Heat exchanger and composite material for a heat exchanger

Abstract

The heat exchanger provided by the application has a channel for fluid flow, and the heat exchanger comprises a base body and a hydrophobic coating layer covering at least part of the surface of the base body, the hydrophobic coating layer comprises a low-surface-energy silane material and a filler dispersed in the low-surface-energy silane material, and the filler comprises at least two kinds of particles, and the shapes of the at least two kinds of particles are different. The particles of different shapes are compounded, so that the particles have a good filling effect in the hydrophobic coating layer, which is beneficial to increasing the compactness of the coating layer, increasing the barrier effect of the hydrophobic coating layer on the corrosive medium, and improving the corrosion resistance of the heat exchanger. The composite material provided by the application comprises a solvent, a low-surface-energy silane material and a filler, the filler comprises at least two kinds of particles, and the shapes of the at least two kinds of particles are different. The composite material forms a corrosion-resistant coating layer containing particles of at least two shapes, thereby improving the corrosion resistance of the heat exchanger.

Description

Technical Field

[0001] This invention relates to the field of heat exchange device technology, and more particularly to a heat exchanger and a composite material for the heat exchanger. Background Technology

[0002] In related technologies, hydrophobic sols are coated onto the surface of heat exchangers to form hydrophobic coatings. These coatings create a larger contact angle for corrosive solutions on the heat exchanger surface, making them less prone to spreading and reducing the direct contact area between the corrosive solution and the heat exchanger surface. Furthermore, the hydrophobic coating itself also provides a certain barrier against corrosive media. Therefore, hydrophobic coatings can improve the corrosion resistance of heat exchangers. Typically, hydrophobic coatings formed from hydrophobic sols inevitably contain some micropores or voids. To increase the density and improve the barrier effect of the hydrophobic coating, fillers can be added to the hydrophobic sol to enhance its density. Currently, most research focuses on the effect of filler content on the anti-corrosion effect of hydrophobic coatings, but less attention is paid to the influence of the shape of the particles contained in the filler on the anti-corrosion effect of the hydrophobic coating.

[0003] To further improve the corrosion resistance of heat exchangers, related technologies can also focus on particle shape to enhance their corrosion resistance. Summary of the Invention

[0004] The purpose of this application is to provide a heat exchanger with good corrosion resistance. Accordingly, this application also provides a composite material for the heat exchanger.

[0005] This application provides a heat exchanger having a channel for fluid flow. The heat exchanger includes a substrate and a hydrophobic coating covering at least a portion of the surface of the substrate. The hydrophobic coating includes a low surface energy silane material and a filler dispersed in the low surface energy silane material. The filler includes at least two types of particles, each of which has a different shape.

[0006] The hydrophobic coating of this application comprises a low surface energy silane material and a filler. The filler consists of particles that fill the network structure of the low surface energy silane material, and are firmly bonded to the heat exchanger substrate through the low surface energy silane material. The micropores or pores in the low surface energy silane material have a variety of shapes. The filler in the hydrophobic coating of this application comprises at least two types of particles, and the particle shapes of at least two types of particles are all different. The combination of particles with different shapes gives the particles a good filling effect in the hydrophobic coating, which helps to increase the density of the coating, increase the barrier effect of the hydrophobic coating against corrosive media, and improve the corrosion resistance of the heat exchanger.

[0007] This application also provides a composite material for a heat exchanger, the composite material comprising a solvent, a low surface energy silane material and a filler, the filler comprising at least two types of particles, the at least two types of particles having different shapes.

[0008] The composite material of this application forms an anti-corrosion coating containing particles of at least two shapes on the surface of the heat exchanger, thereby improving the corrosion resistance of the heat exchanger. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the microstructure of irregularly shaped particles in one embodiment of this application;

[0010] Figure 2 This is a schematic diagram of the microstructure of three-dimensional dendritic particles in one embodiment of this application;

[0011] Figure 3 This is a schematic diagram of the heat exchanger in one embodiment of this application;

[0012] Figure 4 for Figure 3 A magnified schematic diagram of the assembly structure of some components of the heat exchanger in the diagram;

[0013] Figure 5 This is a cross-sectional schematic diagram of the hydrophobic coating on the surface of the heat exchanger substrate in one embodiment of this application;

[0014] Figure 6 This is a cross-sectional schematic diagram of the hydrophobic coating and rare earth conversion film on the surface of the heat exchanger substrate in one embodiment of this application.

[0015] Figure 7 The surface morphology of the samples from Comparative Example 1 and Comparative Example 2 during the 48h salt spray test of this application is shown.

[0016] Figure 8 The surface morphology of the samples from Comparative Example 1 and Comparative Example 2 in the 96h salt spray test of this application is shown.

[0017] Figure 9 The surface morphology of the samples from Example 1 and Comparative Example 1 in the 96h salt spray test of this application is shown. Detailed Implementation

[0018] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0019] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0020] Currently, most anti-corrosion coatings on heat exchanger surfaces are chemical conversion films (TCPs). For example, the anti-corrosion coating on aluminum heat exchangers is often a TCP formed by chromium salt passivation. Due to the high toxicity and carcinogenicity of hexavalent chromium, its use in passivation coatings is strictly prohibited both domestically and internationally. Currently, trivalent chromium is used instead of hexavalent chromium for surface anti-corrosion treatment of aluminum products. However, the environmental and human health hazards of trivalent chromium cannot be ignored. Therefore, developing green and environmentally friendly coatings suitable for heat exchangers, forming an anti-corrosion coating on the heat exchanger surface through coating application, has become an important development direction for heat exchanger surface anti-corrosion technology.

[0021] Some related technologies involve coating heat exchanger surfaces with hydrophobic sols, which then cure to form a hydrophobic coating. During the curing process, the groups in the hydrophobic sol condense with the Me-OH groups on the metal substrate surface to form bonds, and these groups also cross-link to form a network structure. Therefore, the resulting hydrophobic coating can firmly bond to the heat exchanger substrate. The hydrophobic coating provides a larger contact angle for corrosive solutions on the heat exchanger surface, making them less prone to spreading and reducing the direct contact area between the corrosive solution and the heat exchanger surface. Furthermore, the hydrophobic coating itself provides a certain degree of physical barrier or shielding against corrosive media, reducing the contact between the metal substrate and external substances (e.g., oxygen, water, or other corrosive substances). Thus, on the one hand, it reduces or slows down the chemical corrosion of the metal substrate surface by acids and alkalis; on the other hand, due to the reduced contact with oxygen and water, the electrode polarization and depolarization processes are slowed down, thereby reducing or slowing down the electrochemical corrosion of the metal substrate surface to some extent. Therefore, the hydrophobic coating can improve the corrosion resistance of the heat exchanger.

