Phase change material with phase change temperature of-30 to-40 DEG C and preparation method thereof

Abstract

The invention discloses a phase change material with a phase change temperature of-30 to-40 DEG C and a preparation method thereof, and belongs to the technical field of inorganic phase change materials. The high-conductivity magnesium chloride composite material comprises the following raw materials in percentage by weight: 10%-50% of magnesium chloride hexahydrate, 5%-30% of sodium chloride, 0.5%-10% of a high-conductivity material, 0.1%-5% of a thickening agent, 0.1%-5% of a nucleating agent and the balance of deionized water. The phase change temperature of the phase change material ranges from-30 DEG C to-40 DEG C, the heat conductivity is increased to 0.65 W / (m.K) from 0.59 W / (m.K), the phase change latent heat value is 160 J / g, the supercooling degree is reduced to 4.3 DEG C at present from original 9.75 DEG C, and the supercooling degree is smaller than or equal to 5 DEG C.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic phase change materials, and in particular relates to an inorganic phase change material with a phase change temperature of -30 to -40°C. Background Art

[0002] Phase change materials (PCMs) are substances that change state and provide latent heat while maintaining constant temperature. The process of changing physical properties is called a phase change, during which the PCM absorbs or releases large amounts of latent heat.

[0003] Phase change materials can be divided into organic and inorganic phase change materials. They can also be divided into hydrated salt phase change materials and wax phase change materials.

[0004] In cold chain transportation, different single inorganic phase change materials are typically used in different temperature ranges: calcium chloride hexahydrate is commonly used in the 2-8°C range, sodium chloride brine solutions are often used in the -18°C range, and mixed solutions of calcium chloride and magnesium chloride are preferred in the 40°C to 60°C range. However, these materials generally suffer from disadvantages such as phase separation, high supercooling, strong corrosiveness, low latent heat of phase change, and poor heat transfer efficiency. This not only affects cold chain efficiency and cargo quality, but also increases equipment maintenance costs and operational risks.

[0005] Application No. 202410364960X discloses an ultra-low temperature inorganic phase change material, its preparation method and application. Magnesium chloride is selected as the main material and is combined with a specific amount of inorganic eutectic material, inorganic nucleating agent and solvent. The prepared phase change material has a phase change temperature of -45 to -35°C, but the patent does not mention thermal conductivity control.

[0006] Application No. 2022109663688 discloses a low-temperature phase-change material. The phase-change material includes a primary energy storage agent, water, a nucleating agent, a thickener, and an auxiliary energy storage agent. However, the primary energy storage agent is ammonium chloride, and the phase-change temperature is -32 to -36°C. The auxiliary energy storage agent in this patent contains organic materials, which increases the cost. Summary of the Invention

[0007] In order to solve the above problems, the present invention provides a method for preparing a phase change material with a phase change temperature of -30 to -40°C, wherein the weight percentage of the raw materials is as follows: Magnesium chloride hexahydrate 10%-50% Sodium chloride 5%-30% Thermal conductive material 0.5%-10% Thickener 0.1%-5% Nucleating agent 0.1%-5% The balance was deionized water.

[0008] The thermal conductive material is one or more of graphite, graphite powder, nanographite, carbon nanotube or expanded graphite.

[0009] The thickener is one or more of diatomaceous earth, xanthan gum, sodium alginate, hydroxymethyl cellulose or polyacrylamide.

[0010] The phase change temperature is -30 to -40°C, the thermal conductivity is 0.6 to 0.7 W / (m·K), and the latent heat value is 160 to 180 J / g.

[0011] The preparation method of the phase change material comprises the following steps: (1) Deionized water at a temperature of 20-60°C is placed in a container according to the weight ratio, and magnesium chloride hexahydrate is slowly added, stirred thoroughly, and allowed to stand at a constant temperature of 30-60°C for 20-30 minutes. Then sodium chloride is added, stirred thoroughly, and allowed to stand again for 20-30 minutes to obtain solution A.

[0012] (2) Add the thermal conductive material to solution A according to the weight ratio, stir and mix thoroughly to obtain solution B.

[0013] (3) Add thickener to solution B according to the weight ratio and stir thoroughly to obtain solution C.

[0014] (4) Add a nucleating agent to solution C according to a weight ratio and stir thoroughly to obtain a phase change material.

[0015] Compared with the prior art, the present invention has the following advantages: The phase change material of the present invention has a phase transition temperature of -30 to -40°C, a thermal conductivity of 0.6 to 0.7 W / (m·K), and a latent heat of 160 to 180 J / g. The degree of supercooling is ≤5°C, and the material exhibits excellent cyclic stability. The preparation process of the present invention utilizes a step-by-step blending method, conducted entirely at 20-60°C with a stirring speed of 300-1000 rpm. Stirring is continued for 1-2 hours after each addition of a material, followed by 1-2 hours of quiescence. Large-scale production can be achieved at room temperature and pressure, with temperature control accuracy of ±0.5°C in key steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The process flow chart of the present invention is Figure 2 DSC results of the phase change material prepared in Example 1 Figure 3 Thermal conductivity test diagram of the phase change material prepared in Example 1 Figure 4 Thermal conductivity test diagram of the phase change material prepared in Example 2 Figure 5 This is a supercooling test diagram of the phase change material prepared in Example 3 DETAILED DESCRIPTION

