Sintered high-flux heat exchange tube and preparation method thereof

Abstract

The application provides a sintered high-flux heat exchange pipe and a preparation method thereof. The sintered high-flux heat exchange pipe is prepared by rolling metal film layer green bodies prepared from metal powders with different particle sizes after being stacked in pairs, attaching the asymmetric metal film layer green bodies to the surface of a heat exchange pipe, and sintering and cooling to obtain the sintered high-flux heat exchange pipe. The sintered high-flux heat exchange pipe prepared by the application has the advantages of uniform thickness of the surface porous layer, high porosity, good combination of the porous layer and the base pipe, and remarkable effect of strengthening boiling heat transfer, and can meet the needs of high-efficiency heat exchange in high-energy-consumption industries such as petroleum, chemical industry, metallurgy, refrigeration and seawater desalination.

Description

Technical Field

[0001] This invention belongs to the field of heat exchanger tube manufacturing technology, specifically relating to a sintered high-throughput heat exchanger tube and its manufacturing method. Background Technology

[0002] With the global energy shortage becoming increasingly prominent, countries worldwide are placing great emphasis on the efficient use of energy. Industries such as petroleum, chemical, and metallurgy typically employ high-flux heat exchangers with high heat transfer efficiency to improve energy utilization. High-flux heat exchange tubes are key components of these exchangers. The tube surface features a porous layer structure with high-density interconnected pores, which not only increases the heat exchange area but also significantly increases the number of vaporization nuclei, thus substantially enhancing the boiling heat transfer capacity of the heat exchange tube. Based on the processing method of the porous layer, high-flux heat exchange tubes mainly include sintered, machined, and flame-sprayed types. Among them, sintered high-flux heat exchange tubes are highly efficient heat exchange tubes where a specific structured porous metal layer is formed on the surface of a smooth tube through sintering. They are currently the shell-and-tube heat exchange element with the most significant enhancement of boiling heat transfer performance.

[0003] The processing of sintered porous metal layers is technically demanding and requires high quality. Patent CN101367127A discloses a centrifugal coating and vacuum sintering method for processing porous metal layers inside heat exchanger tubes. Patent CN102653003A uses a spraying + sintering method to process porous metal layers on the surface of heat exchanger tubes. Patent CN113621962A discloses a method for preparing a sintered porous coated tube with enhanced flow boiling, where the coating slurry is applied by sealing the first end of the heat exchanger tube, pouring the slurry into the second end until it is full, and then opening the first end to release the excess slurry. All of these methods involve directly applying metal powder slurry to the surface of the heat exchanger tube. Due to the fluidity of the slurry, it is difficult to ensure the uniformity of the coating thickness using these methods. Furthermore, the structure of the porous layer obtained using these methods is relatively simple, limiting further improvement in the boiling heat transfer performance of the heat exchanger tube. Summary of the Invention

[0004] This invention provides a sintered high-flux heat exchange tube and its preparation method to solve the problems of poor uniformity of porous layer thickness and low boiling heat transfer performance in the prior art.

[0005] One of the objectives of this invention is to provide a sintered high-flux heat exchange tube, comprising: a heat exchange tube substrate and an asymmetric metal film layer on the surface of the substrate, wherein the asymmetric metal film layer comprises a coarse metal powder film layer and a fine metal powder film layer stacked on top of each other.

[0006] In the sintered high-flux heat exchange tube provided by this invention:

[0007] The thickness of the asymmetric metal film is 180–500 μm, preferably 250–400 μm;

[0008] The thickness of the coarse metal powder film is 100–400 μm, preferably 150–300 μm;

[0009] The thickness of the fine metal powder film is 80–200 μm, preferably 100–150 μm.

[0010] The present invention involves bonding a uniformly thick asymmetric metal film layer to the surface of a heat exchange tube, wherein the fine metal powder film layer in the asymmetric metal film layer is bonded to the surface of the substrate.

[0011] In the sintered high-flux heat exchange tube provided by this invention:

[0012] In the aforementioned coarse metal powder film, the particle size of the coarse metal powder is 50–100 μm;

[0013] In the fine metal powder film, the particle size of the fine metal powder is 20-50 μm;

[0014] The particle size ratio of the fine metal powder to the coarse metal powder is 1:(1.5-5), preferably 1:(2-3).

