Fire-free automatic brazing method for heat exchanger and heat exchanger

Abstract

The invention discloses a fireless automatic brazing method for a heat exchanger and the heat exchanger, and relates to the technical field of heat exchanger manufacturing. The fireless automatic brazing method for the heat exchanger comprises the following steps that a plurality of to-be-welded semicircular pipes located at the same end of the heat exchanger are divided into a plurality of to-be-welded pipe sets, the to-be-welded parts of the semicircular pipes in the same to-be-welded pipe group have the same welding parameter requirement; induction heaters matched with the to-be-welded pipe sets in number and shape are provided, each induction heater is provided with a profiling area, and the profiling areas of the induction heaters are arranged on the periphery of the same to-be-welded pipe set in a one-to-one surrounding mode; and the induction heater is powered on, so that induction brazing is conducted on the to-be-welded portions of all the semicircular pipes in the corresponding to-be-welded pipe set. According to the technical scheme, the one-time brazing qualification rate of the special-shaped heat exchanger can be increased, the later repair welding rate is reduced, the production efficiency is improved, and the production cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of heat exchanger manufacturing technology, and in particular to a flameless automatic brazing method for heat exchangers and a heat exchanger. Background Technology

[0002] Currently, irregularly shaped heat exchangers used in industries such as air conditioning and HVAC typically employ automated flame brazing to weld semi-circular tubes and long U-tubes. Due to their structural limitations, irregularly shaped heat exchangers experience low first-pass brazing yield and high subsequent repair welding rates (usually exceeding 60%) when using automated flame brazing, resulting in significant quality fluctuations. Because of the high post-weld defect rate, it is usually necessary to assign one person to inspect the weld quality at the end of each equipment unit, and one to two welders to perform repair welding operations. This results in a large number of operators, low production efficiency, and high production costs. Summary of the Invention

[0003] The main objective of this invention is to propose a flameless automatic brazing method for heat exchangers, which aims to improve the first-pass brazing qualification rate of irregularly shaped heat exchangers, reduce the rate of subsequent re-welding, improve production efficiency, and reduce production costs.

[0004] To achieve the above objectives, the present invention proposes a flameless automatic brazing method for heat exchangers, comprising the following steps:

[0005] Multiple semicircular tubes to be welded located at the same end of the heat exchanger are divided into multiple groups of tubes to be welded. The semicircular tubes to be welded in the same group of tubes to be welded have the same welding parameter requirements.

[0006] An induction heater is provided that is adapted to the number and shape of the tube groups to be welded. The induction heater has a contouring area, and the contouring area of ​​each induction heater is arranged one-to-one around the same group of tube groups to be welded.

[0007] The induction heater is energized to perform induction brazing on the parts of the semi-circular tubes in the tube group to be welded.

[0008] In one embodiment, the induction heater includes an induction heating coil for enclosing the contoured area, and the semi-circular tubes in the welding assembly are provided with welding rings at the welding locations. The outermost radial edge of the welding ring of each semi-circular tube located within the induction heating coil maintains a preset distance from the inner effective coil of the induction heating coil.

[0009] In one embodiment, the distance between the outermost of the solder joints of the plurality of semicircular tubes located within the induction heating coil and the inner effective coil of the induction heating coil is consistent or has a preset tolerance.

[0010] In one embodiment, the induction heater includes multiple turns of the induction heating coil, which are arranged along the axial direction of the semicircular tube to heat the semicircular tube.

[0011] In one embodiment, the step of energizing the induction heater to perform induction brazing on the welding portions of the semicircular tubes within the welding assembly includes:

[0012] The induction heating coil is kept in a fixed position relative to the semi-circular tube to fix and heat the welding ring to be welded on the semi-circular tube.

[0013] Alternatively, the induction heating coil may oscillate relative to the semi-circular tube within a preset range to oscillate and heat the weld ring to be welded on the semi-circular tube.

[0014] In one embodiment, in the step of energizing the induction heater to perform induction brazing on the parts of the semi-circular tubes in the tube assembly to be welded, the induction heater is connected to a high-frequency induction heating power supply, the output frequency of which is 10-100KHz.

[0015] In one embodiment, before the step of energizing the induction heater to perform induction brazing on the welding portions corresponding to each semi-circular tube in the welding assembly, the following step is further included:

[0016] Based on the arrangement of the multiple sets of tubes to be welded, the heating sequence of the multiple induction heaters is determined so that the multiple sets of tubes to be welded are induction brazed stepwise or simultaneously.

[0017] In one embodiment, the step of determining the heating sequence of the multiple induction heaters based on the arrangement of the multiple groups of tubes to be welded, so as to enable the multiple groups of tubes to be welded to undergo stepwise or synchronous induction brazing, includes:

[0018] When the distance between two adjacent groups of pipes to be welded is less than the preset safety distance, the two adjacent induction heaters are controlled to heat in stages in sequence so that the two adjacent groups of pipes to be welded are induction brazed step by step.

