Electric heating body with graphite as substrate

Abstract

The utility model discloses an electric heating body with graphite as a substrate, which comprises a graphite substrate, an insulating heat conduction coating is arranged on the outer surface of the graphite substrate, and an electrified heating layer is arranged on the outer surface of the insulating heat conduction coating. According to the electric heating body, the graphite with excellent heat-conducting property is used as the substrate, and the insulating heat-conducting coating is additionally arranged between the outer surface of the graphite and the electric heating layer in order to be matched with the electric heating layer for use, so that heat generated by the electric heating layer is quickly transferred to the graphite through the insulating heat-conducting coating to realize quick heating, and the electric heating body is high in heat efficiency; and the electrified heating layer is separated from a heated substance (such as water) by the graphite and the insulating heat-conducting coating, so that the heated substance is separated from electricity, such as water-electricity separation, the use is safer, and in addition, the graphite is easy to form a gasification core in the heating process, so that boiled water is continuously discharged.

Description

Technical Field

[0001] The utility model relates to an electric heating element, in particular to an electric heating element with graphite as a substrate. Background Art

[0002] Existing electric heating bodies include tubular or flat shapes, such as quartz glass tubes, ceramic heating tubes and metal electric heating tubes, among which the outer surfaces of quartz glass tubes and ceramic tubes are vapor-deposited with metal oxide films, or silk-screened with resistor slurries or wound with resistor wires. During the heating process, quartz glass tubes have the advantages of low expansion coefficient and no precipitation of harmful substances, but the defects of quartz glass tubes are low thermal conductivity (low thermal efficiency), low mechanical strength, easy to break during use, and the inner wall of quartz glass tubes is smooth. During the heating process, it is difficult to form a vaporization core, resulting in discontinuity and interruption of boiling water. Although ceramic tubes have good thermal conductivity and improved thermal efficiency during the heating process, the defects are that ceramic tubes have a large expansion coefficient and poor thermal shock resistance. If a large temperature difference occurs during the heating process, they will easily break, and the cost of raw materials is high. The metal heating tube is made by placing a resistance wire inside the tube and then filling it with insulating magnesium powder and then shrinking the tube. The metal tube has stable performance and a moderate price, but the production process is complicated and can easily cause environmental pollution. In addition, the temperature rises slowly during the heating process, the thermal inertia is large, and the thermal efficiency is low. In addition, the metal electric heating tube is immersed in water during the heating process, which is prone to leakage hazards and is unsafe. Utility Model Content

[0003] The utility model aims to provide an electric heating element with graphite as substrate, which has the advantages of high thermal efficiency, safe use and continuous and uninterrupted flow of hot water.

[0004] The purpose of the utility model is achieved in this way:

[0005] A graphite-based electric heating element comprises a graphite substrate, characterized in that an insulating thermal conductive coating is provided on the outer surface of the graphite substrate, and an electric heating layer is provided on the outer surface of the insulating thermal conductive coating. This electric heating element uses graphite with excellent thermal conductivity as a substrate. In order to cooperate with the electric heating layer, an insulating thermal conductive coating is added between the outer surface of the graphite and the electric heating layer, so that the heat generated by the electric heating layer is quickly transferred to the graphite through the insulating thermal conductive coating to achieve rapid heating. It has high thermal efficiency, and the electric heating layer and the heated substance (such as water) are separated by graphite and the insulating thermal conductive coating, so that the heated substance and electricity are separated, such as water-electricity separation, so it is safer to use. In addition, graphite is easy to form a gasification core during the heating process, so the boiling water is continuously discharged.

[0006] The purpose of the utility model can also be solved by the following technical measures:

[0007] Furthermore, the expansion coefficient of the insulating thermal conductive coating is the same as or similar to that of the graphite substrate, so that the insulating thermal conductive coating is coated on the graphite and has the advantages of being difficult to peel off, break or crack, and having a large insulation resistance coefficient, high voltage resistance and large thermal conductivity.

[0008] Furthermore, the graphite substrate can be a tubular body. When heating water, the energized heating layer and the water flowing through the tubular body are separated by the tubular graphite substrate and the insulating thermal conductive coating, thereby achieving water-electricity separation, making it safer to use. In addition, the tubular graphite substrate easily forms a vaporization core during the heating process, so the boiling water is continuously discharged.

[0009] Furthermore, the graphite substrate may be a flat plate. When used for heating, the energized heating layer and the heated substance are separated by the flat graphite substrate and the insulating thermal conductive coating, which can also achieve separation of the heated substance and electricity, making it safer to use.

[0010] Furthermore, the insulating thermally conductive coating comprises 3 to 4 insulating thermally conductive thin layers stacked in an upper and lower order, so that 3-4 insulating thermally conductive thin layers are formed on the surface of the graphite substrate, and each layer is independent, which is more conducive to improving the overall strength of the entire insulating thermally conductive coating.

[0011] Furthermore, the total thickness of the insulating thermally conductive coating is between 30-120 um. The insulating thermally conductive coating in this thickness range has the advantages of good thermal conductivity and high heating efficiency.

