Preparation method of low-temperature energy storage phase change material
By introducing strontium chloride hexahydrate, ammonium chloride, potassium chloride, and other components into calcium chloride hexahydrate to form a eutectic solution, the problems of supercooling, phase separation, and poor thermal conductivity of calcium chloride hexahydrate are solved, realizing efficient thermal energy storage and stable phase change material applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NINGXIA UNIVERSITY
- Filing Date
- 2026-02-05
- Publication Date
- 2026-05-29
AI Technical Summary
Existing calcium chloride hexahydrate as a phase change material suffers from problems such as overcooling, phase separation, poor thermal conductivity, and corrosion, which limit its large-scale commercial application.
By introducing strontium chloride hexahydrate as a nucleating agent, combined with ammonium chloride and potassium chloride as temperature regulators, using diatomaceous earth and expanded graphite to improve thermal conductivity, and optimizing the component ratio, a transparent and clear eutectic solution is formed, avoiding supercooling and maintaining high latent heat and fluidity.
It significantly reduces supercooling, improves thermal response speed, maintains high latent heat of phase change, broadens the application range, improves thermal conductivity and solves corrosion problems, and the material maintains stability in multiple cycles.
Smart Images
Figure CN122104159A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of low-temperature energy storage phase change material preparation technology, specifically a method for preparing low-temperature energy storage phase change materials. Background Technology
[0002] Phase change materials (PCMs) can absorb or release large amounts of latent heat through phase change processes at near-constant temperatures, thereby achieving the storage and release of thermal energy. They have broad application prospects in building energy conservation, solar energy utilization, industrial waste heat recovery, and agricultural greenhouse temperature control. Based on their chemical composition, PCMs are mainly classified into organic, inorganic, and composite types. Among the many inorganic hydrated salt PCMs, calcium chloride hexahydrate (CaCl26H2O) is considered a highly promising medium- and low-temperature PCM material due to its suitable phase change temperature (approximately 29℃), high latent heat of fusion (approximately 190 kJ / kg), wide availability of raw materials, low price, non-toxicity, and non-flammability. It is particularly suitable for passive building temperature control and temperature buffering in agricultural greenhouses.
[0003] However, despite the aforementioned advantages, calcium chloride hexahydrate alone presents several significant technical drawbacks as a phase change material in practical applications, limiting its large-scale commercial use. While existing technological improvements have alleviated these problems to some extent, they still have shortcomings: 1. Severe Supercooling: During the cooling crystallization process, pure calcium chloride hexahydrate often needs to be cooled to a temperature far below its theoretical freezing point to begin nucleation and crystallization. This supercooling prevents the material from releasing heat in a timely manner within the temperature range where it should release heat, significantly reducing the system's temperature control efficiency and energy utilization. Current Technology: To solve the supercooling problem, current technologies typically add nucleating agents (such as strontium chloride hexahydrate SrCl26H2O, sodium tetraborate, etc.).
[0004] Disadvantages of existing technologies: Although some nucleating agents can effectively reduce supercooling, during long-term thermal cycling, the nucleating agents may agglomerate or settle, leading to a gradual decline in the nucleation effect and a decrease in the cycling stability of the material.
[0005] 2. Phase Separation Problem: Calcium chloride hexahydrate is a semi-uniform melting compound. During melting, it decomposes into liquid calcium chloride tetrahydrate (CaCl₂4H₂O) and excess water. Because the density of calcium chloride tetrahydrate is greater than that of the solution, it easily settles to the bottom of the container. During subsequent cooling and crystallization, the calcium chloride tetrahydrate at the bottom is difficult to recombine with the water in the upper layer to form calcium chloride hexahydrate, leading to an irreversible decrease in the material's heat storage capacity after multiple melt-solidification cycles. Current Technology: To address phase separation, existing technologies often use thickeners (such as sodium carboxymethyl cellulose (CMC), xanthan gum, fumed silica, etc.) to construct a gel network.
[0006] Disadvantages of existing technology: However, the addition of a large amount of thickener often significantly increases the viscosity of the system, resulting in poor material flowability, and organic thickeners are prone to aging and degradation during long-term use; in addition, excessive additives will reduce the overall latent heat value per unit mass of material.
