A graphene electrically heated solid wood composite energy storage floor

Abstract

A new graphene-based electrically heated solid wood composite energy storage flooring offers a superior and safer user experience while maintaining the performance of traditional electrically heated floors. Its low-temperature heating and temperature regulation system further reduces energy consumption, offering a new approach to green home living. The flooring features a three-layer structure, with a base layer laminated to a graphene heat dissipation layer, which utilizes fins to enhance heat transfer efficiency. Simulations and experiments determine the time it takes for the floor surface to heat to a comfortable human temperature and the time it takes for the floor to cool down. This allows for simple timer control of the floor's heating. Finally, experimental comparisons confirm the floor's excellent thermal storage performance, demonstrating its practical value.

Description

Technical Field

[0001] The present invention belongs to the field of solid wood composite flooring, and in particular relates to a graphene electrically heated solid wood composite energy storage flooring. Background Art

[0002] Engineered wood flooring is a tongue-and-groove flooring system made with solid wood panels or veneer as the top layer, a solid wood core layer, and a veneer base layer. The species of the wood used in the top layer is often used to identify the flooring. Unlike so-called "composite flooring" on the market, engineered wood flooring is made by interlacing and laminating planks of different wood species. This overcomes the unidirectional, isotropic nature of solid wood flooring, offering minimal shrinkage and swelling, excellent dimensional stability, and retaining the natural wood grain and comfortable feel of solid wood flooring. Engineered wood flooring combines the stability of laminate flooring with the aesthetics of solid wood flooring, offering significant environmental advantages. While maintaining the traditional electrically heated flooring, it provides users with a higher quality, safer, and more comfortable living experience. At the same time, its low-temperature heating and temperature regulation system further reduces energy consumption, offering a new approach to green home living.

[0003] Solid wood composite electric heated floors are an emerging heating method. They utilize a more efficient heat conduction method and an energy-saving, intelligent feedback control system, making them a suitable primary heat source for indoor heating. However, existing conventional electric heated floors suffer from low thermal efficiency, fluctuating surface temperatures, and poor energy storage. Furthermore, traditional electric heated floors are unable to adjust their temperature autonomously and are prohibitively expensive. Summary of the Invention

[0004] In order to solve the above-mentioned problems existing in the background technology, the present invention provides a graphene electrically heated solid wood composite energy storage floor.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A graphene electrically heated solid wood composite energy storage floor, comprising, from top to bottom, a floor surface layer, a base material layer, and a floor bottom layer;

[0007] The lower surface of the substrate layer is processed with a groove with a depth of 2 mm, and an asbestos mesh heat-insulating layer is provided in the groove;

[0008] The lower surface of the floor surface layer is provided with a groove, the upper surface of the base material layer is provided with a groove, and the two grooves are matched with a graphene heat dissipation layer.

[0009] Furthermore, urea-formaldehyde resin is used to bond the substrate layer to the bottom layer of the floor, the floor surface layer to the substrate layer, the floor surface layer to the graphene heat dissipation layer, and the graphene heat dissipation layer to the substrate layer.

[0010] Furthermore, the depth of the groove at the bottom of the floor surface layer is 2 mm, and the height of the rib is 1 mm.

[0011] Furthermore, the graphene heat dissipation layer consists of an upper insulating layer, an upper graphene heat dissipation layer, an electric heating film, a lower graphene heat dissipation layer, and a lower insulating layer.

[0012] Furthermore, the electric heating film is made of 0.250PET+0.050EVA+0.100PET material, and has a thickness of about 0.5mm.

[0013] Furthermore, the lower end surface of the electric heating film is bonded to the upper end surface of the lower graphene heat dissipation layer.

[0014] Furthermore, no temperature sensor is installed on the floor surface. When the heating time reaches the critical temperature (28°C) after power is turned on, the control system cuts off the power to the electric heating film. When the floor surface cools down to a certain temperature (22°C) for a certain time, the control system restarts the electric heating film and continues heating for a certain time to return the temperature to the critical temperature. By repeating the cycle, the floor surface can be kept between 22°C and 28°C at all times, keeping the floor surface warm at all times.

