Micro-channel heat exchanger core assembly and method of manufacturing the same

Abstract

The application discloses a micro-channel heat exchanger core assembly and a manufacturing method thereof. The heat exchanger core assembly comprises a plurality of sub-cores, the plurality of sub-cores are stacked, and three-point waveforms are used to weld two-by-two stacking contact positions of the sub-cores, thereby forming a main structure of the heat exchanger core assembly. Through the three-point waveform electron beam welding, on the one hand, the welding width can be reduced, and the deformation influence of large heat input on the plate can be prevented; on the other hand, the three-point waveforms play the roles of preheating in the front part, welding in the middle part and slow cooling in the rear part, the molten pool stability in the welding process is maintained, the electron beam nail tip defects at the root of the electron beam weld can be effectively controlled while the welding seam with extremely narrow width and large depth is obtained.

Description

Technical Field

[0001] This invention belongs to the field of heat exchanger manufacturing technology, specifically relating to a microchannel heat exchanger core assembly and its manufacturing method. Background Technology

[0002] Microchannel heat exchangers, represented by printed circuit heat exchangers (PCHEs), possess a series of significant advantages, including large heat transfer area per unit volume, high heat transfer coefficient, strong temperature and pressure resistance, high reliability, and the ability to simultaneously exchange heat with multiple media. They show promising application prospects in fields such as ship propulsion, marine engineering, hydrogen energy, nuclear energy, and concentrated solar power. Microchannel heat exchangers mainly consist of a core and tube box. The core is the core and the most challenging aspect of heat exchanger manufacturing, directly affecting the overall safety and reliability of the heat exchanger. Common fusion welding methods (such as TIG welding and MIG welding) are difficult to apply to the welding points between the plates, while brazing methods are prone to the risk of filler metal overflowing and clogging the mesh. Currently, only vacuum diffusion welding can achieve a good connection between the core plates.

[0003] However, due to limitations in the manufacturing capabilities of diffusion welding equipment and the development level of diffusion welding technology both domestically and internationally, large microchannel cores cannot be diffused and welded in a single process. They must be divided into several sub-cores for diffusion welding, and then the sub-cores are joined together. Currently, the joining of sub-cores both domestically and internationally mostly uses traditional fusion welding methods such as TIG welding and MIG welding. These welding methods have drawbacks: large heat input during welding, which can easily lead to significant welding deformation and residual stress in the core. Furthermore, these welding methods require machining a welding bevel at a certain angle before welding, increasing the difficulty of pre-welding preparation and the amount of deposited metal during welding, thus increasing the core production cycle. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a microchannel heat exchanger core assembly and its manufacturing method, solving the problems of large heat input, the need to process a welding bevel at a certain angle before welding, the difficulty of pre-welding preparation, and the large amount of deposited metal during the welding process in existing welding methods.

[0005] The objective of this invention is achieved through the following technical solution: a microchannel heat exchanger core assembly comprising several sub-cores.

[0006] Several sub-cores are stacked to form the core assembly of a microchannel heat exchanger, and the sub-cores are connected by welding.

[0007] Preferably, each sub-core includes a plurality of first heat exchange plate layers and second heat exchange plate layers, which are stacked alternately to form a cuboid-shaped sub-core. Each of the first and second heat exchange plate layers has a heat exchange channel, and the heat exchange channels of the first and second heat exchange plate layers have different directions.

[0008] Preferably, a transition layer 2 is provided on the connecting surface of the sub-core, and two adjacent sub-cores are welded together through the transition layer 2.

[0009] Furthermore, as a preferred embodiment, a positioning structure is provided between the transition layers 2 for auxiliary positioning when the sub-cores are stacked.

[0010] Furthermore, as a preferred option, the thickness of the transition layer 2 is 5mm-10mm.

[0011] Furthermore, as a preferred embodiment, the positioning structure includes a positioning pin hole and a positioning pin post, with the positioning pin post extending into the positioning pin hole to form a positioning.

[0012] In addition to providing a microchannel heat exchanger core assembly, the present invention further provides a method for manufacturing the above-mentioned core assembly, specifically including the following steps:

[0013] Step 1: Stack several sub-cores sequentially on the turntable inside the vacuum chamber of the electron beam welding machine;

[0014] Step 2: Evacuate the vacuum chamber to achieve the preset vacuum level;

[0015] Step 3: Turn on the electron beam welding gun and use a three-point waveform to weld the two stacked contact points of the sub-cores;

[0016] Step 4: After welding, wait for the core assembly to cool to below the first preset temperature, then remove the vacuum from the vacuum chamber, take out the core assembly, and complete the welding.

