Capillary tube heat exchanger core body based on gradually-shrinking and gradually-expanding channel and preparation method of capillary tube heat exchanger core body

Abstract

The invention provides a capillary heat exchanger core based on a gradually-shrinking and gradually-expanding channel and a preparation method of the capillary heat exchanger core, and belongs to the technical field of heat exchange equipment. The capillary heat exchanger core comprises capillary heat exchange plates which are arranged in a laminated mode, and each capillary heat exchange plate comprises a capillary plate upper cover plate, a capillary plate lower cover plate and a gradually-shrinking and gradually-expanding capillary; the multiple gradually-shrinking and gradually-expanding capillary tubes are arranged between the capillary tube sheet upper cover plate and the capillary tube sheet lower cover plate side by side, the tube walls of the gradually-shrinking and gradually-expanding capillary tubes are arranged to be of gradually-shrinking and gradually-expanding structures in the axial direction so that gradually-shrinking and gradually-expanding channels can be formed in the gradually-shrinking and gradually-expanding structures, and gradually-shrinking areas and gradually-expanding areas in the gradually-shrinking and gradually-expanding structures are alternately arranged. According to the treatment scheme, the heat exchange efficiency of the heat exchanger is improved, the structural strength is enhanced, the manufacturing process is simplified, and flexible customization can be achieved.

Description

Technical Field

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

[0002] In heat exchange technology, capillary heat exchangers are widely used in various industrial and living fields due to their compact structure, light weight, and high heat exchange efficiency. Moreover, with the rise of supercritical carbon dioxide power generation and the widespread application of supercritical carbon dioxide heat pumps, traditional heat exchangers are difficult to meet the requirements of efficient and compact systems, and it is necessary to develop new high-temperature and high-pressure compact heat exchangers. Compared with traditional shell and tube heat exchangers, capillary heat exchangers have stronger tolerance, better heat exchange performance, and higher compactness, which can effectively reduce the volume of new power generation systems. At the same time, compared with other types of high-temperature and high-pressure heat exchangers such as printed circuit board heat exchangers, capillary heat exchangers have lower manufacturing costs and have broad application prospects in energy conversion methods such as carbon dioxide power generation and industrial production fields. Traditional capillary heat exchangers usually use capillaries of equal cross-section as fluid channels. Although this design meets the basic heat exchange requirements to a certain extent, there is still room for improvement in fluid dynamics and heat exchange efficiency.

[0003] The design of a tapered and expanding channel is a method that can effectively improve the dynamic characteristics and heat exchange efficiency of the fluid in the pipeline. The tapered 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 tapered 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 exchange efficiency. Compared with the straight channel, this tapered and expanding channel will significantly increase Nu (Nussel number), and a jet effect will occur at the intersection of the tapered 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 tapered section, increasing the fluid velocity along the flow direction, and continuously destroying the boundary layer, thereby intensifying the fluid turbulence and enhancing the heat exchange 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 tapered and expanding heat exchanger with variable cross-section has broad development prospects. However, it is a very challenging task to realize the manufacturing of such a complex structure at the capillary level.

[0004] Traditional manufacturing methods, such as mechanical drawing, 3D printing, chemical etching, and electrochemical machining, are not only complex and costly, but also difficult to ensure the accuracy and consistency of the capillary channel. In addition, these methods may also damage the capillary material, affecting its overall performance and lifespan.

[0005] The main problems of mechanical drawing manufacturing:

[0006] 1. Complexity of mold manufacturing: Mechanical drawing uses a mold with a gradient shape to cold-draw the metal capillary tube, gradually changing the inner diameter of the tube. The mold design determines the gradient form of the tube inner diameter, which requires a high-precision mold, which has a high manufacturing cost and is difficult to replace after wear;

[0007] 2. Processing accuracy: Springback may occur during the cold drawing process, resulting in actual dimensional deviation of the gradient inner diameter;

[0008] 3. Processing length limitation: It may be difficult to evenly control the inner diameter gradient of long-distance capillaries.

[0009] The main problems of 3D printing:

[0010] 1. Precision limitation: Using computer models to accurately control the inner and outer diameters of the pipe, capillaries with gradient inner diameters are directly manufactured through additive manufacturing technology (such as metal 3D printing or polymer 3D printing). However, the existing 3D printing technology may not be accurate enough when manufacturing ultra-small diameter capillaries, especially the internal structure;

[0011] 2. Printing speed: 3D printing takes a long time to print, is not suitable for mass production, and has high production costs;

[0012] 3. Post-processing: After printing, additional polishing of the inner wall is usually required to meet fluid mechanics requirements.

