Self-cleaning heat exchanger tube insert with super-smooth surface and method

Abstract

The invention discloses a self-cleaning heat exchanger in-tube insert with a super-smooth surface and a method, solves the problem that the surface of the in-tube insert of a heat exchange tube in the prior art is easy to scale at different degrees, and has the beneficial effect of realizing a self-cleaning function of the in-tube insert. According to the specific scheme, the self-cleaning heat exchanger in-pipe insert with the super-smooth surface comprises an insert body, the surface of the insert body is provided with a polydimethylsiloxane high-molecular polymer, lubricating oil is sprayed to form the super-smooth surface in the annular direction of the insert body, and the water contact angle of the super-smooth surface is larger than 100 degrees. The preparation method comprises the following steps: mixing dimethyldimethoxysilane with concentrated sulfuric acid to form a silane solution, and soaking the pretreated insert body in the silane solution for a set time; the soaked insert body is cleaned, and a to-be-treated insert body with a polydimethylsiloxane high-molecular polymer grafting layer is obtained; and spraying the lubricating oil.

Description

Technical Field

[0001] This invention relates to the field of heat exchanger technology, and in particular to a self-cleaning heat exchanger tube insert and method having an ultra-smooth surface. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Heat exchangers, as general-purpose devices for exchanging heat between hot and cold fluids, are widely used process equipment in many industrial sectors such as chemical, power, aerospace, and metallurgy. Typically, in the construction of a chemical plant, heat exchangers account for approximately 11% to 40% of the total investment. Their sophistication, rationality, and operational reliability directly affect the quality, quantity, and cost of the final product.

[0004] Shell-and-tube heat exchangers are currently the most widely used type of heat exchanger. To improve the heat exchange efficiency of shell-and-tube heat exchangers, common engineering methods include optimizing the design of the heat exchange tubes and installing inserts inside the tubes. Among these methods, installing inserts is simple and low-cost, and common insert shapes include ribbon-type, spring-plate type, and spiral blade type. However, as the core component of heat exchange equipment, the heat exchange tubes are prone to scaling problems to varying degrees after long-term operation, leading to a decrease in heat transfer efficiency, affecting the safe operation of the equipment, and increasing the cost of cleaning and maintenance. Therefore, the development of self-cleaning insert technology is urgently needed.

[0005] Superlubricated surfaces are low-slip surfaces designed with inspiration from the surface structure and function of pitcher plants and earthworms. On one hand, superlubricated surfaces possess a molecularly smooth liquid interface, lacking fixed "anchor points" for contaminants to adhere firmly. On the other hand, the contact area between solid contaminants and the lubricating fluid layer on the superlubricated surface is very small, minimizing adhesion forces such as van der Waals forces. However, in the current technology for inserts into heat exchanger tubes, no superlubricated surfaces have been introduced because existing superlubricated material preparation processes require roughening the substrate before forming the superlubricated surface, resulting in low processing efficiency. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a self-cleaning heat exchanger tube insert with an ultra-smooth surface, reducing the deposition of contaminants in the fluid on the tube insert, enabling the tube insert to have a self-cleaning function, thereby reducing the cleaning cost of the heat exchanger tube insert and improving heat exchange efficiency.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: A self-cleaning heat exchanger tube insert with an ultra-slippery surface includes an insert body, the surface of which is coated with a polydimethylsiloxane polymer and coated with lubricating oil to form an ultra-slippery surface in the circumferential direction of the insert body, wherein the water contact angle of the ultra-slippery surface is greater than 100°.

[0008] Secondly, the present invention also provides a method for preparing a self-cleaning heat exchanger tube insert with an ultra-smooth surface, comprising the following: Pre-process the insert itself; Dimethyldimethoxysilane was mixed with concentrated sulfuric acid to form a silane solution. The pretreated insert was then immersed in the silane solution for a set time. The soaked insert body is cleaned and dried to obtain the insert body to be treated with a polydimethylsiloxane polymer graft layer. Lubricating oil is sprayed onto the insert body with a polymer graft layer to be treated, and after the lubricating oil is sprayed, an insert body with an ultra-smooth surface is obtained.

