C and the melt-to-molten mixture D are all 50°C to 70°C.

[0013] An expanded graphite-hydrated salt composite phase-change cold storage material prepared by the method, wherein the phase change temperature of the expanded graphite-hydrated salt composite phase-change cold storage material is 2°C to 10°C.

[0014] Such as the application of the expanded graphite-hydrated salt composite phase change cold storage material in cold storage technology.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses an expanded graphite-hydrated salt composite phase change cold storage material, which at least comprises a hydrated salt crystal mixture, a phase change temperature regulator, a supercooling inhibitor, a phase separation inhibitor and expanded graphite; the hydrated salt crystal mixture comprises several kinds of hydrated salt crystals, and the unit cell structure parameters of the hydrated salt crystals differ by less than 15%; wherein the hydrated salt crystal mixture, as a cold storage functional body, can absorb a large amount of heat energy during the phase change process, and by selecting several kinds of hydrated salt crystals with unit cell structure parameters differing by less than 15% for mixing, it can effectively promote nucleation and reduce supercooling, thereby promoting cold storage performance, improving the phase change latent heat of the hydrated salt phase change cold storage material, and adjusting the phase change temperature; by adjusting the type and amount of the phase change temperature regulator, the phase change temperature of the composite phase change cold storage material can be accurately controlled to meet the needs of different application scenarios; the supercooling inhibitor cooperates with the hydrated salt crystal mixture to effectively promote the smooth crystallization of the hydrated salt crystal mixture during the phase change process, and further improves the performance of the cold storage material. One step to reduce supercooling and improve cold storage performance; phase separation inhibitors can effectively inhibit the phase separation of hydrated salt crystal mixtures, thereby maintaining the uniformity and stability of the material, while increasing the viscosity of the material and reducing the loss of water molecules in the hydrated salt. However, although excessive phase separation inhibitors can prevent the loss of water molecules, they will cause the hydrated salt to have high viscosity, affecting the energy storage performance and energy release efficiency of the material. The presence of expanded graphite can not only absorb the lost water molecules, but also cooperate with the phase inhibitor to inhibit phase separation, retain water molecules in the phase change material, maintain the uniformity of the material, and enhance its stability. Moreover, its porous and curved worm-like structure provides good adsorption and sealing properties, preventing the phase change material from leaking during use and avoiding damage caused by contact with the environment. It also effectively improves the thermal conductivity of the material, expands the area of ​​heating and cooling, and enables the phase change material to absorb and release heat faster during the cold storage and release process, thereby improving the cold storage efficiency.

[0016] The hydrated salt crystal mixture includes disodium hydrogen phosphate dodecahydrate and sodium sulfate decahydrate, both of which have good heat storage performance and can undergo phase change at a specific temperature, thereby storing or releasing a large amount of thermal energy. The mixture of the two can effectively promote nucleation and reduce supercooling, and a composite phase change material with a specific phase change temperature can be prepared.

[0017] In terms of mass percentage, in the hydrated salt crystal mixture, disodium hydrogen phosphate dodecahydrate accounts for 55% to 65%, and sodium sulfate decahydrate accounts for 35% to 45%. The hydrated salt crystal mixture within this ratio range has a higher latent heat of phase change and can store or release more energy during the phase change process, ensuring that the mixture can continuously and effectively store and release heat energy in long-term applications.

[0018] The phase change temperature regulator is ammonium chloride. When ammonium chloride is used as the phase change temperature regulator, it can achieve the regulation of the phase change temperature while maintaining a high phase change latent heat.

[0019] The supercooling inhibitor is borax, which is an effective nucleating agent and can significantly reduce the supercooling degree of the hydrated salt crystal mixture, and cooperate with the hydrated salt crystal mixture to suppress the supercooling problem of the entire phase change material.

