Heat exchanger and thermal management system

Abstract

This application provides a heat exchanger having channels for fluid flow. At least a portion of the surface of the heat exchanger is covered with a colored coating, which includes a color additive selected from at least one of organic pigments, inorganic pigments, and dyes. The colored coating on at least a portion of the surface of the heat exchanger facilitates its identification, installation, inspection, and maintenance. This application also provides a thermal management system including a compressor, a first heat exchanger, a throttling device, and a second heat exchanger. The surface color of the first heat exchanger differs from the surface color of the second heat exchanger. When refrigerant flows through the thermal management system, the refrigerant flows through the compressor into the first heat exchanger, then into the throttling device, and then into the second heat exchanger, where it undergoes heat exchange before flowing back into the compressor. This thermal management system allows for the differentiation of different heat exchangers by their external color, facilitating the installation, inspection, and maintenance of the heat exchangers within the thermal management system.

Description

Technical Field

[0001] This application relates to the field of heat exchange technology, and more particularly to a heat exchanger and a thermal management system. Background Technology

[0002] During the use of heat exchangers, it may be necessary to distinguish between different heat exchangers or different components of heat exchangers. For example, when there are more than two heat exchangers in the same module of a thermal management system, and different heat exchangers are used to perform different functions. Most existing heat exchangers are based on the color of the base material, and at most there are slight differences in size or shape, making it difficult to distinguish them by appearance, which causes inconvenience in installation, inspection or maintenance. Summary of the Invention

[0003] The present invention aims to solve the above-mentioned technical problems. To this end, the present invention proposes a heat exchanger and its manufacturing method, as well as a thermal management system.

[0004] This application provides a heat exchanger having a channel for fluid flow, and at least a portion of the surface of the heat exchanger is covered with a colored coating, the colored coating comprising a color additive selected from at least one of organic pigments, inorganic pigments and dyes.

[0005] The heat exchanger of this application has at least a portion of its surface covered with a colored coating to facilitate identification, installation, inspection, or maintenance. In practical applications, different colored coatings can be applied to different heat exchangers or different areas of the heat exchanger surface according to usage requirements, making them easy to distinguish visually.

[0006] This application also provides a thermal management system, which includes a compressor, a first heat exchanger, a throttling device, and a second heat exchanger. The surface color of the first heat exchanger is different from the surface color of the second heat exchanger. When refrigerant flows through the thermal management system, the refrigerant flows into the first heat exchanger via the compressor, and after heat exchange occurs in the first heat exchanger, it flows into the throttling device. Then, the refrigerant flows into the second heat exchanger, and after heat exchange occurs in the second heat exchanger, it flows back into the compressor.

[0007] The thermal management system of this application can distinguish different heat exchangers by their appearance color, which facilitates the installation, inspection or maintenance of heat exchangers in the thermal management system.

[0008] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the structure of a heat exchanger in one embodiment of this application;

[0010] Figure 2 This is a partial cross-sectional schematic diagram of the heat exchanger manifold in one embodiment of this application;

[0011] Figure 3 for Figure 1 A magnified view of region A in the middle;

[0012] Figure 4 This is a schematic diagram of the fins and heat exchange tubes of a heat exchanger in one embodiment of this application;

[0013] Figure 5 This is a schematic diagram of the edge region and the middle region of the inner side of the heat exchange tube of a heat exchanger in one embodiment of this application;

[0014] Figure 6 This is a schematic diagram of the outer edge region and the central region of the inner surface of the heat exchanger fins in one embodiment of this application;

[0015] Figure 7 This is a schematic diagram of a thermal management system in one embodiment of this application.

[0016] Figure label:

[0017] 100-Heat exchanger; 10-Manifold; 11-Coating; 12-Heat exchange tube; 121-Inner surface of heat exchange tube; 1211-First edge region; 1212-Second edge region; 1213-Middle region; 122-Outer surface of heat exchange tube; 13-Fin; 131-Inner surface of fin; 1311-First outer edge region; 1312-Second outer edge region; 1313-Central region; a1-Fluid inlet; a2-Fluid outlet; 1001-First heat exchanger; 1002-Second heat exchanger; 2-Compressor; 3-Throttling device; 4-Reversing device. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. Based on the technical solutions and embodiments provided in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0019] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the ranges, the endpoint values ​​of the ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges.

[0020] It should be noted that the terms "and / or" or " / " used herein are merely descriptions of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The singular forms "a," "the," and "the" used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0021] In the description of this application, the list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another instance, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements. Furthermore, the terms "at least part of the surface," "at least a portion of the surface," "at least a portion of the surface," or other similar terms mean any part of the surface or the entire surface of the component. For example, at least a portion of the heat exchanger surface means a portion or several parts of the surface of the heat exchanger, or the entire surface of the heat exchanger.

[0022] The present application will be further described in detail below through specific embodiments.

[0023] Currently, most research on heat exchanger coatings focuses on the protective function of surface coatings. For example, by applying hydrophilic or hydrophobic coatings to the heat exchanger surface, condensation and frost formation can be reduced, improving heat exchange efficiency and mitigating corrosion and rust caused by moisture and airborne impurities. Alternatively, substances with antibacterial and antifungal properties can be added to the hydrophilic or hydrophobic coating to reduce the growth of bacteria and mold on the heat exchanger surface, thereby improving heat exchange efficiency and user experience. However, related technologies rarely focus on surface coloring of heat exchangers.

[0024] During the use of heat exchangers, it may be necessary to distinguish between different heat exchangers. For example, when there are more than two heat exchangers in the same module of a thermal management system, and different heat exchangers are used to perform different functions. Most existing heat exchangers are based on the color of the base material, and at most there are slight differences in size or shape, making it difficult to distinguish them by appearance, which causes inconvenience in installation, inspection or maintenance.

[0025] Therefore, in a first aspect, a heat exchanger is provided having a channel for fluid flow, and at least a portion of the surface of the heat exchanger is covered with a colored coating, the colored coating comprising a color additive selected from at least one of organic pigments, inorganic pigments and dyes.

[0026] The heat exchanger of this application has a colored coating on at least part of its surface, facilitating identification, installation, inspection, and maintenance. In practical applications, different colored coatings can be applied to different heat exchangers or different areas of the heat exchanger according to usage requirements, making them easily distinguishable by appearance. The color of the colored coating is achieved by adjusting the type and content of the pigments used. Furthermore, the colored coating isolates the heat exchanger substrate from the external environment, reducing corrosion caused by the external environment, thus improving the durability of the heat exchanger of this application to a certain extent.

[0027] In some embodiments, the color additive is selected from C 18 H 10 C l2 N2O2, C 32 C l16 CuN8, C 32 H 16 CuN8, C 35 H 23 C l2 N3O2, C 12 H 10 N6O4, C 17 H 13 CaC l N4O7S2, at least one of the following: mica, titanium dioxide, tin dioxide, and ferric oxide. That is, the color additive can be selected from C. 18 H 10 C l2 N2O2 (pigment red), C 32 C l16 CuN8 (green), C 32 H 16 CuN8 (blue), C 35 H 23 C l2 N3O2 (purple), C 12 H 10 N6O4 (orange), C 17 H13 CaC l N4O7S2 (yellow), a mixture of mica, titanium dioxide, tin dioxide, and ferric oxide (golden color), or any two or more of these in any proportion. In actual coloring processes, the requirements for colored coatings can vary widely. Some colors may only require one organic pigment, inorganic pigment, or dye, while others may require two or more organic pigments, two or more inorganic pigments, two or more dyes, or a combination of organic pigments, inorganic pigments, and dyes.

[0028] In some embodiments, the particle size of the color additive is 1–5 μm. The smaller the particle size of the color additive, the more uniform and delicate the colored coating, resulting in an aesthetically pleasing colored coating on the heat exchanger surface. Furthermore, the small particle size of the color additive also facilitates its stable adhesion to the heat exchanger surface.

[0029] In some embodiments, the thickness of the colored coating is 8–16 μm. More preferably, the average thickness of the colored coating is 10–11 μm, which is relatively thin and will not have a significant impact on the heat exchange efficiency of the heat exchanger.

[0030] In some embodiments, the standard deviation of the colored coating thickness is less than 0.8 μm. The uniform thickness of the colored coating ensures good consistency in adhesion to the heat exchanger surface, reducing the partial peeling of color additives and the colored coating.

