Composite phase change heat storage material for electric heating floor and preparation method thereof

Abstract

The application discloses a kind of composite phase change heat storage materials for electric heating floor, with solid-solid phase change material as phase change matrix, with heat-conducting reinforcing phase, support skeleton and stabilizer, its material component is as follows by mass percentage: phase change matrix: 40~60%, preferably inorganic salt, or polyethylene glycol or stearic acid is selected;Heat-conducting reinforcing phase: 10~20%, preferably expanded graphite, graphene microsheet or carbon fiber;Support skeleton: 20~40%, preferably graded tailings, or diatomite or cement-based is selected;Stabilizer: 1~5%, preferably high-density polyethylene or silicone rubber.The application has the advantages that the composite phase change heat storage material has high thermal conductivity, high latent heat, stable structure, low cost, green environmental protection, and can realize efficient adaptation with low-voltage electric heating floor heating layer.

Description

Technical Field

[0001] This invention belongs to the technical field of phase change thermal storage materials and electric heating floors, and particularly relates to a composite phase change thermal storage material for electric heating floors and its preparation method. Background Technology

[0002] Low-voltage electric floor heating, with its superior safety performance and convenient installation, is gradually replacing traditional high-voltage electric floor heating and has become an important choice in the building heating field. However, low-voltage electric floor heating has the drawback of "instant heating and instant cooling" in practical applications, especially during peak electricity hours, when continuous power supply leads to a significant increase in heating costs, which seriously restricts its large-scale promotion.

[0003] Phase change thermal storage materials (PCS), as functional materials capable of absorbing or releasing heat at specific temperatures, can effectively solve the energy consumption problem of low-voltage electric floor heating. By storing heat during off-peak hours and releasing it during peak hours, the heating system can achieve "peak shaving and valley filling," reducing heating costs for users and alleviating grid load pressure. Therefore, PCS has become a core component for energy-saving upgrades of low-voltage electric floor heating.

[0004] However, phase change thermal storage materials mostly use paraffin wax as the phase change matrix, which has problems such as low thermal conductivity, easy leakage, and poor structural stability, making it difficult to meet the long-term use requirements of low-voltage electric heating floors. Specifically: (1) Low thermal conductivity: The thermal conductivity of single phase change materials is usually low, resulting in slow heat transfer and poor heat storage and release efficiency. In the application scenarios of low-voltage electric heating floor, it cannot quickly respond to the heating demand of the heating layer, resulting in heat that cannot be stored or released in time, affecting the heating effect and energy efficiency.

[0005] (2) Prone to leakage: Phase change materials are fluid in the molten state. If there is a lack of effective encapsulation or support structure, leakage is likely to occur. Leaking phase change materials will not only contaminate the internal structure of the floor, but may also affect the electrical safety of the floor and shorten its service life.

[0006] (3) Poor structural stability: Single phase change materials lack an effective supporting framework and are prone to deformation after melting, making it impossible to maintain their shape for a long time. This not only damages the structural integrity of the heat storage layer, but also leads to instability in the heat storage and release process, affecting the reliability of the heating system.

[0007] (4) Poor thermal storage performance: Some single phase change materials have low latent heat of phase change and limited thermal storage capacity, making it difficult to achieve continuous heat release during peak power periods. During long peak power periods, they cannot provide stable heat to the room, requiring frequent activation of the heating layer, which leads to increased energy consumption.

[0008] (5) High cost: The preparation of existing phase change thermal energy storage materials mostly relies on pure chemical raw materials without optimization in conjunction with industrial solid waste, resulting in high raw material costs. At the same time, it fails to achieve the dual goals of green environmental protection and solid waste resource utilization, which is inconsistent with national policies and the concept of green development.

