Fish scale spliced heat-insulating reflective screen and design method

Abstract

This invention discloses a fish-scale-shaped spliced ​​heat-insulating reflector and its design method, relating to the field of vacuum heat treatment equipment technology. The heat-insulating reflector includes at least one layer of heat-insulating plate, which is bolted to a frame. The heat-insulating plate includes: a central heat-insulating sub-plate, circular in shape and located at the center; at least one annular heat-insulating sub-plate, radially distributed outside the central heat-insulating sub-plate; the annular heat-insulating sub-plate is formed by splicing multiple fan-shaped heat-insulating units circumferentially; wherein a first gap is provided between adjacent fan-shaped heat-insulating units; the projection of the first gap onto the heat-insulating plate is a wedge shape that varies radially, being smaller at the inner diameter and larger at the outer diameter. Based on the same inventive concept, a design method for the heat-insulating reflector is also disclosed. This heat-insulating screen effectively avoids component interference or heat radiation leakage caused by thermal deformation to a certain extent, while ensuring the assembly stability and heat insulation performance between multiple layers of heat-insulating plates and between each fan-shaped unit.

Description

Technical Field

[0001] This invention relates to the field of vacuum heat treatment equipment technology, and in particular to a fish-scale spliced ​​heat insulation reflective screen and its design method. Background Technology

[0002] Vacuum furnaces are key equipment widely used in vacuum heat treatment, brazing, sintering, and other processes. Their heat shields, as an important component of the furnace's internal thermal field, primarily serve to shield against thermal radiation and reduce heat loss, thereby ensuring furnace temperature uniformity and reducing energy consumption. With the increasing demands for temperature uniformity and control precision in vacuum heat treatment processes, the structural design and thermal deformation control of the heat shields have become crucial factors affecting equipment performance. Existing vacuum furnace heat shields mostly employ multi-layered metal plates (such as tungsten and molybdenum) stacked together to achieve insulation by reflecting thermal radiation.

[0003] To address these issues, some existing technologies employ segmented, modular heat shield structures. This involves dividing a ring-shaped heat shield sub-panel into multiple sector-shaped units, utilizing the gaps between these units to absorb thermal expansion. However, existing modular heat shield structures often result in heat radiation leakage, leading to poor insulation performance.

[0004] Therefore, it is necessary to provide a fish-scale spliced ​​heat insulation reflector and its design method to effectively compensate for the thermal expansion of the heat insulation board in a high-temperature vacuum environment, avoid component interference or heat radiation leakage caused by thermal deformation, and at the same time ensure the assembly stability and heat insulation performance between multi-layer heat insulation boards and between each sector unit. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a fish-scale spliced ​​heat insulation reflector and its design method. The heat insulation reflector can effectively compensate for the thermal expansion of the heat insulation board to a certain extent in a high-temperature vacuum environment, avoid component interference or heat radiation leakage caused by thermal deformation, and at the same time ensure the assembly stability and heat insulation performance between the multi-layer heat insulation boards and between each sector unit.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a fish-scale-shaped spliced ​​heat-insulating reflective screen, comprising at least one layer of heat-insulating board, which is bolted to a frame; the heat-insulating board includes:

[0008] The central insulation panel is circular and located in the center.

[0009] At least one annular heat insulation sub-panel is radially distributed on the outer side of the central heat insulation sub-panel; the annular heat insulation sub-panel is composed of multiple fan-shaped heat insulation units spliced ​​together circumferentially.

[0010] in,

[0011] A first gap is provided between adjacent fan-shaped heat insulation units; the projection of the first gap on a plane parallel to the heat insulation plate is a wedge shape that is smaller at the inner diameter and larger at the outer diameter, which is used to compensate for circumferential displacement caused by thermal expansion.

[0012] Furthermore, the first gap is radially distributed as Gap(r); its value is calculated according to the following formula:

[0013] ,

[0014] In the formula:

[0015] Gap(r) represents the value of the first gap at different radial positions, in mm;

[0016] r is the radius of a point on the sector-shaped heat insulation unit from the center of the circle, in mm;

[0017] α is the coefficient of linear expansion of the material of the sector-shaped heat insulation unit, in units of 1 / ℃;

[0018] ΔT(r) is the temperature rise at a distance r from the center of the circle, in °C.

[0019] φ is the central angle of the sector-shaped heat insulation unit, in radians;

[0020] k is the safety factor, which has no unit.

[0021] Furthermore, a first labyrinth structure extending radially is provided at the assembly surface of the adjacent fan-shaped heat insulation unit; the fitting gap of the first labyrinth structure at room temperature is the first gap, and the radial distribution characteristic of the first gap is Gap(r).

[0022] Furthermore, the safety factor k ranges from 1.015 to 1.035.

[0023] Furthermore, a second labyrinth structure extending circumferentially is provided at the assembly surfaces between the central heat insulation sub-plate and the adjacent annular heat insulation sub-plate, as well as between two adjacent annular heat insulation sub-plates. The fitting gap of the second labyrinth structure at room temperature is the second gap, which is used to compensate for radial displacement caused by thermal expansion.

[0024] Furthermore, a first positioning hole is provided at the center of the central heat insulation sub-plate; a plurality of first straight slots are provided on the outer periphery of the central heat insulation sub-plate, the length direction of the first straight slots being radial to guide the central heat insulation sub-plate to move when it expands radially due to heat; the first positioning hole and the first straight slots are both engaged with the bolts to assemble the central heat insulation sub-plate onto the frame;

[0025] The center distance L between the two arcs of the first straight slot hole satisfies the following formula:

[0026] ,

[0027] In the formula:

[0028] α is the coefficient of linear expansion of the material of the sector-shaped heat insulation unit, in units of 1 / ℃;

[0029] ΔT is the temperature rise at the geometric center of the first straight slot, in °C.

[0030] r is the distance from the center of the bolt that mates with the first straight slot hole to the center of the bolt that mates with the first positioning hole, in mm;

[0031] C is a safety margin, and the value of C is 0.01 to 0.03 times the radius of the bolt that mates with the first straight slot hole, in mm.

[0032] Furthermore, each of the aforementioned fan-shaped heat insulation units has at least one second straight slot hole that slides with the bolt;

[0033] The second straight slot is configured such that when the fan-shaped heat insulation unit is at room temperature, the bolt is located at the end of the second straight slot away from the center of the fan-shaped heat insulation unit.