[0012] Furthermore, the thickness of each insulating and heat-conducting thin layer is between 10-30 um, so that each insulating and heat-conducting thin layer has independent and sufficient hardness.

[0013] Furthermore, the energized heating layer is a metal oxide film generated on the surface of the insulating thermal conductive coating by vapor deposition. The metal oxide film can generate sufficient heat for heating, is easy to implement, and has mature technology.

[0014] Furthermore, the energized heating layer is coated with a layer of resistor paste on the surface of the insulating thermal conductive coating by silk screen printing. The resistor paste can generate sufficient heat for heating, and the technology is mature, which can also achieve the purpose of this patent.

[0015] Furthermore, the energized heating layer is achieved by winding a resistance wire on the surface of the insulating thermal conductive coating. It is easy to implement, the technology is mature, and it can also achieve the purpose of this patent.

[0016] The beneficial effects of the utility model are:

[0017] (1) The electric heating element of the utility model utilizes graphite with excellent thermal conductivity as a substrate. To cooperate with the electric heating layer, an insulating thermal conductive coating is added between the outer surface of the graphite and the electric heating layer, so that the heat generated by the electric heating layer is quickly transferred to the graphite through the insulating thermal conductive coating to achieve rapid heating. It has high thermal efficiency. The electric heating layer and the heated material (such as water) are separated by graphite and the insulating thermal conductive coating, so that the heated material and electricity are separated, such as water and electricity are separated, so it is safer to use. In addition, graphite is easy to form a gasification core during the heating process, so the hot water is continuously discharged.

[0018] (2) The electric heating element of the utility model can be used as a tubular heating element or a flat heating element. Since the expansion coefficient of the insulating thermal conductive coating is the same as or similar to that of the graphite substrate, the insulating thermal conductive coating is coated on the graphite and has the advantages of being difficult to peel off, break or crack, and having a large insulation resistance coefficient, high pressure resistance and large thermal conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of a first embodiment of the electric heating element of the utility model.

[0020] Figure 2 yes Figure 1 Enlarged view of point A.

[0021] Figure 3 It is a schematic diagram of the second embodiment of the electric heating element of the utility model.

[0022] Figure 4 It is a schematic diagram of the third embodiment of the electric heating element of the utility model.

[0023] Figure 5 It is a schematic diagram of a fourth embodiment of the electric heating element of the utility model. DETAILED DESCRIPTION

[0024] Embodiment 1: Figure 1 and Figure 2 As shown, a tubular electric heating body with graphite as a substrate includes a tubular graphite substrate 1, and the outer surface of the tubular graphite substrate 1 is provided with an insulating thermal conductive coating 2, and the expansion coefficient of the insulating thermal conductive coating 2 is the same or similar to that of the tubular graphite substrate 1. In this embodiment, the insulating thermal conductive coating 2 includes 3 to 4 layers of insulating thermal conductive thin layers 21, 22, and 23 stacked in an upper and lower order, and the outer surface of the insulating thermal conductive coating 2 is provided with an electric heating layer 3, and the electric heating layer 3 is a layer of metal oxide film 31 generated on the surface of the insulating thermal conductive coating 2 by vapor deposition.

[0025] The total thickness of the insulating thermal conductive coating 2 is between 30-120 um, and the thickness of each of the insulating thermal conductive thin layers 21, 22, 23 is between 10-30 um.

[0026] Embodiment 2: Figure 3 As shown, the second embodiment is similar to the first embodiment, except that the energized heating layer 3 is coated with a layer of resistance paste 32 on the surface of the insulating thermal conductive coating 2 by screen printing. The effect of the second embodiment is the same or similar to that of the first embodiment.

[0027] Embodiment 3: Figure 4 As shown, the third embodiment is similar to the first embodiment, except that the energized heating layer 3 is wound with a resistance wire 33 on the surface of the insulating thermal conductive coating 2 by winding. The effect of the third embodiment is the same or similar to that of the first embodiment.

[0028] Embodiment 4: Figure 5 As shown, the fourth embodiment is similar to the first and second embodiments, except that the graphite substrate 1 is a flat plate, and the upper surface of the graphite substrate 1 of the flat plate is provided with an insulating thermal conductive coating 2, and the "electrically heated layer 3" is the same as the first or second embodiment, that is, a layer of resistor paste 32 is covered on the surface of the insulating thermal conductive coating 2 by a coating screen printing method. Or a layer of resistor paste 32 is covered on the surface of the insulating thermal conductive coating 2 by a coating screen printing method. It can also achieve the purpose of this patent.

[0029] The electric heating tubes of the above-mentioned multiple embodiments are only a few examples of the present invention and are not exhaustive.

