Plate structure of plate heat exchanger

Abstract

The utility model discloses a plate structure of a plate heat exchanger, which comprises a plurality of single-layer plates A and sandwich plates B. The plates A and B are respectively provided with a plurality of rows of trilobal projections and recesses perpendicular to the trend of a medium, and the layout of the trilobal projections is that one plate A is arranged at each central angle inside a regular hexagon E, and the other plate A is arranged at each central angle inside the regular hexagon E; the plates B are respectively arranged at the vertex angle and the central point of the regular hexagon E; if the protrusions or the recesses on the plate A are the protrusions in the first row and the recesses in the second row, the protrusions or the recesses on the plate B are the recesses in the first row and the protrusions in the second row, and so on; the plates A and the plates B are arranged in a staggered manner and are mutually embedded; and the convex tops or the concave bottoms of the plurality of plates A and B are in contact with the adjacent plate surfaces. By changing the concave-convex shape and the number of the plate surfaces, the convex and concave surfaces on the plate A and the plate B are circular arcs or cones, so that the contact area between the plate sheets is increased, and the plate heat exchanger with the plate sheet structure is large in heat transfer flux, small in pressure loss per unit length and higher in heat transfer efficiency.

Description

Technical Field

[0001] The utility model belongs to a plate type heat exchanger component, in particular to a plate structure of a plate type heat exchanger. Background Art

[0002] Plate heat exchangers have been widely used in metallurgy, mining, petroleum, chemical industry, electricity, medicine, food, chemical fiber, papermaking, textile, shipbuilding, heating and other departments. They can be used for heating, cooling, evaporation, condensation, sterilization, waste heat recovery and other situations. The development and production of the chemical industry are inseparable from the continuous development and progress of heat exchangers, among which plate heat exchangers play a vital role, especially when the temperature difference between cold and hot streams is small, the pressure loss is large, the floor space is small, and the heat transfer coefficient is low. The form and structure of plate heat exchangers are also the focus of research.

[0003] At present, the plate forms of plate heat exchangers mainly include herringbone corrugated plates, horizontal straight corrugated plates and tumor-shaped plates.

[0004] Although the herringbone corrugated plate has high heat transfer efficiency, strong pressure bearing capacity and low fouling coefficient, the flow channel cross-section of the herringbone plate is complex, and the flow of the fluid in the flow channel (such as repeated expansion and contraction) will consume more energy, resulting in increased fluid resistance. The working pressure is usually below 2.5MPa and the working temperature is less than 250°C, which limits its application in some high-pressure and high-temperature scenarios. The flow channel is narrow, usually 3 to 5mm, and it is not suitable for processing media containing large solid particles because these particles can easily cause channel blockage. Therefore, it has defects such as large fluid resistance, working pressure and temperature limitations, and high requirements for the medium.

[0005] Although the horizontal straight corrugated plate has high heat transfer efficiency, uniform fluid distribution, compact structure, and easy cleaning and maintenance, the flow channel is relatively narrow. If there are large solid particles or impurities in the fluid, it is easy to cause blockage of the flow channel, affecting the heat transfer effect. When the fluid flows between the corrugated plates, it will be subject to more friction and resistance, resulting in a large pressure loss, which increases energy consumption and operating costs to a certain extent. In some special environments, such as high temperature or high pressure medium conditions, there are defects such as strict requirements on the fluid and large pressure loss.

[0006] Although the nodular plate has high heat transfer efficiency, good self-cleaning ability, and high structural strength, the manufacturing process is relatively complex and requires precise molds and process control, so the manufacturing cost is relatively high. This also makes the price of nodular plates generally higher in the market, the flow channel structure is relatively complex, and there are high requirements for the cleanliness and particle content of the fluid. Although the nodular plate has a certain self-cleaning ability, it still needs to be cleaned and maintained regularly during long-term operation. Due to its structural characteristics, the difficulty of cleaning and maintenance is relatively large, and professional technology and equipment support are required. Therefore, there are defects such as high manufacturing difficulty, high requirements for fluids, and difficult cleaning and maintenance. Utility Model Content

[0007] In view of the above-mentioned prior art, the utility model provides a plate structure of a plate type heat exchanger. The utility model has a large heat transfer flux and increases the contact point area between the plates by changing the concave and convex shapes and the number of the plate surfaces, and whether the convex top surfaces and the concave bottom surfaces on the A plate and the B plate are arc surfaces or conical surfaces. The plate type heat exchanger using the plate structure of the utility model has a large heat transfer flux and a small pressure loss per unit length, thereby making the heat transfer efficiency higher.

