PCHE core body based on gradually-shrinking and gradually-expanding channel and preparation method of PCHE core body

Abstract

The invention provides a PCHE core based on gradually-shrunk and gradually-expanded channels and a preparation method of the PCHE core, and belongs to the technical field of heat exchange equipment, the PCHE core specifically comprises heat exchange plates, the heat exchange plates are provided with semi-oval channels, the semi-oval channels on the two heat exchange plates are oppositely arranged to form an oval channel, the multiple oval channels are arranged in a stacked mode, and the heat exchange plates are arranged in the oval channel. The elliptical channels for circulating the hot fluid and the elliptical channels for circulating the cold fluid are alternately arranged; an inner inserting piece is arranged in the oval channel, one opposite side wall of the inner inserting piece is connected with the side wall, in the short axis direction, of the oval channel, and a periodic gradually-shrinking and gradually-expanding channel is formed between the remaining side wall of the inner inserting piece and the remaining side wall of the oval channel. An elliptical channel is prepared by chemical etching, and an interposer is fixed in the elliptical channel by diffusion welding technology to form a tapered and divergent channel. According to the treatment scheme, the heat exchange efficiency and the precision and consistency of the structure are improved, and the manufacturing process is simplified.

Description

Technical Field

[0001] The present application relates to the technical field of heat exchange equipment, and in particular to a PCHE core based on a gradually converging and expanding channel and a preparation method thereof. Background Art

[0002] PCHE (Printed Circuit Board Heat Exchanger) is a highly efficient and compact heat exchange equipment widely used in nuclear energy, chemical industry, petroleum, aerospace and other fields. Its channel structure has a crucial influence on the heat transfer performance. Traditional PCHE channel design often pursues straight line or simple curved type (such as Figure 1 As shown in the figure, these designs have limitations in terms of enhancing heat transfer and reducing fluid resistance. The fluid flow in traditional straight or simple curved channels often presents a laminar flow state, and the heat transfer efficiency in this flow state is relatively low because the contact area between the fluid and the wall is limited and the fluid is not easy to generate turbulence during the flow process, thus limiting the improvement of heat transfer performance.

[0003] In recent years, the converging and expanding channel has become a research hotspot because it can effectively promote fluid turbulence and improve the heat transfer coefficient. The design principle of the converging and expanding channel is to change the size of the channel cross-section so that the fluid undergoes continuous acceleration and deceleration during the flow process, thereby generating turbulence, increasing the contact area between the fluid and the wall, and improving the heat transfer efficiency. Compared with the straight channel, this converging and expanding channel will significantly increase Nu (Nussel number), and a jet effect will occur at the intersection of the converging and expanding parts, generating a significant velocity gradient at the cross section, enhancing the mixing of the cold and hot fluids, and a throttling effect will occur at the outlet of the converging section, increasing the fluid velocity along the flow direction, and continuously destroying the boundary layer, thereby intensifying the fluid turbulence and enhancing the heat transfer effect of the cold and hot fluids. And compared with the straight channel, this structure will reduce the weight by about 20%, which shows that the development prospects of lightweight PCHE heat exchangers are broad.

[0004] However, there are some problems with the methods of realizing the gradually contracting and expanding channels in the prior art. For example, the gradually contracting and expanding structure is formed on the channel wall by mechanical processing or chemical etching.

[0005] Difficulties in machining PCHE tapered channels:

[0006] 1. Precision control: Because the PCHE plate is very thin and the channels are mostly 1 to 2 mm in diameter, high-precision equipment and technology are required for the machining of such three-dimensional variable-section channels to ensure that the processed shape and size meet the design requirements;

[0007] 2. Processing difficulty: For deep and narrow channels, the difficulty of mechanical processing will increase significantly. Due to space limitations, the tool may not be able to effectively enter the channel for processing, resulting in reduced processing quality;

[0008] 3. Material removal: During the machining process, a large amount of material needs to be removed to form a gradually contracting and expanding structure. This not only increases the processing time, but may also cause unnecessary damage to the channel wall;

[0009] 4. Tool selection: Due to the complex shape of the channel wall, it is necessary to select a suitable tool for processing. However, the choice of tool is often limited by factors such as channel size and material hardness, making the choice of tool difficult.