[0007] 3. Poor thermal conductivity and corrosivity: Calcium chloride hexahydrate has a low thermal conductivity, resulting in a slow rate of heat absorption and release, making it unsuitable for applications requiring rapid thermal response. Furthermore, as a chloride salt, it is corrosive to metal containers (such as stainless steel and aluminum), increasing packaging costs and the risk of leakage. Current technology: Currently, adding high thermal conductivity fillers (such as expanded graphite, carbon nanotubes, and metal powders) is commonly used to improve thermal conductivity.
[0008] The drawbacks of existing technologies are that high thermal conductivity fillers are often difficult to disperse uniformly in salt solutions and easily disrupt the network structure constructed by thickeners, leading to instability in the overall performance of the phase change material. In summary, although existing technologies have made some progress in improving the undercooling and phase separation of calcium chloride hexahydrate, a technical solution that can simultaneously achieve low undercooling, high cycling stability, excellent thermal conductivity, and a simple preparation process is still lacking. Therefore, developing a novel calcium chloride hexahydrate-based composite phase change material has significant practical value and market demand. Summary of the Invention
[0009] To solve the above technical problems, the present invention provides the following technical solution: a method for preparing a low-temperature energy storage phase change material, characterized in that, by weight percentage, the phase change material comprises the following components: Calcium chloride hexahydrate: 95%-75%, ammonium chloride: 5%-20%, potassium chloride: 5%-20%, strontium chloride hexahydrate: 1%-5%, surfactant: 1%-7%, diatomaceous earth: 35%-65%, fly ash: 10%-40%, expanded graphite: 10%-40%, emulsifier: 1%-7%, emulsifier: 2%-10%; The specific preparation method is as follows: Weighing: Accurately weigh the following ingredients according to the formula ratio: calcium chloride hexahydrate, ammonium chloride, potassium chloride, strontium chloride hexahydrate, surfactant, diatomaceous earth, fly ash, expanded graphite, emulsifier, and dispersant. Melting: Place calcium chloride hexahydrate in a 250ml beaker and heat it in a 60℃ digital display constant temperature water bath. After it is completely melted, turn on the magnetic stirrer. Mixing: After the system temperature stabilizes, add ammonium chloride, potassium chloride, surfactant, diatomaceous earth, fly ash, expanded graphite, emulsifier, and dispersant to the flask in batches, stir at a constant temperature for 30 minutes, and obtain a transparent and clear eutectic solution. Modification: Add strontium chloride hexahydrate to the above solution, increase the stirring speed to 600 rpm, continue stirring, and then place the flask in an ultrasonic cleaner for ultrasonic degassing at 45°C; Finished product: Stop heating, pour the resulting liquid into a mold, and cool until solidified to obtain a phase change material with adjustable phase change temperature and low supercooling.
[0010] Preferably, the magnetic stirrer is set to a speed of 400 rpm and a stirring time of 0.5 h.
[0011] Preferably, the stirring time during the modification process is 20 minutes and the degassing time is 10 minutes.
[0012] It has the following beneficial effects: 1. This invention introduces strontium chloride hexahydrate as a nucleating agent into the calcium chloride hexahydrate system. Due to the extremely high lattice matching degree (isomorphism) between strontium chloride hexahydrate and calcium chloride hexahydrate, it can serve as a heterogeneous nucleation core, effectively reducing the nucleation barrier. Tests show that, under a cooling rate of 2℃ / min, compared with pure calcium chloride hexahydrate without the addition of a nucleating agent, the supercooling of the phase change material described in this invention is reduced from 15-20℃ to below 1.0-2.0℃. This ensures that the material can rapidly crystallize and release heat when it reaches the set phase change temperature, avoiding the temperature control failure problem caused by excessive supercooling.
[0013] 2. Precise control of phase transition temperature achieved by utilizing the eutectic effect. Addressing the problem that the phase transition temperature of single calcium chloride hexahydrate (approximately 29°C) is fixed and difficult to meet the requirements of specific temperature ranges, this invention utilizes ammonium chloride and potassium chloride as modifiers. By leveraging the eutectic effect of mixed salts, the hydrogen bond network of the original hydrated salt is disrupted, effectively controlling the phase transition temperature to the range of 18°C-22°C. This temperature range is particularly suitable for winter cultivation in solar greenhouses, greatly expanding the application range of the material.