[0019] When the distance between two adjacent sets of pipe groups to be welded is greater than or equal to a preset safety distance, the two adjacent induction heaters are controlled to heat synchronously so that the two adjacent sets of pipe groups to be welded are synchronously induction brazed.

[0020] In one embodiment, in the step of dividing multiple semi-circular tubes to be welded located at the same end of the heat exchanger into multiple groups of tubes to be welded, the arrangement of the multiple groups of tubes to be welded includes:

[0021] Multiple semi-circular tubes to be welded are divided into two groups of tubes to be welded, and the two groups of tubes to be welded are symmetrically arranged on both sides of the width centerline of the heat exchanger.

[0022] Alternatively, the multiple semi-circular tubes to be welded are divided into three groups of tubes to be welded, namely the first group of tubes to be welded, the second group of tubes to be welded, and the third group of tubes to be welded. The first group of tubes to be welded is located in the middle of the width direction of the heat exchanger, and the second group of tubes to be welded and the third group of tubes to be welded are respectively arranged on both sides of the first group of tubes to be welded along the width direction of the heat exchanger.

[0023] Alternatively, the multiple semi-circular tubes to be welded are divided into three groups of tubes to be welded, namely the first group of tubes to be welded, the second group of tubes to be welded, and the third group of tubes to be welded. The first group of tubes to be welded is located in the middle of the width direction of the heat exchanger. The second group of tubes to be welded includes two sub-groups of tubes to be welded located on both sides of the first group of tubes to be welded along the width direction of the heat exchanger. The third group of tubes to be welded includes two sub-groups of tubes to be welded located on both sides of the second group of tubes to be welded along the width direction of the heat exchanger.

[0024] The present invention also proposes a heat exchanger comprising a plurality of U-shaped heat exchange tubes and a plurality of semi-circular tubes, wherein the U-shaped heat exchange tubes and the semi-circular tubes are welded and fixed by the heat exchanger non-flame automatic brazing method described above.

[0025] The technical solution of this invention first groups multiple semicircular tubes to be welded according to their specifications, shape, and size, thus creating multiple groups of tubes to be welded. The specifications, shape, and size of each semicircular tube within each group are consistent, ensuring that the structure, shape, and size of the weld joints on each semicircular tube within the same group are essentially the same. Then, by providing an induction heater adapted to the number and shape of the tube groups, multiple semicircular tubes within the same group can be placed within the contouring area of ​​the induction heater. The welding parameters for the welded parts of each semicircular tube within the same contouring area are identical, ensuring that the induction heater can effectively inductively heat the welded parts of the semicircular tubes. When the induction heater is energized, it can synchronously heat the welded parts of multiple semicircular tubes within the same group, ensuring both temperature consistency and synchronous heating of each weld joint, guaranteeing uniform heating temperature and consistent brazing quality. This eliminates quality issues such as localized incomplete welds and overheating that can occur with automatic flame brazing due to excessive temperature differences. It significantly improves the first-pass brazing success rate of semi-circular tubes in irregularly shaped heat exchangers, reducing the frequency of post-weld repairs, decreasing the number of repair operators, increasing production efficiency, and lowering production costs. Furthermore, induction brazing uses electric heating, which produces no noise or smoke during the heating process. This eliminates the high noise, light pollution, and dust pollution associated with flame brazing, making it a harmless, environmentally friendly, and "zero-carbon" brazing method for operators. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of a structure of an embodiment of the heat exchanger provided by the present invention;

[0028] Figure 2 This is a schematic diagram of a heat exchanger brazed using a heated fire bar in the prior art.

[0029] Figure 3 This is a schematic diagram of the brazing of a heat exchanger using an automated flame brazing process in the prior art;

[0030] Figure 4 This is a schematic diagram of an embodiment of the automatic flameless brazing method for heat exchangers provided by the present invention.

[0031] Figure 5 This is a schematic diagram of an embodiment of induction brazing using the flameless automatic brazing method for heat exchangers provided by the present invention.

[0032] Figure 6 This is a schematic diagram of the structure of an induction heater in an embodiment of induction brazing using the flameless automatic brazing method for heat exchangers provided by the present invention.

[0033] Figure 7 This is a schematic diagram of another embodiment of induction brazing using the flameless automatic brazing method for heat exchangers provided by the present invention.

[0034] Figure 8 This is a schematic diagram of another embodiment of induction brazing using the flameless automatic brazing method for heat exchangers provided by the present invention.

[0035] Explanation of icon numbers:

[0036] 100. Heat exchanger; 10. U-shaped heat exchange tube; 20. Semi-circular tube; 30. Fin; 40. Side plate;

[0037] 200, Induction heater; 210, Induction heating coil; 220, Inductor connector; 200a, First induction heater; 200b, Second induction heater; 200c, Third induction heater;

[0038] 310. Convex burner assembly; 320. Concave burner assembly.