[0009] The method for preparing a self-cleaning heat exchanger tube insert with an ultra-smooth surface as described above, wherein dimethyldimethoxysilane and concentrated sulfuric acid are mixed at a volume ratio of 5 to 6:1 to form the silane solution.

[0010] The method for preparing a self-cleaning heat exchanger tube insert with an ultra-smooth surface as described above involves immersing the pretreated insert body in the silane solution for 1-3 minutes.

[0011] The preparation method of a self-cleaning heat exchanger tube insert with an ultra-smooth surface as described above involves performing a second ultrasonic cleaning of the soaked insert body with anhydrous ethanol, and then drying it in a drying oven at a set temperature for 3-5 minutes.

[0012] The method for preparing a self-cleaning heat exchanger tube insert with an ultra-smooth surface, as described above, includes the following pretreatment of the insert body: The insert body is ultrasonically cleaned in anhydrous ethanol for a set time, and the surface of the workpiece is dried with a compressed air gun. There is no need to roughen or otherwise roughen the insert body.

[0013] The method for preparing a self-cleaning heat exchanger tube insert with an ultra-slippery surface, as described above, includes spraying lubricating oil onto the insert body with a polymer graft layer, comprising the following steps: Lubricating oil is sprayed using a spray gun at an air pressure of 0.4-0.6 MPa. During spraying, the distance between the nozzle and the substrate to be treated with a polymer grafted layer is 15-20 cm. The moving speed of the spray gun is 30-40 cm / s. The angle between the nozzle and the substrate to be treated with a polymer grafted layer is 90°.

[0014] The method for preparing a self-cleaning heat exchanger tube insert with an ultra-smooth surface as described above uses one or more of trifluoropropylmethyl silicone oil, methyl silicone oil, or paraffin oil as the lubricating oil.

[0015] As described above, in the method for preparing a self-cleaning heat exchanger tube insert with an ultra-smooth surface, after the lubricating oil is sprayed, the insert body is placed in an acetone solution for ultrasonic cleaning for a set time to remove excess lubricating oil coating from the surface.

[0016] In the method for preparing a self-cleaning heat exchanger tube insert with an ultra-smooth surface as described above, the concentration of the concentrated sulfuric acid is 98%.

[0017] The beneficial effects of the present invention are as follows: 1) In this invention, polydimethylsiloxane polymer is grafted onto the surface of the tube insert matrix and further coated with lubricating oil to form a super-slippery surface, achieving an anti-adhesion and desorption effect. The treated super-slippery surface can simultaneously repel calcium carbonate scale, silt and water. The water contact angle of the final tube insert with the super-slippery surface is greater than 100°, which can further reduce the attachment sites of pollutants.

[0018] 2) The present invention uses a method for preparing an insert in a tube. First, the insert body is pretreated without roughening. Dimethyldimethoxysilane is mixed with concentrated sulfuric acid to form a silane solution, which facilitates the rapid formation of the silane solution. After the solution is formed, the insert body is soaked and dried to obtain the insert body to be treated. Finally, a lubricating oil is sprayed to obtain an insert body with an ultra-slippery surface. This results in the final tube insert having a roll-off angle of less than 4° for calcium carbonate scale, silt, and water, making it difficult for calcium carbonate scale, silt, and water to roll off the original tube insert surface. The final tube insert has a water contact angle greater than 100°, effectively reducing the adhesion points of contaminants.

[0019] 3) In the process of spraying lubricating oil onto the insert body with a polymer graft layer in this invention, a spray gun is used to spray the lubricating oil. By limiting the air pressure, moving speed and angle of the spray gun, the water contact angle of the super-slippery surface can be greater than 100°, which helps to reduce the adhesion sites of contaminants.

