A multi-cavity profiled microchannel flat tube and its extrusion manufacturing method

Abstract

This invention discloses a multi-cavity irregular-shaped microchannel flat tube and its extrusion manufacturing method, relating to the field of heat exchange equipment technology. The invention aims to solve the technical problems of existing microchannel flat tubes with uniform thickness, such as easy occurrence of incomplete welds and sagging during bonding and brazing, poor resistance to lateral bending, and excessive weight. The tube body includes flow channel areas and connecting areas alternately distributed along its width; the surface of the connecting area is concave inward, making its wall thickness smaller than that of the flow channel area; the flow channel area contains rectangular flow channels, 0.5-4 mm wide and 0.5-3 mm high; the thickness of the connecting area is 1 / 4 to 1 / 2 of that of the flow channel area. This invention achieves lightweight design, utilizes the concave area as an venting and weld groove during welding, and endows the tube body with excellent flexible bending capabilities.

Description

Technical Field

[0001] This invention relates to the field of core components and manufacturing technology of heat exchange equipment, and in particular to a multi-cavity irregular microchannel flat tube with a special cross-sectional profile and limited flow channel size, and its extrusion molding method. Background Technology

[0002] With the rapid development of new energy vehicle thermal management systems (such as battery liquid cooling belts), precision vehicle refrigerators, and high-end commercial air conditioning technologies, extremely stringent requirements have been placed on the heat exchange efficiency, structural compactness, and lightweighting of heat exchangers. Microchannel flat tubes, due to their extremely large specific surface area and excellent heat transfer performance, have become the preferred material for high-end heat exchanger cores.

[0003] Existing microchannel flat tubes generally employ a full-drilled porous structure with a uniform cross-sectional thickness. However, in practical high-level engineering applications, this traditional uniform-thickness microchannel flat tube reveals the following significant technical drawbacks:

[0004] First, the yield rate of large-area brazing is low: When brazing wide, uniformly thick flat tubes to flat external substrates (such as air duct walls or heat spreaders), the contact area is too large and is a large flat surface. During the welding process, the molten brazing filler metal is unevenly distributed due to capillary action, which easily forms "blind spot welds" or air pockets in the central area. At the same time, excess liquid brazing filler metal has nowhere to overflow and often forms obvious brazing filler metal accumulation (sag) at the edge of the flat tube, which seriously affects the product appearance and heat transfer uniformity.

[0005] Second, the structure is rigid and prone to collapse when laterally bent: When traditional full-length flat tubes of equal thickness are used for complex spatial wiring (especially lateral bending to avoid other interfering components), the lack of stress release area makes the outer flow channel prone to breakage due to stretching, and the inner flow channel prone to collapse and instability due to compression, resulting in a sharp increase in flow resistance or even scrapping.

[0006] Third, the contradiction between lightweight and high pressure resistance: In order to meet high-pressure conditions such as CO2 refrigerant, the overall wall thickness of the flat tube must be increased. However, this results in excessive metal material being piled up in non-core heat exchange areas, which not only increases the weight of the tube but also violates the principle of cost reduction and efficiency improvement.

[0007] Therefore, there is an urgent need in this field for a novel microchannel flat tube architecture that can systematically solve the comprehensive technical challenges of large-area welding drainage, flexible bending, and lightweighting without sacrificing the pressure-bearing capacity of the core flow channel. Summary of the Invention

[0008] To solve the above-mentioned technical problems, in a first aspect, the present invention provides the following technical solution:

[0009] A multi-cavity irregular microchannel flat tube includes: a tube body, wherein at least two flow channel regions and at least one connecting region are alternately distributed along the width direction of its cross-section, the connecting region being located between two adjacent flow channel regions; multiple independent flow channels are spaced apart inside the flow channel regions along the width direction of the tube body, the flow channels being used for the flow of working fluid; the upper and lower outer surfaces of the connecting region are concave inward relative to the upper and lower outer surfaces of the flow channel regions, such that the outer wall thickness of the connecting region is less than the outer wall thickness of the flow channel region; the cross-section of the flow channel is rectangular, the flow channel having an inner diameter dimension a along the width direction of the tube body and an inner diameter dimension b along the thickness direction of the tube body, wherein the value of a is limited to the range of 0.5 mm to 4 mm, and the value of b is limited to the range of 0.5 mm to 3 mm.