[0008] In order to solve the above technical problems, the utility model proposes a plate structure of a plate heat exchanger, including multiple A plates and B plates, wherein the A plates are single-layer plates, and the B plates are sandwich plates, wherein the A plates and the B plates are provided with multiple rows of protrusions and depressions perpendicular to the direction of the medium, and the intersection profiles of the protrusions and depressions with the plate surface are all the same three-leaf type, and the top surface of the protrusion and the bottom surface of the depression are arc surfaces or conical surfaces, and the position of the vertex of the arc surface or the conical surface coincides with the projection position of the central symmetric point of the three-leaf profile;

[0009] The layout of the trefoil profile on the A plate is arranged according to one at each central angle inside a regular hexagon E; the method for determining whether the trefoil profile on the A plate corresponds to a convexity or a concaveity is: the first row is convex, the second row is concave, and so on; the layout of the trefoil profile on the B plate is arranged according to one at each vertex angle and central point of a regular hexagon E; the method for determining whether the trefoil profile on the B plate corresponds to a convexity or a concaveity is: the first row is concave, the second row is convex, and so on;

[0010] On the A plate and the B plate, a plurality of regular hexagons E are formed in two adjacent rows of three-leaf profiles, and the edge-center distance of the regular hexagon E is d; multiple A plates and B plates are arranged alternately and inlaid with each other; among the multiple A plates and B plates, the raised tops or the recessed bottoms are in contact with the adjacent plate surfaces.

[0011] Furthermore, the plate structure of the plate heat exchanger of the utility model, wherein:

[0012] After multiple A plates and B plates are arranged alternately and inlaid with each other, when the medium passes through, a medium flow is formed between the top of the protrusion and the contact point of the adjacent plate surface and between the bottom of the depression and the contact point of the adjacent plate surface; a medium turbulence is formed at the front face of the protrusion; thereby improving the self-cleaning ability of the plate.

[0013] In the utility model, the heights of the protrusions and depressions on the A plate and the B plate and the geometrical dimensions of the three-leaf shape are determined according to the viscosity of the medium, the flow velocity of the medium and the impurity content.

[0014] In the utility model, whether the convex top surface and the concave bottom surface on the A plate and the B plate are arc surfaces or conical surfaces is determined according to the calculated area of ​​the heat exchanger.

[0015] In the utility model, the heat transfer needs of the heat exchanger are met by changing the heat transfer area by designing the number of plates of the A plate and the B plate, the number of protrusions and depressions on the A plate and the B plate, and whether the top surfaces of the protrusions and the bottom surfaces of the depressions on the A plate and the B plate are arc surfaces or conical surfaces.

[0016] Compared with the prior art, the beneficial effects of the utility model are:

[0017] (1) The utility model increases the contact point area between the plates by changing the concave-convex shape (three-leaf shape) of the plate surface. Compared with the commonly used herringbone plate heat exchanger, the contact point area is increased by about 10%, thereby achieving a large heat transfer flux; by changing the combination of the A and B plates, the fluid channel formed between the plates is changed, thereby increasing the heat exchange area.

[0018] (2) When using a plate heat exchanger with the plate structure of the utility model, the plate adopts a concave-convex shape (three-leaf shape) to change the direction of the original herringbone and horizontal straight plate fluid channel, and adjust it to a rounded along-line direction, avoiding the resistance of traditional right angles, obtuse angles and acute angles, so that the fluid flows around and collides, the local turbulence is enhanced, the pressure loss is reduced, the fluid flow channel is smoother and rounder, and the fluid pressure loss is reduced by about 10%, which changes the disadvantage of large pressure loss per unit length of traditional plate heat exchangers.

[0019] (3) By changing the size of the three-leaf shape, the width of the flow channel of the A and B plates can be changed to suit different media. The A plate in the utility model is a single-layer plate, and the three-leaf shape is arranged in a regular hexagonal shape; the B plate is a sandwich plate, and the three-leaf shape is arranged in a regular triangle shape. The A and B plates are inlaid with each other, and the contact area is increased by using different shapes of the top or bottom of the concave and convex three-leaf shape. For example, the top and bottom can be arc-shaped or vertex-shaped, such as Fig.10 and Fig.11 As shown, the contact area between the plates is increased, making the heat transfer efficiency higher.