[0022] The improvement in corrosion resistance of hydrophobic coatings mainly depends on their hydrophobic properties and internal microstructure. The hydrophobic properties of a hydrophobic coating originate from the hydrophobic groups within it, while its internal microstructure is largely influenced by the degree of cross-linking of the hydrophobic sol. Generally, coatings formed by sols with low cross-linking degrees have more pores; the more pores, the weaker the barrier effect of the coating itself. As the degree of cross-linking increases, the coating density, mechanical strength, and hardness increase, and the barrier effect of the coating itself also increases. However, excessive cross-linking increases the brittleness of the coating, leading to an increase in microcracks on the coating surface and even cracking. To ensure that the hydrophobic coating adheres firmly to the metal substrate and does not generate excessive microcracks or cracking within the coating, the hydrophobic sol needs to have an appropriate degree of cross-linking. Hydrophobic coatings formed by hydrophobic sols inevitably contain some micropores or defects, which can easily become pathways for corrosive media to diffuse into the metal substrate. Therefore, fillers can be added to the hydrophobic sol.

[0023] The filler consists of numerous particles that fill the micropores or voids in the hydrophobic coating. These particles block the transport paths of corrosive media, hindering their transport and diffusion within the hydrophobic coating. Furthermore, they increase the density and thickness of the hydrophobic coating, thereby enhancing its barrier effect against corrosive substances. Currently, most research focuses on the impact of filler content on the anti-corrosion effect of the hydrophobic coating, but less attention is paid to the influence of the shape of the particles within the filler on its anti-corrosion performance.

[0024] A first aspect of this application provides a heat exchanger having a channel for fluid flow. The heat exchanger includes a substrate and a hydrophobic coating covering at least a portion of the surface of the substrate. The hydrophobic coating includes a low surface energy silane material and a filler dispersed in the low surface energy silane material. The filler includes at least two types of particles, each of which has a different shape.

[0025] The hydrophobic coating of this application comprises a low surface energy silane material and a filler. The filler consists of particles that fill the network structure of the low surface energy silane material, which then firmly bonds to the heat exchanger substrate. The micropores or pores in the low surface energy silane material exhibit a variety of shapes. From a pore-filling perspective, the higher the shape matching between the particles and the pores, the better the filling effect. For example, irregularly shaped pores can be effectively filled by irregularly shaped particles, while regularly shaped pores require matching particles for optimal filling. The diversity of particle shapes is beneficial for pore filling. The filler in the hydrophobic coating of this application comprises at least two types of particles with different shapes. This combination of different shaped particles provides a good filling effect in the hydrophobic coating, increasing its density, enhancing its barrier effect against corrosive media, and improving the corrosion resistance of the heat exchanger.

[0026] Fillers are typically added in the form of one or more particles, rather than one or a few. The quantity of each type of particle in a coating can be in the tens, hundreds, thousands, tens of thousands, tens of millions, hundreds of millions, or even trillions. For example, a single particle could include 10, 10... 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10The filler is added in equal quantities. In other words, the focus is on the type of particles, not the quantity. Therefore, when discussing the effect of particle shape on hydrophobic coatings, the focus is not on the shape of one or a few particles, but on the commonalities in shape among particles within a given particle type, and the effects of differences in shape between two or more types of particles. In this application, the particles within a given particle type have approximately the same chemical composition and shape; each particle type corresponds to one chemical composition and one particle shape.

[0027] Particle shape is primarily related to the preparation process. Common preparation processes include ball milling, air jet milling, gas atomization, water atomization, and chemical methods. Different preparation processes result in different particle shapes. For example, powder particles obtained from strip air jet milling are flake-shaped, while those prepared by water atomization or gas atomization are spherical. Silica powder particles prepared by precipitation are roughly spherical, while silica powder particles prepared by vapor phase methods generally exhibit a three-dimensional dendritic structure. Due to the influence of preparation process conditions, the shapes of all particles within a given particle may not be identical. In such cases, the particle shape corresponding to a given particle refers to the shape of the majority (e.g., 50%, 60%, 70%, 80%, 90%, 99%) of the particles within that particle. For example, due to the influence of the preparation process, 99% of the particles in a compound A particle are spherical, while the remaining 1% are teardrop-shaped; we still describe the shape of this compound A particle as spherical. That is, we ignore the small number of particle shape deviations caused by the preparation process.

[0028] In some embodiments, at least one of the at least two types of particles has an irregular shape.

[0029] When particles are filled into the network structure of low surface energy silane materials, not all particles can perfectly match the pores they fill. Therefore, some unfilled gaps may remain on the outer surface of the particles. Furthermore, since the particles themselves have better strength, hardness, and wear resistance than the low surface energy silane materials, the gaps between the particles become the main pathway for corrosive media to penetrate the coating and reach the heat exchanger substrate. The tortuosity and length of the transport path of the corrosive media in the hydrophobic coating largely depend on the surface morphology, or shape, of the particles.

[0030] Particle shapes can be categorized into regular and irregular shapes. Regular shapes typically refer to shapes that exhibit certain mathematical regularities in the dimensions of points, lines, or planes, such as spheres, ellipsoids, rods, needles, plates, columns, hexahedrons, tetrahedrons, dendritic shapes, and three-dimensional dendritic shapes. Regularly shaped particles can usually be described by their regular shape characteristics. Irregular shapes, on the other hand, are those that lack obvious mathematical regularities in the dimensions of points, lines, and planes, such as... Figure 1 As shown.

