CN115900422A

CN115900422A - Heat exchanger and treatment method thereof

Info

Publication number: CN115900422A
Application number: CN202110997970.3A
Authority: CN
Inventors: 黄海; 唐建华; 余书睿; 薛明; 黄宁杰
Original assignee: Hangzhou Sanhua Research Institute Co Ltd
Current assignee: Hangzhou Sanhua Research Institute Co Ltd
Priority date: 2021-08-27
Filing date: 2021-08-27
Publication date: 2023-04-04
Also published as: WO2023024743A1

Abstract

The application provides a heat exchanger and a treatment method thereof, wherein the treatment method of the heat exchanger comprises the following steps: providing a heat exchanger, wherein the heat exchanger comprises a collecting pipe, fins and a plurality of heat exchange pipes which are fixed together, the inner cavity of each heat exchange pipe is communicated with the inner cavity of the collecting pipe, and the fins are fixedly connected between every two adjacent heat exchange pipes; and carrying out sand blasting treatment on the heat exchanger, so that at least part of the outer surface of the metal base material corresponding to at least one of the collecting pipe, the fin and the heat exchange pipe forms a rough surface. The sand blasting treatment is favorable for removing the attached impurities on the outer surface of the metal base material, the danger and the pollution in the process are reduced, and meanwhile, the rough surface formed after the sand blasting treatment is favorable for improving the attachment capacity of the metal base material of the heat exchanger in combination with other coating materials.

Description

Heat exchanger and treatment method thereof

Technical Field

The invention relates to the technical field of heat exchange and material treatment, in particular to a heat exchanger and a treatment method thereof.

Background

The manufacturing and processing process of the heat exchanger in the related technology comprises the steps of fixing a collecting pipe, a heat exchange flat pipe, fins and the like together to form the heat exchanger through a brazing process, covering various functional coatings on the surface of the heat exchanger and the like, wherein a large amount of brazing flux remains on the outer surface of a metal base material corresponding to the heat exchanger after the brazing process. In addition, an oxide layer is formed on the surface of the metal base material of the heat exchanger after the metal base material is placed for a long time, and pollutants such as oil stains and the like are generated on the surface of the metal base material of the heat exchanger. These adhesion impurities subsequently affect the adhesion of the coating.

In some technologies, there is an improvement demand for the above heat exchanger by performing acid washing or alkali washing, that is, removing impurities attached to the outer surface of the metal substrate by means of chemical reaction, and changing the shape of the metal substrate to some extent, but the above method is relatively expensive, and the cleaning process has a certain operation risk, and the waste liquid is relatively environmentally polluting.

Disclosure of Invention

The application provides a heat exchanger and a treatment method thereof, which improve the adhesive capacity of the combination of a metal base material and other coating materials on the basis of effectively removing impurities attached to the surface of the metal base material of the heat exchanger and reducing the operation danger and pollution in the process.

In a first aspect, the present application provides a method of treating a heat exchanger, the method comprising the steps of:

providing a heat exchanger, wherein the heat exchanger comprises a collecting pipe, fins and a plurality of heat exchange pipes which are fixed together, the inner cavities of the heat exchange pipes are communicated with the inner cavity of the collecting pipe, and at least part of the fins are connected between two adjacent heat exchange pipes;

and carrying out sand blasting treatment on the heat exchanger to enable at least part of the outer surface of the metal substrate corresponding to at least one of the collecting pipe, the fin and the heat exchange pipe to form an uneven rough surface.

In this application, pass through sand blasting to the surface of heat exchanger and handle, be favorable to getting rid of the attached impurity of remaining at the metal substrate surface, reduce the danger and the pollution nature of this process, simultaneously, because the surface of metal substrate has formed unevenness's mat surface after sand blasting handles, this mat surface is favorable to improving the metal substrate of heat exchanger and the adhesive force that other coating materials combine.

In a second aspect, the present application provides a heat exchanger, which includes a header, fins, and a plurality of heat exchange tubes fixed together;

the heat exchange tubes are arranged along the length direction of the collecting pipe, and the inner cavities of the heat exchange tubes are communicated with the inner cavity of the collecting pipe; the width of the heat exchange tube is larger than the thickness of the heat exchange tube, and the width direction of the heat exchange tube is not in the same direction with the length direction of the collecting pipe;

at least part of the fin is connected between two adjacent heat exchange tubes;

the outer surface of the metal substrate corresponding to at least one of the collecting pipe, the fins and the heat exchange pipe comprises an uneven rough surface, and the roughness alpha of the rough surface is more than or equal to 0.5 mu m and less than or equal to 10 mu m.

In the present application, the outer surface of the metal substrate corresponding to at least one of the header, the fin and the heat exchange tube includes an uneven rough surface, which is beneficial to improving the adhesion capability of the metal substrate of the heat exchanger to other coating materials.

Drawings

FIG. 1 is a schematic structural diagram of a heat exchanger provided in an embodiment of the present application;

FIG. 2 is a schematic view of an assembly structure of the heat exchange tube and the fins in FIG. 1 of the present application;

FIG. 3 is a schematic structural diagram of the heat exchange tube of FIG. 1 of the present application;

FIG. 4 is a schematic structural view of the fin of FIG. 1 of the present application;

FIG. 5 is a flow chart of a method of treating a heat exchanger according to one embodiment of the present application;

FIG. 6 is a flow chart of a method of treating a heat exchanger according to another embodiment of the present application;

FIG. 7 is a schematic diagram showing the comparison of the effects of the present application after sand blasting the heat exchanger fins 1, 3 and 5 times respectively;

FIG. 8 is a schematic comparison of the effect of the rough surface formed before and after the aluminum plate is sandblasted according to the present application;

FIG. 9 is a graph comparing the results of the salt spray test of some of the examples of the first embodiment of the present application;

FIG. 10 is a graph comparing the results of the salt spray test of some of the second example and some of the comparative examples of the present application;

FIG. 11 is a graph comparing the results of salt spray tests of a portion of the third example and a portion of the comparative example of the present application.

Detailed Description

For better understanding of the technical solutions of the present application, the following detailed descriptions of the embodiments of the present application are provided with reference to the accompanying drawings.

It should be understood that the embodiments described are only a few embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

The present application provides a heat exchanger, in some embodiments a microchannel heat exchanger.