[0020] 4) This invention provides a method for preparing an insert with a super-slippery surface, which can quickly form a super-slippery surface on the surface of the insert body. This effectively reduces the deposition of contaminants in the fluid on the insert during operation, giving the insert a self-cleaning function. This reduces the cleaning cost of the heat exchanger tube insert and improves heat exchange efficiency. The preparation time is not too long, the preparation method is simple and reasonable, and the final super-slippery surface is also heat-resistant, meeting the environmental requirements for the use of heat exchanger tube inserts. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 This is an enlarged comparison image of the surface of a self-cleaning heat exchanger tube insert with an ultra-smooth surface according to one or more embodiments of the present invention, and a conventional tube insert.

[0023] Figure 2 This is a flowchart of a method for preparing a self-cleaning heat exchanger tube insert with an ultra-smooth surface according to one or more embodiments of the present invention.

[0024] Figure 3 This is a comparison diagram of the roll-off angle of a self-cleaning heat exchanger tube insert with an ultra-smooth surface according to one or more embodiments of the present invention against calcium carbonate scale, silt and water, compared to existing tube inserts.

[0025] Figure 4 This is a comparison diagram of the water contact angle of the super-slippery surface of a self-cleaning heat exchanger tube insert with a super-slippery surface according to one or more embodiments of the present invention, compared with that of existing tube inserts.

[0026] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only. Detailed Implementation

[0027] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0028] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. As described in the background section, existing technologies are prone to scaling of varying degrees on the surface of heat exchanger tube inserts. To address this technical problem, this invention proposes a self-cleaning heat exchanger tube insert with an ultra-smooth surface.

[0029] Example 1 In a typical embodiment of the present invention, a self-cleaning heat exchanger tube insert with an ultra-slippery surface includes an insert body, the surface of which is coated with a polydimethylsiloxane polymer and coated with lubricating oil to form an ultra-slippery surface in the circumferential direction of the insert body, wherein the water contact angle of the ultra-slippery surface is greater than 100°.

[0030] refer to Figure 1 As shown in the diagram, when magnified, the insert body (substrate a), i.e., the existing metal materials (stainless steel, carbon steel, copper and copper alloys) such as ribbon type, spring plate type and spiral blade type, has many pits on the surface, making it easy for scale to form. However, when polydimethylsiloxane polymer is grafted onto the surface of the tube insert (b), a microstructure similar to velvet is formed on the surface. Furthermore, lubricating oil is sprayed to form a super-slippery surface, achieving an anti-adhesion and desorption effect. The treated super-slippery surface can simultaneously repel calcium carbonate scale, silt and water. The water contact angle of the super-slippery surface is greater than 100°, which can further reduce the adhesion sites of pollutants. The tube insert formed in this way is not easy to form scale during operation and has the advantages of easy cleaning and high heat transfer efficiency.

[0031] Example 2 This embodiment discloses a method for preparing a self-cleaning heat exchanger tube insert with an ultra-smooth surface, including the following: Pre-treatment of the surface of the insert body: The insert body is ultrasonically cleaned in anhydrous ethanol for a set time, such as 15 minutes, and the workpiece surface is dried with a compressed air gun; there is no need to roughen or otherwise roughen the insert body, which facilitates the rapid forming of an ultra-smooth surface. Surface-grafted PDMS polydimethylsiloxane polymer layer: Dimethyldimethoxysilane and concentrated sulfuric acid (98%) were mixed uniformly at a volume ratio of 5-6:1 to form a silane solution, which facilitated rapid formation of the silane solution. The pretreated insert was then immersed in the silane solution for 1-3 minutes. Too much concentrated sulfuric acid would severely corrode the insert inside the tube, while too little would not achieve the desired catalytic effect. Strict control of the proportion and concentration of concentrated sulfuric acid was essential to ensure a balance between catalytic effect and material protection. Experiments showed that maintaining a volume ratio of concentrated sulfuric acid to dimethyldimethoxysilane of 5-6:1 effectively promoted the grafting reaction while avoiding excessive corrosion of the insert. The silane under the catalysis of concentrated sulfuric acid underwent accelerated hydrolysis, and the resulting silanols underwent a condensation reaction to form polymers. After pretreatment, the hydroxyl groups of the insert are exposed. The insert is then immersed in a silane solution, where the hydroxyl groups react with the polymer to form covalent bonds, resulting in a PDMS graft layer on the surface. The immersed insert is then subjected to a second ultrasonic cleaning with anhydrous ethanol and dried in a drying oven at a set temperature, such as 65°C, for 3-5 minutes to obtain the insert to be treated with a PDMS polydimethylsiloxane polymer graft layer.