[0031] Compared to regularly shaped particles, irregularly shaped particles are more effective at increasing the tortuousness of the transport path of corrosive media. This is because the gaps between irregularly shaped particles, and between irregularly shaped and regularly shaped particles, are irregular in shape. Therefore, the introduction of irregularly shaped particles helps to hinder the penetration and diffusion of corrosive media in the hydrophobic coating, prolonging the time it takes for the corrosive media to penetrate the hydrophobic coating and reach the heat exchanger substrate. This further enhances the barrier effect of the hydrophobic coating against corrosive media and improves the corrosion resistance of the heat exchanger. In addition, irregularly shaped particles also have good anti-slip properties, which helps maintain the consistency and stability of the hydrophobic coating.

[0032] In some embodiments, at least two types of particles have different chemical compositions. As mentioned earlier, the shape of the particles is mainly affected by the preparation process. In some cases, different types of particles can be prepared using the same material but different preparation processes. For example, flake-shaped particles can be prepared by air jet milling of alumina strips, and spherical particles can be prepared by atomization of alumina gas. Then, the flake-shaped and spherical alumina particles are added to the hydrophobic coating to achieve a composite of particles of different shapes in the coating. In other cases, different types of particles can also be prepared using different materials and different preparation processes. For example, irregular alumina particles can be composited with three-dimensional dendritic particles of fumed silica. Since particles prepared from different materials have different physicochemical properties, such as strength, hardness, and wear resistance, adding them to the coating can enhance the hydrophobic coating in different ways. To improve the overall performance of the hydrophobic coating, this application can also use particles with different chemical compositions.

[0033] In some embodiments, the irregularly shaped particles are selected from one of alumina, zinc oxide, zirconium oxide, titanium oxide, silicon oxide, lanthanum oxide, cerium oxide, praseodymium oxide, boron nitride, and barium sulfate. These compounds possess good strength, hardness, and abrasion resistance, and when added as fillers to hydrophobic coatings, they can persistently enhance the corrosion resistance of the hydrophobic coatings.

[0034] In some embodiments, at least one of the at least two types of particles has a regular shape, selected from spherical, ellipsoidal, rod-shaped, needle-shaped, plate-shaped, columnar, hexahedral, tetrahedral, dendritic, and three-dimensional dendritic shapes. This application also incorporates regularly shaped particles into the hydrophobic coating to increase the diversity of particle shapes. In some embodiments, the three-dimensional dendritic particles are fumed silica particles. Figure 2 The shape of the fumed silica particles is shown schematically.

[0035] In some embodiments, the regularly shaped particles are selected from one of aluminum oxide, zinc oxide, zirconium oxide, titanium oxide, silicon oxide, lanthanum oxide, cerium oxide, praseodymium oxide, boron nitride, graphene, graphene oxide, carbon nanotubes, and barium sulfate.

[0036] In some embodiments, the particle size range of the at least two types of particles is 10 to 100 nm.

[0037] In this application, particles are filled within a low surface energy silane-based material network structure. Particles that are too large or too small will weaken the coating's barrier effect against corrosive media: overly large particles increase internal defects in the coating; underly small particles tend to agglomerate and are difficult to disperse, resulting in uneven filling of the micropores or pores within the low surface energy silane-based material network structure. To avoid affecting the heat exchanger's performance, the hydrophobic coating on the heat exchanger surface is relatively thin. Accordingly, this application selects a particle size range of 10–100 nm, ensuring uniform filling of the particles within the low surface energy silane-based material network structure without significantly increasing internal defects in the coating.

[0038] Due to the manufacturing process, the particle size of a particle is typically within a fixed range. For example, if the filler is alumina particles, describing the particle size range as 20–40 nm means that the alumina particles added to the hydrophobic coating all have a particle size within the range of 20–40 nm. Correspondingly, a particle also has an average particle size. In this application, the average particle size theoretically refers to the average particle size of the particles added to the hydrophobic coating.

[0039] In some embodiments, the at least two types of particles include a first type of particle and a second type of particle, wherein the average particle size of the first type of particle is 2 to 10 times that of the second type of particle. The pore sizes in low surface energy silane materials are also diverse. This application uses particles with different average particle sizes, which on the one hand improves the filling effect of the particles on the pores, and on the other hand, the combination of particles with different sizes also helps to increase the density of the coating. In some embodiments, the first type of particle is a regularly shaped particle, and the second type of particle is an irregularly shaped particle; or, the first type of particle is an irregularly shaped particle, and the second type of particle is a regularly shaped particle. In some embodiments, the ratio of the first type of particle to the second type of particle in the hydrophobic coating is 1:1 to 1:5.

[0040] In some embodiments, the at least two types of particles are compounds that are sparingly or slightly soluble in water. Generally, in water at 20°C, a solubility of less than 0.01 g is considered sparingly soluble, a solubility of greater than 0.01 g and less than 1 g is considered slightly soluble, a solubility of greater than 1 g and less than 10 g is considered soluble, and a solubility of greater than 10 g is considered readily soluble. Sparingly or slightly soluble particles can exist stably in the hydrophobic coating for a long period, thereby achieving a sustained improvement in the anti-corrosion performance of the hydrophobic coating.

[0041] In some embodiments, the resistivity of the at least two types of particles is 10. 9 ~10 22 Ω·cm. In other words, the particles are made of insulating materials. Thus, the particles can also utilize their insulating properties to slow down the transfer of ions between the cathode and anode in the electrochemical corrosion galvanic cell, and have a certain inhibitory effect on the overflow of metal cations in the anode and the discharge effect generated by the cathode, that is, they have a resistive effect, reducing or slowing down the electrochemical corrosion of the metal substrate surface.

[0042] In some embodiments, at least a portion of the surface of at least one of the at least two types of particles is grafted with a hydrophobic group selected from at least one of a hydrocarbon group, a halogen atom, and a nitro group. In some embodiments, the hydrocarbon group may be -C. n H 2n+1 (n≥1), -CH=CH2, -C6H5; halogen atoms can be -F, -Cl, -Br, -I, -At; the nitro chemical formula is -NO2. The particles can be hydrophobically treated to give them certain hydrophobic properties due to the grafting of hydrophobic groups onto their surface. Filling the hydrophobic coating with particles possessing certain hydrophobic properties can increase the hydrophobicity of the coating.