[0010] By employing a unique combination of techniques—including an irregularly shaped cross-section internally divided into a flow channel region and an inwardly recessed connection region, and strictly limiting the microchannel dimensions to 0.5 mm to 4 mm (width) and 0.5 mm to 3 mm (height)—this invention achieves a revolutionary transformation from "large-area full-surface contact" to "multi-strand narrow-strip surface contact." The recessed connection region not only eliminates excess weight but also forms a natural stress-relieving zone; while the strictly controlled rectangular micropore size avoids heat transfer dead zones caused by excessively large pore sizes and also avoids a sharp increase in flow resistance caused by excessively small pore sizes, achieving a perfect coupling of heat transfer performance, mechanical deformation capability, and lightweight design.

[0011] In a preferred embodiment of the present invention, the maximum thickness of the connecting region in the tube body thickness direction is H1, and the maximum thickness of the flow channel region in the tube body thickness direction is H2, wherein the ratio of H1 to H2 is limited to one-quarter to one-half. By further employing the golden ratio of one-quarter to one-half thickness, the present invention can also achieve a perfect balance between pressure resistance and lightweight / flexibility. If it is greater than one-half, sufficient flexibility and drainage depth cannot be provided; if it is less than one-quarter, the excessively thin connecting region will cause the tube body to be easily torn and damaged longitudinally when subjected to high-pressure refrigerant evaporation or extrusion molding.

[0012] In a preferred embodiment of the present invention, the span dimension of the connecting area in the tube width direction is W1, and the span dimension of the flow channel area in the tube width direction is W2, wherein the ratio of W1 to W2 is limited to one-fifth to one-third. By further employing a span width ratio of one-fifth to one-third, the present invention can also achieve an optimal balance between heat exchange area and process clearance space. This avoids a sharp reduction in effective heat transfer area due to an excessively wide connecting area, while also ensuring sufficient weld groove width to isolate thermal interference between adjacent flow channel areas.

[0013] In a preferred embodiment of the present invention, the outer surface transition position between the connecting area and the flow channel area is provided with an arc transition surface or an inclined chamfer surface to eliminate stress concentration due to deformation; the connecting area is a solid metal structure without any fluid channels. By further adopting the structural features of the outer surface transition surface and the solid connecting area, the present invention can also achieve a leap in the fatigue resistance of the structure. The arc transition eliminates the stress concentration points caused by abrupt changes in the step, while the solid structure completely eliminates the risk of refrigerant leakage due to micro-cracks in this weak area under high-pressure cycling.

[0014] In a preferred embodiment of the present invention, adjacent flow channels within the same flow channel region are separated by longitudinal ribs, the wall thickness of which is limited to 0.2 mm to 1.0 mm. By further employing specific longitudinal rib thickness limiting technical features, the present invention can also maintain the compressive strength of the flat tube under internal pressure while ensuring the lateral heat conduction efficiency of adjacent flow channels.

[0015] In a preferred embodiment of the present invention, the flow channel region includes a first outer wall located above and a second outer wall located below, wherein the thickness of both the first and second outer walls is greater than or equal to the wall thickness of the longitudinal ribs, and is limited to 0.3 mm to 1.5 mm. By further employing the technical feature of thickening the outer wall and setting a specific threshold, the present invention can also achieve excellent resistance to external stone puncture and chemical corrosion tolerance, significantly improving the service life of the exposed heat exchange core component.

[0016] In a preferred embodiment of the present invention, the tube body is integrally extruded from aluminum alloy or copper alloy, and the upper and lower surfaces of the tube body are axially symmetrically distributed with respect to the horizontal central axis of the tube body. By further employing the technical features of integral extrusion of high thermal conductivity metal and axial symmetry, the present invention can also achieve non-directional blind assembly, improve assembly efficiency, and eliminate tube warping deformation caused by inconsistent stress on the upper and lower surfaces during thermal expansion and contraction.