[0015] In the sintered high-flux heat exchange tube provided by the present invention, the material of the heat exchange tube substrate is not particularly limited, and can be a metal substrate commonly used in the art, preferably at least one of carbon steel, stainless steel, heat-resistant steel, copper, copper alloy, and titanium; the metal powder is selected from at least one of iron-based alloy, stainless steel, copper, copper alloy, and titanium.

[0016] The second objective of this invention is to provide a method for preparing the above-mentioned sintered high-flux heat exchange tube, comprising: attaching the asymmetric metal film layer to the surface of the heat exchange tube substrate, and sintering to obtain the sintered high-flux heat exchange tube.

[0017] The method for preparing the sintered high-flux heat exchange tube provided by this invention specifically includes the following steps:

[0018] (1) The surface of the heat exchange tube substrate is sandblasted, then cleaned and dried.

[0019] (2) After the additive is evenly dispersed in the solvent, coarse metal powder is added and stirred evenly to form a suspension containing coarse metal powder. After casting, a coarse metal powder film green body is prepared.

[0020] (3) After the additive is uniformly dispersed in the solvent, fine metal powder is added and stirred evenly to form a suspension containing fine metal powder. After casting, a fine metal powder film green body is prepared.

[0021] (4) The coarse metal powder film green blank obtained in step (2) and the fine metal powder film green blank obtained in step (3) are bonded and rolled together to obtain an asymmetric metal film green blank.

[0022] (5) Apply a layer of gel solution evenly to the surface of the heat exchange tube substrate after cleaning and drying, attach the fine metal powder film of the asymmetric metal film blank to the surface of the heat exchange tube substrate, press and dry the film surface.

[0023] (6) The heat exchange tube with an asymmetric metal film layer attached to its surface is sintered and cooled to obtain the sintered high-throughput heat exchange tube.

[0024] In step (1) of the preparation method of the sintered high-throughput heat exchange tube provided by the present invention, the sandblasting treatment is not particularly limited and a commonly used sandblasting process can be used; the surface of the heat exchange tube substrate after sandblasting can be cleaned by a conventional cleaning method, for example, the heat exchange tube substrate is placed in an ethanol solution for cleaning and dried at 50-60°C.

[0025] In steps (2) and (3) of the method for preparing the sintered high-flux heat exchange tube provided by the present invention:

[0026] The solvent in the suspension can be a commonly used water or organic solvent, preferably at least one of water, ethanol, butanone, cyclohexanone, and n-butanol;

[0027] The amount of solvent used in the suspension is not particularly limited, as long as it can form a suspension. Preferably, the content of solvent in the suspension is 30-40 wt%, the content of metal powder is 50-60 wt%, and the content of additives is 8-20 wt%.

[0028] The casting operation can be carried out using common casting methods, and then a doctor blade is used to evenly coat the film. The carrier used for casting can be a common film carrier, such as polyester, polyethylene, polypropylene, polytetrafluoroethylene, etc.

[0029] In the obtained coarse metal powder film green body, the weight ratio of coarse metal powder to additives is (2.5-7.5):1, preferably (4-6):1;

[0030] In the obtained fine metal powder film green body, the weight ratio of fine metal powder to additives is (2.5-7.5):1, preferably (4-6):1.

[0031] In the sintered high-flux heat exchange tube provided by the present invention, the additives include a binder, a plasticizer, and a pore-forming agent; preferably, the binder is selected from at least one of polyvinyl butyral, polyvinyl alcohol, and polyethylene oxide; the plasticizer is selected from at least one of polyethylene glycol, dibutyl phthalate, dioctyl phthalate, and glycerol; and the pore-forming agent is selected from at least one of polymethyl methacrylate, methylcellulose, and ethylcellulose; in the suspension, the content of the binder is 1-3 wt%, the content of the plasticizer is 2-5 wt%, and the content of the pore-forming agent is 5-10 wt%.

[0032] In step (4) of the preparation method of the sintered high-flux heat exchanger tube provided by the present invention, the method of bonding and rolling is not particularly limited, and the rolling method commonly used in the art can be adopted. Specifically, the following method can be adopted: take a coarse metal powder film green blank and a fine metal powder film green blank respectively, stack them with their rough surfaces facing each other, and place them between the rolls of a rolling mill for rolling. The thickness of the asymmetric metal film green blank obtained after bonding and rolling is 180-500 μm.

