Heat exchanger and method of processing a heat exchanger

Abstract

The application provides a heat exchanger, which comprises a base body and a composite layer, the composite layer is arranged on at least part of the surface of the base body, and the composite layer comprises a concave-convex oxide layer, a glue layer and a hygroscopic agent layer. The heat exchanger effectively solves the problems of insufficient bonding strength and insufficient structural stability of the hygroscopic agent, the thickness of the hygroscopic agent layer is 0.1-1.5 mm, the stability is ensured, the balance of the mass transfer and heat transfer efficiency is achieved, and the efficiency is significantly improved.

Description

Technical Field

[0001] This application relates to the fields of heat exchange and materials technology, and more specifically, to a heat exchanger and a method for processing the heat exchanger. Background Technology

[0002] Regenerable desiccant-coated heat exchangers are created by coating the fins and other components of traditional metal heat exchangers with a regenerable desiccant coating. By utilizing the regenerable desiccant, water in the air can be physically adsorbed and desorbed under certain heating conditions, thus regenerating the desiccant. Heat exchangers can be broadly classified into three categories based on the principle and method of heat exchange between cold and hot fluids: indirect-contact, mixed-contact, and regenerative. The most widely used is the indirect-contact heat exchanger, where a solid partition separates the heat exchange fluid from the indirect-contact heat transfer. For example, in a metal tube-fin heat exchanger, metal fins are installed on a metal tube, and a regenerable desiccant coating is applied to the surface of the fins. Moisture in the air between the fins is adsorbed / desorbed by the coating. Simultaneously, the regenerable desiccant coating exchanges heat with the cold / hot fluid flowing inside the metal tube through an indirect-contact process. The cold fluid carries away the heat of adsorption from the regenerable desiccant coating, promoting adsorption, while the hot fluid heats the coating, promoting desorption (regeneration). Currently, these renewable desiccant-coated heat exchangers are mainly used in dehumidification, air conditioning, and air-to-water extraction, demonstrating significant application value in effectively utilizing latent heat, air-to-water resources, low-grade waste heat, and solar energy. Compared to traditional renewable desiccant granule-filled heat exchangers, renewable desiccant-coated heat exchangers exhibit outstanding advantages in adsorption / adsorption performance, cycle efficiency, and energy consumption costs due to their significantly improved heat and mass transfer efficiency.

[0003] In existing renewable desiccant coating heat exchanger technologies, improving the structural stability and dissolution stability of the coating is a significant challenge, which is crucial for the coating heat exchanger to adapt to operating conditions.

[0004] In addition, increasing the unit volume / area coating amount of regenerable desiccant on heat exchangers is an important indicator for achieving miniaturized and lightweight product applications. High coating amount not only further enhances structural stability, but also avoids damage to the coating caused by fin gap closure and post-processing thermal and mechanical stress.

[0005] Existing preparation methods are often time-consuming and energy-intensive, resulting in high costs for industrial application. Therefore, this invention aims to optimize high-cost aspects of reported technologies, such as the high cost of coating heat exchangers before assembly in spray coating processes. Summary of the Invention

[0006] To address the problems in the aforementioned technologies, this invention provides a heat exchanger and a method for processing the heat exchanger, aiming to improve the structural stability of the coating and effectively enhance mass and heat transfer efficiency.

[0007] A first aspect of the present invention provides a heat exchanger comprising: a substrate and a composite layer, the composite layer being disposed on at least a portion of the surface of the substrate, the composite layer comprising an uneven oxide layer, an adhesive layer, and a desiccant layer, the desiccant layer having a thickness of 0.1-1.5 mm.

[0008] Preferably, the desiccant layer comprises polyvinyl alcohol and its derivatives, as well as an adsorbent. The adsorbent includes, but is not limited to, one or more combinations of silica gel, molecular sieves, alumina, activated carbon, and metal-organic framework compounds.

[0009] Preferably, the content of polyvinyl alcohol and its derivatives is 5wt%-20wt%.

[0010] Preferably, the adhesive layer comprises polyvinyl alcohol and its derivatives, and the thickness of the adhesive layer is 1-20 micrometers.