[0034] When the fan-shaped heat insulation unit is at its operating temperature, the second straight slot moves relative to the bolt due to thermal expansion, and the bolt is located at one end of the second straight slot near the center of the fan-shaped heat insulation unit.

[0035] Furthermore, the fan-shaped heat insulation unit has one and only one second positioning hole near its inner edge; the center of the second positioning hole is located on the axis of symmetry of the fan-shaped heat insulation unit; the distance from the center of the second positioning hole to the inner edge of the fan-shaped heat insulation unit is 1.5 to 2.5 times the radius of the second positioning hole.

[0036] An even number of second straight slots are provided near the outer edge of the fan-shaped heat insulation unit. The position and shape of the even number of second straight slots are symmetrical about the axis of symmetry of the fan-shaped heat insulation unit.

[0037] Wherein, the second straight slot is a straight slot opening, and the angle θ between its length direction and the axis of symmetry of the fan-shaped heat insulation unit is calculated according to the following formula:

[0038] ,

[0039] In the formula:

[0040] The distance from the center of the second positioning hole to the center of the ring is in mm.

[0041] The distance from the center of the second straight slot hole to the center of the ring is expressed in mm.

[0042] The azimuth angle of the center of the second straight slot relative to the axis of symmetry is expressed in radians.

[0043] Furthermore, for any pair of radially adjacent annular heat insulation sub-plates, the inner annular heat insulation sub-plate is defined as the layer closest to the center; the outer annular heat insulation sub-plate is defined as the layer furthest from the center; the value of each second gap, Gap (rad), is calculated using the following formula:

[0044] ,

[0045] In the formula:

[0046] α is the coefficient of linear expansion of the insulation material, in units of 1 / ℃;

[0047] Temperature rise at the outer edge of the inner annular heat insulation plate, unit: °C;

[0048] The radius of the outer edge of the inner annular heat insulation sub-plate, in mm;

[0049] Temperature rise at the inner edge of the outer annular heat insulation panel, unit: °C;

[0050] The distance from the center of the second positioning hole on the outer annular heat insulation plate to the center of the ring, in mm;

[0051] D is the safety margin, which ranges from 0.1 mm to 0.5 mm.

[0052] Based on the same inventive concept, a heat-insulating reflective screen design method is also disclosed, including the following steps:

[0053] S110: Obtain the linear expansion coefficient α, central angle φ, and radial temperature rise ΔT(r) of the fan-shaped thermal insulation unit; and calculate the radial distribution characteristic Gap(r) of the first gap between adjacent fan-shaped thermal insulation units at room temperature, the value of which is calculated by the following formula:

[0054] ,

[0055] In the formula:

[0056] Gap(r) represents the value of the first gap at different radial positions, in mm;

[0057] r is the radius of a point on the sector-shaped heat insulation unit from the center of the circle, in mm;

[0058] α is the coefficient of linear expansion of the material of the sector-shaped heat insulation unit, in units of 1 / ℃;

[0059] ΔT(r) is the temperature rise at a distance r from the center of the circle, in °C.

[0060] φ is the central angle of the sector-shaped heat insulation unit, in radians;

[0061] k is the safety factor, which has no unit.

[0062] S120: The adjacent sides of the adjacent fan-shaped heat insulation units are processed into a structure with a preset included angle, so that a first gap with a radially varying wedge shape and a distribution characteristic of Gap(r) is formed between them at room temperature.

[0063] The present invention has at least the following advantages or beneficial effects:

[0064] The heat-insulating reflective screen design method of this invention employs a technique of setting the first gap between adjacent fan-shaped heat-insulating units at room temperature as a radially varying wedge shape. This first gap has a smaller value at the inner diameter of the fan-shaped heat-insulating unit and a larger value at the outer diameter. This design allows the distribution of the first gap to match the non-uniform radial thermal expansion of the heat-insulating screen under actual operating conditions: the smaller inner diameter of the first gap helps reduce direct leakage of heat radiation through the gap at high temperatures; the larger outer diameter of the first gap provides space to accommodate the larger thermal expansion in that area. Thus, while ensuring the heat insulation effect, it effectively avoids the fan-shaped units from squeezing each other or structural deformation due to limited thermal expansion. Overall, this invention can improve the thermal expansion adaptability of the heat-insulating screen in high-temperature vacuum environments, enhancing its structural stability and heat insulation performance.

[0065] Furthermore, this invention incorporates a first labyrinthine structure between adjacent fan-shaped heat insulation units, and sets the first gap under normal temperature assembly as the calculated Gap(r). This structure, while compensating for thermal expansion, further blocks direct penetration of heat radiation along the circumferential gaps through a labyrinthine, tortuous path, enhancing the sealing effect at the joints of adjacent units and improving the overall heat radiation protection performance of the heat insulation screen.

[0066] Furthermore, this invention limits the value of the safety factor k to between 1.015 and 1.035. This range provides the necessary engineering margin for the design of the first gap to cope with uncertainties such as fluctuations in material parameters and changes in operating conditions, while avoiding excessive increase in the first gap due to excessive margin, which would affect the thermal insulation efficiency. This achieves a balance between compensation reliability, structural safety, and thermal insulation performance.

[0067] Furthermore, this invention employs a technical solution of fixing the fan-shaped heat insulation unit to the frame through a second straight slot, and configures the bolts to be positioned at both ends of the straight slot in cold and hot states, respectively. This structure allows the fan-shaped heat insulation unit to expand freely when heated, while the sliding fit between the bolts and the straight slot guides the expansion direction, preventing the unit from shifting or jamming. This effectively solves the problem of limited thermal expansion displacement under traditional round hole fixing methods, ensuring assembly stability and smooth expansion process. Attached Figure Description

[0068] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0069] Figure 1 Flowchart of the design method for heat-insulating reflective screens;

[0070] Figure 2 The temperature at the center of the outermost layer of insulation board, which is stacked outwards in a staggered manner along the thickness direction, when different safety factor K values ​​are taken;

[0071] Figure 3 A schematic diagram of the fish-scale spliced ​​heat insulation reflective screen;

[0072] Figure 4 This is a schematic diagram of the fish-scale spliced ​​heat insulation and reflective screen from another perspective.