[0017] Preferably, in step 3, the specific method for welding the two-by-two stacked contact positions of the sub-cores using a three-point waveform is as follows:

[0018] Step 3.1: Use a three-point waveform to intermittently spot weld the adjacent sub-cores at their paired stacked contact points;

[0019] Step 3.2: Use a three-point waveform to perform full weld seam welding on the two-by-two stacked contact points of the spot-welded sub-cores.

[0020] When performing intermittent spot welding, welding is carried out at equal intervals, with the interval between two adjacent intermittent welds being between 180mm and 220mm.

[0021] Preferably, in step 4, the first preset temperature is 80℃-120℃.

[0022] Furthermore, as a preferred embodiment, in step 3.1, the sequence of intermittent spot welding is as follows: first, intermittently spot weld the two longer welds between two adjacent sub-cores, and then intermittently spot weld the two shorter welds between two adjacent sub-cores.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] This invention provides a microchannel heat exchanger core assembly and its manufacturing method. Precision welding between microchannel sub-cores is achieved through vacuum electron beam welding, resulting in a weld with a large aspect ratio in a single operation. By employing a three-point waveform process, the electron beam penetration capability is increased, thereby achieving a large aspect ratio, measured at 15:1 by metallographic imaging. This achieves the required strength for connection between sub-cores, resulting in a welded joint with excellent quality, significantly reducing welding deformation and residual stress, minimizing the adverse effects of welding on the core, and effectively improving the safety and reliability of the microchannel heat exchanger core.

[0025] This invention employs a three-point waveform electron beam welding method. On one hand, it reduces the weld width, preventing the deformation of the plate caused by excessive heat input. On the other hand, the three-point waveform serves to preheat the weld, weld in the middle, and slow cool it at the end, maintaining a stable molten pool during the welding process. This achieves extremely narrow weld widths and deep welds while effectively controlling electron beam stud defects at the weld root. The intermittent sealing welding positions and sequences enable deformation control during the symmetrical welding process of large structures, avoiding significant deformation of the core plate. This invention provides a manufacturing solution for the design of novel heat exchanger cores, ensuring the quality and manufacturing precision of the heat exchanger core welding. Attached Figure Description

[0026] Figure 1 This is a three-dimensional structural diagram of a transition layer disposed on the sub-core in an embodiment of the present invention;

[0027] Figure 2 This is an assembly diagram of the core assembly during welding in an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the sub-core being welded together in an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the three-point electron beam welding waveform in an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of the three-point electron beam welding waveform during welding in an embodiment of the present invention;

[0031] Figure 6 This is a schematic diagram of the regional structure of electron beam spot welding of the transition layer according to an embodiment of the present invention;

[0032] Figure 7 This is a schematic diagram of the regional structure during electron beam welding of the transition layer according to an embodiment of the present invention.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1 is the sub-core; 11 is the first heat exchanger layer; 12 is the second heat exchanger layer; 2 is the transition layer; 3 is the positioning pin hole; 4 is the positioning pin post; 5 is the electron beam welding gun; 6 is the turntable. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0036] The present invention provides a microchannel heat exchanger core assembly, comprising a plurality of sub-cores 1.

[0037] Several sub-cores 1 are stacked to form a microchannel heat exchanger core assembly, and the sub-cores 1 are connected by welding.

[0038] like Figure 1 As shown, in one embodiment of the present invention, each sub-core 1 includes a plurality of first heat exchange plate layers 11 and second heat exchange plate layers 12, which are alternately stacked to form a cuboid-shaped sub-core 1. Each of the first heat exchange plate layers 11 and second heat exchange plate layers 12 has a heat exchange channel, and the heat exchange channels of the first heat exchange plate layers 11 and second heat exchange plate layers 12 have different directions, for example, one is in a front-to-back direction and the other is in a left-to-right direction. These alternating arrangements form a sub-core 1 of a microchannel heat exchanger. A plurality of sub-cores 1 are welded together to form a core assembly, used to produce large-scale microchannel heat exchangers, applicable to multiple technical fields such as ship propulsion, marine engineering, hydrogen energy, nuclear energy, and solar thermal power generation. The microchannel heat exchanger produced by the preparation method in this embodiment exhibits minimal deformation between the plates of the sub-core 1, reliable connection, and excellent dimensional accuracy and operational safety and reliability.