[0043] In some embodiments, the low surface energy silane material includes a silane with a hydrophobic group grafted onto its surface, wherein the hydrophobic group is selected from at least one of a hydrocarbon group, a halogen atom, and a nitro group. In some embodiments, the hydrocarbon group may be -C. n H 2n+1(n≥1), -CH=CH2, -C6H5; halogen atoms can be -F, -Cl, -Br, -I, -At; the nitro chemical formula is -NO2. In some embodiments, the low surface energy silane material can be selected from one or more of heptadecafluorodecyltriethoxysilane, heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltriethoxysilane, octadecyltrimethoxysilane, and hexadecyltrimethoxysilane.

[0044] In some embodiments, the hydrophobic coating comprises, by weight, 0.5 to 1.5 parts of low surface energy silane material and 0.1 to 5 parts of filler.

[0045] Unless otherwise stated, percentages, proportions, or parts in this document are expressed by mass. A "part by mass" refers to the basic unit of measurement for the mass ratio of multiple components. One part can represent any unit mass, such as 1g, 1.68g, or 5g, etc.

[0046] In hydrophobic coatings containing fillers, the filler content or the ratio of filler to low surface energy silane materials is a key factor affecting corrosion resistance. Too little filler content fails to achieve optimal corrosion protection, while too much filler content leads to decreased compatibility between the filler and the low surface energy silane materials, uneven dispersion of the filler in the hydrophobic coating, poor uniformity of the coating's performance, increased internal defects and cracks, and even coating rupture, while also reducing the coating's hydrophobic properties. The ratio used in this application effectively maintains the good hydrophobic properties of the coating while significantly improving its barrier effect, thereby achieving an optimal level of improvement in the surface corrosion resistance of the heat exchanger.

[0047] In some embodiments, the static contact angle between the hydrophobic coating and water is greater than 150°, and the droplet roll-off angle of the hydrophobic coating is less than 5°. Under the specified ratio of low surface energy silane materials and fillers in this application, the hydrophobic coating exhibits good hydrophobic properties.

[0048] In some embodiments, at least a portion of the substrate surface is coated with a rare earth conversion film, the rare earth conversion film comprising rare earth compounds, and at least a portion of the rare earth conversion film is located between the substrate and the hydrophobic coating. "The rare earth conversion film is located between the substrate and the hydrophobic coating" means that one side of the rare earth conversion film is in direct contact with the substrate, and the other side is in direct contact with the hydrophobic coating. The hydrophobic coating is located away from the substrate relative to the rare earth conversion film, and the rare earth conversion film is sandwiched between the heat exchanger substrate and the hydrophobic coating. The hydrophobic coating adheres to the surface of the heat exchanger substrate through the rare earth conversion film. In some cases, the hydrophobic coating coating on the surface of the heat exchanger substrate may be in direct contact with the heat exchanger substrate; or, there may be a rare earth conversion film between the hydrophobic coating and the heat exchanger substrate; or, a portion of the hydrophobic coating is in direct contact with the heat exchanger substrate, and another portion of the hydrophobic coating is further separated from the heat exchanger substrate by the rare earth conversion film. In some cases, the rare earth conversion film can be entirely located between the heat exchanger substrate and the hydrophobic coating; alternatively, a portion of the rare earth conversion film may be located between the heat exchanger substrate and the hydrophobic coating, while another portion of the rare earth conversion film has one side in direct contact with the heat exchanger substrate and the other side exposed to the external environment. In other words, the hydrophobic coating is not applied over this other portion of the rare earth conversion film, and a portion of the heat exchanger surface is covered only with the rare earth conversion film. The rare earth compounds in the rare earth conversion film can further improve the corrosion resistance of the heat exchanger.

[0049] In some embodiments, the rare earth compound includes rare earth oxides and / or rare earth hydroxides. For example, the rare earth compound may be cerium oxide (CeO2), cerium trioxide (Ce2O3), cerium hydroxide (Ce(OH)4), etc. Similarly, the rare earth compound may also be a compound of other rare earth elements, such as La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, and Y.

[0050] In some embodiments, the heat exchanger includes a manifold, fins, and multiple heat exchange tubes, the heat exchange tubes being fixed to the manifold and having their inner cavities communicating with those of the manifold. At least a portion of the fins is fixed between two adjacent heat exchange tubes, and the substrate includes the substrate of at least one of the manifold, heat exchange tubes, and fins. That is, the heat exchanger is a microchannel heat exchanger. A hydrophobic coating, or a combination of a hydrophobic coating and a rare-earth conversion film, is coated on at least a portion of the surface of at least one of the manifold, heat exchange tubes, and fins.

[0051] The following description uses a microchannel heat exchanger as an example to illustrate the heat exchanger of this application.

[0052] like Figure 3 and Figure 4As shown, this application provides a heat exchanger 100, which includes a manifold 11, a plurality of heat exchange tubes 12, and a plurality of fins 13. In the heat exchanger 100, the plurality of heat exchange tubes 12 are all fixed to the manifold 11, and the heat exchange tubes 12 are provided with a plurality of channels 122 for refrigerant flow, and the plurality of channels 122 of the heat exchange tubes 12 are all in communication with the inner cavity of the manifold 11. At least a portion of the fins 13 are fixed between two adjacent heat exchange tubes 12. The manifold 11 is provided with a fluid inlet 101 and a fluid outlet 102 communicating with its inner cavity, thereby facilitating fluid entry into the heat exchanger.

[0053] Multiple heat exchange tubes 12 are arranged along the length of the manifold 11, the length of which can be referenced. Figure 3 or Figure 4 The X direction in the diagram. The heat exchange tube 12 is a longitudinally extending tubular structure; the length direction of the heat exchange tube 12 can be referenced. Figure 3 or Figure 4 The Y-direction and the width direction of heat exchange tube 12 can be referenced. Figure 4 The dimension in the D direction of the heat exchange tube 12 is larger than its dimension in the thickness direction, and the thickness direction of the heat exchange tube 12 approximately coincides with the length direction of the manifold 11. Furthermore, the width direction of the heat exchange tube 12 and the length direction of the manifold 11 are not co-directional. Figure 4 In the heat exchange tube 12, the width direction (D direction) is approximately perpendicular to the length direction (X direction) of the manifold 11.