[0031] In some embodiments, the colored coating comprises silica, at least a portion of which has functional groups -(CH2)3-O-CH2-CH-OCH2 and hydroxyl groups -OH on its surface. The addition of silica increases the adhesion and density of the coating, and silica is widely available and inexpensive. The surface functional group -(CH2)3-O-CH2-CH-OCH2 allows for uniform dispersion of silica nanoparticles in the sol, resulting in uniform dispersion of silica nanoparticles in the coating, thereby improving coating uniformity and consistency. The hydroxyl groups -OH make the silica nanoparticles hydrophilic, thus making the colored coating hydrophilic, facilitating water drainage from the coating surface, reducing water accumulation on the coating surface, and minimizing the erosion of the coating by impurities in the water, thereby enabling the coating to maintain strong adhesion to the substrate for a long time. In some embodiments, at least a portion of the silica has a particle size of 55–65 nm.

[0032] In some embodiments, the colored coating further includes titanium dioxide. Titanium dioxide has hydrophilicity and photocatalytic activity; when combined with silicon dioxide, it forms a binary oxide system, enhancing the hydrophilicity and self-cleaning properties of the coating. In some embodiments, at least a portion of the titanium dioxide has a particle size of 5–10 nm.

[0033] For scenarios with only one heat exchanger, colored coatings of the same or different colors can be applied to different locations on the heat exchanger.

[0034] In some embodiments, the colored coating includes a first colored coating and a second colored coating, which are respectively applied to different locations on the surface of the heat exchanger, and the first and second colored coatings have different colors. Thus, different locations or different components of the heat exchanger can be distinguished by the colored coating. For example, the heat exchanger includes a manifold and a heat exchange tube. The manifold is coated with a first colored coating, and the heat exchange tube is coated with a second colored coating. The color of the first colored coating is different from the color of the second colored coating, thus the manifold and heat exchange tube can be easily distinguished by the first and second colored coatings. Alternatively, the heat exchanger has a first channel for the flow of a first fluid and a second channel for the flow of a second fluid. The outer surface of the structure forming the first channel is coated with a first colored coating, and the outer surface of the structure forming the second channel is coated with a second colored coating. The first and second colored coatings have different colors, thus the first and second colored coatings can be easily distinguished by the first and second colored coatings.

[0035] Different colors can be completely different or partially different. Different colors can be due to different chroma, such as red, green, and blue; or different shades, such as dark red and light red; or different gradations, such as colors gradually darkening from the outside to the inside and gradually lightening from the inside to the outside; or different colors presented in other ways.

[0036] In some embodiments of this application, the heat exchanger includes a manifold, fins, and a plurality of heat exchange tubes; the heat exchange tubes are fixed to the manifold, and the inner cavity of the heat exchange tubes communicates with the inner cavity of the manifold; the fins are located between two adjacent heat exchange tubes; a colored coating is applied to at least a portion of the surface of at least one of the manifold, fins, and heat exchange tubes. Thus, different heat exchangers can be distinguished by the appearance color of at least one of the manifold, fins, and heat exchange tubes.

[0037] The heat exchanger of this application is described below by way of example.

[0038] Microchannel heat exchangers, developed in the 1990s, are highly efficient heat exchange devices with wide applications in chemical, energy, and environmental fields. They possess many characteristics that distinguish them from conventional scale equipment, such as small size, light weight, high efficiency, and high strength. Microchannel technology has also triggered technological innovations in areas such as thermal management systems for new energy vehicles, residential air conditioning, commercial air conditioning, and refrigeration equipment, aiming to improve efficiency and reduce emissions.

[0039] For example, such as Figure 1 As shown, the main structure of the microchannel heat exchanger 100 includes two manifolds 10, multiple heat exchange tubes 12, and at least one fin 13. The heat exchange tubes 12 are fixed to the manifolds 10, and their inner cavities communicate with those of the manifolds 10. The multiple heat exchange tubes 12 are arranged along the length / axial direction (X-direction) of the manifolds 10. One end of the heat exchange tube 12 along its length (Y-direction) is connected to one of the two manifolds 10, and the other end is connected to the other manifold. Two adjacent heat exchange tubes and the manifolds together form an external channel for the flow of external fluid. The inner cavity of the heat exchange tube 12 has multiple internal fluid channels extending along its length. The heat exchange tube 12 can be a microchannel flat tube or an elliptical tube. The fin 13 is located between two adjacent heat exchange tubes 12. The fins 13 are wavy along the length of the heat exchange tube 12, and each fin includes several crests and troughs. The crests and troughs of the fins 13 are connected to two adjacent heat exchange tubes, respectively. In some embodiments, a portion of the fins 13 can be provided with a window structure to form louvered fins, further enhancing heat transfer. In some embodiments, the microchannel heat exchanger is an all-aluminum microchannel heat exchanger. The structure of the microchannel heat exchanger and the connection relationships of its various components are conventional knowledge in the art and will not be described in detail here.

[0040] In this application, at least a portion of the surfaces of the manifold 10, heat exchange tube 12, and fins 13 of the heat exchanger 100 are covered with a colored coating 11. Figure 1 A schematic diagram of the colored coating 11 covering the surface of the manifold 10 is shown below. A partial cross-sectional view of the manifold is shown in the figure. Figure 2 As shown.

[0041] In some embodiments, the colored coating applied to at least a portion of the surface of at least one of the manifold, fins, and heat exchange tube has an average thickness, and the thickness of at least a portion of the colored coating applied to at least a portion of the surface of the fins is less than the average thickness; and / or, the thickness of at least a portion of the colored coating applied to at least a portion of the surface of the heat exchange tube is less than the average thickness.

[0042] The colored coating on the heat exchanger in this application differs from hydrophilic, hydrophobic, and antibacterial coatings, which require improvement of the overall surface properties of the heat exchanger. The colored coating is applied to the heat exchanger surface to facilitate visual differentiation. Therefore, in some preferred embodiments, a colored coating is applied to certain surfaces of the heat exchanger, such as... Figure 4 , Figure 5 and Figure 6As shown, the heat exchange tubes form the inner surface 121 of the external channel, and the fins cooperate with the heat exchange tubes to form the inner surface 131 of the external channel. The colored coating does not need to completely cover these surfaces, and the thickness of the colored coating is not limited. On one hand, applying the colored coating has little effect on the appearance of the heat exchanger because the spaces between the two heat exchange tubes and between the heat exchange tubes and the fins are small, making it difficult for light to reach these spaces and creating a certain visual blind spot. Within this blind spot, it is difficult to discern the color of the heat exchanger's surface from its appearance. On the other hand, applying the colored coating to the inner surface of the heat exchanger may affect the heat exchange efficiency.

[0043] In some embodiments, the heat exchanger channel includes an external channel for the flow of external fluid. The heat exchange tube has an inner surface for forming the external channel, the inner surface having an edge region and a central region. The external channel has a fluid inlet and a fluid outlet. The edge region includes a first edge region relative to the central region and closer to the fluid inlet, and a second edge region relative to the central region and closer to the fluid outlet. The central region is located between the first and second edge regions. The thickness of the colored coating applied to the first and second edge regions is greater than or equal to the thickness of the colored coating applied to the central region. In some preferred embodiments, neither the edge region nor the central region of the inner surface of the heat exchange tube is coated with a colored coating.

[0044] In some embodiments, the heat exchanger has internal channels for the flow of internal fluids such as refrigerant and coolant, and external channels for the flow of external fluids such as a heat transfer fluid, such as air. The external fluids are those relative to the refrigerant or coolant flowing through the internal channels. Ideally, the inner surface of the heat exchange tubes should not be coated with a colored coating; in this case, the surface of the heat exchange tubes needs to be masked during spraying. However, during the spraying process of the heat exchanger, to simplify the process and reduce processing costs, the inner surface of the heat exchange tubes may not be masked, and the coating may be applied directly. In this case, the composite material will inevitably be sprayed onto some areas of the inner surface of the heat exchange tubes. During spraying, the spraying direction can be at a certain angle to the inner surface of the heat exchange tubes to reduce the area or thickness of the colored coating on the inner surface of the heat exchange tubes, thereby minimizing the reduction in heat exchange efficiency caused by the colored coating without affecting the appearance color of the heat exchanger.

[0045] For example, such as Figure 3 , Figure 4 and Figure 5As shown, some heat exchange tubes have an inner surface 121 for forming an external channel, and conversely, some heat exchange tubes have an outer surface 122. Typically, for heat exchange tubes arranged on a manifold, only the first and last two heat exchange tubes in the arrangement have an outer surface. Along the fluid flow direction F, the inner surface 121 has a first edge region 1211 near the fluid inlet a1 relative to the middle region 1213 and a second edge region 1212 near the fluid outlet a2 relative to the middle region 1213. The middle region 1213 is located between the first edge region 1211 and the second edge region 1212. The thickness of the colored coating on both the first edge region 1211 and the second edge region 1212 is greater than the thickness of the colored coating on the middle region 1213. In some embodiments, the edge regions and the middle region can have regular shapes, such as rectangles, squares, etc., or the edge regions and the middle region can have irregular shapes, such as... Figure 5 As shown. In some embodiments, the thickness of the colored coating on the inner surface is less than 8 μm.