[0039] like Figure 2 As shown, in one embodiment of the present invention, a transition layer 2 is provided on the connecting surface of the sub-core 1, and two adjacent sub-cores 1 are welded together through the transition layer 2.

[0040] In this embodiment, a transition layer 2 is provided on the connecting surface of the sub-core 1. Two adjacent sub-cores 1 are welded through the transition layer 2. It should be understood that during the welding process, if the transition layer 2 is not provided, the microchannels at the connecting position will be subjected to a large welding heat input during welding. Under the action of welding stress, the sheet deformation will be too large, affecting the dimensional accuracy and heat exchange efficiency of the product. The provision of the transition layer 2 can withstand most of the welding heat input, thereby avoiding the problem of welding deformation of the sheet caused by welding heat input and ensuring the dimensional accuracy of the product. On the other hand, in conjunction with vacuum electron beam welding, a large aspect ratio is obtained. In particular, the setting of the three-point waveform significantly reduces the weld width, thereby greatly reducing the thickness of the transition layer 2. This significantly reduces the overall size, height and weight of the core assembly and improves its heat exchange efficiency.

[0041] In one embodiment of the present invention, the thickness of the transition layer 2 is 5mm-10mm, preferably 8mm. An excessively thick transition layer 2 increases the production cost of the core assembly, as well as its overall height and weight. Conversely, an insufficiently thick transition layer 2 results in excessive welding heat input to the heat exchange plates, leading to excessive plate deformation under welding stress and affecting the dimensional accuracy and heat exchange efficiency of the core assembly. In this embodiment, by employing vacuum electron beam welding and a three-point waveform design, the thickness of the transition layer 2 is significantly reduced. This ensures the dimensional accuracy and heat exchange efficiency of the core assembly while significantly reducing its production cost, height, and weight.

[0042] like Figure 2 As shown, in one embodiment of the present invention, a positioning structure is provided between the transition layers 2 that connect adjacent sub-cores 1, for auxiliary positioning during the stacking of sub-cores 1. To facilitate the stacking and connection of sub-cores 1, two transition layers 2 are provided in the sub-core 1, respectively disposed on the upper and lower surfaces of the sub-core 1. During stacking, the transition layer 2 that connects adjacent sub-cores 1 refers to the transition layer 2 located on the upper surface of the lower sub-core 1 and the transition layer 2 located on the lower surface of the upper sub-core 1. The positioning structure between these two layers facilitates rapid stacking of sub-cores 1, thereby improving the production efficiency of the core assembly, and also helps improve the stacking alignment accuracy of the sub-cores 1, thereby improving the dimensional accuracy of the core assembly.

[0043] In this embodiment, a positioning structure is provided between the transition layers 2 for auxiliary positioning when the sub-cores 1 are stacked. The positioning structure consists of positioning pin holes 3 and positioning pins 4. The positioning pins 4 extend into the positioning pin holes 3 to form a positioning. The positioning pin holes 3 and positioning pins 4 have simple structures, are easy to manufacture, and can effectively ensure positioning accuracy. There are two or more positioning structures, which can ensure the positioning accuracy between the sub-cores 1. It should be understood that in order to ensure that a positioning structure is formed between the transition layers 2 connecting the two sub-cores 1, a positioning pin hole 3 can be provided on one transition layer 2 of each sub-core 1, and a positioning pin 4 can be provided on the other transition layer 2; alternatively, positioning pin holes 3 can be provided on both transition layers 2 of a portion of the sub-cores 1, and positioning pins 4 can be provided on both transition layers 2 of another portion of the sub-cores 1; alternatively, positioning pin holes 3 and positioning pins 4 can be provided on each transition layer 2 of a sub-core 1, which can achieve rapid positioning and stacking between adjacent sub-cores 1.

