An electric heating element and electric heating device with peltier heat dissipation and joule heat coupling

Abstract

The application discloses a Peltier heat release and Joule heat coupling electric heating element and electric heating device. The electric heating element is formed by linearly connecting a p-type thermoelectric arm, a nickel-chromium alloy and an N-type thermoelectric arm in sequence, and the heights of the N-type and p-type thermoelectric arms on both sides are the same and lower than the height of the nickel-chromium alloy. The p-type thermoelectric arm and the N-type thermoelectric arm are prepared from Mg2Si by doping different elements, and interface buffer layers are arranged at the interfaces between the two ends of the nickel-chromium alloy and the p-type thermoelectric arm and the N-type thermoelectric arm. The interface buffer layers are connected with the p-type thermoelectric arm and the N-type thermoelectric arm through a conductive silver glue layer. The Peltier heat release and Joule heat are coupled through the above method, and the electric heating conversion efficiency is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of electric heater technology, specifically to an electric heating element and device that couples Peltier exothermic heat with Joule thermal heat. Background Technology

[0002] Current mainstream electric heating technologies rely on Joule heating as their core, depending on the resistance heating characteristics of metal alloys (such as Ni-Cr alloys). However, these devices suffer from two major bottlenecks: first, limited electrothermal conversion efficiency, with low infrared emissivity of the metal surface leading to significant Joule heat loss through conduction / convection; and second, insufficient temperature control flexibility, making them prone to structural failure due to thermal stress under long-term high-temperature operation. Therefore, coupling Peltier exothermic heating with Joule heating to achieve a "1+1>2" effect in heating efficiency is of great significance in high-temperature heating applications.

[0003] However, the actual process of Peltier exothermic coupling with Joule thermal coupling faces three major challenges: performance synergy, structural stability, and process adaptation.

[0004] (a) Difficulty in coordinating the two heat output mechanisms: Imbalance between the two heat outputs

[0005] Peltier exothermics rely on electronic energy level transitions at the thermoelectric arm interface, requiring extremely high uniformity of electrical transport; Joule heating relies on the resistivity of Ni-Cr alloys, being sensitive to the stability of resistance values. Both are prone to heat output imbalances due to sudden changes in local resistance. The directionality of Peltier exothermics conflicts with the diffusivity of Joule heating; if the heat radiation directions are inconsistent, it can lead to significant heat loss, with coupling efficiency even lower than that of a single heating mechanism.

[0006] (ii) Difficulty in matching material properties: mutual constraints among multiple dimensions of performance

[0007] Thermal expansion mismatch: The thermal expansion difference between the Mg2Si thermoelectric arm and the Ni-Cr alloy is significant, which can easily lead to interface peeling and structural cracking during high-temperature cycling.

[0008] Resistivity mismatch: The resistivity of the Mg2Si thermoelectric arm differs significantly from that of the Ni-Cr alloy. If not precisely matched, it will lead to uneven current distribution and disrupt the synergy of the two heating mechanisms.

[0009] (iii) Difficulty in interface connection: conductivity and structural stability cannot be simultaneously achieved.

[0010] Traditional soldering processes involve high temperatures (≥231.9℃), which can affect the performance of thermocouples, leading to brittle fracture of Mg2Si thermocouples, excessive oxidation of Ni-Cr alloys, and the inability of rigid connections to alleviate thermal stress. Furthermore, after high-temperature cycling, incomplete soldering and desoldering are prone to occur. Additionally, the surface roughness and gaps between the thermocouple and the alloy can increase contact resistance, weakening the Peltier effect and causing Joule heat to concentrate at the interface, resulting in localized overheating.

[0011] (iv) Difficulty in process integration: High requirements for performance coordination across multiple stages

[0012] The design of the heating layer must simultaneously satisfy both "uniform electrical transmission" and "concentrated heat radiation," which is difficult to control precisely using traditional processing techniques. The fabrication processes of the buffer layer, connecting layer, and heating layer interfere with each other, and uneven coating of the connecting layer between the thermoelectric arm and the buffer layer can lead to sudden changes in resistance.

[0013] In summary, there is an urgent need to provide a method for fabricating an electric heating element that couples Peltier exothermic energy with Joule heat to solve the above problems. Summary of the Invention

[0014] Therefore, the technical problem to be solved by this invention is to provide an electric heating element and device that couples Peltier exothermic heat with Joule thermal heat. This invention achieves Peltier exothermic heat with Joule thermal heat coupling, improving the heating efficiency of the electric heating element, reducing heat loss during heat exchange, reducing thermal mismatch stress in the electric heating element, extending the service life of the electric heating element, and avoiding interface peeling and structural cracking. At the same time, it simplifies the structure of the electric heating element, reduces its production cost, and enables the electric heating element to achieve good durability, low-cost manufacturing, and design flexibility.

[0015] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0016] An electric heating element that is Peltier exothermic and Joule thermally coupled, wherein the electric heating element is composed of a p-type thermoelectric arm, a nickel-chromium alloy and an N-type thermoelectric arm connected in a straight line in sequence, and the N and p-type thermoelectric arms on both sides are at the same height and are lower than the height of the nickel-chromium alloy.

[0017] The p-type and N-type thermoelectric arms are made of Mg2Si by doping with different elements. An interface buffer layer is set at the interface between the nickel-chromium alloy and the p-type and N-type thermoelectric arms to realize the coupling of Peltier exothermic and Joule heat and improve the electrothermal conversion efficiency.

[0018] The aforementioned electric heating element, which combines Peltier exothermic and Joule thermal coupling, uses a p-type thermoelectric arm made of Mg2Si doped with Li. 1.97 Li 0.03 Si, the material of the N-type thermoelectric arm is Mg2Si doped with Bi element. 2.08 Si 0.97 Bi 0.03 .

[0019] Mg 1.97 Li 0.03The specific preparation steps for Si are as follows: high-purity Mg powder (7.8% excess to compensate for volatilization), Si powder, and Li... 13 The mass ratio of Si4 powder is 110:59.5:1. Mg powder, Si powder, and Li powder are weighed separately. 13 Si4 powder was mixed and ground to obtain a mixed powder. All weighing, mixing, and grinding operations were carried out in a glove box. The mixed powder was cold-pressed into cylindrical blocks (pressure 200-400 MPa, holding for 5-20 minutes). The cylindrical blocks were placed in a tube furnace and heated and held at 500-600℃ for 5-10 minutes under argon protection to obtain loose blue Mg2Si powder. The reaction product was ground and sieved to obtain Mg. 1.97 Li 0.03 Si fine powder. Mg 1.97 Li 0.03 Si fine powder is loaded into a high-purity graphite mold, vacuumed, heated, pressurized, and held at that temperature (800-1000℃, 20-50 MPa, for 3-10 minutes). After cooling, Mg is obtained. 1.97 Li 0.03 Si high-density bulk sample.