[0073] Figure 5 This is a top view of a single-layer insulation panel;

[0074] Figure 6 A three-dimensional schematic diagram of the central insulation sub-panel;

[0075] Figure 7 Top view of the central insulation panel;

[0076] Figure 8 This is a three-dimensional schematic diagram of the annular heat insulation sub-panel;

[0077] Figure 9 for Figure 8 Enlarged schematic diagram of the structure at point A in the middle;

[0078] Figure 10 This is a top view of the annular heat insulation sub-panel;

[0079] Figure 11 This is a three-dimensional schematic diagram of a fan-shaped thermal insulation unit;

[0080] Figure 12This is a top view of a fan-shaped thermal insulation unit.

[0081] Figure label:

[0082] 1-Insulation board; 11-Central insulation sub-board; 111-First positioning hole; 112-First straight slot hole; 12-Annular insulation sub-board; 121-Fan-shaped insulation unit; 1211-First labyrinth structure; 1212-Second positioning hole; 1213-Second straight slot hole; 1214-Second labyrinth structure;

[0083] 2- Bolts;

[0084] 3-Rack. Detailed Implementation

[0085] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0086] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0087] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0088] In this invention, terms such as "upper," "lower," "left," "right," "front," "back," "vertical," "horizontal," "side," and "bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are only used to facilitate the description of the structural relationships of the various components or elements of this invention and do not specifically refer to any part or element in this invention. They should not be construed as limitations on this invention.

[0089] In this invention, terms such as "fixed," "connected," and "linked" should be interpreted broadly, indicating that the connection can be fixed, integral, or detachable; it can be a direct connection or an indirect connection through an intermediate medium. For researchers or technicians in the field, the specific meaning of the above terms in this invention can be determined according to the specific circumstances, and they should not be construed as limitations on this invention.

[0090] The embodiments of the present invention will be described in detail below.

[0091] This invention discloses a design method for a heat-insulating reflective screen. This method is used to design a fish-scale-shaped, interlocking heat-insulating reflective screen for use in a vacuum furnace. The heat-insulating reflective screen fabricated based on this design method has the following structure. Figures 3 to 12 As shown, it mainly includes multi-layer insulation panels 1, bolts 2 for connection, and a frame 3 for overall support. The frame 3 is typically made of water-cooled steel structure with internal circulating water channels to maintain sufficient structural strength and stability in high-temperature environments. The material of the bolts 2 is compatible with the material of the insulation panels 1, and creep resistance at high temperatures is taken into consideration; for example, they can be made of molybdenum alloy, tungsten alloy, or high-temperature nickel-based alloy.

[0092] Please see Figures 3 to 6 The heat-insulating reflective screen includes at least one heat-insulating plate 1 in the thickness direction. In this embodiment, the number of heat-insulating plates 1 is 15, and they are stacked along the thickness direction. In other embodiments, the number of heat-insulating plate 1 layers can be selected according to the power, operating temperature range, and heat insulation requirements of the vacuum furnace. For example, for furnaces with operating temperatures below 1000°C, 3 to 5 layers can be used; for furnaces with operating temperatures between 1000°C and 1600°C, 5 to 8 layers can be used; and for ultra-high temperature furnaces with operating temperatures exceeding 1600°C, the number of layers can be increased to more than 10 layers.

[0093] Each insulation panel 1 consists of a central insulation sub-panel 11 located at the center and an annular insulation sub-panel 12 arranged around the central insulation sub-panel 11.

[0094] The central heat insulation sub-panel 11 has a complete circular plate structure. Its function is to form a continuous reflective surface in the central area of ​​the heat insulation screen, blocking heat radiation from directly penetrating from the central area. In this embodiment, the five layers of central heat insulation sub-panels 11 closest to the heat source are made of tungsten; in other embodiments, the central heat insulation sub-panels 11 can be made of high-temperature resistant, high-reflectivity materials such as molybdenum plates, tungsten plates, tantalum plates, stainless steel plates, high-temperature nickel-based alloy plates, or graphite plates. Different material choices bring different beneficial effects: molybdenum plates have good high-temperature strength and a low coefficient of linear expansion, which helps to improve structural stability; tungsten plates have extremely high melting points and excellent high-temperature deformation resistance, making them suitable for ultra-high temperature environments; graphite plates have low thermal conductivity and good thermal shock resistance. The central heat insulation sub-panel 11 can be manufactured by processes such as stamping, precision casting, or wire cutting. Its surface can be polished to enhance the reflectivity of heat radiation, thereby further improving the heat insulation efficiency.

[0095] Around the central heat insulation sub-plate 11, at least two layers of annular heat insulation sub-plates 12 are radially distributed. The number of annular heat insulation sub-plates 12 is not fixed, but is determined according to the overall diameter of the heat insulation screen and the width of each annular plate. For example, for furnace bodies with larger diameters, three, four, or even five layers of annular heat insulation sub-plates 12 can be set to ensure that the width of each plate is within a reasonable range, facilitating processing and installation.

[0096] like Figure 8 , Figure 9 and Figure 10 As shown, the annular heat insulation sub-panel 12 is not a single, integral ring, but rather composed of multiple sector-shaped heat insulation units 121 spliced ​​together circumferentially. Each sector-shaped heat insulation unit 121 is roughly fan-shaped, with a smaller inner radius and a larger outer radius. Dividing the annular heat insulation sub-panel 12 into multiple sector-shaped heat insulation units 121 and splicing them together serves to break down the large annular plate into multiple smaller units, facilitating processing and installation. Furthermore, the first gap between the sector-shaped heat insulation units 121 can absorb and compensate for the thermal expansion generated at high temperatures, preventing damage to the overall structure due to thermal stress.

[0097] The number of sector-shaped heat insulation units 121 can be set according to the size of the heat insulation screen. For example, each layer of annular heat insulation sub-panel 12 can be composed of 8, 12, or 16 sector-shaped heat insulation units 121. The manufacturing method of sector-shaped heat insulation units 121 can adopt the same process as the central heat insulation sub-panel 11, including stamping, cutting, precision casting, etc., and after processing, the edges are chamfered and deburred to avoid stress concentration.