[0020] The phase separation inhibitor is sodium carboxymethyl cellulose. As a high molecular compound, sodium carboxymethyl cellulose is an anionic polysaccharide. Its carboxylmethyl group carries negative charges. These negative charges can form an electrostatic barrier between different components to prevent them from aggregating or separating due to charge interactions. Its long molecular chain structure can expand in the solution, increasing the distance between different components, generating a steric hindrance effect, preventing direct contact and aggregation between components, thereby inhibiting the occurrence of phase separation and being able to form good compatibility with a hydrated salt crystal mixture, exerting a significant phase separation inhibitory effect. At the same time, sodium carboxymethyl cellulose acts as a thickener to increase the viscosity of the material, reduce the loss of water molecules in water and salt, and cooperates with expanded graphite to absorb a small amount of lost water molecules, retaining the water molecules in the material, thereby avoiding the instability of the material caused by water loss.

[0021] The present invention also provides a method for preparing the expanded graphite-hydrated salt composite phase-change cold storage material as described above, the method comprising the steps of: melting a hydrated salt crystal mixture with a phase change temperature regulator, a supercooling inhibitor and a phase separation inhibitor in sequence to form a molten mixture D; and then uniformly mixing the molten mixture D with the expanded graphite to obtain the expanded graphite-hydrated salt composite phase-change cold storage material. Among them, the addition of phase change temperature regulator can adjust the phase change temperature of the composite phase change material to adapt it to specific application requirements and ensure that the material effectively stores and releases cold energy within the required temperature range; the addition of supercooling inhibitor can effectively reduce or eliminate supercooling, so that the composite phase change material undergoes phase change when it is closer to its theoretical phase change temperature; the phase separation inhibitor can increase the viscosity of the system and enhance the interaction between the components, thereby inhibiting the occurrence of phase separation, which helps to improve the energy storage efficiency and stability of the material, and ensure that the hydrated salt crystals and expanded graphite and other components remain evenly distributed during storage and use to avoid performance degradation; the phase change material is loaded with expanded graphite. On the one hand, the expanded graphite has a porous structure and can provide structural support for the composite phase change material. This support can assist the synergistic phase separation inhibitor to enhance the stability of the phase change material, prevent the phase change material from leaking during use, and avoid damage to the environment; on the other hand, it can increase the thermal conductivity of the phase change material, expand the area of ​​heating and cooling, and enhance its storage and release cooling performance. The preparation method is simple and easy to operate, and the raw materials used in the prepared inorganic-inorganic composite phase change cold storage material are low-cost and easy to obtain, which reduces the difficulty in practical application.

[0022] The melting temperatures of the melt-to-molten mixture A, the melt-to-molten mixture B, the melt-to-molten mixture C and the melt-to-molten mixture D are all 50°C to 70°C.

[0023] An expanded graphite-hydrated salt composite phase-change cold storage material prepared by the above method, wherein the phase change temperature of the expanded graphite-hydrated salt composite phase-change cold storage material is 2°C to 10°C, and the material has the advantages of suitable phase change temperature, high phase change latent heat, small supercooling, stable properties, not easy to phase separation, and environmental friendliness, and can be applied to cold chain transportation, building cooling, refrigerator energy saving, air conditioning temperature control and other fields.

[0024] As mentioned above, the application of expanded graphite-hydrated salt composite phase change cold storage materials in cold storage technology, expanded graphite-hydrated salt composite phase change cold storage materials in cold storage technology has the characteristics of high efficiency, stability, environmental protection and low cost, and can be widely used in air-conditioning systems, building energy conservation, cold chain logistics, solar energy cold storage, water heating, power generation and other fields, and has broad application prospects and important research value in energy conservation, environmental protection and new energy utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1The present invention is a schematic flow chart of a method for preparing an expanded graphite-hydrated salt composite phase-change cold storage material.

[0026] Figure 2 This is a step cooling curve diagram of the expanded graphite-hydrated salt composite phase change cold storage material prepared in Examples 1-4 of the present invention.

[0027] Figure 3 This is a DSC curve diagram of the expanded graphite-hydrated salt composite phase change cold storage material prepared in Example 1 of the present invention.

[0028] Figure 4 This is a stability curve diagram of the composite phase change cold storage material prepared in Comparative Example 1 of the present invention.