[0020] Mg was prepared by self-propagating combustion synthesis method 2.08 Si 0.97 Bi 0.03 Specifically, high-purity Mg, Si, and Bi powders (Mg:Si:Bi powder mass ratio of 9:4.5:1) are accurately weighed, mixed, and ground to obtain a mixed powder. The mixed powder is then placed into a quartz tube, vacuumed, and sealed. Ignition initiates a self-propagating high-temperature reaction, rapidly synthesizing Mg. 2.08 Si 0.97 Bi 0.03 Powder. Mg 2.08 Si 0.97 Bi 0.03 The powder is ground to obtain a fine powder, which is then placed into a graphite mold and sintered in an SPS (temperature 800–1000℃, pressure 20–50 MPa, holding time 3–10 minutes) to obtain Mg. 2.08 Si 0.97 Bi 0.03 Highly dense bulk sample.

[0021] The present invention uses Mg2Si as the matrix material for N and P type thermoelectric arm materials. By using the same matrix material and doping different elements, N / P type materials are prepared. This improves the electrothermal conversion efficiency of the electric heating element, simplifies the process, reduces manufacturing costs and defect density, and reduces the increase in thermal resistance during long-term operation.

[0022] The chemical composition of the nickel-chromium alloy is Ni-xCr, where x represents the mass percentage of Cr in the nickel-chromium alloy, x = 10~20 wt.%. That is, the nickel-chromium alloy is a Ni-xCr alloy with different doping ratios, such as Ni-10Cr, Ni-15Cr, and Ni-20Cr nickel-based alloy materials. Among these, Ni-15Cr (with a resistivity range of 1.06 × 10⁻⁶) is preferred. -4 –1.12×10 -4 The range of values ​​for Ω·cm and the coefficient of linear expansion is 13 × 10⁻⁶. ⁻6 –16.0×10 -6 / K), Ni-20Cr (resistivity range is 1.09×10 -4 –1.14×10 -4 The value of the linear expansion coefficient (Ω·cm) ranges from 16.0 × 10⁻⁶. ⁻6 –20.0×10 -6 / K) or Ni-10Cr (resistivity range is 0.95×10 -4 – 1.05×10 -4 The value of the linear expansion coefficient (Ω·cm) ranges from 12.5 × 10⁻⁶. ⁻6 – 13.0 × 10 -6 / K).

[0023] Ni-15Cr exhibits high resistivity, enabling more efficient Joule heating and thus improving electrothermal conversion efficiency. Its moderate coefficient of linear expansion facilitates better thermal expansion matching with the graphene buffer layer (which has a negative coefficient of expansion) and other components (such as Mg2Si thermoelectric arms), reducing the risk of interfacial delamination or cracking due to thermal stress. High-temperature oxidation resistance ensures stable material performance and reduces oxidation failure under long-term high-temperature service conditions. A small temperature coefficient of resistance means minimal fluctuation in resistance with temperature, contributing to the stability and controllability of Joule heat output. High resistance stability ensures a reliable heating mechanism, avoiding heat output imbalances caused by sudden changes in local resistance.

[0024] The coefficient of linear expansion of traditional Ni-Cr alloys is 17.0 × 10⁻⁶. ⁻6 –18.0×10 -6 / K, using Ni-15Cr alloy, a Cr content of 15wt.% achieves optimal distortion, avoiding both insufficient constraint due to too little Cr and lattice defect agglomeration due to too much Cr, thus maximizing the suppression of atomic thermal expansion and reducing CTE to a certain extent. Within the same temperature range, Ni-15Cr has a relatively low coefficient of linear expansion, similar to graphene (CTE≈-8×10). ⁻6 ~-1×10 ⁻6The N / A ratio ( / K) shows good matching, resulting in lower coating stress. Furthermore, the resistivity and thermal output characteristics of the three alloys mentioned above are optimized by adjusting the composition ratio. While Ni-10Cr and Ni-20Cr alloys do not have the best overall performance, they each have their advantages. Ni-10Cr has the lowest CTE, resulting in good matching with ceramic / carbon coatings and low thermal stress; it also has the lowest resistivity, making it suitable for low-power precision applications. The Ni-Cr alloy matrix is ​​austenitic γ-Ni, and Cr atoms are larger than Ni atoms. Dissolving into the Ni lattice causes lattice distortion, hindering dislocation movement. In Ni-20Cr, the Cr content is doubled, significantly enhancing lattice distortion and thus greatly increasing dislocation slip resistance, making dislocation movement more difficult at high temperatures and resulting in a lower creep rate. In contrast, the 20% Cr in the Ni-20Cr alloy is largely dissolved in the Ni austenitic matrix, causing strong lattice distortion and producing a significant solid solution strengthening effect, resulting in higher high-temperature creep resistance and less deformation at high temperatures. It is particularly suitable for industrial furnace heating elements and high-temperature heat-resistant structural components.

[0025] The aforementioned electric heating element, which couples Peltier exothermic and Joule thermal coupling, involves annealing the p-type and N-type thermoelectric arms under an inert atmosphere before assembly, followed by cooling to room temperature to obtain pretreated p-type and N-type thermoelectric arms. The annealing temperature is 400–600℃, and the annealing time is 3–4 hours. During the synthesis of Mg₂Si, an additional 4–8 at% Mg must be added to compensate for high-temperature volatilization losses. Excess Mg cannot react completely with Si to form Mg₂Si and will remain at grain boundaries or exist in a free state. During cooling, the solid solubility of Mg in Si decreases sharply, leading to strong Mg segregation to the surface, enriching the sample surface as elemental Mg. Therefore, the prepared Mg₂Si sample contains elemental Mg on its surface. Pure Mg has a melting point of only 650℃ and a boiling point of 1090℃, and already exhibits significant vapor pressure at 400–600℃. Once free elemental Mg precipitates on the surface, it will rapidly evaporate / sublimate even at relatively low temperatures. Since Mg is volatile, sample volatilization during subsequent heating can contaminate the substrate. Therefore, p-type and N-type thermoelectric arms prepared from Mg₂Si by doping with different elements are annealed. The arms are heated to 400–600 °C for 3–4 hours, followed by natural cooling. This process cleans the surface of the Mg₂Si sample, purifying the material and preventing sample volatilization and substrate contamination during subsequent heating. This annealing temperature range allows for effective volatilization of elemental Mg while maintaining the stability of the Mg₂Si matrix. Furthermore, it avoids excessively high temperatures that could exacerbate Mg₂Si decomposition (Mg₂Si ⇌ 2Mg(g) + Si(s)), uncontrolled diffusion of Li / Bi dopants, or significant oxidation of the material. Annealing time is 3-4 hours: sufficient for the free Mg on the surface to fully volatilize and diffuse out, while avoiding excessive heat treatment that could lead to grain coarsening or increased defects.