[0044] In addition to providing a microchannel heat exchanger core assembly, the present invention further provides a method for manufacturing the above-mentioned core assembly, specifically including the following steps:

[0045] Step S1: Stack several sub-cores 1 sequentially on the turntable 6 inside the vacuum chamber of the electron beam welding machine;

[0046] Step S2: Evacuate the vacuum chamber to achieve the preset vacuum level;

[0047] Step S3: Turn on the electron beam welding gun 5 and use a three-point waveform to weld the stacked contact points between the sub-cores 1; the three-point waveform is set at intervals along the welding direction, such as... Figure 3 As shown;

[0048] Step S4: After welding, once the core assembly has cooled to below the first preset temperature, the vacuum chamber is de-vacuumed, the core is removed, and welding is complete. Figure 3 As shown.

[0049] In existing technologies, the welding between sub-cores 1 typically employs traditional fusion welding methods such as TIG welding and MIG welding. These methods suffer from high heat input during welding, leading to significant welding deformation and residual stress in the core. To overcome these drawbacks and effectively achieve the assembly welding between sub-cores 1, a transition layer 2 is required to prevent the welding from affecting the deformation of the plates. A bevel is then machined at the welding position for filler wire welding. To prevent significant welding deformation and residual stress, a thicker transition layer 2 is needed, typically ranging from 15mm to 30mm in thickness. Producing heat exchangers using this method results in larger core assembly dimensions, increased overall weight, and decreased heat exchange efficiency. In this embodiment, the connection between the sub-cores 1 is achieved through vacuum electron beam welding. This reduces heat input, thereby reducing deformation and residual stress during welding. It eliminates the need for a transition layer 2 or allows for a thinner transition layer 2, improving welding quality and the heat exchange efficiency of the finished core assembly. Furthermore, it allows for a weld with a large depth-to-width ratio. By employing a three-point waveform process, the electron beam penetration is increased, resulting in a large depth-to-width ratio of 15:1, as measured by metallographic photography. No beveling or filler wire is required during welding, reducing preparation work, increasing production efficiency, and lowering production costs. During the assembly welding of the sub-cores 1, a three-point waveform electron beam welding method is used. This reduces the weld width, preventing the large heat input from affecting the deformation of the plate. The three-point waveform also serves to preheat the weld, weld in the middle, and slow cool it at the end, maintaining a stable molten pool and effectively controlling nail tip defects at the root of the electron beam weld, ensuring welding quality and meeting the required weld strength.

[0050] In one embodiment of the present invention, the specific method for welding the two-by-two stacked contact positions of the sub-cores using a three-point waveform in step 3 is as follows:

[0051] Step 3.1: Use a three-point waveform to perform intermittent spot welding at the stacked contact positions between adjacent sub-cores 1;

[0052] Step 3.2: Use a three-point waveform to perform full weld seam welding on the stacked contact positions between the spot-welded sub-cores 1.

[0053] In this embodiment, intermittent spot welding of the position to be welded before formal welding can effectively fix the sub-core 1, so as to prevent welding deformation during formal welding from affecting the welding on the opposite side. While reducing welding deformation, it ensures the smooth progress of welding work.

[0054] like Figures 6 to 7As shown, in one embodiment of the present invention, the weld between two adjacent sub-cores 1 is rectangular. The two longer welds are denoted as A1 and A2, and the two shorter welds as A3 and A4. The welding sequence in step S3 is: weld A1 and A2 first, then weld A3 and A4. However, the order of welding A1 and A2 is not critical; A1 can be welded first, or A2 can be welded first. Similarly, the order of welding A3 and A4 is not critical; A3 can be welded first, or A4 can be welded first. By setting the above welding sequence, welding deformation can be significantly controlled, reducing the deformation impact of welding on the core, and effectively improving the dimensional accuracy and operational safety and reliability of the microchannel heat exchanger core. It should be noted that... Figure 7 In the diagram, A1, A2, A3, and A4 are the welding areas, while area E is the non-welding area. During welding, a vacuum state is maintained. The circumferential weld formed by A1, A2, A3, and A4 creates a stable connection between two adjacent sub-cores 1, ensuring connection strength while reducing welding deformation, thus guaranteeing the dimensional accuracy and safety of the core assembly. The circumferential weld between two adjacent sub-cores 1 forms the core assembly, achieving a stable connection between them while minimizing welding deformation.

[0055] When performing intermittent spot welding, welding is carried out in an equal-interval manner, with the interval between two adjacent intermittent welds being between 180mm and 220mm, preferably 200mm.