[0029] Figure 5 This is a stability curve diagram of the expanded graphite-hydrated salt composite phase change cold storage material prepared in Example 1 of the present invention.

[0030] Figure 6 This is a stability curve diagram of the composite phase change cold storage material prepared in Comparative Example 2.

[0031] Figure 7 This is a stability curve diagram of the composite phase change cold storage material prepared in Comparative Example 3. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0033] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0034] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0035] The present invention provides an expanded graphite-hydrated salt composite phase-change cold storage material, which at least comprises a hydrated salt crystal mixture, a phase-change temperature regulator, a supercooling inhibitor, a phase separation inhibitor and expanded graphite; The hydrated salt crystal mixture includes several kinds of hydrated salt crystals, and the unit cell structure parameters of the hydrated salt crystals differ by less than 15%; In terms of mass percentage, after the hydrated salt crystal mixture is mixed with the phase change temperature regulator, the proportion of the phase change temperature regulator is 10% to 25%; after the hydrated salt crystal mixture is mixed with the phase change temperature regulator and the supercooling inhibitor, the proportion of the supercooling inhibitor is 1% to 4%; after the hydrated salt crystal mixture is mixed with the phase change temperature regulator, the supercooling inhibitor and the phase separation inhibitor, the proportion of the phase separation inhibitor is 1% to 4%; after the hydrated salt crystal mixture is mixed with the phase change temperature regulator, the supercooling inhibitor, the phase separation inhibitor and the expanded graphite, the proportion of the expanded graphite is 3% to 9%; Preferably, the hydrated salt crystal mixture includes disodium hydrogen phosphate dodecahydrate and sodium sulfate decahydrate, and in the hydrated salt crystal mixture, the proportion of disodium hydrogen phosphate dodecahydrate is 55% to 65%, and the proportion of sodium sulfate decahydrate is 35% to 45% by mass; the phase change temperature regulator is ammonium chloride; the supercooling inhibitor is borax; and the phase separation inhibitor is sodium carboxymethyl cellulose.

[0036] See also Figure 1 The present invention provides a method for preparing the above-mentioned expanded graphite-hydrated salt composite phase change cold storage material, comprising: S1: melting the hydrated salt crystal mixture into a molten mixture A, specifically: mixing 55% to 65% of disodium hydrogen phosphate dodecahydrate and 35% to 45% of sodium sulfate decahydrate by mass percentage, heating in a water bath at 50° C. to 70° C., and melting into the molten mixture A; S2: Mixing the molten mixture A with the phase change temperature regulator to melt into a molten mixture B, specifically: 75% to 85% of the molten mixture A and 10% to 25% of the phase change temperature regulator are mixed by mass fraction, heated in a water bath at 50° C. to 70° C., and melted into a molten mixture B; S3: Mixing the molten mixture B with the supercooling inhibitor to melt into a molten mixture C, specifically: 96% to 99% of the molten mixture B and 1% to 4% of the supercooling inhibitor are mixed by mass fraction, heated in a water bath at 50°C to 70°C, and melted into a molten mixture C; S4: Mixing the molten mixture C with the phase separation inhibitor and melting them into a molten mixture D, specifically: 96% to 98% of the molten mixture C and 1% to 4% of the phase separation inhibitor are mixed by mass, heated in a water bath at 50° C. to 70° C., and melted to obtain a molten mixture D; S5: Evenly mix the molten mixture D and the expanded graphite to obtain an expanded graphite-hydrated salt composite phase change cold storage material, specifically: 3% to 9% of expanded graphite and 91% to 97% of molten mixture D are mixed by mass, heated in a water bath at 50° C. to 70° C., and mixed evenly to obtain an expanded graphite-hydrated salt composite phase change cold storage material.