[0017] The present invention is further illustrated below by specific examples. However, those skilled in the art should be aware that the specific examples of the present invention do not limit the present invention in any way, and any equivalent replacements made on the basis of the present invention fall within the scope of protection of the present invention. Example 1

[0018] The preparation method of the phase change cold storage material comprises the following steps: (1) Place 40-50 parts of deionized water at 25°C into a container, then slowly add 30-40 parts of magnesium chloride hexahydrate, stir thoroughly, and let stand at a constant temperature of 30°C for 20-30 minutes. Then add 10-15 parts of sodium chloride, stir thoroughly, and let stand again for 20-30 minutes to obtain solution A. (2) Add 0-5 parts of graphite powder to solution A according to the weight ratio, stir and mix thoroughly to obtain solution B; Depend on Figure 2 It can be seen from the DSC curve that the phase change temperature of the phase change material prepared in this embodiment is -37°C, and the phase change latent heat value is 180 J / g.

[0019] Depend on Figure 3 It can be seen that the thermal conductivity is 0.6 W / (m·K), 0.59 W / (m·K), 0.63 W / (m·K), 0.68 W / (m·K), and 0.75 W / (m·K). Example 2

[0020] like Figure 1 As shown, the present invention discloses a method for preparing a phase-change phase-change cold storage material, comprising the following steps in sequence: (1) Place 40-50 parts of deionized water at 25°C into a container, then slowly add 30-40 parts of magnesium chloride hexahydrate, stir thoroughly, and let stand at a constant temperature of 30°C for 20-30 minutes. Then add 10-15 parts of sodium chloride, stir thoroughly, and let stand again for 20-30 minutes to obtain solution A. (2) Add 0-5 parts of graphite powder to solution A according to the weight ratio, stir and mix thoroughly to obtain solution B; (3) Add 0-2 parts of hydroxymethyl cellulose to solution B according to the weight ratio and stir thoroughly to obtain solution C.

[0021] Depend on Figure 4 It can be seen that the thermal conductivities are 0.75 W / (m·K), 0.73 W / (m·K), 0.69 W / (m·K), 0.65 W / (m·K), and 0.64 W / (m·K) respectively. Example 3

[0022] like Figure 1 As shown, the present invention discloses a method for preparing a phase-change phase-change cold storage material, comprising the following steps in sequence: (1) Place 40-50 parts of deionized water at 25°C into a container, then slowly add 30-40 parts of magnesium chloride hexahydrate, stir thoroughly, and let stand at a constant temperature of 30°C for 20-30 minutes. Then add 10-15 parts of sodium chloride, stir thoroughly, and let stand again for 20-30 minutes to obtain solution A. (2) Add 0-5 parts of graphite powder to solution A according to the weight ratio, stir and mix thoroughly to obtain solution B; (3) Add 0-2 parts of hydroxymethyl cellulose to solution B according to the weight ratio and stir thoroughly to obtain solution C.

[0023] (4) Add 0-5 parts of graphite powder, borax and diatomaceous earth to solution C according to the weight ratio, stir thoroughly, and obtain a phase change material.

[0024] Depend on Figure 4 It can be seen that the supercooling degrees are 3.6℃, ​​6.11℃ and 3.95℃ respectively.

Claims

1. A phase change material with a phase change temperature of -30 to -40°C, characterized in that: The weight percentage composition of the raw materials is: Magnesium chloride hexahydrate 10%-50% Sodium chloride 5%-30% Thermal conductive material 0.5%-10% Thickener 0.1%-5% Nucleating agent 0.1%-5% The balance was deionized water.

2. The phase change material according to claim 1, wherein: The thermal conductive material is one or more of graphite, graphite powder, nanographite, carbon nanotube or expanded graphite.

3. The phase change material according to claim 1, wherein: The thickener is one or more of xanthan gum, sodium alginate, hydroxymethyl cellulose or ammonium polyacrylate.

4. The phase change material according to claim 1, wherein: The nucleating agent is one or more of diatomaceous earth, graphite powder or borax.

5. The phase change material according to any one of claims 1 to 4, characterized in that: The phase change temperature is -30~-40℃, the thermal conductivity is 0.6~0.7 W / (m·K), the phase change latent heat is 160~180 J / g, and the supercooling degree is ≤5℃.

6. The method for preparing the phase change material according to claim 5, characterized in that The following steps are involved: (1) Deionized water at a temperature of 20-60°C is placed in a container according to the weight ratio, and magnesium chloride hexahydrate is slowly added, stirred thoroughly, and allowed to stand for 20-30 minutes while maintaining a constant temperature of 30-60°C. Then sodium chloride is added, stirred thoroughly, and allowed to stand for another 20-30 minutes to obtain solution A. (2) Add the thermal conductive material to solution A according to the weight ratio, stir and mix thoroughly to obtain solution B; (3) Add thickener to solution B according to the weight ratio and stir thoroughly to obtain solution C; (4) Add a nucleating agent to solution C according to a weight ratio and stir thoroughly to obtain a phase change material.

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