[0033] In step (5) of the preparation method of the sintered high-flux heat exchanger tube provided by this invention, the gel-like solution can be a commonly used gel-like solution in the art, such as polyvinyl butyral-ethanol solution, polyvinyl alcohol-water solution, polyethylene oxide-water solution, etc. In this invention, an asymmetric metal film green body is bonded to a heat exchanger tube substrate coated with the gel-like solution, then pressed with a shaped mold and dried at 60–100°C.

[0034] In step (6) of the method for preparing the sintered high-flux heat exchange tube provided by the present invention,

[0035] The sintering is carried out in a hydrogen atmosphere or a vacuum atmosphere;

[0036] The sintering process is as follows: first, the temperature is raised to 200-300℃ at a rate of 4-5℃ / min and held for 60-90min; then, the temperature is slowly raised to 400-500℃ at a rate of 1-2℃ / min and held for 60-90min; then, the temperature is rapidly raised to 1000-1300℃ at a rate of 8-10℃ / min and held for 60-90min; and finally, the temperature is cooled to below 60℃.

[0037] The sintered high-flux heat exchange tube provided by this invention has the following positive effects:

[0038] (1) The present invention uses a method of bonding a uniform metal film green sheet to the surface of the heat exchange tube and then pressing the metal film to the surface of the heat exchange tube with a shaped mold to prepare a surface metal porous layer, which ensures the uniformity of the porous layer thickness.

[0039] (2) In this invention, a fine metal powder film is bonded to the surface of a substrate. Due to the small particle size and low melting point of the fine metal powder, it is easier for the fine metal powder to form a strong metallurgical bond with the substrate surface under the same sintering conditions. Therefore, good bonding performance between the porous metal layer and the base tube is ensured.

[0040] (3) The porous metal layer prepared by this invention has a special asymmetric structure. The porous layer structure is fine on the side near the tube surface and relatively coarse on the side near the liquid medium. This asymmetric porous metal layer can greatly increase the number of vaporization nuclei and the frequency of bubble ejection, thus significantly enhancing boiling heat transfer and effectively improving the heat transfer efficiency of the heat exchange tube. Detailed Implementation

[0041] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0042] The testing instruments and conditions used in this embodiment are as follows:

[0043] Bonding performance test between porous layer and base tube:

[0044] The bonding performance between the porous layer and the base pipe is tested using the shear strength method, that is, the shear strength of the porous layer is used to evaluate the bonding strength between the porous layer and the base pipe. Shear strength refers to the ultimate ability of the porous layer to withstand axial shear force per unit area at the contact surface with the base pipe, and its calculation formula is as follows:

[0045]

[0046] In the formula, τ b denoted as the shear strength of the porous layer, F as the maximum load during the peeling of the porous layer, D as the outer diameter of the base tube, and W as the axial length of the porous layer.

[0047] Heat transfer performance test:

[0048] The heat transfer performance of the high-flux heat exchanger tubes was measured using a pool boiling test apparatus. The heat flux Q at various voltage values ​​can be obtained by multiplying the condensate flow rate m and the latent heat of vaporization γ by time t, i.e., Q = (m·γ) / t; the heat flux density q = Q / A; and the boiling heat transfer coefficient h = q / (t). w -t sat ); where A is the effective heat transfer area, t w t represents the temperature of the outer wall of the pipe. sat The temperature is the medium temperature.

[0049] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0050] Example 1

[0051] (1) The surface of the 316L stainless steel heat exchange tube substrate is sandblasted, then cleaned in an ethanol solution, and then dried at 50°C.

[0052] (2) Prepare a solution by adding 6g of polyvinyl butyral and 12g of dibutyl phthalate to 100g of ethanol. Add 15g of polymethyl methacrylate with an average particle size of 100μm and 150g of 316L stainless steel powder with a particle size of about 96μm to the solution. Stir for 40min to mix them thoroughly to obtain a suspension. Adjust the height of the scraper and use the scraper to evenly coat the suspension onto a polyester film coated with silicone oil. Let it stand for 30min and peel off the film to obtain a coarse metal powder film green body with a thickness of 300μm.

[0053] (3) Prepare a solution by adding 6g of polyvinyl butyral and 12g of dibutyl phthalate to 100g of ethanol. Add 15g of polymethyl methacrylate with an average particle size of 60μm and 150g of 316L stainless steel powder with a particle size of about 45μm to the solution. Stir for 40min to mix them thoroughly to obtain a suspension. Adjust the height of the scraper and use the scraper to evenly coat the suspension onto a polyester film coated with silicone oil. Let it stand for 30min and peel off the film to obtain a fine metal powder film green body with a thickness of 150μm.