[0013] The main problems of electrochemical machining:

[0014] 1. Difficult to control: Electrochemical machining uses electrolyte to corrode the inner wall of the capillary, gradually expand or reduce the inner diameter, and control the electrolytic current and corrosion time to achieve a gradual shape. It is necessary to accurately control the current density and electrolyte flow rate to avoid non-uniform corrosion;

[0015] 2. Environmental impact: The treatment of electrolyte and the discharge of waste liquid require additional environmental protection measures;

[0016] 3. Surface roughness: Further polishing may be required after processing to meet high finish requirements.

[0017] Therefore, a more efficient, economical and less damaging manufacturing method is needed to realize the application of tapered and divergent channels in capillary heat exchangers. Summary of the invention

[0018] In view of this, the embodiments of the present application provide a capillary heat exchanger core based on a gradually converging and expanding channel and a preparation method thereof, which at least partially solve the problems of low heat exchange efficiency and difficult precision control existing in the prior art.

[0019] In the first aspect, an embodiment of the present application provides a capillary heat exchanger core based on a tapered and expanding channel, comprising capillary heat exchange plates arranged in a stacked manner, the capillary heat exchange plates comprising a capillary plate upper cover plate, a capillary plate lower cover plate and tapered and expanding capillaries, a plurality of tapered and expanding capillaries are arranged side by side between the capillary plate upper cover plate and the capillary plate lower cover plate, the tube wall of the tapered and expanding capillary tube is arranged as a tapered and expanding structure along the axial direction to form a tapered and expanding channel inside thereof, and the tapered area and the gradually expanding area in the tapered and expanding structure are arranged alternately.

[0020] In a second aspect, an embodiment of the present application further provides a method for preparing a capillary heat exchanger core based on a gradually converging and expanding channel as described in the first aspect, the method comprising:

[0021] According to the design requirements of the heat exchanger, select capillary tubes with appropriate materials and wall thickness;

[0022] The capillary tube is provided with heating points which are periodically distributed along its axial direction;

[0023] Heating the heating point;

[0024] The capillary is processed so that the heating point forms a gradually contracting area or a gradually expanding area, and the gradually contracting area and the gradually expanding area are arranged alternately to form a gradually contracting and gradually expanding capillary;

[0025] Laying a plurality of gradually converging and expanding capillaries side by side between an upper cover plate of a capillary plate and a lower cover plate of a capillary plate;

[0026] The gradually converging and expanding capillary is fixed between the upper cover plate of the capillary plate and the lower cover plate of the capillary plate by diffusion welding to form a capillary heat exchange plate;

[0027] According to the heat exchange requirements, the capillary heat exchange plates are stacked to form a capillary heat exchanger core.

[0028] According to a specific implementation of the embodiment of the present application, the capillary is processed so that the heating point forms a gradually shrinking area or a gradually expanding area, including:

[0029] While heating, an axial tensile force is applied to the capillary to stretch it;

[0030] After stopping heating, maintain the axial tension until cooling to room temperature, so that a tapered area is formed at the heating point.

[0031] According to a specific implementation of the embodiment of the present application, the stretching speed is set to 1-10 mm / s, and the cooling rate in the process of maintaining the axial tension until cooling to room temperature is set to 1-10°C / min.

[0032] According to a specific implementation of the embodiment of the present application, the capillary is processed so that the heating point forms a gradually shrinking area or a gradually expanding area, including:

[0033] While heating, gas or liquid is introduced into the capillary to increase the internal pressure, causing the heated point to expand;

[0034] After stopping heating and internal pressurization, the expanded state is maintained until cooling to room temperature, so that the heating point forms a gradually expanding area.

[0035] According to a specific implementation of the embodiment of the present application, the capillary is processed so that the heating point forms a gradually shrinking area or a gradually expanding area, including:

[0036] Use a roller to press the heating point to create a depression at the heating point of the capillary;

[0037] Cool to room temperature to form a tapered area at the heating point.

[0038] According to a specific implementation of the embodiment of the present application, the shape of the roller is set to be a U-shaped tube wheel or a V-shaped roller.