[0046] In some embodiments, the heat exchanger's channels include external channels for the flow of external fluid. The fins have an inner surface for forming the external channels, the inner surface having an outer edge region and a central region. The external channels have a fluid inlet and a fluid outlet. The outer edge region includes a first outer edge region near the fluid inlet relative to the central region and a second outer edge region near the fluid outlet relative to the central region. The central region is located between the first and second outer edge regions. The thickness of the colored coating applied to the first and second outer edge regions is greater than or equal to the thickness of the colored coating applied to the central region. In some preferred embodiments, neither the outer edge region nor the central region of the fin's inner surface is coated with a colored coating.

[0047] Ideally, the inner surface of the fins should not be coated with a colored coating; in this case, the fin surface needs to be masked. However, during the heat exchanger spraying process, to simplify the process and reduce costs, the inner surface of the fins can be sprayed directly without masking. In this case, the composite material will inevitably be sprayed onto some surfaces of the fins. During spraying, the spraying direction can be at a certain angle to the inner surface of the fins to reduce the area or thickness of the colored coating on the fins. This minimizes the reduction in heat exchange efficiency caused by the colored coating without affecting the appearance of the heat exchanger.

[0048] For example, such as Figure 3 , Figure 4 and Figure 6As shown, the fin has an inner surface 131. Along the fluid flow direction F, the inner surface 131 has an outer edge region and a central region. The outer edge region includes a first outer edge region 1311 that is closer to the fluid inlet a1 relative to the central region 1313, and a second outer edge region 1312 that is closer to the fluid outlet a2 relative to the central region 1313. The central region 1313 is located between the first outer edge region 1311 and the second outer edge region 1312. The thickness of the colored coating applied to the first outer edge region 1311 and the second outer edge region 1312 is greater than the thickness of the colored coating applied to the central region 1313. In some embodiments, the outer edge region and the central region may have regular shapes, such as rectangles, squares, etc., or the outer edge region and the central region may have irregular shapes, such as... Figure 6 As shown.

[0049] In some embodiments, the thickness of the colored coating on the inner surface of the fin is less than 8 μm.

[0050] A second aspect of this application provides a method for manufacturing a heat exchanger, the method comprising:

[0051] We provide composite materials, including sol-gels and color additives;

[0052] The composite material is coated and cured to form a colored coating on at least a portion of the surface of the heat exchanger.

[0053] In some embodiments of this application, the composite material coating heat exchanger is carried out by at least one of dip coating, spray coating, brush coating, curtain coating or roller coating.

[0054] In some preferred embodiments, the composite material is coated onto the heat exchanger surface using a spraying method. The colored coating on the heat exchanger surface aims to color the surface, unlike hydrophilic, hydrophobic, and antibacterial coatings that need to be applied to the entire outer surface. The colored coating is applied only to the visible area of ​​the outer surface. The outer surface refers to the surface exposed to the external environment. For microchannel heat exchangers, the outer surface includes the surfaces of components such as manifolds, heat exchange tubes, and fins that come into contact with the external heat exchange medium, such as air. However, some areas of the outer surface, such as the inner surfaces of the heat exchange tubes and fins, are visually obscure due to the difficulty in obtaining light, making it difficult to discern their color. Therefore, it is preferable to leave these areas uncoated or with minimal coating. The spraying method allows for selective application of the coating area on the outer surface, thus achieving minimal or no coating on the inner surfaces of the heat exchange tubes and fins.

[0055] In some embodiments, the spraying direction is parallel to at least a portion of the surface of the heat exchange tube, and / or, the spraying direction is parallel to at least a portion of the surface of the fins. Thus, during spraying, the surfaces of the fins / heat exchange tube parallel to the spraying direction are less likely to be coated with the composite material, thereby reducing the likelihood of forming a colored coating and facilitating minimal or no coating on the inner surfaces of the heat exchange tube and fins. In some embodiments, the spraying direction is parallel to at least a portion of the inner surface of the heat exchange tube, and / or, the spraying direction is parallel to at least a portion of the inner surface of the fins.

[0056] In some embodiments, the spraying direction is perpendicular to the windward side of the heat exchanger. The external environment exchanges heat with the fluid (e.g., refrigerant, coolant, etc.) inside the heat exchanger through a heat transfer medium (e.g., air). When the external heat transfer medium passes through the heat exchanger, the surface that first contacts the external heat transfer medium is the windward side of the heat exchanger.

[0057] The curing method may include, for example, drying in an oven. In some embodiments, the curing temperature is 180°C to 220°C; more preferably, the curing temperature is 190°C to 210°C; even more preferably, the curing temperature is 200°C. In some embodiments, the curing time is 5 to 75 minutes; more preferably, the curing time is 10 to 60 minutes.

[0058] In some embodiments, the method for preparing the heat exchanger includes: performing a surface pretreatment on the heat exchanger before coating it with the composite material. Specifically, in some embodiments, the surface pretreatment includes: sandblasting the surface of the heat exchanger with a 100-200 mesh, cleaning the surface of the heat exchanger with alcohol or acid, and then air-drying or drying at 35°C-50°C. Sandblasting can increase the roughness of the heat exchanger surface, thereby making the adhesion of the colored coating on the heat exchanger surface more stable. In some embodiments, the sandblasting mesh is 120-180 mesh, such as 150 mesh. In some embodiments, the drying temperature is 40°C. The cleaning method used may be, for example, ultrasonic cleaning or blasting with anhydrous ethanol, or acid etching.

[0059] A third aspect of this application provides a thermal management system, comprising a compressor 2, a first heat exchanger 1001, a throttling device 3, and a second heat exchanger 1002. The surface color of the first heat exchanger 1001 is different from the surface color of the second heat exchanger 1002. When refrigerant flows through the thermal management system, the refrigerant flows into the first heat exchanger 1001 via the compressor 2, and after heat exchange occurs in the first heat exchanger 1001, it flows into the throttling device 3. Then, the refrigerant flows into the second heat exchanger 1002, and after heat exchange occurs in the second heat exchanger 1002, it flows back into the compressor 2. Figure 7As shown. Since the surfaces of the first heat exchanger 1001 and the second heat exchanger 1002 have different colors—for example, the first heat exchanger surface is red and the second heat exchanger surface is green—the first heat exchanger and the second heat exchanger can be easily distinguished by appearance. In some embodiments, the first heat exchanger 1001 is a condenser and the second heat exchanger 1002 is an evaporator. In some embodiments, the thermal management system also includes a reversing device 4.

[0060] In some embodiments, at least a portion of the surface of one of the first heat exchanger 1001 and the second heat exchanger 1002 is coated with a colored coating, the color of which is different from the color of the substrate of both the first heat exchanger 1001 and the second heat exchanger 1002; or, at least a portion of the surface of the first heat exchanger 1001 is coated with a third colored coating, and at least a portion of the surface of the second heat exchanger 1002 is coated with a fourth colored coating, the color of which is different from the color of the fourth colored coating. Thus, by coating one of the two heat exchangers with a colored coating, the first heat exchanger and the second heat exchanger are distinguished by the difference in color between the colored coating and the heat exchanger substrate; or, by coating the surfaces of the two heat exchangers with different colored coatings, the first heat exchanger and the second heat exchanger are distinguished by the different colors of the colored coatings.

[0061] For heat exchanger surface coloring technology, existing TCP (chromium peroxide) technology can provide obvious coating color changes, such as silver, blue, or purple, by adding commercially available color additives. However, recent studies have found trace amounts of hexavalent chromium (Cr) in TCP. 6+ It poses a significant health hazard to operators. The EU RoHS environmental organization completely banned the commercial application of hexavalent chromium conversion membranes in 2017, necessitating the development of relevant alternative processes.

[0062] Therefore, this application uses composite materials to form a colored coating on the heat exchanger surface. Compared to TCP coloring technology, coloring the heat exchanger surface with composite materials is environmentally friendly and greatly reduces the threat of the coating to the health of operators and users.

