Air tightness detection method for plate-fin heat exchanger

Abstract

The invention discloses a method for detecting the air tightness of a plate-fin heat exchanger, and provides a method for detecting whether a leakage point exists in the heat exchanger through secondary negative pressure, which comprises the following steps of: forming a closed inner cavity in the plate-fin heat exchanger, then vacuumizing the inner cavity of the plate-fin heat exchanger, stopping vacuumizing when the inner cavity reaches a preset primary negative pressure value, and stopping vacuumizing when the inner cavity reaches the preset primary negative pressure value. The negative pressure change of the inner cavity is observed, and if the first-stage negative pressure value of the inner cavity is not kept unchanged after a period of time, it is judged that serious leakage points exist in the plate-fin heat exchanger, and the air tightness is unqualified; and if the first-stage negative pressure value of the inner cavity is kept unchanged after a period of time, the inner cavity of the plate-fin heat exchanger continues to be vacuumized, and when the inner cavity reaches the preset second-stage negative pressure value and can be kept for a certain period of time, it is judged that the air tightness of the plate-fin heat exchanger is qualified. The air tightness detection of the plate-fin heat exchanger can be quickly and efficiently completed, a drying step in a pressure water detection method is avoided, the limitation of the size of the detected heat exchanger by the size of a water tank is overcome, the detection environment is improved, and the detection efficiency is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of air tightness detection of heat exchangers, and in particular relates to an air tightness detection method for a plate-fin heat exchanger. Background Art

[0002] The function of a heat exchanger is to transfer heat from one medium to another, thereby achieving the purpose of heating or cooling. Plate-fin heat exchangers have the characteristics of high heat transfer efficiency and compact structure, and are widely used in aerospace, shipbuilding, engineering machinery, wind power and other fields.

[0003] The air tightness of the heat exchanger is related to its normal operation. Air tightness testing is an important part of the quality inspection of heat exchangers in production. The purpose is to ensure that there is no leakage in all parts of the heat exchanger to ensure its normal operation.

[0004] At present, air tightness testing methods can be divided into two categories according to the different testing media: wet testing method and dry testing method.

[0005] The wet test method is to fill the heat exchanger with high-pressure gas in a liquid environment and judge its air tightness by observing whether bubbles are generated on its surface, such as the soap bubble method and pressure water test method;

[0006] The dry test method uses special testing equipment to determine the air tightness of the heat exchanger, such as helium mass spectrometry, differential pressure method, etc. Since the differential pressure method requires a reference object for comparison, and the internal volume of the heat exchanger varies, this method is difficult to be widely used in the heat exchanger industry.

[0007] At present, the pressure water inspection method is often used to detect leakage in plate-fin heat exchangers. This method is low-cost and simple to operate, but the size of the heat exchanger being inspected is often affected by the size of the water tank. In addition, the heat exchanger needs to be lifted and placed in water before the water inspection. After the water inspection, the water in the outer fins of the plate-fin heat exchanger is not easy to clean up, and an additional drying or baking step is required, which greatly reduces the inspection efficiency and seriously affects the progress of the inspection link. It is difficult to meet the needs of large-size and large-volume plate-fin heat exchanger inspection in actual production. Summary of the invention

[0008] The present invention aims to provide a plate-fin heat exchanger air tightness detection method to make up for the shortcomings of the existing plate-fin heat exchanger air tightness detection process, avoid the drying or baking steps in the pressure water detection method, overcome the difficulty that the size of the heat exchanger to be inspected is limited by the size of the water tank, and improve the detection environment so as to complete the air tightness detection quickly and efficiently.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A method for detecting air tightness of a plate-fin heat exchanger, comprising:

[0011] The plate-fin heat exchanger to be inspected is placed in the atmospheric environment, and all the nozzles connected to the inner cavity of the plate-fin heat exchanger are blocked to form a closed inner cavity inside the plate-fin heat exchanger. Then, the inner cavity of the plate-fin heat exchanger is evacuated. When the inner cavity reaches a predetermined first-level negative pressure value, the evacuation is stopped, and the change of the negative pressure in the inner cavity of the plate-fin heat exchanger is observed. If the first-level negative pressure value of the inner cavity fails to remain unchanged after a period of time, it is determined that the plate-fin heat exchanger has a serious leak and the air tightness is unqualified; if the first-level negative pressure value of the inner cavity remains unchanged after a period of time, the inner cavity of the plate-fin heat exchanger continues to be evacuated. When the inner cavity reaches a predetermined second-level negative pressure value and can be maintained for a period of time, it is determined that the air tightness of the plate-fin heat exchanger is qualified.