[0054] exist Figure 3 In this heat exchanger, there are two manifolds 11, and the two ends of the heat exchange tube 12 along its length are respectively inserted into the inner cavities of the two manifolds 11. This type of heat exchanger is also commonly referred to in the industry as a single-row heat exchanger. In some other embodiments, the number of manifolds 11 can be one or more than two. Correspondingly, the number of heat exchange tubes and fins is also set according to the actual product requirements.

[0055] In some implementations, such as Figure 4 As shown, the fins 13 are wavy along the length (Y direction) of the heat exchange tube 12. The fins 13 include multiple fin units 131 arranged along the length of the heat exchange tube 12. These multiple fin units 131 are sequentially connected along the length of the heat exchange tube 12, and the connection points of adjacent fin units 131 form peaks or troughs in the corresponding wave structure of the fins 13. The fins 13 are fixed to the heat exchange tube 12 at the connection points of adjacent fin units 131. During assembly, components such as the manifold 11, fins 13, and heat exchange tube 12 can be pre-assembled together. A brazing process is then used to fix the manifold 11 to the heat exchange tube 12, and the fins 13 are fixed between adjacent heat exchange tubes.

[0056] The heat exchanger 100 includes a substrate 100-1 and a hydrophobic coating 14 covering at least a portion of the surface of the substrate 100-1. The substrate 100-1 is the substrate of at least one of the manifold 11, the heat exchange tube 12, and the fins 13.

[0057] Figure 5 This is a cross-sectional schematic diagram of the surface of the heat exchanger substrate in one embodiment of this application. Figure 5 As shown, the surface of the heat exchanger substrate 100-1 is covered with a hydrophobic coating 14. The hydrophobic coating includes a low surface energy silane material 141 and two types of particles dispersed in the low surface energy silane material. One type of particle has an irregular shape, and the other type of particle has a three-dimensional dendritic shape. The irregularly shaped particles 142 and the three-dimensional dendritic particles 143 are mixed and filled in the low surface energy silane material 141. Figure 5 R1 and R2 are used to show the transport path of the corrosive medium in the hydrophobic coating. As can be seen from the figure, the combination of irregularly shaped particles and three-dimensional dendritic particles makes the path of the corrosive medium through the hydrophobic coating more tortuous, thereby enhancing the barrier effect of the hydrophobic coating on the corrosive medium.

[0058] Figure 6 This is a cross-sectional schematic diagram of the surface of a heat exchanger substrate according to another embodiment of this application. Figure 6 As shown, a rare earth conversion film 15 is coated on the surface of the heat exchanger substrate 100-1. The rare earth conversion film 15 includes a rare earth compound 151 (shown as a triangle). The rare earth conversion film 15 is located between the heat exchanger substrate 100-1 and the hydrophobic coating 14.

[0059] In other embodiments, the heat exchanger of this application can also be a plate heat exchanger, a tube-and-fin heat exchanger, a shell-and-tube heat exchanger, a finned tube heat exchanger, a water-cooled plate, a direct-cooling plate, or other heat exchangers used for the flow of refrigerant or coolant. That is to say, the hydrophobic coating of this application, or the combination of a hydrophobic coating and a rare-earth conversion film, can be used not only for channel heat exchangers, but also for surface anti-corrosion treatment of other heat exchangers such as plate heat exchangers, tube-and-fin heat exchangers, shell-and-tube heat exchangers, finned tube heat exchangers, water-cooled plates, and direct-cooling plates.

[0060] A second aspect of this application provides a surface treatment method for a heat exchanger, comprising:

[0061] Step S11: Provide a heat exchanger, which includes a substrate;

[0062] Step S21: Provide a composite material, which includes a solvent, a low surface energy silane material, and a filler, wherein the filler includes at least two types of particles, and the shapes of the at least two types of particles are different.

[0063] Step S31: Apply the composite material to at least a portion of the surface of the heat exchanger substrate provided in S11, and cure it to form a hydrophobic coating applied to at least a portion of the surface of the substrate.

[0064] The characteristics and types of low surface energy silane materials, as well as the shape, particle size range, chemical composition, and types of filler particles, are described in the previous text and will not be repeated here.

[0065] In some embodiments, the heat exchanger substrate provided in step S11 undergoes surface sandblasting. Specifically, in some embodiments, the surface sandblasting treatment includes: sandblasting the surface of the heat exchanger substrate with 100-200 mesh white corundum at a sandblasting angle of 30°-60°, maintaining a distance of 30-60 mm between the spray gun and the workpiece, and performing sandblasting more than or equal to 1 time; then ultrasonically cleaning or rinsing the heat exchanger surface with alcohol or water, followed by air drying or baking at 35°C-50°C. Sandblasting can increase the surface roughness of the heat exchanger, thereby making the hydrophobic coating adhere more firmly to the surface of the heat exchanger substrate. In some embodiments, the surface roughness Ra of the heat exchanger substrate is 0.5 μm-10 μm, and in some embodiments, the surface roughness Ra of the heat exchanger substrate is 1 μm-3 μm. For example, the micrometers can be 1μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2.0μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm, 3μm, etc.

[0066] In some embodiments, in step S31, the method of applying the composite material to at least a portion of the surface of the heat exchanger includes, but is not limited to, at least one of dip coating, spraying, brushing, curtain coating, or roller coating.

[0067] In some embodiments, the curing process in step S31 may include, for example, drying in an oven. In some embodiments, the curing temperature is 60–180°C. In some embodiments, the curing time is 5–35 minutes.

[0068] In some embodiments, before step S31 and after step S11, the method further includes step S41: forming a rare earth conversion film on the surface of the heat exchanger. The order of steps S41 and S21 is not limited; step S41 can be performed before or after step S21.

[0069] In some embodiments, step S41 includes: preparing a rare earth conversion solution, immersing the heat exchanger in the rare earth conversion solution, removing the heat exchanger, and then drying the surface of the heat exchanger. In other embodiments, the rare earth conversion solution can also be dip-coated, sprayed, brushed, dip-coated, or roller-coated onto the surface of the heat exchanger.

[0070] In some embodiments, the rare earth conversion solution includes rare earth raw materials, an oxidant, and water.