[0063] Composite materials used to form colored coatings on heat exchanger surfaces can be commercially available or homemade. However, many existing composite materials, including their sol components and the ratio of sol to color additives, are designed for substrates such as glass, ceramics, and steel plates used at room or constant temperatures. These cannot be directly applied to heat exchanger surfaces, or their application is ineffective. Heat exchangers are devices that heat or cool the external environment through heat transfer between the internal fluid and the external environment. During operation, the surface coating of a heat exchanger undergoes more frequent heating and cooling cycles due to the temperature difference between the internal fluid and the external environment. Compared to coatings on surfaces such as glass, ceramics, and colored steel plates used at room or constant temperatures, coatings applied to heat exchanger surfaces require stronger adhesion and durability to reduce the detachment of color additives or the entire colored coating.

[0064] Therefore, in a fourth aspect of this application, a composite material is provided that can form a colored coating with strong adhesion and good durability on the surface of a heat exchanger. The composite material includes a sol and a color additive, wherein the sol includes an alcohol solvent.

[0065] For some existing composite materials, after the formation of a colored coating, the partial detachment of the color additives or the colored coating itself is not due to insufficient adhesive strength, but rather to poor dispersibility of the color additives, leading to agglomeration and aggregation of some color additives within the composite material. After the colored coating is formed, the outer surface of the color additive aggregates can fully contact the adhesive material, but the color additives inside the aggregates cannot fully contact the adhesive material, or may even be isolated from it. Therefore, the bonding between the color additive aggregates and the substrate mainly relies on the adhesive material bonded to their outer surface. However, this portion of adhesive material is insufficient relative to the overall weight and volume of the color additive aggregates to permanently adhere them to the substrate. After a period of use, these color additive aggregates detach, sometimes even dragging the adhesive material within the coating, causing the entire coating to detach from the substrate, resulting in spots with peeling marks on the colored coating and affecting the product's appearance. In other cases, even if the color additives can adhere to the substrate, the aggregates can cause uneven coating thickness, resulting in an uneven coating surface. This affects the product's appearance, and the uneven surface makes the coating more susceptible to adhering to impurities from water or air. These impurities can corrode the coating and affect its service life.

[0066] The composite material of this application includes a sol and a color additive, which can form a colored coating on the substrate surface. During the formation of the colored coating, the sol forms an adhesive substance that firmly adheres the color additive to the substrate. The alcohol solvent in the sol ensures uniform dispersion of the color additive, thereby enabling it to be evenly distributed throughout the colored coating. This reduces the agglomeration of the color additive in certain areas of the coating, improves the consistency of the bonding force between the color additive and the adhesive substance, and enhances the consistency of the coating's adhesion to the substrate surface. Consequently, the thickness, unit weight, and adhesion of the colored coating also exhibit good consistency, reducing the likelihood of some color additives or coating peeling off from the substrate surface due to weak bonding or adhesion. This results in a colored coating on the substrate surface that provides durable decoration and protection.

[0067] In some embodiments, the alcohol solvent is derived from the sol, and / or the alcohol solvent is an additionally added solvent. "Alcohol solvent derived from the sol" means that at least a portion of the sol uses an alcohol solvent during preparation, and / or the sol generates the alcohol solvent through a chemical reaction or other type of reaction during preparation, and the alcohol solvent remains at least partially in the sol after preparation. The alcohol solvent is an additionally added solvent; for example, the alcohol solvent can be mixed into the sol as long as it does not disrupt the colloidal structure of the sol. In some embodiments, the sol includes an alcohol-soluble sol, in which colloidal particles are dispersed in an alcohol solvent.

[0068] In some embodiments, the alcohol solvent includes alcohol compounds having 1 to 10 carbon atoms, preferably alcohol compounds having 1 to 8 carbon atoms, and more preferably alcohol compounds having 1 to 4 carbon atoms. In some embodiments, the alcohol solvent may be any one or a mixture of any two or more of methanol, ethanol, isopropanol, benzyl alcohol, and ethylene glycol in any proportion.

[0069] In some embodiments, the composite material comprises 90-99 parts by weight of sol and 1-10 parts by weight of color additives, wherein the proportion of alcohol solvent in the sol is 15%-30%.

[0070] 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.

[0071] According to embodiments of this application, the composite material comprises 90 to 99 parts of sol, typically but not limitingly, for example, 90.1 parts, 90.2 parts, 90.5 parts, 91 parts, 93 parts, 95 parts, 97.5 parts, 98.8 parts, and any value within the range formed by any two of these point values.

[0072] According to embodiments of this application, the composite material includes 1 to 10 parts of color additive. Typical but non-limiting examples include 1.1 parts, 1.5 parts, 2 parts, 3 parts, 5 parts, 5.6 parts, 6.1 parts, 7 parts, 8 parts, 9 parts, 9.2 parts, 9.9 parts, and any value within the range formed by any two of these point values. The 1 to 10 parts of color additive can be 1 to 10 parts of organic pigment or 1 to 10 parts of inorganic pigment, or it can be organic pigment, inorganic pigment, and dye mixed in any proportion to form 1 to 10 parts of color additive.

[0073] According to embodiments of this application, the proportion of alcohol solvents in the sol is a percentage by parts. For example, if the alcohol solvent is 10 parts and the total sol volume is 100 parts, then the proportion of alcohol solvents in the sol is 10%. For instance, when the sol only includes alcohol-soluble sols, the proportion of alcohol solvents in the sol refers to the proportion of alcohol solvents in the alcohol-soluble sol. When the sol includes not only alcohol-soluble sols but also other types of sols, the proportion of alcohol solvents in the sol refers to the proportion of alcohol solvents in the total sol volume. For example, if the sol includes both alcohol-soluble and water-soluble sols, the proportion of alcohol solvents in the sol refers to the proportion of alcohol solvents in the mixed sol composed of alcohol-soluble and water-soluble sols.

[0074] The content of color additives determines the color concentration of the composite material and the depth of the final colored coating. Too little color additive results in minimal color change to the substrate surface, requiring multiple coats to achieve the desired color, or even failing to achieve the desired color at all. Too much color additive, on the other hand, may lead to poor dispersion in the sol, thus affecting the overall performance of the coating. Alcohol solvents improve pigment dispersibility; generally, higher alcohol solvent content results in better pigment dispersion in the sol. More color additives require a corresponding increase in alcohol solvent to ensure adequate pigment dispersion in the sol. However, the composite material of this application, used to form a colored coating on a product surface, must consider not only the dispersibility of the color additives but also the bonding force between the color additives and the adhesive substances, as well as the overall adhesion of the colored coating to the substrate. The bonding force between the color additives and the adhesive substances, and the adhesion of the colored coating to the substrate, primarily depend on the adhesive substances in the sol, other than alcohol solvents, such as colloidal particles with surface-bonded organic functional groups. With a high proportion of color additives and alcohol solvents, the amount of substances used for adhesive bonding is relatively low. Insufficient content of substances used for adhesive bonding will lead to a deterioration in the adhesion performance of the coating.

[0075] This application selects the ratio of sol and color additives and the content of alcohol solvent in the sol within the above-mentioned range, comprehensively considering the performance indicators of the colored coating formed by the composite material, such as the coloring effect of the colored coating, the compatibility and bonding force between the sol and the color additives, the adhesion of the colored coating to the substrate, the thickness of the coating, and the uniformity of coating thickness, color, and unit weight. This ensures that the color of the composite material has a wide color range and that the coating has excellent comprehensive performance, reducing the peeling of pigments or coating parts, thereby enabling the colored coating to provide stable, durable, and uniform coloring to the product substrate.

[0076] In some embodiments, the sol also includes a water solvent, which accounts for 10% to 40% of the sol. When coating composite materials, alcohol solvents evaporate relatively quickly. To ensure good coating performance of the composite material on the substrate surface and to prevent uneven coating surfaces caused by excessively rapid solvent evaporation and surface drying of the composite material during spraying, the sol also includes water with a slow evaporation rate.

[0077] In some embodiments, the aqueous solvent is derived from the sol, and / or the aqueous solvent is an additionally added solvent. "A aqueous solvent derived from the sol" means that at least a portion of the sol uses an aqueous solvent during its preparation, and / or the sol generates the aqueous solvent through a chemical reaction or other type of reaction during its preparation, and the aqueous solvent remains at least partially in the sol after preparation. The aqueous solvent is an additionally added solvent; for example, it can be mixed into the sol as long as it does not disrupt the colloidal structure of the sol. In some embodiments, the sol includes a water-soluble sol. A water-soluble sol refers to a sol in which colloidal particles are dispersed in water.

[0078] In some embodiments, the alcohol solvent accounts for 20% to 26% of the sol, and the water solvent accounts for 30% to 36%. In some embodiments, the alcohol solvent accounts for 24% of the sol, and the water solvent accounts for 34%.

