A titanium nano-coated heat exchanger

Abstract

The present invention provides a titanium nano - coated heat exchanger and its coating method, including a main body and heat exchange tubes arranged inside the main body. An air inlet and an air outlet are respectively arranged on both sides of the main body, and a water inlet and a water outlet are respectively arranged at both ends of the heat exchange tubes; the inner wall of the main body and / or the inner wall of the air inlet and / or the inner wall of the air outlet and / or the inner wall and / or outer wall of the heat exchange tubes serve as the bottom surface, and a titanium nano - coating is provided on the bottom surface. The present invention provides a titanium nano - coated heat exchanger. Since the bottom surface of the heat exchanger is provided with a titanium nano - coating, the requirement for the corrosion resistance of the heat exchanger manufacturing material is reduced, thereby reducing the overall cost of the heat exchanger and decreasing the capital investment of enterprises. The titanium nano - coating has the characteristics of a dense structure, a high surface smoothness, a small friction coefficient, inhibits the fouling inside the heat exchanger, improves the heat exchange efficiency, and at the same time has good corrosion resistance, which can extend the service life of the heat exchanger.

Description

Technical Field

[0001] The present invention relates to the technical field of heat exchangers, and more specifically, to a titanium nano-coated heat exchanger. Background Art

[0002] In recent years, with the continuous enhancement of people's awareness of environmental protection, energy conservation and consumption reduction, China has paid increasing attention to the recovery of flue gas waste heat. By using the heat of flue gas to heat the circulating water of the hot water heating system, the heating capacity is improved, the coal consumption is reduced, and good energy-saving and emission-reduction effects are achieved. In the flue gas waste heat recovery system, the heat exchanger is a necessary device to meet the process conditions and is also one of the main devices to improve energy utilization efficiency.

[0003] Since the flue gas contains corrosive media such as H2S, SO x , NO x , Cl-, F-, H+, etc., they will chemically react with the heat exchanger material at a certain temperature and humidity to form soluble salts, gradually corroding and damaging the heat exchanger; due to the change of flue gas temperature, the soluble salts will deposit in the heat exchanger, and over time, a dense and hard water scale will form on the inner surface of the heat exchanger. Since the heat transfer coefficient of the water scale is extremely low, the thermal efficiency of the heat exchanger continuously decreases, causing huge losses to the enterprise.

[0004] The main methods to solve the above problems in the prior art are: (1) manufacturing the heat exchanger with corrosion-resistant materials, generally using expensive materials such as titanium and Hastelloy. These materials have high prices, making the cost of the heat exchanger too high and increasing the overall cost of the entire system. Moreover, most of these materials have relatively low heat transfer coefficients, greatly affecting the heat exchange effect. (2) Using 316 stainless steel + nickel metal plating. This method has been proven unable to meet the requirements of anti-flue gas corrosion after operation, with serious rust blockage, and needs to be replaced within no more than two years of operation, unable to meet the enterprise operation and environmental protection requirements. (3) Using nitriding technology. Although the nitriding technology has good corrosion resistance, it is difficult to solve the problems of scaling and increased material brittleness after high-temperature treatment.

[0005] Therefore, the problems existing in the prior art need to be further improved and developed. Summary of the Invention

[0006] (1) Invention Objective: To solve the problems existing in the above prior art, the objective of the present invention is to provide a titanium nano-coated heat exchanger and its coating method.