[0026] The aforementioned electric heating element, which couples Peltier exothermic heat with Joule heating, features an interface buffer layer with a thickness of 15-25 μm. This interface buffer layer is a graphene buffer layer, formed by calcining a nickel-chromium alloy in graphite powder at 700-900°C for 7-9 hours, resulting in the graphite powder adhering to the surface of the nickel-chromium alloy. Using a material with a negative coefficient of thermal expansion as the interface buffer layer creates a step-like change in the coefficient of thermal expansion, smoothly transitioning the thermal expansion behavior from low to high expansion. This eliminates the "cliff-like" drop in physical properties, thereby buffering differences in thermal expansion and eliminating interfacial thermal stress. Due to its negative expansion and isotropic properties, the graphene buffer layer, when used for interface buffering, can compensate for the positive expansion of the heating resistance layer.

[0027] The aforementioned electric heating element with Peltier exothermic and Joule thermal coupling includes an interface buffer layer connected to both a p-type and an N-type thermoelectric arm via a conductive silver paste layer. The conductive silver paste layer contains ≥85% silver powder. The conductive silver paste layer bonds the Mg2Si thermoelectric arm to the Ni-Cr alloy, strengthening the electrical connection and eliminating the need for soldering. The coverage area of ​​the conductive silver paste is determined based on the contact area between the Mg2Si thermoelectric arm and the Ni-Cr alloy. Using conductive silver paste instead of soldering results in lower interface resistance and avoids damage to the Mg2Si thermoelectric arm and Ni-Cr alloy due to the high temperatures of soldering. This leads to more stable contact resistance after long-term aging. Furthermore, eliminating the need for an electrical connection layer reduces processing steps, simplifies the structure of the electric heating element, further reduces production costs, and also reduces thermal mismatch stress, extending the lifespan of the electric heater using this element.

[0028] Secondly, the present invention also provides an electric heating device that is Peltier exothermic and Joule thermally coupled. The electric heating device includes multiple sets of spaced heating units embedded in the inner side plate of an insulating high-temperature resistant substrate. The multiple sets of heating units form a heating resistance layer. Each set of heating units includes multiple electric heating elements that are Peltier exothermic and Joule thermally coupled as described above. An insulating high-temperature resistant heating substrate is disposed directly above the heating resistance layer. The heating resistance layer releases heat outward through the insulating high-temperature resistant heating substrate.

[0029] The aforementioned electric heating device, which couples Peltier exothermic heat transfer with Joule heating, comprises multiple heating units separated by vertically arranged partitions fixed to an insulating high-temperature resistant substrate. The partitions separate adjacent heating units, reduce lateral heat transfer, and improve temperature distribution uniformity. Support plates I are located at both ends of the insulating high-temperature resistant substrate to support and limit the heating resistance layer.

[0030] The aforementioned electric heating device with Peltier exothermic and Joule thermal coupling includes a support plate II between a support plate I and an adjacent heating unit. The support plates I and II are arranged parallel to each other and a spring is provided between them. The spring provides continuous preload to compensate for dimensional changes caused by thermal expansion and contraction and reduce thermal stress concentration. The tops of the partition plate and the support plate II are in contact with the insulating high-temperature resistant heating substrate, providing multi-point support. The two ends of the partition plate, support plate I, and support plate II are connected by connecting rods to form a frame-type support structure, thereby improving the overall rigidity and structural stability of the device, alleviating thermal mismatch stress, reducing warping deformation, and improving the reliability and service life of long-term high-temperature operation.

[0031] The aforementioned electric heating device, which couples Peltier exothermic and Joule thermal coupling, comprises multiple electric heating elements spaced apart within predetermined grooves parallel to each other on the inner side panel of an insulating high-temperature resistant substrate. The insulating high-temperature resistant substrate has a thickness of 8-12 mm; the insulating high-temperature resistant heating substrate has a thickness of 2-3 mm. Both the insulating high-temperature resistant substrate and the insulating high-temperature resistant heating substrate are made of alumina or zirconium oxide, both possessing the common advantages of high temperature resistance, high strength, good insulation, and excellent chemical stability. The insulating high-temperature resistant substrate bears the electrical insulation requirements between the heating resistance layer and the external environment. If the thickness of the insulating high-temperature resistant substrate is <8 mm: the substrate lacks rigidity, and the heating resistance layer is prone to bending or cracking due to mechanical stress or thermal deformation after embedding; if the thickness is >12 mm: the substrate is too heavy, increasing the overall size and weight of the device, and also increasing the difficulty of processing the predetermined grooves, easily leading to problems such as uneven sidewalls and residual impurities at the bottom, affecting the adhesion between the heating resistance layer and the insulating high-temperature resistant substrate; the insulating high-temperature resistant heating substrate should not be too thick, as this may cause poor heat dissipation and reduce the thermal efficiency of the heater.