[0071] In some embodiments, the rare earth conversion solution comprises 1 to 3 parts of rare earth raw material, 92.5 to 97.5 parts of water, and 1.5 to 4.5 parts of oxidant.

[0072] In some embodiments, the method for preparing rare earth conversion solution includes: dissolving rare earth raw materials in water, and then adding an oxidant to obtain rare earth conversion solution.

[0073] In some embodiments, the preparation method of rare earth conversion solution may include: dissolving 1 to 3 parts by mass of rare earth raw material in 92.5 to 97.5 parts by mass of deionized water, mixing and treating to obtain an intermediate solution; heating the intermediate solution to 45°C to 55°C, then adding 1.5 to 4.5 parts by mass of oxidant to the system, and continuing to mix to obtain rare earth conversion solution.

[0074] The aforementioned rare earth raw materials are those that can provide rare earth elements, such as raw materials that can provide cerium (Ce). In some embodiments, the rare earth raw materials include, but are not limited to, one or a combination of at least two of cerium nitrate hexahydrate, anhydrous cerium nitrate, cerium chloride and its polyhydrates, cerium sulfate and its polyhydrates, and cerium acetate and its polyhydrates. The aforementioned cerium chloride and its polyhydrates are anhydrous cerium chloride, polyhydrates of cerium chloride such as cerium chloride heptahydrate or cerium chloride octahydrate, etc. Similarly, the aforementioned cerium sulfate and its polyhydrates are anhydrous cerium sulfate, polyhydrates of cerium sulfate such as cerium sulfate tetrahydrate; cerium acetate and its polyhydrates are anhydrous cerium acetate, polyhydrates of cerium acetate such as cerium acetate trihydrate or cerium acetate tetrahydrate, etc.

[0075] In some embodiments, the oxidant includes, but is not limited to, at least one of hydrogen peroxide, sodium perchlorate, and tert-butyl hydrogen peroxide. For example, the oxidant may be an aqueous solution of hydrogen peroxide (with a mass concentration of about 27.5 wt.% to 30 wt.%), or sodium perchlorate, or an aqueous solution of tert-butyl hydrogen peroxide or a n-butanol solution of tert-butyl hydrogen peroxide (with a mass concentration of not less than 60 wt.%).

[0076] A third aspect of this application also provides a composite material for a heat exchanger, the composite material comprising a solvent, a low surface energy silane material, and a filler, the filler comprising at least two types of particles, each of which has a different shape. This composite material can form an anti-corrosion coating containing particles of at least two different shapes on the surface of the heat exchanger, thereby improving the corrosion resistance of the heat exchanger.

[0077] In some embodiments, the solvent is selected from at least one of ethanol, methanol, and isopropanol.

[0078] The characteristics and types of low surface energy silane materials, as well as the shape, particle size range, chemical composition, and types of filler particles, are described in the previous text and will not be repeated here.

[0079] In some embodiments, the composite material comprises, by weight, 93.5 to 99.4 parts solvent, 0.5 to 1.5 parts low surface energy silane material, and 0.1 to 5 parts filler, wherein the filler comprises at least two types of particles, and the at least two types of particles have different shapes.

[0080] In some embodiments, the composite material provided in step S21 is obtained by manufacturing.

[0081] The fourth aspect of this application provides a method for preparing a composite material, the method comprising: mixing a solvent, a low surface energy silane material and a filler to obtain a composite material, wherein the filler comprises at least two types of particles, and the at least two types of particles have different shapes.

[0082] In this application, mixing can be achieved through mechanical stirring, ultrasonic dispersion, or other methods. The raw materials can be added to the solvent all at once, or in two or more additions. This application does not limit the mixing method, order of addition, method of addition, or number of additions. In some embodiments, at least one of at least two types of particles is added to the solvent in two or more additions. This facilitates the dispersion of the filler in the composite material, thereby ensuring that the filler is uniformly dispersed in the network structure formed by the low surface energy silane material.

[0083] To facilitate understanding of the present invention, multiple sets of experiments were conducted. The present invention will be further described below with reference to specific embodiments and comparative examples. For ease of performance testing, plates were used instead of heat exchangers for sample preparation. That is, plates of the same material as the heat exchanger were used, and a relevant coating was applied to the plates to form a coating for testing. In actual preparation, the surface treatment of the heat exchanger can adopt the same steps as the surface treatment of the plates in this embodiment.

[0084] Example 1

[0085] Step 1: Surface Pretreatment

[0086] The plate was sandblasted with 120-mesh white corundum. The angle between the spray gun and the area to be coated was about 45° and the distance between the spray gun and the area to be coated was 50mm. One sandblasting was performed. Then the plate was cleaned with anhydrous ethanol and dried at 40°C for later use.

[0087] Step 2: Forming a rare earth conversion membrane

[0088] Step 2.1: Weigh 1 part of cerium nitrate hexahydrate into a beaker, add 95.1 parts of deionized water, and mechanically stir until the solid is completely dissolved and the solution is colorless and transparent. Heat the solution in a water bath to 50°C, add 2.4 parts of a tert-butyl hydroperoxide n-butanol solution (wherein the mass fraction of tert-butyl hydroperoxide is greater than 70%), and continue stirring and heating to 50°C to prepare a rare earth conversion solution.

[0089] Step 2.2: Immerse the plate that has undergone surface pretreatment in Step 1 in the rare earth conversion solution prepared in Step 2.1, keep it at 50°C for 40 minutes, take it out and dry it with cold air or let it air dry naturally, thus forming a rare earth conversion film on the surface of the plate.

[0090] The main equations for the formation of rare earth conversion films are as follows:

[0091] Al→Al 3+ +3e - ;

[0092] O2 + 2H2O + 4e - →4OH - ;

[0093] Ce 3+ +3OH - →Ce(OH)3;

[0094] 2Ce(OH)3→Ce2O3+3H2O.

[0095] Step 3: Preparation of composite materials

[0096] Step 3.1: Weigh 98 parts of ethanol, 1 part of heptadecafluorodecyltrimethoxysilane, and 1 part of hydrophobic nano-silica (SiO2) powder, ultrasonically disperse for 15 min, and mechanically stir for 2 h to obtain sol A.

