CN102408878B - Phase change energy storage material - Google Patents

Abstract

The invention discloses a phase change energy storage material, which comprises: Antarctica, a nucleating agent, a thickening agent and a heat conducting agent, wherein the nucleating agent is barium sulfate and strontium chloride hexahydrate. Compared with the prior art, the present invention uses barium sulfate and strontium chloride hexahydrate as nucleating agents. Since the nucleating agent matches the crystal structure characteristics, lattice parameter size, physical properties and other aspects of Antarctica, In addition, thickeners and other components are added together to solve the problem of large undercooling of phase change energy storage materials in the prior art. At the same time, since Antarctica has a large latent heat of phase change, the phase change energy storage material also has the characteristics of large latent heat of phase change. Experimental results show that the supercooling degree of the phase change energy storage material prepared by the present invention is only 0.4°C.

Description

Phase Change Energy Storage Materials

technical field

The invention relates to the technical field of energy storage materials, and more specifically, to a phase change energy storage material.

Background technique

Phase change energy storage materials are one of the hotspots in the development and research of energy utilization and material science at home and abroad in recent years. Phase change energy storage, also known as latent heat energy storage, is a material that uses phase change latent heat to store energy at a constant temperature. The heat storage/discharge is carried out by using energy, and the characteristics are: high heat storage density, heat storage/release process is carried out under constant temperature conditions, and the heat storage/release rate is controllable. In the above-mentioned heat storage/release process, the phase change material is the medium that realizes the phase change heat storage. When the temperature is higher than the phase change point, it absorbs heat so that the phase change occurs, that is, the heat storage process of melting; when the temperature drops below the phase change point At this point, a reverse phase transition occurs, that is, an exothermic process of solidification. The temperature of the surrounding environment can be adjusted by using the heat storage and heat release functions of phase change materials. Therefore, phase change energy storage materials have broad prospects in the fields of building heating and air conditioning. For building heating, on the one hand, phase change energy storage materials can alleviate the contradiction between energy supply and demand in terms of time, intensity and location, play a role in shifting peaks and filling valleys, and reduce the operation and maintenance costs of air conditioning or heating systems; on the other hand On the one hand, it can reduce temperature fluctuations in buildings and improve indoor comfort. In addition, phase-change energy storage materials are used in floor heating, which can also store excess energy and wait until the energy supply is intermittent.

Antarcticite is a natural mineral discovered in Antarctica in 1965 and named after it. The chemical composition of Antarctica is CaCl ₂ 6H ₂ O, the crystal structure is trigonal, the space group P321 has stable physical and chemical properties, the density is 1.7g/cm ³ , the hardness is 2-3, the glass luster, the cleavage {0001 } Complete, X-rays can produce diffraction and so on. It is worth emphasizing that the melting point of Antarctica is around 29°C. Above this temperature, Antarctica exists in the form of an amorphous liquid, while below this temperature it crystallizes into a colorless and transparent crystal and releases a lot of heat ( About 170-190kJ/kg). This characteristic of Antarctica actually provides us with a good example of natural phase change energy storage. At present, calcium chloride hexahydrate is the most researched phase-change energy storage material, which is actually a concrete manifestation of the practical application of Antarctica. For example, the literature [Li Zhiguang, Xu Lei, Huang Hongjun, etc. Research on phase change constant temperature material calcium chloride hexahydrate. Functional Materials, 2007, 38 (Supplement): 3162-3163.] studied a phase change energy storage material, The material uses barium hydroxide as a nucleating agent and the inorganic phase-change material calcium chloride hexahydrate, and uses the step cooling curve method to measure the hexahydrate when adding barium hydroxide with mass fractions of 1.0%, 2.0% and 3.0%. For the phase transition temperature of calcium chloride hydrate, the measurement results show that when the addition of 3.0% barium hydroxide is added, the phase transition effect is better, and the phase transition temperature is 28.10°C. In the literature [Wang Fang, Zheng Maoyu, Li Zhongjian, etc., Numerical Simulation of Thermal Storage Process of Solar Heat Pump Thermal Storage System. Acta Solaris Sinica, 2007.128(14): 411-415], the package container containing calcium chloride hexahydrate phase change material Put it into a solar water tank to store heat, and establish a phase change heat transfer model based on this. Through the comparison and analysis of the experimental results and simulation results, the temperature of the inlet and outlet of the heat storage tank, the temperature of the phase change material, and the storage and release of the water tank and other parameters change. The trend matches.