[0010] Difficulties and problems with chemical etching:

[0011] 1. Etching uniformity: Chemical etching is a process that removes part of the material surface through chemical reaction. The uniformity of chemical etching is affected by many factors, such as the concentration, temperature, stirring speed, etc. of the etching solution. When forming a gradually converging and expanding structure on the channel wall, it is necessary to ensure that the etching solution can act evenly on the entire channel wall to avoid uneven etching;

[0012] 2. Edge distortion: During the chemical etching process, the etching solution flows and reacts quickly at the edge, which can easily lead to over-etching or shape distortion of the edge.

[0013] 3. It is difficult to control the accuracy of three-dimensional variable cross-sections: The chemical etching method can only process channels with two-dimensional variable cross-sections, but it is difficult to control the accuracy of three-dimensional variable cross-section gradually shrinking and expanding channels, and it is impossible to effectively etch out expanding and shrinking channels.

[0014] These methods are not only complex and costly, but also difficult to ensure the accuracy and consistency of the channel structure. In addition, these methods may also cause damage to the channel wall during the processing process, affecting the overall performance and life of the heat exchanger. Summary of the invention

[0015] In view of this, the embodiments of the present application provide a PCHE core based on a gradually converging and expanding channel and a preparation method thereof, which at least partially solves the problems existing in the prior art of low heat exchange efficiency, difficulty in ensuring structural accuracy and consistency, and high manufacturing cost.

[0016] In the first aspect, an embodiment of the present application provides a PCHE core based on a gradually converging and expanding channel, including a heat exchange plate, wherein a semi-elliptical channel is provided on the heat exchange plate, and an elliptical channel is formed when the semi-elliptical channels on two heat exchange plates are arranged opposite to each other, and a plurality of elliptical channels are stacked, and the elliptical channels for circulating hot fluid and the elliptical channels for circulating cold fluid are arranged alternately; an inner plug-in is arranged inside the elliptical channel, and an opposite side wall of the inner plug-in is connected to the side wall of the elliptical channel in the short axis direction, and a periodic gradually converging and expanding channel is formed between the remaining side wall of the inner plug-in and the remaining side wall of the elliptical channel.

[0017] According to a specific implementation of an embodiment of the present application, the inner plug-in is configured as spheres periodically arranged along the central axis of the elliptical channel, metal wires periodically arranged with grooves, metal wires with periodically variable cross-sections, or a chain structure of periodically arranged ellipsoids.

[0018] In a second aspect, an embodiment of the present application further provides a method for preparing a PCHE core based on a gradually converging and expanding channel as described in any embodiment of the first aspect, the method comprising:

[0019] Calculate the length-to-width ratio of the elliptical channel based on the overall layout and performance requirements of the heat exchanger;

[0020] Pre-treat the heat exchange plates;

[0021] After pretreatment, the heat exchange plates are chemically etched to form semi-elliptical channels based on the calculated aspect ratio;

[0022] Two heat exchange plates are arranged opposite to each other to form an elliptical channel;

[0023] preparing an insert;

[0024] The inner plug is inserted into the elliptical channel and placed in a vacuum or inert gas protection environment for heating, so that an opposite side wall of the inner plug is diffusion-welded with the side wall of the elliptical channel in the short axis direction, and a periodic gradually contracting and expanding channel is formed between the remaining side wall of the inner plug and the remaining side wall of the elliptical channel.

[0025] According to a specific implementation of the embodiment of the present application, chemically etching the heat exchange plate to form a semi-elliptical channel includes:

[0026] Coating photoresist: coating photoresist on the surface of the heat exchange plate to form a protective layer;

[0027] Exposure and development: Use ultraviolet light to expose the photoresist through a mask plate, on which a flow pattern of a semi-elliptical channel is engraved; put the exposed heat exchange plate into a developer to remove the photoresist in the unexposed area, exposing the area to be etched;

[0028] Chemical etching: Choose appropriate etching solution according to the heat exchange plate to etch the heat exchange plate;

[0029] After etching, cleaning, stripping and post-processing are performed.