[0011] Preferably, the degree of alcoholysis of polyvinyl alcohol and its derivatives is 90-100%, the degree of polymerization is 2000-3000, and the molecular weight is 100000-200000.

[0012] Preferably, the adsorbent weight per unit area of ​​the desiccant layer is 300-600 grams per square meter.

[0013] Preferably, the thickness of the uneven oxide layer is 0.01-0.1 micrometers, and the roughness is 1-10 micrometers.

[0014] A second aspect of the present invention provides a method for processing a heat exchanger, wherein at least a portion of the surface of a heat exchanger substrate is processed, the method comprising: performing surface etching and rapid air drying to form an uneven oxide layer; impregnating and curing an adhesive slurry to form an adhesive layer; and impregnating and curing a desiccant slurry to form a desiccant layer having a thickness of 0.1-1.5 mm.

[0015] Preferably, the desiccant slurry comprises polyvinyl alcohol and its derivatives, as well as an adsorbent. The adsorbent includes one or more combinations of silica gel, silicon dioxide, molecular sieves, alumina, activated carbon, and metal-organic framework compounds.

[0016] Preferably, after dipping in the desiccant slurry, the dipped surface is blown with hot air until the desiccant slurry on the dipped surface is semi-cured, and then a new desiccant slurry is dipped in again.

[0017] Preferably, in the curing step, the product is dried at a low temperature of 50-60 degrees Celsius for 0.5-1.5 hours, and then heated to a high temperature of 80-100 degrees Celsius for 2-5 hours.

[0018] The heat exchanger proposed in this invention effectively solves the problems of insufficient adhesive strength and structural stability of the desiccant. The thickness of the desiccant layer is 0.1-1.5 mm, which ensures stability while achieving a balance between mass transfer and heat transfer efficiency, resulting in a significant improvement in efficiency. Attached Figure Description

[0019] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0020] Figure 1 This is a schematic diagram of the structure of a heat exchanger according to one embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the structure of the substrate surface and the composite layer in one embodiment of the present invention;

[0022] Figure 3 This is a schematic flowchart of a heat exchanger processing method according to an embodiment of the present invention. Detailed Implementation

[0023] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted.

[0024] Figure 1 This is a schematic diagram of the heat exchanger according to one embodiment of the present invention. Figure 1 As shown, the tube-fin heat exchanger includes multiple tubes 501 and multiple fins 502 mounted on them. During operation, a heat exchange medium flows within the tubes 501 to achieve heat transfer.

[0025] Heat exchanger substrates are typically made of metal base materials, including various metals and metal alloys, such as aluminum, copper, titanium, nickel, zirconium, iron, aluminum alloys, copper alloys, titanium alloys, nickel alloys, zirconium alloys, stainless steel, and combinations thereof.

[0026] It is important to note that Figure 1 The heat exchanger described herein is a partitioned-wall type, but this invention is not limited to partitioned-wall heat exchangers; it is also applicable to other types of heat exchangers such as mixing and regenerative heat exchangers. The heat exchanger structure described in this application is also not limited to... Figure 1 The tube-fin heat exchanger shown can be, for example, a heat exchanger structure including manifolds, heat exchange tubes, and fins, or other heat exchanger structures. The more complex the heat exchanger structure and the higher the density, the more obvious the advantages of the present invention become.

[0027] The heat exchanger includes a substrate and a composite layer. The composite layer is applied to at least a portion of the surface 1 of the substrate, for example, it may be applied to the surface of the tube 501 or the fins 502, and more preferably it may be applied to the entire surface of the heat exchanger substrate.

[0028] The heat exchanger provided in this application is a regenerable desiccant coated heat exchanger, that is, the composite layer includes a regenerable desiccant. The regenerable desiccant physically adsorbs water in the air and desorbs the water under certain heating conditions, thereby realizing the regeneration of the regenerable desiccant.