[0079] In some embodiments, the sol contains silica nanoparticles, wherein at least a portion of the silica nanoparticles have functional groups -(CH2)3-O-CH2-CH-OCH2 and hydroxyl groups -OH bound to their surfaces. The surface functional group -(CH2)3-O-CH2-CH-OCH2 ensures uniform dispersion of the silica nanoparticles in the sol, resulting in uniform dispersion of silica nanoparticles in the coating, thereby improving coating uniformity and consistency. The hydroxyl groups -OH make the silica nanoparticles hydrophilic, thus making the colored coating hydrophilic, facilitating water drainage from the coating surface, reducing the accumulation of large amounts of water on the coating surface, and reducing the erosion of the coating by impurities in the water, thereby enabling the coating to maintain strong adhesion to the substrate for a long time. In some embodiments, at least a portion of the silica nanoparticles have a particle size of 55–65 nm. In some embodiments, the sol comprises an alcohol-soluble sol containing silica nanoparticles, the surface of which is bound with functional groups -(CH2)3-O-CH2-CH-OCH2 and hydroxyl groups -OH. Alcohol-soluble sols refer to colloidal particles dispersed in alcohol solvents.

[0080] In some embodiments, the sol contains titanium dioxide nanoparticles. The addition of titanium dioxide nanoparticles allows silicon dioxide and titanium dioxide to form a binary oxide system in the sol. The interaction and substitution of titanium and silicon atoms in different coordination states can stabilize the Ti-O and Si-O structures, thereby enhancing the adhesion of the sol and improving the hydrophilicity of the coating. In some embodiments, at least some of the titanium dioxide nanoparticles have a particle size of 5–10 nm.

[0081] In some embodiments, the color additive is selected from at least one of organic pigments, inorganic pigments, and dyes. In some embodiments, the color additive is selected from C 18 H 10 C l2 N2O2, C 32 C l16 CuN8, C 32 H 16 CuN8, C 35 H 23 C l2 N3O2, C 12 H 10 N6O4, C 17 H 13 CaC l N4O7S2, at least one of the following: mica, titanium dioxide, tin dioxide, and ferric oxide. That is, the color additive can be selected from C. 18 H 10 C l2 N2O2 (red), C 32 C l16CuN8 (green), C 32 H 16 CuN8 (blue), C 35 H 23 C l2 N3O2 (purple), C 12 H 10 N6O4 (orange), C 17 H 13 CaC l N4O7S2 (yellow), a mixture of mica, titanium dioxide, tin dioxide, and ferric oxide (golden color), or any two or more of these in any proportion. In actual coloring processes, the color requirements for colored coatings can vary widely. Some colors may only require one organic pigment, inorganic pigment, or dye, while others may require two or more organic pigments, two or more inorganic pigments, two or more dyes, or a combination of organic pigments, inorganic pigments, and dyes. The selection of color additives should be based on their ability to mix with the sol to achieve the desired color.

[0082] A fifth aspect of this application provides a method for preparing a composite material, the method comprising: mixing 90-99 parts of sol with 1-10 parts of color additive, wherein the sol comprises an alcohol solvent, and the alcohol solvent accounts for 15%-30% of the sol.

[0083] The preparation method of this application uses a sol with an appropriate alcohol solvent ratio and mixes the sol and color additives in an appropriate ratio to make the color additives uniformly dispersed in the sol, reducing the agglomeration of color additives, thereby preparing a composite material with excellent coating performance. This composite material can form a colored coating with good consistency in film thickness, color, and adhesion, strong adhesion, and good durability, thereby reducing the peeling off of some color additives or coatings from the substrate due to weak bonding or adhesion caused by pigment additive agglomeration.

[0084] It should be understood that the preparation method of this composite material is based on the same inventive concept as the aforementioned composite material. For the relevant characteristics such as the raw material composition and proportion of the composite material, please refer to the description of the aforementioned composite material section, which will not be repeated here.

[0085] The above-mentioned methods of mixing the sol and color additives include, but are not limited to, mechanical mixing. In other embodiments, various commonly used mixing methods known in the art can also be used, such as ultrasonic mixing or a combination of mechanical and ultrasonic mixing. This application does not impose any special limitations on this, as long as the sol can be mixed evenly with the color additives.

[0086] In some specific embodiments, the preparation method of the composite material includes: mechanically mixing the sol and color additive for 10-30 minutes. In this application, the sol and color additive can be mechanically mixed for 10 minutes, 12 minutes, 15 minutes, and 30 minutes, until the sol and color additive are uniformly mixed.

[0087] In some embodiments, the method for preparing the composite material further includes: sanding or grinding after mixing the sol with the color additive.

[0088] Sanding or grinding can give pigment additives a smaller particle size, resulting in a finer and more uniform color in the colored coating. After mixing the sol with the color additive, the method for refining the particle size of the color additive is not limited to sanding or grinding; other laboratory or industrial methods can also be used. Generally, the longer the sanding or grinding time, the smaller the particle size of the color additive and the more uniform and delicate the colored coating. However, considering cost, the particle size of the color additive should only be small enough to meet the application requirements.

[0089] In some specific embodiments, the preparation method of the composite material includes: after mixing the sol and color additives, grinding them using a sand mill for 10 to 60 minutes. In this application, specifically, the sand milling or grinding time can be set to any value within a range of 10 minutes, 11 minutes, 15 minutes, 20 minutes, 30 minutes, 45 minutes, 60 minutes, or any two of these values, depending on the particle size of the desired color additives, etc.

[0090] According to embodiments of this application, there are no special restrictions on the source of the sol and color additives; they can be prepared in-house or commercially available products. In other embodiments, at least one of the color additives and sol can be commercially available. Embodiments of this application also do not limit the preparation order of the color additives and sol. For example, in the preparation process of the composite material, the color additive can be prepared first, followed by the sol; or, the sol can be prepared first, followed by the color additive; or, the color additive and sol can be prepared simultaneously.

[0091] In some embodiments of this application, the sol in the composite material is prepared in-house. The preparation method of the sol is described below.

[0092] In some embodiments, the method for preparing the composite material further includes preparing an alcohol-soluble silica sol, wherein the alcohol-soluble silica sol comprises silica nanoparticles dispersed in an alcohol solvent, and the surface of the silica nanoparticles is bound with functional groups -(CH2)3-O-CH2-CH-OCH2 and hydroxyl groups -OH. The method for preparing the alcohol-soluble silica sol includes: mixing a silane precursor, an alcohol solvent, a surfactant, water and a pH adjuster, and reacting them in a water bath to obtain the alcohol-soluble silica sol.

[0093] In some embodiments, the method for preparing the alcohol-soluble silica sol includes: mixing 36-40 parts by weight of a silane precursor, 50-56 parts by weight of an alcohol solvent, 0.5-1.5 parts by weight of a surfactant, 5-7 parts by weight of water, and 0.5-2 parts by weight of a pH adjuster, and reacting the mixture in a water bath to obtain an alcohol-soluble silica sol, wherein at least a portion of the silane precursor contains the functional group -(CH2)3-O-CH2-CH-OCH2. For example, the mass fraction of the silane precursor may be 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, etc.; the mass fraction of the alcohol solvent may be 50 parts, 51 parts, 52 parts, 53 parts, 54 parts, 55 parts, 56 parts, etc.; the mass fraction of the surfactant may be 0.5 parts, 0.8 parts, 1 part, 1.2 parts, 1.5 parts, etc.; the mass fraction of water may be 5 parts, 5.5 parts, 6.5 parts, 7 parts, etc.; and the mass fraction of the pH adjuster may be 0.5 parts, 1 part, 1.2 parts, 1.5 parts, 1.6 parts, 1.8 parts, 2 parts, etc. In some embodiments, the mixing temperature is 45°C to 55°C. For example, the mixing temperature is 45°C, 46°C, 48°C, 50°C, 52°C, 54°C, 55°C, etc.

[0094] In some embodiments, the silane precursor comprises glycidoxypropyltrimethoxysilane (KH-560) and tetraethyl orthosilicate. Thus, the silica nanoparticles contained in the prepared sol have functional groups -(CH2)3-O-CH2-CH-OCH2 and hydroxyl groups -OH on their surface. In other embodiments, other types of silane precursors may also be used.

[0095] In some embodiments, the silane precursor comprises 30 to 32 parts of γ-glycidoxypropyltrimethoxysilane (KH-560) and 6 to 8 parts of tetraethyl orthosilicate. For example, the mass fraction of KH-560 may be 30, 31, or 32 parts; and the mass fraction of tetraethyl orthosilicate may be 6, 7, or 8 parts.