In addition, the literature [Liu Dong, Xu Yunlong. Effects of nucleating agents on the energy storage performance of calcium chloride hexahydrate phase change materials, Acta Solar Sinica, 2007, 28(7): 732-738] and the literature [Xu Yunlong, Liu Dong .Research on supercooling properties of calcium chloride hexahydrate phase change materials. Materials Engineering, 2006, Suppl. The heat storage performance of the composite system of borax, strontium chloride hexahydrate, Ba(OH) ₂ 8H ₂ O and other nucleating agents and calcium chloride hexahydrate under different working conditions, but the phase change energy storage materials obtained in the above literature research The degree of supercooling is large.

Contents of the invention

In view of this, the technical problem to be solved by the present invention is to provide a phase change energy storage material, which has a large latent heat of phase change and a small degree of supercooling.

In order to solve the above technical problems, the present invention provides a phase change energy storage material, including:

Antarctic stone, nucleating agent, thickener and heat conducting agent, the nucleating agent is barium sulfate and strontium chloride hexahydrate.

Preferably, the mass ratio of barium sulfate to strontium chloride hexahydrate is 1: (1.5-4).

Preferably, the mass ratio of barium sulfate to strontium chloride hexahydrate is 1: (2-3).

Preferably, 1.5wt%-2wt% nucleating agent is included.

Preferably, the thickener is hydroxyethyl cellulose and carboxymethyl cellulose.

Preferably, the thickener is hydroxyethyl cellulose and carboxymethyl cellulose with a mass ratio of (1-2):(1-2).

Preferably, 0.2wt%-0.3wt% thickener is included.

Preferably, 0.1wt% of heat conducting agent is included, and the heat conducting agent is white graphite.

Preferably, 5wt%-10wt% of temperature regulator is also included, and the temperature regulator is ammonium chloride and magnesium hydroxide.

Preferably, the mass ratio of ammonium chloride to magnesium hydroxide is 4:1.

The invention provides a phase change energy storage material, comprising: Antarctica, a nucleating agent, a thickening agent and a heat conducting agent, wherein the nucleating agent is barium sulfate and strontium chloride hexahydrate. Compared with the prior art, the present invention uses barium sulfate and strontium chloride hexahydrate as nucleating agents. Since the nucleating agent matches the crystal structure characteristics, lattice parameter size, physical properties and other aspects of Antarctica, In addition, thickeners and other components are added together to solve the problem of large undercooling of phase change energy storage materials in the prior art. At the same time, since Antarctica has a large latent heat of phase change, the phase change energy storage material also has the characteristics of large latent heat of phase change. Experimental results show that the supercooling degree of the phase change energy storage material prepared by the present invention is only 0.4°C.

Description of drawings

Fig. 1 is the cooling curve of the phase change energy storage material prepared in Example 1 of the present invention;

Fig. 2 is the cooling curve of the phase change energy storage material prepared in Example 2 of the present invention;

Fig. 3 is the cooling curve of the phase change energy storage material prepared in Example 3 of the present invention;

Fig. 4 is the cooling curve of the pure Antarctic rock provided in Comparative Example 1 of the present invention.

Detailed ways

The following clearly and completely describes the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

The invention discloses a phase change energy storage material, comprising:

Antarctica (CaCl ₂ ·6H ₂ O), a nucleating agent, a thickener and a heat conducting agent, the nucleating agent being barium sulfate and strontium chloride hexahydrate (SrCl ₂ ·6H ₂ O).