[0032] In some examples, a mixture of dimethyldimethoxysilane and concentrated sulfuric acid is placed in a constant-temperature water bath, with the temperature controlled between 40°C and 50°C, and the reaction is continuously stirred for 4 to 6 hours to ensure that the dimethyldimethoxysilane is fully hydrolyzed and forms a stable polydimethylsiloxane precursor. Subsequently, the treated insert is immersed in the reaction solution, and polydimethylsiloxane is grafted onto its surface through chemical bonding. During this process, the immersion time must be strictly controlled, typically 30 to 40 minutes, to avoid an excessively thick polymer layer affecting subsequent spraying effects and thermal conductivity. After grafting, the insert is removed, and the surface is rinsed with deionized water to remove any residual reaction solution, followed by nitrogen purging and drying to ensure no impurities remain on the surface, preparing it for the next step of lubricant spraying.

[0033] Lubricating oil spraying Lubricating oils such as trifluoropropylmethyl silicone oil, methyl silicone oil, or paraffin oil are sprayed onto the surface of the insert substrate with a polymer graft layer using an existing spray gun. Since both PDMS and silicone oil have siloxane backbones, PDMS exhibits a strong affinity for silicone oil. This affinity not only improves the uniformity of the lubricating layer but also enhances its durability, ensuring stable performance over extended use. Furthermore, the sprayed insert substrate requires appropriate curing treatment, typically by allowing it to stand at room temperature for a set time or by other means, to further improve the adhesion and stability of the lubricating layer. Ultimately, this results in an insert surface with excellent super-lubricating properties, laying a solid foundation for subsequent applications.

[0034] During the spraying process, the distance, angle, and spraying speed of the spray gun need to be precisely controlled to ensure that the lubricating oil can evenly cover the entire surface, avoiding localized areas of excessive or insufficient thickness. Specifically, the air pressure for spraying is generally set to 0.4 MPa to 0.6 MPa; the distance between the nozzle and the workpiece during spraying is 15 cm to 20 cm; the moving speed of the spray gun is 30 cm to 40 cm / second; and the angle between the nozzle and the workpiece is 90°. After spraying, the workpiece is ultrasonically cleaned in acetone solution for 5 minutes to remove excess lubricating oil coating from the surface. By limiting the relevant parameters during spraying, the roll-off angle of the insert body against calcium carbonate scale, mud, and water is less than 4°, and the water contact angle of the super-slippery surface is greater than 100°, thereby reducing the adhesion sites of contaminants.