[0097] Step 3.2: Take 98 parts of the sol A prepared in step 3.1 above, add 1.5 parts of hydrophobic nano silica powder and 0.5 parts of nano alumina (Al2O3) powder, ultrasonically disperse for 15 min, and mechanically stir for 30 min to obtain the composite material.

[0098] The hydrophobic nano silica powder is obtained by treating fumed silica with dimethyl dichlorosilane (CAS: 75-78-5). The fumed silica particles are three-dimensional dendritic in shape and have a particle size of 5-50 nm. The nano alumina powder consists of irregularly shaped particles with a particle size of 20-40 nm.

[0099] Step 4: Coating the plate

[0100] The plate with the rare earth conversion film on its surface, which has been processed in step 2, is immersed in the composite material prepared in step 3 for 2 minutes. After immersion, the plate is placed in an oven and cured at 120°C for 20 minutes to obtain a plate with a rare earth conversion film and a hydrophobic coating.

[0101] Examples 2-3

[0102] The main difference between Examples 2 and 3 and Example 1 lies in step 3, which involves preparing the composite material. All other steps are the same as in Example 1.

[0103] In Example 2, step 3, preparing the composite material, includes:

[0104] Step 3.1: Weigh 99 parts of ethanol, 0.5 parts of heptadecafluorodecyltrimethoxysilane, and 0.5 parts of hydrophobic nano silica powder, ultrasonically disperse for 15 min, and mechanically stir for 2 h to obtain sol A.

[0105] Step 3.2: Take 99.4 parts of the sol A prepared in step 3.1 above, add 0.5 parts of hydrophobic nano silica powder and 0.1 parts of nano alumina powder, ultrasonically disperse for 15 min, and mechanically stir for 30 min to obtain the composite material.

[0106] In Example 3, step 3, preparing the composite material, includes:

[0107] Step 3.1: Weigh 96.5 parts of ethanol, 1.5 parts of heptadecafluorodecyltrimethoxysilane, and 2 parts of hydrophobic nano silica powder, disperse them by ultrasonication for 15 min, and then stir them by mechanical stirring for 2 h to obtain sol A.

[0108] Step 3.2: Take 97 parts of the sol A prepared in step 3.1 above, add 2 parts of hydrophobic nano silica powder and 1 part of nano alumina powder, ultrasonically disperse for 15 min, and mechanically stir for 30 min to obtain the composite material.

[0109] Comparative Example 1

[0110] The difference between Comparative Example 1 and Example 1 lies in step 3. Step 3 of Comparative Example 1 involves preparing the composite material, which includes:

[0111] Step 3.1: Weigh 98 parts of ethanol, 1 part of heptadecafluorodecyltrimethoxysilane, and 1 part of hydrophobic nano silica powder, disperse them by ultrasonication for 15 min, and then stir them by mechanical stirring for 2 h to obtain sol A.

[0112] Step 3.2: Take 98 parts of sol A prepared in step 3.1 above, add 2 parts of hydrophobic nano silica powder, ultrasonically disperse for 15 min, and mechanically stir for 30 min to obtain the composite material.

[0113] Everything else is the same as in Example 1.

[0114] Comparative Example 2

[0115] The difference between Comparative Example 2 and Example 1 lies in step 3. Step 3 of Comparative Example 2 involves preparing the composite material, which includes:

[0116] Step 3.1: Weigh 98 parts of ethanol, 1 part of heptadecafluorodecyltrimethoxysilane, and 1 part of hydrophobic nano silica powder, disperse them by ultrasonication for 15 min, and then stir them by mechanical stirring for 2 h to obtain sol A.

[0117] Step 3.2: Take 98 parts of the sol A prepared in step 3.1 above, add 2 parts of nano alumina powder, ultrasonically disperse for 15 min, and mechanically stir for 30 min to obtain the composite material.

[0118] Everything else is the same as in Example 1.

[0119] Performance testing

[0120] 1. Hydrophobicity test (contact angle test)

[0121] The testing instrument used is a contact angle measuring instrument, which adopts the optical imaging principle and uses image contour analysis to measure the contact angle of the sample. The contact angle refers to the angle formed at the solid-liquid-gas three-phase interface point on the solid surface when a drop of liquid is placed on a solid horizontal plane, with the liquid phase sandwiched between the two tangents of the gas-liquid interface and the solid-liquid interface.

[0122] During testing, turn on the contact angle measuring instrument and the connected computer, and open the testing software.

[0123] Place the sample on a horizontal worktable and use a microsyringe to adjust the amount of droplet, which is generally about 1 μL. The droplet forms on the needle tip. Rotate the knob to raise the worktable so that the sample surface comes into contact with the droplet. Then lower the worktable so that the droplet is left on the sample.

[0124] The contact angle of this region was obtained through testing and data analysis using testing software. Five different points were tested on each embodiment and comparative example sample, and the average value was recorded as the contact angle of that embodiment and comparative example sample.

[0125] The test results of the contact angle above show that the initial contact angle of the sample surface of Examples 1-3 and Comparative Examples 1-2 is greater than 150°, exhibiting a superhydrophobic state, indicating that the hydrophobic coating formed on the sample surface in each embodiment and comparative example of this application has excellent hydrophobic properties.

[0126] 2. Corrosion resistance test (salt spray test)

[0127] The plate samples prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to salt spray tests. The salt spray test was conducted according to the ASTM G85 standard, using acidic salt spray. Each sample was placed in a salt spray chamber, and the surface corrosion was observed at regular intervals. After the acidic salt spray test, each sample was removed, and the surface corrosion was observed and the time when corrosion spots appeared was recorded.

[0128] Due to the influence of salt spray chamber conditions and sample placement, even samples with the same formulation can show significant differences in salt spray test results across different batches. Therefore, to better compare the corrosion resistance of plates prepared with different formulations, this application compares samples from salt spray tests conducted concurrently.

[0129] This application compares the samples of Comparative Example 1 and Comparative Example 2. After a 48-hour salt spray test, the surface morphology of the samples of Comparative Example 1 and Comparative Example 2 is as follows: Figure 7 As shown, where Figure 7 (a) is a surface morphology diagram of the sample in Comparative Example 1. Figure 7 (b) shows the surface morphology of the sample in Comparative Example 2. After 96 hours of salt spray testing, the surface morphologies of the samples in Comparative Example 1 and Comparative Example 2 are as follows. Figure 8 As shown, where Figure 8 (a) is a surface morphology diagram of the sample in Comparative Example 1. Figure 8 (b) shows the surface morphology of the sample in Comparative Example 2. Figure 7 and Figure 8 It can be seen that the salt spray resistance of Comparative Example 1 and Comparative Example 2 samples is comparable.