[0054] (4) The coarse metal powder and fine metal powder film green blanks are stacked and rolled to obtain an asymmetric metal film green blank with a thickness of 380 μm.

[0055] (5) Apply a layer of polyvinyl butyral-ethanol solution evenly to the surface of the 316L stainless steel heat exchange tube, and use fine metal powder film of asymmetric metal film blank to adhere to the surface of the heat exchange tube, press and dry the film surface.

[0056] (6) The 316L heat exchange tube with an asymmetric metal film layer attached to its surface is placed in a hydrogen sintering furnace for sintering. The specific sintering process is as follows: first, the temperature is raised to 240℃ at a rate of 4℃ / min and held for 60min, then the temperature is slowly raised to 450℃ at a rate of 2℃ / min and held for 60min, and then the temperature is rapidly raised to 1300℃ at a rate of 8℃ / min and held for 60min. After cooling, a sintered high-flux heat exchange tube is obtained.

[0057] The porous layer of the prepared 316L stainless steel-based high-flux heat exchanger tube has a thickness of 350 μm and a porosity of 61%. The bonding strength between the porous layer and the base tube is 37 MPa. When the heat flux density is 45.6 kW / m³... 2 At that time, the boiling heat transfer coefficient of the high-flux heat exchanger tube in deionized water was 26.8 kW / (m²). 2 ·K).

[0058] Example 2

[0059] (1) The surface of the B10 copper-nickel alloy heat exchange tube substrate is sandblasted, then cleaned in an ethanol solution, and then dried at 50°C.

[0060] (2) Prepare a solution by adding 7g of polyvinyl alcohol and 10g of glycerol to 100g of water. Add 18g of polymethyl methacrylate with an average particle size of 90μm and 160g of B10 copper-nickel alloy powder with a particle size of about 100μm to the solution. Stir for 40min to mix them thoroughly to obtain a suspension. Adjust the height of the scraper and use the scraper to evenly coat the suspension onto a polyester film coated with silicone oil. Let it stand for 30min and peel off the film to obtain a coarse metal powder film green body with a thickness of 280μm.

[0061] (3) Prepare a solution by adding 6g of polyvinyl alcohol and 9g of glycerol to 100g of water. Add 19g of polymethyl methacrylate with an average particle size of 30μm and 150g of B10 copper-nickel alloy powder with a particle size of about 35μm to the solution. Stir for 40min to mix them thoroughly to obtain a suspension. Adjust the height of the scraper and use the scraper to evenly coat the suspension onto a polyester film coated with silicone oil. Let it stand for 30min and peel off the film to obtain a fine metal powder film green body with a thickness of 140μm.

[0062] (4) The coarse metal powder and fine metal powder film green blanks are stacked and rolled to obtain an asymmetric metal film green blank with a thickness of 350 μm.

[0063] (5) Apply a layer of polyvinyl alcohol-water solution evenly to the surface of the heat exchange tube, and use the fine metal powder film of the asymmetric metal film green blank to adhere to the surface of the heat exchange tube, press and dry the film surface.

[0064] (6) The B10 copper-nickel alloy heat exchange tube with an asymmetric metal film layer on its surface is placed in a hydrogen sintering furnace for sintering. The specific sintering process is as follows: first, the temperature is raised to 220℃ at a rate of 4℃ / min and held for 60min, then the temperature is slowly raised to 420℃ at a rate of 1℃ / min and held for 60min, and then the temperature is rapidly raised to 1050℃ at a rate of 8℃ / min and held for 60min. After cooling, a sintered high-flux heat exchange tube is obtained.

[0065] The porous layer of the prepared B10 copper-nickel alloy-based high-flux heat exchanger tube has a thickness of 320 μm and a porosity of 58%. The bonding strength between the porous layer and the base tube is 39 MPa. When the heat flux density is 45.6 kW / m³... 2 At that time, the boiling heat transfer coefficient of the high-flux heat exchanger tube in deionized water was 26.5 kW / (m²). 2 ·K).

[0066] Example 3

[0067] (1) The surface of the titanium heat exchanger tube substrate is sandblasted, then cleaned in an ethanol solution, and then dried at 50°C.