[0037] Example 1 55% of disodium hydrogen phosphate dodecahydrate and 45% of sodium sulfate decahydrate are mixed according to mass percentage, and heated in a water bath at 55° C. to melt into a molten mixture A; 90% of the molten mixture A and 10% of ammonium chloride are mixed by mass, heated in a water bath at 55°C to melt into a molten mixture B; 99% of the molten mixture B and 1% of borax are mixed by mass, heated in a water bath at 55°C, and melted into a molten mixture C; 98% of the molten mixture C and 2% of sodium carboxymethyl cellulose were mixed by mass, heated in a water bath at 55°C, and melted into a molten mixture D; 5% of expanded graphite and 95% of molten mixture D were mixed by mass fraction, heated in a water bath at 55° C., and mixed evenly to obtain an expanded graphite-hydrated salt composite phase change cold storage material.

[0038] Example 2 55% of disodium hydrogen phosphate dodecahydrate and 45% of sodium sulfate decahydrate are mixed according to mass percentage, and heated in a water bath at 55° C. to melt into a molten mixture A; 90% of the molten mixture A and 10% of ammonium chloride are mixed by mass, heated in a water bath at 55°C to melt into a molten mixture B; 99% of the molten mixture B and 1% of borax are mixed by mass, heated in a water bath at 55°C, and melted into a molten mixture C; 98% of the molten mixture C and 2% of sodium carboxymethyl cellulose were mixed by mass, heated in a water bath at 55°C, and melted into a molten mixture D; 7% of expanded graphite and 93% of molten mixture D were mixed by mass fraction, heated in a water bath at 55° C., and mixed evenly to obtain an expanded graphite-hydrated salt composite phase change cold storage material.

[0039] Example 3 55% of disodium hydrogen phosphate dodecahydrate and 45% of sodium sulfate decahydrate are mixed according to mass percentage, and heated in a water bath at 55° C. to melt into a molten mixture A; 90% of the molten mixture A and 10% of ammonium chloride are mixed by mass, heated in a water bath at 55°C to melt into a molten mixture B; 99% of the molten mixture B and 1% of borax are mixed by mass, heated in a water bath at 55°C, and melted into a molten mixture C; 98% of the molten mixture C and 2% of sodium carboxymethyl cellulose were mixed by mass, heated in a water bath at 55°C, and melted into a molten mixture D; 3% of expanded graphite and 97% of molten mixture D were mixed by mass fraction, heated in a water bath at 55° C., and mixed evenly to obtain an expanded graphite-hydrated salt composite phase change cold storage material.

[0040] Example 4 55% of disodium hydrogen phosphate dodecahydrate and 45% of sodium sulfate decahydrate are mixed according to mass percentage, and heated in a water bath at 55° C. to melt into a molten mixture A; 90% of the molten mixture A and 10% of ammonium chloride are mixed by mass, heated in a water bath at 55°C to melt into a molten mixture B; 99% of the molten mixture B and 1% of borax are mixed by mass, heated in a water bath at 55°C, and melted into a molten mixture C; 98% of the molten mixture C and 2% of sodium carboxymethyl cellulose were mixed by mass, heated in a water bath at 55°C, and melted into a molten mixture D; 9% of expanded graphite and 91% of molten mixture D were mixed by mass fraction, heated in a water bath at 55° C., and mixed evenly to obtain an expanded graphite-hydrated salt composite phase change cold storage material.

[0041] Example 5 60% of disodium hydrogen phosphate dodecahydrate and 40% of sodium sulfate decahydrate are mixed according to mass percentage, and heated in a water bath at 60° C. to melt into a molten mixture A; 85% of the molten mixture A and 15% of ammonium chloride are mixed by mass, heated in a water bath at 60°C, and melted into a molten mixture B; 98% of the molten mixture B and 2% of borax are mixed by mass, heated in a water bath at 55°C, and melted into a molten mixture C; 97% of the molten mixture C and 3% of sodium carboxymethyl cellulose were mixed by mass, heated in a water bath at 60°C, and melted into a molten mixture D; 9% of expanded graphite and 91% of molten mixture D were mixed by mass fraction, heated in a water bath at 60° C., and mixed evenly to obtain an expanded graphite-hydrated salt composite phase change cold storage material.