[0017] In a preferred embodiment of the present invention, the tube extends along its length and is divided into a straight heat exchange section in the middle and bent connecting sections at both ends. The bent connecting sections use the connecting area as a flexible deformation hub and undergo plastic bending in a direction away from the plane of the straight heat exchange section. By further employing the technical feature of bending away from the plane at the ends, the present invention can also achieve ingenious spatial avoidance. When the two ends of the flat tube need to be connected to a collector tube with an outer diameter greater than the thickness of the flat tube, this bending clearance ensures that the straight heat exchange section in the middle is not interfered with by the collector tube, achieving 100% zero-distance fit with the external plane.

[0018] To solve the above-mentioned technical problems, in a second aspect, the present invention provides the following technical solution:

[0019] A method for extruding a multi-cavity irregular microchannel flat tube as described in the first aspect includes the following steps: providing a thermally conductive metal ingot and heating it to its plastic rheological temperature; pushing the heated metal ingot into an extrusion die; the forming orifice of the extrusion die includes a wide-slit extrusion zone corresponding to the flow channel zone, a narrow-slit extrusion zone corresponding to the connecting zone, and multiple forming mandrels disposed in the wide-slit extrusion zone; after the metal passes through the extrusion die, the metal material generates differentiated flow rates in the narrow-slit extrusion zone and the wide-slit extrusion zone, and is integrally extruded into a tube body having the inwardly recessed connecting zone and the flow channel inside; and cooling and shaping the extruded tube body.

[0020] By employing a technique that utilizes wide and narrow slit extrusion dies to generate differentiated plastic flow rates in high-temperature metal, thereby enabling the one-time molding of irregularly shaped tubes, this invention achieves mass production of composite flat tubes with integrated drainage channels at extremely low manufacturing costs. This method ensures dense lattice continuity between the flow channel region and the connecting region from a metallurgical microstructure perspective, endowing the tube with extremely high overall compressive strength and tear resistance.

[0021] In a preferred embodiment of the present invention, the metal ingot is made of aluminum alloy, and the gap height of the narrow-slit extrusion zone is controlled to be one-quarter to one-half of the gap height of the wide-slit extrusion zone, in order to balance the deformation resistance of the metal flowing laterally from the wide-slit extrusion zone to the narrow-slit extrusion zone during the extrusion process. By further employing the metal rheological constraint ratio technology, the present invention can also achieve a significant extension of the die life. It overcomes the industry bottleneck in irregular microchannel extrusion where the cantilever mandrel is "broken" by the metal flow due to extremely uneven local flow velocity.

[0022] In a preferred embodiment of the present invention, after cooling and shaping the tube body, a lateral bending process is further included: applying a bending force to bend the tube body along the longitudinally extending connecting area; the connecting area, as a weak area, absorbs the main deformation stress to form a flexible hinge, causing the adjacent flow channel areas to deflect relatively while the internal flow channel cross-section remains unchanged. By further employing a lateral bending forming step based on an irregular cross-section, the present invention can also achieve irregular conformal laying of flat tubes in confined spaces, and the bending process does not cause flow channel collapse, ensuring constant fluid resistance.

[0023] In a preferred embodiment of the present invention, after cooling and shaping the tube body, the method further includes assembling the tube body into a heat exchanger assembly: providing a heat exchange substrate with a flat contact surface; laying the tube body flat on the heat exchange substrate, so that the outer surface of the flow channel region contacts the contact surface and pre-places brazing filler metal; the connection region, due to its inward concavity, forms a non-welding gap extending along the length of the tube body between its surface and the contact surface; high-temperature brazing is performed, and the molten liquid brazing filler metal forms a tight weld between the flow channel region and the contact surface; excess liquid brazing filler metal is drained into and retained in the non-welding gap. By further employing the large-area brazing drainage process technology, the present invention can also fundamentally eliminate the obvious brazing filler metal edge accumulation caused by large-area welding. The non-welding gap becomes a perfect "welding space" and "venting channel," significantly improving the consistency of welding strength and the appearance quality of the finished product.