[0029] Specifically, the regenerable desiccant adsorbs / desorbs water from the air within the space of the heat exchanger. Simultaneously, the composite layer undergoes indirect heat exchange with the cold / hot fluid (heat exchange medium) flowing inside the tube. The cold fluid carries away the adsorption heat of the composite layer, promoting the adsorption of the regenerable desiccant, while the hot fluid heats the composite layer, promoting the desorption of water from the regenerable desiccant, thus achieving the regeneration of the desiccant. In this way, the heat exchanger provided by this invention can achieve a dual process of mass transfer (water) and heat transfer.

[0030] Figure 2 This is a schematic diagram of the structure of the substrate surface and the composite layer in one embodiment of the present invention. Figure 2 As shown, the composite layer is applied to at least a portion of the surface 1 of the substrate, and the composite layer includes an uneven oxide layer 2, an adhesive layer 3, and a desiccant layer 4.

[0031] The uneven oxide layer 2 adheres closely to the surface 1 of the substrate, acting as an isolation layer for the metal on surface 1 and preventing the exposed metal from reacting with water and forming bubble defects during the dip coating process. The uneven oxide layer increases surface roughness, thereby increasing the adhesion sites and bonding strength between the substrate and the composite layer.

[0032] Preferably, the thickness of the uneven oxide layer 2 is 0.01-0.1 micrometers and the roughness is 1-10 micrometers. The inventors of this application have creatively discovered that the thickness of the uneven oxide layer 2 has a significant impact on heat transfer and adhesion. The ultrathin oxide layer has lower interfacial thermal resistance and better adhesion.

[0033] Adhesive layer 3 adheres to the uneven oxide layer 2, enhancing adhesion. Applying adhesive layer 3 between surface 1 and the desiccant layer 4 increases the bonding strength between the coating and the substrate, effectively preventing the composite layer from detaching. Preferably, the thickness of adhesive layer 3 is 1-20 micrometers; an ultra-thin adhesive layer provides better heat transfer efficiency.

[0034] The desiccant layer 4 is an adsorption / desorption functional layer with a thickness of 0.1-1.5 mm. The thickness of the desiccant layer has a significant impact on structural stability and mass and heat transfer capabilities. If the desiccant layer 4 is too thick, it will lead to structural instability, easy cracking and bubbling, and reduced heat transfer efficiency. If the desiccant layer 4 is too thin, it cannot achieve a high adsorption capacity, resulting in low adsorption efficiency.

[0035] The desiccant layer 4 uses hydrophilic adhesives and adsorbents. Hydrophilic adhesives include polyvinyl alcohol, hydroxypropyl methylcellulose, chitosan, gelatin, and their derivatives. The desiccant is a renewable desiccant material, including but not limited to one or more combinations of silica gel, molecular sieves, alumina, activated carbon, and metal-organic frameworks (MOFs). Molecular sieves refer to renewable desiccant materials with regular and uniform pores in their structure, with pore sizes on the order of molecules, allowing only molecules with diameters smaller than the pore size to enter.

[0036] Preferably, the desiccant layer 4 comprises polyvinyl alcohol and its derivatives, as well as an adsorbent. Polyvinyl alcohol has good hydrophilicity, which can improve the solubility stability of the desiccant layer 4, resulting in better heat exchanger durability. Since hydrophilic binders such as hydroxypropyl methylcellulose, chitosan, and gelatin have low water solubility temperatures and poor stability at the heat exchanger's operating temperature, a desiccant layer formulation including polyvinyl alcohol and its derivatives with specific parameters is preferred, as it can effectively improve the structural stability and solubility stability of the composite layer.

[0037] At this point, the adhesive layer 3 is preferably made of polyvinyl alcohol. In another preferred embodiment, the desiccant layer 4 is composed only of polyvinyl alcohol and its derivatives and an adsorbent. Since polyvinyl alcohol is non-toxic and non-irritating, it can ensure that the heat exchanger composite layer structure is very stable under operating conditions, while the water desorbed from the desiccant layer 4 can be directly reused or drunk.

[0038] In order to achieve better moisture absorption, in a preferred embodiment, the adsorbent weight per unit area of ​​the desiccant layer is 300-600 grams per square meter. When this value is met, the heat exchanger has a very good mass transfer effect.