[0020] (4) The eddy current and turbulence of the medium formed by the unique fluid channel give the plate excellent self-cleaning ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the A plate inlay surface in the utility model;

[0022] Figure 2 It is a structural schematic diagram of the B plate inlay surface in the utility model;

[0023] Figure 3 yes Figure 1 The enlarged schematic diagram of the local structure of the inlaid surface of plate A is shown;

[0024] Figure 4 yes Figure 2 The enlarged schematic diagram of the local structure of the inlaid surface of plate B is shown;

[0025] Figure 5 Yes Figure 1 A and Figure 2 The schematic diagram of the medium flow formed after the B plate is inlaid is shown, wherein a1 and a2 show the turbulent flow of the medium, and b1 and b2 show the bypass flow of the medium;

[0026] Figure 6 It is the cross-section of plate A;

[0027] Figure 7 It is the cross-section of plate B;

[0028] Figure 8 It is a cross-sectional schematic diagram after the A plate and the B plate are inlaid;

[0029] Fig. 9 It is a schematic diagram of the shape of the inlay contact point between the A plate and the B plate;

[0030] Fig.10 It is a schematic diagram of the arc-shaped contact between plate A and plate B;

[0031] Fig.11 It is a schematic diagram of the contact form of the top angle shape of plate A and plate B;

[0032] Fig.12 It is a schematic diagram of a plate heat exchanger using the plate of the utility model;

[0033] Figure 13-1 This is a schematic diagram of the structure of plate A in the embodiment;

[0034] Figure 13-2 Schematic diagram of the structure of plate B in the embodiment;

[0035] Figure 13-3 Schematic diagram of the trifoliate profile of the A plate and the B plate in the embodiment.

[0036] In the figure:

[0037] 1- Flange 2- Fixing clamp 3- Corner hole bushing 4- Foot

[0038] 5-pillar 6-movable splint 7-lower guide rod 8-nut

[0039] 9-bolt 10-upper guide rod 11-rubber pad 12-plate. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the following embodiments are by no means intended to limit the present invention in any way.

[0041] The utility model provides a plate structure of a plate heat exchanger, comprising a plurality of A plates and B plates, wherein the A plates are single-layer plates, and the B plates are sandwich plates, and the A plates and the B plates are provided with a plurality of rows of protrusions and depressions perpendicular to the direction of the medium. Figure 1 The A-board structure is shown. Figure 2 The B-board surface structure is shown.

[0042] The intersection profiles of the protrusions and the depressions with the plate surface are all the same three-leaf shape. The layout of the three-leaf shape profile on the A plate is arranged according to the arrangement of one at each central angle inside a regular hexagon E, such as Figure 3 As shown, Figure 6 The cross section of the A plate is shown; the method of determining whether the A plate corresponds to the three-leaf profile is as follows: the first row is convex, the second row is concave, and so on.

[0043] The layout of the three-leaf profile on the B plate is to arrange one at the vertex and the center point of a regular hexagon E, such as Figure 4 As shown, Figure 7 The cross section of plate A is shown; the method for determining whether the three-leaf profile on plate B corresponds to a convexity or a concaveity is as follows: the first row is a concave, the second row is a convexity, and so on. On plates A and B, two adjacent rows of three-leaf profiles form a plurality of regular hexagons E, and the apicocenter distance of the regular hexagons E is d, as shown in FIG. Figure 5 and Fig. 9 shown.