Antarcticite is a natural mineral discovered in Antarctica in 1965 and named after it. The chemical composition of Antarctica is CaCl ₂ ·6H ₂ O, the crystal structure is trigonal, and the space group is P321. Antarctica has stable physical and chemical properties, with a density of 1.7g/cm ³ , a hardness of 2-3, glass luster, complete cleavage of {0001}, and diffraction of X-rays. It is worth emphasizing that the melting point of Antarctica is around 29°C. Above this temperature, Antarctica exists in the form of an amorphous liquid, while below this temperature it crystallizes into a colorless and transparent crystal and releases a lot of heat ( About 170-190kJ/kg). In the above technical solution, Antarctica has an appropriate melting point and high energy storage capacity, and is an important inorganic heat storage material. Therefore, the present invention uses Antarctica as a heat storage medium. The present invention can use commercially available artificially synthesized Antarctica, and there is no special limitation on its manufacturer and model, or it can be prepared according to methods well known to those skilled in the art.

However, due to the very serious "overcooling" phenomenon in the pure Antarctica energy storage medium. The so-called "supercooling" phenomenon refers to the phenomenon that the liquid substance does not crystallize when it is cooled to the "freezing point", but needs to be cooled to a certain temperature below the "freezing point" to start to crystallize. The supercooling phenomenon is an inherent phenomenon of liquid-solid conversion. And take supercooling as the driving force of crystallization. Since the Antarctic rock heat storage medium used in the present invention has a "supercooling" phenomenon, this phenomenon will affect the performance and service life of the phase change energy storage material, which is a very unfavorable factor. Therefore, the present invention adopts the "addition nucleating agent "Method", by using barium sulfate and strontium chloride hexahydrate as nucleating agents, according to the non-uniform nucleation mechanism, the number of nucleates is increased, and the degree of supercooling is effectively reduced. Due to the matching of barium sulfate, strontium chloride hexahydrate and Antarctica in terms of crystal structure characteristics, lattice parameter size, physical properties, etc., and with the addition of thickener and other ingredients, it solves the problem of phase change energy storage in the prior art The problem of large material supercooling. The mass ratio of the barium sulfate to strontium chloride hexahydrate is preferably 1: (1.5-4), more preferably 1: (2-3), more preferably 1:2; the phase-change energy storage material preferably includes 1.5 wt% to 2 wt% nucleating agent, more preferably including 2 wt% nucleating agent.

Another obvious disadvantage of Antarctica as a phase change medium material is its "precipitation" phenomenon. When Antarctica is heated, it usually transforms into another type of inorganic salt compound of CaCl ₂ ·pH ₂ O containing less mole of water, and CaCl ₂ ·pH ₂ O will be partially or completely dissolved in the remaining (6-p) molar water. During heating, some brine mixtures become anhydrous salts and can be completely or partially dissolved in the water of crystallization. If the solubility of the salt is high, the inorganic brine mixture can be completely dissolved when heated above the melting point; but if the solubility is not high, some salts are still in an undissolved state even if heated above the melting point. At this time, the residual solid The substance sinks to the bottom of the container due to its high density. The precipitation of residual salt causes the crystal liquid to separate, and it cannot recombine with its crystal water to form a uniform original Antarctica. At the end of the cooling process, the energy storage material in the container forms three layers: a bottom layer of undissolved solids, a middle layer of crystallized hydrated salt crystals, and a top layer of a solution layer. This phenomenon will lead to the deterioration of the phase change energy storage performance, and the phase change energy storage capacity will be lost after a certain thermal cycle. For the above-mentioned technical problems, the phase change energy storage material of the present invention includes a thickener, and the purpose of the thickener (or called a suspending agent) is exactly to enhance the viscosity of the solution, so that the solid particles or crystal nuclei in the solution can be evenly distributed in the solution. Stratification occurs without the influence of gravity. The thickener that the present invention adopts is preferably hydroxyethyl cellulose and carboxymethyl cellulose, wherein, the mass ratio of described hydroxyethyl cellulose and carboxymethyl cellulose is preferably (1～2): (1～2) 2), more preferably 1:1; in addition, the phase change energy storage material preferably includes 0.2wt%-0.3wt% thickener.