[0042] Example 6 65% of disodium hydrogen phosphate dodecahydrate and 35% of sodium sulfate decahydrate are mixed according to mass percentage, and heated in a water bath at 70° C. to melt into a molten mixture A; 80% of the molten mixture A and 20% of ammonium chloride are mixed by mass, heated in a water bath at 70°C, and melted into a molten mixture B; 97% of the molten mixture B and 3% of borax are mixed by mass, heated in a water bath at 70°C, and melted into a molten mixture C; 97% of the molten mixture C and 3% of sodium carboxymethyl cellulose were mixed by mass, heated in a water bath at 70°C, and melted into a molten mixture D; 7% of expanded graphite and 93% of molten mixture D were mixed by mass, heated in a water bath at 70°C, and mixed evenly to obtain an expanded graphite-hydrated salt composite phase change cold storage material.

[0043] Example 7 60% of disodium hydrogen phosphate dodecahydrate and 40% of sodium sulfate decahydrate are mixed according to mass percentage, and heated in a water bath at 65° C. to melt into a molten mixture A; 75% of the molten mixture A and 25% of ammonium chloride are mixed by mass, heated in a water bath at 65°C to melt into a molten mixture B; 96% of the molten mixture B and 4% of borax are mixed by mass, heated in a water bath at 70°C, and melted into a molten mixture C; 97% of the molten mixture C and 3% of sodium carboxymethyl cellulose were mixed by mass, heated in a water bath at 70°C, and melted into a molten mixture D; 7% of expanded graphite and 95% of molten mixture D were mixed by mass fraction, heated in a water bath at 70° C., and mixed evenly to obtain an expanded graphite-hydrated salt composite phase change cold storage material.

[0044] Comparative Example 1 55% of disodium hydrogen phosphate dodecahydrate and 45% of sodium sulfate decahydrate are mixed according to mass percentage, and heated in a water bath at 55° C. to melt into a molten mixture A; 90% of the molten mixture A and 10% of ammonium chloride are mixed by mass, heated in a water bath at 55°C to melt into a molten mixture B; 99% of the molten mixture B and 1% of borax are mixed by mass, heated in a water bath at 55°C, and melted into a molten mixture C; 98% of the molten mixture C was mixed with 2% of sodium carboxymethyl cellulose by mass fraction, and heated in a water bath at 55° C. to obtain a phase change cold storage material.

[0045] Comparative Example 2 55% of disodium hydrogen phosphate dodecahydrate and 45% of sodium sulfate decahydrate are mixed according to mass percentage, and heated in a water bath at 55° C. to melt into a molten mixture A; 90% of the molten mixture A and 10% of ammonium chloride are mixed by mass, heated in a water bath at 55°C to melt into a molten mixture B; 99% of the molten mixture B and 1% of borax are mixed by mass, heated in a water bath at 55°C, and melted into a molten mixture C; 98% of the molten mixture C and 2% of sodium polyacrylate were mixed by mass, heated in a water bath at 55°C, and melted into a molten mixture D; Calculated by mass fraction, 5% of expanded graphite was mixed with 95% of molten mixture D, heated in a water bath at 55° C., and mixed evenly to obtain a composite phase change cold storage material.

[0046] Comparative Example 3 55% of disodium hydrogen phosphate dodecahydrate and 45% of sodium sulfate decahydrate are mixed according to mass percentage, and heated in a water bath at 55° C. to melt into a molten mixture A; 90% of the molten mixture A and 10% of ammonium chloride are mixed by mass, heated in a water bath at 55°C to melt into a molten mixture B; 99% of the molten mixture B and 1% of borax are mixed by mass, heated in a water bath at 55°C, and melted into a molten mixture C; 98% of the molten mixture C and 2% of the polyacrylamide were mixed by mass fraction, heated in a water bath at 55°C, and melted into a molten mixture D; Calculated by mass fraction, 5% of expanded graphite was mixed with 95% of molten mixture D, heated in a water bath at 55° C., and mixed evenly to obtain a composite phase change cold storage material.