[0096] In some embodiments, the alcohol solvent includes alcohol solvents with 1 to 10 carbon atoms, preferably alcohol solvents with 1 to 8 carbon atoms, and more preferably alcohol solvents with 1 to 4 carbon atoms. Further, in some embodiments, the solvent is any one or a mixture of any two or more of methanol, ethanol, isopropanol, benzyl alcohol, and ethylene glycol in any proportion. Therefore, it is widely available, readily accessible, and low in cost.

[0097] In some embodiments, the surfactant includes, but is not limited to, at least one selected from sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, and hexadecylbenzene sulfonic acid. Further, in some embodiments, the surfactant is sodium dodecyl sulfate. Therefore, it is low in cost, widely available, and has good performance.

[0098] In some embodiments, the pH adjuster includes an organic acid or an inorganic acid. In some embodiments, the pH adjuster includes, but is not limited to, at least one of formic acid and acetic acid. Further, in some embodiments, the pH adjuster is formic acid.

[0099] The equations or reaction mechanisms involved in the preparation of the alcohol-soluble silica sol in this application are as follows:

[0100] 1) Hydrolysis and condensation of tetraethyl orthosilicate: Si(OCH2CH3)4 + 2H2O → SiO2 + 4C2H5OH.

[0101] 2) Hydrolysis of KH560: R-Si(OCH3)3 + 3H2O → R-Si(OH)3 + CH3OH

[0102] KH560 polycondensation: R-Si(OH)3+R-Si(OH)3→R-Si(OH)2-O-Si(OH)2-R+H2O

[0103] R-Si(OH)3+R-Si(OCH3)3→R-Si(OH)2-O-Si(OH)2-R+CH3OH

[0104] Where R represents the long-chain group -(CH2)3-O-CH2-CH-OCH2 in KH560, and KH560 has the following structural formula (I):

[0105]

[0106] 3) Condensation of KH560 with silanol groups: R-Si(OH)3+Si(OH)4→R-Si(OH)2-O-Si(OH)3+H2O.

[0107] The silica nanoparticles in the sol prepared in this application are synthesized in situ and have functional groups -(CH2)3-O-CH2-CH-OCH2 on their surface, resulting in a uniform distribution of silica nanoparticles in the coating formed by the composite material, thereby improving the uniformity and consistency of the coating. The alcohol-soluble silica sol prepared in this application can form a film independently on the substrate surface. Because the surface of the silica nanoparticles contains a large number of hydrophilic hydroxyl (-OH) groups, the hydroxyl groups undergo dehydration condensation to form a spatial network structure. Since the silica sol is an alcohol-soluble sol prepared using alcohol solvents, the alcohol solvents can uniformly disperse the color additives. During the formation of the colored coating in the composite material, the silica sol undergoes dehydration condensation, which can uniformly adhere the color additives and the silica nanoparticles themselves to the substrate surface, forming a colored coating with strong adhesion, film thickness, uniform color, and good durability. In addition, the hydroxyl groups on the surface of silica nanoparticles make the coating hydrophilic, which enhances the drainage effect of the colored coating, reduces the erosion of the coating by external water or impurities in the air, and further improves the durability of the colored coating.

[0108] In some embodiments, the preparation method of the alcohol-soluble silica sol includes: weighing 50-56 parts by weight of an alcohol solvent and 0.5-1.5 parts by weight of a surfactant, and ultrasonically dispersing them; adding 36-40 parts by weight of a silane precursor, and mixing in a water bath; adding 5-7 parts by weight of water and 0.5-2 parts by weight of a pH adjuster, and reacting in a water bath to obtain the alcohol-soluble silica sol, wherein at least a portion of the silane precursor contains the functional group -(CH2)3-O-CH2-CH-OCH2. The alcohol-soluble silica sol prepared in the embodiments of this application has good compatibility with color additives, the color additives can be well dispersed therein, and the preparation process is simple.

[0109] In some embodiments, the preparation method of the sol includes: weighing 50-56 parts by weight of an alcohol solvent and 0.5-1.5 parts by weight of a surfactant, and ultrasonically dispersing for 5-15 min; adding 36-40 parts by weight of a silane precursor, mixing in a water bath at 40-60°C for 20-40 min, and stirring at 200-300 rpm; adding 5-7 parts by weight of water and 0.5-2 parts by weight of a pH adjuster, controlling the addition to be completed within 5-15 min, and reacting in a water bath for 22-26 h to obtain an alcohol-soluble silica sol, wherein at least a portion of the silane precursor contains the functional group -(CH2)3-O-CH2-CH-OCH2.

[0110] In some embodiments, the method for preparing the sol further includes adding filler to the sol.

[0111] Adding fillers to a sol can increase viscosity, reduce coating permeability, and improve coating durability. Typically, powdered fillers are mixed into coatings to improve coating performance, such as adhesion and durability. However, powders often have poor dispersion in sols, leading to poor coating uniformity and increasing the likelihood of fillers or color additives peeling off.

[0112] This application incorporates fillers into the sol via sol-gel mixing. This approach facilitates uniform dispersion of the fillers and, because the fillers are prepared using the sol-gel method, their surfaces are coated with functional groups, resulting in stronger adhesion to the substrate after coating formation compared to dry powder fillers. In some embodiments, the sol preparation method includes mixing water-soluble silica sol and titanium dioxide sol with the aforementioned alcohol-soluble silica sol, wherein the solid content of the mixture of water-soluble silica sol and titanium dioxide sol is greater than the solid content of the alcohol-soluble silica sol. The solid content of the mixture of water-soluble silica sol and titanium dioxide sol refers to the solid content of the mixed sol obtained after mixing the water-soluble silica sol and titanium dioxide sol. For example, the solid content of water-soluble silica sol is x1%, and its proportion in the mixed sol is y1%. The solid content of titanium dioxide sol is x2%, and its proportion in the mixed sol is y2%. The sum of y1% and y2% is 1, so the total solid content of the mixture is x1%·y1% + x2%·y2%. Silica in the water-soluble silica sol and titanium dioxide in the titanium dioxide sol act as fillers, added to the alcohol-soluble silica sol through sol mixing. The water-soluble solvent in the water-soluble silica sol can enhance the coating performance of the composite material and prevent uneven coating surfaces caused by excessively rapid solvent evaporation and fast surface drying of the composite material during spraying.

[0113] In some embodiments, the silica nanoparticles in the water-soluble silica sol have a particle size of 55–65 nm and a solid content of 45%–55%. In some embodiments, the silica nanoparticles in the alcohol-soluble silica sol have a smaller particle size than those in the water-soluble silica sol. In some embodiments, the silica nanoparticles in the silica sol have a particle size of 60 nm and a solid content of 50%. In some embodiments, the pH of the water-soluble silica sol is 9.

[0114] In some embodiments, the silica nanoparticles in the titanium dioxide sol have a particle size of 5–10 nm and a solid content of 2%–4%.

[0115] In some embodiments, the titanium dioxide sol is a water-soluble sol or an alcohol-soluble sol.

[0116] In some embodiments, the method for preparing the sol includes: mixing alcohol-soluble silica sol, water-soluble silica sol, and titanium dioxide sol; adjusting the pH to acidic using a pH adjuster; and stirring in a water bath. The pH adjuster includes organic or inorganic acids. Specifically, in some embodiments, the pH adjuster is formic acid. Thus, the prepared mixed sol exhibits good homogeneity, and both silica nanoparticles and titanium dioxide nanoparticles are uniformly dispersed within the sol.

[0117] In some embodiments, the method for preparing the sol includes: weighing water-soluble silica sol, alcohol-soluble silica sol and titanium dioxide sol, adjusting the pH to 3.0-4.0 with a pH adjuster, and stirring in a water bath at 40-60°C for 3-5 hours.

[0118] In some embodiments, the method for preparing the sol includes: weighing 34-36 parts of alcohol-soluble silica sol, 55-57 parts of water-soluble silica sol, and 4-6 parts of titanium dioxide sol; adjusting the pH to 3.0-4.0 with 3-5 parts of pH adjuster; and stirring in a water bath at 40-60°C for 3-5 hours. According to embodiments of this application, the mass fraction of the alcohol-soluble sol is 34-36 parts, typically but not limitingly, for example, 34 parts, 34.5 parts, 34.8 parts, 35 parts, 35.5 parts, 36 parts, and any value within the range formed by any two of these values. According to embodiments of this application, the mass fraction of the silica sol is 55-57 parts, typically but not limitingly, for example, 55.5 parts, 56 parts, 56.5 parts, 57 parts, and any value within the range formed by any two of these values. According to the embodiments of this application, the mass fraction of the titanium dioxide sol is 4 to 6 parts, typically but not limitingly, for example, 4 parts, 4.5 parts, 5 parts, 5.5 parts, and any value within the range formed by any two of these point values. The ratio of alcohol-soluble silica sol, water-soluble silica sol, and titanium dioxide sol is selected within this range, comprehensively considering the dispersibility of pigment additives and fillers in the sol in the composite material, the bonding force between pigment additives and fillers and the substrate in the colored coating, and the density and uniformity of the coating. The resulting coating exhibits uniform distribution of pigment additives and fillers, good uniformity, and strong adhesion.