[0130] This application also compares the samples of Example 1 and Comparative Example 1. The surface morphology of the samples of Example 1 and Comparative Example 1 underwent a 96% salt spray test, as shown below. Figure 9 As shown, where Figure 9 (a) is a surface morphology diagram of the sample from Example 1. Figure 9 (b) shows the surface morphology of the sample in Comparative Example 1. From... Figure 9 As observed, in the 96-hour salt spray test, the rust spots on the surface of the sample from Example 1 were significantly fewer than those in Comparative Example 1. This demonstrates that the corrosion resistance of the sample from Example 1 is superior to that of the sample from Comparative Example 1, indicating that the combination of nano-alumina particles with different chemical compositions and particle shapes and hydrophobic fumed silica particles can significantly improve the corrosion resistance of the samples.

[0131] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A heat exchanger having channels for fluid flow, the heat exchanger comprising a substrate and a hydrophobic coating covering at least a portion of the surface of the substrate, characterized in that: The hydrophobic coating comprises a low surface energy silane material and a filler dispersed in the low surface energy silane material. The filler comprises at least two types of particles, each of which has a different shape. At least one of the at least two types of particles has an irregular shape. The at least two types of particles include a first type of particle and a second type of particle, wherein the first type of particle is a regularly shaped particle and the second type of particle is an irregularly shaped particle. The method for preparing the heat exchanger includes preparing a composite material that can be used to form the hydrophobic coating. The preparation of the composite material includes the following steps: Weigh 96.5-99 parts of solvent, 0.5-1.5 parts of the low surface energy silane material, and 0.5-2 parts of the first type of particulate powder, and stir to obtain sol A; Take 97-99.4 parts of sol A, add 0.5-2 parts of the first type of granular powder and 0.1-1 parts of the second type of granular powder, and stir to obtain the composite material.

2. The heat exchanger according to claim 1, characterized in that: The at least two particles are compounds that are poorly or slightly soluble in water.

3. The heat exchanger according to claim 2, characterized in that: At least one of the at least two types of particles has a regular shape, which is selected from one of the following: spherical, ellipsoidal, rod-shaped, needle-shaped, plate-shaped, columnar, hexahedral, tetrahedral, dendritic, and three-dimensional dendritic.

4. The heat exchanger according to claim 3, characterized in that: The chemical compositions of the at least two types of particles are different, and the irregularly shaped particles are selected from one of aluminum oxide, zinc oxide, zirconium oxide, titanium oxide, silicon oxide, lanthanum oxide, cerium oxide, praseodymium oxide, boron nitride, and barium sulfate. The regularly shaped particles are selected from one of the following: aluminum oxide, zinc oxide, zirconium oxide, titanium oxide, silicon oxide, lanthanum oxide, cerium oxide, praseodymium oxide, boron nitride, graphene, graphene oxide, carbon nanotubes, and barium sulfate.

5. The heat exchanger according to claim 1, characterized in that: The particle size range of the at least two types of particles is 10~100 nm.

6. The heat exchanger according to claim 1, characterized in that: At least a portion of the surface of at least one of the at least two types of particles is grafted with a hydrophobic group selected from at least one of hydrocarbon groups, halogen atoms, and nitro groups.

7. The heat exchanger according to claim 1, characterized in that: The low surface energy silane material includes silanes with hydrophobic groups grafted onto their surface, wherein the hydrophobic groups are selected from at least one of hydrocarbon groups, halogen atoms, and nitro groups.

8. The heat exchanger according to claim 1, characterized in that: At least a portion of the surface of the substrate is coated with a rare earth conversion film, the rare earth conversion film comprising rare earth compounds, and at least a portion of the rare earth conversion film is located between the substrate and the hydrophobic coating.

9. The heat exchanger according to any one of claims 1 to 8, characterized in that: The heat exchanger includes a manifold, fins, and multiple heat exchange tubes. The heat exchange tubes are fixed to the manifold, and the inner cavity of the heat exchange tubes is connected to the inner cavity of the manifold. At least a portion of the fins is fixed between two adjacent heat exchange tubes. The substrate includes the substrate of at least one of the manifold, the heat exchange tubes, and the fins.

10. A composite material for heat exchangers, characterized in that: The composite material includes a solvent, a low surface energy silane material, and a filler. The filler includes at least two types of particles, each of which has a different shape. At least one of the at least two types of particles has an irregular shape. The at least two types of particles include a first type of particle and a second type of particle, wherein the first type of particle is a regularly shaped particle and the second type of particle is an irregularly shaped particle. The preparation of the composite material includes the following steps: Weigh 96.5-99 parts of the solvent, 0.5-1.5 parts of the low surface energy silane material, and 0.5-2 parts of the first type of particulate powder, and stir to obtain sol A; Take 97-99.4 parts of sol A, add 0.5-2 parts of the first type of granular powder and 0.1-1 parts of the second type of granular powder, and stir to obtain the composite material; The composite material also has at least one of the following technical features a to f: a. The solvent is selected from at least one of ethanol, methanol, and isopropanol; b. The low surface energy silane material includes silanes with hydrophobic groups grafted onto their surface, wherein the hydrophobic groups are selected from at least one of hydrocarbon groups, halogen atoms, and nitro groups; c. The at least two particles are compounds that are sparingly or slightly soluble in water; d. The shape of at least one of the at least two types of particles is a regular shape, and the regular shape is selected from one of the following: spherical, ellipsoidal, rod-shaped, needle-shaped, plate-shaped, columnar, hexahedral, tetrahedral, dendritic, and three-dimensional dendritic. e. The particle size range of the at least two types of particles is 10~100 nm; f. At least a portion of the surface of at least one of the at least two types of particles is grafted with a hydrophobic group selected from at least one of hydrocarbon groups, halogen atoms, and nitro groups.

Images