[0039] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0042] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0043] like Figure 1 As shown, the heat exchanger 100 includes multiple U-shaped heat exchange tubes 10 and multiple semi-circular tubes 20. The ends of the multiple U-shaped heat exchange tubes 10 face the same end of the heat exchanger 100 and are connected through the semi-circular tubes 20, thus forming a tortuous heat exchange pipeline. Optionally, the heat exchanger 100 also includes multiple fins 30, which are sleeved around the multiple U-shaped heat exchange tubes 10 to increase the heat exchange area and improve the heat exchange efficiency. In addition, to ensure the installation stability of the fins 30, the heat exchanger 100 also includes a side plate 40 disposed on the outermost side of the multiple fins 30. For the irregularly shaped heat exchanger 100, the shapes of its fins 30 and side plates 40 are usually irregular (e.g., similar to U-shape or V-shape). To adapt to the irregular structure of the heat exchanger 100, the multiple U-shaped heat exchange tubes 10 and semi-circular tubes 20 also exhibit an irregular irregular structural arrangement.

[0044] Currently, the irregularly shaped heat exchanger 100 typically employs an automated flame brazing process to braze the semi-circular tube 20 and the U-shaped heat exchange tube 10. For example... Figure 2 and Figure 3 As shown, in existing technologies, the brazing heating elements are generally designed as arc-shaped or contour-following heating elements according to the shape and size of the semi-circular tube 20 to be welded, and are configured as convex element assembly 310 and concave element assembly 320. During brazing, the convex element assembly 310 and concave element assembly 320 are arranged on both sides of the heat exchanger 100 to heat the weld points of the semi-circular tube 20. However, in production practice, it has been found that using the above-mentioned automatic flame brazing process, the first-pass brazing qualification rate of the heat exchanger 100 is low, the subsequent repair welding rate is high (the repair welding rate is usually higher than 60%), and the quality fluctuates greatly.

[0045] In-depth research has revealed that traditional flame brazing processes generally consist of two parts: a combustible gas (liquefied petroleum gas - LPG / natural gas) and an oxidizing gas (oxygen - O2). The main components of LPG are propane (C3H8), butane (C4H10), and certain amounts of hydrocarbons such as propylene (C3H6) and butene (C4H8). Furthermore, to increase the wettability of the liquid solder and prevent oxidation of the copper tube surface, a gaseous flux (whose main component is trimethyl borate, with a required content of 55-65%) is added to the O2-LPG / natural gas mixture. The combustion temperature of this three-gas mixture can reach 2400 degrees Celsius. Depending on the oxygen-to-LPG mixing ratio, the O2-LPG gas flame can exhibit three different flame properties: an oxidizing flame, a neutral flame, and a reducing flame (also known as a carburizing flame).

[0046] 1. Neutral flame: The volume ratio of O2 to LPG is 3.5;

[0047] 2. Reducing flame: A reducing flame is formed when the volume ratio of O2 to LPG is less than 3.5;

[0048] 3. Oxidizing flame: When the volume ratio of O2 to LPG is greater than 3.5, it is an oxidizing flame.

[0049] When brazing irregularly shaped heat exchangers, a neutral flame is generally used. The requirements for the flame heating position are usually as follows:

[0050] 1. During preheating: The outer flame is used to heat the workpiece within a range of 20mm to 40mm from the welding nozzle;

[0051] 2. During welding: The flame heating position is about 5mm above the top of the flaming mouth. Use the outer flame 3-5mm away from the white core of the flame to heat the weld by swinging it back and forth.

[0052] like Figure 3 As shown, when using flame brazing, irregularly shaped heat exchangers have the following problems due to the irregular distribution of semicircular tubes, with some semicircular tubes being obliquely distributed:

[0053] 1) Some weld joints are blocked by other semi-circular tubes, and the heating flame cannot be heated with a 3-5mm outer flame with a white core as required above. The temperature at the blocked weld joints cannot reach the optimal brazing temperature, resulting in uneven brazing heating.

[0054] 2) Some weld points are located in the center of the heat exchanger. Due to structural limitations, the ideal heating flame position cannot directly reach the weld point, resulting in insufficient local temperature at the weld point and problems such as incomplete welding.

[0055] 3) The semi-circular tube weld points near the outer side of the two devices are unobstructed, and the semi-circular tubes and weld points are in direct contact with the flame. The flame temperature is high, and the temperature of the semi-circular tubes is high during brazing heating.

[0056] Due to the aforementioned issues with automated flame brazing, irregularly shaped heat exchangers experience problems during flame heating: high brazing temperatures on the outer semicircular tubes and low brazing temperatures on the central and obscured semicircular tubes, resulting in significant temperature differences between the inside and outside, leading to issues such as incomplete welds and overheating. Therefore, in actual mass production, automated flame brazing of irregularly shaped heat exchangers typically requires manual re-welding after each initial weld, resulting in a low first-pass yield and a high re-welding rate. Furthermore, automated flame brazing generates noise and light pollution, which is detrimental to the health of operators; it also produces dust and harmful gases (such as CO2 and SO2), polluting the environment.

[0057] Based on this, the present invention proposes a flameless automatic brazing method for heat exchangers, which improves the first-pass brazing qualification rate of irregularly shaped heat exchangers, reduces the subsequent repair welding rate, improves production efficiency, and reduces production costs; and can eliminate the high noise, light pollution and dust pollution generated by flame brazing, making it a green, environmentally friendly and "zero-carbon" emission brazing method.