[0014] 3. High latent heat of phase change is maintained. Although temperature regulators and nucleating agents are introduced, this invention optimizes the ratio of each component to maximize the heat storage capacity of the material while adjusting the temperature range. Using differential scanning calorimetry (DSC) testing, at a heating and cooling rate of 5℃ / min and under N2 atmosphere, the latent heat of fusion of the material of this invention is still maintained above 170J / g, which has excellent thermal energy storage density.
[0015] 4. Excellent heat transfer efficiency and flowability: Since this technical solution abandons the traditional high-viscosity organic thickener, the resulting composite material maintains excellent low viscosity characteristics in the liquid state, has good natural convection heat transfer capability, and is easy to fill and encapsulate in various irregularly shaped containers. Attached Figure Description
[0016] Figure 1 This is a flowchart of the preparation method of the transformer substation material of the present invention; Figure 2 This is a DSC curve diagram of the present invention; Figure 3 This is a supercooling curve diagram of the present invention; Figure 4 This is a diagram showing the solidification effect of the phase change material prepared in this invention. Figure 5 This is a diagram showing the effect of melting the phase change material prepared in this invention. Detailed Implementation
[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0018] First embodiment: Please refer to Figures 1-5 The present invention provides a technical solution, comprising the following steps: Step S1: Mix anhydrous calcium chloride and deionized water at a molar ratio of 1:6. Place the mixture in a constant temperature water bath and stir continuously at 500 r / min for 30 min at 60℃ to allow for a full hydration reaction, thereby obtaining a homogeneous and stable calcium chloride hexahydrate solution. After the reaction is complete, seal the solution and place it in a 30℃ constant temperature water bath for later use. Step S2: The calcium chloride hexahydrate obtained in step S1 is used as the main heat storage agent with a mass fraction of 80%-90%; 1%-10% ammonium chloride and 2%-10% potassium chloride are added as temperature regulators. After mixing the above components, the mixture is stirred at 400 r / min for 30 min at 50°C until a completely molten liquid mixture is formed. Testing phase: A series of samples with different mass fractions were prepared, and their DSC curves and cooling curves were tested respectively. The effects of the addition of ammonium chloride and potassium chloride on the phase transition temperature and supercooling of the system were analyzed, and the matrix formulation with the target phase transition temperature was optimized. Step S3: Based on the matrix formulation selected in step S2, add 5%-10% by mass of strontium chloride hexahydrate or strontium hydroxide octahydrate as nucleating agents, and treat for 30 minutes at 50°C and 400 r / min stirring conditions to achieve uniform dispersion of nucleating agents at the molecular or micron level in the phase change material system. Step S4: Perform full-performance thermal analysis on the nucleating agent-containing composite material prepared in step S3. By comparing the DSC data and cooling curves under different types and amounts of nucleating agents, comprehensively examine its melting / solidification behavior, and finally determine the optimal composite phase change material composition that has suitable phase change temperature, high latent heat of phase change and low supercooling.
[0019] Second embodiment: Please refer to Figures 1-5 The present invention provides a technical solution, comprising the following steps: Step S1: Accurately weigh ammonium chloride and potassium chloride in different proportions and dissolve them in a certain amount of deionized water. Stir at 400 r / min for 30 min at 50℃ until a completely molten liquid mixture is formed. Step S2: Mix the solution of ammonium chloride (5%-10%) and potassium chloride (2%-10%) prepared in step S1 with anhydrous calcium chloride at a molar ratio of 6:1. Place the mixture in a constant temperature water bath and stir continuously at 500 r / min for 30 min at 60℃ to completely form a molten liquid mixture. Step S3: Based on the matrix formulation selected in step S2, add 5%-10% by mass of strontium chloride hexahydrate or strontium hydroxide octahydrate as nucleating agents, and treat for 30 min at 50℃ and 400 r / min stirring conditions to achieve uniform dispersion of nucleating agents at the molecular or micron level in the phase change material system. Step S4: Perform full-performance thermal analysis on the nucleating agent-containing composite material prepared in step S3. By comparing the DSC data and cooling curves under different types and amounts of nucleating agents, comprehensively examine its melting / solidification behavior, and finally determine the optimal composite phase change material composition that has suitable phase change temperature, high latent heat of phase change and low supercooling.
