Airplane environment control system heat exchanger leakage rate detection platform and detection method

Abstract

The invention relates to the technical field of heat exchanger detection, in particular to an aircraft environment control system heat exchanger leakage rate detection table and detection method. One end of the hot side air inlet pipe is communicated with an air source and is provided with a first laminar flow meter and a first valve, and the other end is communicated with a heat exchanger to be tested; one end of the cold side air inlet pipe is communicated with the air source and is provided with a second laminar flow meter and a second valve, and the other end is communicated with the heat exchanger to be tested; one end of the cold edge measuring tube is communicated with the heat exchanger to be tested and is provided with a third valve, and a port of the other end is provided with a first float flowmeter; one end of the hot edge measuring tube is communicated with the heat exchanger to be measured and is provided with a fourth valve, and a port of the other end is provided with a second float flowmeter. The system can accurately measure the flow of the inlet and the outlet of the hot side and the cold side of the heat exchanger, and effectively detect external leakage and blow-by. And the heat exchanger does not need to be dried for the second time after detection is finished. Not only is the complexity of manual operation reduced, but also the repeatability and reliability of the test can be improved through an automatic program.

Description

Technical Field

[0001] The present application relates to the technical field of heat exchanger detection, and in particular to a leakage detection station and detection method for a heat exchanger of an aircraft environmental control system. Background Art

[0002] A heat exchanger is a passive heat transfer device in an aircraft system, which is mainly used to transfer heat between two fluids that need to be transferred. Usually in an aircraft air conditioning system, a heat exchanger is used to exchange heat between high-temperature compressed air and low-temperature air, thereby adjusting the temperature and humidity inside the aircraft. In order to coordinate and balance the air temperature and humidity in the cabin, the air passing through the heat exchanger can be kept within a suitable temperature and humidity range. At the same time, by cooling the compressed air through the heat exchanger, a natural flow of air can also be formed in the cabin, so that the air inside and outside the cabin can be effectively circulated, further improving the air quality and ventilation effect.

[0003] In order to ensure the quality of the heat exchanger, it is necessary to conduct an air tightness test to test whether the heat exchanger has leakage problems. The water immersion method is a common detection method. The heat exchanger is immersed in water and whether bubbles appear to know whether there is leakage. An existing heat exchanger air tightness detection device includes a workbench, a water tank is installed on the upper surface of the workbench, an observation window is provided on one side of the water tank, first mounting grooves are provided on both sides of the upper surface of the workbench, a support rod is slidably installed inside each first mounting groove, a first driving mechanism for driving the support rod to move is provided on one side of the workbench, and a mounting frame is movably provided between the two support rods.

[0004] Through the observation window set on one side of the water tank, it is possible to observe in real time whether bubbles appear during the immersion of the internal workpiece, and then complete the air tightness detection of the workpiece. Through the first drive mechanism, the second drive mechanism and the clamping control mechanism, the position of the clamping plate is adjusted, and then the workpiece can be clamped and moved. However, this structure can only perform a qualitative analysis of the air tightness of the heat exchanger. At the same time, after the air tightness detection process is completed, the heat exchanger needs to be dried twice before it can be put into use, which is cumbersome. Summary of the invention

[0005] In order to solve the above problems, the present application provides a leakage detection station and detection method for a heat exchanger of an aircraft environmental control system.

[0006] The present application provides an aircraft environmental control system heat exchanger leakage detection station and detection method using the following technical solutions: In a first aspect, a leakage detection station for a heat exchanger of an aircraft environmental control system comprises: Gas source; A hot side air inlet pipe, one end of which is connected to the air source, and the other end of which is used to be connected to the hot side inlet of the heat exchanger to be tested; a first laminar flow meter and a first valve are provided on the hot side air inlet pipe; A cold side air inlet pipe, one end of which is connected to the air source, and the other end of which is used to be connected to the cold side inlet of the heat exchanger to be tested; a second laminar flow meter and a second valve are provided on the cold side air inlet pipe; a cold side measuring tube, one end of which is used to communicate with the cold side outlet of the heat exchanger to be measured, and a port at the other end of which is provided with a first float flowmeter, and a third valve is provided on the cold side measuring tube; and The hot edge measuring tube has one end connected to the hot edge outlet of the heat exchanger to be measured, and the port at the other end is provided with a second float flowmeter. The hot edge measuring tube is provided with a fourth valve.