[0030] According to a specific implementation of the embodiment of the present application, the etching temperature of the chemical etching is 20-50° C., and the etching time is 5-30 minutes.

[0031] According to a specific implementation of the embodiment of the present application, the etching depth of the chemical etching is 0.1-2 mm, and the width of the flow channel is 0.5-2 mm.

[0032] According to a specific implementation of the embodiment of the present application, the etching solution is FeCl 3 Solution or HNO 3 Mixed solution with HF, FeCl 3 30% to 40% of the solution.

[0033] According to a specific implementation of an embodiment of the present application, the photoresist is coated by spin coating, spray coating or roll coating.

[0034] According to a specific implementation of the embodiment of the present application, the heating rate during the diffusion welding process is set to 5-20° C. / min.

[0035] According to a specific implementation of the embodiment of the present application, the cooling rate during the diffusion welding process is set to 1-10° C. / min.

[0036] Beneficial effects:

[0037] The PCHE core based on the gradually shrinking and expanding channel and the preparation method thereof in the embodiment of the present application have the following beneficial effects:

[0038] 1. Improve heat exchange efficiency: The gradually contracting and expanding channel design significantly enhances fluid turbulence and increases the contact area between the fluid and the wall, thereby improving heat exchange efficiency. This design allows the fluid to continuously experience acceleration and deceleration during the flow process, enhancing the mixing and disturbance of the fluid, which is conducive to the rapid transfer of heat;

[0039] 2. Simplified manufacturing process: The manufacturing method of the present invention is relatively simple and easy to realize automated production, which greatly simplifies the manufacturing process of the gradually shrinking and expanding channel, thereby significantly reducing the manufacturing cost;

[0040] 3. Improve the accuracy and consistency of the structure: The present invention can ensure the integrity and strength of the channel structure, and this method provides a way and method for solving the problem that the general sphere is difficult to fix, so that its position will not change during welding, thereby improving the accuracy and consistency of the structure;

[0041] 4. Environmentally friendly: The present invention has little impact on the environment during manufacturing and use. Diffusion welding technology, as a clean and efficient welding method, reduces the emission of harmful gases and the generation of waste. In addition, due to the reduction in manufacturing costs, the heat exchanger of the present invention can also reduce energy consumption and carbon emissions in long-term use, which is beneficial to environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 It is a schematic diagram of the structure of a straight channel PCHE core in the prior art;

[0044] Figure 2 Schematic diagram of a PCHE heat exchange plate with a semi-elliptical channel according to an embodiment of the present invention;

[0045] Figure 3 A schematic diagram of a PCHE core of an elliptical channel according to an embodiment of the present invention;

[0046] Figure 4 A schematic diagram of processing a variable-section wire insert according to an embodiment of the present invention;

[0047] Figure 5 Schematic diagram of the structure of a variable-section iron wire insert according to an embodiment of the present invention;

[0048] Figure 6 is a transverse cross-sectional view of a gradually converging and expanding channel according to an embodiment of the present invention;

[0049] Figure 7 is a longitudinal cross-sectional view of a gradually converging and expanding channel according to an embodiment of the present invention;

[0050] Figure 8 It is a schematic diagram of assembling a gradually converging and expanding channel according to an embodiment of the present invention.

[0051] In the figure: 1: first heat exchange plate; 2: elliptical lower arc; 3: second heat exchange plate; 4: elliptical upper arc; 5: hot fluid channel; 6: cold fluid channel; 7: iron wire; 8: heating area; 9: protrusion; 10: variable cross-section iron wire insert. DETAILED DESCRIPTION

[0052] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0053] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0054] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0055] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The illustrations only show the components related to the present application rather than being drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed at will, and the component layout may also be more complicated.

[0056] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects described may be practiced without these specific details.

[0057] In the first aspect, the present application embodiment provides a PCHE core based on a gradually shrinking and expanding channel, as shown below: Figures 1 to 8 Describe in detail.