[0007] (2) Technical solution: To solve the above technical problems, the present technical solution provides a titanium nano-coated heat exchanger, including a main body and heat exchange tubes arranged inside the main body. An air inlet and an air outlet are respectively arranged on both sides of the main body, and a water inlet and a water outlet are respectively arranged at both ends of the heat exchange tubes. The inner wall of the main body and / or the inner wall of the air inlet and / or the inner wall of the air outlet and / or the inner wall and / or outer wall of the heat exchange tubes serve as the bottom surface. The surface of the bottom surface is smooth and free of attachments, and the surface roughness of the bottom surface is 40 - 70 μm; a titanium nano-coating is provided on the bottom surface, and the total thickness of the titanium nano-coating reaches more than 270 μm. The titanium nano-coating includes 2 primer films and 4 topcoat films, and the total thickness range is 270 μm - 300 μm. The titanium nano-coating includes a primer layer and a topcoat layer. The primer layer includes at least two primer films, and the topcoat layer includes at least four topcoat films; the composition and proportion of the primer film include: epoxy resin: 43%, titanium nano-metal powder: 24%, acetone: 18%, curing agent: 5%, mica powder: 10%; the composition and proportion of the topcoat film include: polyurethane resin: 63%, titanium nano-metal powder: 15%, acetone: 12%, curing agent: 4%, mica powder: 6%.

[0008] The present invention also provides a coating method for a titanium nano-coated heat exchanger, including the following steps:

[0009] Step 1: Clean, derust and roughen the surface of the bottom surface to make the surface roughness reach 40 - 70 μm;

[0010] Step 2: Mix epoxy resin, titanium nano-metal powder, acetone, curing agent and mica powder respectively in different proportions to form the primer and topcoat of the titanium nano-polymer coating, and add a diluent;

[0011] Step 3: Coat two layers of primer and four layers of topcoat on the bottom surface in sequence and cure to obtain a titanium nano-coated heat exchanger;

[0012] Step 4: Conduct appearance inspection, thickness inspection, leak point inspection and adhesion inspection on the titanium nano-coated heat exchanger.

[0013] A coating method for a titanium nano-coated heat exchanger, wherein the specific steps of Step 1 include:

[0014] Step 11: Use an alkaline solution to conduct high-pressure hot water cleaning on the bottom surface to remove grease and dirt;

[0015] Step 12: Use quartz sand as abrasive material, add it to a sandblaster, and conduct sandblasting on the bottom surface;

[0016] Step 13: After sandblasting, use a vacuum cleaner, dry and clean compressed air or a brush to remove dust from the bottom surface to ensure that there is no residue on the surface.

[0017] A coating method for a titanium nano - coated heat exchanger, wherein the particle sizes of the abrasive materials are the same or different, and the proportion distribution of the abrasive materials with different particle sizes is approximately equal; the compressed air pressure in the sandblasting machine is controlled at 0.4 - 0.8 Mpa.

[0018] A coating method for a titanium nano - coated heat exchanger, wherein adding a diluent in step 2 specifically means: preparing the primer and the topcoat according to the correct ratio, adding no more than 20% of the diluent to the primer and the topcoat respectively, stirring evenly and then standing for 5 - 10 minutes to eliminate air bubbles, and the diluent is ethylene glycol monomethyl ether.

[0019] A coating method for a titanium nano - coated heat exchanger, wherein step 3 specifically includes the following steps:

[0020] Step 31: After the bottom surface is treated and cleaned, apply two coats of the primer in the titanium nano - polymer coatings, and the coating interval between the two coats of primer is 4 hours to ensure the interlayer bonding force;

[0021] Step 32: Wait for 4 hours. After the primer is cured, apply four coats of the topcoat in the titanium nano - polymer coatings. The coating interval between each coat of topcoat is 4 hours. During this period, rotate the constructed bottom surface by 180 degrees to ensure uniform coating;

[0022] Step 33: After all coatings are applied, cure at room temperature for more than 7 days.

[0023] A coating method for a titanium nano - coated heat exchanger, wherein after each coat of primer or topcoat is applied, check the appearance and thickness of the primer film or topcoat film to ensure no missed coating and uniform thickness for each layer; when there is a missed coating or insufficient thickness, make up the coating in time; check the thickness of the primer layer after the last coat of primer film is dry and before curing. If the thickness is less than 80 μm, increase the number of coating layers until it is qualified; check the thickness of the topcoat layer after the last coat of topcoat film is dry and before curing. If the thickness is less than 170 μm, increase the number of coating layers until it is qualified.