[0047] The performance tests of Examples 1-4 and Comparative Examples 1-3 were compared. Figure 2It can be seen that the composite phase change materials with different expanded graphite contents have little effect on supercooling, proving that the addition of expanded graphite will not destroy the role of borax as a supercooling inhibitor in the composite material. Figure 2 In the embodiment, DHPD-SSD-NBC-3%EG represents the expanded graphite-hydrated salt composite phase change cold storage material prepared in Example 3, DHPD-SSD-NBC-5%EG represents the expanded graphite-hydrated salt composite phase change cold storage material prepared in Example 1, DHPD-SSD-NBC-7%EG represents the expanded graphite-hydrated salt composite phase change cold storage material prepared in Example 2, and DHPD-SSD-NBC-9%EG represents the expanded graphite-hydrated salt composite phase change cold storage material prepared in Example 4. Figure 3 From the DSC curve, it can be seen that the phase change temperature of the expanded graphite-hydrated salt composite phase change cold storage material is 4.2°C, and the phase change latent heat is 285.4 J / g; see Figure 4 , when the composite phase change material prepared in comparative example 1 is subjected to a temperature rise and fall cycle, the step cooling curves at the first and 100th cooling times show that the phase change temperature difference between the first and 100th cooling times is 4.2°C, indicating poor stability; see Figure 5 When the expanded graphite-hydrated salt composite phase change cold storage material is heated and cooled in a cycle, the step cooling curves at the first and 100th cooling times show that the phase change temperature difference between the first and 100th cooling times is only 0.35°C, and the step cooling curves are basically the same, proving that the addition of EG effectively enhances its stability. Figure 6 , when the composite phase change material prepared in comparative example 2 is subjected to a temperature rise and fall cycle, the step cooling curves at the first and 100th cooling times show that the phase change temperature difference between the first and 100th cooling times is 5.6°C, indicating poor stability; see Figure 7 When the composite phase change material prepared in Comparative Example 3 was subjected to a temperature rise and fall cycle, from the step cooling curves at the 1st and 100th cooling times, it can be seen that the phase change temperature difference between the 1st and 100th cooling times was 2.6°C, and the stability was average; thus, it can be seen that the synergistic effect of sodium carboxymethyl cellulose and expanded graphite can significantly improve the stability of the phase change cold storage material.

[0048] The present invention provides an expanded graphite-hydrated salt composite phase-change cold storage material prepared by the above method. The phase change temperature of the expanded graphite-hydrated salt composite phase-change cold storage material is 2°C to 10°C. The expanded graphite-hydrated salt composite phase-change cold storage material has the advantages of suitable phase change temperature, high phase change latent heat, small supercooling, stable properties, not easy to phase separation, environmental friendliness, etc., and can be applied to cold chain transportation, building cooling, refrigerator energy saving, air conditioning temperature control and other fields.

[0049] Application of the expanded graphite-hydrated salt composite phase change energy storage material in the energy storage technology as described above. The expanded graphite-hydrated salt composite phase change energy storage material has the characteristics of high efficiency, stability, environmental protection and low cost in the energy storage technology, and can be widely applied to fields such as air conditioning systems, building energy conservation, cold chain logistics, solar energy energy storage, water heating, power generation, etc. It has broad application prospects and important research value in aspects such as energy conservation, environmental protection and new energy utilization.

[0050] In summary, the present invention provides an expanded graphite-hydrated salt composite phase change energy storage material, a preparation method and an application. By using a hydrated salt crystal mixture as the energy storage functional body and mixing several hydrated salt crystals with the difference in unit cell structure parameters within 15%, the nucleation is promoted to reduce supercooling and the latent heat of phase change of the hydrated salt phase change energy storage material is increased; by adjusting the type and dosage of the phase change temperature regulator, the phase change temperature of the composite phase change energy storage material can be accurately controlled to meet the requirements of different application scenarios; by using a supercooling inhibitor to cooperate with the hydrated salt crystal mixture, the supercooling degree is further reduced and the energy storage performance is improved; by using a phase separation inhibitor to inhibit the phase separation of the hydrated salt crystal mixture and cooperating with the expanded graphite to retain water molecules in the phase change material, the uniformity of the material is maintained, its stability is enhanced, and the finally obtained phase change energy storage material has the advantages of appropriate phase change temperature, high latent heat of phase change, small supercooling degree, stable properties and not easy to phase separate, and being environmentally friendly. It promotes the development of the hydrated salt phase change energy storage material in fields such as cold chain transportation, building cooling, refrigerator energy conservation, air conditioning temperature regulation, etc.