[0032] The insulating high-temperature resistant substrate has predetermined grooves corresponding to the electric heating element, and the electric heating element is embedded in the predetermined groove on the insulating high-temperature resistant substrate that matches it. Grooves of a specific shape (i.e., "predetermined grooves") are pre-designed and machined on the insulating high-temperature resistant substrate; the shape and size of these predetermined grooves match the electric heating element. Subsequently, the electric heating element is embedded into these corresponding predetermined grooves, thereby achieving the fixation and positioning of the electric heating element on the insulating high-temperature resistant substrate. This structural design aims to provide installation space for the electric heating element, enabling it to be firmly bonded to the insulating high-temperature resistant substrate. Predetermined structures are formed on the insulating high-temperature resistant substrate through processes such as high-temperature sintering, machining, chemical etching, and laser cleaning to provide predetermined grooves for embedding the electric heating element. The electric heating element is attached to the insulating high-temperature resistant substrate through processes such as embedding. The embedding process has the advantages of convenient construction of the electric heating element structure, low cost, and simple manufacturing process, while also allowing for the replacement of materials constituting the N-type and P-type thermoelectric arms at any time, exploring more possibilities. Furthermore, a predetermined pattern may be provided on the bottom of the electric heating element and the corresponding predetermined groove, the predetermined pattern being a serpentine or grid pattern. The predetermined pattern can also be determined according to specific circumstances and is not limited thereto.

[0033] The aforementioned electric heating device, which couples Peltier exothermic and Joule thermal coupling, has an insulating adhesive layer covering the area of ​​the insulating high-temperature resistant substrate not covered by the electric heating element. The insulating adhesive layer is made of aerogel coating. To improve the thermal efficiency and safety of the electric heater, the electric heating element needs to have good insulation and sealing properties. Due to the embedded structure of the insulating high-temperature resistant substrate, some areas are not covered by the heating resistance layer, resulting in exposed areas. The insulating adhesive layer covers these areas. When selecting the material for the insulating adhesive layer, the operating temperature range, operating voltage, and high-temperature resistance of the electric heater need to be considered. The insulating adhesive layer can be prepared using a high-temperature resistant flexible material. Specifically, the high-temperature resistant flexible material should be able to withstand temperatures as low as 800℃, and preferably maintain excellent thermal stability for a long period at around 1400℃. The material used to prepare the heat insulation adhesive layer can be an aerogel coating. The brand of the aerogel coating is Libigao. Its components include the following parts by weight: 5-15 parts of silica, 5-15 parts of titanium dioxide, 15-25 parts of ceramic microspheres, 30-40 parts of deionized water, and 25-40 parts of waterborne acrylic copolymer.

[0034] The method for preparing the heat-insulating adhesive layer is as follows: the aerogel coating is uniformly applied to the area on the surface of the insulating high-temperature resistant substrate that does not have a predetermined groove (this can be done by spraying, brushing, etc.), with a coating thickness of 1-2 mm to ensure the uniformity and thickness of the coating; it can also be determined according to the specific situation.

[0035] The final heating resistance layer has an overall resistivity of 4.09 × 10⁻ 3 -4.5×10⁻ 3 Ω·cm, at this point, the resistivity range of the alloy is adjustable, and it works synergistically with N and P-type thermoelectric arms to stabilize the alloy while also exhibiting Seebeck coefficient enhancement, high-temperature oxidation resistance, and high stability; the coefficient of linear expansion is 6×10. ⁻6 -12×10 -6 / K, preferably 8×10 ⁻6 -10×10 -6 / K, within this range, a dual synergy of "minimizing thermal stress" and "stabilizing electrical conductivity" is achieved, which can meet the requirements for long-term service at medium and high temperatures (below 800℃).

[0036] The height of the heating resistance layer is 10-15 mm, meaning the height of the nickel-chromium alloy layer is 10-15 mm, preferably 11-13 mm. This height allows the heating resistance layer to better fill the predetermined groove on the insulating high-temperature resistant substrate. If the height is <10 mm: the Joule heating power is insufficient, the heating efficiency is <70%, the heating resistance layer has poor rigidity and is prone to bending after thermal shock cycling; if the thickness is >15 mm, the heating rate slows down, energy consumption increases; and accumulated thermal stress leads to interface peeling and substrate cracking.

[0037] Thirdly, the present invention also provides a method for preparing an electric heating device coupled with Peltier exothermic and Joule thermal coupling, comprising the following steps:

[0038] Step 1: Prepare nickel-chromium alloy, p-type thermoelectric arm, and N-type thermoelectric arm respectively; the p-type thermoelectric arm and N-type thermoelectric arm are prepared by doping Mg2Si with different elements; the material of the p-type thermoelectric arm is Mg2Si doped with Li. 1.97 Li 0.03 Si, the material of the N-type thermoelectric arm is Mg2Si doped with Bi element. 2.08 Si 0.97 Bi 0.03 The chemical composition of the nickel-chromium alloy is Ni-xCr, where x represents the mass percentage of Cr in the nickel-chromium alloy, and x = 10~20 wt.%; the p-type thermoelectric arm and the N-type thermoelectric arm are pre-treated by annealing in an inert atmosphere before assembly, and then cooled to room temperature to obtain the pre-treated p-type thermoelectric arm and N-type thermoelectric arm. The annealing temperature is 400~600℃ and the annealing time is 3~4h.

[0039] Step 2: Connect the p-type thermoelectric arm, the nickel-chromium alloy, and the N-type thermoelectric arm in series. An interface buffer layer is provided at the interface between the nickel-chromium alloy and the p-type and N-type thermoelectric arms. This interface buffer layer is a graphene buffer layer, formed by burying the nickel-chromium alloy in graphite powder at 700-900℃ for 7-9 hours, resulting in a buffer layer on the surface of the nickel-chromium alloy. The interface buffer layer is connected to the p-type and N-type thermoelectric arms via a conductive silver paste layer, completing the assembly of the electric heating element.

[0040] Step 3: Embed the assembled multiple electric heating elements on the inner side plate of the insulating high-temperature resistant substrate to form a heating resistance layer, and place an insulating high-temperature resistant heating substrate on top of the heating resistance layer to obtain an electric heating device that is coupled with Peltier exothermic and Joule thermal coupling.

[0041] In the above-mentioned method for preparing an electric heating device with Peltier exothermic and Joule thermal coupling, in step three, multiple assembled electric heating elements are embedded in the inner side plate of an insulating high-temperature resistant substrate to form a heating resistance layer. An insulating high-temperature resistant heating substrate is placed above the heating resistance layer, and a heat-insulating adhesive layer is applied to the area of ​​the insulating high-temperature resistant substrate that is not covered by the electric heating elements, thereby obtaining an electric heating device with Peltier exothermic and Joule thermal coupling.