Referring to fig. 1, a heat exchanger 100 includes two headers 11, a plurality of heat exchange tubes 12, and a plurality of fins 13, in the heat exchanger, the plurality of heat exchange tubes 12 are all fixed to the headers 11, the heat exchange tubes 12 are provided with a plurality of channels for refrigerant to flow through, and the plurality of channels of the heat exchange tubes 12 are all communicated with an inner cavity of the headers 11, the fins 13 are located between two adjacent heat exchange tubes 12, the outer surfaces of the metal substrates corresponding to the headers 11, the fins 13, and the heat exchange tubes 12 may be rough surfaces processed by a sand blasting process, which is schematically illustrated as rough surfaces 121 of the metal substrates corresponding to the heat exchange tubes 12 in fig. 1. The collecting main 11 is provided with a fluid inlet 101 and a fluid outlet 102 which are communicated with the inner cavity of the collecting main, so that the fluid can enter the heat exchanger conveniently.

The heat exchanger 100 of the present application may be a microchannel heat exchanger, and specifically, the plurality of heat exchange tubes 12 are arranged along a length direction of the collecting main 11, and the length direction of the collecting main 11 may refer to an X direction in fig. 1.

The heat exchange tube 12 is a tubular structure extending lengthwise, the length direction of the heat exchange tube 12 can be referred to as Y direction in fig. 1, and the width direction of the heat exchange tube 12 can be referred to as D direction in fig. 2. The width of the heat exchange tube 12 is larger than the thickness of the heat exchange tube 12, and the thickness direction of the heat exchange tube 12 substantially coincides with the length direction of the header 11. The width direction of the heat exchange tube 12 is not in the same direction as the longitudinal direction of the header 11. In fig. 1, the width direction (D direction) of the heat exchange tube 12 is substantially perpendicular to the longitudinal direction (X direction) of the header 11.

In some embodiments, the material of the metal substrate corresponding to any one of the header 11, the fin 13 and the heat exchange tube 12 includes at least one of aluminum, copper and stainless steel. For example, the collecting pipe 11, the fins 13 and the heat exchange pipe 12 are all aluminum parts.

In some embodiments, the roughness Ra of the rough surface of the metal base material is 0.5 to 10 μm, and in some embodiments, the roughness Ra of the rough surface of the metal base material is 1 to 3 μm. Specifically, the roughness of the rough surface coated on the metal substrate may be 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, etc., but is not limited to the values listed, and other values not listed in the range of the values are also applicable. The roughness of the surface of the metal base material is controlled, so that the metal base material has good durability when other coating materials are combined subsequently, although the adhesion of the subsequent coating is facilitated under the condition of large roughness, the deformation degree of the metal base material is large when the roughness is too large, for example, more than 10 micrometers, the thickness of the metal base material is relatively high, and otherwise, the metal base material is easily damaged.

For a metal substrate which is not subjected to sand blasting treatment, the roughness error at each position of the metal substrate is relatively large because the residual impurities on the surface of the metal substrate are different and uneven.

In fig. 1, the number of the collecting pipes 11 is 2, and both ends of the heat exchange tube 12 in the length direction are respectively communicated with the inner cavities of the two collecting pipes 11. This type of heat exchanger is also commonly referred to in the industry as a single row heat exchanger, and in some other embodiments the number of headers 11 may be 1 or more than 2. Correspondingly, the number of the heat exchange tubes and the number of the fins are set according to the actual product requirement.

In some embodiments, referring to fig. 2, the fin 13 is a corrugated structure extending in the length direction (Y direction) of the heat exchange tube 12. The fin 13 comprises a plurality of fin units 131 arranged along the length direction of the heat exchange tube 12, the fin units 131 are sequentially connected along the length direction of the heat exchange tube 12, the position where two adjacent fin units 131 are connected forms a wave crest or a wave trough in a corresponding wave structure of the fin 13, and the fin 13 is fixed with the heat exchange tube 12 at the position where two adjacent fin units 131 are connected.

Referring to fig. 3, the heat exchange tube 12 includes two side surfaces 122 and two end surfaces 123, the two side surfaces 122 are substantially disposed in a plane, the two side surfaces 122 are disposed in parallel, and the two side surfaces 122 are respectively disposed on two opposite sides of the heat exchange tube 12 in the thickness direction (X direction). The two end surfaces 123 are located on opposite sides of the heat exchange tube 12 in the width direction (D direction), respectively.

The roughened surfaces include a first roughened surface that is at least a portion of end surface 123 and a second roughened surface that is at least a portion of side surface 122. The roughness of the first rough surface is greater than or equal to that of the second rough surface.

This is advantageous in that, because the heat exchange tube 12 has a flat tubular structure, the two end faces 123 have relatively large radian and relatively narrow size, and when the metal substrate of the subsequent heat exchange tube 12 is combined with the coating material, the end face 123 with large radian has relatively high difficulty in combining with the coating material, and in order to improve the combining ability of the position and the coating, the roughness of the end face 123 part can be set to be larger than that of the side face 122, so that the relatively uneven surface structure of the metal substrate can be better combined with the coating material, so that the combining force with the coating material at the position of the end face 123 is stronger, and accordingly, the combining durability with the coating material at the position can be improved.

Further, the side surface 122 of the heat exchange pipe 12 is relatively flat. The side surface 122 may be equally divided into three regions in the width direction of the heat exchange tube, that is, the side surface 122 includes two first regions 31 and one second region 32, and the second region 32 is located between the two first regions 31 so that the first regions 31 are closer to the end surface 123 than the second regions 32. The roughness of the second rough surface in the first region 31 is equal to or greater than the roughness of the second rough surface in the second region 32. This arrangement is advantageous in that the first region 31, which is positioned relatively outward in the width direction of the heat exchange tube 12, is brought into contact with air relatively early in the heat exchange process, so that the relatively outward portion of the heat exchange tube 12 is more likely to accumulate moisture while the air flows along the width direction of the heat exchange tube 12, and thus the portion is more likely to frost as the windward side. In order to improve the bonding force between the portion and the coating material, the roughness of the second rough surface in the first region 31 may be set to be equal to or greater than the roughness of the second rough surface in the second region 32.