[0024] In a preferred embodiment of the present invention, a phase-change refrigerant is introduced into the interior of the tube, the refrigerant being one of R134a, R600a, or carbon dioxide; the inner diameters a and b of the flow channel are configured to cause the phase-change refrigerant to form an annular flow or a fine mist flow within the flow channel region. By further employing microscopic thermodynamic two-phase flow control features, the present invention can also maximize the boiling heat transfer coefficient.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. Completely solves the problem of large-area brazing: Traditional flat tube full-plane contact leads to uncontrollable brazing filler metal flow. The specially designed thinned connection zone in this invention naturally forms a continuous non-welding gap between the assembly surfaces. In the high-temperature brazing furnace, this gap generates a weak negative pressure exhaust effect, extracting air bubbles and flux residue trapped within the welding interface of the flow channel area, while simultaneously cutting off and accommodating excess liquid capillary brazing filler metal. This causal relationship ensures that each flow channel area obtains a uniform and non-overflowing full weld, resulting in an extremely high yield.

[0027] 2. Achieving Zero-Damage Bending Avoidance and Lightweight Design: By removing redundant material from the intermediate heat exchange dead zone to form an inwardly recessed solid connection area, the amount of metal used per unit length is significantly reduced (cost reduction). More importantly, this recessed weak area acts like a "flexible hinge." When external force is applied during lateral spatial tubing, the main plastic deformation is concentrated in this solid weak area, effectively protecting the areas containing microporous channels on both sides from compressive stress damage, achieving zero-damage wiring in complex spaces.

[0028] 3. Limiting heat transfer efficiency due to size specificity: By strictly controlling the dimensions of the rectangular flow channel within a specific range of 0.5 to 4 mm in width and 0.5 to 3 mm in height, and combining this with a specific width-to-thickness ratio, an inseparable thermodynamic and mechanical coupling system is formed. This ensures that the internal fluid shear stress and tube wall heat transfer flux reach their optimal stagnation points while preventing the metal extrusion die from cracking, achieving superior system-level performance. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments disclosed in this invention, the accompanying drawings of the embodiments will be briefly described below. These drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0030] Figure 1 This is a schematic diagram showing the cross-section and microchannel dimensions of the multi-cavity irregular-shaped microchannel flat tube in an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of the longitudinal section of the multi-cavity irregular microchannel flat tube in an embodiment of the present invention. Detailed Implementation

[0032] The technical solutions (including preferred technical solutions) of the present invention will be further described in detail below with reference to the accompanying drawings and by way of listing some optional embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] This embodiment provides a multi-cavity irregular-shaped microchannel flat tube, such as Figure 1 As shown, this pipe is extremely suitable as the core heat exchange medium at the bottom of an evaporator or condenser.

[0035] It includes an integrally extruded aluminum alloy tube 100. Unlike existing uniform thickness profiles, this tube 100 exhibits a wavy or dumbbell-shaped alternating thickness characteristic along the width direction of its cross-section. Specifically, the tube has at least two flow channel regions 110 and at least one connecting region 120 sandwiched in between, distributed alternately in sequence.

[0036] Within the flow channel region 110, multiple independent flow channels 111 are densely arranged side-by-side along the width of the tube. These flow channels 111 traverse the entire tube and are used for the flow of high-pressure refrigerant (such as refrigerant or antifreeze). To ensure that the working fluid can form strong turbulence or two-phase annular flow within the micropores to enhance heat transfer, this embodiment strictly limits the cross-section of the flow channels 111 to a rectangular square hole shape. Figure 1The flow channel 111 has an inner diameter dimension 'a' along the width direction of the tube body and an inner diameter dimension 'b' along the thickness direction of the tube body. In this embodiment, 'a' (micropore width) is preferably 0.5 mm to 4 mm, and 'b' (micropore height) is preferably 0.5 mm to 3 mm. This dimensional microstructure maximizes the contact perimeter between the tube wall and the fluid per unit volume.