[0030] The electric heating element of the utility model, the insulating thermal conductive coating 2 formed on the outer side wall of the graphite substrate 1 is a new type of insulating coating slurry, the slurry can be formed on the outer side wall of the manufactured graphite substrate 1 by silk screen printing or spraying, the slurry includes the following components and their weight parts: 50-60 parts of ceramic material, 10-20 parts of zirconium tungstate, 5-15 parts of 99.9% high-purity quartz sand, 5-20 parts of aluminum dihydrogen phosphate aqueous solution, 1-5 parts of water glass and 1-5 parts of acetone; wherein, the role of the ceramic material in the slurry is insulation and thermal conductivity; zirconium tungstate is a negative thermal expansion material, and its role in the slurry is to adjust the expansion coefficient of the slurry to be close to the expansion coefficient of graphite, so that the slurry coated on the graphite is not easy to peel off, break or crack; 99.9% high-purity quartz sand, such as: SiO2≥99.9% , Fe2O3≤0.001%, the role of high-purity quartz sand is to improve the gloss of the coating, and at the same time it also plays a role in adjusting the expansion coefficient of the coating and the weather resistance of the coating, increasing the hardness and corrosion resistance of the coating; the role of aluminum dihydrogen phosphate is to mix with ceramic materials (such as: one of silicon carbide, boron nitride and aluminum oxide) and high-purity quartz sand at room temperature and then form a high viscosity at a constant temperature of 50-90°C for 4-8 hours. After drying and sintering at 350-850°C, it has high resistance to precipitation (precipitation), compression and hydration, and has good insulation. The function of water glass is a kind of adhesive with strong bonding force, high strength and good heat resistance; acetone is a low boiling point, quick-drying polar solvent, and its function is to improve the leveling property of the coating in this formula; the insulating coating slurry prepared is suitable for graphite as a substrate, and the insulating coating slurry is coated on its surface. The insulating coating slurry has the advantages of small expansion coefficient, not easy to peel off, not easy to break and not easy to crack, large insulation resistance coefficient, high voltage resistance and large thermal conductivity.

[0031] Among them, the ceramic material is one of silicon carbide, boron nitride and aluminum oxide. Compared with general ceramic materials, these three specific ceramic materials have good cost performance, good thermal conductivity and insulation properties. Their expansion coefficients are close to those of graphite materials, and their thermal shock resistance is significantly improved.

[0032] The above-mentioned slurry is screen-printed or sprayed 3-4 times on the outer surface (outer wall) of the above-mentioned graphite substrate 1 in sequence, that is, 3-4 layers of the above-mentioned insulating thermal conductive thin layers 21, 22, 23 are formed, and each layer of insulating thermal conductive thin layers 21, 22, 23 forms a stacked multi-layer structure in an upper and lower order.

[0033] The electric heating element of the utility model is a graphite substrate 1 made of graphite material, and the insulating thermal conductive coating 2 is formed on its outer surface, that is, the graphite substrate 1 and the insulating thermal conductive coating 2 together constitute a graphite substrate. After testing, its performance indicators are as follows: (1) After the graphite substrate is placed in a 600°C high-temperature furnace for 30 minutes, it is taken out and put into water at 15°C to 25°C. The insulating thermal conductive coating 2 does not peel off, break or crack. The measured expansion coefficient is 2.0x10-6 / k-1. (2) The insulation resistance of the insulating thermal conductive coating 2 is ≥30MΩ, and there is no chrome flash or breakdown in the 1850V withstand voltage test, and the leakage current is ≤0.2mA. (3) The thermal conductivity is greater than or equal to 45W / cm.K.

Claims

1. An electric heating element with graphite as substrate, comprising a graphite substrate (1), characterized in that: The outer surface of the graphite substrate (1) is provided with an insulating thermal conductive coating (2), and the outer surface of the insulating thermal conductive coating (2) is provided with an electrically conductive heating layer (3).

2. The electric heating element with graphite as substrate according to claim 1, characterized in that: The insulating thermal conductive coating (2) and the graphite substrate (1) have expansion coefficients that are the same or similar.

3. The electric heating element with graphite as substrate according to claim 1, characterized in that: The graphite substrate (1) is a tubular body.

4. The electric heating element with graphite as substrate according to claim 1 is characterized in that: The graphite substrate (1) is a flat plate.

5. The electric heating element with graphite as substrate according to any one of claims 1 to 4, characterized in that: The insulating heat-conducting coating (2) comprises 3 to 4 insulating heat-conducting thin layers (21, 22, 23) stacked in an upper and lower order.

6. The electric heating element with graphite as substrate according to claim 5, characterized in that: The total thickness of the insulating thermal conductive coating (2) is between 30 and 120 μm.

7. The electric heating element with graphite as substrate according to claim 6 is characterized in that: The thickness of each of the insulating and heat-conducting thin layers (21, 22, 23) is between 10 and 30 um.

8. The electric heating element with graphite as substrate according to claim 3 or 4, characterized in that: The energized heating layer (3) is a layer of metal oxide film (31) generated on the surface of the insulating thermal conductive coating (2) by vapor deposition.

9. The electric heating element with graphite as substrate according to claim 3 or 4, characterized in that: The energized heating layer (3) is formed by coating and silk-screening a layer of resistance paste (32) on the surface of the insulating thermal conductive coating (2).

10. The electric heating element with graphite as substrate according to claim 3, characterized in that: The energized heating layer (3) is formed by winding a resistance wire (33) around the surface of the insulating heat-conducting coating (2).

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