[0068] (2) Prepare a solution by adding 8g of polyvinyl butyral and 10g of dioctyl phthalate to 100g of ethanol. Add 16g of polymethyl methacrylate with an average particle size of 90μm and 170g of titanium powder with a particle size of about 90μm to the solution. Stir for 40min to mix them thoroughly to obtain a suspension. Adjust the height of the scraper and use the scraper to evenly coat the suspension onto a polyester film coated with silicone oil. Let it stand for 30min and peel off the film to obtain a coarse metal powder film green body with a thickness of 270μm.

[0069] (3) Prepare a solution by adding 6g of polyvinyl butyral and 11g of dioctyl phthalate to 100g of ethanol. Add 18g of polymethyl methacrylate with an average particle size of 40μm and 160g of titanium powder with a particle size of about 45μm to the solution. Stir for 40min to mix them thoroughly to obtain a suspension. Adjust the height of the scraper and use the scraper to evenly coat the suspension onto a polyester film coated with silicone oil. Let it stand for 30min and peel off the film to obtain a fine metal powder film green body with a thickness of 120μm.

[0070] (4) The coarse metal powder and fine metal powder film green blanks are stacked and rolled to obtain an asymmetric metal film green blank with a thickness of 320 μm.

[0071] (5) Apply a layer of polyvinyl butyral-ethanol solution evenly to the surface of the heat exchange tube, and use the fine metal powder film of the asymmetric metal film green blank to adhere to the surface of the heat exchange tube, press and dry the film surface.

[0072] (6) The titanium heat exchange tube with an asymmetric metal film attached to its surface is placed in a vacuum sintering furnace for sintering. The specific sintering process is as follows: first, the temperature is raised to 250℃ at a rate of 5℃ / min and held for 60min; then, the temperature is slowly raised to 450℃ at a rate of 1℃ / min and held for 60min; then, the temperature is rapidly raised to 1100℃ at a rate of 8℃ / min and held for 60min. After cooling, a sintered high-flux heat exchange tube is obtained.

[0073] The porous layer of the prepared titanium-based high-flux heat exchanger tube has a thickness of 300 μm and a porosity of 59%. The bonding strength between the porous layer and the base tube is 35 MPa. When the heat flux density is 45.6 kW / m³... 2 At that time, the boiling heat transfer coefficient of the high-flux heat exchanger tube in deionized water was 25.3 kW / (m²). 2 ·K).

[0074] Comparative Example 1

[0075] (1) The surface of the 316L stainless steel heat exchange tube substrate is sandblasted, then cleaned and dried.

[0076] (2) Prepare a solution by adding 6g of polyvinyl butyral and 12g of dibutyl phthalate to 100g of ethanol. Add 15g of polymethyl methacrylate with an average particle size of 100μm, 100g of 316L stainless steel powder with a particle size of about 96μm and 50g of 316L stainless steel powder with a particle size of about 45μm to the solution and stir for 40min to mix them thoroughly to obtain a suspension. Adjust the height of the scraper and use the scraper to evenly coat the suspension onto a polyester film coated with silicone oil. Let it stand for 30min and peel off the film to obtain a metal powder film green body with a thickness of 380μm.

[0077] (3) Apply a layer of polyvinyl butyral-ethanol solution evenly to the surface of the 316L stainless steel heat exchange tube, attach the metal film green to the surface of the heat exchange tube, press and dry the film surface.

[0078] (4) The 316L heat exchange tube with the metal film attached to the surface is placed in a hydrogen sintering furnace for sintering. The specific sintering process is as follows: first, the temperature is raised to 240℃ at a rate of 4℃ / min and held for 60min, then the temperature is slowly raised to 450℃ at a rate of 2℃ / min and held for 60min, and then the temperature is rapidly raised to 1300℃ at a rate of 8℃ / min and held for 60min. After cooling, the sintered high-flux heat exchange tube is obtained.

[0079] The porous layer of the prepared 316L stainless steel-based high-flux heat exchanger tube has a thickness of 350 μm and a porosity of 60%. The bonding strength between the porous layer and the base tube is 28 MPa. When the heat flux density is 45.6 kW / m³... 2 At that time, the boiling heat transfer coefficient of the high-flux heat exchanger tube in deionized water was 22.8 kW / (m²). 2 ·K).