[0058] In one embodiment, a PCHE core based on a tapered and expanding channel includes a heat exchange plate, on which a semi-elliptical channel is provided. When the semi-elliptical channels on two heat exchange plates are arranged relative to each other, an elliptical channel is formed. A plurality of elliptical channels are stacked, and the elliptical channels for circulating hot fluid and the elliptical channels for circulating cold fluid are alternately arranged. An inner plug-in is arranged inside the elliptical channel, and an opposite side wall of the inner plug-in is connected to the side wall of the elliptical channel in the short axis direction, and a periodic tapered and expanding channel is formed between the remaining side wall of the inner plug-in and the remaining side wall of the elliptical channel.

[0059] In specific implementation, the structure of the heat exchange plate refers to Figure 2 As shown, the heat exchange plate is evenly distributed with semi-elliptical channels. When two heat exchange plates (the first heat exchange plate 1 and the second heat exchange plate 3) are relatively arranged together, the two semi-elliptical channels will form an elliptical channel. Figure 3 As shown, the elliptical channel is provided with an elliptical upper arc line 4 and an elliptical lower arc line 2. In the PCHE core, the elliptical channels are stacked, and the cold fluid channels 6 and the cold fluid channels are alternately arranged.

[0060] When designing the elliptical channel structure, an elliptical channel with a specific aspect ratio is designed as the basic structure according to the overall layout and performance requirements of the heat exchanger. The PCHE heat exchange plate with a semi-elliptical channel is manufactured by chemical etching. The heat exchange plate with an elliptical channel can be obtained by combining two semi-elliptical channel plates. The elliptical design not only optimizes the space utilization, but also facilitates the stable flow of the fluid in the channel.

[0061] In the specific implementation, the manufacturing of the gradually shrinking and expanding channel in this embodiment is to periodically arrange some inner plug-ins in the elliptical PCHE channel, weld the top and bottom of the inner plug-in to the elliptical channel, and the left and right sides of the inner plug-in will form a periodic gradually shrinking and expanding channel with the side wall of the elliptical channel. For the inner plug-in, it can be set in one of the following forms: 1. Use a sphere as an inner plug-in and arrange it periodically in the elliptical channel, and the diameter of the sphere is equal to the short axis of the elliptical channel; 2. Periodically set grooves on the iron wire 7, and use the entire iron wire 7 as an inner plug-in, and the diameter of the iron wire 7 is equal to the short axis of the elliptical channel; 3. Heat some periodic parts on the iron wire 7 at high temperature while applying outward axial tension on both sides, so that the diameter of the heated part becomes smaller and forms a variable cross-section with the unchanged part; 4. Use an ellipsoid and iron wire 7 to form an ellipsoid chain to form an inner plug-in, and periodically set the ellipsoid on the iron wire 7 to form an ellipsoid chain. For some other methods of inner plug-in, it is also within the scope of protection of the present invention and is not specifically limited. The iron wire 7 can be replaced by other metal wires according to actual conditions.

[0062] In one embodiment, the inner plug-in is configured as spheres periodically arranged along the central axis of the elliptical channel, metal wires periodically arranged with grooves, metal wires with periodically variable cross-sections, or a chain structure of periodically arranged ellipsoids.

[0063] In specific implementation, the structure of the metal wire with periodic variable cross-section is referred to as Figure 4 and Figure 5 Taking the iron wire 7 as an example, the preparation process of the variable cross-section iron wire insert 10 includes the following steps: firstly, a wire 7 (or other material) having a diameter equal to the minor axis of the elliptical channel is selected, and some appropriate points with certain intervals and periodic distribution are selected on the wire 7, such as Figure 4 The heating area 8 shown in the figure heats these points to a high temperature until the iron wire 7 becomes soft, and then an axial force (such as Figure 4 ), so that the diameter of the iron wire 7 on the high temperature heating part becomes smaller, while the diameter of the unheated part remains unchanged and is presented in the form of a protrusion 9, so that a variable cross-section iron wire 7 (such as Figure 5 ). The spacing between these points can be accurately calculated to ensure that the required gradually contracting and expanding channel structure can be formed in the subsequent welding process. The material of the iron wire 7 needs to be compatible with the main material of the PCHE to ensure the welding quality and overall strength.