[0007] By adopting the above technical solution, the gas source is used to introduce gas into the hot side air inlet pipe or the cold side air inlet pipe, and the flow of the hot side and cold side inlet and outlet of the heat exchanger can be accurately measured through the first laminar flow meter, the second laminar flow meter, the first float flow meter, and the second float flow meter, so as to effectively detect external leakage and blowby. After the test, there is no need to dry the heat exchanger again. The integrated design of the system not only reduces the complexity of manual operation, but also improves the repeatability and reliability of the test through automated procedures. In addition, the system has strong versatility and can be applied to the air tightness detection of heat exchangers in all fluid systems of the aircraft, reducing the safety hazards caused by leakage and ensuring the normal operation of the aircraft environmental control system and flight safety.

[0008] Optionally, it also includes a display operation panel and a processing controller, and the display operation panel, the first valve, the second valve, the third valve, the fourth valve, the first laminar flow meter, the second laminar flow meter, the first float flow meter, and the second float flow meter are all electrically connected to the processing controller.

[0009] By adopting the above technical solution and integrating the design of the display operation panel and the processing controller, the operation of the aircraft environmental control system heat exchanger leakage detection station is made more intuitive and convenient.

[0010] Optionally, it also includes a main air outlet pipe, which is a three-way pipe. The air inlet end of the main air outlet pipe is connected to the air source, and one of the other two air outlet ends of the main air outlet pipe is connected to the hot side air inlet pipe, and the other is connected to the cold side air inlet pipe.

[0011] By adopting the above technical solution, the gas source can supply gas to the hot side air inlet pipe and the cold side air inlet pipe at the same time without the need for additional pipes or interfaces, thereby reducing the complexity of the system and potential leakage points.

[0012] Optionally, a pressure regulating and shut-off valve is provided on the air inlet end of the main air outlet pipe.

[0013] By adopting the above technical solution, the gas pressure entering the heat exchanger can be accurately controlled to ensure that it is within a safe and effective working pressure range. This not only helps to maintain the efficient operation of the heat exchanger and prevent equipment damage caused by excessive pressure, but also can quickly cut off the gas source when an abnormal situation is detected to ensure the safety of the entire system.

[0014] Optionally, a one-way valve is provided on the hot side air inlet pipe, and a one-way valve is provided on the cold side air inlet pipe.

[0015] By adopting the above technical solution, one-way gas flow is ensured and backflow is prevented, thereby protecting the system from potential backflow and enhancing the reliability and safety of the system.

[0016] Optionally, the hot side air inlet pipe is provided with a pressure regulating and shut-off valve, and the cold side air inlet pipe is provided with a pressure regulating and shut-off valve.

[0017] By adopting the above technical solution, the pressure can be flexibly adjusted to meet different testing requirements, thereby enhancing the adaptability and reliability of the system.

[0018] In a second aspect, a method for detecting leakage of a heat exchanger of an aircraft environmental control system is provided, based on the above-mentioned aircraft environmental control system heat exchanger leakage detection station, comprising the following steps: Confirm that there is no leakage between the pipeline interface and the interface of the heat exchanger to be tested, close the third valve and the fourth valve, and open the first valve and the second valve; if the first laminar flow meter has a flow display value, it means that there is external leakage in the hot side channel of the heat exchanger to be tested; if the second laminar flow meter has a display value, it means that there is external leakage in the cold side channel of the heat exchanger to be tested; the sum of the flow values ​​of the first laminar flow meter and the second laminar flow meter is the external leakage of the heat exchanger to be tested; Close the second valve and the fourth valve, and open the first valve and the third valve; if the first float flowmeter has a flow display value, the flow value of the first float flowmeter is the leakage amount from the hot side to the cold side of the heat exchanger to be tested.