[0039] According to a specific implementation of the embodiment of the present application, heating the heating point includes:

[0040] The heating point is heated by laser heating or high-frequency induction heating.

[0041] According to a specific implementation of the embodiment of the present application, the heating rate of the diffusion welding is set to 5-20°C / min, and the cooling rate is set to 1-10°C / min.

[0042] According to a specific implementation of the embodiment of the present application, the welding pressure of the diffusion welding is set to 5-20 MPa.

[0043] Beneficial effects:

[0044] The capillary heat exchanger core based on the gradually converging and expanding channel and the preparation method thereof in the embodiment of the present application have the following beneficial effects:

[0045] 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;

[0046] 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;

[0047] 3. Enhanced structural strength: Diffusion welding of stainless steel sheets and capillaries provides a solid packaging structure, enhancing the overall strength and durability of the heat exchanger;

[0048] 4. Flexible customization: By adjusting the heating point position and the roller shape, capillary channels with different cross-sections can be flexibly manufactured to meet the needs of different application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] 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.

[0050] Figure 1 is a schematic diagram of a capillary according to an embodiment of the present invention;

[0051] Figure 2 A schematic diagram of a capillary processed by roller pressing according to an embodiment of the present invention;

[0052] Figure 3 is a schematic structural diagram of a gradually converging and expanding capillary according to an embodiment of the present invention;

[0053] Figure 4 The overall structure diagram of the capillary heat exchange plate according to one embodiment of the present invention is

[0054] Figure 5 A cross-sectional view in the width direction of a capillary heat exchange plate according to an embodiment of the present invention;

[0055] Figure 6 is a cross-sectional view in the length direction of a capillary heat exchange plate according to an embodiment of the present invention;

[0056] Figure 7 A schematic diagram of a capillary heat exchanger core according to an embodiment of the present invention;

[0057] Figure 8 Schematic diagram of a capillary tube subjected to heating and stretching processing according to an embodiment of the present invention.

[0058] In the figure: 1. capillary; 2. heating point; 3. gradually converging and expanding capillary; 4. gradually converging area; 5. gradually expanding area; 6. capillary plate upper cover; 7. fluid channel; 8. capillary plate lower cover; 9. capillary heat exchange plate. DETAILED DESCRIPTION

[0059] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] The embodiment of the present application provides a capillary heat exchanger core based on a gradually converging and expanding channel, as shown below Figures 1 to 8 Describe in detail.

[0065] In the first aspect, an embodiment of the present application provides a capillary heat exchanger core 1 based on a tapered and expanding channel, comprising a stacked capillary heat exchange plate 9, the capillary heat exchange plate 9 comprising a capillary plate upper cover plate 6, a capillary plate lower cover plate 8 and a tapered and expanding capillary 3, a plurality of tapered and expanding capillaries 3 are arranged side by side between the capillary plate upper cover plate 6 and the capillary plate lower cover plate 8, the tube wall of the tapered and expanding capillary 3 is arranged as a tapered and expanding structure along the axial direction to form a tapered and expanding channel inside thereof, and the tapered area 4 and the gradually expanding area 5 in the tapered and expanding structure are arranged alternately.

[0066] In specific implementation, the structure of the capillary 1 is as follows: Figure 1 As shown, the structure of the gradually converging and expanding capillary 3 is shown in FIG. Figure 3 As shown, the tapered and divergent capillary 3 includes a tapered region 4 and a divergent region 5, and the tapered region 4 and the divergent region 5 are arranged alternately. A fluid channel 7 is formed inside the tapered and divergent capillary 3, and by being set as a tapered and divergent channel, fluid turbulence is effectively promoted, and the contact area between the fluid and the wall is increased, thereby significantly improving the heat exchange efficiency.

