A microchannel heat exchanger and its preparation method and application

Abstract

The present invention discloses a microchannel heat exchanger, a preparation method thereof and an application thereof, belonging to the technical field of microchannel heat exchangers. The microchannel heat exchanger provided by the present invention is composed of a plurality of cold side plates, hot side plates and cover plates stacked in sequence. Among them, the cold side plate or the hot side plate includes a plurality of parallel array microchannels arranged at equal intervals, and the cold side plate or the hot side plate is formed by pressing a welding layer, a corrosion-resistant functional layer and a strength support layer. The prefabricated flow channel plate technology using alloy powder + pre-pressing process adopted by the present invention increases the combination of material design of the microchannel heat exchanger, making it possible to realize the design requirements of heat exchangers such as high strength, corrosion resistance and high thermal conductivity that cannot be fully achieved by conventional materials in the same heat exchanger. Through the gradient arrangement of alloy powder, the weldable material system of diffusion welding technology is expanded, and the material categories of microchannel heat exchangers are expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of microchannel heat exchangers, and in particular, to a microchannel heat exchanger, a preparation method thereof, and an application thereof. Background Art

[0002] A microchannel heat exchanger is an efficient and compact heat exchange device that achieves excellent heat exchange performance by transferring fluids in microchannels. The microchannel heat exchanger has several advantages compared to traditional heat exchangers. High-efficiency heat exchange: The small size of the microchannels shortens the heat transfer distance between the fluid and the solid, thereby improving the heat exchange efficiency. Fast response: Due to its small volume and low heat capacity, the microchannel heat exchanger can respond to temperature changes more quickly. Energy conservation and environmental protection: Because of its high-efficiency heat exchange characteristics, the microchannel heat exchanger can reduce the energy consumption during equipment operation and achieve energy conservation and emission reduction. Compact structure: The compact design of the microchannel heat exchanger makes it suitable for scenarios with limited space, such as the automotive and aerospace fields.

[0003] As a typical representative of microchannel heat exchangers, the printed circuit board heat exchanger has higher reliability and has broad application prospects in fields such as the petroleum and chemical industries, gasification technology, aerospace, fuel cells, and new energy. However, the high manufacturing cost has become the most important factor hindering its widespread application.

[0004] Solid-phase additive manufacturing technology, also known as solid-state 3D printing or SSAM. Different from traditional processing methods, solid-phase additive manufacturing technology constructs three-dimensional objects by adding materials layer by layer, rather than obtaining the required shape by removing materials. Vacuum diffusion welding technology is the most widely used solid-phase additive manufacturing technology. It is a welding technology that forms a good joint at the interface of the workpieces to be welded through atomic diffusion under certain temperature, pressure, and holding time conditions. Because the workpieces to be welded do not melt and have small deformation during the welding process, it is a solid-phase welding method very suitable for constructing complex internal cavity structures. With the progress of science and technology, diffusion welding is being widely applied in fields such as aeroengine blades, compact microchannel heat exchangers, and high heat flux density water-cooled plates.

[0005] The manufacturing process of microchannel heat exchangers mainly includes raw material sheet processing - flow channel plate processing - diffusion welding - combined welding - product inspection. The main processes of flow channel plate processing include chemical etching and machining. Machining microchannel plates is expensive and is currently only used in small amounts on difficult-to-etch materials such as superalloys and ceramics. Compared with machining, the chemical etching process is a process suitable for batch processing of flow channel plates. However, its processing cost is still higher than the requirements for large-scale commercial promotion of microchannel heat exchangers, and chemical etching is relatively mature for aluminum alloys, copper alloys, and stainless steels, while the etching of superalloys, ceramics, etc. still cannot achieve industrial batch production, thus severely restricting the large-scale promotion of microchannel heat exchangers.

[0006] Currently, the manufacturing process of microchannel heat exchangers has the disadvantages of high processing cost of flow channel plates, narrow range of processable materials (corrosion-resistant materials such as superalloys, ceramics, and Hastelloy are not easy to process), large damage to materials during diffusion welding, and single processing material, etc. Summary of the Invention

[0007] The object of the present invention is to provide a microchannel heat exchanger, its preparation method and application in order to overcome the defects existing in the above-mentioned prior art.