[0037] To ensure structural stability under extreme high-pressure refrigerant conditions (e.g., system operating pressure can reach over 10 MPa when using carbon dioxide as a refrigerant), adjacent flow channels 111 within the same flow channel region 110 are physically separated and structurally supported by longitudinal baffles 114. In this embodiment, the wall thickness of the longitudinal baffles 114 is precisely limited to 0.2 mm to 1.0 mm. This size range is of critical significance: it avoids internal liquid leakage or structural tearing and bursting under high pressure differential due to excessively thin baffles, while also avoiding unnecessary weight increase of the pipe and waste of effective internal flow cross-sectional area due to excessively thick baffles.

[0038] Furthermore, the flow channel 110 is tightly enclosed by two layers of solid metal walls along the height of the tube: a first outer wall 112 above the flow channel 111 and a second outer wall 113 below the flow channel 111. Since these two outer walls are directly exposed to the external environment, they must withstand not only the outward expansion pressure of the internal refrigerant but also potential impacts from stones, friction, or mechanical compression during assembly. Sufficient "metal melting allowance" (to prevent burn-through) must also be provided during external brazing. Therefore, in this embodiment, the thicknesses of the first outer wall 112 and the second outer wall 113 are set to be greater than or equal to the wall thickness of the longitudinal rib 114, specifically limited to 0.3 mm to 1.5 mm.

[0039] This micro-stress distribution design of "thick outer wall and thin inner ribs", combined with the extremely thinned connection area 120, enables the entire tube 100 to achieve extreme lightweighting while still possessing an ultra-high pressure resistance and external impact resistance comparable to traditional thick-walled round tubes.

[0040] The upper and lower outer surfaces of the connecting area 120 are significantly concave inward relative to the upper and lower outer surfaces of the flow channel areas 110 on both sides, making the connecting area 120 an "extremely thinned zone" on the cross-section of the pipe. Furthermore, to prevent the weak area from becoming a leak point, the connecting area 120 has no holes inside and is a solid metal body.

[0041] This embodiment provides clear critical limits on the proportions of each region of the tube: the maximum thickness of the connection region 120 is set to H1, and the maximum thickness of the flow channel region 110 is set to H2. Specifically, this embodiment employs a stringent ratio of H1 to H2 between one-quarter and one-half. When subjected to internal operating pressures exceeding 2.5 MPa or even 10 MPa, this structure retains sufficient lateral tensile strength (without cracking) and allows the connection region 120 to naturally act as a "flexible hinge" absorbing distortion stress when the tube undergoes lateral bending.

[0042] Meanwhile, the width span of the connection area 120 is set to W1, and the width span of the flow channel area 110 is set to W2. In this embodiment, the ratio of W1 to W2 is between one-fifth and one-third. This arrangement ensures that more than 75% of the area inside the tube remains a highly efficient heat exchange microporous area, guaranteeing a strong output of cold or heat.

[0043] Example 2

[0044] This embodiment focuses on describing the efficient extrusion manufacturing and component-level application process of the aforementioned multi-cavity irregular-shaped microchannel flat tube. The manufacturing and application method specifically includes:

[0045] Step 1: Select aluminum alloy 3003 or 3102 series that is easy to cut and has extremely high thermal conductivity as the ingot blank, and heat it in a soaking furnace to a high temperature to exhibit a good plastic rheological state.

[0046] Step Two: The metal ingot is fed into a specially designed die of an extruder for integral extrusion molding. Due to the extreme difference between the wide slit (corresponding to the flow channel region 110) and the narrow slit (corresponding to the connecting region 120) at the die exit section, the flow velocity gradient of the metal during the extrusion process is extremely large. Precisely because we limited the thickness ratio to not less than one-quarter in the aforementioned embodiment, the resistance to the lateral supplementary flow of metal from the wide slit to the narrow slit is controlled within a safe threshold, avoiding stress fatigue fracture of the cantilever needle tip in the die, and achieving stable one-time molding and output of the tube 100 with micropores and deep recesses.