[0015] The beneficial effects of the present invention compared to the prior art are:

[0016] 1. Graphene is used to prepare the heating film of the electric heating floor to achieve low-temperature heating. At the same time, the floor substrate plays the role of energy storage, saving energy while giving users a comfortable experience.

[0017] 2. Use a simple timer to control the heating time and adjust the temperature independently, which is low cost.

[0018] 3. The use of thermal insulation asbestos net prevents heat loss and promotes more efficient use of thermal energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a layered structure diagram of graphene electric heating solid wood composite flooring;

[0020] Figure 2 This is the overall structure diagram of the graphene electric heating floor;

[0021] Figure 3 This is a diagram of the graphene electric heating floor control system;

[0022] Figure 4 This is a diagram of the temperature control system of the graphene electric heating floor;

[0023] Figure 5 This is the PCM floor structure diagram;

[0024] Figure 6 This is a comparison chart of the temperature changes between the graphene electric heating floor and the ordinary floor;

[0025] Figure 7 This is the graph of the graphene electric heating floor heating curve;

[0026] Figure 8 This is the power-off cooling curve of the graphene electric heating floor;

[0027] Figure 9 This is a schematic diagram of the floor heat transfer process;

[0028] Figure 10 This is a schematic diagram of the structure of each layer of graphene electrically heated solid wood composite flooring;

[0029] Among them, 1-floor surface layer, 2-upper insulation layer, 3-upper graphene heat dissipation layer, 4-electric heating film, 5-lower graphene heat dissipation layer, 6-lower insulation layer, 7-base material layer, 8-asbestos mesh thermal insulation layer, 9-floor bottom layer, 10-AC power supply, 11-temperature control switch, 12-heating module, 13-temperature control resistor, 14-PCM floor surface layer, 15-PCM floor phase change material layer, 16-PCM floor base material layer, 17-PCM floor electric heating film, 18-PCM floor bottom layer, 19-temperature change curve of ordinary electric heating floor, 20-temperature change curve of graphene electric heating floor, I. Time control switch II. Electric heating floor III. Time coordinate (s) IV. Temperature coordinate (℃). DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0031] The graphene-based electrically heated solid wood composite flooring designed in this invention differs from previous designs in both material selection and internal structural design. Through innovative processes and a superior structural design, it improves heat conduction efficiency and energy consumption, thereby addressing the performance shortcomings of traditional electric heated floors and, to a certain extent, enhancing their heat transfer efficiency. This study analyzed temperature comparison test data from traditional electric heated floors and solid wood composite graphene-based electrically heated floors. The temperature change rates of the two types of flooring were measured under controlled variables. The study explored the impact of innovative materials and structures on the thermal efficiency of the graphene-based electrically heated flooring, providing technical support for improving the heat transfer performance of graphene-based electrically heated floors.

[0032] When the graphene electrically heated solid wood composite flooring is heated (power is applied to the heating film), heat is transferred through the heating film 4 to the upper and lower graphene heat dissipation layers 3 and 5. According to the second law of thermodynamics, heat flows in both directions. The upwardly transferred heat is transferred to the floor surface layer 1 through the graphene fins and then transferred into the indoor air through convection and radiation. Some of the downwardly transferred heat is insulated by the asbestos mesh thermal barrier layer 8 and stored in the base material layer 7, thus storing energy. According to the research results of the literature "Qu Bingxian, Wang Chengkang, Yan Junxia, et al. 2021. Research and simulation of heat transfer characteristics of graphene modified phase change polyurethane foam materials. Packaging Engineering, 42(11):87-95", the carbon crystal graphene used in the electric heating film is a lightweight material with excellent heat dissipation performance, good oxidation resistance, no rust, and low cost. It is generally used as the preferred material for heat conduction and heat dissipation. Therefore, the composite graphene electric heating floor involved in the present invention uses carbon crystal graphene film as a thermal conductive material. At the same time, asbestos fiber is selected as the asbestos mesh heat-insulating layer 8 of the composite graphene electric heating floor, because the thermal conductivity of asbestos fiber is 0.104-0.260W / (m·k), it has good thermal insulation performance and high fire resistance, and it also has high tensile strength, chemical and thermal corrosion resistance, good electrical insulation and thermal insulation performance, and is the best choice for thermal insulation and insulation materials. These characteristics just meet the performance requirements of the solid wood composite graphene electric heating floor involved in the present invention.

