A high thermal conductivity shaped composite phase change material and preparation method thereof

Abstract

The present invention discloses a high thermal conductivity shaped composite phase change material and a preparation method thereof, belonging to the field of phase change heat storage. The composite phase change material is made of foam metal filled with a modified phase change material, wherein the modified phase change material is composed of the following components by mass percentage: 98.7~99.3% barium hydroxide octahydrate, 0.2~0.8% nano copper oxide, and 0.5% thickener. The phase change temperature of the modified phase change material is 77.5°C, the phase change latent heat is 277.3J / g, and the thermal conductivity of the composite phase change material is 12.4W / (m·K). The present invention has the advantages of high latent heat and high thermal conductivity, can meet the actual needs of various engineering projects, and solves the problems of poor stability and low thermal conductivity of barium hydroxide octahydrate as a phase change material.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic phase change energy storage materials, in particular to a high thermal conductivity composite phase change material and a preparation method thereof. Background Art

[0002] Phase change energy storage materials, as effective media for storing and releasing heat, have become a hot topic worthy of research. Macroscopically, phase change materials can be divided into two categories: organic and inorganic. The representative of the organic type is paraffin, which is now widely used. However, its low thermal conductivity, large heat storage volume, and high price greatly affect its practicality. Inorganic phase change materials, especially inorganic hydrated salt phase change materials, have many advantages such as high heat storage density, high heat storage efficiency, and nearly constant heat release temperature. Therefore, they can be applied in many fields, such as photothermal utilization, industrial waste heat recovery, the construction industry, and electronic component heat dissipation.

[0003] Barium hydroxide octahydrate is a cheap, readily available phase change energy storage material with a very high latent heat of phase change (266-295 J / g). It has broad application prospects. However, it has problems such as large supercooling, severe phase separation, and low thermal conductivity, which hinder its application in practical engineering. Therefore, reducing its supercooling and improving its stability (reducing phase separation) has become the primary task of studying barium hydroxide octahydrate.

[0004] Adding a nucleating agent is an effective method for eliminating supercooling in inorganic phase change materials. However, barium hydroxide octahydrate has a monoclinic crystal structure, making it difficult to find a nucleating agent with a lattice parameter difference within 15%. Nucleating agents used in existing technologies mostly chemically react with barium hydroxide octahydrate, significantly reducing its heat storage performance. Furthermore, existing technologies disclose the use of expanded graphite to enhance the thermal conductivity of phase change materials. However, expanded graphite limits the heat storage performance of barium hydroxide octahydrate to a certain extent, and the enhanced thermal conductivity is also very limited (3-4 W / (m·K)), which is only about three times that of pure barium hydroxide octahydrate (1.2 W / (m·K)). Therefore, there is an urgent need to find a material that can both reduce the supercooling of phase change materials and improve their thermal conductivity. Summary of the Invention

[0005] The purpose of the present invention is to provide a shaped composite phase change material based on a foam metal skeleton and a preparation method thereof, so as to solve the problems of supercooling and phase separation of the phase change material, and improve the defects of the phase change material such as low thermal conductivity and reduced phase change latent heat.

[0006] The technical solutions for achieving the purpose of the present invention are:

[0007] A composite phase change material is made of foam metal filled with a modified phase change material, wherein the modified phase change material consists of the following components by mass percentage: 98.7-99.3% barium hydroxide octahydrate, 0.2-0.8% nano copper oxide, and 0.5% thickener.

[0008] A composite phase change material is made of foam metal filled with a modified phase change material, wherein the modified phase change material consists of the following components by mass percentage: 99.3% barium hydroxide octahydrate, 0.2% nano copper oxide, and 0.5% thickener.

[0009] Furthermore, the thickener is hydroxyethyl cellulose (HEC).

[0010] Furthermore, the foam metal is foam copper, foam aluminum or foam nickel.

[0011] The method for preparing the composite phase change material comprises the following steps:

[0012] (1) barium hydroxide octahydrate, nano copper oxide, and a thickener are mixed and stirred, ground, placed at 90±5° C., and stirred until completely melted to obtain a modified phase change material;

[0013] (2) placing the foam metal in a mold, pouring the modified phase change material in (1) into the mold until the foam metal is completely filled, sealing it, and letting it stand for a period of time until the phase change material is completely solidified, thereby obtaining a high latent heat and high thermal conductivity composite phase change material.

[0014] Furthermore, in step (1), stirring is performed until the mixture is completely melted, ultrasonication is performed for 60 minutes, and heat preservation is performed for at least 10 minutes to obtain a modified phase change material.

[0015] Compared with the prior art, the present invention has the following significant advantages:

[0016] (1) The addition of nano-metal particles reduces the supercooling of barium hydroxide octahydrate, improves the thermal conductivity and retains the phase change latent heat of barium hydroxide octahydrate. The phase change temperature of the modified phase change material is 77.5℃, the phase change latent heat is 277.3J / g, and the thermal conductivity of the composite phase change material is 12.4W / (m·K).

[0017] (2) The addition of foam metal can not only enhance thermal conductivity but also increase the heat charging and discharging rate.

[0018] (3) The preparation method is simple. Compared with other inorganic hydrated salts, the composite phase change material has the advantages of high thermal conductivity and high latent heat.