[0012] As a solution, the nozzle on the plate-fin heat exchanger communicating with the inner cavity is connected to the vacuum pump through an air valve.

[0013] As a solution, the nozzle on the plate-fin heat exchanger communicating with the inner cavity is connected to a vacuum gauge.

[0014] As an option, the plate-fin heat exchanger is a heat exchanger made of aluminum alloy.

[0015] As an option, the inner cavity volume of the plate-fin heat exchanger is 1 to 100 liters.

[0016] As a solution, the predetermined first-stage negative pressure value of the inner cavity of the plate-fin heat exchanger is 1×10 -2 Pa~1×10 - 4 Pa.

[0017] As a solution, the predetermined secondary negative pressure value of the inner cavity of the plate-fin heat exchanger is 1×10 -3 Pa~1×10 - 4 Pa.

[0018] As an approach, the period of time is at least 3 to 5 minutes.

[0019] Compared with the prior art, the present invention proposes a scheme for detecting whether there is a leak in a heat exchanger through a secondary negative pressure test based on the existing detection method. The primary negative pressure test is used to screen whether there is a serious leak, and the secondary negative pressure test is used to ensure the accuracy and reliability of the detection method. The airtightness detection method of the present invention omits the drying or baking step in the pressure water detection method, breaks through the limitation of the size of the heat exchanger to be tested by the size of the water tank, does not need to use a water tank, improves the detection environment, and significantly improves the efficiency of the detection link. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the principle of the air tightness detection method of the plate-fin heat exchanger in the present invention;

[0021] In the figure: 1. vacuum gauge; 2. plate-fin heat exchanger; 3. gas valve; 4. vacuum pump; 5. first nozzle; 6. second nozzle. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but it should not be understood that the scope of the subject matter described in the present invention is limited to the following embodiments. Without departing from the above-mentioned technical ideas of the present invention, various modifications, substitutions and changes made according to the common technical knowledge and customary means in the field are included in the scope of the present invention.

[0023] It should be noted that the first nozzle 5 and the second nozzle 6 described below are only used to distinguish nozzles at different positions on the plate-fin heat exchanger 2, and are not used to limit the specific positions and numbers of the nozzles. For example, the first nozzle 5 can be an inlet nozzle or an outlet nozzle, and the same applies to the second nozzle 6. When there are more than two nozzles on the plate-fin heat exchanger 2, the first nozzle 5 is any one of the nozzles, and the second nozzle 6 is any other nozzle except the first nozzle 5.

[0024] The principle of the air tightness detection method for plate-fin heat exchangers of the present invention is: the plate-fin heat exchanger 2 to be inspected is placed in the atmospheric environment, the first nozzle 5 of the plate-fin heat exchanger 2 to be inspected is connected to the vacuum pump 4, the conduction and closing of the air path between the two are controlled by the air valve 3, and the second nozzle 6 is connected to the vacuum gauge 1, thereby forming a closed inner cavity inside the plate-fin heat exchanger 2. Open the air valve 3, and use the vacuum pump 4 to draw a vacuum so that the inner cavity of the plate-fin heat exchanger 2 forms a negative pressure environment. Use the vacuum gauge 1 to observe the vacuum value of the closed inner cavity. When the vacuum reaches a predetermined first-level negative pressure value, close the air valve 3, maintain the pressure for a certain period of time, and observe the change of the negative pressure in the inner cavity of the plate-fin heat exchanger 2. If the first-level negative pressure value of the inner cavity of the plate-fin heat exchanger 2 fails to remain unchanged after a period of time, it is determined that the plate-fin heat exchanger 2 has a serious leak and the air tightness is unqualified; if the first-level negative pressure value of the inner cavity remains unchanged after a period of time, open the air valve 3 to continue to draw a vacuum in the inner cavity of the plate-fin heat exchanger 2. When the inner cavity reaches a predetermined second-level negative pressure value and can be maintained for a period of time, it is determined that the air tightness of the plate-fin heat exchanger 2 is qualified.