[0008] The present invention solves its technical problems by adopting the following technical solutions.

[0009] The present invention provides a microchannel heat exchanger, which includes alternately hot and cold and sequentially stacked plates and cover plates. The plates are composed of a substrate and grooves arranged at equal intervals along the width direction of the substrate. Among them, the substrate is composed of alternately arranged first welding areas and first corrosion-resistant areas, and the tops of two adjacent grooves are connected by a second welding area. The projection of the second welding area on the substrate corresponds to the first welding area on the substrate. The part between the substrate and the grooves is composed of a support area and a second corrosion-resistant area on the surface of the support area. Under specific working conditions, the materials selected for the first welding area, corrosion-resistant area and strength area are allowed to overlap.

[0010] The present invention also provides a preparation method for the above-mentioned microchannel heat exchanger, including: preparing the microchannel heat exchanger by means of layered laying and layered pre-pressing.

[0011] The present invention also provides an application of the above-mentioned microchannel heat exchanger in the field of high temperature and high pressure, applying the microchannel heat exchanger to supercritical carbon dioxide heat exchange.

[0012] The present invention has the following beneficial effects:

[0013] A microchannel heat exchanger, its preparation method and application provided by the present invention. The microchannel heat exchanger provided by the present invention includes alternately hot and cold and sequentially stacked plates and cover plates. The plates are composed of a substrate and grooves arranged at equal intervals along the width direction of the substrate. Among them, the substrate is composed of alternately arranged first welding areas and first corrosion-resistant areas, and the tops of two adjacent grooves are connected by a second welding area. The projection of the second welding area on the substrate corresponds to the first welding area on the substrate. The part between the substrate and the grooves is composed of a support area and a second corrosion-resistant area on the surface of the support area. The above-mentioned microchannel heat exchanger provided by the present invention is prepared by layered laying and layered pre-pressing of alloy powders with different compositions. Through the gradient arrangement of alloy powders, the weldable material system of diffusion welding technology is expanded, and the material categories of microchannel heat exchangers are expanded, so as to provide a microchannel heat exchanger with high strength, high corrosion resistance, and high welding reliability and can be used in corrosive media such as lead bismuth, and it can be applied to heat exchange in high temperature and high pressure fields such as supercritical carbon dioxide. Brief Description of the Drawings

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0015] Figure 1 It is a cross-sectional view of the heat exchanger core;

[0016] Figure 2 They are different functional areas of the heat exchange plate;

[0017] Reference numerals in the drawings: 1-1 - Cover plate, 1-2 - Cold side plate, 1-3 - Hot side plate, 2-1 - First welding area, 2-2 - Second welding area, 2-3 - First corrosion-resistant area, 2-4 - Second corrosion-resistant area, 2-5 - Support area. Detailed Embodiments

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0019] The following specifically describes a microchannel heat exchanger provided by the embodiments of the present invention, its preparation method, and applications.

[0020] In a first aspect, the embodiments of the present invention provide a microchannel heat exchanger, which includes alternately cold and hot plates and cover plates stacked in sequence. The plates are composed of a substrate and grooves arranged at equal intervals along the width direction of the substrate. Among them, the substrate is composed of alternately arranged first welding areas and first corrosion-resistant areas, and the tops of adjacent two grooves are connected by a second welding area. The projection of the second welding area on the substrate corresponds to the first welding area on the substrate. The part between the substrate and the grooves is composed of a support area and a second corrosion-resistant area on the surface of the support area.

[0021] The microchannel heat exchanger designed in the embodiments of the present invention has a structure as Figure 1 shown. The heat exchanger includes a cold side plate 1-2, a hot side plate 1-3, and a cover plate 1-1 stacked in sequence. Among them, the heat exchange plate (cold side plate or hot side plate) is formed by powder pressing, and its cross-section is as Figure 2 shown. According to the required functional characteristics, the heat exchange plate can be divided into the following areas: 2-1 - First welding area, 2-2 - Second welding area, 2-3 - First corrosion-resistant area, 2-4 - Second corrosion-resistant area, 2-5 - Support area.