[0044] Multiple A plates and B plates are arranged alternately and inlaid with each other. Figure 8 The schematic diagram of the A and B plates after inlay is shown. Among the multiple A plates and B plates, the top of the protrusion or the bottom of the depression contacts the adjacent plate surface. The top surface of the protrusion and the bottom surface of the depression are arc surfaces or conical surfaces, thereby increasing the contact point area between the plates. Fig.10 The arc surface bulge on plate A is shown. Fig.11The conical surface protrusion on the B plate is shown. In the present invention, the top surface of the protrusion and the bottom surface of the depression on the A plate and the B plate are determined to be arc surface or conical surface according to the calculated area of ​​the heat exchanger, and the contact point area is controlled by the contact point shape, thereby increasing the contact point area. The position of the vertex of the arc surface or the conical surface coincides with the projection position of the central symmetric point of the three-leaf profile, such as Fig. 9 As shown in the figure, the area where the small circle is located is the contact point of the A and B plates. The contact point area can be controlled by adjusting the size of the three-leaf shape. The contact area of ​​this structure is 10% higher than that of the ordinary herringbone plate. In the utility model, the height of the protrusions and depressions on the A and B plates and the geometric size of the three-leaf shape can be determined according to the viscosity of the medium, the flow rate of the medium, and the impurity content.

[0045] In the utility model, after multiple A plates and B plates are arranged in a staggered manner and inlaid with each other, when the medium passes through, the medium flows around between the top of the protrusion and the contact point of the adjacent plate surface and between the bottom of the depression and the contact point of the adjacent plate surface; and the medium turbulence is formed at the front of the protrusion. Figure 5 As shown, b1 and b2 show the flow around the medium, which enhances the flow around the concave and convex points on the plate; a1 and a2 show the turbulence of the medium. Such a structure causes the flow to collide and enhances the local turbulence. The frequent changes in the flow direction and flow velocity of the fluid greatly increase the disturbance of the fluid, making it difficult for dirt to accumulate, thereby improving the self-cleaning ability of the plate. Therefore, the plate structure of the utility model has a very good self-cleaning ability.

[0046] At the same time, the vortex and turbulence make the flow of the fluid inside the heat exchanger more complicated. The frequent changes in the flow direction and flow velocity of the fluid greatly increase the disturbance of the fluid, making the heat exchange between the heat transfer surface and the fluid more sufficient. This helps to reduce the heat transfer thermal resistance, thereby improving the heat transfer efficiency. The utility model can effectively prevent the occurrence of heat transfer dead zones by optimizing the plate structure to increase vortex and turbulence. The heat transfer dead zone is an area inside the heat exchanger where the fluid flows poorly and the heat transfer effect is poor, while vortex and turbulence can make the fluid evenly distributed inside the heat exchanger, improving the heat transfer effect inside the entire heat exchanger.

[0047] Due to the existence of vortex and turbulence, plate heat exchangers can adapt to fluids of different viscosities, and even maintain good heat transfer performance for high-viscosity fluids. In addition, by adjusting the structure, number, number of bumps and contact point shapes of the plates, the heat transfer area can be easily changed to meet different heat transfer requirements. Although vortex and turbulence will increase the complexity of fluid flow, a reasonable plate structure design can reduce the pressure loss of the fluid inside the heat exchanger while ensuring heat transfer efficiency, thereby reducing operating costs.

[0048] Fig.12The plate heat exchanger using the plate structure of the utility model is shown, and the plate heat exchanger includes a plate bundle, and the plate bundle includes a fixed clamping plate 2, a movable clamping plate 6 and a series of clamping plates and plates. The clamping plates clamp the plates and form a sealed heat exchange area. The fixed clamping plate 2, the movable clamping plate 6 and the clamping plate are usually made of carbon steel plates or stainless steel plates, and their thickness is determined according to the pressure that the heat exchanger needs to withstand. The main function is to clamp all the plates together evenly to ensure the sealed flow of the fluid between the plates. The fixed clamping plate 2 is located on one side of the heat exchanger, and the movable clamping plate 6 can be adjusted when necessary to ensure close contact between the plates. The fixed clamping plate 2 and the movable clamping plate 6 are provided with an upper guide rod 10 and a lower guide rod 7 for supporting and positioning the clamping plate and the plate 12 to ensure that the plate 12 will not move or deform when heated or pressurized. The support 5 mainly supports the weight of the entire heat exchanger, making the entire heat exchanger a stable whole.