[0033] The graphene electric heating solid wood composite floor is modeled using the 3D design software Solidworks. Figure 2 As shown, the floor surface layer 1 and the graphene layer are mortise-jointed, the substrate layer 7 and the floor bottom layer 9 are connected together by gluing, and the lower end surface of the substrate layer 7 is grooved and embedded in the asbestos mesh heat-insulating layer 8.

[0034] like Figure 2As shown in the figure, the model of the solid wood composite graphene electric heating floor is established. The order from top to bottom is solid wood floor surface layer 1, upper insulation layer 2, upper graphene heat dissipation layer 3, electric heating film 4, lower graphene heat dissipation layer 5, lower insulation layer 6, substrate layer 7, asbestos mesh heat-resisting layer 8, and floor bottom layer 9. Grooves are opened above the graphene heat dissipation layer. The groove position can be adjusted according to the processing method. For example, if it is convenient for processing, grooves can be opened on the graphene and the insulation layer can be tightly attached; or a thick insulation layer can be connected first and then small grooves can be opened on the insulation layer to expand the area of the heat transfer surface. According to Fourier's law of heat conduction, the heat transfer amount Q is proportional to the heat transfer area of the carbon crystal graphene heat sink. Therefore, the heat transfer amount can be increased by increasing the heat transfer area. The present invention designs the carbon crystal graphene heat sink based on the theory of ribbed heat transfer, wherein the protruding surface of the carbon crystal graphene becomes the rib. According to the research results of the literature "Jiang Linxin, Li Bo. 2020. Influence of structural characteristics on the performance of spiral tube heat exchanger. Packaging Engineering, 41(13):197-203.", the ribs can effectively increase the area of the heat transfer part, thereby achieving the purpose of increasing the heat transfer amount.

[0035] An automatic temperature control system for graphene electric heating floor is designed to achieve self-regulation of the heating temperature during operation. The designed temperature control system mainly includes a heat generation system, a heat conversion system, a heat transfer system, a heat dissipation system, and other automatic control systems to ensure indoor temperature. The control system is implemented as follows: after the power is turned on, the electric heating film generates heat and adjusts the required temperature through a timer, and then transfers the heat to the surface of the solid wood floor through the graphene film. Its control system is as follows: Figure 3 shown.

[0036] The electric heating medium of graphene electric heated solid wood composite flooring is the metallic carbon crystal graphene in the graphene heat dissipation layer and the carbon fiber and silver-plated copper wire in the electric heating film. These are its main heating elements. When powered on, the atomic molecules of the carbon fiber ink violently vibrate and collide under the action of the electric field, generating heat energy. The electric heating film then transfers the heat to the metallic carbon crystal graphene by heat conduction. The carbon crystal graphene heat dissipation plate transfers heat to the floor surface by heat conduction. The heat energy generated by the electric heating film is evenly transmitted to the solid wood composite floor surface through the metallic carbon crystal graphene. When the graphene heat dissipation layer reaches equilibrium with the surface temperature of the floor, the floor surface will radiate heat at a constant temperature, transferring heat to the indoor air by radiation. The heat transferred:

[0037]

[0038] Where, is the emissivity; is the radiation surface area of the radiator. 、 are the floor surface temperature and the indoor air temperature, respectively.

[0039] After the air molecules gain heat, they undergo convective heat transfer with the indoor walls along with molecular thermal motion. The heat of convective heat transfer is:

[0040]

[0041] Where, is the convective heat transfer, unit is W; is the convective heat transfer coefficient; , are the average temperatures of the wall and fluid, respectively, in °C; is the convective heat transfer area, unit .

[0042] According to the thermal engineering principle that hot air is light and cold air is heavy, the heat radiated by the graphene electric heating floor causes the hot air in the room to rise continuously, and the cold air to fall and be gradually heated. This cycle is repeated, and the indoor temperature continues to rise, ultimately achieving the purpose of heating. Therefore, the heat transfer process of the above floor is as follows Figure 9 shown.