[0042] The technical solution of the present invention achieves the following beneficial technical effects:

[0043] 1. This invention uses "P-type Mg 1.97 Li 0.03 Si thermoelectric arm - nickel-chromium alloy - N-type Mg 2.08 Si 0.97 Bi 0.03 The thermoelectric arms are connected in series, and the height of the N and P type thermoelectric arms on both sides is lower than that of the nickel-chromium alloy. Meanwhile, the nickel-chromium alloy and the P type Mg... 1.97 Li 0.03 Si thermoelectric arm, N-type Mg 2.08 Si 0.97 Bi 0.03 Graphene buffer layers are introduced between the thermoelectric arms, and these buffer layers are connected to the p-type and N-type thermoelectric arms via conductive silver paste layers. The synergistic effect of these techniques reduces interfacial thermal stress during heterogeneous material pairing, regulates electron carrier concentration, avoids substrate damage, absorbs thermal deformation, and enhances the Seebeck coefficient, thereby improving the performance of p-type Mg... 1.97 Li 0.03 Si thermoelectric arm, N-type Mg 2.08 Si 0.97 Bi 0.03The thermal expansion and resistivity of the thermoelectric arm and the Ni-Cr alloy are more compatible, which improves the synergistic effect of Peltier heat release and Joule heat, thereby improving the electrothermal conversion efficiency. When applied to an electric heater, the current simultaneously triggers the Joule heat of the nickel-chromium alloy and the Peltier heat of the thermoelectric arm interface. The two types of heat radiation are directed vertically upward and radiate towards the insulating high-temperature resistant heating substrate, reducing heat loss.

[0044] 2. This invention effectively reduces residual stress and thermal mismatch stress caused by different expansion coefficients in the manufacturing process of electric heating elements by introducing a graphene buffer layer, thereby preventing cracking and improving the durability of the electric heating elements. Furthermore, by embedding a nickel-chromium alloy in graphite powder and sintering it, the resulting graphene buffer layer contains a certain amount of C-Cr and C-Ni bonds. Carbon atoms can provide additional electron carriers, leading to an increase in electron concentration and thus reducing resistivity. The heterojunction interface formed by the metal carbide phase and the matrix metal phase introduces a potential barrier. Driven by heat flow, high-energy carriers can more easily pass through these barriers, while low-energy carriers are scattered back. Although the increased carrier concentration leads to a decrease in resistivity, the higher contribution of high-energy carriers results in an increase in the average carrier energy (relative to the Fermi level), thereby enhancing the Seebeck coefficient and strengthening the Peltier exothermic synergistic effect. Moreover, this invention reduces the material preparation time by sintering the Ni-Cr alloy to prepare the graphene buffer layer, significantly reducing production costs and making electric heaters using electric heating elements more competitive in the market.

[0045] 3. This invention uses conductive silver paste instead of tin solder. The conductive silver paste layer is formed by low-temperature curing (80~150℃), avoiding damage to the substrate. After curing, the conductive silver paste layer has flexibility (elongation at break ≥15%) and can absorb thermal deformation. Combined with a graphene buffer layer, it further reduces interfacial thermal stress. At the same time, the silver powder content in the conductive silver paste layer is ≥85%, and the contact resistance is ≤1×10⁻⁶. -3 Ω・cm 2 This ensures smooth electrical transmission, and the paste-like form can fill the interface gaps and increase the contact area.

[0046] 4. The height of the N- and P-type thermoelectric arms on both sides of the electric heating element of this invention is lower than that of the Ni-Cr alloy. Assuming the thermoelectric arms and the Ni-Cr alloy are of the same height, the exposed area of ​​the sidewalls of the thermoelectric arms is large, and Peltier heat will be shunted. When the height of the thermoelectric arms is reduced, the lateral heat dissipation path is reduced, and the heat flow concentration is increased. This causes the location of Peltier heat generation to spatially overlap with the Joule heat source of the Ni-Cr alloy, and after coupling with the Joule heat generated by the Ni-Cr alloy, the heat is uniformly released outward through the insulating high-temperature resistant heating substrate, thereby achieving uniformity and concentration of heat flow direction, reducing heat loss, and improving electrothermal conversion efficiency.

[0047] 5. This invention precisely controls the resistance values ​​of the Ni-Cr alloy, the p-type thermoelectric arm, and the N-type thermoelectric arm, avoiding heating imbalances caused by sudden changes in local resistance. Furthermore, through synergy with other techniques, it stabilizes the overall CTE of the heating resistance layer at 6.0 × 10⁻⁶. ⁻6 –12.0×10 ⁻6 / K further alleviates the thermal stress between the heating resistance layer and the insulating high-temperature resistant substrate, reducing interface peeling or substrate cracking.

[0048] 6. The electric heating element of this invention has a relatively simple structure, which reduces the potential for malfunctions during operation. The Ni-Cr alloy, along with P-type and N-type thermoelectric arms, are embedded in an insulating high-temperature resistant substrate to form a heating resistance layer. If the material filling the layer is damaged during prolonged operation, it can be replaced promptly. Furthermore, the simplified structure allows for greater flexibility in future design iterations, making customization to specific needs easier. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the structure of the electric heating element of the present invention;

[0050] Figure 2 This is a schematic diagram of the structure of the electric heating device assembled from the various parts of the present invention.

[0051] Reference numerals: 1. Insulating high-temperature resistant substrate; 2. Insulating high-temperature resistant heating substrate; 3. Heating resistance layer; 4. Interface buffer layer; 5. Thermal insulation adhesive layer; 6. Conductive silver paste layer; 7. P-type thermoelectric arm; 8. N-type thermoelectric arm; 9. Nickel-chromium alloy; 10. Partition plate; 11. Support plate I; 12. Support plate II; 13. Connecting rod. Detailed Implementation

[0052] Example 1

[0053] like Figure 1 As shown, in an electric heating element that couples Peltier exothermic and Joule thermally, the p-type thermoelectric arm 7, the nickel-chromium alloy 9, and the N-type thermoelectric arm 8 are connected in a straight line in sequence, and the heights of the N-type and p-type thermoelectric arms on both sides are the same and lower than the height of the nickel-chromium alloy.

[0054] The p-type thermoelectric arm 7 and the N-type thermoelectric arm 8 are made of Mg2Si by doping with different elements. An interface buffer layer 4 is provided at the interface between the nickel-chromium alloy 9 and both the p-type and N-type thermoelectric arms 7 and 8. This design employs a p-type-metal-N-type connection method, which can generate a large amount of Joule heat through the resistive properties of the metal. Simultaneously, when electrons flow from a higher energy level conductor to a lower energy level conductor under the influence of an electric field, these electrons undergo a downward transition at the interface, macroscopically manifesting as exothermic heating. This coupling effect of resistance heating and Peltier exothermic heating effectively improves the efficiency of electric heating.