[0098] Based on the above structure, the heat-insulating reflective screen design method provided by this invention includes a series of steps to precisely control the assembly relationship between the components. The specific steps are as follows:

[0099] S100: The first gap between adjacent fan-shaped heat insulation units 121 under normal temperature assembly is set to a wedge shape that varies radially, such that the first gap has a smaller value at the inner diameter of the fan-shaped heat insulation unit 121 and a larger value at the outer diameter.

[0100] This step is one of the core aspects of the design method of this invention. Its function is to match the distribution of the first gap with the thermal expansion law of the heat insulation screen under actual working conditions. Specifically, when the vacuum furnace is working, the radial temperature distribution of the heat insulation screen is usually uneven, with the temperature in the outer diameter region usually higher than that in the inner diameter region. Therefore, the thermal expansion of the outer diameter region is also greater than that in the inner diameter region. This uneven temperature distribution stems from the fact that the heating elements are usually arranged around the furnace chamber, as well as the heat dissipation effect at the edge of the heat insulation screen. If the first gap adopts a traditional uniform shape, either the spacing value at the inner diameter is too large, leading to heat radiation leakage, or the spacing value at the outer diameter is too small, causing the units to squeeze each other after thermal expansion. The wedge-shaped first gap design of this invention, which is larger on the outside and smaller on the inside, can just adapt to this uneven thermal expansion. Under high temperature conditions, after each fan-shaped heat insulation unit 121 is heated and expanded, its adjacent sides can just fit together or maintain a small and uniform gap, thereby ensuring the heat insulation effect while avoiding structural interference. The specific value of the first gap of the wedge can be 0.2mm to 0.8mm at the inner diameter and 1.5mm to 5.0mm at the outer diameter, depending on the unit size and operating temperature.

[0101] Specifically, step S100 further includes sub-steps S110 and S120:

[0102] Step S110: Based on the material physical properties of the sector-shaped heat insulation unit 121 and the operating temperature parameters of the vacuum furnace, calculate the radial distribution of the first gap between adjacent sector-shaped heat insulation units 121 under normal temperature assembly. The material physical properties include at least the linear expansion coefficient α of the material, as well as necessary elastic modulus, Poisson's ratio, etc., for more accurate thermal stress analysis. The operating temperature parameters include the highest operating temperature inside the furnace and the radial temperature distribution function ΔT(r). The setting of the spacing values ​​of each point in the first gap is based on scientific calculations in thermodynamics and materials science. In this embodiment, the setting of the spacing values ​​of each point in the first gap is simplified using theoretical formulas; in other embodiments, finite element analysis software can also be used to calculate the temperature field and thermal expansion displacement field. By establishing a three-dimensional model of the heat insulation screen and applying thermal loads and boundary conditions, the displacement of each point under hot conditions can be obtained intuitively.

[0103] Step S120: Based on the calculation results of step S110, the first gap between adjacent sector-shaped heat insulation units 121 under normal temperature assembly is set as a wedge shape that varies radially. This means that during processing and assembly, the adjacent sides of two adjacent sector-shaped heat insulation units 121 are not parallel, but form a small angle, thus naturally forming a wedge-shaped space that gradually increases in size from the inside to the outside between them. This angle is typically between 0.1° and 0.5°, and the specific value is determined by the distribution of Gap(r).

[0104] More specifically, in step S110, the first gap distribution Gap(r) required between adjacent sector-shaped insulation units 121 at room temperature is calculated according to the following formula:

[0105] ,

[0106] In the formula:

[0107] Gap(r) represents the value of the first gap at different radial positions, in mm;

[0108] r is the radius of a point on the sector-shaped heat insulation unit 121 from the center of the circle, in mm;

[0109] α is the coefficient of linear expansion of the material of the sector-shaped heat insulation unit 121, in units of 1 / ℃;

[0110] ΔT(r) is the temperature rise at a distance r from the center of the circle, in °C.

[0111] φ is the central angle of the sector-shaped heat insulation unit 121, in radians;

[0112] k is the safety factor, which has no unit.

[0113] α is the coefficient of linear expansion of the material in sector-shaped insulation unit 121; this coefficient is an inherent property of the material and is usually a function of temperature over a certain temperature range, rather than a constant value. Therefore, the coefficient of linear expansion value at the corresponding temperature should be used. For example, for molybdenum, its average coefficient of linear expansion in the range of 20℃ to 1000℃ is approximately 5.2 × 10⁻⁶. -6 / ℃, and will increase slightly at higher temperatures. This parameter can be obtained from material handbooks, national standards (such as GB / T 4339), or experimental measurements.

[0114] ΔT(r) represents the temperature rise at a distance r from the center of the circle; that is, the difference between the operating temperature and the ambient temperature (usually taken as 20℃). It is a function of the radius r, reflecting the non-uniformity of the radial temperature field. In this embodiment, ΔT(r) can be obtained through thermal simulation analysis; in other embodiments, it can also be measured by arranging thermocouples on the actual furnace body. The measurement points can be arranged equidistantly or unequally along the radial direction to obtain the temperature distribution curve.

[0115] φ is the central angle of the sector-shaped heat insulation unit 121; for example, if a layer of annular heat insulation sub-panel 12 is composed of 9 sector-shaped heat insulation units 121, then the central angle φ of each unit is 40 degrees (which needs to be converted to radians for calculation).