At the same time, the thermal conductivity of inorganic hydrated salt Antarctica as a phase change energy storage material is relatively poor. Therefore, the present invention increases thermal conductivity without affecting its energy storage performance by adding a heat conducting agent, so as to facilitate its heat storage and heat improvement in practical applications, that is, to increase its heat conversion efficiency. The heat conducting agent in the present invention is preferably white graphite (BN); the phase change energy storage material preferably includes 0.1wt%-0.2wt% heat conducting agent, more preferably 0.1wt% heat conducting agent.

In addition, the present invention also preferably includes a temperature regulator, the temperature regulator is preferably ammonium chloride and magnesium hydroxide, and the mass ratio of the temperature regulator to the phase-change energy storage material for floor heating is preferably (5-10 ): 100, more preferably (6-9): 100, more preferably (7-8): 100. Ammonium chloride and magnesium hydroxide form a eutectic system with antarctica, changing the melting point of pure antarctica during cooling.

The phase-change energy storage material provided by the present invention is preferably prepared according to the following method: heat the Antarctica to 40-50°C, then add a nucleating agent while stirring, continue to add a thickener after the nucleating agent is completely dissolved, and stir evenly Add a heat conducting agent, then add a temperature regulator according to the phase change temperature requirements of the required phase change energy storage material, and obtain a phase change energy storage material after cooling down.

The melting point of heat storage medium Antarctica is about 29°C, and the latent heat of phase change is about 190kJ/kg. Among them, the melting point of the preferred additive strontium chloride hexahydrate is 115°C, and the melting point of barium sulfate is as high as 1600°C. In addition, the preferred additive The thickener hydroxyethyl cellulose and carboxymethyl cellulose are not crystals, and their softening temperature is above 100°C. The melting point of the above-mentioned additives is much higher than that of Antarctica. The influence of the latent heat of phase change of the material is relatively small. Therefore, the phase change energy storage material provided by the present invention is guaranteed to have relatively high phase change latent heat.

In order to further illustrate the technical solution of the present invention, the preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

The chemical reagents used in the examples of the present invention are all commercially available.

Example 1

Put 400g of calcium chloride crystalline hydrate into a 500ml beaker and heat to 40°C, then add 2g of barium sulfate and 4g of strontium chloride hexahydrate as nucleating agents while stirring, and continue to add 0.4g after the nucleating agents are completely dissolved Carboxymethyl cellulose and 0.4g hydroxyethyl cellulose, after stirring evenly, add 0.4g white graphite, after the white graphite is added and completely dissolved, the temperature is lowered and cooled to obtain a phase change energy storage material, which is put into a plastic container as a finished product to be prepared. use.

Perform performance measurement on the phase change energy storage material prepared in this embodiment:

The temperature drop method is used to test the phase change energy storage material, and the paperless recorder records the temperature, specifically:

The phase-change energy storage material prepared in this example was heated to 60°C, then put into a test bottle, a thermocouple was inserted into the test bottle, and the temperature was lowered in a freezer at the same time, and the cooling curve shown in Figure 1 was obtained. It can be seen from Figure 1 that the phase change energy storage material prepared in this example begins to crystallize when it is supercooled to 28.9°C, and the temperature rises to 29.5°C, and the phase change temperature is kept at a constant temperature of 29.5°C. In the solid state, the temperature begins to drop slowly, and the supercooling degree of the phase change energy storage material is only 0.6°C, which basically eliminates the supercooling degree.