[0025] like Figure 1 As shown, a method for detecting negative pressure of air tightness of an aluminum alloy plate-fin heat exchanger proposed by the present invention specifically comprises the following steps:

[0026] S1: Connect the first nozzle 5 of the plate-fin heat exchanger 2 to be inspected to the vacuum pump 4 through an adapter with a sealing ring, and the opening and closing of the gas path between the first nozzle 5 and the vacuum pump 4 is controlled by the gas valve 3;

[0027] S2: Connect the second nozzle 6 of the plate-fin heat exchanger 2 to be inspected to the vacuum gauge 1 through an adapter with a sealing ring, so as to form a closed inner cavity inside the plate-fin heat exchanger 2. The detection range of the vacuum gauge 1 is 0 to 1×10 -4 Pa or 0~1×10 -5 Pa;

[0028] S3: Open the air valve 3 and use the vacuum pump 4 to evacuate the inner cavity of the plate-fin heat exchanger 2 to form a negative pressure environment in the inner cavity of the plate-fin heat exchanger 2. The preferred value of the first-level negative pressure is 1×10 -2 Pa, the preferred value of the secondary negative pressure is 1×10 -3 ~10 - 4 Pa, adjusted according to demand;

[0029] S4: reading the vacuum value of the inner cavity of the plate-fin heat exchanger 2 by using the vacuum gauge 1;

[0030] S5: When the vacuum degree of the inner cavity of the plate-fin heat exchanger 2 reaches a predetermined value of 1×10 -2 When it is below Pa, close the gas valve 3;

[0031] S6: Maintain the pressure for 5 minutes and observe the value change of the vacuum gauge 1. If the primary negative pressure value of the inner cavity of the plate-fin heat exchanger 2 cannot remain unchanged, it is determined that there is a serious leak in the plate-fin heat exchanger 2 and the air tightness test fails.

[0032] S7: If the first-level negative pressure value of the inner cavity of the plate-fin heat exchanger 2 remains unchanged, open the air valve 3 to continue to evacuate the inner cavity of the plate-fin heat exchanger 2. When the inner cavity reaches the predetermined second-level negative pressure value and can be maintained for a period of time, it is determined that the air tightness of the plate-fin heat exchanger 2 is qualified, otherwise it is unqualified.

[0033] S7: After the detection is completed, first open the air valve 3 to make the inner cavity pressure of the plate-fin heat exchanger 2 the same as the ambient pressure. When the inner cavity pressure is the same as the ambient pressure, remove the air valve 3 and the vacuum pump 4 at the first nozzle 5, and remove the vacuum gauge 1 at the second nozzle 6.

[0034] The above is the main concept of the invention. Any plate-fin heat exchanger airtightness negative pressure detection method designed according to the concept of the present invention falls within the protection scope of the present invention.

Claims

1. A method for detecting air tightness of a plate-fin heat exchanger, characterized in that: include: The plate-fin heat exchanger (2) to be inspected is placed in an atmospheric environment, and all nozzles connected to the inner cavity of the plate-fin heat exchanger (2) are blocked to form a closed inner cavity inside the plate-fin heat exchanger (2). The inner cavity of the plate-fin heat exchanger (2) is then evacuated. When the inner cavity reaches a predetermined first-level negative pressure value, the evacuation is stopped and the change in the negative pressure in the inner cavity of the plate-fin heat exchanger (2) is observed. If the first-level negative pressure value of the inner cavity fails to remain unchanged after a period of time, it is determined that the plate-fin heat exchanger (2) has a serious leak and is unqualified for air tightness. If the first-level negative pressure value of the inner cavity remains unchanged after a period of time, the inner cavity of the plate-fin heat exchanger (2) is continuously evacuated. When the inner cavity reaches a predetermined second-level negative pressure value and can be maintained for a period of time, it is determined that the air tightness of the plate-fin heat exchanger (2) is qualified.

2. A plate-fin heat exchanger air tightness detection method according to claim 1, characterized in that: The nozzle on the plate-fin heat exchanger (2) that is in communication with the inner cavity is connected to the vacuum pump (4) via an air valve (3).

3. A plate-fin heat exchanger air tightness detection method according to claim 1, characterized in that: The nozzle on the plate-fin heat exchanger (2) that is in communication with the inner cavity is connected to the vacuum gauge (1).

4. A plate-fin heat exchanger air tightness detection method according to claim 1, characterized in that: The plate-fin heat exchanger (2) is a heat exchanger made of aluminum alloy.

5. The plate-fin heat exchanger air tightness detection method according to claim 1, characterized in that: The inner cavity volume of the plate-fin heat exchanger (2) is 1 to 100 liters.

6. A plate-fin heat exchanger air tightness detection method according to claim 1, characterized in that: The first level negative pressure value is 1×10 -2 Pa.

7. The method for detecting air tightness of a plate-fin heat exchanger according to claim 1, characterized in that: The secondary negative pressure value is 1×10 -3 Pa~1×10 -4 Pa.

8. The method for detecting air tightness of a plate-fin heat exchanger according to claim 1, characterized in that: The period of time is at least 3 to 5 minutes.

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