[0064] In a second aspect, an embodiment of the present application further provides a method for preparing a PCHE core based on a gradually converging and expanding channel as described in any embodiment of the first aspect, the method comprising:

[0065] Calculate the length-to-width ratio of the elliptical channel based on the overall layout and performance requirements of the heat exchanger;

[0066] Pre-treat the heat exchange plates;

[0067] After pretreatment, the heat exchange plates are chemically etched to form semi-elliptical channels based on the calculated aspect ratio;

[0068] Two heat exchange plates are arranged opposite to each other to form an elliptical channel;

[0069] preparing an insert;

[0070] The inner plug is inserted into the elliptical channel and placed in a vacuum or inert gas protection environment for heating, so that an opposite side wall of the inner plug is diffusion-welded with the side wall of the elliptical channel in the short axis direction, and a periodic gradually contracting and expanding channel is formed between the remaining side wall of the inner plug and the remaining side wall of the elliptical channel.

[0071] The present application adopts a chemical etching process to prepare an elliptical channel, and fixes an internal plug-in inside the elliptical channel by diffusion welding to form a gradually contracting and expanding channel.

[0072] The method of the embodiment of the present application solves the following problems: 1. Low heat exchange efficiency: The present invention effectively promotes fluid turbulence and increases the contact area between the fluid and the wall by introducing a tapered and expanding channel structure, thereby significantly improving the heat exchange efficiency. 2. High manufacturing cost: The methods of realizing tapered and expanding channels in the prior art, such as mechanical processing or chemical etching, are not only complex in process but also costly. The present invention places an inner plug-in in an elliptical PCHE channel and welds them together using diffusion welding technology. The tapered and expanding channel structure formed by the inner plug-in and the elliptical channel greatly simplifies the manufacturing process of the tapered and expanding channel and reduces the manufacturing cost. 3. Structural accuracy and consistency are difficult to guarantee: The processing methods in the prior art may cause damage to the channel wall, affect the overall performance and life of the heat exchanger, and it is difficult to guarantee the accuracy and consistency of the channel structure. The present invention ensures the integrity and strength of the channel structure, while improving the accuracy and consistency of the structure and extending the service life of the heat exchanger.

[0073] In one embodiment, chemically etching the heat exchange plate to form a semi-elliptical channel includes:

[0074] Coating photoresist: coating photoresist on the surface of the heat exchange plate to form a protective layer;

[0075] Exposure and development: Use ultraviolet light to expose the photoresist through a mask plate, on which a flow pattern of a semi-elliptical channel is engraved; put the exposed heat exchange plate into a developer to remove the photoresist in the unexposed area, exposing the area to be etched;

[0076] Chemical etching: Choose appropriate etching solution according to the heat exchange plate to etch the heat exchange plate;

[0077] After etching, cleaning, stripping and post-processing are performed.

[0078] In specific implementation, the chemical etching process of the PCHE heat exchange plate includes the following steps:

[0079] Material preparation and pretreatment: usually high temperature resistant and corrosion resistant metal materials such as stainless steel (316L) are selected to clean the metal sheets to remove surface oil, oxide layer and other impurities to ensure the surface is clean;

[0080] Coating photoresist: Spin coating, spray coating or roller coating can be used to evenly coat a layer of photoresist on the surface of the metal plate to form a protective layer;

[0081] Exposure and development: Use ultraviolet light (UV) to expose the photoresist through a mask with a designed flow pattern. Put the exposed plate into the developer to remove the photoresist in the unexposed (or exposed, depending on the type of photoresist) area, exposing the metal surface to be etched;

[0082] Chemical etching: Choose the appropriate etching solution according to the metal material, immerse the plate in the etching solution, or use spray etching. Adjust according to the etching depth and etching solution concentration, usually a few minutes to tens of minutes. Control in the range of 20-50℃, the specific temperature is determined according to the etching solution and material characteristics;

[0083] Cleaning and degumming: After etching is completed, rinse the plate with deionized water to remove the residual etching solution, and use an organic solvent (such as acetone) or a special degumming agent to remove the remaining photoresist;

[0084] Post-processing: Polish or passivate the etched plate to improve surface finish and corrosion resistance.