[0056] In embodiments of the present invention, the preset vacuum value is less than or equal to 5 × 10⁻³ Pa. Using vacuum electron beam welding to produce core components avoids contamination of the weld metal with harmful gases such as oxygen and nitrogen, and facilitates degassing and purification of the weld. Furthermore, it results in a large weld depth-to-width ratio, enabling welding without beveling and reducing pre-welding preparation work. Simultaneously, vacuum electron beam welding offers high speed, a small heat-affected zone, and minimal welding deformation, ensuring the dimensional accuracy of the finished product.

[0057] In another embodiment of the present invention, in step S4, the first preset temperature is 80℃-120℃. Cooling the core assembly in a vacuum chamber before the temperature drops to the first preset temperature can prevent oxidation of the high-temperature weld in air and also prevent weld cracks, thereby ensuring the quality of the welded joint and improving the safety of the core assembly. Preferably, the first preset temperature is 100℃.

[0058] The following example further illustrates the microchannel heat exchanger core assembly and its manufacturing method provided in this invention:

[0059] In this embodiment, the core assembly is formed by welding together several stacked sub-cores 1, and the structure of the sub-core 1 is as follows: Figure 1As shown, the sub-core 1 includes several first heat exchanger layers 11 and second heat exchanger layers 12, which are stacked alternately to form a cuboid structure. A transition layer 2 is provided at the upper and lower ends of the sub-core 1. The first heat exchanger layers 11, second heat exchanger layers 12, and transition layer 2 are connected by diffusion welding to form the sub-core 1. The thickness of the transition layer 2 is 5mm-10mm. Positioning pin holes 3 and / or positioning pins 4 are provided on the transition layer 2. The positioning pin holes 3 and positioning pins 4 on two adjacent sub-cores 1 cooperate for positioning. The manufacturing method of the above core assembly includes the following steps:

[0060] Step 1: Stack and assemble the sub-cores 1 sequentially onto the turntable 6 inside the electron beam welder, and position them at the center of the turntable 6;

[0061] Step 2: Place the assembled sub-core 1 into the vacuum chamber of the electron beam welding machine, close the vacuum chamber door, and evacuate the vacuum. Figure 3 The weld seams are arranged as shown, ready for welding;

[0062] Step 3: After the vacuum level reaches 5×10⁻³ Pa, turn on the electron beam welding gun 5 to perform electron beam spot welding of the core unit. During spot welding, apply the following load: Figures 4 to 5 The welding waveform shown has three points aligned with the weld direction. A small current is used, with a weld penetration depth of 3mm-10mm and a length of 80mm-100mm.

[0063] like Figure 6 As shown, the following is adopted Figures 4 to 5 The welding waveform shown illustrates the intermittent electron beam welding of symmetrical weld seams at equal intervals (200mm) at the ends and middle sections to fix the core and prevent stress deformation on the opposite sides during the formal welding. After the four weld seams (A1-A2, A3-A4) on the four sides of the core are intermittently spot welded in sequence and symmetrically, the formal welding process begins.

[0064] Welding is also performed symmetrically, i.e., A1-A4. (The following text appears to be a separate, unrelated instruction: "Using...") Figure 4 The electron beam welding process under the welding waveform involves rotating the turntable 6 after each weld is completed to weld the next weld.

[0065] Figure 7 The diagram shows the welding area between the cores. The cross-sectional area (A1-A4) is the welding area, and area E is the non-welding area, which is in a vacuum state.

[0066] It should be noted that the working distance between the electron beam welding gun 5 and the workpiece weld seam will change when welding A1 and A2 compared to welding A3 and A4. Therefore, when the working distance changes, the distance between the electron beam welding gun and the workpiece weld seam needs to be adjusted accordingly.

[0067] Step S4: After completing vacuum electron beam welding, wait for the core assembly to cool to below 100°C, then release the vacuum in the vacuum chamber to normal atmospheric pressure, open the furnace door and remove the core assembly to complete the core welding manufacturing.

[0068] The microchannel core assembly manufactured according to the above manufacturing method has the following advantages:

[0069] 1) No transition layer 2 may be added or a very thin transition layer 2 may be added between the sub-cores 1. Electron beam welding under three-point waveform can reduce the weld width and achieve effective penetration depth while effectively controlling root defects. The weld width is 2mm-3mm and the weld depth-to-width ratio reaches 15:1.