Accordingly, the principle of setting the roughness of each region of the fin 13 is similar, and with respect to the fin 13, referring to fig. 4, the fin unit 131 is equally divided into three regions in the width direction (D direction) of the fin unit 131, that is, the surface of the fin unit 131 includes two third regions 33 and one fourth region 34. The fourth region 34 is located between the two third regions 33. That is, the third region 33 is further outward than the fourth region 34 in the width direction of the fin 13. The roughness of the rough surface of the fin 13 in the third region 33 is equal to or greater than the roughness of the rough surface of the fin 13 in the fourth region 34. Therefore, the roughness of the position of the fin, which is easy to frost, is larger, so that the bonding capacity of the metal base material and the coating material at the position can be improved. The coating material can be a hydrophilic coating material or a hydrophobic coating material which is easy to drain water, and the durability of the coating material is improved, so that the drainage capability of the position is stronger, and the frosting is not easy to affect the heat exchange performance.

As shown in fig. 5, the rough surface formed on the surface of the metal substrate of the heat exchanger is prepared in the following manner in some embodiments of the present application.

And S11, providing a heat exchanger, wherein the heat exchanger comprises a collecting pipe, fins and a heat exchange pipe which are fixed together. Specifically, the collecting pipe, the fins and the heat exchange tube are fixed through a welding process, the heat exchanger after the welding process meets the condition that the inner cavity of the heat exchange tube is communicated with the inner cavity of the collecting pipe, and the fins are fixedly connected between every two adjacent heat exchange tubes.

And S21, performing sand blasting treatment on the heat exchanger. The heat exchanger after sand blasting treatment meets the requirement that at least part of the outer surface of the metal base material corresponding to at least one of the collecting pipe, the fin and the heat exchange pipe is provided with a rough surface.

The collecting pipe, the fins and the heat exchange pipe can be welded by brazing, namely the parts are welded into a whole by brazing, and the brazing process is favorable for realizing the sealing property among the connecting positions of the parts. However, in the brazing process, brazing flux remains on the outer surfaces of the metal base materials of the collecting pipe, the fin and the heat exchange pipe, the brazing flux is limited by material properties, the brazing flux is inorganic, the adhesion is poor, the brazing flux is difficult to combine with a coating material, and the coating is not easy to cover the position where the brazing flux remains in practical application. Furthermore, the metal substrates of the components of the heat exchanger, which are exposed to air for a long time, also form an oxide layer which is likewise disadvantageous for bonding with some types of coating materials. Therefore, the surface of the heat exchanger needs to be treated before coating so as to remove residual brazing flux, oxides, oil stains and other pollutants on the surface, and a certain surface roughness structure is constructed to facilitate the adhesion of the coating.

The surface treatment method for heat exchangers in the related art at present is chemical treatment, i.e. acid washing and alkali washing, and the excess attachments on the surface of the metal substrate are removed by using solvents such as acid, alkali and the like as cleaning agents and chemical reaction of the cleaning agents and metal oxides, soldering flux and the like. However, the method has high cost, complex process, serious environmental pollution and certain danger in the cleaning process. The cleaning of the organic solvent can generate a large amount of waste solvent, the waste solvent is difficult to treat and has great harm to human bodies and the environment, and meanwhile, the flammable and explosive characteristics of the solvent have potential safety hazards. Waste water is generated in the cleaning process, and meanwhile, the cleaning quality is difficult to ensure, and only part of pollutants can be removed. And further, the above manner is difficult to form a regular rough surface on the metal base material, and has no additive effect on the subsequent coating on the heat exchanger.

In the embodiment provided by the application, the heat exchanger is subjected to sand blasting to remove the attachments on the surface of the metal base material, so that the metal base material can be exposed, and the surface of the metal base material is subjected to physical treatment such as sand blasting to form a rough surface on the surface of the metal base material, wherein the rough surface is formed on the basis of physical deformation after the sand blasting. The sand blasting treatment is to mix abrasive in compressed air as a medium and spray the mixture on the surface of a heat exchanger so as to ensure that the surface of the metal matrix obtains certain roughness and cleanliness.

The benefits of the grit blasting include, in the first aspect, the removal of large amounts of flux, oxide layers, oil stains, etc. remaining on the surface of the metal substrate, resulting in a cleaner surface of the metal substrate. And in the second aspect, a better micro rough surface structure is formed on the surface of the metal substrate under the sand blasting and polishing effects of the abrasive, so that the bonding force between the metal substrate and other coating materials is increased, and the leveling and decoration of the coating are facilitated. In the third aspect, the cutting and impact of the blasting strengthens the mechanical properties of the surface of the metal base material, improving the fatigue resistance of the metal base material. In the fourth aspect, the sand blasting can remove irregular structures such as burrs on the surface of the metal base material, and small round corners are formed on the surface of the metal base material, particularly on junctions where parts are connected, so that the surface of the metal base material is more smooth and attractive, and the subsequent treatment is facilitated. After sand blasting treatment, the surface tissue form of the metal base material is changed, and metal grains are more refined and compact. After the sand blasting treatment, more hydroxyl groups are formed on the surface of the metal base material, and in the process of connecting the subsequent functional film layer, the hydroxyl groups of the functional film layer and the hydroxyl groups of the metal base material are subjected to dehydration condensation, so that the functional film layer and the metal base material can be connected through covalent bonds, and the covalent bonds are relatively stable in connection mode, thereby being beneficial to improving the durability of the connection with the functional film layer.

In addition, the treatment mode of the sand blasting process has the characteristics of high efficiency, low cost and suitability for large-surface-area cleaning treatment of metal substrates, and furthermore, the grinding materials adopted by the sand blasting process can be recycled, so that the cost can be further reduced.

This application is to this kind of welding earlier of heat exchanger, and the processing step of back sandblast can effectively get rid of the impurity that adheres to on the heat exchanger surface among the welding process, and forms unevenness's mat surface on the metal substrate surface. And if the surfaces of all parts of the heat exchanger are subjected to sand blasting firstly and then assembled and welded, impurities in the welding process can still be attached to the rough surface, so that the coating of subsequent coating materials is influenced.