[0009] (6) Poor compatibility with the heating layer of the electric heating floor: The bond between the heat storage layer and the heating layer is not tight, resulting in a large thermal resistance and significant heat loss. The heat generated by the heating layer cannot be fully absorbed by the heat storage layer, which not only reduces energy utilization efficiency but may also cause local overheating of the heating layer, affecting its service life. Summary of the Invention

[0010] The purpose of this invention is to solve the problems of low thermal conductivity, poor structural stability, poor heat storage performance, high cost, and insufficient compatibility with low-voltage electric heating floors in existing phase change thermal storage materials. It provides a composite phase change thermal storage material for electric heating floors, which has the advantages of high thermal conductivity, high latent heat, stable structure, low cost, and green environmental protection, and can achieve efficient compatibility with the heating layer of low-voltage electric heating floors.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: A composite phase change thermal storage material for electric heating floors uses solid-solid phase change materials as the phase change matrix, combined with a thermally conductive reinforcing phase, a supporting skeleton, and a stabilizer. By optimizing the compounding ratio, the synergistic improvement of thermal storage, thermal conductivity, and structural stability is achieved.

[0012] The components of the composite phase change thermal storage material, by mass percentage, are: Phase change matrix: 40%~60%, preferably inorganic salts, or polyethylene glycol or stearic acid, to ensure sufficient heat storage capacity and to be suitable for the human body's comfortable temperature range; Thermally conductive reinforcing phase: 10%~20%, preferably expanded graphite, graphene microsheets or carbon fiber, is used to improve the thermal conductivity of the heat storage material to ≥1.5W / (m·K) and accelerate heat transfer; Support skeleton: 20%~40%, preferably graded tailings sand, whose fine powder fills the pores and coarse particles provide structural strength, or diatomaceous earth or cement-based materials can be used to realize the resource utilization of solid waste, while improving the structural stability of the material and preventing structural damage caused by volume changes. Stabilizer: 1%~5%, preferably high-density polyethylene or silicone rubber, used to enhance the compatibility of each component, prevent leakage after the phase change matrix melts, and improve the long-term stability of the material.

[0013] Furthermore, the solid-solid phase change material has a phase change temperature of 45~55℃ and a latent heat of phase change ≥180J / g.

[0014] Furthermore, the composite phase change thermal storage material is composed of the following components by mass percentage: 50% solid-solid phase change material, 15% graphene micro-sheets, 30% graded tailings sand, and 5% high-density polyethylene.

[0015] Furthermore, the composite phase change thermal storage material is composed of the following components by mass percentage: 60% solid-solid phase change material, 10% graphene micro-flakes, 28% graded tailings sand, and 2% high-density polyethylene.

[0016] Furthermore, the composite phase change thermal storage material is composed of the following components by mass percentage: 40% solid-solid phase change material, 20% expanded graphite, 38% graded tailings sand, and 2% silicone rubber.

[0017] To further achieve the objective of this invention, a method for preparing a composite phase change thermal storage material for electric heating floors is also provided, the specific steps of which are as follows: S1, Raw material pretreatment: The phase change matrix is ​​heated to 42~45℃ to induce a phase change; the thermally conductive reinforcing phase is dried and dispersed to prevent agglomeration; the supporting skeleton is dried and sieved to remove impurities and control the moisture content to ≤1%; S2, thermally conductive enhanced phase dispersion: The phase change matrix of the solid-solid phase change material is placed in a stirring device, the thermally conductive enhanced phase is added, and the mixture is stirred at high speed for 20-30 minutes to ensure that the thermally conductive enhanced phase is uniformly dispersed in the phase change matrix and to improve the overall thermal conductivity. S3, Mixing the support skeleton and stabilizer: Add the pretreated support skeleton and stabilizer to the above mixing system, adjust the stirring speed to medium speed, and stir for 15~25 minutes to make the support skeleton and stabilizer evenly dispersed to form a stable composite system; S4, Casting into mold: Pour the evenly mixed slurry into the preset mold. The mold size is adapted to the heat storage layer requirements of the low-pressure electric heating floor. The casting thickness is controlled to be 15~18mm. S5, Cooling and solidification: Place the mold after casting in a normal temperature environment and allow it to cool naturally to room temperature so that the slurry is completely solidified. After demolding, the composite phase change thermal storage material product can be obtained. S6, Encapsulation: The finished product is encapsulated with aluminum foil or metal film to prevent paraffin penetration. At the same time, it acts as a reflective layer to reflect heat upwards, reducing heat loss and improving heat storage and release efficiency.