[0080] Comparative Example 2

[0081] (1) The surface of the 316L stainless steel heat exchange tube substrate is sandblasted, then cleaned and dried.

[0082] (2) Prepare a solution by adding 6g of polyvinyl butyral and 12g of dibutyl phthalate to 100g of ethanol. Add 15g of polymethyl methacrylate with an average particle size of 100μm and 150g of 316L stainless steel powder with a particle size of about 96μm to the solution. Stir for 40min to mix them thoroughly to obtain a suspension. Adjust the height of the scraper and use the scraper to evenly coat the suspension onto a polyester film coated with silicone oil. Let it stand for 30min and peel off the film to obtain a coarse metal powder film green body with a thickness of 370μm.

[0083] (3) Apply a layer of polyvinyl butyral-ethanol solution evenly to the surface of the 316L stainless steel heat exchange tube, attach the metal film green to the surface of the heat exchange tube, press and dry the film surface.

[0084] (4) The 316L heat exchange tube with the metal film attached to the surface is placed in a hydrogen sintering furnace for sintering. The specific sintering process is as follows: first, the temperature is raised to 240℃ at a rate of 4℃ / min and held for 60min, then the temperature is slowly raised to 450℃ at a rate of 2℃ / min and held for 60min, and then the temperature is rapidly raised to 1300℃ at a rate of 8℃ / min and held for 60min. After cooling, the sintered high-flux heat exchange tube is obtained.

[0085] The porous layer of the prepared 316L stainless steel-based high-flux heat exchanger tube has a thickness of 350 μm and a porosity of 58%. The bonding strength between the porous layer and the base tube is 23 MPa. When the heat flux density is 45.6 kW / m³... 2 At that time, the boiling heat transfer coefficient of the high-flux heat exchanger tube in deionized water was 22.1 kW / (m²). 2 ·K).

[0086] Comparative Example 3

[0087] (1) The surface of the 316L stainless steel heat exchange tube substrate is sandblasted, then cleaned and dried.

[0088] (2) Prepare a solution by adding 6g of polyvinyl butyral and 12g of dibutyl phthalate to 100g of ethanol. Add 15g of polymethyl methacrylate with an average particle size of 60μm and 150g of 316L stainless steel powder with a particle size of about 45μm to the solution. Stir for 40min to mix them thoroughly to obtain a suspension. Adjust the height of the scraper and use the scraper to evenly coat the suspension onto a polyester film coated with silicone oil. Let it stand for 30min and peel off the film to obtain a fine metal powder film green body with a thickness of 390μm.

[0089] (3) Apply a layer of polyvinyl butyral-ethanol solution evenly to the surface of the 316L stainless steel heat exchange tube, attach the metal film green to the surface of the heat exchange tube, press and dry the film surface.

[0090] (4) The 316L heat exchange tube with the metal film attached to the surface is placed in a hydrogen sintering furnace for sintering. The specific sintering process is as follows: first, the temperature is raised to 240℃ at a rate of 4℃ / min and held for 60min, then the temperature is slowly raised to 450℃ at a rate of 2℃ / min and held for 60min, and then the temperature is rapidly raised to 1300℃ at a rate of 8℃ / min and held for 60min. After cooling, the sintered high-flux heat exchange tube is obtained.

[0091] The porous layer of the prepared 316L stainless steel-based high-flux heat exchanger tube has a thickness of 350 μm and a porosity of 50%. The bonding strength between the porous layer and the base tube is 36 MPa. When the heat flux density is 45.6 kW / m³... 2 At that time, the boiling heat transfer coefficient of the high-flux heat exchanger tube in deionized water was 19.8 kW / (m²). 2 ·K).

[0092] The performance of the sintered high-flux heat exchange tubes prepared in Examples 1-3 and Comparative Examples 1-3 is compared, as shown in the table below:

[0093]

[0094] Based on the above comparative analysis, it can be seen that the high-flux heat exchange tube with asymmetric surface porous layer structure prepared by the present invention has uniform porous layer thickness, high porosity, high bonding strength between porous layer and substrate, and excellent boiling heat transfer performance.