[0022] In a second aspect, an embodiment of the present invention further provides a method for manufacturing the above microchannel heat exchanger, including: preparing the microchannel heat exchanger by means of layered laying and layered pre-pressing.

[0023] In an alternative embodiment, the method includes the following steps: arranging the solder powder and the corrosion-resistant powder at intervals and performing a first pre-pressing, then laying the high-strength and high-temperature-resistant powder for a second pre-pressing of the flow channel shape, laying the corrosion-resistant powder on the surface of the formed groove and performing a third pre-pressing, then laying the solder powder at the connection between the tops of two adjacent grooves and performing a fourth pre-pressing, and then performing a fifth pre-pressing on the whole to complete the production of the plate. Stack the produced plates alternately in hot and cold states. After the stacking is completed, diffusion welding is performed, and finally the head and the nozzle are welded to prepare the microchannel heat exchanger.

[0024] In an alternative embodiment, the first pre-pressing includes: arranging the solder powder and the corrosion-resistant powder with the required mass ratio at intervals, and performing the first pre-pressing with a pressing force of 10-50 MPa.

[0025] In an alternative embodiment, the second pre-pressing, the third pre-pressing, and the fourth pre-pressing include: after the first pre-pressing is completed, laying the high-strength and high-temperature-resistant powder, and using a special mold to perform a pre-pressing of the flow channel shape with a pressing force of 50-100 MPa for the second pre-pressing; laying the corrosion-resistant powder on the surface of the formed groove and performing the third pre-pressing with a pressing force of 20-70 MPa, and laying the solder powder at the connection between the tops of two adjacent grooves and performing the fourth pre-pressing with a pressing force of 20-70 MPa.

[0026] In an alternative embodiment, the fifth pre-pressing includes: after passing the surface scanning inspection after the fourth pre-pressing, performing a fifth pressing on the whole with a pressing force of 120 MPa to 250 MPa.

[0027] In an alternative embodiment, the solder powder includes any one of 316L and pure nickel, the corrosion-resistant powder includes any one of FeAl3 and Monel400, and the high-strength and high-temperature-resistant powder includes any one of 310S and Inconel617.

[0028] In an alternative embodiment, the number of powder laying layers for the first pre-pressing, the third pre-pressing, and the fourth pre-pressing is 1 layer, the number of powder laying layers for the second pre-pressing is 5 layers, and the thickness of each powder laying layer is 0.1-0.3 mm.

[0029] In an alternative embodiment, after the first pre-pressing, the second pre-pressing, the third pre-pressing, and the fourth pre-pressing are completed, the pre-pressed surface is purged to remove the excess powder.

[0030] In an alternative embodiment, the diffusion welding is performed as follows: the welding temperature is 1030 ± 50 °C, the heating rate is 2 - 10 °C / min, the welding pressure is 2 - 15 MPa, the holding time is 1 - 8 h, and rapid cooling is initiated after welding to cool the workpiece to room temperature as soon as possible.

[0031] As can be seen above, the embodiments of the present invention provide a method for manufacturing a microchannel heat exchanger, and the manufacturing process is as follows: alloy powder is used as the unit for manufacturing. The alloy powder is subjected to powder spreading, pressing, assembly, diffusion welding, combined welding, and product inspection to prepare a microchannel heat exchanger, where the powder spreading and pressing processes can be repeated multiple times.

[0032] The heat exchanger is manufactured by means of layered laying and layered pre-pressing. That is, it is laid layer by layer from the bottom layer upwards, and the powder thickness of each layer varies from 0.1 to 0.3 mm. The pre-pressure is generally 10 - 50 MPa, and the final compaction force is 120 MPa - 250 MPa. The pre-pressing is carried out by relatively gentle vertical plane machining, and the final compaction can be carried out by plane pressing with a hydraulic press or rolling according to the equipment situation. According to the powder type, the pressing process can be carried out under vacuum or in the atmosphere to control the oxygen content in the powder.