[0019] By adopting the above technical solution, closing certain valves and opening other valves, it is possible to accurately identify and quantify the external leakage of the hot and cold side channels of the heat exchanger, as well as the amount of leakage from the hot side to the cold side. The flow readings of the laminar flow meter and the float flow meter are used to determine the leakage amount, ensuring the accuracy of the test results. The automated control reduces the errors caused by human operation and improves the reliability of the test process.

[0020] Optionally, also include: Close the first valve and the third valve, and open the second valve and the fourth valve; If the second float flowmeter has a flow display value, the flow value of the second float flowmeter is the leakage amount from the cold side to the hot side of the heat exchanger to be tested.

[0021] By adopting the above technical solution, the amount of blowby from the cold side to the hot side of the heat exchanger to be tested can be accurately measured. The flow reading of the second float flowmeter can quantify the amount of blowby from the cold side to the hot side, which improves the comprehensiveness and accuracy of the detection, ensures the reliability of the heat exchanger in the aircraft environmental control system, and thus ensures flight safety.

[0022] In summary, the present application includes at least one of the following beneficial technical effects: 1. Use the gas source to introduce gas into the hot side air inlet pipe or the cold side air inlet pipe, and the first laminar flow meter, the second laminar flow meter, the first float flow meter, and the second float flow meter can accurately measure the flow of the hot side and cold side inlet and outlet of the heat exchanger, thereby effectively detecting external leakage and blowby. After the test, there is no need to dry the heat exchanger again.

[0023] 2. Closing specific valves and opening other valves can accurately identify and quantify the external leakage of the hot and cold side channels of the heat exchanger, as well as the amount of blowby from the hot side to the cold side and from the cold side to the hot side. The flow readings of laminar flow meters and float flow meters are used to determine the leakage and blowby, ensuring the accuracy of the test results.

[0024] 3. The integrated design of the system not only reduces the complexity of manual operation, but also improves the repeatability and reliability of the test through automated procedures. In addition, the system is highly versatile and can be applied to the air tightness detection of heat exchangers in all fluid systems of the aircraft, reducing the potential safety hazards caused by leakage and ensuring the normal operation of the aircraft environmental control system and flight safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 2 is a schematic diagram of the structure of a heat exchanger leakage detection station for an aircraft environmental control system in an embodiment of the present application; Figure 2 It is a schematic diagram of the structure of the display operation panel in the embodiment of the present application.

[0026] Description of reference numerals: 100. Heat exchanger to be tested; 1. Air source; 2. Hot side air inlet pipe; 3. Cold side air inlet pipe; 4. Cold side measuring pipe; 5. Hot side measuring pipe; 6. Main air outlet pipe; 7. Pressure regulating and shut-off valve; 8. One-way valve; F1. First laminar flow meter; F2. Second laminar flow meter; F3. First float flow meter; F4. Second float flow meter; V1. First valve; V2. Second valve; V3. Third valve; V4. Fourth valve. DETAILED DESCRIPTION

[0027] The following will be combined with the attached Figure 1-2, the technical solutions in the embodiments of the present application are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0028] The present application embodiment discloses a leakage detection station for a heat exchanger of an aircraft environmental control system. Figure 1 The aircraft environmental control system heat exchanger leakage detection station includes an air source 1, a hot side air intake pipe 2, a cold side air intake pipe 3, a cold side measuring pipe 4, a hot side measuring pipe 5, a display operation panel and a processing controller.

[0029] The gas source 1 is a cold air bottle, one end of the hot side air inlet pipe 2 is connected to the gas source 1, and the other end is used to be connected to the hot side inlet of the heat exchanger 100 to be tested; one end of the cold side air inlet pipe 3 is connected to the gas source 1, and the other end is used to be connected to the cold side inlet of the heat exchanger 100 to be tested. In this embodiment, the gas source 1 is connected to the hot side air inlet pipe 2 and the cold side air inlet pipe 3 through the main air outlet pipe 6, and the main air outlet pipe 6 is a three-way pipe. The air inlet end of the main air outlet pipe 6 is connected to the gas source 1, and one of the other two air outlet ends of the main air outlet pipe 6 is connected to the hot side air inlet pipe 2, and the other is connected to the cold side air inlet pipe 3.