[0049] The plate 12 is the core component of the heat exchanger, which is usually made of metal and is provided with a sealing groove and a corner hole. The sealing groove is provided with a rubber pad 11, and the corner hole is provided with a corner hole bushing 3. All the plates 12 are arranged in parallel, and rubber gaskets are provided between the plates 12 to seal the periphery of the plates to prevent fluid leakage. Bolt holes are provided around the fixed clamping plate 2 and the movable clamping plate 6, and the movable clamping plate 6 is pushed to move toward the fixed clamping plate 2 by bolts 9 and nuts 8 to clamp the plates 12. The plates 12 are stacked to form a heat exchange channel, and a fluid channel is formed between adjacent plates 12. The fluid flows between the plates to exchange heat. In order to increase the heat exchange efficiency, the plates 12 in the heat exchanger adopt the plate structure designed in the utility model (as described above, no further description is given here), which is composed of multiple A plates and B plates. The A plate is a single-layer plate, and the B plate is a sandwich plate. Multiple rows of protrusions and depressions are provided on the A plate and the B plate along the direction of the medium. The guide structure formed by the staggered arrangement and mutual inlay of multiple A plates and B plates can guide the fluid to flow along a specific path, increase the turbulence of the fluid flow, and thus improve the heat exchange efficiency.

[0050] Research Materials:

[0051] The herringbone A and B plates commonly used on the market are adjusted to the concave and convex three-leaf structure of the A and B plates designed in the utility model. The A and B plates are arranged alternately and inlaid with each other. The A plate is a single-layer plate, and the three-leaf shape presents an internal arrangement of a regular hexagon; the B plate is a sandwich plate, and the three-leaf shape presents an equilateral triangle angle arrangement. Heat exchange is achieved by contact of the outer edge angles of the concave and convex three-leaf shape. The notable feature of the herringbone plate is its corrugated shape. The corrugations on the plates are inverted and stacked together to form a herringbone structure from top to bottom. The advantages of the improved plate structure are: (1) The plate adopts a concave-convex shape (three-leaf shape) to change the resistance of the right angles, obtuse angles and acute angles of the fluid channel of the original herringbone and horizontal straight plate, and now it is adjusted to a rounded shape, avoiding these resistances and reducing pressure drop; making the fluid flow around and collide, local turbulence is enhanced, and the heat transfer efficiency is improved (the pressure drop of a single unit of a general herringbone plate heat exchanger is about 50Kpa, and the pressure drop of a single unit of the plate heat exchanger studied is about 45kpa, and the pressure drop is reduced by about 10%); (2) The contact point area of ​​the improved plate guide structure is higher than the contact point area of ​​the herringbone plate. According to the influence of other factors such as process medium and single unit size, the heat exchange area of ​​the general improved plate is about 5% of the effective area of ​​the plate, and the heat exchange area of ​​the herringbone plate is about 4.5% of the effective area of ​​the plate, that is, the heat exchange area is increased by about 10%.

[0052] Embodiment: For methanol distillation energy-saving transformation project: annual output of 700,000 tons of methanol, in order to save steam consumption, a new tower is added, the thermal coupling mode is changed to achieve energy saving, and a new tower top condenser is added to save floor space and improve heat transfer efficiency. All modified and changed condensers are replaced with plate heat exchangers adopting the plate structure of the utility model. The specifications and dimensions of the improved plate heat exchanger are about 10% smaller than those of conventional plate heat exchangers, and the plate contact area is about 10% larger than that of conventional plate heat exchangers, thereby reducing the floor space and heat exchange area.

[0053] The design data of the plate structure used in this embodiment are as follows:

[0054] The medium is methanol vapor, the calculated dimensions of plate A and plate B are 1500*600mm (length*width), the calculated heat exchanger area is 1200*600*1500 (length*width*height), and the effective area of ​​plate A and plate B is 1072*540mm. Figure 13-1 and Figure 13-2 As shown, the calculated number of 3-leaf protrusions and depressions of plate A is 672, and the calculated number of 3-leaf protrusions and depressions of plate B is 312. The dimensions of the 3-leaf profile are as follows: Figure 13-3As shown, it can be seen that the three-leaf profile designed in the utility model is evenly distributed in the circumferential direction. The three-leaf profile and the three tangent points of its circumscribed circle are connected in sequence to form an equilateral triangle, that is, the three tangent points are connected through the center point O of the circumscribed circle of the three-leaf profile, and the central angles of two adjacent connecting lines are 120°. The composite heat exchange area of ​​plate A and plate B is 0.00089m 2 In order to determine that the side length of the regular hexagon E of the three-leaf layout is 43.3mm, all the regular hexagons E on the A and B plates are arranged in the same way, the distance between the vertex of the top row of regular hexagons E and the effective area is 4.5mm, and the distance between the vertex of the regular hexagon E on the left and right edges and the edge of the same side plate is 7.5mm. In this embodiment, the diameter of the circumscribed circle of the three-leaf outline is 25mm, the radius of the three-leaf outer arc is 4mm, and the radius of the concave arc tangent to the two adjacent outer arcs is 6mm, such as Figure 13-3 As shown. Usually, the plate size of the plate heat exchanger is calculated to be 1500*600mm (length*width), the overall size is 1350*600*1500mm (length*width*height), and the composite area of ​​the two plates A and B of the heat exchanger is 0.0008m 2 The size of the plate heat exchanger using the plates designed in this embodiment is reduced by about 10% compared with the conventional plate heat exchanger, and the heat exchange area is increased by about 10%.