[0085] In specific implementation, the parameter requirements for the chemical etching process include:

[0086] 1. Etching solution concentration: FeCl 3 Solution: 30%~40% (stainless steel); HNO 3 +HF mixed solution: the proportion is adjusted according to the material;

[0087] 2. Etching temperature: 20℃~50℃, determined according to the etching solution and material characteristics;

[0088] 3. Etching time: adjusted according to the etching depth and etching solution concentration, usually 5 to 30 minutes;

[0089] 4. Etching depth: according to design requirements, usually 0.1~2mm;

[0090] 5. Flow channel width: according to design requirements, usually 0.5~2mm;

[0091] 6. Surface roughness: Ra≤1.6μm (adjusted according to application requirements);

[0092] 7. Photoresist thickness: 5-20 μm, ensuring sufficient protection of unetched areas;

[0093] 8. Exposure time: adjusted according to the type of photoresist and the intensity of ultraviolet light, usually 10 to 60 seconds;

[0094] 9. Development time: adjusted according to the photoresist type and developer concentration, usually 1 to 5 minutes.

[0095] In one embodiment, the etching temperature of the chemical etching is 20-50° C., and the etching time is 5-30 minutes.

[0096] In one embodiment, the etching depth of the chemical etching is 0.1-2 mm, and the width of the flow channel is 0.5-2 mm.

[0097] In one embodiment, the etching solution is FeCl 3 Solution or HNO 3 Mixed solution with HF, FeCl 3 30% to 40% of the solution.

[0098] In one embodiment, the photoresist is coated by spin coating, spray coating or roller coating.

[0099] During specific implementation, regarding the preparation of the interposer, since the structure of the interposer can be set in various forms, the preparation methods of interposers with different structures are described in detail below.

[0100] Solution 1: Using a spherical ball as an inner plug-in, the preparation method specifically includes the following steps:

[0101] 1. Setting of sphere arrangement points

[0102] Layout principle: The spheres should be arranged periodically along the central axis of the elliptical channel. The spacing (S) between two adjacent spheres is determined according to the flow characteristics and heat transfer requirements. The specific layout spacing can be determined by studying the effects of different spacings on the flow and heat transfer characteristics through numerical simulation methods.

[0103] 2. Factors affecting layout points

[0104] Flow resistance: Too small a spacing will increase flow resistance, while too large a spacing will reduce the disturbance effect.

[0105] Heat transfer efficiency: The smaller the spacing, the stronger the flow disturbance and the higher the heat transfer efficiency, but the pressure drop will also increase.

[0106] Manufacturing process: The layout points need to consider the feasibility of the welding process.

[0107] 3. Ball fixing method

[0108] Welding fixation: Weld the top and bottom of the sphere to the inner wall of the elliptical channel to ensure that the sphere is tightly combined with the channel wall. Use a positioning rod to fix the position of the sphere before welding to ensure the layout accuracy.

[0109] Solution 2: Using the iron wire 7 with grooves as the inner plug-in, the preparation method specifically includes the following steps:

[0110] 1. Groove layout and structural dimensions

[0111] Groove arrangement: grooves are periodically processed on the iron wire 7, and the spacing (S) and groove width (W) between two adjacent grooves are determined according to design requirements. The specific operation and plan are the same.

[0112] Groove shape: Rectangular, semicircular or trapezoidal grooves can be used, and the specific shape is selected according to the flow characteristics.

[0113] 2. Method for fixing wire 7

[0114] Welding and fixing: The two ends of the iron wire 7 are welded and fixed to the inlet and outlet of the elliptical channel to ensure that the iron wire 7 is arranged in a straight line in the channel.

[0115] The diameter (D) of the wire 7 should be equal to the minor axis diameter of the elliptical channel to ensure close contact with the channel wall.

[0116] The groove arrangement needs to consider the balance between flow disturbance and pressure drop to avoid excessive increase in flow resistance.

[0117] Solution 3: Using the variable cross-section iron wire 7 as the internal plug-in, the preparation method specifically includes the following steps:

[0118] 1. Variable cross-section design

[0119] Variable cross-section position: Periodically select heating positions on the wire 7, and the length of the heating position (L 1 ) and the length of the non-heating part (L 2 ) is the same as option 1.