[0024] A coating method for a titanium nano - coated heat exchanger, wherein the appearance inspection specifically means visually checking whether the surface of the titanium nano - coating is flat and smooth, and whether there are defects such as missed coating, stickiness, peeling, air bubbles and scars;

[0025] The thickness inspection specifically means using a thickness gauge to detect the thickness of the titanium nano - coating, and the thinnest point of the titanium nano - coating should be ≥150 μm;

[0026] The leakage point inspection specifically means using a 5 - 10 times magnifying glass to check, and those without leakage points are qualified;

[0027] The specific bond strength inspection is as follows: use a blade to cut through the titanium nano - coating to form a V - shaped incision, pick and peel the titanium nano - coating inside the incision, and test its bond strength.

[0028] A coating method for a titanium nano - coating heat exchanger. When performing thickness inspection, select three areas to be detected on the surface of the titanium nano - coating at the part to be inspected. For each area to be detected, 10% of the area is inspected. Taking 1m 2 as a detection area, at least 2 points are randomly selected for each detection area, and the points are evenly distributed. The number of randomly selected points at the weld is not less than 30% of the total number of detected points.

[0029] A coating method for a titanium nano - coating heat exchanger. The sampling rate of leakage point inspection is equal to or greater than 5% of the coating area, and key inspection is carried out on weak links such as the weld. If the number of leakage points is 1 per m 2 , repair is carried out. If the number of leakage points exceeds 1 per m 2 , overall recoating is carried out.

[0030] (III) Beneficial effects: The present invention provides a titanium nano - coating heat exchanger. Since the bottom surface of the heat exchanger is provided with a titanium nano - coating, the requirement for the corrosion resistance of the heat exchanger manufacturing material is reduced, thereby reducing the overall cost of the heat exchanger and reducing the capital investment of the enterprise. The titanium nano - coating has the characteristics of a dense structure, high surface smoothness, a small friction coefficient, inhibits scale formation inside the heat exchanger, improves the heat exchange efficiency, and at the same time has good corrosion resistance, which can extend the service life of the heat exchanger. Brief Description of the Drawings

[0031] Figure 1 is a schematic diagram of the overall structure of a titanium nano - coating heat exchanger of the present invention;

[0032] Figure 2 is a schematic diagram of the heat exchange tube structure of a titanium nano - coating heat exchanger of the present invention;

[0033] Figure 3 is a schematic diagram of the coating method of a titanium nano - coating heat exchanger of the present invention;

[0034] Reference numerals in the drawings:

[0035] 1 - main body, 2 - air inlet, 3 - air outlet, 4 - water inlet, 5 - water outlet, 6 - heat exchange tube, 7 - liquid collection box, 8 - drain outlet, 9 - titanium nano - coating. Detailed Embodiments

[0036] The present invention is further described in detail below in conjunction with preferred embodiments. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0037] The accompanying drawings are schematic diagrams of embodiments of the present invention. It should be noted that the drawings are only examples and are not drawn to scale, and should not be used to limit the actual protection scope of the present invention.

[0038] This technical solution provides a titanium nano-coated heat exchanger, such as Figure 1 As shown, it comprises: a main body 1 and a heat exchange tube 6 arranged inside the main body 1, an air inlet 2 and an air outlet 3 are respectively arranged on both sides of the main body 1, high-temperature flue gas enters the main body 1 from the air inlet 2, and low-temperature flue gas leaves the main body 1 from the air outlet 3, and a water inlet 4 and a water outlet 5 are respectively arranged at both ends of the heat exchange tube 6, low-temperature liquid enters the heat exchange tube 6 from the water inlet 4, and high-temperature liquid leaves the heat exchange tube 6 from the water outlet 5. When the high-temperature flue gas passes through the heat exchange tube 6, it contacts the wall surface and transfers heat to the low-temperature liquid in the heat exchange tube 6, thereby achieving the effect of heat exchange.