[0030] A pressure regulating and shutoff valve 7 is provided on the air inlet end of the main air outlet pipe 6; a first laminar flow meter F1 and a first valve V1 are provided on the hot side air inlet pipe 2, and the first laminar flow meter F1 is used to measure the flow in the hot side air inlet pipe 2. A pressure regulating and shutoff valve 7 and a one-way valve 8 are provided on the hot side air inlet pipe 2. A second laminar flow meter F2 and a second valve V2 are provided on the cold side air inlet pipe 3, and the second laminar flow meter F2 is used to measure the flow in the cold side air inlet pipe 3. A pressure regulating and shutoff valve 7 and a one-way valve 8 are provided on the cold side air inlet pipe 3.

[0031] By providing a pressure regulating and shut-off valve 7, the gas pressure entering the heat exchanger can be accurately controlled to ensure that it is within a safe and effective working pressure range. This not only helps to maintain the efficient operation of the heat exchanger and prevent equipment damage caused by excessive pressure, but also can quickly cut off the gas source when an abnormal situation is detected to ensure the safety of the entire system.

[0032] The provision of the one-way valve 8 ensures one-way flow of gas and prevents backflow, thereby protecting the system from potential backflow and enhancing the reliability and safety of the system.

[0033] One end of the cold edge measuring tube 4 is used to communicate with the cold edge outlet of the heat exchanger 100 to be tested, and the port at the other end is provided with a first float flowmeter F3. The cold edge measuring tube 4 is provided with a third valve V3.

[0034] One end of the hot edge measuring tube 5 is used to communicate with the hot edge outlet of the heat exchanger 100 to be tested, and the port at the other end is provided with a second float flowmeter F4, and a fourth valve V4 is provided on the hot edge measuring tube 5. The first valve V1, the second valve V2, the third valve V3, and the fourth valve V4 are all electric ball valves, and in other embodiments, they can also be other electric valves.

[0035] The hot side inlet, cold side inlet, cold side outlet and hot side outlet of the heat exchanger 100 to be tested are all provided with plugging covers to ensure that there is no leakage at the connection between the heat exchanger 100 to be tested and the pipeline.

[0036] The processing controller is connected to an external power supply through a wire, and the display operation panel, the first valve V1, the second valve V2, the third valve V3, the fourth valve V4, each pressure regulating and shut-off valve 7, the first laminar flow meter F1, the second laminar flow meter F2, the first float flow meter F3, and the second float flow meter F4 are all electrically connected to the processing controller.

[0037] Reference Figure 2 The display operation panel is provided with V1 button, V2 button, V3 button and V4 button, which respectively control the opening and closing of the first valve V1, the second valve V2, the third valve V3 and the fourth valve V4. The display operation panel is provided with P1 button, P2 button and P3 button, which respectively control the opening and closing of each pressure regulating and shutoff valve. The display operation panel is provided with a flow display area, AUTO1 button and AUTO2 button.

[0038] Press the AUTO1 button, and the system automatically enters the "leakage volume" detection program. According to the preset pressure, the system automatically adjusts the output pressure of the three pressure regulating and shut-off valves through the processing controller, opens the first valve V1 and the second valve V2, and shuts off the third valve V3 and the fourth valve V4.

[0039] Press the AUTO2 button, the system automatically enters the "leakage amount" detection program, the AUTO1 button automatically pops up, the processing controller closes the second valve V2 and the fourth valve V4, and opens the first valve V1 and the third valve V3.

[0040] The display operation panel integrates multiple buttons to control the opening and closing of the valve and the flow meter reading display, while the processing controller is responsible for receiving the instructions of the operation panel and performing real-time control and data processing on the system. Through centralized control, the complexity of on-site operations is reduced, the workload of operators is reduced, and it helps to improve the safety and accuracy of the detection process.