In some embodiments of the present application, the step S21 of sand blasting the heat exchanger includes: and mixing the abrasive in compressed air, and spraying the abrasive to the outer surface of the heat exchanger through a spray gun. Further, the abrasive may be corundum, such as brown corundum, white corundum, black corundum, garnet, etc. The abrasive can also be a grit of the silicon carbide type, such as black silicon carbide, green silicon carbide, and the like. Of course, when the abrasive is selected, other kinds of gravels can be selected, and the abrasive can be glass beads, steel shots, steel grit, ceramic grit, resin grit, walnut grit and the like.

In some embodiments, the abrasive has a particle size between 30 mesh and 280 mesh. Specifically, the particle size of the abrasive may be 30 mesh, 50 mesh, 80 mesh, 120 mesh, 150 mesh, 180 mesh, 200 mesh, 220 mesh, 250 mesh, 280 mesh, or the like. The selection of the grain diameter of the abrasive can influence the construction of the rough surface on the surface of the metal base material, when the grain diameter mesh number of the abrasive is relatively large, the rough surface on the surface of the metal base material can be finer, and when the grain diameter mesh number is too large, the roughness of the rough surface can be difficult to ensure. When the particle size is too small, the formation of a rough surface having a certain roughness is relatively slow, and the roughening effect is poor. In some embodiments, the abrasive can have a particle size ranging between 100 mesh to 200 mesh. Therefore, the grain diameter of the grinding material is not too large or too small, and accordingly, a more ideal rough surface structure is more easily obtained.

In some embodiments, the distance between the lance and the corresponding injection location of the outer surface of the heat exchanger is between 20mm and 100mm. Specifically, the distance between the nozzle of the spray gun and the corresponding spraying position of the outer surface of the heat exchanger is simply recorded as the sand blasting distance, the sand blasting distance is too close, pits are easily formed in the surface of the metal base material, the overall rough surface is poor in appearance, the sand blasting distance is too far, the impact force of abrasive materials is poor, and the surface form degree of the metal base material is poor. The blasting distance may be selected in this application to be 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, etc. In some embodiments, the blasting distance may be between 50mm and 100mm.

In some embodiments, the spray angle α of the spray gun satisfies 0 < α ≦ 90. The spray angle of the spray gun is an included angle between the incident direction of the abrasive and the plane where the spray position of the heat exchanger is located, and specifically, the spray angle alpha of the spray gun is 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, 90 degrees and the like. The spray angle α of the spray gun is too small, the interference angle between the metal base material and the abrasive is small, and it is difficult to form a rough surface, and the spray angle α of the spray gun may be an acute angle of 90 ° or less. In some embodiments of the present application, the spray angle α of the spray gun is 45 °.

In some embodiments, the pressure of the compressed air is 0.45MPa to 0.65MPa, specifically, the pressure of the compressed air is 0.45MPa, 0.5MPa, 0.55MPa, 0.6MPa, 0.65MPa. Because the collecting pipes, the fins and the heat exchange tubes of all parts of the heat exchanger are mostly made of aluminum materials in the industry, and correspondingly, the aluminum materials are relatively soft, the pressure of compressed air cannot be too high, otherwise, the parts are easily damaged. Of course, the pressure of the compressed air must not be too low, otherwise it is difficult to form a rough surface. In some embodiments of the present application, the pressure of the compressed air is 0.45MPa.

In the heat exchanger field, the fin material of setting between adjacent heat exchange tube is thinner relatively, in order to avoid the fin to be hit by the abrasive material in the sandblast in-process and hit the destruction, needs the sandblast number of times of control to the fin. In the embodiment of the present application, the number of times of blasting to the fin is 3 or less. Referring to a schematic diagram of comparison of the number of times of blasting the fin position in fig. 7, (c) a pattern in fig. 7 shows the deformation of the fin after 1 blasting, (d) a pattern shows the deformation of the fin after 3 blasting, and (e) a pattern shows the deformation of the fin after 5 blasting. As can be seen from fig. 7, the deformation of the fin is less after the 1 st sand blasting is performed on the fin position, and the fin deformation starts to appear more obviously after the 3 rd sand blasting, and the fin deformation tends to be more serious with the increase of the number of sand blasting times. In pass 5, small areas of fin damage have occurred and the fins are broken through by the gravel. In at least some embodiments of the present application, the number of blasting passes on the fin may be controlled not to exceed 3 times. Specifically, the number of blasting passes for the fin may be 1. The sand blasting times of the collecting pipe and the heat exchange pipe can be more than or equal to 1 time, if the pipe wall of the collecting pipe is thick, sand blasting can be performed on the collecting pipe for 1 to 2 times correspondingly.

Referring to fig. 6, before step S21 of the present application, that is, the step of performing sand blasting on the heat exchanger, the method further includes:

and S20, blocking a fluid inlet and a fluid outlet which are communicated with the tube cavity of the collecting pipe. Typically, the manifold will be provided with a fluid inlet and a fluid outlet. As shown in fig. 1, the fluid inlet 101 and the fluid outlet 102 of the collecting pipe 11 are provided, the fluid inlet 101 and the fluid outlet 102 are communicated with the tube cavity of the collecting pipe 11, and in the specific operation of step S20, a sealing component made of a rubber plug material may be used to seal the fluid inlet and the fluid outlet of the collecting pipe, so that the advantage of preventing abrasive, i.e., gravel, from entering the tube cavity of each component of the heat exchange tube is achieved, and the influence on the flow of fluid is avoided. The heat exchanger which is plugged can be integrally placed into a sand blasting machine for sand blasting operation.

The method further comprises the following steps after the step S21, namely the step of performing sand blasting on the heat exchanger:

and S22, carrying out ultrasonic cleaning treatment on the heat exchanger subjected to sand blasting treatment.

Specifically, the step S22 of performing ultrasonic cleaning treatment on the heat exchanger subjected to sand blasting treatment includes:

and (3) ultrasonically cleaning the heat exchanger subjected to sand blasting treatment by adopting at least one of deionized water, ethanol and absolute ethanol, wherein the ultrasonic cleaning time is 5-10 min, and the ultrasonic frequency of the ultrasonic cleaning is 80-100 Hz. After the heat exchanger after sand blasting treatment is subjected to ultrasonic cleaning treatment, residual gravel on the surface of the heat exchanger can be removed, and the influence on the coating of a subsequent film layer is avoided.

And S23, drying the heat exchanger subjected to the ultrasonic cleaning treatment.