[0039] Preferably, in the present invention, a liquid collecting box 7 is provided inside the main body 1 and below the heat exchange tube 6, and a drain port 8 is connected below the liquid collecting box 7 for collecting and discharging condensed water generated during the heat exchange process from inside the main body 1.

[0040] Preferably, the inner wall of the main body 1 and / or the inner wall of the air inlet 2 and / or the inner wall of the air outlet 3 and / or the inner wall and / or the outer wall of the heat exchange tube 6 are provided with a titanium nano coating 9. Figure 2 As shown, the outer surface of the heat exchange tube 6 is provided with a titanium nano coating 9. The inner wall of the main body 1 and / or the inner wall of the air inlet 2 and / or the inner wall of the air outlet 3 and / or the inner wall and / or the outer wall of the heat exchange tube 6 can be called the bottom surface, and the surface of the bottom surface is smooth and free of attachments, and the surface roughness of the bottom surface is 40-70 μm.

[0041] Preferably, the titanium nano coating comprises a primer layer and a topcoat layer. The primer layer comprises at least two primer films, i.e., the primer needs to be applied at least twice, each application forms a primer film; the topcoat layer comprises at least four topcoat films, i.e., the topcoat needs to be applied at least four times, each application forms a topcoat film.

[0042] Preferably, the composition and proportion of the primer film are as follows: epoxy resin: 43%, titanium nano metal powder: 24%, acetone: 18%, curing agent: 5%, mica powder: 10%. The composition and proportion of the topcoat film are as follows: polyurethane resin: 63%, titanium nano metal powder: 15%, acetone: 12%, curing agent: 4%, mica powder: 6%.

[0043] Preferably, the thickness range of the primer layer is 80μm - 100μm, the thickness range of the topcoat layer is 170μm - 200μm, and the total thickness range of the titanium nano coating is 270μm - 300μm.

[0044] This technical solution also provides a coating method for a titanium nano coating heat exchanger, as Figure 3 shown, including the following steps:

[0045] Step 1: Clean, derust, and roughen the surface of the bottom surface to make the surface roughness reach 40 - 70μm;

[0046] Step 2: Mix epoxy resin, titanium nano metal powder, acetone, curing agent, and mica powder in different proportions to form the primer and topcoat of the titanium nano polymer coating, and add a diluent;

[0047] Step 3: Coat two layers of primer and four layers of topcoat on the bottom surface in sequence and cure to obtain a heat exchanger with a titanium nano coating;

[0048] Step 4: Conduct appearance inspection, thickness inspection, leak point inspection, and adhesion inspection on the heat exchanger with a titanium nano coating.

[0049] Preferably, the specific steps of Step 1 include:

[0050] Step 11: Use alkaline solution to conduct high-pressure hot water cleaning on the bottom surface to remove grease and dirt. The bottom surface is the inner wall of the main body 1 and / or the inner wall of the air inlet 2 and / or the inner wall of the air outlet 3 and / or the inner wall and outer wall of the heat exchange tube 6.

[0051] Step 12: Use quartz sand as abrasive, add it to a sandblasting machine, and conduct sandblasting on the bottom surface. After sandblasting, the surface roughness of the bottom surface reaches 40 - 70μm, and there is no visible grease, dirt, oxide scale, rust, and paint coating attachments on the surface, and a uniform metallic luster is shown.

[0052] Step 13: After sandblasting, use a vacuum cleaner, dry and clean compressed air, or a brush to remove dust from the bottom surface to ensure that there is no residue on the surface.

[0053] Preferably, the sand materials may have the same or different particle sizes, and the proportion distribution of the sand materials with different particle sizes is roughly equal; the compressed air pressure of the sandblasting machine is controlled at 0.4-0.8 Mpa.