[0018] Furthermore, in steps S1 to S5, the prepared product has a thermal conductivity ≥1.5W / (m·K) and a thickness controlled to be 15~18mm.

[0019] Compared with the prior art, the advantages of the technical solution of the present invention are as follows: (1) By adding thermally conductive reinforcing phases such as graphene microsheets and expanded graphite, the thermal conductivity of the heat storage material is increased to more than 1.5 W / (m·K), which accelerates heat transfer, realizes rapid heat storage and release, and is suitable for the heating requirements of low-voltage electric heating floor. (2) The present invention uses paraffin with a latent heat of phase change ≥180J / g as the phase change matrix. It has sufficient heat storage capacity and can store a large amount of heat during off-peak hours at night and release it slowly during peak hours during the day. Combined with a low-voltage heating system, it can reduce operating electricity costs by 30%~50%, and is especially suitable for areas with large peak-valley electricity price differences. (3) The present invention uses graded tailings sand as a support skeleton and is combined with stabilizers such as high-density polyethylene, which effectively avoids the structural damage and deformation caused by the volume change of phase change material. It has strong structural stability and can be used stably for a long time. (4) This invention uses tailings sand as a supporting framework to realize the high-value utilization of industrial solid waste, reduce resource waste and solid waste landfill volume, which is in line with policy; at the same time, it optimizes the component ratio, significantly reduces raw material costs, and facilitates large-scale promotion. (5) The thickness of the heat storage material of the present invention is controlled at 5~8mm, which can be closely bonded to the 15mm thick graphene-carbon fiber composite conductive heating layer. There is no air layer, the heat loss is small, and the heat generation-heat storage-heat release are integrated, which is compatible with the modular structure of low-voltage electric heating floor. (6) The preparation process of the present invention is simple and convenient, requires no complex equipment, can achieve large-scale production, and the preparation process has no pollutant emissions, is green and environmentally friendly, and has low production costs. Detailed Implementation Example 1

[0020] To make the present invention clearer, the following description further illustrates a composite phase change thermal storage material for electric heating floors and its preparation method. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the present invention.

[0021] This embodiment provides a composite phase change heat storage material for electric heating floors, the material composition by mass percentage is as follows: 50% solid-solid phase change material, phase change temperature 50℃, latent heat of phase change 185J / g; 15% graphene micro-sheets; 30% graded tailings sand; 5% high-density polyethylene.

[0022] The preparation method of the above-mentioned composite phase change thermal storage material for electric heating floors is as follows: S1, Raw material pretreatment: The solid-solid phase change material is heated to 45℃ to induce a phase change; the graphene microsheets are dried and dispersed to prevent agglomeration; the supporting framework is dried and sieved to remove impurities, and the moisture content is controlled to be ≤1%. S2, thermally conductive enhancement phase dispersion: The molten phase change matrix is ​​placed in a stirring device, the thermally conductive enhancement phase is added, and the mixture is stirred at high speed for 25 minutes to ensure that the thermally conductive enhancement phase is uniformly dispersed in the phase change matrix and to improve the overall thermal conductivity. S3, Mixing the support skeleton and stabilizer: Add the pretreated support skeleton and stabilizer to the above mixture, adjust the stirring speed to medium speed, stir for 20 minutes to make the support skeleton and stabilizer evenly dispersed and form a stable composite system; S4, Casting into mold: The evenly mixed slurry is poured into a preset mold. The mold size is adapted to the heat storage layer requirements of the low-pressure electric heating floor, and the casting thickness is controlled to be less than 20mm. S5, Cooling and Curing: Place the mold after casting in a normal temperature environment and allow it to cool naturally to room temperature so that the slurry is completely cured. After demolding, the composite phase change thermal storage material product can be obtained.