[0067] For the preparation of the gradually converging and expanding capillary 3, the following steps can be adopted:

[0068] Select a capillary 1 with suitable material and wall thickness (select suitable material and wall thickness according to the design pressure, corrosion resistance, melting point, economy and other conditions of the heat exchanger) as the raw material to ensure that it has good plasticity and sufficient strength under high temperature heating to withstand subsequent processing. Use laser or high-frequency induction heating technology to perform local high-temperature heating (such as 30°) on the preset periodically distributed heating points 2 on the capillary 1 (use numerical simulation and other means to simulate the influence of different points on flow and heat transfer, and then select the appropriate point spacing) Figure 2 ) to soften these areas without affecting the properties of the surrounding materials. The selection of heating point 2 and temperature control must be precise to ensure the consistency and controllability of the deformation. In the designated area after heating and softening, a roller with a specific shape (V-shaped roller, U-shaped roller, etc.) is used to press to make the capillary 1 partially concave and form the desired gradually shrinking and expanding cross-section (such as Figure 3 ). During the roller pressing process, it is necessary to ensure that the cross-section changes smoothly after pressing to avoid a sudden increase in resistance when the fluid flows. At the same time, by adjusting the position of the heating point 2 and the shape of the roller, the capillary 1 channel with different cross-section changes can be flexibly manufactured to meet the needs of different application scenarios.

[0069] The tapered and gradually expanding capillaries 3 are arranged in a row and disposed between the capillary plate upper cover 6 and the capillary plate lower cover 8. The tapered and gradually expanding capillaries 3, the capillary plate upper cover 6 and the capillary plate lower cover 8 are fixed by diffusion welding technology to obtain a capillary heat exchange plate 9. During the diffusion welding process, the temperature, pressure and time parameters need to be controlled to ensure that the welding interface is free of defects while maintaining the integrity of the internal channel of the capillary 1. According to different heat exchange requirements, the capillary heat exchange plates 9 are stacked to meet the heat exchange requirements, and then the capillary 1 heat exchanger core is prepared. The diffusion welding of the capillary 1 plate upper and lower covers and the tapered and gradually expanding capillaries 3 provides a solid packaging structure, which enhances the overall strength and durability of the heat exchanger.

[0070] In a second aspect, the present application also provides a method for preparing a capillary tube heat exchanger core based on a gradually converging and expanding channel as described in the first aspect, the method comprising:

[0071] According to the design requirements of the heat exchanger, select a capillary tube 1 with appropriate material and wall thickness;

[0072] The capillary 1 is provided with heating points 2 which are periodically distributed along the axial direction thereof;

[0073] Heating the heating point 2;

[0074] The capillary 1 is processed so that the heating point 2 forms a gradually contracting region 4 or a gradually expanding region 5, and the gradually contracting region 4 and the gradually expanding region 5 are arranged alternately to form a gradually contracting and expanding capillary 3;

[0075] Lay a plurality of gradually converging and expanding capillaries 3 in parallel between an upper cover plate 6 of a capillary sheet and a lower cover plate 8 of a capillary sheet;

[0076] The gradually converging and expanding capillary 3 is fixed between the capillary plate upper cover 6 and the capillary plate lower cover 8 by diffusion welding to form a capillary heat exchange plate 9;

[0077] According to the heat exchange requirements, the capillary heat exchange plates 9 are stacked to form the capillary heat exchanger core 1 .

[0078] The following describes a method for preparing a capillary tube 1 heat exchanger core based on a gradually converging and expanding channel, taking a method for roller pressing a heated capillary tube 1 as an example, and includes the following steps:

[0079] 1. Processing of periodically variable cross-section gradually contracting and expanding capillary 3: Select capillary 1 with suitable material and wall thickness as raw material to ensure that it has good plasticity and sufficient strength under high temperature heating to withstand subsequent processing. Use laser or high-frequency induction heating technology to locally heat the preset periodically distributed heating points 2 on the capillary 1 (such as Figure 2) to soften these areas without affecting the properties of the surrounding materials. The selection of heating point 2 and temperature control must be precise to ensure the consistency and controllability of the deformation. In the designated area after heating and softening, a roller with a specific shape is used to press to make the capillary 1 partially concave to form the desired gradually shrinking and expanding cross-section (such as Figure 3 The roller design should ensure that the cross-section changes smoothly after pressing to avoid sudden increase in resistance when the fluid flows.

[0080] 2. Packaging of capillary heat exchange plate 9: For the processed gradually converging and expanding capillary 3, lay it flat between two thinner metal plates (the upper and lower cover plates of the capillary 1 half plate), and firmly combine the three by diffusion welding technology (such as Figures 4 to 6 ). During the diffusion welding process, the temperature, pressure and time parameters need to be controlled to ensure that the welding interface is free of defects while maintaining the integrity of the internal channel of the capillary 1.

[0081] 3. Capillary 1 heat exchanger core: Figure 7 As shown, according to different heat exchange requirements, the capillary heat exchange plates 9 are stacked to meet the heat exchange requirements.