[0039] The composite layer in this application innovatively comprises a three-layer composite structure, which can effectively improve the structural stability and dissolution stability of the coating, while achieving better mass and heat transfer effects.

[0040] The production of heat exchangers coated with renewable desiccant mostly employs electrostatic spraying, where renewable desiccant is sprayed onto the fin surface using a spray gun before assembly. While this method offers good uniformity and fast curing, it often suffers from poor coating adhesion and powdering, posing significant risks to the functional stability of the heat exchanger. Furthermore, the coating thickness produced by this process is limited, preventing the achievement of high coating coverage per unit volume on the heat exchanger, which is detrimental to miniaturized and lightweight product applications. Moreover, spraying cannot directly coat the surface of tube-fin heat exchangers with slit structures; the straight spray path leads to obstructions, uneven coating, and fin gap blockage. Therefore, the spraying process requires disassembling the fins for spraying before reassembly, increasing process complexity and placing higher demands on the heat exchanger's structural design, both resulting in higher manufacturing costs.

[0041] Dip coating involves directly immersing the heat exchanger in a renewable desiccant slurry. This process is well-suited for coating complex surfaces, and some research has successfully fabricated heat exchangers with renewable desiccant coatings using dip coating. However, the developed methods still have significant limitations. These limitations primarily stem from the fact that the coating quality is closely related to the slurry viscosity, the amount coated in a single pass is limited, and existing dip coating processes generally require multiple cycles of dipping and curing. This results in numerous steps, long processing times, high energy consumption, and high costs. Furthermore, repeated high-temperature curing exposes the coating to repeated thermal stress, leading to more structural defects.

[0042] Figure 3 This is a schematic flowchart of a heat exchanger processing method according to an embodiment of the present invention. Figure 3 As shown, the heat exchanger is treated using a dip-coating process, which involves treating the entire heat exchanger substrate that needs to be covered with the composite layer. This overall coating process avoids mechanical stress during the assembly of the coated fins, thereby increasing structural stability. It is suitable for miniaturized and lightweight applications and can also effectively reduce manufacturing costs.

[0043] The specific steps for treating heat exchangers include:

[0044] S1. Ultrasonic cleaning: The heat exchanger is immersed in detergent and ultrasonically cleaned to remove oil and other impurities from the surface of the heat exchanger.

[0045] S2, Etching and Drying: The surface of the heat exchanger is etched and then quickly dried to form an uneven oxide layer 2.

[0046] Specifically, the heat exchanger surface 1 is immersed in an acidic / alkaline solution for etching, followed by rinsing with water to remove the etching solution. The acidic solution includes, but is not limited to, aqueous solutions of one or more mixtures of hydrochloric acid, sulfuric acid, phosphoric acid, and nitric acid; the alkaline solution includes, but is not limited to, aqueous solutions of one or more mixtures of sodium hydroxide, potassium hydroxide, and ammonia. In other embodiments, the heat exchanger surface can also be treated with a sandblasting process, where high-hardness sand is blasted onto the metal substrate surface, creating surface irregularities through mechanical friction and impact, followed by cleaning to obtain the desired surface roughness.

[0047] The heat exchanger, after etching and water washing, is rapidly dried to obtain an ultrathin oxide layer on the etched metal substrate surface. The uneven oxide layer 2, through etching, increases surface roughness, thereby increasing the adhesion sites and bonding strength between the substrate and the composite layer. Simultaneously, the uneven oxide layer 2 prevents the exposed metal from reacting with water and forming bubble defects during the dip-coating process. Rapid air drying allows for control of the thickness of the uneven oxide layer 2, resulting in an ultrathin oxide layer with low interfacial thermal resistance.

[0048] S3. Dip-coating and curing the adhesive layer: Dip the adhesive slurry and cure it to form adhesive layer 3. Applying the adhesive layer between the metal substrate and the hygroscopic coating increases the adhesion strength between the substrate and the composite layer. Prepare a completely dissolved aqueous solution of polyvinyl alcohol and dip the air-dried heat exchanger into it.

[0049] During curing, gradient curing is preferred: first, dry at a low temperature of 50-60 degrees Celsius for 0.5-1.5 hours, then raise the temperature to 80-100 degrees Celsius and dry for 2-5 hours. Gradient curing slows down the curing temperature rise rate and reduces thermal stress.