[0116] k is the safety factor; its function is to compensate for the difference between theoretical calculations and actual working conditions, such as fluctuations in material parameters, assembly errors, temperature field measurement errors, and material performance degradation after long-term use. In this embodiment, the value range of the safety factor k is limited to 1.015 to 1.035. By analyzing the measured temperature data at the center of the outermost insulation board under different safety factor K values, such as... Figure 2 As shown, the following pattern can be observed: as the K value increases, the outermost temperature exhibits a trend of first decreasing and then increasing. When the K value is too small (K<1.01), such as K=1.000, the outermost temperature reaches as high as 182.1℃; when K=1.005, the temperature drops to 165.7℃. This indicates that when the K value is too small, thermal expansion compensation is insufficient, assembly errors lead to thermal stress, causing structural deformation and thermal radiation leakage, thus significantly increasing the outermost temperature. When the K value enters 1.010, the temperature has dropped to 148.4℃; while when the K value is in the optimal range of 1.015 to 1.035, the outermost temperature stabilizes between 137.4℃ and 142.8℃, with K=1.020 reaching the lowest point of 137.4℃. Within this range, the temperature is lowest and fluctuates gently, indicating sufficient thermal expansion compensation, the zero thermal stress state structure performs optimally, and thermal radiation leakage is minimized. When the K value is too large (K>1.035), for example, when K=1.040 the temperature rises to 149.0℃, and when K=1.045 and K=1.050 the temperature further rises to 162.3℃ and 168.4℃ respectively. This indicates that an excessively large K value leads to an excessively large first gap under normal temperature assembly. Under hot conditions, the remaining first gap causes a significant increase in heat radiation leakage, and the outermost layer temperature rises again. In summary, the measured data clearly show that the optimal range for the safety factor K is 1.015 to 1.035. Within this range, the outermost layer temperature reaches its lowest and remains stable, the thermal expansion compensation effect of the heat insulation screen is optimal, the heat radiation leakage is minimal, and the overall heat insulation performance is optimal. However, when the K value deviates from this range, whether it is too small or too large, it will lead to a significant increase in the outermost layer temperature and a deterioration in the heat insulation effect.

[0117] Please see Figure 8 , Figure 9 and Figure 10To further enhance the heat radiation protection capability at the joint of adjacent fan-shaped heat insulation units 121, a first labyrinth structure 1211 is provided between adjacent fan-shaped heat insulation units 121. This first labyrinth structure 1211 is not an independent additional component, but is directly formed on the joint side of adjacent fan-shaped heat insulation units 121 through machining (such as milling, wire cutting, or electrical discharge machining). For example, a groove can be machined on the side of one fan-shaped heat insulation unit 121, and a tenon that mates with the groove can be machined on the corresponding side of the adjacent fan-shaped heat insulation unit 121. The cross-sectional shape of the groove and tenon can be rectangular, trapezoidal, or semi-circular. In this embodiment, a rectangular cross-section groove and tenon are used, with a depth of 3mm to 8mm and a width of 2mm to 5mm. When the two are joined, the concave and convex structures interlock to form a tortuous first gap channel. The first gap of the first labyrinth structure 1211 under normal temperature assembly is the Gap(r) calculated by the aforementioned formula. The function of this structure is to prevent heat radiation from penetrating in a straight line even when the first gap exists at high temperatures. Instead, it must undergo multiple reflections and absorptions, thus significantly reducing heat leakage along the circumferential gap. According to the principles of heat transfer, the heat flux of radiative heat is related to the angle factor; the labyrinth structure can reduce the angle factor of linear heat radiation by several times or even an order of magnitude. In other embodiments, multiple concave and convex structures, such as two or three, can be used to form a multi-level labyrinth, further enhancing the heat radiation protection effect. The surface of the labyrinth structure can be roughened to increase the absorption coefficient of heat radiation, thereby further attenuating heat radiation energy.

[0118] Furthermore, this design method further includes the following steps:

[0119] S200: The sector-shaped thermal insulation unit 121 is fixed to the frame 3 using bolts. This step details the installation and fixing method of the sector-shaped thermal insulation unit 121, the key being the design of the fixing holes. Each sector-shaped thermal insulation unit 121 has at least one straight slot hole for sliding engagement with the bolt 2. This straight slot hole is not an ordinary round hole, but an elongated oval hole extending radially along the length of the sector-shaped thermal insulation unit 121, with semi-circular ends. In this embodiment, each sector-shaped thermal insulation unit 121 has two such straight slot holes; in other embodiments, depending on the size of the unit, four or more may be provided. The number of straight slot holes needs to ensure the reliability of the fixing while avoiding over-constraint. The total length of the straight slot hole consists of two parts: the diameter d of the bolt 2 plus the required thermal expansion displacement L (i.e., L in the subsequent formula). The function of this straight slot hole is to provide guidance and space for the thermal expansion of the sector-shaped thermal insulation unit 121.

[0120] Bolt 2 passes through a straight slot to fix the sector-shaped heat insulation unit 121 to the frame 3, but bolt 2 is not tightened completely; a suitable gap is left to allow the straight slot to slide relative to bolt 2. The tightening torque of bolt 2 is usually between 3 N·m and 5 N·m, which ensures fixation without generating excessive friction that hinders sliding. A gasket, such as a molybdenum gasket or a graphite gasket, can also be placed between bolt 2 and the heat insulation plate 1 to distribute pressure evenly and prevent seizing.

[0121] The working state of the straight slot hole is configured as follows:

[0122] When the sector-shaped heat insulation unit 121 is at room temperature, the bolt 2 is located at the end of the straight slot hole away from the center of the sector-shaped heat insulation unit 121. At this time, the entire unit is at the innermost side of its radial travel.

[0123] When the sector-shaped heat insulation unit 121 is at its operating temperature, the unit expands due to heat, increasing its size. Since the bolt 2 is fixed to the frame 3, the thermal expansion of the unit drives the sector-shaped heat insulation unit 121 to move outward relative to the bolt 2, eventually positioning the bolt 2 at one end of the straight slot near the center of the sector-shaped heat insulation unit 121. This design ensures that the sector-shaped heat insulation unit 121 always has sufficient displacement space throughout the entire thermal expansion process, preventing internal stress from being generated due to the constraint of the fixing point or causing the bolt 2 to shear off. The effectiveness of this structure can be verified through comparative experiments: two sector-shaped units made of the same material, one fixed with the straight slot of this invention and the other fixed with a regular round hole, were heated to 1000°C simultaneously. It was found that the unit fixed with the round hole exhibited significant warping deformation, while the unit fixed with the straight slot remained flat, and the bolt did not loosen.