[0055] The p-type thermoelectric arm is made of Mg2Si doped with Li element. 1.97 Li 0.03 Si, the material of the N-type thermoelectric arm is Mg2Si doped with Bi element. 2.08 Si 0.97 Bi 0.03 p-type Mg 1.97 Li 0.03 Si and N-type Mg 2.08 Si 0.97 Bi 0.03 Both belong to the category of doped Mg₂Si-based semiconductor thermoelectric materials, whose resistivity is mainly determined by both carrier concentration and mobility. Li doping, as an acceptor doping, can transform Mg₂Si into a p-type semiconductor, while Bi doping, as a donor doping, can increase the electron carrier concentration to form an N-type semiconductor. 1.97 Li 0.03 The resistivity of Si is approximately 1.8 × 10⁻⁶. -3 Ω·cm, N-type Mg 2.08 Si 0.97 Bi 0.03 Resistivity approximately 2.2 × 10⁻⁶ -3 Ω·cm.

[0056] Mg 1.97 Li 0.03 The specific preparation steps for Si are as follows: high-purity Mg powder (7.8% excess to compensate for volatilization), Si powder, and Li... 13 The mass ratio of Si4 powder is 110:59.5:1. Mg powder, Si powder, and Li powder are weighed separately. 13 Si4 powder was mixed and ground to obtain a mixed powder. All weighing, mixing, and grinding operations were carried out in a glove box. The mixed powder was cold-pressed into cylindrical blocks (pressure 200-400 MPa, holding for 5-20 minutes). The cylindrical blocks were placed in a tube furnace and heated and held at 500-600℃ for 5-10 minutes under argon protection to obtain loose blue Mg2Si powder. The reaction product was ground and sieved to obtain Mg. 1.97 Li 0.03Si fine powder. Mg 1.97 Li 0.03 Si fine powder is loaded into a high-purity graphite mold, vacuumed, heated, pressurized, and held at that temperature (800-1000℃, 20-50 MPa, for 3-10 minutes). After cooling, Mg is obtained. 1.97 Li 0.03 Si high-density bulk sample.

[0057] Mg 2.08 Si 0.97 Bi 0.03 The specific preparation steps are as follows: Accurately weigh high-purity Mg, Si, and Bi powders (Mg in excess at 7.8% and the mass ratio of Mg, Si, and Bi powders being 9:4.5:1), mix and grind them to obtain a mixed powder. Place the mixed powder into a quartz tube, evacuate the tube, and seal it. Ignite the tube to initiate a self-propagating high-temperature reaction, rapidly synthesizing Mg. 2.08 Si 0.97 Bi 0.03 Powder. Mg 2.08 Si 0.97 Bi 0.03 The powder is ground to obtain a fine powder, which is then placed into a graphite mold and sintered in an SPS (temperature 800–1000℃, pressure 20–50 MPa, holding time 3–10 minutes) to obtain Mg. 2.08 Si 0.97 Bi 0.03 The high-density bulk sample was used as an N-type thermoelectric arm.

[0058] Before assembling the p-type thermoelectric arm 7 and N-type thermoelectric arm 8 into the electric heating element, they are first subjected to annealing pretreatment in an inert atmosphere. Specifically, the p-type and N-type thermoelectric arms, which are prepared by doping Mg2Si with different elements, are heated to 500℃ in an inert atmosphere for 4 hours and then naturally cooled. This is used to clean the Mg element on the surface of the Mg2Si sample, thereby purifying the material and preventing the sample from volatilizing and contaminating the base during subsequent heating.

[0059] In this embodiment, a Ni-15Cr alloy is used. Ni particles and Cr particles are weighed at a mass ratio of 85:15, with the Cr particles accounting for 0.5% more of the total mass than the 85:15 ratio of nickel to chromium particles. This is to offset the chromium loss during the vacuuming and high-temperature refining stages. The weighed nickel and chromium particles are then mixed, ground, placed in a mold, and placed in a hot press furnace under vacuum. The particles are then melted and solidified under high temperature and pressure (1100~1250℃, 20~40MPa) to obtain the Ni-15Cr alloy. Subsequently, the Ni-15Cr alloy is placed in graphite powder and calcined at 800℃ for 8 hours to form a graphene buffer layer on the surface of the Ni-15Cr alloy, resulting in a Ni-15Cr alloy with a graphene buffer layer on the outer surface. The thickness of the interface buffer layer 4 is 20±5μm. The graphene buffer layer can compensate for differences in thermal expansion and reduce interfacial thermal stress. Ni-15Cr alloy (with graphene buffer layer): room temperature resistivity 1.02×10⁻⁶ -4 Ω·cm (slightly lower than pure Ni-15Cr, due to the graphene buffer layer providing additional conductive channels). The interface buffer layer 4 is connected to the p-type thermoelectric arm and the n-type thermoelectric arm through a conductive silver paste layer 6 (the conductive silver paste layer contains ≥85% silver powder) to form an electric heating element.

[0060] An insulating high-temperature resistant substrate 1 with a thickness of 10 mm was prepared by high-temperature sintering, machining and laser cleaning of alumina ceramic, and a predetermined groove was processed on the insulating high-temperature resistant substrate 1; an aerogel coating was uniformly applied to the area on the surface of the insulating high-temperature resistant substrate 1 without the predetermined groove, and the coating thickness was 1-2 mm.

[0061] like Figure 2 As shown, an electric heating device is assembled. The electric heating device includes multiple sets of spaced heating units embedded in the inner side panel of an insulating high-temperature resistant substrate 1. These heating units are separated by vertically arranged partitions 10, which are fixed to the insulating high-temperature resistant substrate 1. These partitions separate adjacent heating units, reduce lateral heat transfer, and improve temperature distribution uniformity. Support plates I 11 are provided at both ends of the insulating high-temperature resistant substrate 1 to support and limit the heating resistance layer 3. Alternatively, a support plate II 12 can be provided between the support plate I 11 and adjacent heating units. The support plates I 11 and II 12 are arranged parallel to each other, and multiple springs are provided between them. The springs provide continuous preload to compensate for dimensional changes caused by thermal expansion and contraction, reducing thermal stress concentration. The tops of partition 10 and support plate II 12 are in contact with the insulating high-temperature resistant heating substrate 2, forming multi-point support for it; the two ends of partition 10, support plate I 11 and support plate II 12 are connected by connecting rod 13 to form a frame support structure, thereby improving the overall rigidity and structural stability of the device, relieving thermal mismatch stress, reducing warping deformation, and improving the reliability and service life of long-term high-temperature operation.