[0033] After the flow channel plate is pressed, the flow channel plates are stacked in sequence and loaded into a vacuum diffusion welding furnace. The assembled microchannel heat exchanger core is welded, and a reasonable welding temperature is designed according to the material, and a reasonable holding time and welding pressure are set according to the size of the microchannel heat exchanger core. After welding, samples are taken from the margin area of the product core and surface coloring and other inspections are carried out to ensure the welding quality. The remaining nozzles and heads are welded according to the heat exchanger design, and product testing is carried out.

[0034] The features and performance of the present invention will be further described in detail below in conjunction with embodiments.

[0035] Embodiment 1

[0036] In this embodiment, a microchannel heat exchanger made of iron-based with high strength, high corrosion resistance, and high welding reliability is designed, which can be used in corrosive media such as lead-bismuth and can also be applied to high-temperature and high-pressure fields such as supercritical carbon dioxide. Refer to Figure 1 and Figure 2 , and the preparation of the microchannel heat exchanger includes the following steps:

[0037] A 0.3 mm thick bottom layer powder is precisely laid using a special powder sieve. The bottom layer powder consists of weldable powder 316L (corresponding to the first welding zone 2 - 1 of the microchannel heat exchanger) and corrosion-resistant powder FeAl3 (corresponding to the first corrosion-resistant zone 2 - 3 of the microchannel heat exchanger). They are arranged at intervals. After laying, pre-pressing is carried out with a compaction force of 50 Mpa.

[0038] After pressing is completed, lay the high-strength and high-temperature-resistant powder 310S (corresponding to the support area 2-5 of the microchannel heat exchanger) in layers. Each layer has a thickness of 0.3 mm and 5 layers are laid. Use a special mold to pre-press the flow channel shape, and the pre-tightening pressure is 60 MPa. Use a sizing tooling to scrape off the excess powder, and lay 0.3 mm of corrosion-resistant powder FeAl3 (corresponding to the second corrosion-resistant area 2-4 on the surface of the support area of the microchannel heat exchanger) in the formed microchannels, and perform pre-pressing with a pre-tightening pressure of 30 MPa. After pre-tightening is completed, blow the pre-pressed surface to remove the excess powder.

[0039] Lay the easy-to-weld powder 316L (corresponding to the second welding area 2-2 of the microchannel heat exchanger) at the connection of two adjacent grooves. The powder layer has a thickness of 0.3 mm and is pressed to 30 MPa. After pre-pressing is completed, perform surface blowing.

[0040] Perform a scanning inspection on the surface after pre-pressing is completed to confirm that there are no defects such as chipping and shrinkage cavities.

[0041] Perform the final pressing on the plate, with a pressure of 190 MPa.

[0042] Stack the pressed plates alternately in hot and cold states. After stacking is completed, place them in a vacuum diffusion welding furnace.

[0043] Turn on the diffusion welding furnace, set the parameters as welding temperature 1030 °C, heating rate 5 °C / min, welding pressure 10 MPa, and heat preservation time 3 h. Weld the product. After welding is completed, turn on the rapid cooling to cool the workpiece to room temperature as soon as possible.

[0044] After welding is completed, take metallographic and mechanical property test specimens in the surplus area to observe whether they meet the design requirements. And perform fluorescence detection on the welding surface to observe whether there are welding cracks.

[0045] Weld the heads and nozzles. After welding is completed, perform a pressure test to confirm that the product meets the design requirements.

[0046] Example 2

[0047] In this example, a microchannel heat exchanger made of iron-based high-strength, high-corrosion-resistant, and high-welding-reliability materials is designed, which can be used in corrosive media such as lead-bismuth, and can also be applied to high-temperature and high-pressure fields such as supercritical carbon dioxide. See Figure 1 and Figure 2 , the preparation of the microchannel heat exchanger includes the following steps:

[0048] Precisely lay the bottom layer powder with a thickness of 0.3 mm using a special powder sieve. The bottom layer powder consists of easy-to-weld powder 316L (corresponding to the first welding area 2-1 of the microchannel heat exchanger) and corrosion-resistant powder FeAl3 (corresponding to the first corrosion-resistant area 2-3 of the microchannel heat exchanger). They are arranged at intervals. After laying is completed, perform pre-pressing with a pressing force of 30 Mpa.