[0058] Please see Figure 4 and Figure 5 In one embodiment of the present invention, the automatic brazing method for the heat exchanger 100 without flame includes the following steps:

[0059] S1. Divide the multiple semi-circular tubes 20 to be welded located at the same end of the heat exchanger 100 into multiple groups of tubes to be welded, and the semi-circular tubes to be welded in the same group of tubes to be welded have the same welding parameter requirements.

[0060] S2. Provide an induction heater 200 adapted to the number and shape of the tube groups to be welded. The induction heater 200 has a contouring area, and the contouring area of ​​each induction heater 200 is arranged one-to-one around the periphery of each group of tube groups to be welded.

[0061] S3. Power on the induction heater 200 to perform induction brazing on the parts of the semi-circular tubes 20 in the tube group to be welded.

[0062] The brazing method of the present invention is applicable to the flameless automatic induction brazing of the semi-circular tube 20 of copper, aluminum, steel and other metal heat exchangers 100. It is applicable to the production and manufacture of heat exchangers 100 with regular and irregular shapes, and is particularly well applied to the brazing of the semi-circular tube 20 of irregularly shaped heat exchangers 100. The following description mainly focuses on the brazing of the semi-circular tube 20 of irregularly shaped heat exchangers 100.

[0063] The ends of multiple U-shaped heat exchange tubes 10 of the irregular heat exchanger 100 extend from the end face of the side plate 40 of the heat exchanger 100. Any two ends of the U-shaped heat exchange tubes 10 are connected and communicate with each other via U-shaped semicircular tubes 20. Typically, the multiple semicircular tubes 20 located at the same end of the heat exchanger 100 may have different specifications, such as different shapes, sizes, wall thicknesses, and materials. Correspondingly, the welding parameter requirements for the welding parts of the multiple semicircular tubes 20 will also differ. To ensure the uniformity of induction brazing, in step S1, the multiple semicircular tubes 20 to be welded are first grouped according to the welding parameter requirements of the welding parts of the semicircular tubes 20, thus dividing them into multiple groups of tubes to be welded. The welding parameter requirements (such as the required heating temperature and heating time) for the welding parts of each semicircular tube 20 within each group of tubes to be welded are consistent. This ensures that during subsequent induction heating, the welding parts of each semicircular tube 20 located within the same contouring area have the same welding parameters, thereby guaranteeing welding uniformity. Typically, the welding area of ​​the semi-circular tube 20 to be welded is provided with a welding ring. The required welding parameters can be determined based on the specifications of the welding ring (such as shape and size). For example, when the specifications of the welding ring are the same, the required welding parameters are also the same.

[0064] Multiple semicircular tubes 20 to be welded are divided into multiple groups, such as two, three, or more groups, depending on the actual arrangement of the semicircular tubes 20. In step S2, induction heaters 200 adapted to the number of groups are provided. For example, two induction heaters 200 are provided when there are two groups; three induction heaters 200 are provided when there are three groups. The induction heaters 200 have a contoured area adapted to the outer periphery of the group, so that multiple semicircular tubes 20 of the group can be placed in the contoured area, and the inner edge of the contoured area can be as close as possible to the welding part of the semicircular tube 20, so as to ensure that the induction heaters 200 can effectively induction heat the welding part of the semicircular tube 20. In step S3, after the induction heaters 200 are energized, induction brazing can be performed simultaneously on the welding parts of multiple semicircular tubes 20 within the same group by one induction heater 200. Induction brazing is primarily based on the phenomenon of electromagnetic induction. When a conductive workpiece (such as the U-shaped heat exchange tube 10 and the semi-circular tube 20) is placed in a changing electromagnetic field, induced currents (eddy currents) are generated inside the workpiece. These induced currents generate resistance heat as they flow inside the workpiece, thereby heating the workpiece to the required brazing temperature. By controlling the frequency and intensity of the induced current, induction brazing can achieve precise heating of the workpiece, either locally or entirely.

[0065] It is worth noting that in step S3, multiple sets of pipe assemblies to be welded can be brazed in stages or simultaneously, depending on the actual situation. Taking two sets of pipe assemblies as an example, if the two sets are close together and simultaneous heating would cause interference, one set can be heated first using an induction heater 200, and then the other set can be heated using another induction heater 200. If the two sets are far apart and simultaneous heating would not interfere with each other, they can optionally be brazed simultaneously, which can improve brazing efficiency.