[0043] The present invention obtains the heating time for the floor to reach the critical temperature through heat transfer analysis of the floor model, so that a simple timer can be used for autonomous temperature adjustment. The low-cost adjustment method reduces the production cost of the electric heating floor and can provide users with a more comfortable smart home experience.

[0044] Example 1:

[0045] Step 1: Establish the thickness and structure of each layer of the graphene electric heating floor

[0046] The graphene electrically heated solid wood composite energy storage flooring consists of three layers. The top layer is made of cherry wood, sanded on both sides to a thickness of 4mm and laid along the grain. The base layer is made of ordinary pine, sanded to a thickness of 8mm and laid across the grain. The underlayer is low-grade veneer, made of rotary-cut pine, sanded on both sides to a thickness of 2mm. A 2mm thick insulating asbestos mesh was selected as the asbestos mesh heat barrier. A 2mm deep groove was machined into the lower surface of the base layer, and the 2mm asbestos mesh was inserted into the groove. The lower surface of the base layer was tightly bonded to the upper surface of the underlayer using urea-formaldehyde resin adhesive. A graphene heat dissipation layer is added to the floor surface layer and the substrate layer for heat conduction. A 2mm deep rib-shaped groove is opened at the bottom of the panel layer, where the groove depth is 1mm. Based on the principle of ribbed heat transfer, the graphene heat dissipation plate is processed with protruding rib parts on the upper surface to increase the heat transfer area. The ribs of the graphene heat dissipation layer are embedded in the bottom grooves of the floor surface layer. The upper end surface of the graphene heat dissipation layer is evenly coated with 0.5mm thick urea-formaldehyde resin adhesive. The adhesive here plays both a bonding and an insulating role. The lower surface of the graphene heat dissipation layer and the upper surface of the substrate layer are bonded by urea-formaldehyde resin adhesive. The graphene heat dissipation layer consists of an upper insulating layer, an upper graphene heat dissipation layer, an electric heating film, a lower graphene heat dissipation layer, and a lower insulating layer. The electric heating film is made of 0.250 PET, 0.050 EVA, and 0.100 PET, with an actual thickness of approximately 0.5 mm. The lower end surface of the electric heating film is bonded to the upper end surface of the lower graphene heat dissipation layer, while the lower graphene heat dissipation layer is not notched. The lower end surface of the lower graphene heat dissipation layer is also coated with a urea-formaldehyde resin adhesive with a fixed thickness of 0.5 mm, which serves as both bonding and insulation. The entire graphene heat dissipation layer is installed in the grooves between the floor surface and the base layer, bonding to the grooves on the lower end surface of the surface layer. The floor surface and base layer are bonded together using urea-formaldehyde resin. The overall dimensions are 910 mm × 127 mm × 18 mm.

[0047] In summary, the structure of each layer of graphene electric heating solid wood composite floor is as follows Figure 10 shown.

[0048] Graphene electric heating solid wood composite flooring layered structure Figure 1 shown. Figure 1 1 to 9 are floor surface layer, upper insulation layer, upper graphene heat dissipation layer, electric heating film, lower graphene heat dissipation layer, lower insulation layer, base material layer, asbestos mesh heat insulation layer, and floor bottom layer.

[0049] Step 2: Establish a temperature control system for graphene electric heating solid wood composite flooring

[0050] The actual room temperature is measured by the temperature detection element and converted into a voltage signal. The voltage signal is added to the amplifier input together with the preset indoor temperature voltage signal and compared. The difference signal is amplified by the amplifier to drive the electric heating film heating system to take corresponding action. When the detected indoor temperature is lower than the preset indoor temperature, the electric heating film heating system starts to start and continuously supplies heat, transferring heat to the low-temperature object carbon crystal graphene heat sink in the form of heat conduction, thereby making the indoor temperature evenly distributed; when the average room temperature reaches the preset temperature requirement, the difference signal is zero, the electric heating film heating system stops running, and the room temperature is controlled by intermittent opening and closing.