[0050] Before the coating cures, airflow pressure parallel to the fins is used to improve the uniformity of the coating and remove gap blockages in structural components such as fins.

[0051] S4. Impregnation and curing of desiccant layer: Impregnate with desiccant slurry and cure to form a desiccant layer with a thickness of 0.1-1.5 mm.

[0052] In terms of operation, first prepare the desiccant slurry according to its composition. In a completely dissolved polyvinyl alcohol aqueous solution, add the renewable desiccant powder according to the preset mass percentage under mechanical stirring. Stir and mix at 80-95 degrees Celsius for 2-4 hours. After ultrasonic treatment to fully fuse, stir and cool down to 30-40 degrees Celsius, then dip the entire heat exchanger into the slurry.

[0053] In a preferred embodiment, the hygroscopic slurry is composed of polyvinyl alcohol and an adsorbent, which includes one or more of silica gel, molecular sieves, alumina, activated carbon, and metal-organic framework compounds.

[0054] To achieve the required thickness of the hygroscopic agent, multiple dip coatings are often necessary. However, the current dip coating process has a limited coating amount per coat, requiring repeated dip coatings and high-temperature curing, which is time-consuming, energy-intensive, and costly. Furthermore, repeated high-temperature curing can easily cause thermal stress defects.

[0055] This invention innovatively employs a hot air semi-curing process. After the slurry is applied, hot air is blown onto the surface until the slurry's fluidity decreases, resulting in a semi-cured state. When the heat exchanger includes a finned structure, a slurry film without blocking channels between the fins is also required before a new slurry is applied. Preferably, hot air at 50-70 degrees Celsius is blown along the parallel direction of the heat exchanger fins.

[0056] The hot air semi-curing process can reduce the fluidity of the slurry on the substrate surface, and the new slurry can be adhered to the re-dip coating. This significantly increases the amount of desiccant applied in a single coat before high-temperature curing. At the same time, the semi-cured, semi-fluid state and multi-layer coating can reduce interlayer defects. The hot air treatment process can also clear the gaps between the fins, avoid blockage, and improve the uniformity of the coating.

[0057] Compared to re-dip coating after full curing, hot air semi-curing increases the coating amount per curing cycle, reduces the time and number of high-temperature curing cycles, shortens the time of major energy-consuming steps, and significantly reduces energy costs. The reduced number of high-temperature curing cycles also reduces thermal stress defects.

[0058] After the slurry is applied, it is cured at high temperature, preferably using gradient curing and applying airflow pressure parallel to the fins. The process of applying and curing the slurry can be repeated multiple times as needed.

[0059] The present invention will be 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 some examples, and any other suitable specific examples are within the scope of this application.

[0060] Examples 1-4

[0061] According to the heat exchanger processing method described above, steps S1 to S4 are performed to form a composite layer. Examples 1-4 correspond to layer structures with different thickness parameters, Comparative Example 1 does not include an uneven oxide layer, and Comparative Example 2 does not have a binder layer. The components of each layer in Examples 1-4 and Comparative Examples 1 and 2 are the same.

[0062] The above-described Examples 1-4 and Comparative Examples 1-2 were tested. The adhesion test in this application primarily assesses structural stability, including observing whether the composite layer itself forms a complete plane, whether there are bulges or cracks, and taking samples for scratching, bending, and airflow impact tests to observe for any peeling. If a complete plane cannot be formed or peeling occurs, the test fails. The heat transfer test includes a temperature difference test on the periodic average heat transfer effect of the composite layer (a smaller temperature difference indicates better heat transfer performance).

[0063]

[0064]

[0065] The comparison of Comparative Examples 1 and 2 and Examples 1-4 shows that the three-layer structure has better structural stability. Examples 1, 2, and 3 show that the thickness of the uneven oxide layer or the adhesive layer has a significant impact on heat transfer efficiency, and an excessively thick uneven oxide layer can even have a negative impact on adhesion.