[0082] In one embodiment, referring to Figure 8 , the capillary 1 is processed so that the heating point 2 forms a gradually contracting region 4 or a gradually expanding region 5, including:

[0083] While heating, an axial tensile force is applied to the capillary 1 to stretch it;

[0084] After stopping heating, the axial tension is maintained until cooling to room temperature, so that the heating point 2 forms a tapered area 4.

[0085] Specifically, the step of preparing the gradually converging and expanding capillary 3 by applying an axial force to the capillary 1 includes:

[0086] Material preparation: Select suitable capillary tube materials (such as stainless steel, copper alloy, etc.) to ensure that the material has good ductility and heat resistance. Clean the surface of the tube to remove oil and oxide layer.

[0087] Heating and softening: Use high-frequency induction heating or laser heating equipment to locally heat specific points on the round tube. The heating temperature is controlled near the softening point of the material (usually 0.6 to 0.8 times the melting point of the material). The heating time is determined by the material thickness and heating method, usually a few seconds to tens of seconds.

[0088] Apply axial tension: While heating and softening, apply axial tension to both ends of the tube. The magnitude of the tension is determined according to the material properties and the target deformation, usually 0.5-0.8 times the yield strength of the material. The stretching speed is controlled at 1-10mm / s to avoid breakage caused by too fast a stretching speed.

[0089] Cooling and shaping: After stopping heating, maintain axial tension until the softened part cools to room temperature. The cooling rate is controlled at 1-10℃ / min to reduce residual stress.

[0090] Repeat the operation: According to the design requirements, periodically select heating point 2 on the circular tube and repeat the above steps to achieve periodic changes in the cross section.

[0091] Furthermore, the process parameter requirements during the application of axial force specifically include the following:

[0092] Heating temperature: near the softening point of the material (usually 0.6 to 0.8 times the melting point of the material);

[0093] Heating time: a few seconds to tens of seconds, adjusted according to material thickness and heating method;

[0094] Axial tension: 0.5 to 0.8 times the yield strength of the material;

[0095] Stretching speed: 1-10mm / s;

[0096] Cooling rate: 1-10℃ / min;

[0097] Spacing between heating points 2: determined according to design requirements, usually 2-5 times the diameter of capillary 1.

[0098] In one embodiment, the capillary 1 is processed so that the heating point 2 forms a gradually contracting region 4 or a gradually expanding region 5, including:

[0099] While heating, gas or liquid is introduced into the capillary 1 to increase the internal pressure, causing the heating point 2 to expand;

[0100] After stopping heating and internal pressurization, the expanded state is maintained until cooling to room temperature, so that the heating point 2 forms a gradually expanding area 5.

[0101] Specifically, the steps of preparing the gradually converging and expanding capillary 3 by internally expanding the capillary 1 include:

[0102] Material preparation: Select suitable capillary tube material and ensure that the material has good ductility and heat resistance. Clean the surface of the tube to remove oil and oxide layer.

[0103] Heating and softening: Use high-frequency induction heating or laser heating equipment to locally heat specific points on the round tube. The heating temperature is controlled near the softening point of the material (usually 0.6-0.8 times the melting point of the material). The heating time is determined by the material thickness and heating method, usually a few seconds to tens of seconds.

[0104] Internal expansion: While heating and softening, high-pressure gas or liquid is introduced into the tube to expand the softened part. The pressure is determined according to the material properties and the target deformation, usually 0.5-1 times the yield strength of the material. The expansion time is controlled within a few seconds to tens of seconds to ensure that the softened part is fully deformed.

[0105] Cooling and shaping: After stopping heating and internal pressure, keep the expansion state until the softened part cools to room temperature. The cooling rate is controlled at 1-10℃ / min to reduce residual stress.

[0106] Repeat the operation: According to the design requirements, periodically select heating point 2 on the circular tube and repeat the above steps to achieve periodic changes in the cross section.

[0107] Furthermore, the process parameter requirements for internal expansion include the following:

[0108] Heating temperature: near the softening point of the material (usually 0.6-0.8 times the melting point);

[0109] Heating time: a few seconds to tens of seconds, adjusted according to material thickness and heating method;

[0110] Internal pressure: 0.5-1 times the yield strength of the material;

[0111] Expansion time: a few seconds to tens of seconds, to ensure that the softened part is fully deformed;

[0112] Cooling rate: 1-10℃ / min;

[0113] Spacing between heating points 2: determined according to design requirements, usually 2-5 times the diameter of capillary 1.