[0049] After the pressing is completed, lay the high-strength and high-temperature-resistant powder 310S (corresponding to the support area 2-5 of the microchannel heat exchanger) in layers. Lay 5 layers with a thickness of 0.3 mm for each layer, and use a special mold to pre-press the flow channel shape. The pre-tightening pressure is 150 MPa. Use a sizing tooling to scrape off the excess powder, and lay 0.3 mm of corrosion-resistant powder FeAl3 (corresponding to the second corrosion-resistant area 2-4 on the surface of the support area of the microchannel heat exchanger) in the formed microchannels, and perform pre-pressing with a pre-tightening pressure of 70 MPa. After the pre-tightening is completed, blow the pre-pressed surface to remove the excess powder.

[0050] Lay the easy-welding powder 316L at the connection of two adjacent grooves (corresponding to the second welding area 2-2 of the microchannel heat exchanger), with a powder layer thickness of 0.3 mm, and press it to 70 MPa. After the pre-pressing is completed, perform surface blowing.

[0051] Perform a scanning inspection on the surface after the pre-pressing is completed to confirm that there are no defects such as chipping and shrinkage cavities.

[0052] Perform the final pressing on the plate with a pressure of 250 MPa.

[0053] Stack the pressed plates alternately in hot and cold states. After the stacking is completed, put them into a vacuum diffusion welding furnace.

[0054] Turn on the diffusion welding furnace, set the parameters as welding temperature 1080 °C, heating rate 10 °C / min, welding pressure 15 MPa, and heat preservation time 8 h, and weld the product. After the welding is completed, turn on the rapid cooling to cool the workpiece to room temperature as soon as possible.

[0055] After the welding is completed, take metallographic and mechanical property test specimens in the surplus area to observe whether they meet the design requirements. And perform fluorescence inspection on the welding surface to observe whether there are welding cracks.

[0056] Weld the heads and nozzles. After the welding is completed, perform a pressure test to confirm that the product meets the design requirements.

[0057] Example 3

[0058] In this example, a microchannel heat exchanger made of nickel-based with high strength, high corrosion resistance, and high welding reliability is designed, which can be used in corrosive media such as lead-bismuth, and can also be applied to high-temperature and high-pressure fields such as supercritical carbon dioxide. See Figure 1 and Figure 2 , and the preparation of the microchannel heat exchanger includes the following steps:

[0059] A special powder sieve is used to precisely lay a bottom layer of powder with a thickness of 0.1 mm. The bottom layer of powder consists of solder powder pure nickel (corresponding to the first welding zone 2-1 of the microchannel heat exchanger) and Monel 400 (Monel alloy) (corresponding to the first corrosion-resistant zone 2-3 of the microchannel heat exchanger). They are arranged at intervals. After laying, pre-pressing is carried out with a pressing force of 50 Mpa.

[0060] After the pressing is completed, high-strength and high-temperature-resistant powder Inconel 617 (corresponding to the support zone 2-5 of the microchannel heat exchanger) is laid in layers. Each layer has a thickness of 0.3 mm and 5 layers are laid. A special mold is used for pre-pressing the runner shape with a pre-tightening pressure of 60 MPa. A sizing tooling is used to scrape off the excess powder. In the formed microchannels, 0.3 mm of corrosion-resistant powder Monel 400 (corresponding to the second corrosion-resistant zone 2-4 on the surface of the support zone of the microchannel heat exchanger) is laid and pre-pressed with a pre-tightening pressure of 30 MPa. After the pre-tightening is completed, the pre-pressed surface is purged to remove the excess powder.

[0061] Solder powder pure nickel is laid at the connection of two adjacent grooves (corresponding to the second welding zone 2-2 of the microchannel heat exchanger) with a powder layer thickness of 0.1 mm and pressed to 30 MPa. After the pre-pressing is completed, surface purging is carried out.

[0062] The surface after the pre-pressing is completed is scanned and inspected to confirm that there are no defects such as chipping and shrinkage cavities.

[0063] Final pressing of the plate is carried out with a pressure of 190 MPa.

[0064] The pressed plates are stacked alternately hot and cold, and after stacking is completed, they are placed in a vacuum diffusion welding furnace.