[0120] 2. Variable cross-section size

[0121] The diameter of the heated part (d): usually 0.5 to 0.8 times the original diameter (D), that is, d = (0.5 to 0.8) D. The diameter of the non-heated part (D): remains unchanged.

[0122] 3. Variable cross-sectional shape: The transition area should be smooth and avoid sharp changes to reduce flow resistance.

[0123] 4. Processing method

[0124] Heating and stretching: The selected part is heated to high temperature and axial tension is applied at the same time to reduce the diameter of the heated part.

[0125] Process control: Heating temperature and time need to be precisely controlled to avoid degradation of material properties.

[0126] 5. Fixation method

[0127] Welding fixation: The two ends of the iron wire 7 are welded and fixed to the inlet and outlet of the elliptical channel.

[0128] Scheme 4: Using the ellipsoid chain as the inner plug-in, the preparation method specifically includes the following steps:

[0129] 1. Ellipsoid chain design

[0130] Ellipsoid dimensions: The major axis (a) and minor axis (b) of the ellipsoid should match the dimensions of the elliptical channel.

[0131] Ellipsoid spacing: The determination of the ellipsoid spacing is the same as in scheme 1.

[0132] Ellipsoid shape: The surface of the ellipsoid should be smooth and the transition area should be smooth to reduce flow resistance.

[0133] 2. Ellipsoid chain fixing method

[0134] Welding fixation: The top and bottom of the ellipsoid are welded and fixed to the inner wall of the elliptical channel.

[0135] Connection method: The ellipsoids can be connected by thin rods to form a chain structure.

[0136] In one embodiment, the heating rate during the diffusion welding process is set to 5-20° C. / min.

[0137] In one embodiment, the cooling rate during the diffusion welding process is set to 1-10° C. / min.

[0138] In the specific implementation, for diffusion welding, the elliptical channel component equipped with the variable cross-section iron wire 7 insert is placed in a vacuum or inert gas protection environment, and heated to a certain temperature to cause diffusion welding between the insert protrusion and the channel wall. During this process, the gap between the protrusion and the elliptical channel wall gradually decreases until it is completely closed, forming a continuous gradually shrinking and expanding channel structure.

[0139] The process parameter settings for the diffusion welding process include the following:

[0140] 1. The welding temperature is usually 0.6 to 0.9 times the melting point of the material, as follows:

[0141] -Stainless steel (316L): 900℃~1100℃;

[0142] 2. Welding pressure is 5-20MPa, and the specific pressure is adjusted according to the material and plate thickness;

[0143] 3. The insulation time is 10 to 120 minutes, which can be adjusted according to the material, temperature and pressure;

[0144] 4. Vacuum degree ≤10 -3 Pa (high vacuum environment, avoid oxidation);

[0145] 5. Heating rate 5℃~20℃ / min, avoid excessive thermal stress;

[0146] 6. Cooling rate 1℃~10℃ / min, slow cooling to reduce residual stress;

[0147] 7. Surface roughness Ra≤1.6μm (the plate surface needs to be clean and flat before welding);

[0148] 8. Surface treatment: Oxide layers and contaminants must be removed before welding, usually by mechanical polishing or chemical cleaning.

[0149] The embodiments provided by the present invention have the following characteristics:

[0150] 1. Improve heat exchange efficiency: The gradually contracting and expanding channel design significantly enhances fluid turbulence and increases the contact area between the fluid and the wall, thereby improving heat exchange efficiency. This design allows the fluid to continuously experience acceleration and deceleration during the flow process, enhancing the mixing and disturbance of the fluid, which is conducive to the rapid transfer of heat.

[0151] 2. Simplified manufacturing process: The manufacturing method of the present invention is relatively simple and easy to realize automated production, which greatly simplifies the manufacturing process of the gradually converging and expanding channel, thereby significantly reducing the manufacturing cost.

[0152] 3. Improve the accuracy and consistency of the structure: The present invention can ensure the integrity and strength of the channel structure, and this method provides a way of thinking and method for the problem that general spheres are difficult to fix, so that their position will not change during welding, thereby improving the accuracy and consistency of the structure.