[0055] In summary, the plate heat exchanger of the utility model has made great adjustments on the plate structure (the conventional herringbone plate structure is adjusted to a concave-convex three-leaf structure), and the concave-convex shape (three-leaf shape) on the plate is used to increase the contact point area between the plates, increase the fluid channel, increase the heat exchange area, and reduce the pressure loss.

[0056] Although the utility model has been described above in conjunction with the accompanying drawings, the utility model is not limited to the above-mentioned specific embodiments, which are merely illustrative rather than restrictive. Under the guidance of the utility model, ordinary technicians in this field can make many improvements and changes without departing from the purpose of the utility model, all of which are within the protection of the utility model.

Claims

1. A plate structure of a plate heat exchanger, comprising a plurality of A plates and B plates, wherein the A plates are single-layer plates, the B plates are sandwich plates, and the A plates and the B plates are provided with a plurality of rows of protrusions and depressions perpendicular to the direction of the medium, characterized in that: The intersection profiles of the protrusion and the depression with the plate surface are all the same trifoliate shape, the top surface of the protrusion and the bottom surface of the depression are arc surfaces or conical surfaces, and the positions of the vertices of the arc surfaces or conical surfaces coincide with the projection positions of the central symmetric points of the trifoliate contours; The layout of the trefoil profile on the A plate is arranged in accordance with the arrangement of one at each central angle inside a regular hexagon E; the method of determining whether the trefoil profile on the A plate corresponds to a convexity or a concaveity is: the first row is convex, the second row is concave, and so on; The layout of the trefoil profile on the B plate is arranged in accordance with the arrangement of one at the vertex and the center point of a regular hexagon E respectively; the method of determining whether the trefoil profile on the B plate corresponds to a convexity or a concaveity is: the first row is a concave, the second row is a convexity, and so on; On the A plate and the B plate, a plurality of regular hexagons E are formed in two adjacent rows of three-leaf profiles, and the edge-center distance of the regular hexagons E is d; Multiple A plates and B plates are arranged alternately and inlaid with each other; among the multiple A plates and B plates, the convex tops or concave bottoms are in contact with adjacent plate surfaces.

2. The plate structure of the plate heat exchanger according to claim 1, characterized in that: After multiple A plates and B plates are arranged in an interlaced manner and inlaid with each other, when the medium passes through, a flow of the medium is formed between the top of the protrusion and the contact point of the adjacent plate surface and between the bottom of the depression and the contact point of the adjacent plate surface; a turbulent flow of the medium is formed at the front of the protrusion; Thereby improving the self-cleaning ability of the plate.

3. The plate structure of the plate heat exchanger according to claim 1, characterized in that: The heights of the protrusions and depressions on the A plate and the B plate and the geometrical dimensions of the three-leaf shape are determined according to the viscosity of the medium, the flow rate of the medium and the impurity content of the medium.

4. The plate structure of the plate heat exchanger according to claim 1, characterized in that: According to the calculated area of ​​the heat exchanger, it is determined whether the convex top surface and the concave bottom surface on the A plate and the B plate are arc surfaces or conical surfaces.

5. The plate structure of the plate heat exchanger according to claim 1, characterized in that: The heat transfer needs of the heat exchanger can be met by changing the heat transfer area by designing the number of plates of the A plate and the B plate, the number of protrusions and depressions on the A plate and the B plate, and whether the top surface of the protrusions and the bottom surface of the depressions on the A plate and the B plate are arc surfaces or conical surfaces.

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