[0066] Examples 1 and 4 show that the thickness of the desiccant layer also has a significant impact on mass and heat transfer efficiency. When the desiccant layer is too thick, the heat transfer efficiency decreases. In practice, it has been found that an excessively thick desiccant layer affects structural stability, and the heat transfer efficiency cannot meet the requirements. An excessively thick desiccant layer is also detrimental to miniaturized and lightweight product applications. According to the structure of the present invention, when the desiccant layer thickness is less than 1.5 mm, it exhibits structural stability under normal operating conditions and can meet the heat transfer efficiency requirements.

[0067] Examples 5-13

[0068] Studies have shown that the composition and parameters of the desiccant layer have a significant impact on the structural stability, adhesion, mass transfer effect, and solubility stability of the composite layer. Following the heat exchanger treatment method described above, steps S1 to S4 are performed to form the composite layer. Examples 5-13 show adsorbent layers composed of polyvinyl alcohol and adsorbent with different parameter ratios. The contents in the tables are the mass percentages (wt%) of polyvinyl alcohol, and the adsorbent material used is the same.

[0069] Tests were conducted on Examples 5-13. The adsorption test measured the amount of desiccant coated per unit area, used to measure the moisture absorption capacity of the heat exchanger; the greater the amount of desiccant coated per unit area, the greater the moisture absorption capacity. The dissolution test involved immersing the sample in water or a 20% ethanol aqueous solution at 40-60 degrees Celsius for 300 hours to observe its resistance and structural stability. The adhesion test included a desorption test at a desorption temperature of 80 degrees Celsius; if desorption occurred, the test was considered a failure. If the adhesion test failed, it indicated that the product had not achieved the expected good results, and the subsequent two tests were not conducted.

[0070]

[0071]

[0072] A comparison of Examples 10-13 and Examples 5-9 shows that the adsorbent layer composed of polyvinyl alcohol and desiccant with certain parameter configurations exhibits excellent adsorption effect and dissolution stability. The dissolution test conditions in this application are quite stringent, exceeding typical practical operating conditions. Under these conditions, Examples 5, 6, 7, and 9 all demonstrate good performance. Comparing Examples 5, 6, and 7, the thickness of the desiccant layer is directly proportional to the amount of desiccant applied per unit area and the heat exchanger's moisture absorption capacity. If the desiccant coating is too thin, the amount of desiccant applied and the moisture absorption capacity are limited; however, if it is too thick, it will also affect the heat and mass transfer efficiency of the desiccant coating, reducing the moisture absorption capacity. Therefore, the moisture absorption layer thickness range of 0.1-1.5 mm in the structure of this invention is a preferred range based on a comprehensive consideration of moisture absorption capacity and heat and mass transfer efficiency. Examples 12 and 7, 8, and 9 show that excessively high polyvinyl alcohol content will reduce the proportion of desiccant in the coating and increase bubble defects, thus failing the adhesion test (Example 12). Example 8 shows that a low polyvinyl alcohol content affects solubility stability, while Example 13 shows that an excessively low polyvinyl alcohol content reduces the adhesion strength of the coating. Examples 10 and 11 show that the degree of polymerization and degree of alcoholysis of polyvinyl alcohol have a significant impact on stability; a too low degree of polymerization cannot achieve the required adhesion strength of the coating, and a too low degree of alcoholysis cannot withstand the desorption temperature of 80 degrees Celsius.

[0073] Long-term research has shown that using hot-soluble polyvinyl alcohol (PVA) and its derivatives with a degree of polymerization greater than or equal to 2000, a degree of hydrolysis greater than or equal to 90%, and a molecular weight of 100,000-200,000 can help form a composite layer with a smooth surface and uniform thickness. This layer exhibits excellent adhesion and resistance to dissolution, withstanding immersion in water at 40-60 degrees Celsius or a 20% ethanol aqueous solution for over 300 hours, and demonstrating high stability to withstand some extreme conditions in actual working environments. Based on structural stability, PVA with a content of 5wt%-20wt% exhibits good mass transfer efficiency, achieving a balance between mass transfer efficiency and stability. Since the quality of the dip-coated layer is closely related to the viscosity of the slurry, the hygroscopic slurry formulation of this application significantly increases the amount of material coated per coat, alleviating the need for repeated dip-coating and curing in existing dip-coating processes. This reduces the number of long-term, frequent high-temperature curing cycles, minimizing defects caused by thermal stress, avoiding coating structural instability under high coating amounts, and also reducing processing and energy costs.