[0023] Testing revealed that the finished product has a thermal conductivity of 1.8 W / (m·K), exhibits no leakage, and has sufficient heat storage capacity. It can stably store and release heat at around 42℃, making it suitable for residential, office building, and other civilian low-voltage electric heating floor applications. Example 2

[0024] This embodiment provides a composite phase change thermal storage material for electric heating floors, the material composition by mass percentage is as follows: 60% solid-solid phase change material, phase change temperature 50℃, latent heat of phase change 200J / g; 10% graphene micro-sheets; 28% graded tailings sand; 2% high-density polyethylene.

[0025] The preparation method of the above-mentioned composite phase change thermal storage material for electric heating floors is as follows: S1, Raw material pretreatment: Paraffin wax is heated to 45℃ to induce a phase change; graphene microsheets are dried and dispersed to prevent agglomeration; the supporting framework is dried and sieved to remove impurities, and the moisture content is controlled to ≤1%; S2, thermally conductive enhancement phase dispersion: The molten phase change matrix is ​​placed in a stirring device, the thermally conductive enhancement phase is added, and the mixture is stirred at high speed for 25 minutes to ensure that the thermally conductive enhancement phase is uniformly dispersed in the phase change matrix and to improve the overall thermal conductivity. S3, Mixing the support skeleton and stabilizer: Add the pretreated support skeleton and stabilizer to the above mixture, adjust the stirring speed to medium speed, stir for 20 minutes to make the support skeleton and stabilizer evenly dispersed and form a stable composite system; S4, Casting into mold: The evenly mixed slurry is poured into a preset mold. The mold size is adapted to the heat storage layer requirements of the low-pressure electric heating floor, and the casting thickness is controlled to be less than 20mm. S5, Cooling and Curing: Place the mold after casting in a normal temperature environment and allow it to cool naturally to room temperature so that the slurry is completely cured. After demolding, the composite phase change thermal storage material product can be obtained.

[0026] Testing revealed that the finished product has a thermal conductivity of 1.5 W / (m·K), exhibits no leakage, and has a larger heat storage capacity, classifying it as a high-heat-storage type suitable for low-voltage electric heating floor scenarios in cold regions with high heat storage requirements. Example 3

[0027] This embodiment provides a composite phase change heat storage material for electric heating floors, the material composition by mass percentage is as follows: 40% solid-solid phase change material, phase change temperature 45℃, latent heat of phase change 185J / g; 20% expanded graphite; 38% graded tailings sand; 2% silicone rubber.

[0028] The preparation method of the above-mentioned composite phase change thermal storage material for electric heating floors is as follows: S1, Raw material pretreatment: The solid-solid phase change material is heated to 45℃ to induce a phase change; the expanded graphite is dried and dispersed to prevent agglomeration; the support skeleton is dried and sieved to remove impurities, and the moisture content is controlled to be ≤1%. S2, thermally conductive enhancement phase dispersion: The molten phase change matrix is ​​placed in a stirring device, the thermally conductive enhancement phase is added, and the mixture is stirred at high speed for 25 minutes to ensure that the thermally conductive enhancement phase is uniformly dispersed in the phase change matrix and to improve the overall thermal conductivity. S3, Mixing the support skeleton and stabilizer: Add the pretreated support skeleton and stabilizer to the above mixture, adjust the stirring speed to medium speed, stir for 20 minutes to make the support skeleton and stabilizer evenly dispersed and form a stable composite system; S4, Casting into mold: The evenly mixed slurry is poured into a preset mold. The mold size is adapted to the heat storage layer requirements of the low-pressure electric heating floor, and the casting thickness is controlled to be less than 20mm. S5, Cooling and Curing: Place the mold after casting in a normal temperature environment and allow it to cool naturally to room temperature so that the slurry is completely cured. After demolding, the composite phase change thermal storage material product can be obtained.