[0066] The technical solution of this invention first groups multiple semicircular tubes 20 to be welded according to their specifications, shape, and size, thus dividing them into multiple groups of tubes to be welded. The specifications, shape, and size of each semicircular tube 20 within each group are consistent, ensuring that the structure, shape, and size of the weld joints of each semicircular tube 20 within the same group are essentially the same. Then, by providing an induction heater 200 adapted to the number and shape of the tube groups to be welded, multiple semicircular tubes 20 within the group can be placed within the contouring area of ​​the induction heater 200. The welding parameters of the welded parts of each semicircular tube within the same contouring area are the same, ensuring that the induction heater 200 can effectively inductively heat the welded parts of the semicircular tubes 20. When the induction heater 200 is energized, it can synchronously heat the welded parts of multiple semicircular tubes 20 within the same group, ensuring both temperature consistency and synchronous heating of each weld joint, guaranteeing uniform heating temperature for each weld joint and consistent brazing quality. This eliminates the quality problems associated with automatic flame brazing, such as localized incomplete welds and overheating due to excessive temperature differences. It significantly improves the first-pass brazing qualification rate of 100mm semi-circular tubes and 20mm diameter tubes in irregularly shaped heat exchangers, reducing the frequency of post-weld repairs, decreasing the number of repair operators, increasing production efficiency, and lowering production costs. Furthermore, induction brazing uses electric heating, which produces no noise or smoke during the heating process. This eliminates the high noise, light pollution, and dust pollution caused by flame brazing, making it a harmless, environmentally friendly, and "zero-carbon" brazing method for operators.

[0067] like Figure 5 and Figure 6 As shown, in one embodiment, the induction heater 200 includes an induction heating coil 210 for enclosing the contoured area. The semicircular tubes 20 in the tube assembly to be welded are provided with welding rings at the welding locations. The outermost radial edge of the welding ring of each semicircular tube 20 located in the induction heating coil 210 is kept at a preset distance from the inner effective coil of the induction heating coil 210.

[0068] In this embodiment, the induction heater 200 includes an induction heating coil 210. The flexible deformation of the induction heating coil 210 allows for the easy construction of a contoured region that matches the outer periphery of the tube assembly to be welded, reducing the manufacturing difficulty of the induction heater 200. The induction heating coil 210 can be an irregularly shaped ring structure with an opening. The interior of the induction coil forms a contoured region for accommodating the tube assembly to be welded, and both ends of the induction heating coil 210 form inductor connectors 220 for connecting an external power supply circuit. The induction heating coil 210 can be configured as a single-turn or multi-turn coil as needed. When the induction heating coil 210 has multiple turns, the multi-turn coil can be arranged axially or radially along the heat exchange tube, provided space permits. An induction heating coil 210 surrounds a group of semicircular tubes 20. The outer periphery of the semicircular tubes 20 within the same group is only partially wrapped by the induction heating coil. The inner effective coil of the induction heating coil 210 refers to the arc-shaped section of the coil whose inner edge can wrap around the semicircular tube 20, effectively heating the weld ring of the semicircular tube 20. To prevent short circuits and fires during induction brazing, a predetermined distance should be maintained between the outermost radial edge of the weld ring of each semicircular tube 20 within the induction heating coil 210 and the inner effective coil of the induction heating coil 210. Optionally, this predetermined distance should be no less than 1 mm to ensure brazing safety. For example, the predetermined distance between the inner effective coil of the induction heating coil 210 and the outermost radial edge of the weld ring of the semicircular tube 20 can be 1 mm, 1.5 mm, 2 mm, etc. Considering the effectiveness of induction brazing heating, the preset distance should not be too large to ensure that the induction heating coil 210 can effectively induction heat the internal semi-circular tube 20.

[0069] The contour induction heater 200 is designed according to the following principles: the "proximity heating principle" in induction heating, the structure of the induction heating coil 210 that can directly induction heat each part to be welded (so that the effective coil of the induction heating coil 210 can "wrap" each part to be welded), and the principle that the distance between the outer side of the part to be welded and the inner effective coil of the induction heating coil 210 is consistent. This ensures that each part to be welded can be heated and heated at the same time during induction heating, and ensures the consistency and uniformity of the heating temperature.

[0070] To further ensure the consistency of induction brazing quality, in one embodiment, the radial outermost edge of the weld ring of the plurality of semicircular tubes 20 located within the induction heating coil 210 is kept consistent with the spacing between the inner effective coil of the induction heating coil 210, or a preset tolerance exists.

[0071] Ideally, the distance between the outermost radial edge of the weld rings of the multiple semicircular tubes 20 located within the induction heating coil 210 and the inner effective coil of the induction heating coil 210 should be consistent. This ensures that the effective coil of the induction heating coil 210 can "wrap" each weld ring, and that the distance between the induction heating coil 210 and the outermost radial edge of each weld ring is consistent. This guarantees that all weld rings can be heated simultaneously during induction heating, ensuring consistent and uniform heating temperatures. In actual production, it is difficult to guarantee that the distance between the induction heating coil 210 and the outermost radial edge of each weld ring is absolutely consistent. As long as it is within a preset tolerance range, it can be considered to be approximately consistent. For example, a reference distance H can be used, and a preset distance within a tolerance range of H ± 1 mm can be considered approximately consistent.

[0072] To further improve induction brazing efficiency, in one embodiment, the induction heater 200 includes multiple turns of the induction heating coil 210. For example, the induction heater 200 may include two, three, or more turns of the induction heating coil 210, thereby increasing the induction heating area and improving the induction brazing efficiency.