[0051] The temperature control system of the graphene electric heating floor is a typical closed-loop control system. Figure 4 As shown, the indoor temperature is adjusted by the timer, the power is turned on, an electrical signal i(t) is input to the whole system, and the heat transfer of the system is controlled by the control equation. When the temperature rises to the set temperature, the system is powered off to achieve feedback regulation. k 1. After the power is turned off, the temperature drops. When the specified time is reached, the system is powered on and heating starts again to achieve feedback regulation. k 2. When the floor surface temperature is too high after a specified time, the power supply circuit is cut off to ensure safety and eliminate hidden dangers. When the temperature is lower, the temperature circulation supply can be guaranteed, ensuring the comfort and energy saving of the product.

[0052] Whether the heating system of the electric heating film is started or not is related to the predetermined temperature set by the thermostat of the electric heating film. When the indoor temperature is lower than the set temperature, the heating system of the electric heating film will start. According to the principle of air circulation convection, the cold air will be below. After the electric heating film is heated, the heat is transferred to the room through the graphene heat dissipation layer and the floor surface layer, circulating and heating the cold air to make the indoor temperature uniform. When the predetermined time is reached, the electric heating film thermostat will automatically shut down the heating system. The constant room temperature is adjusted through this control system.

[0053] Based on winter heating requirements in northern China and the traditional Chinese medicine concept of "warm feet and cool head," floors frequently visited by people should be kept at a temperature between 24°C and 26°C, with an upper limit of 28°C. Floors occupied for short periods should be kept at a temperature between 28°C and 30°C, with an upper limit of 32°C. Floors unoccupied should be kept at a temperature between 35°C and 40°C, with an upper limit of 42°C. Graphene composite heating panels are commonly used in northern homes as the floor surface for frequent human contact. We use this as the standard, setting the heating temperature of the electric heating film at 32°C and the upper limit of the floor surface's suitable human body temperature at 28°C, maintaining a temperature of 26°C. At this temperature, the human body perceives a temperature of approximately 18°C to 22°C, providing a refreshing warmth and comfort during the cold winter months. This also saves energy and achieves a relatively economical heating temperature.

[0054] The present invention uses a simple timer to control the temperature, and obtains the temperature change curve according to the thermal analysis simulation results. Figure 7 、 8 As shown. When the total thickness of the floor is 18mm, the time it takes for the floor surface to reach 22°C after heating is 1637 seconds, the time it takes to reach 26°C is 3342 seconds, and the time it takes to reach 28°C is 6533 seconds. In order to facilitate setting the timer, the heating time is rounded to the nearest minute, and the time it takes to reach 22°C is 27 minutes (1620s), the time it takes to reach 26°C is 56 minutes (3360s), and the time it takes to reach 28°C is 109 minutes (6540s). Therefore, after the floor is started, it can be powered off after 109 minutes of heating. After the floor is powered off, it will take 1486 seconds ( Figure 8 The simulation shows that the temperature drops to 22°C, rounded to 25 minutes (1500 seconds). After the floor is powered off for 25 minutes, the control system reheats the floor for another 81 minutes. This cycle ensures that the floor surface remains between 22°C and 28°C, providing users with the most comfortable experience.

[0055] Step 3: Set the timer to control the heating time

[0056] According to the above content, when the floor is just turned on, the heating time is set to 109 minutes. The power will be automatically cut off after 109 minutes. When the floor surface temperature is lower than 22°C after 25 minutes, the control system will heat the floor again for 81 minutes. This cycle can keep the floor surface between 22°C and 28°C.

[0057] Comparative Example 1:

[0058] The comparison object is a PCM electric heating floor with a thickness of 18mm. The surface layer 14 is made of eucalyptus wood with double-sided sanding and a thickness of 4mm. The phase change material layer 15 is a composite PCM with a thickness of 3mm. The base layer 16 is made of 8mm thick pine sawn wood. The electric heating film 17 is heated at a low temperature. The bottom plate 18 is made of pine wood with a fixed thickness of 2mm. The electric heating film is 1mm. The basic structure is as follows Figure 5 shown.