[0054] Preferably, in step 2, epoxy resin, titanium nano metal powder, acetone, curing agent and mica powder are respectively mixed in different proportions to form the primer and topcoat of the titanium nano polymer coating. The proportions of the components in the primer are: epoxy resin: 43%, titanium nano metal powder: 24%, acetone: 18%, curing agent: 5%, mica powder: 10%. The proportions of the components in the topcoat are: polyurethane resin: 63%, titanium nano metal powder: 15%, acetone: 12%, curing agent: 4%, mica powder: 6%.

[0055] Prepare the primer and topcoat according to the correct ratio, and add a diluent not exceeding 20% of the total amount to the primer and the topcoat respectively to adjust the viscosity to meet the ideal spraying requirements. Preferably, the diluent is ethylene glycol monomethyl ether (MOE). After stirring the diluent and the primer or the diluent and the topcoat evenly, let it stand for 5-10 minutes to eliminate bubbles. The mixed primer and topcoat can be applied after filtering through a 100-mesh filter screen.

[0056] Preferably, in step 3, two layers of primer and four layers of topcoat are sequentially applied to the bottom surface and cured, which specifically includes the following steps:

[0057] Step 31: After the bottom surface is processed and cleaned, apply two coats of the primer in the titanium nano polymer coating. The coating interval between the primers is 4 hours to ensure the interlayer bonding force.

[0058] Step 32: Wait for 4 hours. After the primer is cured, apply four coats of the topcoat in the titanium nano polymer coating. The coating interval between each coat of the topcoat is 4 hours. During this period, the bottom surface under construction needs to be rotated 180 degrees to ensure uniform coating.

[0059] Step 33: After all the coatings are applied, cure at room temperature for more than 7 days.

[0060] Preferably, an airless spraying machine is used to apply the coating to the surface of the bottom surface. More preferably, before the coating operation, a small amount of the mixed titanium nano polymer coating can be weighed for trial coating and verification to ensure the single film thickness and quality.

[0061] Preferably, once the titanium nano polymer coating thickens due to excessive reaction during the spraying process, the coating should be immediately stopped. This coating has been scrapped and should be re-formulated. The overreaction time of the coating is related to the ambient temperature. The higher the temperature, the shorter the required time and the less the material should be formulated. Conversely, the lower the temperature, the longer the required time and the appropriate amount of the formulated material can be increased.

[0062] Preferably, in step 3, after each application of a primer or a topcoat, check the appearance and thickness of the primer film or the topcoat film to ensure that there is no missed coating and the thickness of each layer is uniform; when there is a missed coating or the thickness is insufficient, make up the coating in a timely manner.

[0063] More preferably, after the last primer film has dried and before curing, check the thickness of the primer layer. If the thickness is less than 80 μm, the number of coating layers needs to be increased until it is qualified. After the last topcoat film has dried and before curing, check the thickness of the topcoat layer. If the thickness is less than 170 μm, the number of coating layers needs to be increased until it is qualified.

[0064] Preferably, in step 4, the appearance inspection specifically is to visually check whether the surface of the titanium nano - coating is flat and smooth, and whether there are defects such as missed coating, stickiness, peeling, bubbles, and scars.

[0065] The thickness inspection specifically is to use a thickness gauge to detect the thickness of the titanium nano - coating. The thinnest point of the titanium nano - coating should be ≥150 μm; preferably, when conducting the thickness inspection, select three areas to be detected on the surface of the titanium nano - coating at the part to be inspected, and take 10% of the area of each area to be detected for inspection. Taking 1 m 2 as a detection area, at least 2 points should be randomly selected for each detection area, and the points should be evenly distributed. The number of randomly selected points at the weld should be no less than 30% of the total number of detected points.

[0066] If there is more than 1 unqualified point in each area to be detected, then this area is unqualified. If the unqualified area does not exceed 5%, then recoat the area where the thickness of the titanium nano - coating is less than 90% of the specified thickness; if the unqualified area exceeds 5%, then double - check the corresponding part. If the unqualified area still exceeds 5% after double - checking, then the thickness of the titanium nano - coating in this part is unqualified, and recoat until it is qualified; if the unqualified area after double - checking does not exceed 5%, then recoat the area where the thickness of the titanium nano - coating is less than 90% of the specified thickness.