[0041] The present application also discloses a method for detecting leakage of a heat exchanger in an aircraft environmental control system. The method is based on the above-mentioned aircraft environmental control system heat exchanger leakage detection station and comprises the following steps: Confirm that there is no leakage between the pipeline interface and the interface of the heat exchanger 100 to be tested, press the AUTO1 button, and the system automatically enters the "external leakage" detection program. The system automatically adjusts the output pressure of the three pressure regulating and shutoff valves according to the preset pressure, opens the first valve V1 and the second valve V2, and shuts off the third valve V3 and the fourth valve V4. When the system is stable, if the first laminar flow meter F1 has a flow display value, it means that the hot side channel of the heat exchanger 100 to be tested has an external leakage; if the second laminar flow meter F2 has a display value, it means that the cold side channel of the heat exchanger 100 to be tested has an external leakage; the sum of the flow values ​​of the first laminar flow meter F1 and the second laminar flow meter F2 is the external leakage of the heat exchanger 100 to be tested.

[0042] If the cold side fluid of the heat exchanger 100 to be tested is low-pressure air, the cold side structure of the heat exchanger 100 to be tested is only visually inspected, and external leakage measurement is generally not performed. If the cold side fluid of the heat exchanger 100 to be tested is liquid, such as fuel, coolant, etc., the cold side structure of the heat exchanger 100 to be tested must be inspected for external leakage.

[0043] Press the AUTO2 button, the system automatically enters the "leakage" detection program, at this time the AUTO1 button automatically pops up, the processing controller closes the second valve V2, the fourth valve V4, and opens the first valve V1, the third valve V3. When the system is stable, if the first float flowmeter F3 has a flow display value, the flow value of the first float flowmeter F3 is the leakage from the hot side to the cold side of the heat exchanger 100 to be tested (this value is the mass flow rate).

[0044] If the cold side fluid of the heat exchanger 100 to be tested is low-pressure ram air, there is no need to check the leakage from the cold side to the hot side of the heat exchanger 100 to be tested; if the cold side fluid of the heat exchanger 100 to be tested is fuel, lubricating oil, coolant and other media, a leakage test from the cold side to the hot side must be performed on the heat exchanger 100 to be tested. At this time, through the display operation panel, manually close the first valve V1 and the third valve V3, open the second valve V2 and the fourth valve V4, when the system is stable, if the second float flowmeter F4 has a flow display value, the flow value of the second float flowmeter F4 is the leakage from the cold side of the heat exchanger 100 to the hot side (this value is the mass flow rate).

[0045] The gas source 1 is used to introduce gas into the hot side air inlet pipe 2 or the cold side air inlet pipe 3, and the first laminar flow meter F1, the second laminar flow meter F2, the first float flow meter F3, and the second float flow meter F4 can accurately measure the flow of the hot side and cold side inlet and outlet of the heat exchanger, thereby effectively detecting external leakage and blowby. After the detection, there is no need to perform secondary drying on the heat exchanger.

[0046] Closing certain valves and opening other valves can accurately identify and quantify external leakage in the hot and cold side channels of the heat exchanger, as well as the amount of blowby from the hot side to the cold side and from the cold side to the hot side. The flow readings of laminar flow meters and float flow meters are used to determine the amount of leakage and blowby, ensuring the accuracy of the test results.

[0047] The integrated design of the system not only reduces the complexity of manual operation, but also improves the repeatability and reliability of the test through automated procedures. In addition, the system is highly versatile and can be applied to the air tightness detection of heat exchangers in all fluid systems of the aircraft, reducing the potential safety hazards caused by leakage and ensuring the normal operation of the aircraft environmental control system and flight safety.