Specifically, step S23 is to perform drying treatment on the heat exchanger subjected to the ultrasonic cleaning treatment, and includes:

and (3) drying or naturally airing the heat exchanger subjected to ultrasonic cleaning, wherein if the heat exchanger is dried in a drying mode, the drying temperature can be above 40 ℃. The heat exchanger after drying treatment is reserved for standby.

In some embodiments, the heat exchanger after the sand blasting treatment may be subjected to ultrasonic cleaning with deionized water, acetone, and ethanol sequentially, each ultrasonic cleaning time is 5min to 10min, and the ultrasonic frequency is 80Hz to 100Hz, specifically, the ultrasonic cleaning time may be 5min, 6min, 7min, 8min, 9min, 10min, and the like, which is not limited to the enumerated values, and other non-enumerated values within the range of the enumerated values are also applicable, and the heat exchanger after the ultrasonic cleaning is placed in an oven for drying.

Further, in order to avoid exposing the heat exchanger after the drying treatment to the air for a long time, the exposed clean metal substrate is easy to form an oxide layer on the surface or be contaminated by other pollutants. In some embodiments of the present application, after the step S22 of drying the heat exchanger after the ultrasonic cleaning process and before the step S31 of obtaining the heat exchanger, the method further includes:

step S30, a functional film layer is arranged on the surface of the rough surface formed by sand blasting.

In some embodiments, a coating layer may be disposed on the surface of the metal substrate corresponding to the collecting main, the heat exchange tube and the fin according to specific needs, for example, a functional film layer is disposed on at least the surface of the metal substrate corresponding to the heat exchange tube and the fin, so as to obtain a better durability effect.

Specifically, the step of providing the functional film layer on the surface of the rough surface after the sand blasting in step S30 may be implemented in various ways according to the kind of the functional film layer.

In a first alternative embodiment, step S30 includes applying a hydrophilic coating or a hydrophobic coating including a silane-based sol to at least a portion of the rough surface, and forming a film layer including a silane-based sol on the rough surface after curing.

The film layer including the silane-based sol includes a silane-based sol material containing a hydrophobic group or a hydrophilic group. The hydrophobic group contained in the functional film layer is, for example, a C10 to C20 hydrocarbon group, a hydrocarbon group containing a group such as an aryl group, an ester group, an ether group, an amine group, or an amide group, or a hydrocarbon group containing a double bond.

In terms of the manufacturing method, taking the hydrophilic film layer prepared from the hydrophilic coating as an example, specifically, the heat exchanger after sand blasting treatment can be soaked in the hydrophilic coating containing the silane sol in a dip-coating manner, the dip-coating frequency is 1 time, the dip-coating duration is controlled to be more than 2min, after the heat exchanger is taken out, the redundant feed liquid can be blown away by using an air gun, and then the heat exchanger with the hydrophilic coating can be obtained by fixing the heat exchanger at the temperature of 200 ℃ for more than 10 min.

In a second alternative embodiment, step S30 includes applying a rare earth conversion coating to at least a portion of the rough surface, and forming a rare earth conversion coating including a rare earth element-containing compound on the rough surface after curing.

And coating a hydrophilic coating or a hydrophobic coating comprising silane sol on at least part of the surface of the rare earth conversion coating, and after curing, correspondingly forming a film layer comprising silane sol on the surface of the rare earth conversion coating.

Specifically, the heat exchanger after sand blasting can be soaked in a rare earth element cerium conversion solution in a dip-coating mode, the duration of the dip-coating is controlled to be more than 10min at the reaction temperature of 50 ℃, and after the heat exchanger is taken out, the heat exchanger can be dried by an air gun to obtain the heat exchanger with the cerium conversion film. Then, the components are soaked in a hydrophobic coating comprising silane sol in a dip-coating mode, the dip-coating frequency is 1 time, the dip-coating duration is controlled to be more than 2min, after the components are taken out, redundant feed liquid can be blown away by using an air gun, and then the components are fixed for more than 20min at the temperature of 120 ℃, so that the heat exchanger with a double-layer coating, namely a top coating of the hydrophobic coating is matched with a bottom coating of a rare earth conversion coating, can be obtained, and has a good hydrophobic anticorrosion function.

In a third alternative embodiment, step S30 includes applying a coating including chromate on at least a portion of the rough surface, and after curing, forming a chromium salt passivation film layer on the rough surface.

Specifically, the heat exchanger after sand blasting treatment can be soaked in a passivation solution coating comprising chromate in a dip-coating mode, the reaction temperature is controlled to be 40 ℃, the dip-coating duration is controlled to be more than 2min, after the heat exchanger is taken out, redundant feed liquid can be blown away by an air gun, and then the heat exchanger with the chromate passivation film layer can be obtained after the heat exchanger is fixed for more than 10min at the temperature of 40 ℃, and the heat exchanger has better corrosion resistance.

In other embodiments of the present application, the functional film layer may also be other types of coatings, such as dust-proof coatings, antimicrobial coatings, and the like. The thickness of the functional film layer is 10 μm to 14 μm, and specifically, it may be 10 μm, 10.3 μm, 10.6 μm, 12 μm, 14 μm, etc., but it is not limited to the recited values, and other values not recited in the range of the values are also applicable. The coating is too thick, which causes resource waste and affects the heat exchange efficiency of the heat exchanger. If the coating is too thin, the coating cannot achieve a more ideal coating effect.

The following describes a plurality of examples provided in the present application, and compares the effects.

In examples 1 to 8, for the convenience of performance testing, an aluminum plate was used as a test sample, that is, an aluminum plate was subjected to sand blasting, and a rare earth conversion coating and a hydrophobic coating were applied to the sand-blasted aluminum plate. The aluminum plate used for the test sample piece is basically the same as the material of the conventional aluminum heat exchanger in the field.

Example 1

(1) And placing the test sample piece into a sand blasting machine for sand blasting treatment, setting the abrasive to be white corundum with the grain diameter of 120 meshes, setting the distance between a spray gun and the position to be sprayed of the heat exchanger to be 50mm, setting the spray angle of the spray gun to be 45 degrees, setting the pressure of compressed air in the spray gun to be 0.45MPa, and setting the sand blasting times to be 1 time.

(2) Taking out the sample piece after sand blasting, spraying the surface of the sample piece with absolute ethyl alcohol, and then drying at 40 ℃ for later use.