[0124] For details on fixing the central insulation sub-panel 11, please refer to [link / reference]. Figure 5 , Figure 6 and Figure 7Its installation method is similar to that of the fan-shaped heat insulation unit 121, but slightly different. A first positioning hole 111 is provided at the center of the central heat insulation sub-plate 11. The first positioning hole 111 is a circular hole, and its function is to determine the precise position of the central heat insulation sub-plate 11, serving as the assembly reference for the entire heat insulation screen 1. On the outer periphery of the central heat insulation sub-plate 11, a plurality of first straight slots 112 are provided circumferentially. In this embodiment, there are 3 first straight slots 112, which are evenly distributed on the outer edge of the central heat insulation sub-plate 11. The even distribution can ensure that the central heat insulation sub-plate 11 is subjected to balanced forces and remains concentric during thermal expansion. The function of the first straight slots 112 is to guide the movement of the central heat insulation sub-plate 11 when it expands radially due to heat. Both the first positioning hole 111 and the first straight slots 112 are engaged with bolts 2 to assemble the central heat insulation sub-plate 11 onto the frame 3. The bolt 2 passing through the first positioning hole 111 fixes the center point of the central heat insulation sub-plate 11 as the base point for thermal expansion; while the bolt 2 passing through the first straight slot hole 112 allows the outer edge of the central heat insulation sub-plate 11 to expand outward, and the length direction of the straight slot hole is radial, providing guidance for the expansion.

[0125] The design length of the first straight slot 112 is crucial. The center distance L between its two arcs (i.e., the effective guiding length of the straight slot) satisfies the following formula:

[0126] ,

[0127] In the formula:

[0128] α is the linear expansion coefficient of the material of the sector-shaped heat insulation unit 121, which is consistent with α in the aforementioned formula, with the unit being 1 / ℃.

[0129] ΔT represents the temperature rise at the geometric center of the first straight slot 112, i.e., the temperature rise at the outer edge of the central insulation sub-plate 11, in °C. This value can be obtained through simulation or actual measurement.

[0130] r is the distance, in mm, from the center of bolt 2 that mates with the first straight slot 112 to the center of bolt 2 that mates with the first positioning hole 111. This distance is the thermal expansion reference length of the central heat insulation subplate 11 in this radial direction.

[0131] C is a safety margin, and its value ranges from 0.01 to 0.03 times the radius of the bolt 2 that mates with the first straight slot 112, in mm. The purpose of the safety margin C is to ensure that even if there is a slight deviation in the calculation of thermal expansion, or other minor deformations (such as slight warping of the plate surface or slight displacement of the bolt), the bolt 2 will not move to the extreme position of the straight slot and become stuck, thus ensuring absolutely smooth movement. For example, if the radius of the bolt 2 is 5 mm, then the value of C ranges from 0.05 mm to 0.15 mm. In this embodiment, a preferred value of C is 0.02 times the bolt radius, i.e., 0.1 mm. Comparative experiments demonstrate that setting a safety margin C can effectively reduce the risk of jamming caused by errors in the calculation of thermal expansion, and improve the reliability of long-term operation.

[0132] For each sector-shaped insulation unit 121 of the annular insulation sub-panel 12, the hole design is more refined; please refer to [link / reference needed]. Figure 10 , Figure 11 and Figure 12 Each sector-shaped heat insulation unit 121 has a second positioning hole 1212 near its inner edge, and there is only one such hole. This second positioning hole 1212 is circular, with its center located on the axis of symmetry of the sector-shaped heat insulation unit 121. The function of the second positioning hole 1212 is to serve as a positioning reference for the sector-shaped heat insulation unit 121 on the annular heat insulation sub-plate 12. It cooperates with the bolt 2 passing through it to determine the initial circumferential and radial position of the unit relative to the center of the ring. To ensure the stability and strength of the positioning, the distance from the center of the second positioning hole 1212 to the inner edge of the sector-shaped heat insulation unit 121 is designed to be 1.5 to 2.5 times the radius of the second positioning hole 1212. For example, if the radius of the second positioning hole 1212 is 3 mm, then the distance from its center to the inner edge should be 4.5 mm to 7.5 mm. This distance ensures sufficient material strength around the hole to prevent tearing under heat or stress, while also preventing cracking during processing due to its proximity to the edge. If the distance is less than 1.5 times the radius, the hole edge strength is insufficient; if it is greater than 2.5 times the radius, it occupies unnecessary radial space, affecting the effective size of the element. The preferred value for this distance is 2.0 times the radius.

[0133] An even number of second straight slots 1213, such as 2, 4, or 6, are provided near the outer edge of the fan-shaped heat insulation unit 121. The positions and shapes of these even-numbered second straight slots 1213 are mirror-symmetrical about the axis of symmetry of the fan-shaped heat insulation unit 121. This symmetrical design ensures that the constraint and guidance on both sides of the fan-shaped heat insulation unit 121 are balanced when it expands due to heat, so that it can expand smoothly along its axis of symmetry without deflection or warping. If an odd number of holes is used, symmetrical constraint cannot be formed, which may easily cause the unit to rotate under heat. In this embodiment, for units with a large central angle (e.g., above 60°), four second straight slots 1213 can be provided, symmetrically distributed on both sides of the axis of symmetry; for units with a small central angle, two are sufficient.

[0134] The second straight slot 1213 is a straight slot, and the angle θ between its length direction and the axis of symmetry of the fan-shaped heat insulation unit 121 is calculated according to the following formula:

[0135] ,

[0136] In the formula:

[0137] This is the distance from the center of the second positioning hole 1212 to the center of the ring, in mm. This is a fixed reference distance.

[0138] The distance from the center of the second straight slot hole 1213 to the center of the ring is in mm.

[0139] β is the azimuth angle of the center of the second straight slot 1213 relative to the axis of symmetry, in radians. Since the shape of the fan-shaped heat insulation unit 121 is regular, each point on it has its coordinates relative to the axis of symmetry, and β is the polar angle describing the position of that point.

[0140] A straight slotted hole cut at this angle θ allows for thermal expansion displacement at that point without generating additional constraint forces. Finite element simulations verify that, when simulating thermal expansion, the interference pressure between the bolt and the hole wall is less than 0.1 MPa for a straight slotted hole designed according to this formula, while a straight slotted hole in any direction will generate significant lateral forces.

[0141] Furthermore, this design method further includes the following steps:

[0142] S300: A second labyrinth structure 1214 is provided at the radial junctions between the central heat insulation sub-plate 11 and each layer of annular heat insulation sub-plates 12, and between adjacent layers of annular heat insulation sub-plates 12, to compensate for radial displacement caused by thermal expansion. Similar to the first labyrinth structure 1211, the second labyrinth structure 1214 is also a concave-convex mating structure directly machined on the radial junction surfaces of adjacent plates, and its function is also to prevent heat radiation from penetrating through radial gaps. The machining method can be milling or grinding, machining annular grooves on the outer edge of the central heat insulation sub-plate 11 or the inner edge of the annular heat insulation sub-plate 12, and machining annular bosses on the mating plates to form a tortuous sealing path. The depth and width of the grooves and bosses can be designed with reference to the circumferential labyrinth structure.