[0020] Third embodiment: Please refer to Figures 1-5 The present invention provides a technical solution, comprising the following steps: Step S1: Accurately weigh 5%-10% strontium chloride hexahydrate or strontium hydroxide octahydrate, and treat it at 50℃ and 400r / min for 30min to prepare solutions with different mass fractions; Step S2: Mix anhydrous calcium chloride with the solution prepared in step S1 at a molar ratio of 1:6. Place the mixture in a constant temperature water bath and stir continuously at 500 r / min for 30 min at 60℃ to allow it to undergo a full hydration reaction and obtain a homogeneous and stable matrix solution. Step S3: The matrix obtained in step S2 is used as the main heat storage agent with a mass fraction of 80%-90%; 1%-10% ammonium chloride and 2%-10% potassium chloride are added as temperature regulators. After mixing the above components, the mixture is stirred at 400 r / min for 30 min at 50°C until a completely molten liquid mixture is formed. Step S4: Perform full-performance thermal analysis on the nucleating agent-containing composite material prepared in step S3. By comparing the DSC data and cooling curves under different types and amounts of nucleating agents, comprehensively examine its melting / solidification behavior, and finally determine the optimal composite phase change material composition that has suitable phase change temperature, high latent heat of phase change and low supercooling.
[0021] Summary: Figure 2 As shown, by adding a nucleating agent, the supercooling was significantly reduced and the thermal response rate was improved; like Figure 3 As shown, despite the introduction of temperature regulators and nucleating agents, the present invention maintains a high latent heat of phase change. By optimizing the ratio of each component, the material's heat storage capacity is maximized while adjusting the temperature range. Using differential scanning calorimetry (DSC) testing, the latent heat of fusion of the material of the present invention remains above 170 J / g at a heating / cooling rate of 5 °C / min and in an N2 atmosphere, demonstrating excellent thermal energy storage density.
[0022] Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art and related fields based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described and explained in the present invention, unless otherwise specified or limited, shall be implemented according to conventional means in the art.
Claims
1. A method for preparing a low-temperature energy storage phase change material, characterized in that, The phase change material comprises the following components by weight percentage: Calcium chloride hexahydrate: 95%-75%, ammonium chloride: 5%-20%, potassium chloride: 5%-20%, strontium chloride hexahydrate: 1%-5%, surfactant: 1%-7%, diatomaceous earth: 35%-65%, fly ash: 10%-40%, expanded graphite: 10%-40%, emulsifier: 1%-7%, dispersant: 2%-10%; The specific preparation method is as follows: Weighing: Accurately weigh the following ingredients according to the formula ratio: calcium chloride hexahydrate, ammonium chloride, potassium chloride, strontium chloride hexahydrate, surfactant, diatomaceous earth, fly ash, expanded graphite, emulsifier, and dispersant. Melting: Place calcium chloride hexahydrate in a 250ml beaker and heat it in a 60℃ digital display constant temperature water bath. After it is completely melted, turn on the magnetic stirrer. Mixing: After the system temperature stabilizes, add ammonium chloride, potassium chloride, surfactant, diatomaceous earth, fly ash, expanded graphite, emulsifier, and dispersant to the flask in batches, stir at a constant temperature for 30 minutes, and obtain a transparent and clear eutectic solution. Modification: Add strontium chloride hexahydrate to the above solution, increase the stirring speed to 600 rpm, continue stirring, and then place the flask in an ultrasonic cleaner for ultrasonic degassing at 45°C; Finished product: Stop heating, pour the resulting liquid into a mold, and cool until solidified to obtain a phase change material with adjustable phase change temperature and low supercooling.
2. The method for preparing a low-temperature energy storage phase change material according to claim 1, characterized in that: The magnetic stirrer is set to rotate at 400 rpm and the stirring time is 0.5 h.
3. The method for preparing a low-temperature energy storage phase change material according to claim 1, characterized in that: The stirring time during the modification process is 20 minutes, and the degassing time is 10 minutes.