(3) And (3) coating the rare earth conversion solution containing cerium on the surface of the sample piece in a dip coating mode on the basis of the sample piece in the step (2), controlling the dip coating time to be about 10min at the reaction temperature of 50 ℃, taking out an air gun and drying the air gun to obtain the sample piece with the cerium conversion film.

(4) And (3) on the basis of the sample piece obtained in the step (5), coating the hydrophobic coating comprising the silane sol on the surface of the cerium conversion film in a dip-coating mode, wherein the dip-coating frequency is 1, the dip-coating duration is controlled to be about 2min, taking out the sample piece, blowing off redundant feed liquid by using an air gun, and fixing the sample piece at the temperature of 120 ℃ for more than 20min to obtain the sample piece with the rare earth conversion coating and the hydrophobic coating.

Example 2

The difference from example 1 is that the spray angle of the spray gun was adjusted to 90 ° in step (1).

Example 3

The difference from example 1 is that the distance between the spray gun and the position to be sprayed of the sample is adjusted to 100mm in step (1).

Example 4

The difference from example 1 is that the distance between the spray gun and the position to be sprayed of the sample piece was adjusted to 100mm and the spray angle of the spray gun was adjusted to 90 ° in step (1).

Example 5

The difference from example 1 is that the abrasive is adjusted to white corundum of 150 mesh particle size in step (1).

Example 6

The difference from example 1 is that the abrasive is adjusted to 150 mesh size white corundum in step (1) and the distance between the spray gun and the position to be sprayed of the sample is adjusted to 100mm.

Example 7

The difference from example 1 is that the abrasive in step (1) was adjusted to white corundum of 200 mesh particle size.

Example 8

The difference from example 1 is that the abrasive is adjusted to 200 mesh size white corundum in step (1) and the distance between the spray gun and the position to be sprayed of the sample is adjusted to 100mm.

In example 9, for the convenience of performance test, an aluminum plate was used as a test sample, that is, an aluminum plate was subjected to sand blasting, and a hydrophilic coating was applied to the sand-blasted aluminum plate. The aluminum plate used for the test sample piece is basically the same as the material of the conventional aluminum heat exchanger in the field.

Example 9

The difference from example 1 is that the coating material of example 9 is in particular a hydrophilic coating of the sol-gel type comprising a silane system, in particular:

(1) And providing the test sample piece after sand blasting treatment.

(2) And (2) coating the hydrophilic sol coating of a silane system on the surface of the test sample piece in the step (1) in a dip-coating mode, wherein the dip-coating frequency is 1 time, the dip-coating duration is controlled to be 2min, after the hydrophilic sol coating is taken out, blowing off redundant feed liquid by using an air gun, and then fixing at the temperature of 200 ℃ for more than 10min to obtain the sample piece with the hydrophilic coating.

In example 10, for the convenience of performance test, an aluminum plate was used as a test piece, that is, an aluminum plate was subjected to sand blasting, and a passivation solution coating including chromate was applied to the sand-blasted aluminum plate. The aluminum plate used for the test sample piece is basically the same as the material of the conventional aluminum heat exchanger in the field.

Example 10

The difference from embodiment 1 is that the coating material of embodiment 10 is specifically a passivation film layer including chromate, specifically:

(1) And providing the test sample piece after sand blasting treatment.

(2) And (2) coating the surface of the test sample piece in the step (1) with a passivation solution coating containing chromate in a dip-coating mode, controlling the reaction temperature at 40 ℃, controlling the dip-coating time at 2min, taking out, blowing off redundant feed liquid by using an air gun, and fixing at the temperature of 40 ℃ for more than 10min to obtain the sample piece with the chromate passivation film layer.

Comparative example 1

The test sample of comparative example 1 did not perform the step of sand blasting as compared to example 1. Specifically, comparative example 1 includes the following steps:

(1) And (3) coating the rare earth conversion solution containing cerium on the surface of the test sample piece in a dip-coating mode, controlling the dip-coating time to be about 10min at the reaction temperature of 50 ℃, taking out an air gun and drying the air gun to obtain the sample piece with the cerium conversion film.

(2) And (2) on the basis of the sample piece obtained in the step (1), coating a hydrophobic coating comprising silane sol on the surface of the cerium conversion film in a dip-coating mode, wherein the dip-coating frequency is 1, the dip-coating duration is controlled to be about 2min, taking out the sample piece, blowing off redundant feed liquid by using an air gun, and then fixing the sample piece at the temperature of 120 ℃ for more than 20min to obtain the sample piece with the rare earth conversion coating and the hydrophobic coating.

Comparative example 2

The test piece of comparative example 2 did not perform the step of grit blasting compared to example 1, but the test piece of comparative example 2 was acid washed before applying the coating, specifically:

(1) And (3) immersing the test sample piece into a hydrochloric acid solution with the concentration of 5%, ultrasonically etching for 10min at room temperature, taking out, cleaning with deionized water, and airing for later use.

(2) And (2) coating the rare earth conversion solution containing cerium on the surface of the sample piece to be tested in a dip coating mode on the basis of the sample piece in the step (1), controlling the dip coating time to be about 10min at the reaction temperature of 50 ℃, taking out an air gun and drying the air gun to obtain the sample piece with the cerium conversion film.

(3) And (3) on the basis of the sample piece obtained in the step (2), coating a hydrophobic coating comprising silane sol on the surface of the cerium conversion film in a dip-coating mode, wherein the dip-coating frequency is 1 time, the dip-coating duration is controlled to be about 2min, taking out the sample piece, blowing off redundant feed liquid by using an air gun, and fixing the sample piece at the temperature of 120 ℃ for more than 20min to obtain the sample piece with the rare earth conversion coating and the hydrophobic coating.

Comparative example 3

The test piece of comparative example 3 did not perform the grit blasting step compared to example 1, but the test piece of comparative example 3 was base washed before the coating was applied, specifically:

(1) And (3) immersing the test sample piece into 1mol/L NaOH solution, ultrasonically etching for 10min at room temperature, taking out, cleaning with deionized water, and airing for later use.