[0067] The leak - point inspection specifically is as follows: Since the titanium nano - polymer coating is an electrostatic - conductive coating, an electric - spark leak detector cannot be used. Use a 5 - 10 times magnifying glass to check. Those without leak points are qualified. The sampling rate of the leak - point inspection is equal to or greater than 5% of the coating area, and key inspection should be carried out on weak links such as welds. If the number of leak points is 1 per m 2 , conduct repairs. If the number of leak points exceeds 1 per m 2 , conduct a full recoat.

[0068] The adhesion inspection specifically is: Use a knife blade to cut through the titanium nano - coating to form a V - shaped incision, and pick and peel the titanium nano - coating inside the incision to test its adhesion.

[0069] Preferably, use a sharp blade to vertically cut through the titanium nano-coating to form a V-shaped incision with a side length of about 40 mm and an included angle of about 45 o . Use the tip of the knife to pick and peel the titanium nano-coating inside the incision from the intersection of the cutting lines. If the titanium nano-coating at the picked-up part shows brittle punctate fracture, the adhesion of the titanium nano-coating is qualified; if the titanium nano-coating at the picked-up part shows a situation of being picked up or peeled off in pieces, the adhesion of the titanium nano-coating is unqualified.

[0070] Preferably, during the adhesion test, select three measurement points on the surface of the titanium nano-coating at the part to be inspected. If the measurement points are qualified, the adhesion of this part is qualified; if there is an unqualified measurement point, double-check the unqualified part; if there is still one unqualified point after double-checking, the adhesion of the titanium nano-coating of this part is unqualified.

[0071] The above content is an illustration of the preferred embodiments of the present invention, which can help those skilled in the art to more fully understand the technical solutions of the present invention. However, these embodiments are only examples and cannot be considered that the specific implementation manners of the present invention are limited to the descriptions of these embodiments. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions and transformations can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A titanium nano-coated heat exchanger, comprising a main body and a heat exchange tube arranged inside the main body, wherein an air inlet and an air outlet are respectively arranged on both sides of the main body, and a water inlet and a water outlet are respectively arranged at both ends of the heat exchange tube, characterized in that: The inner wall of the main body and / or the inner wall of the air inlet and / or the inner wall of the air outlet and / or the inner wall and / or the outer wall of the heat exchange tube is the bottom surface, the surface of the bottom surface is smooth and free of attachments, and the surface roughness of the bottom surface is 40 to 70 μm; The bottom surface is provided with a titanium nano coating, the total thickness of the titanium nano coating is in the range of 270 μm to 300 μm, the titanium nano coating comprises a primer layer and a topcoat layer, the primer layer comprises at least two primer films, and the topcoat layer comprises at least four topcoat films; The components and proportions of the primer film include: epoxy resin: 43%, titanium nano-metal powder: 24%, acetone: 18%, curing agent: 5%, mica powder: 10%; the components and proportions of the topcoat film include: polyurethane resin: 63%, titanium nano-metal powder: 15%, acetone: 12%, curing agent: 4%, mica powder: 6%; The thickness of the primer layer ranges from 80 μm to 100 μm, and the thickness of the topcoat layer ranges from 170 μm to 200 μm.