[0035] The method for preparing a tube insert with a super-slippery surface provided in this embodiment can form a super-slippery surface on the tube insert surface without special tools. It is applicable to surfaces with complex morphologies of tube inserts, and is compatible with any material of the tube insert. The overall reaction speed is fast, the cost is low, and calcium carbonate scale, silt, and water easily slide off the super-slippery surface. (Reference) Figure 3 As shown, compared to existing tube inserts without a super-slippery surface, tube inserts with a super-slippery surface exhibit a roll-off angle of less than 4° for calcium carbonate scale, silt, and water, making it difficult for these substances to roll off the original tube insert surface. (Reference) Figure 4 As shown, the designed tube inserts with super-slippery surfaces all have water contact angles greater than 100°, while the original surface water contact angle of existing tube inserts is less than 95°. Increasing the contact angle reduces the adhesion sites for contaminants. Therefore, because calcium carbonate scale, silt, and water do not easily slide off the super-slippery surface, the tube inserts with super-slippery surfaces have a self-cleaning function, effectively preventing the reduction in heat exchange efficiency caused by scaling on the surface of the heat exchanger tube inserts.

[0036] Moreover, the process is simple and facilitates the mass production of heat exchanger tube inserts.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A self-cleaning heat exchanger tube insert having a super-slippery surface, characterized in that, The insert body is provided with a polydimethylsiloxane polymer on the surface and is sprayed with lubricating oil to form a super-smooth surface around the insert body, and the water contact angle of the super-smooth surface is greater than 100°.

2. A method of preparing a self-cleaning heat exchanger tube insert with super- slippery surface according to claim 1, characterized in that, The application relates to an insert body with a super-smooth surface. The insert body is pretreated; Dimethyl dimethoxy silane is mixed with concentrated sulfuric acid to form a silane solution, and the pretreated insert body is soaked in the silane solution for a set time. The pretreated insert body is cleaned and dried to obtain a to-be-treated insert body with a polydimethylsiloxane polymer grafted layer. The to-be-treated insert body with the polymer grafted layer is sprayed with lubricating oil, and the insert body with a super-smooth surface is obtained after the lubricating oil is sprayed.

3. A method of preparing a self-cleaning heat exchanger tube insert with super- slippery surface according to claim 2, characterized in that, The dimethyl dimethoxy silane is mixed with the concentrated sulfuric acid at a volume ratio of 5-6:1 to form the silane solution.

4. A method of preparing a self-cleaning heat exchanger tube insert with super- slippery surface according to claim 2, characterized in that, The pretreated insert body is soaked in the silane solution for 1-3 minutes.

5. A method of preparing a self-cleaning heat exchanger tube insert with super- slippery surface as claimed in claim 2, wherein, The soaked insert body is cleaned by ultrasonic cleaning with anhydrous ethanol and is dried in a drying box at a set temperature for 3-5 minutes.

6. A method of preparing a self-cleaning heat exchanger tube insert with super- slippery surface as claimed in claim 2, wherein, The pretreatment of the insert body includes the following steps: The insert body is ultrasonically cleaned in anhydrous ethanol for a set time, and the surface of the workpiece is blown dry with a compressed air gun.

7. A method of preparing a self-cleaning heat exchanger tube insert with super- slippery surface as claimed in claim 2, wherein, The spraying of the lubricating oil on the to-be-treated insert body with the polymer grafted layer includes the following steps: The lubricating oil is sprayed by using a spray gun, and the air pressure of the spraying is 0.4-0.6 MPa; when spraying, the distance between the nozzle and the to-be-treated insert body with the polymer grafted layer is 15-20 cm; the moving speed of the spray gun is 30-40 cm / s; and the angle between the nozzle and the to-be-treated insert body with the polymer grafted layer is 90°.

8. A method of preparing a self-cleaning heat exchanger tube insert with super- slippery surface according to claim 2, wherein, The lubricating oil is one or more of trifluoropropyl methyl silicone oil, methyl silicone oil or paraffin oil.

9. A method of preparing a self-cleaning heat exchanger tube insert with super- slippery surface according to claim 2, characterized in that, After the lubricating oil is sprayed, the insert body is placed in an acetone solution for ultrasonic cleaning for a set time to remove the excess lubricating oil coating on the surface.

10. A method of preparing a self-cleaning heat exchanger tube insert with super- slippery surface as claimed in claim 2, wherein, The concentration of the concentrated sulfuric acid is 98%.

Images