[0065] The diffusion welding furnace is started, and the parameters are set as welding temperature 1030 °C, heating rate 5 °C / min, welding pressure 10 MPa, and holding time 3 h. The product is welded. After welding is completed, rapid cooling is started to cool the workpiece to room temperature as soon as possible.

[0066] After welding is completed, metallographic and mechanical property test specimens are taken in the surplus area to observe whether they meet the design requirements. And fluorescence detection is carried out on the welding surface to observe whether welding cracks occur.

[0067] The head and nozzle are welded. After welding is completed, a pressure test is carried out to confirm that the product meets the design requirements.

[0068] Example 4

[0069] In this example, a microchannel heat exchanger made of nickel-based material with high strength, high corrosion resistance, and high welding reliability is designed, which can be used in corrosive media such as lead-bismuth and can also be applied to high-temperature and high-pressure fields such as supercritical carbon dioxide. For the microchannel heat exchanger, see Figure 1 and Figure 2, the preparation of the microchannel heat exchanger includes the following steps:

[0070] Precisely lay a bottom powder layer with a thickness of 0.1 mm using a special powder sieve. The bottom powder layer consists of solder powder pure nickel (corresponding to the first welding zone 2-1 of the microchannel heat exchanger) and Monel 400 (Monel alloy) (corresponding to the first corrosion-resistant zone 2-3 of the microchannel heat exchanger). They are arranged at intervals. After laying, perform pre-pressing with a pressing force of 50 Mpa.

[0071] After the pressing is completed, lay the high-strength and high-temperature-resistant powder Inconel 617 (corresponding to the support zone 2-5 of the microchannel heat exchanger) in layers. Each layer has a thickness of 0.3 mm and 5 layers are laid. Use a special mold to perform pre-pressing for the runner shape with a pre-tightening pressure of 100 MPa. Use a shaping tooling to scrape off the excess powder. Lay 0.3 mm of corrosion-resistant powder Monel 400 (corresponding to the second corrosion-resistant zone 2-4 on the surface of the support zone of the microchannel heat exchanger) in the formed microchannels, and perform pre-pressing with a pre-tightening pressure of 70 MPa. After the pre-tightening is completed, blow the pre-pressed surface to remove the excess powder.

[0072] Lay solder powder pure nickel at the connection of two adjacent grooves (corresponding to the second welding zone 2-2 of the microchannel heat exchanger) with a powder layer thickness of 0.1 mm, and press it to 70 MPa. After the pre-pressing is completed, perform surface blowing.

[0073] Perform a scanning inspection on the surface after the pre-pressing is completed to confirm that there are no defects such as chipping and shrinkage cavities.

[0074] Perform final pressing on the plate with a pressure of 250 MPa.

[0075] Stack the pressed plates alternately in hot and cold states. After stacking is completed, place them in a vacuum diffusion welding furnace.

[0076] Start the diffusion welding furnace, set the parameters as welding temperature 1080 °C, heating rate 10 °C / min, welding pressure 15 MPa, heat preservation time 8 h, weld the product. After welding is completed, start rapid cooling to cool the workpiece to room temperature as soon as possible.

[0077] After welding is completed, take metallographic and mechanical property test specimens in the surplus area to observe whether they meet the design requirements. And perform fluorescence detection on the welding surface to observe whether there are welding cracks.

[0078] Weld the head and the nozzle. After welding is completed, perform a pressure resistance test to confirm that the product meets the design requirements.

[0079] Compared with the prior art, the present invention has the following beneficial effects:

[0080] 1. The present invention uses alloy powder + pre-pressing process to prepare the prefabricated flow channel plate, completely getting rid of the selectivity of the etching process for materials;

[0081] 2. The present invention prepares a prefabricated flow channel plate by using alloy powder + pre-pressing process, without consumables such as etching consumables and processing tools, greatly reducing the processing cost of the flow channel plate.

[0082] 3. The technology of preparing a prefabricated flow channel plate by using alloy powder + pre-pressing process adopted by the present invention increases the combination of material design of the microchannel heat exchanger, making it possible to achieve the design requirements of heat exchangers such as high strength, corrosion resistance, and high thermal conductivity that cannot be fully realized by conventional materials in the same heat exchanger.