(3) And (3) on the basis of the sample piece obtained in the step (2), coating a hydrophobic coating comprising silane sol on the surface of the cerium conversion film in a dip-coating mode, wherein the dip-coating frequency is 1, the dip-coating duration is controlled to be about 2min, taking out the sample piece, blowing off redundant feed liquid by using an air gun, and then fixing the sample piece at the temperature of 120 ℃ for more than 20min to obtain the sample piece with the rare earth conversion coating and the hydrophobic coating.

Comparative example 4

The test sample of comparative example 4 did not perform the step of sand blasting as compared to example 9. Other steps are similar, and redundant description is omitted.

Comparative example 5

The test sample of comparative example 5 did not perform the step of sand blasting as compared to example 10. Other steps are similar, and redundant description is omitted.

Performance test

1. Description of morphology before and after blasting

Referring to fig. 8, the rough surface of an aluminum plate before and after sandblasting is compared, where in fig. 8 (a) is a schematic view of the surface of a metal substrate corresponding to an aluminum plate without sandblasting, and (b) is a schematic view of the surface of a metal substrate corresponding to an aluminum plate after sandblasting. As can be seen from the graphs (a) and (b), the surface of the metal substrate of the aluminum plate without sand blasting is relatively smooth. After sand blasting, the metal substrate surface of the aluminum plate presents an irregular rough surface, the rough surface presents a deformed wrinkle appearance as a whole, the rough surface has outwards protruding ridges and inwards recessed pit structures, and the rough surface also has barb-shaped structures at partial positions, and the positions of the barb-shaped structures can be referred to the positions of the dotted line frames in the graph (b). In the subsequent process of combining the rough surface with other coating materials, other coating materials can be filled in the pit structure and are fastened by the barb-shaped structure, the bonding force between the metal substrate and the coating materials is increased, and the morphology structure plays a role in improving the durability of the coating to a certain extent.

In general, the rugged rough surface of the metal substrate after sand blasting is relatively uniform, the rugged positions in the whole appearance are relatively uniformly distributed, and the surface of the metal substrate without sand blasting, especially the metal substrate with residual brazing flux, also shows a certain rough structure, but the rough structure is irregular, the position with the brazing flux protrudes, the position without the brazing flux is sunken, and the difference between the rough surface and the rough surface formed by sand blasting is larger. Furthermore, for the metal base material after the sand blasting treatment, the metal base material which supports and is adjacent to the rough surface is deformed due to external force in the sand blasting process, and the arrangement of the metal crystal grains is more compact and uniform relative to the metal base material at one side far away from the rough surface. If the rough surface is formed by other modes, the metal crystal grains are distributed more dispersedly and irregularly on the whole.

2. Testing of hydrophobic Corrosion resistance

The tests in this section are described by taking examples 1 to 8 and comparative example 1 as examples, and specifically, the salt spray tests were performed on the samples obtained in examples 1 to 8 and comparative example 1, respectively. The salt spray test refers to a test standard ASTM G85, an acid salt spray test is carried out, each sample is placed in a salt spray box, and the samples are taken out at regular intervals to observe the surface corrosion point condition. After the acid salt spray test, each sample is taken out, and the surface corrosion condition of the sample is observed.

TABLE 1 results of Performance test of examples and comparative examples

As can be seen from the data in table 1, the time of the salt fog corrosion spots of the samples corresponding to examples 1 and 3 is relatively latest, and the salt fog corrosion spots appear after 168 hours, and the patterns S1, S2, and S3 in fig. 9 are graphs of the salt fog test results of examples 1, 3, and 8, which are provided by the present application, after 168 hours. As can be seen from the schematic of fig. 9, after 168 hours, the number of the corresponding sample pits of example 3 is the least, and the conditions of the sample blasting are as follows: the grain diameter of the abrasive is 120 meshes, the distance between the nozzles is 100mm, and the sand blasting angle is 45 degrees. This application keeps relatively good after the salt spray experiment to the surface morphology of most embodiments of sample is ended, and most samples just appear slightly corroding the point on its surface after 140 hours salt spray experiments, illustrate the sample after the sandblast is handled, behind collocation tombarthite conversion coating and the hydrophobic coating again, and corrosion resisting property is very excellent, and this can guarantee the heat transfer performance of heat exchanger product to a certain extent, can also prolong the life of heat exchanger.

Referring to fig. 10, a graph of the results of the salt spray test for example 3 over 196h is shown in pattern P1, and graphs of the results of the salt spray test for comparative examples 1 to 3 over 24h are shown in patterns P2, P3, and P4. As is apparent from fig. 10, the corrosion points of comparative examples 1 to 3 occurred in less than 24 hours after the acid salt spray test, and the corrosion points occurred rapidly in a short time without the blasting step regardless of whether the chemical etching process such as acid washing or alkali washing was performed. And after the sample corresponding to the embodiment 3 of the application is subjected to a salt spray test for 196h, corrosion points are fewer, corrosion pits are shallower, and the overall corrosion condition is lighter. This also indicates that the samples after grit blasting had superior durability and corrosion resistance to the coating than the samples without grit blasting.

It should be noted that, if a heat exchanger product is used to perform the corrosion resistance test, the following method can be adopted, nitrogen is filled into the inner cavity of the heat exchanger until the pressure is 1MPa, then the inlet and the outlet of the heat exchanger are sealed, and a connecting pipe is reserved to connect the barometer. And then, the heat exchanger is placed in a salt spray box for a salt spray test, and the pressure value change of the barometer is observed. When the pressure of the heat exchanger drops, the corrosion perforation of a certain part of the heat exchanger is indicated, and the failure of the heat exchanger is marked. In practice, the quality of the corrosion resistance can be judged by comparing the time taken for the heat exchanger to be lowered to a certain pressure.

3. Hydrophilic durability test

In the test of the part, a flowing water test is carried out by taking the example 9 and the comparative example 4 as examples, specifically, the samples of the example 9 and the comparative example 4 are immersed in flowing water, taken out at regular intervals and dried, and the contact angle of the surface of the sample and the coating state are tested. The test results are shown in table 1, respectively:

TABLE 1

As can be seen from the data in Table 1, the contact angle of the surface of the sample of example 9 still shows better hydrophilicity after 336h of flowing water test. In contrast, in the sample of comparative example 4, after the running water test for 240 hours, the coating layer was peeled off in a large area, and it was difficult to ensure the hydrophilicity. The samples provided by the present application were more durable to hydrophilic coatings than samples that were not grit blasted.