[0114] In one embodiment, the capillary 1 is processed so that the heating point 2 forms a gradually contracting region 4 or a gradually expanding region 5, including:

[0115] Use a roller to press the heating point 2 to make the heating point 2 of the capillary 1 concave;

[0116] After cooling to room temperature, the heating point 2 forms a tapered area 4 .

[0117] Furthermore, the shape of the roller is set to be a U-shaped roller or a V-shaped roller.

[0118] In one embodiment, heating the heating point 2 includes:

[0119] The heating point 2 is heated by laser heating or high-frequency induction heating.

[0120] When implemented, the specific requirements of laser heating technology include:

[0121] 1) Main process parameters:

[0122] Laser power density: According to the different types of materials, adjust the laser power density. The higher the power density, the faster the heating speed, but too high power density may cause the workpiece surface to overheat or melt.

[0123] Laser irradiation time: Control the time of laser action to achieve the desired heating depth and temperature.

[0124] Scanning speed: The speed at which the laser beam moves on the workpiece surface. The faster the scanning speed, the shorter the heating time and the shallower the quenching layer depth.

[0125] Focal length and focal depth: The larger the focal length, the greater the focal depth, which is suitable for heating workpieces with complex shapes.

[0126] 2) Process requirements:

[0127] Workpiece surface treatment: The workpiece needs to be blackened to increase the absorption rate of laser energy.

[0128] Laser beam mode: Obtaining a rectangular hardened section can be achieved by optical methods or by adjusting the laser's resonant cavity.

[0129] Cooling method: Self-cooling quenching is adopted, and cooling is carried out by heat conduction inside the workpiece.

[0130] When implemented, the specific requirements of high-frequency induction heating technology include:

[0131] 1) Main process parameters:

[0132] Heating frequency: Select the appropriate frequency according to the size of the workpiece and the required hardened layer depth. The higher the frequency, the shallower the heating depth.

[0133] Power: Select the appropriate power according to the size of the workpiece and heating requirements.

[0134] Heating time: Control the heating time to achieve the desired temperature.

[0135] 2) Process requirements:

[0136] Inductor design: Design the appropriate inductor according to the shape and size of the workpiece to ensure uniform heating.

[0137] Cooling medium: After heating, it is necessary to spray water or immerse in oil to cool immediately to complete the quenching process.

[0138] Heating uniformity: Ensure uniform heating of the workpiece surface and interior to avoid local overheating or insufficient heating.

[0139] In one embodiment, the heating rate of the diffusion welding is set to 5-20° C. / min, and the cooling rate is set to 1-10° C. / min.

[0140] In one embodiment, the welding pressure of the diffusion welding is set to 5-20 MPa.

[0141] In specific implementation, the diffusion welding process parameter requirements include the following:

[0142] Welding temperature: usually 0.6-0.9 times the melting point of the material, as follows:

[0143] Stainless steel (316L): 900-1100℃,

[0144] Nickel-based alloy (Inconel 600 / 625): 1000-1200°C;

[0145] Welding pressure: 5-20MPa, the specific pressure is adjusted according to the material and plate thickness;

[0146] Insulation time: 10-120 minutes, adjusted according to material, temperature and pressure;

[0147] Vacuum degree: ≤10 -3 Pa (high vacuum environment, avoid oxidation);

[0148] Heating rate: 5-20℃ / min, avoid excessive thermal stress;

[0149] Cooling rate: 1-10℃ / min, slow cooling to reduce residual stress;

[0150] Surface roughness: Ra≤1.6μm (the plate surface must be clean and flat before welding);

[0151] Surface treatment: Oxide layers and contaminants must be removed before welding, usually by mechanical polishing or chemical cleaning.

[0152] The embodiments provided by the present invention have the following characteristics:

[0153] 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;

[0154] 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;

[0155] 3. Enhanced structural strength: Diffusion welding of stainless steel sheets and capillaries provides a solid packaging structure, enhancing the overall strength and durability of the heat exchanger;

[0156] 4. Flexible customization: By adjusting the heating point position and the roller shape, capillary channels with different cross-sections can be flexibly manufactured to meet the needs of different application scenarios.