[0083] 4. By finely adjusting the ratio of elements in the alloy powder, the deterioration of the base material performance caused by too long holding time or too high welding temperature during the diffusion welding process can be greatly reduced.

[0084] 5. Through the gradient arrangement of the alloy powder, the weldable material system of the diffusion welding technology is expanded, and the material categories of the microchannel heat exchanger are expanded.

[0085] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A microchannel heat exchanger, characterized in that, The microchannel heat exchanger includes plates and cover plates that are alternately hot and cold and stacked in sequence. The plates are composed of a substrate and grooves arranged at equal intervals in the width direction of the substrate. Among them, the substrate is composed of a first welding area and a first corrosion-resistant area arranged at intervals, and the tops of two adjacent grooves are connected by a second welding area. The projection of the second welding area on the substrate corresponds to the first welding area on the substrate. The part between the substrate and the grooves is composed of a support area and a second corrosion-resistant area on the surface of the support area; The microchannel heat exchanger is prepared by a method of layered laying and layered pre-pressing, including the following steps: arranging easy-to-weld powder and corrosion-resistant powder at intervals and performing a first pre-pressing, then laying high-strength and high-temperature-resistant powder for a second pre-pressing of the flow channel shape, laying corrosion-resistant powder on the surface of the formed grooves and performing a third pre-pressing, then laying easy-to-weld powder at the connection between the tops of two adjacent grooves and performing a fourth pre-pressing, and then performing a fifth pre-pressing on the whole to complete the production of the plates. Stack the produced plates alternately hot and cold in sequence. After the stacking is completed, diffusion welding is carried out, and finally the end heads and nozzles are welded to prepare the microchannel heat exchanger.

2. A method for preparing a microchannel heat exchanger according to claim 1, characterized in that, The first pre-pressing includes: arranging the easy-to-weld powder and the corrosion-resistant powder in the required mass ratio at intervals, and performing a first pre-pressing with a pressing force of 10-50 MPa.

3. The preparation method according to claim 2, characterized in that, The second pre-pressing, the third pre-pressing, and the fourth pre-pressing include: after the first pre-pressing is completed, laying high-strength and high-temperature-resistant powder, and using a special mold to perform a pre-pressing of the flow channel shape with a pressing force of 50-100 MPa for the second pre-pressing; laying corrosion-resistant powder on the surface of the formed grooves and performing a third pre-pressing with a pressing force of 20-70 MPa, laying easy-to-weld powder at the connection between the tops of two adjacent grooves and performing a fourth pre-pressing with a pressing force of 20-70 MPa.

4. The preparation method according to claim 2, characterized in that, The fifth pre-pressing includes: after the surface after the fourth pre-pressing is scanned and inspected to be qualified, performing a fifth pressing on the whole, and the pressing force is 120 MPa-250 MPa.

5. The preparation method according to claim 2, characterized in that, The easy-to-weld powder includes any one of 316L and pure nickel, the corrosion-resistant powder includes any one of FeAl3 and Monel400, and the high-strength and high-temperature-resistant powder includes any one of 310S and Inconel617.

6. The preparation method according to claim 2, characterized in that, The number of powder-laying layers for the first pre-pressing, the third pre-pressing, and the fourth pre-pressing is 1 layer, the number of powder-laying layers for the second pre-pressing is 5 layers, and the thickness of each powder-laying layer is 0.1-0.3 mm. And after the first pre-pressing, the second pre-pressing, the third pre-pressing, and the fourth pre-pressing are completed, the pre-pressed surface is purged to remove excess powder.

7. The preparation method according to claim 2, characterized in that, The operation of the diffusion welding is as follows: the welding temperature is 1030±50 °C, the heating rate is 2-10 °C / min, the welding pressure is 2-15 MPa, the heat preservation time is 1-8 h, and after the welding is completed, rapid cooling is started to cool the workpiece to room temperature as soon as possible.

8. Use of the microchannel heat exchanger according to claim 1 or the microchannel heat exchanger prepared by the preparation method according to any one of claims 2-7 in the field of high temperature and high pressure, characterized in that The described microchannel heat exchanger is applied to supercritical carbon dioxide heat exchange.

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