4. Comparative salt spray test for appearance of chromate passivation coating

The tests in this section are described by taking example 10 and comparative example 5 as examples, and specifically, the salt spray tests were performed on the samples obtained in example 10 and comparative example 5, respectively. The salt spray test refers to a test standard ASTM G85, an acid salt spray test is carried out, each sample is placed in a salt spray box, and the samples are taken out at regular intervals to observe the surface corrosion point condition. In fig. 11, the F1 pattern is a graph of the results of the salt spray test for 48 hours on the sample of comparative example 5 provided in the present application, and the F1 pattern is a graph of the results of the salt spray test for 48 hours on the sample of example 10 provided in the present application. It is apparent from fig. 11 that the sample of comparative example 5 on the left side, which is not sand blasted, has a significant number of surface pits and a deep etching pit after 48 hours of salt spray test, and thus the corrosion traces can be more clearly seen. The samples subjected to the sandblasting treatment in example 10 on the right have a smaller number of surface pits, shallower pits, and a relatively better corrosion condition, and it is described that the samples subjected to the sandblasting treatment provided by the present application have a better durability against the chromate passivation film layer than the samples not subjected to the sandblasting treatment.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Although the present application has been described with reference to preferred embodiments, it is not intended to limit the scope of the claims, and many possible variations and modifications may be made by one skilled in the art without departing from the spirit of the application.

Claims

1. A method of treating a heat exchanger, the method comprising the steps of:

2. The process of claim 1, wherein the step of grit blasting the heat exchanger comprises:

and mixing the abrasive in compressed air, and spraying the abrasive to the outer surface of the heat exchanger through a spray gun.

3. The processing method according to claim 2, characterized in that it further comprises at least one of the following technical features a to d:

a. the grinding material is corundum gravel;

b. the grain size of the grinding material is 30 meshes to 280 meshes;

c. the pressure intensity of the compressed air is 0.45 MPa-0.65 MPa;

d. the number of times of sand blasting to the fin is less than or equal to 3.

4. The process of claim 1, wherein the step of grit blasting the heat exchanger is preceded by:

and the fluid inlet and the fluid outlet which are communicated with the tube cavity of the collecting pipe are blocked.

5. The process of claim 1, wherein the step of grit blasting the heat exchanger is further followed by:

carrying out ultrasonic cleaning treatment on the heat exchanger subjected to sand blasting treatment;

and drying the heat exchanger subjected to the ultrasonic cleaning treatment.

6. The process of claim 5, wherein the step of subjecting the sand blasted heat exchanger to an ultrasonic cleaning process comprises:

and ultrasonically cleaning the heat exchanger subjected to sand blasting treatment by adopting at least one of deionized water, ethanol or absolute ethanol, wherein the ultrasonic cleaning time is 5-10 min, and the ultrasonic frequency of the ultrasonic cleaning is 80-100 Hz.

7. The treatment method according to claim 5, wherein the step of drying the heat exchanger after the ultrasonic cleaning treatment further comprises:

and arranging a functional film layer on the surface of the rough surface.

8. The method as set forth in claim 7, wherein the step of providing a functional film layer on the surface of the sandblasted rough surface comprises:

coating a hydrophilic coating or a hydrophobic coating comprising a silane sol on at least a part of the rough surface, and forming a film layer comprising the silane sol on the rough surface after curing;

or,

coating a rare earth conversion coating on at least part of the rough surface, and forming a rare earth conversion coating comprising a compound containing a rare earth element on the rough surface after curing;

coating a hydrophilic coating or a hydrophobic coating comprising silane sol on at least part of the surface of the rare earth conversion coating, and after curing, correspondingly forming a film layer comprising silane sol on the surface of the rare earth conversion coating;

or,

and coating a coating comprising chromate on at least partial area of the rough surface, and forming a chromium salt passivation film layer on the rough surface after curing.

9. A heat exchanger is characterized by comprising a collecting pipe, fins and a plurality of heat exchange pipes which are fixed together;

at least part of the fin is connected between two adjacent heat exchange tubes;

the outer surface of the metal base material corresponding to at least one of the collecting pipe, the fins and the heat exchange pipe comprises an uneven rough surface, and the roughness (Ra) of the rough surface meets the condition that Ra is more than or equal to 0.5 mu m and less than or equal to 10 mu m.

10. The heat exchanger according to claim 9, wherein the header, the fins and the heat exchange tubes of the heat exchanger are integrally fixed by brazing assembly;

the roughness (Ra) of the rough surface at each position of the heat exchanger meets the condition that Ra is more than or equal to 1 mu m and less than or equal to 3 mu m;

the material of the metal base material corresponding to any one of the collecting pipe, the fin and the heat exchange pipe comprises at least one of aluminum, copper and stainless steel, and the rough surface of the metal base material is formed after sand blasting treatment.

11. The heat exchanger of claim 9, wherein the fins are of a corrugated configuration extending lengthwise of the heat exchange tubes;

the fin comprises a plurality of fin units arranged along the length direction of the heat exchange tube, the fin units are sequentially connected, wave crests or wave troughs in a wave structure corresponding to the fin are formed at the positions where adjacent fin units are connected, and the fin is fixed with the heat exchange tube at the positions where the adjacent fin units are connected.

12. The heat exchanger of claim 11, wherein the heat exchange tube comprises two side faces and two end faces; the two side surfaces are respectively positioned at two opposite sides of the heat exchange tube in the thickness direction; the two end faces are respectively positioned at two opposite sides of the width direction of the heat exchange tube;

the roughness of the rough surface at the end surface is equal to or greater than the roughness of the rough surface at the side surface.

13. The heat exchanger according to claim 12, wherein the side surface of the heat exchange tube is divided into three regions in the width direction thereof, the three regions of the side surface of the heat exchange tube include two first regions and a second region located between the two first regions, and the roughness of the roughened surface in the first regions is equal to or greater than the roughness of the roughened surface in the second regions;

and/or the surface of the fin unit is divided into three regions according to the width direction of the heat exchange tube, the three regions of the surface of the fin unit comprise two third regions and a fourth region located between the two third regions, and the roughness of the rough surface in the third region is greater than or equal to that of the rough surface in the fourth region.