2. A coating method for a titanium nano-coated heat exchanger, applicable to the titanium nano-coated heat exchanger according to claim 1, characterized in that: The following steps are involved: Step 1: Clean, remove rust and roughen the bottom surface to make the surface roughness reach 40-70μm; Step 2: Mix epoxy resin, titanium nano metal powder, acetone, curing agent and mica powder in different proportions to form a primer and a topcoat of the titanium nano polymer coating, and add a diluent; Step 3: Apply two layers of primer and four layers of topcoat on the bottom surface in sequence and cure them to obtain a titanium nano-coated heat exchanger; Step 4: Perform appearance inspection, thickness inspection, leakage inspection and adhesion inspection on the titanium nano-coated heat exchanger; The step 1 specifically includes: Step 11: Use lye to wash the bottom surface with high pressure hot water to remove grease and dirt; Step 12: Use quartz sand as abrasive material, add it into the sandblasting machine, and sandblast the bottom surface; Step 13: After sandblasting, use a vacuum cleaner, dry and clean compressed air or a brush to remove dust from the bottom surface to ensure that there is no residue on the surface; The step 3 specifically comprises the following steps: Step 31: After the bottom surface is treated and cleaned, two coats of the primer in the titanium nano polymer coating are applied, and the interval between the coatings of the primers is 4 hours to ensure the interlayer bonding strength; Step 32: After waiting for 4 hours and the primer is cured, four coats of the titanium nano polymer coating are applied, with each coat of topcoat applied at an interval of 4 hours, during which the bottom surface to be constructed is rotated 180 degrees to ensure uniform coating; Step 33: After all coatings are applied, cure at room temperature for more than 7 days.

3. The coating method of a titanium nano-coating heat exchanger according to claim 2, characterized in that: The particle sizes of the sand materials are the same or different, and the proportions of the sand materials with different particle sizes are roughly equal; the compressed air pressure in the sand blasting machine is controlled at 0.4-0.8Mpa.

4. The coating method of a titanium nano-coating heat exchanger according to claim 2, characterized in that: The step 2 of adding the diluent specifically comprises: preparing the primer and the topcoat in a correct ratio, and adding no more than 20% of the diluent to the primer and the topcoat respectively, stirring evenly and then standing for 5-10 minutes to eliminate bubbles, wherein the diluent is ethylene glycol methyl ether.

5. The coating method of a titanium nano-coating heat exchanger according to claim 2, characterized in that: After each application of a primer or topcoat, check the appearance and thickness of the primer film or topcoat to ensure that there is no missing coating and that the thickness of each layer is uniform; if there is a missing coating or the thickness is insufficient, apply additional coating in time; after the last primer film is completely dry and before solidification, check the thickness of the primer layer. If the thickness is less than 80μm, increase the number of coating layers until it is qualified; after the last topcoat film is completely dry and before solidification, check the thickness of the topcoat layer. If the thickness is less than 170μm, increase the number of coating layers until it is qualified.

6. The coating method of a titanium nano-coating heat exchanger according to claim 2, characterized in that: Specifically, the appearance inspection includes visually inspecting whether the surface of the titanium nano-coating is flat and smooth, and whether there are defects such as missing coating, stickiness, peeling, bubbles and scars; The thickness inspection specifically includes using a thickness gauge to detect the thickness of the titanium nano coating, and the thinnest point of the titanium nano coating should be ≥150 μm; The leakage point inspection is specifically to use a 5-10 times magnifying glass to inspect, and the one without leakage points is qualified; The adhesion test is specifically to use a knife blade to cut through the titanium nano-coating to form a V-shaped incision, and then peel off the titanium nano-coating in the incision to test its adhesion.

7. A method for coating a titanium nano-coating heat exchanger according to claim 6, characterized in that: When conducting thickness inspection, three areas to be inspected are selected on the surface of the titanium nano-coating at the part to be inspected, and 10% of the area of ​​each area to be inspected is taken for inspection. 2 For one inspection area, at least 2 points shall be randomly inspected in each inspection area, and the points shall be evenly distributed. The number of randomly inspected points at the weld shall not be less than 30% of the total number of inspection points.

8. The coating method of a titanium nano-coating heat exchanger according to claim 6, characterized in that: The spot check rate of the leakage point inspection is equal to or greater than 5% of the coating area, and the weak links at the welds are inspected in particular; if the number of leakage points is 1 / m 2 , repair, if the number of leaks exceeds 1 / m 2 , for comprehensive recoating.

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