Example 2

Put 400g of Antarctica into a 500ml beaker and heat to 50°C, then add 2g of barium sulfate and 4g of strontium chloride hexahydrate as nucleating agents while stirring, and continue to add 0.4g of carboxymethyl fiber after the nucleating agents are completely dissolved Add 0.4g of white graphite and 0.4g of hydroxyethyl cellulose, stir evenly, then add 16g of ammonium chloride and 4g of magnesium hydroxide, cool down and cool down after the addition of the additives is completed and completely dissolved, and a phase change energy storage material is obtained. Put it into a plastic container to become a finished product for use.

The same method as in Example 1 was used to measure the performance of the phase change energy storage material prepared in this example. Figure 2 is the cooling curve of the phase change energy storage material prepared in this example. It can be seen from the figure that the phase change energy storage material The energy storage material starts to crystallize when it is supercooled to 23.8°C, the temperature rises to 24.5°C, and the phase transition temperature is kept at a constant temperature of 24.5°C. The degree of supercooling is only 0.7°C, basically eliminating the degree of supercooling, and the phase transition temperature is reduced to 24.5°C.

Example 3

Put 400g of Antarctica into a 500ml beaker and heat to 45°C, then add 3g of barium sulfate and 6g of strontium chloride hexahydrate while stirring, and continue to add 0.6g of carboxymethylcellulose and 0.6g of Hydroxyethyl cellulose, after stirring evenly, add 0.4g of white graphite, after the addition of additives is completed and completely dissolved, the temperature is lowered and cooled to obtain a phase change energy storage material, which is put into a plastic container to become a finished product for use.

The same method as in Example 1 was used to measure the performance of the phase-change energy storage material prepared in this example. The phase-change energy storage material was heated to 40° C., put into a freezer and started to cool, and the liquid cooled rapidly. As shown in Figure 3, the cooling curve of the phase-change energy storage material prepared for this example, it can be seen from the figure that the phase-change energy storage material begins to crystallize when it is supercooled to 28.9°C, and the temperature rises to 29.1°C, and the phase change The temperature has been kept at a constant temperature of 29.1-29.3°C. After the phase transition is over, all the liquids turn into solids, and the temperature begins to drop slowly. The supercooling degree of the phase change energy storage material is only 0.4°C, and the supercooling degree basically does not exist.

Comparative example 1

After heating pure Antarctica to 47°C, all of it becomes liquid, and then put it into the freezer to start cooling, and measure its supercooling degree. The cooling curve of pure Antarctica is shown in Figure 4. It can be seen from the figure that pure Antarctica begins to crystallize when it is supercooled to 12.8°C, and the temperature rises rapidly to 29.6°C. After the end, all the liquids turned into solids, the temperature began to drop slowly, and the supercooling degree of Antarctica reached 16.8°C.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (4)

1. a phase-changing energy storage material comprises:

The thermal conducting agent of the nucleator of Antarctic Rock, 1.5wt%～2wt%, the thickening material of 0.2wt%～0.3wt%, 0.1wt% and the temperature regulato of 5wt%～10wt%, described nucleator is barium sulfate and six water strontium chlorides;

The mass ratio of described barium sulfate and six water strontium chlorides is 1:(1.5～4);

Described thickening material is Natvosol and carboxymethyl cellulose;

Described thermal conducting agent is white graphite;

Described temperature regulato is ammonium chloride and magnesium hydroxide.

2. phase-changing energy storage material according to claim 1, is characterized in that, the mass ratio of described barium sulfate and six water strontium chlorides is 1:(2～3).

3. phase-changing energy storage material according to claim 1, is characterized in that, the mass ratio that described thickening material is Natvosol and carboxymethyl cellulose is (1～2): (1～2).

4. phase-changing energy storage material according to claim 1, is characterized in that, the mass ratio of described ammonium chloride and magnesium hydroxide is 4:1.

Images