[0059] The laboratory dimensions were 8m × 6m × 3m. A thermocouple temperature measuring instrument was used to measure the temperature changes of the floor surface and subfloor layers over time. The indoor temperature was set to a normal post-heating temperature of 16°C ± 2°C, and the humidity was maintained at 20 ± 5%. A humidifier was placed to maintain minimal humidity fluctuations after heating. A conventional electric heating floor and a solid wood composite graphene electric heating radiator floor were assembled into groups of three, each laid face-up on either side of the laboratory. Six temperature collection points were evenly spaced on the floor, and three were placed vertically in the room, spaced 0.5m apart. The floor was heated for 1000 seconds. As the graphene electric heating floor was heated, the floor surface temperature gradually increased, increasing the temperature difference between indoor and outdoor. After 0.5 hours of inactivity, the floor surface temperature naturally cooled.

[0060] The surface temperature changes of ordinary electric heating floor and composite graphene electric heating floor after 1000s of power on are as follows Figure 6 As can be seen from the figure, the floor will continue to heat up for a period of time after the heating is stopped. The graphene electric heating floor 19 has a better energy storage effect. Within 1 hour after the peak, the ordinary floor 20 quickly cools down to below 20°C, while the composite graphene electric heating floor cools down relatively slowly. Within 1 hour, the floor surface remains above 20°C. Therefore, it can be seen that the composite graphene electric heating floor has a better energy storage effect and can save more energy while providing a comfortable life.

[0061] Through comparative experiments, it is verified that graphene electric heating solid wood composite flooring has better heat transfer efficiency and energy storage effect, and can provide a safer, cleaner, more comfortable and healthier heating method for the cold northern winter.

Claims

1. A graphene electrically heated solid wood composite energy storage floor, characterized by: The floor comprises, from top to bottom, a floor surface layer (1), a base material layer (7) and a floor bottom layer (9); The lower surface of the substrate layer (7) is processed into a groove with a depth of 2 mm, and an asbestos mesh heat-insulating layer (8) is provided in the groove; The floor surface layer (1) has a groove on its lower surface, and the base material layer (7) has a groove on its upper surface, and the two grooves are matched to form a graphene heat dissipation layer; The groove depth at the bottom of the floor surface is 2mm, and the rib height is 1mm; The graphene heat dissipation layer is composed of an upper insulating layer (2), an upper graphene heat dissipation layer (3), an electric heating film (4), a lower graphene heat dissipation layer (5), and a lower insulating layer (6); Urea-formaldehyde resin is used for bonding between the substrate layer (7) and the floor bottom layer (9), between the floor surface layer (1) and the substrate layer (7), between the floor surface layer (1) and the graphene heat dissipation layer, and between the graphene heat dissipation layer and the substrate layer (7); The lower end surface of the electric heating film is bonded to the upper end surface of the lower graphene heat dissipation layer; The electric heating medium of graphene electric heating solid wood composite flooring is the metal carbon crystal graphene in the graphene heat dissipation layer and the carbon fiber and silver-plated copper wire in the electric heating film. These are its main heating elements. When the power is turned on, the atomic molecules of the carbon fiber ink violently oscillate and collide under the action of the electric field, thereby generating heat energy. The electric heating film transfers the heat to the metal carbon crystal graphene by heat conduction. The carbon crystal graphene heat dissipation plate transfers the heat to the floor surface by heat conduction. The heat energy generated by the electric heating film is evenly transmitted to the surface of the solid wood composite flooring through the metal carbon crystal graphene. When the surface temperature of the graphene heat dissipation layer reaches equilibrium with that of the floor, the floor surface will radiate heat at a constant temperature, transferring the heat to the indoor air by radiation. The electric heating film is made of 0.250PET+0.050EVA+0.100PET material.

2. The graphene electrically heated solid wood composite energy storage floor according to claim 1, characterized in that: No temperature sensor is installed on the floor surface. When the heating time reaches the critical temperature (28°C) after power is turned on, the control system cuts off the power to the electric heating film. When the floor surface cools down to a certain temperature (22°C) within a certain period of time, the control system restarts the electric heating film and continues heating for a certain period of time to return the temperature to the critical temperature. This cycle repeats to ensure that the floor surface temperature is always between 22°C and 28°C, keeping the floor surface warm at all times.

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