[0119] To fully illustrate the relevant properties of the composite materials provided in this application and to facilitate understanding of the invention, multiple sets of experiments were conducted for verification. The invention is further described below with reference to specific embodiments and comparative examples. Those skilled in the art will understand that the examples described in this application are only a portion of the examples, and any other suitable specific examples are within the scope of this application.

[0120] Example 1

[0121] 1. Preparation of composite materials

[0122] In this embodiment, the sol includes alcohol-soluble silica sol, water-soluble silica sol, and titanium dioxide sol. The alcohol-soluble silica sol is prepared in-house and appears as a transparent sol, containing approximately 54% anhydrous ethanol. Both the water-soluble silica sol and titanium dioxide sol are commercially available products, with the titanium dioxide sol also being a water-soluble sol. The water-soluble silica sol has colloidal particles with a particle size of 55–65 nm, a solid content of approximately 50%, and a pH of 9. The titanium dioxide sol has colloidal particles with a particle size of 5–10 nm and a solid content of approximately 3%. The color additive is commercially available Pigment Red 254, with a chemical composition of C. 18 H 10 C l2 N2O2.

[0123] A) Preparation of sol

[0124] (a1) Preparation of alcohol-soluble sol

[0125] Alcohol-soluble sols refer to sols in which colloidal particles are dispersed in an alcohol solvent. By mass, 54 parts anhydrous ethanol and 1 part sodium dodecyl sulfate were ultrasonically dispersed for 10 min; then 31 parts KH-560 and 7 parts tetraethyl orthosilicate were added, and the mixture was mechanically stirred at 250 rpm for 30 min in a 50°C water bath. Next, 6 parts water and 1 part formic acid were added dropwise to the system, completing the addition within 10 min. The mixture was then reacted at 50°C for 24 h to obtain an alcohol-soluble silica sol. The silica nanoparticles contained in the alcohol-soluble silica sol have functional groups -(CH2)3-O-CH2-CH-OCH2 and hydroxyl groups -OH on their surface.

[0126] (a2) Mix the alcohol-soluble sol and the water-soluble sol.

[0127] 35 parts of the alcohol-soluble silica sol, 56 parts of the water-soluble silica sol, and 5 parts of the water-soluble titanium dioxide sol prepared in step (a1) were mixed evenly. The pH of the system was adjusted to approximately 3.0 using 4 parts of formic acid as a pH adjuster. The mixture was stirred and reacted in a water bath at approximately 50°C for about 4 hours to obtain the sol. After mixing, the anhydrous ethanol content in the mixed sol was approximately 24%, of which 18.9% was anhydrous ethanol added during the preparation of the alcohol-soluble sol.

[0128] B) Mix the sol with the color additives

[0129] By weight, 95 parts of sol and 5 parts of red pigment were mechanically mixed for 20 minutes and then sand-milled for 30 minutes to obtain the composite material.

[0130] 2. Preparation of heat exchangers

[0131] Pretreatment of the heat exchanger surface to be coated includes: sandblasting the heat exchange tube surface with 150 mesh, then washing the heat exchange tube and / or fin surface with anhydrous ethanol, and drying at 40°C for later use.

[0132] The composite material obtained in step 1 is sprayed onto the pretreated surface of the heat exchanger and cured at 200°C for 30 minutes to obtain a heat exchanger with a red coating.

[0133] Examples 2-7

[0134] The composite material and heat exchanger were prepared in the same manner as in Example 1, except for the type of color additive and / or the ratio of sol to color additive.

[0135] In Example 2, 95 parts of sol and 5 parts of Pigment Green 7 were mixed. The main chemical composition of Pigment Green 7 is C. 32 C l16 CuN8.

[0136] In Example 3, 95 parts of sol and 5 parts of Pigment Blue 15:3 were mixed. The main chemical composition of Pigment Blue 15:3 is C. 32 H 16 CuN8.

[0137] In Example 4, 95 parts of sol and 5 parts of pigment violet 23 were mixed. The main chemical composition of pigment violet 23 is C. 35 H 23 Cl2N3O2.

[0138] In Example 5, 92 parts of sol and 8 parts of gold pigment were mixed, wherein the gold pigment was a mixture of mica, titanium dioxide, tin dioxide and ferric oxide.

[0139] In Example 6, 90 parts of sol and 10 parts of Pigment Orange 64 were mixed. The main chemical composition of Pigment Orange 64 is C. 12 H 10 N6O4.

[0140] In Example 7, 90 parts of sol and 10 parts of Pigment Yellow 191 were mixed. The main chemical composition of Pigment Yellow 191 is C. 17 H 13 CaC l N4O7S2.

[0141] Examples 8-9

[0142] The composite material and heat exchanger were prepared in the same manner as in Example 1, except for the ratio of sol and red pigment, and the curing time of the composite material.

[0143] In Example 8, the composite material contains 90 parts of sol and 10 parts of pigment red 254; the composite material is sprayed onto the pretreated surface of the heat exchanger and cured at 180°C for 60 minutes to obtain a heat exchanger with a colored coating.

[0144] In Example 9, the composite material contains 99 parts sol and 1 part pigment red 254; the composite material is sprayed onto the pretreated surface of the heat exchanger and cured at 220°C for 10 minutes to obtain a heat exchanger with a colored coating.

[0145] Everything else is the same as in Example 1.

[0146] Examples 10-11

[0147] The composite material and heat exchanger were prepared in the same manner as in Example 1, except that: (a1) an alcohol-soluble sol was prepared.

[0148] In Example 10, the difference from Example 1 is that in step (a1), 56 parts by mass of anhydrous ethanol and 1.5 parts by mass of sodium dodecyl sulfate are mixed and ultrasonically dispersed for 15 min. Then, 32 parts by mass of KH-560 and 8 parts by mass of tetraethyl orthosilicate are added, and the mixture is mechanically stirred for 40 min at 55°C and 300 rpm in a water bath. Then, 7 parts by mass of water and 2 parts by mass of formic acid are added dropwise to the system, and the addition is completed within 15 min. The mixture is then reacted in a water bath at 55°C for about 26 h to obtain an alcohol-soluble silica sol. The rest is the same as in Example 1.

[0149] In Example 11, the difference from Example 1 is that in step (a1), 50 parts by mass of anhydrous ethanol and 0.5 parts by mass of sodium dodecyl sulfate are mixed and ultrasonically dispersed for 5 min. Then, 30 parts by mass of KH-560 and 6 parts by mass of tetraethyl orthosilicate are added, and the mixture is mechanically stirred for 20 min at a stirring speed of 200 rpm in a water bath at 45°C. Then, 5 parts by mass of water and 0.5 parts by mass of formic acid are added dropwise to the system, and the addition is completed within 5 min. The mixture is then reacted in a water bath at 45°C for about 22 h to obtain an alcohol-soluble silica sol. The rest is the same as in Example 1.

[0150] Examples 12-13

[0151] The composite material and heat exchanger were prepared in the same manner as in Example 1, except that: (a2) the ratio of alcohol-soluble sol to water-soluble sol was adjusted in the mixing of alcohol-soluble sol and water-soluble sol.

[0152] In Example 12, the difference from Example 1 is that in step (a2), 36 parts of the alcohol-soluble silica sol, 57 parts of the water-soluble silica sol, and 6 parts of the water-soluble titanium dioxide sol prepared in step (a1) are mixed evenly, and the pH of the system is adjusted to about 3.0 using 5 parts of formic acid as a pH adjuster. The mixture is stirred and reacted for about 5 hours in a water bath at about 55°C to obtain the sol. The rest is the same as in Example 1.

[0153] In Example 13, the difference from Example 10 is that in step (a2), 34 parts of the alcohol-soluble silica sol, 55 parts of the water-soluble silica sol, and 4 parts of the water-soluble titanium dioxide sol prepared in step (a1) are mixed evenly, and the pH of the system is adjusted to about 3.0 using 3 parts of formic acid as a pH adjuster. The mixture is stirred and reacted for about 5 hours in a water bath at about 45°C to obtain the sol. The rest is the same as in Example 1.

[0154] Comparative Example 1

[0155] The difference between Comparative Example 1 and Example 1 is that the heat exchanger tubes and / or fins of Comparative Example 1 have been sandblasted to 150 mesh, then washed with anhydrous ethanol, and dried. Furthermore, the heat exchanger surface in Comparative Example 1 does not have a colored coating formed by the composite material.