[0074] The invention proposes a highly stable and efficient regenerable desiccant-coated heat exchanger, comprising a multi-layer composite structure of an uneven oxide layer, an adhesive layer, and a desiccant layer. This effectively solves the problems of insufficient desiccant bonding strength and insufficient structural stability. The desiccant layer thickness is 0.1-1.5 mm, which achieves a balance between mass transfer and heat transfer efficiency while ensuring stability, resulting in a significant improvement in efficiency.

[0075] The formulation and parameters of the hygroscopic slurry enable high single-coat yield, enhance adhesion, and reduce solubility at operating temperatures, thereby simultaneously improving structural stability and solubility stability.

[0076] The method for preparing a regenerable desiccant-coated heat exchanger proposed in this invention improves the overall structural stability of the coating through multi-layer processes and slurry formulation, increasing the amount of desiccant coated on the heat exchanger while enhancing coating uniformity and preventing pore blockage between fins. The dip-coating process enables the entire heat exchanger to be coated with adsorbent without having to withstand the mechanical stress during heat exchanger assembly, and can reduce processing and energy costs.

[0077] The hot air semi-curing treatment after dip coating reduces the frequency of high-temperature curing, shortens the time of the main energy-consuming steps, reduces energy consumption costs, and reduces thermal stress defects.

[0078] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and combinations of the technical features in this application should all be considered within the scope of protection of the present invention.

Claims

1. A heat exchanger, characterized in that, include: The substrate and the composite layer, wherein the composite layer is disposed on at least a portion of the surface of the substrate, the composite layer comprising an uneven oxide layer, an adhesive layer, and a desiccant layer, the thickness of the desiccant layer being 0.1-1.5 mm.

2. The heat exchanger as described in claim 1, characterized in that, The desiccant layer comprises polyvinyl alcohol and its derivatives, as well as an adsorbent.

3. The heat exchanger as described in claim 2, characterized in that, The content of polyvinyl alcohol and its derivatives is 5wt%-20wt%.

4. The heat exchanger as described in claim 1, characterized in that, The adhesive layer comprises polyvinyl alcohol and its derivatives, and the thickness of the adhesive layer is 1-20 micrometers.

5. The heat exchanger according to any one of claims 1 to 4, characterized in that, The polyvinyl alcohol and its derivatives have a degree of alcoholysis of 90-100%, a degree of polymerization of 2000-3000, and a molecular weight of 100000-200000.

6. The heat exchanger as described in claim 1, characterized in that, The adsorbent in the desiccant layer has a unit area weight of 300-600 grams per square meter.

7. The heat exchanger as claimed in claim 1, characterized in that, The thickness of the uneven oxide layer is 0.01-0.1 micrometers, and the roughness is 1-10 micrometers.

8. A method for processing a heat exchanger, comprising processing at least a portion of the surface of a heat exchanger substrate, characterized in that, The method includes: Perform surface etching and rapid air drying to form an uneven oxide layer; Dip the adhesive into the resin and allow it to cure to form an adhesive layer; The desiccant slurry is impregnated and cured to form a desiccant layer with a thickness of 0.1-1.5 mm.

9. The heat exchanger processing method as described in claim 8, characterized in that, The hygroscopic slurry contains polyvinyl alcohol and its derivatives, as well as an adsorbent.

10. The heat exchanger processing method as described in claim 8, characterized in that, After dipping in the desiccant slurry, the dipped surface is blown with hot air until the desiccant slurry on the dipped surface is semi-cured, and then a new desiccant slurry is dipped in again.

11. The heat exchanger processing method as described in claim 8, characterized in that, During the curing process, dry at a low temperature of 50-60 degrees Celsius for 0.5-1.5 hours, and then raise the temperature to 80-100 degrees Celsius for a high temperature of 2-5 hours.

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