[0070] 2) High welding efficiency. Electron beam welding does not require the processing of welding bevels, and the weld can be fully penetrated in one pass without the need for multiple welding passes. The welding efficiency can be increased by 5 to 10 times compared with traditional welding methods (TIG welding, MIG welding).

[0071] 3) By optimizing the electron beam welding sequence, welding deformation can be significantly controlled, with core welding deformation less than 2mm. No subsequent machining or straightening treatment is required, which effectively improves the manufacturing precision and safety and reliability of the microchannel heat exchanger core assembly.

[0072] It should be noted that all directional and positional terms used in this invention, such as "up," "down," "left," "right," "front," "back," "vertical," "horizontal," "inner," "outer," "top," "lower," "tail end," "head end," and "center," are only used to explain the relative positional relationships and connection situations between components in a specific state. They are merely for the convenience of describing the invention and do not require the invention to be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the invention. Furthermore, descriptions involving "first," "second," etc., 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. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or a solution where both A and B are satisfied simultaneously.

[0073] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0074] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A microchannel heat exchanger core assembly, characterized in that: The microchannel heat exchanger core assembly includes several sub-cores (1); Several of the sub-cores (1) are stacked to form the microchannel heat exchanger core assembly, and the sub-cores (1) are connected by welding. The manufacturing method of the microchannel heat exchanger core assembly specifically includes the following steps: Step 1: Stack several of the sub-cores (1) sequentially on the turntable (6) inside the vacuum chamber of the electron beam welding machine; Step 2: Evacuate the vacuum chamber to achieve the preset vacuum level; Step 3: Turn on the electron beam welding gun (5) and use a three-point waveform to weld the two stacked contact positions of the sub-core (1); wherein, the three-point waveform is used for preheating at the front, welding in the middle, and slow cooling at the rear. Step 4: After welding, wait for the core assembly to cool to below the first preset temperature, remove the vacuum from the vacuum chamber, take out the core assembly, and complete the welding.

2. The microchannel heat exchanger core assembly as described in claim 1, characterized in that: Each of the sub-cores (1) includes a plurality of first heat exchange plate layers (11) and second heat exchange plate layers (12), the first heat exchange plate layers (11) and the second heat exchange plate layers (12) are stacked alternately to form the sub-core (1) in the shape of a cuboid. The first heat exchange plate layer (11) and the second heat exchange plate layer (12) are each provided with a heat exchange channel, and the heat exchange channels of the first heat exchange plate layer (11) and the second heat exchange plate layer (12) have different directions.

3. The microchannel heat exchanger core assembly as described in claim 1, characterized in that: A transition layer (2) is provided on the connecting surface of the sub-core (1), and two adjacent sub-cores (1) are welded together through the transition layer (2).

4. The microchannel heat exchanger core assembly as described in claim 3, characterized in that: A positioning structure is provided between the transition layers (2) for auxiliary positioning when the sub-cores (1) are stacked.

5. A microchannel heat exchanger core assembly as described in claim 4, characterized in that: The thickness of the transition layer (2) is 5 mm - 10 mm.

6. A microchannel heat exchanger core assembly as described in claim 4, characterized in that: The positioning structure includes a positioning pin hole (3) and a positioning pin (4), wherein the positioning pin (4) extends into the positioning pin hole (3) to form a positioning.

7. A microchannel heat exchanger core assembly as described in claim 1, characterized in that: In step 3, the specific method for welding the two-by-two stacked contact positions of the sub-core (1) using a three-point waveform is as follows: Step 3.1: Use a three-point waveform to intermittently spot weld the adjacent sub-cores (1) at their paired stacked contact positions; Step 3.2: Use a three-point waveform to perform full weld seam welding on the two stacked contact positions of the sub-core (1) after spot welding; When performing intermittent spot welding, welding is carried out at equal intervals, with the interval between two adjacent intermittent welds being between 180mm and 220mm.

8. A microchannel heat exchanger core assembly as described in claim 1, characterized in that: In step 4, the first preset temperature is 80℃-120℃.

9. A microchannel heat exchanger core assembly as described in claim 7, characterized in that: In step 3.1, the sequence of intermittent spot welding is as follows: first, intermittent spot welding is performed on the two longer welds between two adjacent sub-cores (1), and then intermittent spot welding is performed on the two shorter welds between two adjacent sub-cores (1).

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