[0143] For any pair of radially adjacent annular heat insulation sub-plates 12, the layer closer to the center is defined as the inner annular heat insulation sub-plate 12, and the layer farther from the center is defined as the outer annular heat insulation sub-plate 12. The second gap of the second labyrinth structure 1214 under normal temperature assembly is calculated by the following formula:

[0144] ,

[0145] In this formula:

[0146] α is the coefficient of linear expansion of the insulation board material 1, in units of 1 / ℃.

[0147] The temperature rise at the outer edge of the inner annular heat insulation sub-plate 12 is expressed in °C.

[0148] The outer radius of the inner annular heat insulation sub-plate 12 is in mm.

[0149] The temperature rise at the inner edge of the outer annular heat insulation sub-plate 12 is expressed in °C.

[0150] The distance from the center of the second positioning hole 1212 on the outer annular heat insulation subplate 12 to the center of the ring is measured in mm.

[0151] D is the safety margin, and its value range can be referenced from the safety margin of the first straight slot 112, for example, 0.1mm to 0.5mm.

[0152] The principle behind this formula is based on the relative thermal expansion of the inner and outer plates in the radial direction. The outer edge of the inner plate expands outwards, and the inner edge of the outer plate also expands outwards, but the amount of expansion differs due to their different initial positions and temperature rises. For example, if the outer edge of the inner plate expands by 1.0 mm and the inner edge of the outer plate expands by 1.5 mm, both in the outward direction, then the relative displacement between them is 0.5 mm. Therefore, a second gap of at least 0.5 mm (plus a safety margin) needs to be reserved. This formula, through mechanistic analysis, accurately describes the coupling relationship of radial thermal expansion, providing a theoretical basis for the design of the second gap.

[0153] Based on the same inventive concept, this invention also provides a fish-scale-patterned spliced ​​heat-insulating reflective screen. This heat-insulating reflective screen is a specific product manufactured according to the above-described design method. Figures 3 to 12 As shown, it comprises multiple layers of insulation panels 1, which are stacked in a staggered manner along their thickness and mounted to a frame 3 by bolts 2. The staggered stacking means that the circumferential gaps between adjacent fan-shaped insulation units 121 do not coincide in the vertical direction, but are offset from each other. The staggered angle γ of this stacking method is designed to be half the central angle of the fan-shaped insulation unit 121. For example, if the central angle of the fan-shaped insulation unit 121 is 40°, then the staggered angle γ is 20°. This staggered structure allows heat radiation to pass through one layer of gaps and then be blocked by the continuous surface of the next layer, preventing it from penetrating the entire insulation screen in a straight line. Instead, it must undergo multiple reflections, thus greatly improving the overall insulation efficiency. Through comparative experiments, the temperature on the back of the heat insulation screen was measured under the same heat source conditions. It was found that the temperature on the back of the heat insulation screen with staggered stacking was significantly lower than that with non-staggered stacking. Compared with the straight-through gap structure without staggered stacking, the staggered structure of the present invention can reduce the heat radiation heat flux density through the heat insulation screen by about 40% to 60%.

[0154] In summary, the structural features of this fish-scale spliced ​​heat-insulating reflective screen are as follows: the heat insulation panel 1 consists of a central heat insulation sub-panel 11 and an annular heat insulation sub-panel 12; the annular heat insulation sub-panel 12 is formed by splicing multiple fan-shaped heat insulation units 121 circumferentially; a first labyrinth structure 1211 is formed between adjacent fan-shaped heat insulation units 121, which has a first gap calculated according to the aforementioned method under normal temperature assembly; a second labyrinth structure 1214 is formed at the radial adjacency between the central heat insulation sub-panel 11 and each layer of annular heat insulation sub-panel 12, which also has a second gap calculated according to the aforementioned method under normal temperature assembly. The connections between all components adopt a sliding fit between bolts 2 and straight slot holes, providing precise guidance for thermal expansion. The staggered stacking of multiple layers further enhances the heat radiation protection capability.

[0155] The fish-scale spliced ​​heat-insulating reflector and its design method of this invention achieve precise compensation for non-uniform thermal expansion by designing the first gap as a radially varying wedge shape and supplementing it with precise calculation formulas. Simultaneously, the circumferential and second labyrinthine structures ensure the freedom of thermal expansion while effectively blocking heat radiation leakage. The sliding fit between the straight slot holes and bolts provides precise guidance and space for the radial expansion of the fan-shaped units and the central plate. The staggered stacking of multiple layers further enhances the overall heat radiation protection capability. Overall, this invention addresses both thermal expansion compensation and heat radiation protection structure, providing a structurally stable and heat-insulating reflector solution for vacuum furnaces. This structure can be applied to various types of vacuum furnaces, including vacuum heat treatment furnaces, vacuum brazing furnaces, and vacuum sintering furnaces, and can play a positive role in extending equipment life, reducing energy consumption, and improving furnace temperature uniformity under high-temperature conditions.

[0156] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A fish-scale-patterned spliced ​​heat-insulating reflective screen, characterized in that, It includes at least one layer of heat insulation board (1), which is installed on the frame (3) by bolts (2); the heat insulation board (1) includes: The central insulation panel (11) is circular and located in the center; At least one annular heat insulation sub-panel (12) is radially distributed on the outside of the central heat insulation sub-panel (11); the annular heat insulation sub-panel (12) is formed by splicing together multiple fan-shaped heat insulation units (121) circumferentially; in, A first gap is provided between adjacent fan-shaped heat insulation units (121); the projection of the first gap on a plane parallel to the heat insulation plate (1) is a wedge shape that is smaller at the inner diameter and larger at the outer diameter, which varies radially to compensate for circumferential displacement caused by thermal expansion.