[0153] 4. Environmentally friendly: The present invention has little impact on the environment during manufacturing and use. Diffusion welding technology, as a clean and efficient welding method, reduces the emission of harmful gases and the generation of waste. In addition, due to the reduction in manufacturing costs, the heat exchanger of the present invention can also reduce energy consumption and carbon emissions in long-term use, which is beneficial to environmental protection.

[0154] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A PCHE core based on a gradually shrinking and expanding channel, characterized in that: The invention comprises a heat exchange plate, wherein a semi-elliptical channel is provided on the heat exchange plate, wherein the semi-elliptical channels on two heat exchange plates are arranged opposite to each other to form an elliptical channel, wherein a plurality of elliptical channels are arranged in a stacked manner, and the elliptical channels for circulating hot fluid and the elliptical channels for circulating cold fluid are arranged alternately; an inner plug-in is arranged inside the elliptical channel, wherein an opposite side wall of the inner plug-in is connected to the side wall of the elliptical channel in the short axis direction, and a periodic gradually contracting and expanding channel is formed between the remaining side wall of the inner plug-in and the remaining side wall of the elliptical channel.

2. The PCHE core based on the gradually contracting and expanding channels according to claim 1 is characterized in that: The inner plug-in is configured as spheres periodically arranged along the central axis of the elliptical channel, metal wires periodically arranged with grooves, metal wires with periodically variable cross-sections, or a chain structure of periodically arranged ellipsoids.

3. A method for preparing a PCHE core based on a gradually converging and expanding channel as claimed in claim 1 or 2, characterized in that: The method comprises: Calculate the length-to-width ratio of the elliptical channel based on the overall layout and performance requirements of the heat exchanger; Pre-treat the heat exchange plates; After pretreatment, the heat exchange plates are chemically etched to form semi-elliptical channels based on the calculated aspect ratio; Two heat exchange plates are arranged opposite to each other to form an elliptical channel; preparing an insert; The inner plug is inserted into the elliptical channel and placed in a vacuum or inert gas protection environment for heating, so that an opposite side wall of the inner plug is diffusion-welded with the side wall of the elliptical channel in the short axis direction, and a periodic gradually contracting and expanding channel is formed between the remaining side wall of the inner plug and the remaining side wall of the elliptical channel.

4. The method for preparing a PCHE core based on a gradually converging and expanding channel according to claim 3, characterized in that: The chemical etching of the heat exchange plate to form a semi-elliptical channel comprises: Coating photoresist: coating photoresist on the surface of the heat exchange plate to form a protective layer; Exposure and development: Use ultraviolet light to expose the photoresist through a mask plate, on which a flow pattern of a semi-elliptical channel is engraved; put the exposed heat exchange plate into a developer to remove the photoresist in the unexposed area, exposing the area to be etched; Chemical etching: Choose appropriate etching solution according to the heat exchange plate to etch the heat exchange plate; After etching, cleaning, stripping and post-processing are performed.

5. The method for preparing a PCHE core based on a gradually converging and expanding channel according to claim 4, characterized in that: The etching temperature of the chemical etching is 20-50° C., and the etching time is 5-30 minutes.

6. The method for preparing a PCHE core based on a gradually converging and expanding channel according to claim 4, characterized in that: The etching depth of the chemical etching is 0.1-2 mm, and the width of the flow channel is 0.5-2 mm.

7. The method for preparing a PCHE core based on a gradually converging and expanding channel according to claim 4, characterized in that: The etching solution is a FeCl3 solution or a mixed solution of HNO3 and HF, 30% to 40% of the FeCl3 solution.

8. The method for preparing a PCHE core based on a gradually converging and expanding channel according to claim 4, characterized in that: The photoresist is coated by spin coating, spray coating or roll coating.

9. The method for preparing a PCHE core based on a gradually converging and expanding channel according to claim 3, characterized in that: The heating rate during the diffusion welding process is set to 5-20°C / min.

10. The method for preparing a PCHE core based on a gradually converging and expanding channel according to claim 3, characterized in that: The cooling rate during the diffusion welding process is set at 1-10°C / min.

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