[0073] Considering that the multiple semicircular tubes 20 on the end face of the heat exchanger 100 are usually arranged in a relatively compact manner and the distance between two adjacent semicircular tubes 20 is small, it is usually difficult to accommodate the multi-turn induction heating coil 210 arranged radially. In order to make it suitable for multi-turn induction coils, the multi-turn induction heating coil 210 can optionally be arranged along the axial direction of the semicircular tube 20 to heat the semicircular tube 20.

[0074] In one embodiment, the step of energizing the induction heater 200 to perform induction brazing on the parts of the semi-circular tubes 20 within the tube assembly to be welded includes:

[0075] The induction heating coil 210 is kept in a fixed position relative to the semi-circular tube 20 to fix and heat the welding ring to be welded on the semi-circular tube 20.

[0076] Alternatively, the induction heating coil 210 may oscillate relative to the semicircular tube 20 within a preset range to oscillate and heat the welding ring to be welded on the semicircular tube 20.

[0077] In this embodiment, the induction heating coil 210 can heat the semicircular tube 20 in two ways. For example, during the induction heating process, the induction heating coil 210 and the semicircular tube 20 can remain relatively stationary, that is, the induction heating coil 210 can maintain a fixed position relative to the semicircular tube 20 to fix the welding ring to be welded on the semicircular tube 20. In this way, it can be ensured that the distance between the outermost of the welding rings to be welded on the multiple semicircular tubes 20 located within the induction heating coil 210 and the inner effective coil of the induction heating coil 210 is basically maintained throughout the entire induction heating process, thereby ensuring that each welding point can be heated and heated simultaneously during induction heating, ensuring the consistency and uniformity of the heating temperature. Alternatively, during the induction heating process, the induction heating coil 210 can be oscillated relative to the semicircular tube 20 within a preset amplitude to oscillate and heat the welding ring to be welded on the semicircular tube 20. In this way, the oscillation of the induction heating coil 210 can increase the induction heating range. The induction heating coil 210 can oscillate radially or axially along the semicircular tube 20.

[0078] In one embodiment, during the step of energizing the induction heater 200 to perform induction brazing on the semicircular tubes 20 within the tube assembly to be welded, the heat exchanger 100 remains stationary. For example, before induction brazing, the heat exchanger 100 can be transported to the welding station via a conveyor belt, turntable mechanism, etc. During induction brazing, the heat exchanger 100 remains stationary at the welding station to ensure that the induction heater 200 can effectively heat the weld rings of the semicircular tubes 20 within the heat exchanger 100.

[0079] In one embodiment, in the step of energizing the induction heater 200 to perform induction brazing on the parts of the semi-circular tubes 20 in the tube assembly to be welded, the induction heater 200 is connected to a high-frequency induction heating power supply, the output frequency of which is 10-100KHz.

[0080] In this embodiment, the induction heater 200 employs a high-frequency induction heating power supply, enabling high-frequency induction heating and improving induction heating efficiency. The induction heating device uses current as its energy source. The workpiece to be welded is placed in the induction heating coil 210, and heating is achieved by utilizing the induced current generated in the conductor under the action of a high-frequency magnetic field (eddy current loss, and hysteresis loss caused by the magnetic field within the conductor, causing the conductor to heat up). Optionally, the output frequency of the high-frequency induction heating power supply is 10–100 kHz. For example, the output frequency can be 10 kHz, 20 kHz, 30 kHz, 40 kHz, 50 kHz, 60 kHz, 70 kHz, 80 kHz, 90 kHz, 100 kHz, etc.

[0081] Based on the above embodiments, in one embodiment, before the step of energizing the induction heater 200 to perform induction brazing on the welding portions corresponding to each semi-circular tube 20 in the welding assembly, the following steps are further included:

[0082] Based on the arrangement of the multiple sets of tubes to be welded, the heating sequence of the multiple induction heaters 200 is determined so that the multiple sets of tubes to be welded are induction brazed stepwise or synchronously.

[0083] During brazing, the appropriate heating method can be selected based on the arrangement of multiple sets of pipes to be brazed. For example, when multiple sets of pipes are far apart and simultaneous heating does not cause interference, simultaneous induction brazing of multiple sets can be performed to improve brazing efficiency. When multiple sets of pipes are close together and simultaneous heating causes interference, step-by-step induction brazing of multiple sets can be performed to ensure brazing quality.

[0084] Furthermore, the step of determining the heating sequence of the multiple induction heaters 200 based on the arrangement of the multiple groups of tubes to be welded, so as to enable the multiple groups of tubes to be welded to undergo stepwise induction brazing or synchronous induction brazing, includes:

[0085] When the distance between two adjacent groups of pipes to be welded is less than the preset safety distance, the two adjacent induction heaters 200 are controlled to heat in stages in sequence so that the two adjacent groups of pipes to be welded are induction brazed step by step.

[0086] When the distance between two adjacent sets of pipe groups to be welded is greater than or equal to a preset safety distance, the two adjacent induction heaters 200 are controlled to heat synchronously so that the two adjacent sets of pipe groups to be welded are synchronously induction brazed.