2. The fish-scale spliced ​​heat-insulating reflective screen according to claim 1, characterized in that, The first gap has a radial distribution characteristic called Gap(r), and its value is calculated according to the following formula: ， In the formula: Gap(r) represents the value of the first gap at different radial positions, in mm; r is the radius of a point on the sector-shaped heat insulation unit (121) from the center of the circle, in mm; α is the coefficient of linear expansion of the material of the fan-shaped heat insulation unit (121), in units of 1 / ℃; ΔT(r) is the temperature rise at a distance r from the center of the circle, in °C. φ is the central angle of the sector-shaped heat insulation unit (121), in radians; k is the safety factor, which has no unit.

3. The fish-scale spliced ​​heat-insulating reflective screen according to claim 2, characterized in that, A first labyrinth structure (1211) extending radially is provided at the assembly surface of the adjacent fan-shaped heat insulation unit (121); the assembly gap of the first labyrinth structure (1211) at room temperature is the first gap.

4. The fish-scale spliced ​​heat-insulating reflective screen according to claim 2, characterized in that, The safety factor k ranges from 1.015 to 1.

035.

5. The fish-scale spliced ​​heat-insulating reflective screen according to claim 1, characterized in that, A second labyrinth structure (1214) extending circumferentially is provided at the assembly surface between the central heat insulation sub-plate (11) and the adjacent annular heat insulation sub-plate (12), as well as between two adjacent annular heat insulation sub-plates (12). The fitting gap of the second labyrinth structure (1214) at room temperature is the second gap, which is used to compensate for radial displacement caused by thermal expansion.

6. The fish-scale spliced ​​heat-insulating reflective screen according to claim 5, characterized in that, The central heat insulation sub-plate (11) has a first positioning hole (111) at its center; the central heat insulation sub-plate (11) has a plurality of first straight slot holes (112) on its outer periphery; the first straight slot holes (112) are radial in length and are used to guide the central heat insulation sub-plate (11) to move when it expands radially when heated; the first positioning hole (111) and the first straight slot holes (112) are both engaged with the bolts (2) to assemble the central heat insulation sub-plate (11) onto the frame (3); The center distance L between the two arcs of the first straight slot hole (112) satisfies the following formula: ， In the formula: α is the coefficient of linear expansion of the material of the sector-shaped heat insulation unit, in units of 1 / ℃; ΔT is the temperature rise at the geometric center of the first straight slot hole (112), in °C; r is the distance from the center of the bolt (2) that mates with the first straight slot (112) to the center of the bolt (2) that mates with the first positioning hole (111), in mm; C is a safety margin, and the value of C is 0.01 to 0.03 times the radius of the bolt (2) that mates with the first straight slot hole (112), in mm.

7. The fish-scale spliced ​​heat-insulating reflective screen according to claim 5, characterized in that, Each of the fan-shaped heat insulation units (121) has at least one second straight slot hole (1213) that slides with the bolt (2); The second straight slot (1213) is configured such that when the fan-shaped heat insulation unit (121) is at room temperature, the bolt (2) is located at one end of the second straight slot (1213) away from the center of the fan-shaped heat insulation unit (121); When the fan-shaped heat insulation unit (121) is at the working temperature, the second straight slot (1213) moves relative to the bolt (2) due to thermal expansion, and the bolt (2) is located at one end of the second straight slot (1213) near the center of the fan-shaped heat insulation unit (121).

8. The fish-scale spliced ​​heat-insulating reflective screen according to claim 7, characterized in that: The fan-shaped heat insulation unit (121) has one and only one second positioning hole (1212) near its inner edge; the center of the second positioning hole (1212) is located on the axis of symmetry of the fan-shaped heat insulation unit (121); the distance from the center of the second positioning hole (1212) to the inner edge of the fan-shaped heat insulation unit (121) is 1.5 to 2.5 times the radius of the second positioning hole (1212); An even number of second straight slots (1213) are provided near the outer edge of the fan-shaped heat insulation unit (121), and the position and shape of the even number of second straight slots (1213) are symmetrical about the axis of symmetry of the fan-shaped heat insulation unit (121). Wherein, the second straight slot (1213) is a straight slot, and the angle θ between its length direction and the axis of symmetry of the fan-shaped heat insulation unit (121) is calculated according to the following formula: ， In the formula: The distance from the center of the second positioning hole (1212) to the center of the ring is in mm; The distance from the center of the second straight slot (1213) to the center of the ring, in mm; The azimuth angle of the center of the second straight slot (1213) relative to the axis of symmetry is expressed in radians.

9. The fish-scale spliced ​​heat-insulating reflective screen according to claim 7, characterized in that, For any pair of radially adjacent annular heat insulation sub-plates (12), the inner annular heat insulation sub-plate (12) is defined as the layer closest to the center; the outer annular heat insulation sub-plate (12) is defined as the layer furthest from the center; the value of each second gap, Gap (rad), is calculated according to the following formula: ， In the formula: α is the coefficient of linear expansion of the insulation material, in units of 1 / ℃; Temperature rise at the outer edge of the inner annular heat insulation sub-plate (12), unit: °C; The outer radius of the inner annular heat insulation sub-plate (12) is in mm; Temperature rise at the inner edge of the outer annular heat insulation sub-plate (12), unit: ℃; The distance from the center of the second positioning hole (1212) on the outer annular heat insulation subplate (12) to the center of the ring, in mm; D is the safety margin, which ranges from 0.1 mm to 0.5 mm.

10. A method for designing a heat-insulating reflective screen, characterized in that, Includes the following steps: S110: Obtain the linear expansion coefficient α, central angle φ, and radial temperature rise ΔT(r) of the fan-shaped heat insulation unit (121); and calculate the radial distribution characteristic Gap(r) of the first gap between adjacent fan-shaped heat insulation units (121) at room temperature, the value of which is calculated by the following formula: ， In the formula: Gap(r) represents the value of the first gap at different radial positions, in mm; r is the radius of a point on the sector-shaped heat insulation unit (121) from the center of the circle, in mm; α is the coefficient of linear expansion of the material of the fan-shaped heat insulation unit (121), in units of 1 / ℃; ΔT(r) is the temperature rise at a distance r from the center of the circle, in °C. φ is the central angle of the sector-shaped heat insulation unit (121), in radians; k is the safety factor, which has no unit. S120: The adjacent sides of the adjacent fan-shaped heat insulation units (121) are processed into a structure with a preset included angle, so that a first gap with a radially varying wedge shape and a distribution characteristic of Gap(r) is formed between them at room temperature.

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