[0062] Multiple heating units form a heating resistance layer 3. Each heating unit includes multiple electric heating elements that are Peltier exothermic and Joule thermally coupled. These assembled electric heating elements are embedded in predetermined grooves on the inner side panel of an insulating high-temperature resistant substrate 1 to form the heating resistance layer 3. An insulating adhesive layer 5, made of aerogel coating, covers the areas of the insulating high-temperature resistant substrate not covered by the electric heating elements. An insulating high-temperature resistant heating substrate 2 (2.5 mm thick, made of alumina) is positioned directly above the heating resistance layer 3, through which the heating resistance layer 3 releases heat outwards.

[0063] The overall height of heating resistance layer 3 is 10 mm, with an equivalent resistivity of 4.22 × 10⁻⁶. -3 Ω·cm, the overall linear expansion coefficient is (9±1)×10 -6 / K. The electrothermal conversion efficiency is increased to approximately 88.6%, while maintaining a good thermal expansion match between the heating resistance layer 3 and the insulating high-temperature resistant substrate 1, reducing the interfacial stress caused by thermal mismatch during high-temperature cycling, thereby reducing the risk of peeling of the graphene buffer layer from the thermoelectric arm and cracking of the insulating high-temperature resistant substrate.

[0064] Example 2

[0065] The difference from Example 1 is that, based on Example 1, the Cr content of the Ni-Cr alloy is changed, and the Ni:Cr mass ratio is adjusted to 9:1 (i.e., Ni-10Cr), while other parameters remain unchanged. The specific preparation process is as follows: Ni particles and Cr particles are weighed according to a mass ratio of 9:1, with the Cr particle mass exceeding the total mass by 0.5% to offset chromium loss during the vacuuming and high-temperature refining stages. Subsequently, the Ni-10Cr alloy is prepared by sintering in a hot press furnace, as in Example 1.

[0066] In this embodiment, the overall resistivity of the heating resistance layer 3 composed of Ni-10Cr reaches approximately 4.09 × 10⁻⁶. -3 The overall linear expansion coefficient is controlled within (7±1)×10 Ω·cm. -6 Within the range of / K. When the Cr content is adjusted from 15% to 10% (i.e., from Ni-15Cr to Ni-10Cr), the resistivity of the alloy decreases significantly. The reduced solid solution of Cr atoms in the Ni face-centered cubic lattice leads to a decrease in the degree of lattice distortion, a significant reduction in impurity scattering and phonon scattering of free electrons, an increase in the mean free path of electrons, and a decrease in Joule heating under the same current. Ultimately, the electrothermal conversion efficiency is slightly lower than that of Example 1, at approximately 85.4%, and the graphene buffer layer and thermoelectric arm are less prone to peeling off.

[0067] Example 3

[0068] The difference from Example 1 is that, based on Example 1, the Cr content of the Ni-Cr alloy is changed, and the Ni:Cr mass ratio is adjusted to 80:20 (i.e., Ni-20Cr), while other parameters remain unchanged. The specific preparation process is as follows: Ni particles and Cr particles are weighed according to a mass ratio of 80:20, with the Cr particle mass exceeding the total mass by 0.5% to offset chromium loss during the vacuuming and high-temperature refining stages. Subsequently, the Ni-20Cr alloy is prepared by sintering in a hot press furnace, as in Example 1.

[0069] In this embodiment, the overall resistivity of the heating resistance layer 3 composed of Ni-20Cr reaches approximately 4.5 × 10⁻⁶. -3 The overall linear expansion coefficient is controlled within (11.5±0.5)×10 Ω·cm. -6 Within the range of / K, Ni-Cr alloys are typical solid solution alloys, with Cr atoms dissolved into the face-centered cubic lattice of Ni. The difference in atomic radius between Cr (0.128 nm) and Ni (0.125 nm) causes lattice distortion. The presence of Cr atoms severely interferes with the directional movement of free electrons in Ni, increasing the probability of electron collisions with the lattice (impurity scattering + phonon scattering). When the Cr content is increased from 15% to 20%, the resistivity of the Ni-Cr alloy increases significantly. This is due to the increased lattice distortion caused by the large amount of Cr atoms dissolved in solid solution, which enhances the scattering of electrons by impurities and phonons. The final electrothermal conversion efficiency is slightly higher than that in Example 1, reaching approximately 89.3%. However, the coefficient of linear expansion increases significantly, resulting in poorer thermal matching with the graphene buffer layer and the Mg2Si thermoelectric arm. The interfacial thermal stress increases significantly at high temperatures. Although the high-temperature oxidation resistance is slightly improved, the oxide film tends to thicken and the internal stress increases, posing a risk of localized peeling. The temperature coefficient of resistance (TCR) increases, the high-temperature resistance stability decreases, and the overall toughness is also reduced.

[0070] In summary, the Ni-15Cr alloy achieves an optimal balance in terms of resistivity, coefficient of linear expansion, high-temperature oxidation resistance, temperature coefficient of resistance, and long-term stability. Its moderate resistivity ensures sufficient Joule heat output while also providing good compatibility with p / N type Mg2Si thermoelectric arms.

[0071] Example 4

[0072] The difference from Example 1 is that, based on the heating resistance layer height of 10mm in Example 1, the height of the heating resistance layer 3 is changed to 12mm, while other parameters and methods remain unchanged.

[0073] Increased thickness enhances device rigidity and improves Joule heating power, but slightly reduces the heating rate and decreases thermal stress accumulation. Continued thermal stress accumulation can lead to microstructural damage at the interface, forming microcracks. If the thermal stress level is low, these microcracks may close due to surface tension or self-healing effects, preventing further development into macroscopic cracks. The total elastic strain energy stored in the material is significantly reduced, avoiding separation or detachment at the interface where the two materials meet. Device rigidity is enhanced, and no bending occurs after thermal shock cycling.