[0051] The above are only the preferred embodiments of the present invention and are not used to limit the technical solutions of the present invention in any way. Those skilled in the art should understand that without departing from the spirit and principle of the present invention, the technical solutions can be subject to several simple modifications and substitutions, and these modifications and substitutions also fall within the protection scope covered by the claims.

Claims

1. An expanded graphite-hydrated salt composite phase change cold storage material, characterized in that: At least comprising a hydrated salt crystal mixture, a phase change temperature regulator, a supercooling inhibitor, a phase separation inhibitor and expanded graphite; The hydrated salt crystal mixture includes several kinds of hydrated salt crystals, and the unit cell structure parameters of the hydrated salt crystals differ by less than 15%; In terms of mass percentage, after the hydrated salt crystal mixture is mixed with the phase change temperature regulator, the proportion of the phase change temperature regulator is 10% to 25%; after the hydrated salt crystal mixture is mixed with the phase change temperature regulator and the supercooling inhibitor, the proportion of the supercooling inhibitor is 1% to 4%; after the hydrated salt crystal mixture is mixed with the phase change temperature regulator, the supercooling inhibitor and the phase separation inhibitor, the proportion of the phase separation inhibitor is 1% to 4%; after the hydrated salt crystal mixture is mixed with the phase change temperature regulator, the supercooling inhibitor, the phase separation inhibitor and the expanded graphite, the proportion of the expanded graphite is 3% to 9%.

2. The expanded graphite-hydrated salt composite phase change cold storage material according to claim 1, characterized in that: The hydrated salt crystal mixture includes disodium hydrogen phosphate dodecahydrate and sodium sulfate decahydrate.

3. The expanded graphite-hydrated salt composite phase change cold storage material according to claim 2, characterized in that: In terms of mass percentage, in the hydrated salt crystal mixture, disodium hydrogen phosphate dodecahydrate accounts for 55% to 65%, and sodium sulfate decahydrate accounts for 35% to 45%.

4. The expanded graphite-hydrated salt composite phase change cold storage material according to claim 1, characterized in that: The phase change temperature regulator is ammonium chloride.

5. The expanded graphite-hydrated salt composite phase change cold storage material according to claim 1, characterized in that: The supercooling inhibitor is borax.

6. The expanded graphite-hydrated salt composite phase change cold storage material according to claim 1, characterized in that: The phase separation inhibitor is sodium carboxymethyl cellulose.

7. The method for preparing the expanded graphite-hydrated salt composite phase change cold storage material according to any one of claims 1 to 6, characterized in that: include: Melting the hydrated salt crystal mixture into a molten mixture A; Mixing the molten mixture A with the phase change temperature regulator to melt into the molten mixture B; Mixing the molten mixture B with the supercooling inhibitor to melt into a molten mixture C; Mixing the molten mixture C with a phase separation inhibitor and melting them into a molten mixture D; The molten mixture D is mixed evenly with expanded graphite to obtain an expanded graphite-hydrated salt composite phase change cold storage material.

8. The method for preparing the expanded graphite-hydrated salt composite phase change cold storage material according to claim 7, characterized in that: The melting temperatures of the melt-to-molten mixture A, the melt-to-molten mixture B, the melt-to-molten mixture C and the melt-to-molten mixture D are all 50°C to 70°C.

9. An expanded graphite-hydrated salt composite phase change cold storage material prepared by the method of claim 7 or 8, characterized in that: The phase change temperature of the expanded graphite-hydrated salt composite phase change cold storage material is 2°C to 10°C.

10. Use of the expanded graphite-hydrated salt composite phase change cold storage material according to any one of claims 1 to 6 in cold storage technology.

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