[0157] 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 capillary heat exchanger core based on a gradually converging and expanding channel, characterized in that: The invention comprises a capillary heat exchange plate (9) arranged in a stacked manner, wherein the capillary heat exchange plate (9) comprises a capillary plate upper cover plate (6), a capillary plate lower cover plate (8) and a gradually converging and gradually expanding capillary tube (3), wherein a plurality of gradually converging and gradually expanding capillaries (3) are arranged side by side between the capillary plate upper cover plate (6) and the capillary plate lower cover plate (8), wherein the tube wall of the gradually converging and gradually expanding capillary tube (3) is arranged in a gradually converging and gradually expanding structure in the axial direction so as to form a gradually converging and gradually expanding channel therein, and the gradually converging area (4) and the gradually expanding area (5) in the gradually converging and gradually expanding structure are arranged alternately.

2. A method for preparing a capillary heat exchanger core based on a gradually converging and expanding channel according to claim 1, characterized in that: The method comprises: According to the design requirements of the heat exchanger, a capillary tube (1) with appropriate material and wall thickness is selected; The capillary (1) is provided with heating points (2) which are periodically distributed along the axial direction thereof; Heating the heating point (2); The capillary (1) is processed so that the heating point (2) forms a gradually contracting region (4) or a gradually expanding region (5), and the gradually contracting region (4) and the gradually expanding region (5) are arranged alternately to form a gradually contracting and gradually expanding capillary (3); Laying a plurality of gradually converging and expanding capillaries (3) in parallel between an upper cover plate (6) of a capillary plate and a lower cover plate (8) of a capillary plate; Fixing the gradually converging and expanding capillary (3) between the capillary plate upper cover (6) and the capillary plate lower cover (8) by diffusion welding to form a capillary heat exchange plate (9); According to the heat exchange requirements, the capillary heat exchange plates (9) are stacked to form a capillary heat exchanger core.

3. The method for preparing a capillary heat exchanger core based on a gradually converging and expanding channel according to claim 2, characterized in that: The capillary (1) is processed so that the heating point (2) forms a gradually contracting region (4) or a gradually expanding region (5), comprising: While heating, applying axial tension to the capillary (1) to stretch it; After stopping heating, the axial tension is maintained until cooling to room temperature, so that the heating point (2) forms a tapered area.

4. The method for preparing a capillary heat exchanger core based on a gradually converging and expanding channel according to claim 3, characterized in that: The stretching speed of the stretching is set to 1-10 mm / s, and the cooling rate during the process of maintaining the axial tension until cooling to room temperature is set to 1-10° C. / min.

5. The method for preparing a capillary heat exchanger core based on a gradually converging and expanding channel according to claim 2, characterized in that: The capillary (1) is processed so that the heating point (2) forms a gradually contracting region (4) or a gradually expanding region (5), comprising: While heating, gas or liquid is introduced into the capillary (1) to increase the internal pressure, thereby causing the heated point (2) to expand; After stopping heating and internal pressurization, the expanded state is maintained until cooling to room temperature, so that the heating point (2) forms a gradually expanding area (5).

6. The method for preparing a capillary heat exchanger core based on a gradually converging and expanding channel according to claim 2, characterized in that: The capillary (1) is processed so that the heating point (2) forms a gradually contracting region (4) or a gradually expanding region (5), comprising: Using a roller to press the heating point (2) to cause a depression in the heating point (2) of the capillary (1); Cooling to room temperature causes the heating point (2) to form a tapered area (4).

7. The method for preparing a capillary heat exchanger core based on a gradually converging and expanding channel according to claim 6, characterized in that: The shape of the roller is set to be a U-shaped roller or a V-shaped roller.

8. The method for preparing a capillary heat exchanger core based on a gradually converging and expanding channel according to claim 2, characterized in that: The step of heating the heating point (2) comprises: The heating point (2) is heated by laser heating or high-frequency induction heating.

9. The method for preparing a capillary heat exchanger core based on a gradually converging and expanding channel according to claim 2, characterized in that: The heating rate of the diffusion welding is set to 5-20°C / min, and the cooling rate is set to 1-10°C / min.

10. The method for preparing a capillary heat exchanger core based on a gradually converging and expanding channel according to claim 2, characterized in that: The welding pressure of the diffusion welding is set to 5-20 MPa.

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