[0047] Step 3: After discharge, perform rapid online spray quenching and tension straightening to eliminate residual internal stress and complete cooling and shaping.

[0048] Step 4: Assembly and Application with Large-Area Brazing (Key Point): To manufacture high-efficiency evaporators such as those on the exterior of car refrigerators, a section of irregularly shaped flat tube is laid flat on a metal duct wall substrate with a smooth surface. Due to the wavy characteristics of the tube's cross-section, only the outer surface of the flow channel area 110 has close surface contact with the substrate, while the recessed connecting area 120 is suspended, naturally forming a through-hole, non-welded gap channel with the substrate.

[0049] Step 5: Apply flux and a low-melting-point solder coating to the contact surface, and then place the entire assembly into a nitrogen-protected brazing furnace for high-temperature brazing. At high temperatures, the solder melts and forms a liquid capillary flow. At this point, perfect capillary adsorption occurs between the wide, flat metal substrate and the multiple separated flow channels 110, while excess overflowing liquid solder cannot cross the boundaries, is blocked, and drips down, remaining in the non-welding gap below the connection area 120. Simultaneously, the exhaust gas generated by the high-temperature vaporization of the flux is smoothly discharged to both ends along this gap channel. This process completely eliminates the problems of localized bulging, incomplete weld dead zones, and large nodular accumulations around the weld that easily occur during traditional large flat pipe welding.

[0050] Example 3

[0051] Based on the basic structure and process of Embodiments 1 and 2, this embodiment further introduces an "end space avoidance" design scheme with outstanding substantive features to avoid external interference components. This structure can be directly connected to your company's complex closed-loop refrigerant system.

[0052] Since the refrigerant in the microchannel tube is usually collected at the end of the heat exchanger, a large-diameter cylindrical manifold 200 (distribution pipe) needs to be horizontally welded to both ends of the multi-cavity irregular-shaped microchannel flat tube. However, in many compact assembly scenarios (such as installation close to the inner wall of the air duct), the outer diameter of the manifold will inevitably be much larger than the thickness of the flat tube. If the flat tube is designed in a straight line, the large manifold will prematurely press against the inner wall of the air duct, causing the main straight heat exchange section of the flat tube to be suspended in the air, resulting in fatal contact thermal resistance.

[0053] Therefore, this embodiment makes full use of the material toughness of the tube body 100, and divides the tube body along its length into a straight heat exchange section in the middle and a bent connection section near both ends.

[0054] During processing, a tooling die is used to apply a normal punching force to the bent connecting section. After the tube body is subjected to force, due to the extremely thin thickness of the connecting area 120 (only 1 / 4 to 1 / 2 of the thickness), the connecting area 120 first undergoes microscopic lattice slip and plastic deformation, which, like a hinge, causes the thick flow channel areas 110 on both sides to tilt as a whole. Finally, the bent connecting section bends and lifts at a small angle (such as 5° to 15°) in the direction away from the mating plane, causing the axis of the thick manifold welded to the end to shift outward.

[0055] This design cleverly utilizes the unique concave tube cross-sectional characteristics. Without sacrificing or compressing the internal flow area of ​​the microporous channel, it uses a slight "lifting" motion at both ends to create a perfect suspended clearance space for the large manifold, thus ensuring that the straight heat exchange section in the middle, which is several hundred millimeters long, can achieve 100% zero-distance tight fit with the external air duct wall panel.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the spirit and principle of the present invention (such as changing the type of refrigerant, changing the material of the heat-conducting metal, or the micro-tooth-shaped turbulence structure), and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0057] It will be readily understood by those skilled in the art that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, combinations, substitutions, improvements, etc., made under the spirit and principles of the present invention are included within the protection scope of the present invention.