[0048] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0050] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. An aircraft environmental control system heat exchanger leakage detection station, characterized in that: include: Gas source (1); A hot side air inlet pipe (2), one end of which is connected to the air source (1), and the other end of which is used to be connected to the hot side inlet of the heat exchanger (100) to be tested; a first laminar flow meter (F1) and a first valve (V1) are provided on the hot side air inlet pipe (2); A cold side air inlet pipe (3), one end of which is connected to the air source (1), and the other end of which is used to be connected to the cold side inlet of the heat exchanger (100) to be tested; a second laminar flow meter (F2) and a second valve (V2) are provided on the cold side air inlet pipe (3); a cold edge measuring tube (4), one end of which is used to communicate with the cold edge outlet of the heat exchanger (100) to be measured, and a port at the other end of which is provided with a first float flowmeter (F3); and a third valve (V3) is provided on the cold edge measuring tube (4); and A hot edge measuring tube (5) has one end connected to the hot edge outlet of the heat exchanger (100) to be measured, and a second float flowmeter (F4) is provided at the port of the other end. A fourth valve (V4) is provided on the hot edge measuring tube (5).

2. The aircraft environmental control system heat exchanger leakage detection platform according to claim 1, characterized in that: The invention also includes a display operation panel and a processing controller, wherein the display operation panel, the first valve (V1), the second valve (V2), the third valve (V3), the fourth valve (V4), the first laminar flow meter (F1), the second laminar flow meter (F2), the first float flow meter (F3), and the second float flow meter (F4) are all electrically connected to the processing controller.

3. The aircraft environmental control system heat exchanger leakage detection platform according to claim 1, characterized in that: It also includes a main air outlet pipe (6), which is a three-way pipe. The air inlet end of the main air outlet pipe (6) is connected to the air source (1), and one of the other two air outlet ends of the main air outlet pipe (6) is connected to the hot side air inlet pipe (2), and the other is connected to the cold side air inlet pipe (3).

4. The aircraft environmental control system heat exchanger leakage detection platform according to claim 3, characterized in that: A pressure regulating and shutoff valve (7) is provided on the air inlet end of the main air outlet pipe (6).

5. The aircraft environmental control system heat exchanger leakage detection platform according to claim 1, characterized in that: The hot edge air inlet pipe (2) is provided with a one-way valve (8).

6. The aircraft environmental control system heat exchanger leakage detection platform according to claim 1, characterized in that: The cold side air inlet pipe (3) is provided with a one-way valve (8).

7. The aircraft environmental control system heat exchanger leakage detection platform according to claim 1, characterized in that: The hot edge air inlet pipe (2) is provided with a pressure regulating and shutoff valve (7).

8. The aircraft environmental control system heat exchanger leakage detection platform according to claim 1, characterized in that: The cold side air inlet pipe (3) is provided with a pressure regulating and shutoff valve (7).

9. A method for detecting leakage of a heat exchanger in an aircraft environmental control system, characterized in that: The aircraft environmental control system heat exchanger leakage detection platform according to any one of claims 1 to 8 comprises the following steps: Confirm that there is no leakage between the pipeline interface and the interface of the heat exchanger (100) to be tested, close the third valve (V3) and the fourth valve (V4), and open the first valve (V1) and the second valve (V2); if the first laminar flow meter (F1) has a flow display value, it means that the hot side channel of the heat exchanger (100) to be tested has an external leakage; if the second laminar flow meter (F2) has a display value, it means that the cold side channel of the heat exchanger (100) to be tested has an external leakage; the sum of the flow values ​​of the first laminar flow meter (F1) and the second laminar flow meter (F2) is the external leakage amount of the heat exchanger (100) to be tested; The second valve (V2) and the fourth valve (V4) are closed, and the first valve (V1) and the third valve (V3) are opened; if the first float flowmeter (F3) has a flow display value, the flow value of the first float flowmeter (F3) is the leakage amount from the hot side to the cold side of the heat exchanger (100) to be tested.

10. The method for detecting leakage of a heat exchanger in an aircraft environmental control system according to claim 9, characterized in that: Also includes: The first valve (V1) and the third valve (V3) are closed, and the second valve (V2) and the fourth valve (V4) are opened; if the second float flowmeter (F4) has a flow display value, the flow value of the second float flowmeter (F4) is the leakage amount from the cold side to the hot side of the heat exchanger (100) to be tested.

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