[0087] In this embodiment, the preset safety distance can be set according to actual conditions to ensure that there is no interference when two adjacent groups of pipes to be welded are simultaneously induction heated. Taking two groups of pipes to be welded as an example, when the distance between the two groups of pipes to be welded is close, less than the preset safety distance, the induction heaters 200 corresponding to the two groups of pipes to be welded can be heated in segments in sequence. That is, after welding multiple semi-circular tubes 20 of one group of pipes to be welded by one induction heater 200, the other induction heater 200 is used to weld multiple semi-circular tubes 20 of the other group of pipes to be welded. In this way, interference can be avoided when the two induction heaters 200 work at the same time, ensuring welding quality. When the distance between the two groups of pipes to be welded is far, greater than or equal to the preset safety distance, the induction heaters 200 corresponding to the two groups of pipes to be welded can be heated synchronously, so that each semi-circular tube 20 in the two groups of pipes to be welded can be heated synchronously for induction brazing, which can significantly improve brazing efficiency. For example, when there are three sets of pipe assemblies to be welded, the induction heaters 200 corresponding to the three sets of pipe assemblies can be selected to heat them in stages according to a specific sequence, thereby dividing the three sets of pipe assemblies to be welded into three steps for induction brazing. Alternatively, the middle set of pipe assemblies to be welded can be induction brazed first, and after welding is completed, the two sets of pipe assemblies to be welded on both sides can be induction brazed first; or, the two sets of pipe assemblies to be welded on both sides can be induction brazed first, and then the middle set of pipe assemblies to be welded can be induction brazed.

[0088] In the step of dividing the multiple semi-circular tubes 20 to be welded located at the same end of the heat exchanger 100 into multiple groups of tubes to be welded, the arrangement of the multiple groups of tubes to be welded can be varied, including but not limited to the following:

[0089] For example, such as Figure 5 As shown, in one embodiment, multiple semi-circular tubes 20 to be welded are divided into two groups of tubes to be welded, and the two groups of tubes to be welded are symmetrically arranged on both sides of the width centerline of the heat exchanger 100. Accordingly, each tube group to be welded is equipped with an induction heater 200. The induction heating coils 210 of the two contour induction heaters 200 are respectively arranged around the periphery of the corresponding tube group to be welded, so that all welding points are placed inside the induction heating coils 210 for direct heating and brazing, ensuring the quality of the brazing weld. To improve the efficiency of induction heating, the induction heating coils 210 can adopt a two-turn or multi-turn structure.

[0090] For example, such as Figure 7As shown, in another embodiment, the plurality of semi-circular tubes 20 to be welded are divided into three groups of tubes to be welded: a first group, a second group, and a third group. The first group is located at the middle of the width direction of the heat exchanger 100, and the second and third groups are arranged on both sides of the first group along the width direction of the heat exchanger 100. Correspondingly, each group is equipped with an induction heater 200: a first induction heater 200a, a second induction heater 200b, and a third induction heater 200c. The induction heating coils 210 of the three contour induction heaters 200 are respectively arranged around the periphery of the corresponding group of tubes to be welded, so that all weld points are placed inside the induction heating coils 210 for direct heating and brazing, ensuring the quality of the weld. To improve the efficiency of induction heating, the induction heating coils 210 can adopt a two-turn or multi-turn structure.

[0091] For example, such as Figure 8 As shown, in another embodiment, the plurality of semi-circular tubes 20 to be welded are divided into three groups of tubes to be welded: a first group, a second group, and a third group. The first group is located at the middle of the width direction of the heat exchanger 100. The second group includes two sub-groups of tubes to be welded located on both sides of the first group along the width direction of the heat exchanger 100. The third group includes two sub-groups of tubes to be welded located on both sides of the second group along the width direction of the heat exchanger 100. Accordingly, each group of tubes to be welded is equipped with an induction heater 200, namely a first induction heater 200a, a second induction heater 200b, and a third induction heater 200c. The second induction heater 200b includes two sub-modeling induction heating areas located on both sides of the first induction heater 200a, and the third induction heater 200c includes two sub-modeling induction heating areas located on both sides of the second induction heater 200b. The brazing process involves induction brazing of the semi-circular tube 20 of the heat exchanger 100 in three steps. During brazing, all weld points are placed inside the induction heating coil 210 for direct heating to ensure weld quality. To improve induction heating efficiency, this scheme can employ a two-turn or multi-turn structure.

[0092] like Figure 1As shown, the present invention also proposes a heat exchanger 100, which includes a plurality of U-shaped heat exchange tubes 10 and a plurality of semi-circular tubes 20. The U-shaped heat exchange tubes 10 and the semi-circular tubes 20 are welded and fixed using the above-described flameless automatic brazing method for the heat exchanger 100. The flameless automatic brazing method for the heat exchanger 100 is described in the above embodiments. Since the heat exchanger 100 adopts all the technical solutions of all the above embodiments, it possesses at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be elaborated further here.