[0029] Testing revealed that the prepared product has a thermal conductivity of 2.0 W / (m·K), exhibits no leakage, and demonstrates higher thermal conductivity. The material cost is 10% lower than that of Example 1, making it a low-cost option suitable for cost-sensitive low-voltage electric heating floor applications such as factories and warehouses.

[0030] In summary, the composite phase change thermal storage material of the present invention not only has high thermal conductivity and excellent thermal storage performance, but also has a stable structure and no deformation. At the same time, it reduces costs and is more environmentally friendly. It is suitable for the preparation of thermal storage layers for low-voltage electric heating floors, and can realize off-peak electricity thermal storage and peak electricity thermal release. It is especially suitable for areas with large peak-valley electricity price differences and can be widely used in various building heating scenarios.

[0031] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A composite phase change thermal storage material for electric heating floors, characterized in that: Using solid-solid phase change materials as the phase change matrix, combined with thermally conductive reinforcing phases, supporting frameworks, and stabilizers, the material composition by mass percentage is as follows: Phase change matrix: 40%~60%, preferably inorganic salts, or polyethylene glycol or stearic acid; Thermally conductive reinforcing phase: 10%~20%, preferably expanded graphite, graphene microsheets or carbon fiber; Support frame: 20%~40%, preferably graded tailings sand, or diatomaceous earth or cement-based materials; Stabilizer: 1%~5%, preferably high-density polyethylene or silicone rubber.

2. The composite phase change thermal storage material for electric heating floors according to claim 1, characterized in that: The solid-solid phase change material has a phase change temperature of 45~55℃ and a latent heat of phase change ≥180J / g.

3. The composite phase change thermal storage material for electric heating floors according to claim 2, characterized in that: The composite phase change thermal storage material is composed of the following components by mass percentage: 50% solid-solid phase change material, 15% graphene microsheets, 30% graded tailings sand, and 5% high-density polyethylene.

4. The composite phase change thermal storage material for electric heating floors according to claim 2, characterized in that: The composite phase change thermal storage material is composed of the following components by mass percentage: 60% solid-solid phase change material, 10% graphene micro-flakes, 28% graded tailings sand, and 2% high-density polyethylene.

5. The composite phase change thermal storage material for electric heating floors according to claim 2, characterized in that: The composite phase change thermal storage material is composed of the following components by mass percentage: 40% solid-solid phase change material, 20% expanded graphite, 38% graded tailings sand, and 2% silicone rubber.

6. A method for preparing a composite phase change thermal storage material for electric heating floors as described in claim 2, characterized in that: S1, Raw material pretreatment: The phase change matrix is ​​heated to 42~45℃ to induce a phase change; the thermally conductive reinforcing phase is dried and dispersed to prevent agglomeration; the supporting skeleton is dried and sieved to remove impurities and control the moisture content to ≤1%; S2, thermally conductive enhanced phase dispersion: Place the solid-solid phase change matrix into a stirring device, add the thermally conductive enhanced phase, and stir at high speed for 20-30 minutes to make the thermally conductive enhanced phase uniformly dispersed in the phase change matrix; S3, Mixing the support skeleton and stabilizer: Add the pretreated support skeleton and stabilizer to the above mixing system, adjust the stirring speed to medium speed, and stir for 15~25 minutes to make the support skeleton and stabilizer evenly dispersed to form a stable composite system; S4, Casting into mold: Pour the evenly mixed slurry into the preset mold. The mold size is adapted to the heat storage layer requirements of the low-pressure electric heating floor. The casting thickness is controlled to be 15~18mm. S5, Cooling and solidification: Place the mold after casting in a normal temperature environment and allow it to cool naturally to room temperature so that the slurry is completely solidified. After demolding, the composite phase change thermal storage material product can be obtained. S6, Packaging: The finished product is packaged using aluminum foil or metal film.

7. The method for preparing the composite phase change thermal storage material for electric heating floors according to claim 6, characterized in that: In steps S1 to S5, the prepared product has a thermal conductivity ≥1.5W / (m·K) and a thickness controlled to be 5~8mm.