Claims

1. A multi-lumen shaped microchannel flat tube characterized by, include: The tube body has at least two flow channel regions and at least one connecting region alternately distributed along the width direction of its cross-section, the connecting region being located between two adjacent flow channel regions; The interior of the flow channel area is provided with multiple independent flow channels at intervals along the width direction of the pipe body, and the flow channels are used for the flow of working fluid. The upper and lower outer surfaces of the connecting area are recessed inward relative to the upper and lower outer surfaces of the flow channel area, such that the outer wall thickness of the connecting area is less than the outer wall thickness of the flow channel area. The cross-section of the flow channel is rectangular, and the flow channel has an inner diameter dimension a along the width direction of the tube body and an inner diameter dimension b along the thickness direction of the tube body. The value of a is limited to 0.5 mm to 4 mm, and the value of b is limited to 0.5 mm to 3 mm.

2. The multi-cavity irregular-shaped microchannel flat tube according to claim 1, characterized in that, The maximum thickness of the connecting area in the tube body thickness direction is H1, and the maximum thickness of the flow channel area in the tube body thickness direction is H2. The ratio of H1 to H2 is limited to one-quarter to one-half.

3. The multi-cavity irregular-shaped microchannel flat tube according to claim 2, characterized in that, The span dimension of the connecting area in the width direction of the pipe body is W1, and the span dimension of the flow channel area in the width direction of the pipe body is W2. The ratio of W1 to W2 is limited to one-fifth to one-third.

4. The multi-cavity irregular-shaped microchannel flat tube according to claim 1, characterized in that, Within the same flow channel region, two adjacent flow channels are separated by longitudinal ribs.

5. The multi-cavity irregular-shaped microchannel flat tube according to any one of claims 1 to 4, characterized in that, The tube body is integrally extruded from aluminum alloy or copper alloy, and the upper and lower surfaces of the tube body are axially symmetrical about the horizontal central axis of the tube body.

6. The multi-cavity irregular-shaped microchannel flat tube according to claim 1, characterized in that, The tube extends along its length and is divided into a straight heat exchange section in the middle and bent connecting sections at both ends; the bent connecting sections use the connecting area as a flexible deformation hub and undergo plastic bending in a direction away from the plane of the straight heat exchange section.

7. A method for extruding multi-cavity irregular-shaped microchannel flat tubes, used to manufacture multi-cavity irregular-shaped microchannel flat tubes as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Provide thermally conductive metal ingots and heat them to their plastic rheological temperature; The heated metal ingot is pushed into the extrusion die; the forming die includes a wide-slit extrusion zone corresponding to the flow channel zone, a narrow-slit extrusion zone corresponding to the connecting zone, and multiple forming mandrels disposed in the wide-slit extrusion zone; After the metal passes through the extrusion die, the metal material generates differentiated flow rates in the narrow-slit extrusion zone and the wide-slit extrusion zone, and is integrally extruded into a tube having the inwardly recessed connecting area and the internal flow channel; The extruded tube is then cooled and shaped.

8. The extrusion manufacturing method according to claim 7, characterized in that, The metal ingot is made of aluminum alloy, and the gap height of the narrow-slit extrusion zone is controlled to be one-quarter to one-half of the gap height of the wide-slit extrusion zone, so as to balance the deformation resistance of the metal flowing laterally from the wide-slit extrusion zone to the narrow-slit extrusion zone during the extrusion process.

9. The extrusion manufacturing method according to claim 7, characterized in that, After the tube body is cooled and shaped, the process further includes a step of lateral bending of the tube body: applying a bending force to cause the tube body to bend along the longitudinally extending connection area; the connection area, as a weak area, absorbs the main deformation stress to form a flexible hinge, causing the adjacent flow channel areas to deflect relative to each other while the flow channel cross-section inside remains unchanged.

10. The extrusion manufacturing method according to claim 7, characterized in that, After cooling and shaping the tube, the process further includes assembling the tube into a heat exchanger assembly: providing a heat exchange substrate with a flat mating surface; laying the tube flat on the heat exchange substrate, so that the outer surface of the flow channel region is in contact with the mating surface and pre-applying brazing filler metal; the connection region is recessed inward, and a non-welding gap is formed between its surface and the mating surface, extending along the length of the tube; high-temperature brazing is performed, and the molten liquid brazing filler metal forms a tight weld between the flow channel region and the mating surface; excess liquid brazing filler metal is drained into and retained in the non-welding gap.

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