Claims

1. A method for preparing a sintered high-flux heat exchange tube, characterized in that, The preparation method includes the following steps: (1) The surface of the heat exchange tube substrate is sandblasted, then cleaned and dried; (2) After the additive is evenly dispersed in the solvent, coarse metal powder is added and stirred evenly to form a suspension containing coarse metal powder. After casting, a coarse metal powder film green body is prepared. (3) After the additive is evenly dispersed in the solvent, fine metal powder is added and stirred evenly to form a suspension containing fine metal powder. After casting, a green body of fine metal powder film is prepared. (4) The coarse metal powder film green blank obtained in step (2) and the fine metal powder film green blank obtained in step (3) are bonded and rolled together to obtain an asymmetric metal film green blank. (5) Apply a layer of gel solution evenly to the surface of the heat exchange tube substrate after cleaning and drying, attach the fine metal powder film of the asymmetric metal film blank to the surface of the heat exchange tube substrate, press and dry the film surface. (6) The heat exchange tube with an asymmetric metal film layer attached to its surface is sintered and cooled to obtain a sintered high-flux heat exchange tube. The sintering is carried out in a hydrogen atmosphere or a vacuum atmosphere; The sintering steps are as follows: first, the temperature is raised to 200-300℃ at a rate of 4-5℃ / min and held for 60-90min; then, the temperature is slowly raised to 400-500℃ at a rate of 1-2℃ / min and held for 60-90min; then, the temperature is rapidly raised to 1000-1300℃ at a rate of 8-10℃ / min and held for 60-90min; finally, the temperature is cooled to below 60℃. The sintered high-throughput heat exchange tube includes: a heat exchange tube substrate and an asymmetric metal film layer on the surface of the substrate, wherein the asymmetric metal film layer includes a coarse metal powder film layer and a fine metal powder film layer stacked on top of each other.

2. The preparation method according to claim 1, characterized in that, The thickness of the asymmetric metal film is 180~500µm; and / or, The thickness of the coarse metal powder film is 100~400µm; and / or, The thickness of the fine metal powder film is 80~200µm; and / or, The fine metal powder film in the asymmetric metal film layer is bonded to the surface of the substrate.

3. The preparation method according to claim 2, characterized in that, The thickness of the asymmetric metal film is 250~400µm; and / or, The thickness of the coarse metal powder film is 150~300µm; and / or, The thickness of the fine metal powder film is 100~150µm.

4. The preparation method according to claim 1, characterized in that, In the aforementioned coarse metal powder film, the particle size of the coarse metal powder is 50~100µm; and / or, In the aforementioned fine metal powder film, the particle size of the fine metal powder is 20~50µm; and / or, The particle size ratio of the fine metal powder to the coarse metal powder is 1:(1.5~5).

5. The preparation method according to claim 4, characterized in that, The particle size ratio of the fine metal powder to the coarse metal powder is 1:(2~3).

6. The preparation method according to claim 1, characterized in that, The material of the heat exchange tube substrate is selected from at least one of carbon steel, stainless steel, heat-resistant steel, copper, and titanium; and / or, The metal powder is selected from at least one of iron-based alloys, copper, and titanium.

7. The preparation method according to claim 1, characterized in that, The solvent in the suspension is selected from at least one of water, ethanol, butanone, cyclohexanone, and n-butanol; and / or, The suspension contains 30-40 wt% solvent, 50-60 wt% metal powder, and 8-20 wt% additives.

8. The preparation method according to claim 1, characterized in that, The additives include binders, plasticizers, and pore-forming agents.

9. The preparation method according to claim 8, characterized in that, The adhesive is selected from at least one of polyvinyl butyral, polyvinyl alcohol, and polyethylene oxide; and / or, The plasticizer is selected from at least one of polyethylene glycol, dibutyl phthalate, dioctyl phthalate, and glycerol; and / or, The pore-forming agent is selected from at least one of polymethyl methacrylate, methylcellulose, and ethylcellulose; and / or, The suspension contains 1-3 wt% binder, 2-5 wt% plasticizer, and 5-10 wt% pore-forming agent.

10. The preparation method according to claim 1, characterized in that, In the aforementioned coarse metal powder film green body, the weight ratio of coarse metal powder to additives is (2.5~7.5):1; and / or, In the aforementioned fine metal powder film green body, the weight ratio of fine metal powder to additives is (2.5~7.5):

1.

11. The preparation method according to claim 10, characterized in that, In the aforementioned coarse metal powder film green body, the weight ratio of coarse metal powder to additives is (4~6):1; and / or, In the aforementioned fine metal powder film green body, the weight ratio of fine metal powder to additives is (4~6):1.

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