[0019] (4) Wide range of applications (phase change temperature 78°C, suitable for application under low temperature conditions). BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the cooling curve of the modified phase change material of the present invention.

[0021] Figure 2 This is the cooling curve of the comparative example of the present invention.

[0022] Figure 3 This is the heating performance parameter curve of the modified phase change material described in the present invention.

[0023] Figure 4 This is a test diagram of the phase change latent heat of the modified phase change materials with different ratios of the present invention.

[0024] Figure 5 This is a scatter plot of thermal conductivity of nano-copper oxide with different components in the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0026] In the modified phase change material of the present invention, the contact angle between the barium hydroxide octahydrate crystal phase and the nano-copper oxide is small, which can reduce the critical nucleation energy of the barium hydroxide octahydrate. The nano-copper oxide uniformly suspended in the melt becomes an inducing factor for the solidification of the melt and does not react with the barium hydroxide octahydrate. The thickener increases the viscosity of the barium hydroxide octahydrate melt, so that the solid particles in the liquid can be more evenly distributed throughout the solution without being deposited at the bottom, thereby basically overcoming the crystal-liquid separation. The modified phase change material basically eliminates the defects such as supercooling and phase separation on the basis of ensuring the high latent heat of the main phase change material barium hydroxide octahydrate. The addition of foam metal provides nucleation sites for barium hydroxide octahydrate to a certain extent and improves the thermal conductivity of the overall phase change material.

[0027] The steps for preparing a composite phase change material of the present invention are as follows:

[0028] S1. Based on the total mass of the modified phase change material of 30 g, 98.7-99.3 wt% of barium hydroxide octahydrate, 0.2-0.8 wt% of nano-copper oxide, and 0.5 wt% of hydroxyethyl cellulose were weighed, stirred, ground evenly, and poured into a centrifuge tube. The mixture was placed in a magnetic stirrer with a water bath temperature of 90°C until the phase change material was completely melted. Ultrasonic dispersion was performed for 60 min, and the mixture was kept warm for 10 min to obtain the modified phase change material.

[0029] S2. Place the foam metal in a mold of matching size, use the modified phase change material in S2 as the phase change matrix, and pour it into the mold until the foam metal is completely filled. Seal it with plastic wrap and tin foil, and let it stand for a while until the phase change material is completely solidified, thus obtaining a high latent heat, high thermal conductivity fixed composite phase change material.

[0030] Examples 1-4

[0031] According to the above step S1, the modified phase change material was prepared with the ratio shown in Table 1, and the thermal performance test was performed on it. The results are as follows: Figure 1 , 3, 4, and 5.

[0032] See Figure 1 In Example 2, the modified phase change material with an addition amount of 0.2% of nano-copper oxide has the best stability and a supercooling degree of 0.5°C.

[0033] See Figure 1 、 3 In Example 2, when the content of nano-copper oxide is 0.2%, the modified phase change material has good stability and the phase change latent heat is 277.3 J / g.

[0034] Table 1

[0035]

[0036] The modified phase change material prepared in Example 2 was filled into foam copper (20 PPI, porosity 98%, Kunshan Guangjiayuan Electronic Materials Co., Ltd.) according to the above step S2 to prepare a composite phase change material. The thermal conductivity of the composite phase change material was measured to be 12.4 W / (m·K).

[0037] Comparative Examples 1-4:

[0038] Based on the total mass of the modified phase change material being 30 g, barium hydroxide octahydrate, nano-copper, and hydroxyethyl cellulose were weighed according to Table 2, mixed, stirred, ground, and evenly poured into a centrifuge tube. The mixture was placed in a magnetic stirrer with a water bath temperature of 90°C until the phase change material was completely melted. Ultrasonic dispersion was performed for 60 minutes, and the mixture was kept warm for 10 minutes to obtain the modified phase change materials of Comparative Examples 1-4.

[0039] Table 2

[0040]

[0041]

[0042] The cooling curve of the modified phase change material is as follows: Figure 2 shown.

Claims

1. A composite phase change material, characterized in that: Made of foam metal filled with modified phase change material, wherein the modified phase change material is composed of the following components by mass percentage: 99.3% barium hydroxide octahydrate, 0.2% nano copper oxide, and 0.5% thickener; The foam metal is foam copper.

2. The composite phase change material according to claim 1, wherein The thickener is hydroxyethyl cellulose.

3. The composite phase change material according to claim 1, wherein The pore size of the foam copper is 20ppi and the porosity is 98%.

4. The method for preparing a composite phase change material according to any one of claims 1 to 3, wherein: The following steps are involved: (1) Mix barium hydroxide octahydrate, nano copper oxide, and thickener, grind, place at 90±5°C, and stir until completely melted to obtain a modified phase change material; (2) Place the foam metal in a mold, pour the modified phase change material in (1) into the mold until the foam metal is completely filled, seal it, and let it stand for a period of time until the phase change material is completely solidified, thereby obtaining a high latent heat and high thermal conductivity composite phase change material.

5. The method according to claim 4, wherein In step (1), stirring is performed until the mixture is completely melted, ultrasonication is performed for 60 minutes, and heat preservation is performed for at least 10 minutes to obtain a modified phase change material.

Images