[0074] Example 5

[0075] The difference from Example 1 is that, based on Example 1, the material of the insulating high-temperature resistant substrate 1 is changed from alumina to zirconium oxide, while other parameters and methods remain unchanged. Zirconia has better high-temperature resistance (>1200℃), improving the high-temperature stability of the device, but its slightly lower thermal conductivity leads to a slower heating rate, reducing the risk of cracking of the insulating high-temperature resistant substrate 1.

[0076] Comparative Example 1

[0077] The difference from Example 1 is that, based on Example 1, only Ni-15Cr nickel-chromium alloy is used as the heating element, and the P-type and N-type thermoelectric arm structures are omitted, while the rest of the structure remains the same. This structure relies solely on the nickel-chromium alloy to generate Joule heat. Although it has good heating stability, it lacks the Peltier exothermic effect generated by the thermoelectric interface, and cannot achieve synergistic coupling of the two heat sources, resulting in relatively low heat utilization. Under the same test conditions, its electrothermal conversion efficiency is approximately 76.5%.

[0078] The differences between the above embodiments and comparative examples are summarized in Tables 1 to 3 below:

[0079] Table 1. Raw material list for Examples 1-5 and Comparative Example 1

[0080]

[0081] Table 2 Comparison of Indicators between Examples 1-3 and Comparative Examples

[0082]

[0083] Table 3 Comparison of indicators between Example 1 and Examples 4 and 5

[0084]

[0085] Table 2 shows that the electrothermal conversion efficiency of the comparative examples is lower than that of Examples 1-3, and the heat utilization rate and heat flow concentration capacity are limited. This indicates that using nickel-chromium alloy alone is insufficient to fully utilize the heat flow concentration and heat gain effects. Furthermore, Examples 1-3 demonstrate that the Ni-15Cr alloy achieves the best balance between electrothermal conversion efficiency and other performance characteristics. Table 3 also shows that using a heating resistance layer height of 12 mm and a zirconium oxide insulating high-temperature substrate results in superior performance in all aspects.

[0086] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. An electric heating element coupled with Peltier exothermic and Joule thermal coupling, characterized in that, The electric heating element is composed of a p-type thermoelectric arm (7), a nickel-chromium alloy (9), and an N-type thermoelectric arm (8) connected in a straight line. The N-type and p-type thermoelectric arms on both sides are of the same height and are lower than the height of the nickel-chromium alloy. The chemical composition of the nickel-chromium alloy (9) is Ni-xCr, where x represents the mass percentage of Cr in the nickel-chromium alloy, and x = 10~20 wt.%. The p-type thermoelectric arm (7) and the N-type thermoelectric arm (8) are respectively made of Mg2Si by doping with different elements. An interface buffer layer (4) is provided at the interface connection between the nickel-chromium alloy (9) and the p-type thermoelectric arm (7) and the N-type thermoelectric arm (8) to realize the coupling of Peltier exothermic and Joule heat and improve the electrothermal conversion efficiency. The interface buffer layer (4) is a graphene buffer layer. The graphene buffer layer is formed on the surface of the nickel-chromium alloy by placing the nickel-chromium alloy in graphite powder and calcining it at 700~900℃ for 7~9h. The interface buffer layer (4) is connected to the p-type thermoelectric arm (7) and the N-type thermoelectric arm (8) respectively through a conductive silver paste layer (6).

2. The electric heating element according to claim 1, characterized in that, The p-type thermoelectric arm (7) is made of Mg2Si doped with Li element. 1.97 Li 0.03 Si, the material of the N-type thermoelectric arm (8) is Mg2Si doped with Bi element. 2.08 Si 0.97 Bi 0.03 .

3. An electric heating element with Peltier exothermic and Joule thermal coupling according to claim 1 or 2, characterized in that, Before assembly, the p-type thermoelectric arm (7) and N-type thermoelectric arm (8) are pre-treated by annealing in an inert atmosphere and then cooled to room temperature to obtain the pre-treated p-type thermoelectric arm and N-type thermoelectric arm. The annealing temperature is 400~600℃ and the annealing time is 3~4h.

4. The electric heating element according to claim 1, characterized in that, The thickness of the interface buffer layer (4) is 15-25 μm.

5. The electric heating element according to claim 1, characterized in that, The silver powder content in the conductive silver paste layer (6) is ≥85%.

6. An electric heating device with Peltier exothermic and Joule thermal coupling, characterized in that, It includes multiple sets of spaced heating units embedded in the inner side panel of an insulating high-temperature resistant substrate (1), the multiple sets of heating units forming a heating resistance layer (3), each set of heating units including multiple electric heating elements that are Peltier exothermic and Joule thermally coupled as described in any one of claims 1 to 5, an insulating high-temperature resistant heating substrate (2) is provided directly above the heating resistance layer (3), and the heating resistance layer (3) releases heat outward through the insulating high-temperature resistant heating substrate (2).

7. The electric heating device according to claim 6, characterized in that, Multiple heating units are separated from each other by vertically arranged partitions (10). The partitions (10) are fixed on an insulating high-temperature resistant substrate (1). Support plates I (11) are provided at both ends of the insulating high-temperature resistant substrate (1).

8. The electric heating device according to claim 7, characterized in that, A support plate II (12) is provided between the support plate I (11) and the adjacent heating unit. The support plate I (11) and the support plate II (12) are arranged in parallel and a spring is provided between them. The tops of the partition plate (10) and the support plate II (12) are in contact with the insulating high-temperature resistant heating substrate (2), and the two ends of the partition plate (10), the support plate I (11) and the support plate II (12) are connected by a connecting rod (13).

9. The electric heating device according to claim 8, characterized in that, Multiple electric heating elements are interspersed in predetermined grooves parallel to each other on the inner side panel of the insulating high-temperature resistant substrate (1). The thickness of the insulating high-temperature resistant substrate (1) is 8-12 mm; the thickness of the insulating high-temperature resistant heating substrate (2) is 2-3 mm; the materials of the insulating high-temperature resistant substrate (1) and the insulating high-temperature resistant heating substrate (2) are alumina or zirconium oxide.

10. The electric heating device according to claim 9, characterized in that, A heat-insulating adhesive layer (5) is applied to the area of ​​the insulating high-temperature resistant substrate (1) where the electric heating element is not covered. The heat-insulating adhesive layer (5) is made of aerogel coating material. The overall resistivity of the formed heating resistance layer (3) is The coefficient of linear expansion is The height is 10-15mm.

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