[0093] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A flameless automatic brazing method for heat exchangers, characterized in that, Includes the following steps: Multiple semicircular tubes to be welded located at the same end of the heat exchanger are divided into multiple groups of tubes to be welded. The semicircular tubes to be welded in the same group of tubes to be welded have the same welding parameter requirements. An induction heater is provided that is adapted to the number and shape of the tube groups to be welded. The induction heater has a contouring area, and the contouring area of ​​each induction heater is arranged one-to-one around the periphery of each group of tube groups to be welded. The induction heater is energized to perform induction brazing on the parts of the semi-circular tubes in the tube group to be welded.

2. The automatic flameless brazing method for heat exchangers as described in claim 1, characterized in that, The induction heater includes an induction heating coil for enclosing the contoured area. The semi-circular tubes in the welding assembly are provided with welding rings at the welding locations. The outermost radial edge of the welding ring of each semi-circular tube located within the induction heating coil maintains a preset distance from the inner effective coil of the induction heating coil.

3. The automatic flameless brazing method for heat exchangers as described in claim 2, characterized in that, The radial outermost edge of the welding ring of the multiple semi-circular tubes located in the induction heating coil is kept consistent with the spacing between the inner effective coil of the induction heating coil, or there is a preset tolerance.

4. The automatic flameless brazing method for heat exchangers as described in claim 2, characterized in that, The induction heater includes multiple turns of the induction heating coil, which are arranged along the axial direction of the semicircular tube to heat the semicircular tube.

5. The automatic flameless brazing method for heat exchangers as described in claim 2, characterized in that, The step of energizing the induction heater to perform induction brazing on the welding parts of each semi-circular tube in the tube assembly includes: The induction heating coil is kept in a fixed position relative to the semi-circular tube to fix and heat the welding ring to be welded on the semi-circular tube. Alternatively, the induction heating coil may oscillate relative to the semi-circular tube within a preset range to oscillate and heat the weld ring to be welded on the semi-circular tube.

6. The automatic flameless brazing method for heat exchangers as described in claim 1, characterized in that, In the step of energizing the induction heater to perform induction brazing on the parts of the semi-circular tubes in the tube assembly to be welded, the induction heater is connected to a high-frequency induction heating power supply, the output frequency of which is 10-100KHz.

7. The automatic flameless brazing method for heat exchangers as described in any one of claims 1 to 6, characterized in that, Before the step of energizing the induction heater to perform induction brazing on the welding parts corresponding to each semi-circular tube in the welding assembly, the following steps are also included: Based on the arrangement of the multiple sets of tubes to be welded, the heating sequence of the multiple induction heaters is determined so that the multiple sets of tubes to be welded are induction brazed stepwise or simultaneously.

8. The automatic flameless brazing method for heat exchangers as described in claim 7, characterized in that, The step of determining the heating sequence of multiple induction heaters based on the arrangement of multiple groups of pipes to be welded, so as to enable the multiple groups of pipes to be welded to undergo stepwise or simultaneous induction brazing, includes: When the distance between two adjacent groups of pipes to be welded is less than the preset safety distance, the two adjacent induction heaters are controlled to heat in stages in sequence so that the two adjacent groups of pipes to be welded are induction brazed step by step. When the distance between two adjacent sets of pipe groups to be welded is greater than or equal to a preset safety distance, the two adjacent induction heaters are controlled to heat synchronously so that the two adjacent sets of pipe groups to be welded are synchronously induction brazed.

9. The automatic flameless brazing method for heat exchangers as described in claim 7, characterized in that, In the step of dividing the multiple semi-circular tubes to be welded located at the same end of the heat exchanger into multiple groups of tubes to be welded, the arrangement of the multiple groups of tubes to be welded includes: Multiple semi-circular tubes to be welded are divided into two groups of tubes to be welded, and the two groups of tubes to be welded are symmetrically arranged on both sides of the width centerline of the heat exchanger. Alternatively, the multiple semi-circular tubes to be welded are divided into three groups of tubes to be welded, namely the first group of tubes to be welded, the second group of tubes to be welded, and the third group of tubes to be welded. The first group of tubes to be welded is located in the middle of the width direction of the heat exchanger, and the second group of tubes to be welded and the third group of tubes to be welded are respectively arranged on both sides of the first group of tubes to be welded along the width direction of the heat exchanger. Alternatively, the multiple semi-circular tubes to be welded are divided into three groups of tubes to be welded, namely the first group of tubes to be welded, the second group of tubes to be welded, and the third group of tubes to be welded. The first group of tubes to be welded is located in the middle of the width direction of the heat exchanger. The second group of tubes to be welded includes two sub-groups of tubes to be welded located on both sides of the first group of tubes to be welded along the width direction of the heat exchanger. The third group of tubes to be welded includes two sub-groups of tubes to be welded located on both sides of the second group of tubes to be welded along the width direction of the heat exchanger.

10. A heat exchanger, characterized in that, The heat exchanger includes a plurality of U-shaped heat exchange tubes and a plurality of semi-circular tubes, wherein the U-shaped heat exchange tubes and the semi-circular tubes are welded and fixed using the heat exchanger flameless automatic brazing method as described in any one of claims 1 to 9.

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