[0156] Performance testing

[0157] 1. Adhesion test

[0158] The test samples of Examples 1-13 were subjected to a cross-cut test. The cross-cut test involves cutting and penetrating the coating on the substrate in a grid pattern, and classifying the completed grid pattern into six levels to assess the coating's resistance to separation from the substrate.

[0159] ISO rating of the cross-cutting knife test:

[0160] Grade 0: The edges of the cut are completely smooth, and there is no peeling at the edges of the grid.

[0161] Level 1: Small pieces peel off at the intersection of the cuts, and the actual damage within the gridded area does not exceed 5%;

[0162] Grade 2: There is peeling at the edges and / or intersections of the incision, and the peeled area is 5% to 15% of the gridded area;

[0163] Level 3: Partial or large-scale peeling along the cut edge, and / or partial peeling of some grids, with the peeled area being 15% to 35% of the grid area;

[0164] Level 4: Large areas of the cut edge are peeled off / or some square grids are partially or completely peeled off, with the peeled area being 35% to 65% of the grid area;

[0165] Level 5: Exceeds the previous level.

[0166] The ISO rating of the cross-cut adhesion test results for the test samples in Examples 1-13 was all 0. This demonstrates that the colored coating of this application has strong adhesion to the substrate.

[0167] 2. Coating thickness test

[0168] The coating thickness of Examples 1 to 7 was tested using a high-precision coating thickness gauge, and the results are shown in Table 1.

[0169] Table 1

[0170] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Thickness (μm) 11.9 14.0 15.7 14.3 15.0 8.1 10.1

[0171] As shown in Table 1, the thickness of the colored coating formed on the heat exchanger surface is in the range of 8 to 16 μm. The thinner colored coating has less impact on the heat exchange efficiency of the heat exchanger.

[0172] This application also tests the film thickness uniformity of the colored coating on the surface of the heat exchanger prepared in Examples 1 and 5. The specific test method is as follows: 10 test points are randomly selected on the surface of the heat exchanger with the colored coating, and the film thickness is tested respectively.

[0173] The thicknesses of the red coating measured at test points on the heat exchanger surface in Example 1 were: 11.2 μm, 10.2 μm, 10.1 μm, 11.8 μm, 10.4 μm, 9.6 μm, 10.5 μm, 9.4 μm, 9.7 μm, 9.5 μm, and 10.2 μm, respectively. The average film thickness was 10.2 μm, and the standard deviation was 0.736 μm.

[0174] The thicknesses of the gold coating measured at test points on the heat exchanger surface in Example 5 were 11.8 μm, 12.0 μm, 11.3 μm, 11.1 μm, 12.8 μm, 12.1 μm, 12.8 μm, 11.2 μm, 10.3 μm, 12.6 μm, and 11.8 μm, respectively. The average film thickness was 11.8 μm, and the standard deviation was 0.782 μm.

[0175] As can be seen from the above test results, since the color additives and fillers in the composite material of this application are evenly distributed in the coating, the thickness of the colored coating on the heat exchanger surface has good consistency, and the adhesion is strong and has good consistency.

[0176] 3. Hydrophilicity test (contact angle test)

[0177] 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.

[0178] During testing, turn on the contact angle measuring instrument and the connected computer, and open the testing software.

[0179] 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.

[0180] 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.

[0181] The contact angle test results show that the initial contact angles of the samples from Examples 1 to 13 are all smaller than the initial contact angle of 39.114° of the sample from Comparative Example 1. This indicates that the hydrophilic particles contained in the coating of this application, such as silica and titanium dioxide, increase the hydrophilicity of the substrate surface, which is beneficial for condensate drainage and makes it less likely for a humid water environment to form on the sample surface.

[0182] In the description of this application, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. The directional terms such as "upper," "lower," "inner," and "outer" described in the embodiments of this application are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of this application.

[0183] 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 a channel for fluid flow, characterized in that: At least a portion of the surface of the heat exchanger is covered with a colored coating, the colored coating comprising a color additive selected from at least one of organic and inorganic color additives; The heat exchanger includes a manifold, fins, and a plurality of heat exchange tubes, wherein the heat exchange tubes are fixed to the manifold, and the inner cavity of the heat exchange tubes communicates with the inner cavity of the manifold; a colored coating is applied to at least a portion of the surface of at least one of the manifold, the fins, and the heat exchange tubes, and the colored coating applied to at least a portion of the surface of at least one of the manifold, the fins, and the heat exchange tubes has an average thickness; The thickness of at least a portion of the colored coating applied to at least a portion of the surface of the fin is less than the average thickness; And / or, the thickness of at least a portion of the colored coating applied to at least a portion of the surface of the heat exchange tube is less than the average thickness.

2. The heat exchanger according to claim 1, characterized in that: The color additive is selected from C. 18 H 10 C l2 N2O2, C 32 C l16 CuN8, C 32 H 16 CuN8, C 35 H 23 C l2 N3O2, C 12 H 10 N6O4, C 17 H 13 CaC l N4O7S2, at least one of the following: mica, titanium dioxide, tin dioxide, and ferric oxide.

3. The heat exchanger according to claim 1, characterized in that: The colored coating comprises silicon dioxide and titanium dioxide, wherein at least a portion of the silicon dioxide surface is bonded with functional groups -(CH2)3-O-CH2-CH-OCH2 and hydroxyl groups -OH.

4. The heat exchanger according to claim 1, characterized in that: The thickness of the colored coating is 8~16 μm.

5. The heat exchanger according to claim 1, characterized in that: The colored coating includes a first colored coating and a second colored coating, which are respectively applied to different positions on the surface of the heat exchanger. The color of the first colored coating is different from the color of the second colored coating.

6. The heat exchanger according to any one of claims 1-5, characterized in that: The fins are located between two adjacent heat exchange tubes.

7. The heat exchanger according to claim 1, characterized in that: The heat exchanger includes an external channel for external fluid flow. The heat exchange tube has an inner surface for forming the external channel. The inner surface has an edge region and a middle region. The external channel has a fluid inlet and a fluid outlet. The edge region includes a first edge region relative to the middle region and closer to the fluid inlet, and a second edge region relative to the middle region and closer to the fluid outlet. The middle region is located between the first edge region and the second edge region. The thickness of the colored coating applied to the first edge region and the second edge region is greater than or equal to the thickness of the colored coating applied to the middle region. And / or, The fin has an inner surface for forming the external channel, the inner surface having an outer edge region and a central region, the external channel having a fluid inlet and a fluid outlet, the outer edge region including a first outer edge region relative to the central region and closer to the fluid inlet and a second outer edge region relative to the central region and closer to the fluid outlet, the central region being located between the first outer edge region and the second outer edge region, and the thickness of the colored coating applied to the first outer edge region and the second outer edge region being greater than or equal to the thickness of the colored coating applied to the central region.

8. A thermal management system, characterized in that: The thermal management system includes a compressor, a first heat exchanger, a throttling device, and a second heat exchanger. The surface color of the first heat exchanger is different from the surface color of the second heat exchanger. When refrigerant flows through the thermal management system, the refrigerant flows into the first heat exchanger via the compressor, and after heat exchange occurs in the first heat exchanger, it flows into the throttling device. Then, the refrigerant flows into the second heat exchanger, and after heat exchange occurs in the second heat exchanger, it flows back into the compressor. One of the first heat exchanger and the second heat exchanger includes a manifold, fins, and a plurality of heat exchange tubes, wherein the heat exchange tubes are fixed to the manifold and the inner cavity of the heat exchange tubes communicates with the inner cavity of the manifold; the fins are located between two adjacent heat exchange tubes; a colored coating is applied to at least a portion of the surface of at least one of the manifold, the fins, and the heat exchange tubes, wherein the colored coating applied to at least a portion of the surface of at least one of the manifold, the fins, and the heat exchange tubes has an average thickness; The thickness of at least a portion of the colored coating applied to at least a portion of the surface of the fin is less than the average thickness; And / or, the thickness of at least a portion of the colored coating applied to at least a portion of the surface of the heat exchange tube is less than the average thickness.

9. The thermal management system according to claim 8, characterized in that: At least a portion of the surface of one of the first and second heat exchangers is covered with a colored coating, the color of which is different from the color of the substrate of both the first and second heat exchangers; or... At least a portion of the surface of the first heat exchanger is covered with a third colored coating, and at least a portion of the surface of the second heat exchanger is covered with a fourth colored coating, wherein the color of the third colored coating is different from the color of the fourth colored coating.

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